Creativity break: how is creativity in biology changing the world?

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(logos pop)

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- I think it's really exciting

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how biology and creativity have combined,

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particularly in the area
of health and outcomes.

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And how do we help people with blindness?

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How do we help people who are paraplegic,

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where we can start to read
the electrical activity

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of their intended movement
and have a robot do that.

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So they can gain, you know,

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that activity again,

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and have that power in their lives again.

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I think that is a classic

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and beautiful example of the combination

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of biology and creativity
making our lives better

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every single day

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- Butterflies use something
called structural color

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which involves bending light
to generate color instead

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of using a bunch of pigment.

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So it definitely saves the butterflies

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a bunch of energy in making that pigment.

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But now because of some observant
and innovative scientists

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it's saving us energy too.

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It's being used in screens

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around the world to
make them more efficient

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at projecting color, which
reduces the carbon footprint

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as some of our most common electronics.

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And how about the creativity of using mRNA

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which is pretty much just
biological text messages

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to give our bodies a heads up

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that they need to recognize
dangerous viruses.

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It's the technology being used in some

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of our most innovative vaccines right now.

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(screen whooshes)

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Creativity break: what types of skills will help students innovate in biology?

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- I think it's going to
be even more important

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to have the widest range of
skillsets that you could have,

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so less specialization,
more a jack-of-all-trades,

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including design, design
thinking, design work,

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together with that programming experience,

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so that you can jump into the
new technological advances

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that are being made every day.

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We're gonna be so much
more in virtual reality,

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can you not just use it,
but can you program it?

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- I think the most important
ones will be curiosity

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and keen-eyed observational skills.

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See, curiosity fuels the question why,

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which is an essential
part of every innovation,

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and keen observational skills allow us

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not to waste our effort
reinventing the wheel.

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Life has already solved so
many of the toughest problems

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that the world can possibly throw in it,

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so why not figure out how
biology has overcome an obstacle

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and adapt or improve on that?

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Creativity break: how can students expand their creativity in biology?

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- I'd encourage every single one of you

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to spend some time immersed
in a different culture

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or maybe even spend some time working

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in a totally different part of the world

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from where you grew up.

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And...

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It doesn't have to be quite that drastic.

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It could be as simple as
investing in relationships

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with people from other parts of the world.

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And while you're at it,

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I'd encourage you to learn
a different language.

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Both of those experiences, I think,

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will stretch your mind in ways

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that help you consider
other possibilities.

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- Students can expand their creative

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and scientific skill sets

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by thinking beyond the classroom
and beyond the textbook,

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using that information

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from classroom and from the textbook

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and from other formal information sources,

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and expanding that to learn
more about both today's world

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and the world that you
imagine for the future.

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That involves using those skills

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such as communication,
and problem-solving,

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and critical thinking

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to wonder not just about
what is already known,

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but to wonder about what is not yet known,

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which involves using creativity
to think and to wonder.

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And that also means
communicating with other people

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to see how wanna shape the world as well.

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Creativity break: how does creativity play a role in your everyday life?

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- As we move forward, as
scientists, as biologists,

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the old adage is true:

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A picture is worth a thousand words.

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So what is that image,
that graph, that graphic,

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or even that imagery

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that really gets to the core of your idea.

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It almost gets to advertising.

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You want that image to stick
in your listeners' minds

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that both lets them understand

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the undeniably complex concept
that you're trying to convey

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but also makes it memorable

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and developing that skill
to come up with that picture

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that is truly worth a thousand words

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is going to be the skill
that we will all need

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going into the future.

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- Creativity plays a role in my life

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pretty much every single day
by reminding me not to stop

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just because I've reached a setback,

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like hitting a wall as
you're moving towards a goal

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doesn't have to be the end for that goal.

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To me it just means the path to success

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isn't gonna be quite as straightforward

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as I originally thought.

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Like the way around that wall

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may require me to climb
over it, or tunnel under it,

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or maybe even dig straight through it.

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But if I'm creative enough,

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I can probably find a way
to get to the other side.

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And this plays out for me in the lab

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literally every single day.

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It fuels a tenacity that
can see you through things

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like graduate school, if you
ever choose to go that route.


Creativity break: how do you get into your creative zone?

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- I allow my brain to do the work

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to get into my creative zone.

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When I have a problem to resolve,

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sometimes I just sleep on it

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and I let my subconscious mind work

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through resolving problems
and solving problems.

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Our brains are always at work

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like trying to defragment and break apart

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the things that we encounter.

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So I spend a little time thinking about

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how I can approach things creatively,

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and then I spend a little time

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not thinking about those things

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and allowing my brain
and my subconscious mind

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to have an opportunity
to do the work for me.

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A lot of times when I
come back afterwards,

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I've got a great idea,
I've got the answers,

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and I have new ways to
solve and resolve things

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that I've been thinking about.

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- To get into my creative
zone, I do something

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that I'd like to call
productive procrastination.

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I start what I'm working
on way before it's due,

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and then in fits and starts,

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I work while giving my mind
permission to wander to things

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that absolutely are not on the agenda.

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It's encouraged some of my
most creative experiences,

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some of my best songwriting,
educational videos,

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and even scientific breakthroughs

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while I was supposed to be working

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on something totally unrelated.

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This won't work for everyone,

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but my mind is most creative

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when it's free to go on
unplanned adventures.

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Good music also helps.

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A great playlist to me is
worth its weight in gold.

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My playlists are special,

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because they only include
instrumental music and songs

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in languages that I don't actually speak,

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so my thoughts don't get too pulled

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into the lyrics themselves.

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Creativity break: what are some new ways of thinking about problem solving?

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- We have the opportunity to
work together with a variety

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of different voices, colleagues
from all over the world

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who have different
strengths that they bring,

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different perspectives that they bring,

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about life, and about
how the world operates,

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and only when we bring
those voices together

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will we have a more complete picture

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about how the living world works.

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So in order to really solve
the problems of the future,

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we're going to need to work together

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as a global community.

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- Problems are not solved in isolation.

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They're solved in collaborative
groups with other people,

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and they're solved to be realistic.

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So you have to consider not
just your own discipline

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or your own science, but also
some economics, and ethics,

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and other things that
relate to the real world

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to help you reach a real
world, but sensible, solution.

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So it requires combining
all those different ways

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of thinking, being communicative
and problem solving

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and working with other people

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so that you can reach solutions

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that actually benefit the world,

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because some solutions are
gonna be great on paper,

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but in practice, they
aren't really practical.

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So that's why using new ways

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of thinking to solve
problems is really important.

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- As an example, for
me, in my PhD project,

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even though my background
has been in biology,

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the problem that really
captured my interest

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and that I wanted to pursue
involves mechanics and physics.

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And so it required learning a lot

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of some deep theories and ideas in physics

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that I wouldn't have thought of before,

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and now I kinda approach,

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it sort of changed the way

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that I approach biological problems.

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Now I have this physics lens
that I didn't have before,

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and that expands the possibilities

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of experiments I can think of,

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or hypotheses that I could
have for how something works.

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(upbeat music)


Creativity break: how have you used creative communication to solve a problem?

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- I've used creative communication
to solve problems related

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to especially people
learning different science.

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For example, in chemistry people
sometimes have a hard time

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understanding subatomic particles

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and molecules and atoms and
making those connections

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between quantities and numbers.

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So instead of jumping right into that

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which can be very difficult for people,

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I've learned to be
creative and use analogies

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or relating that to something
that is more accessible

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such as cooking or money
or building something.

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And then when people can make the relation

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between something large and familiar,

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to something small or
subatomic and unfamiliar

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it makes it easier for them
to make those connections

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and build upon that knowledge.

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So several years ago I started
making videos of myself

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explaining biology and
entomology in language

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that was accessible and
familiar to people my age

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and people who don't fit
the stereotypical model

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of a scientist.

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It's a choice that I'm really
glad that I made actually.

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I've received so much
positive feedback about videos

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no more complicated than me

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holding a bug in front of a camera.

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And actually just like this,

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me literally holding a
bug in front of a camera

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and explaining what makes a tick.

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Note to self,

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I should make a video about
what makes ticks tick.

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That'd be pretty cool.

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Wait, sorry, that's
neither here nor there.

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The point of what I'm saying is

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the choice not to excise my personality,

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the choice to bring all of my quirkiness

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into how I communicate is what
seems to make the difference.

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A big part of being creative
really can be just figuring out

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how to bring all of you

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to whatever it is that you choose to do.

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Phishing attacks

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- [Instructor] Let's say
you get an email like this,

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where it looks like it is from PayPal.

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It says "Response required" really big,

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so this is a little bit scary.

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And it says, "Dear," you,

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"We emailed you a little while
ago to ask you for your help

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"resolving an issue with
your PayPal account."

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This seems really serious.

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"Your account is still temporarily limited

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"because we haven't heard from you.

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"We noticed some unusual login
activity with your account.

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"Please check that no one
has logged into your account

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"without your permission."

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This is scary:

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To help us with this

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and to see what you can and
can't do with your account

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until the issue is resolved,

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log in to your account or
go to the Resolution Center.

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As always, if you need
help or have any questions,

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feel free to contact us.

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We're always here to help.

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Thank you for being a PayPal customer.

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Sincerely, PayPal.

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What would you do in this situation?

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Well, I think for a lot of
us, our emotional response is,

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hey, PayPal, some of my
money is involved, there.

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They're talking about other
people maybe trying to log in.

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I definitely wanna resolve this.

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And just in the heat of the moment,

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you might click on this "log in,"

00:01:07.790 --> 00:01:09.940
or you might go to the Resolution Center,

00:01:09.940 --> 00:01:14.460
and that might start you down
a little bit of a scary path.

00:01:14.460 --> 00:01:17.410
Because even though
this looks like PayPal,

00:01:17.410 --> 00:01:21.430
you really need to verify
that it really is PayPal.

00:01:21.430 --> 00:01:23.490
And there are some clues here

00:01:23.490 --> 00:01:26.060
that make it clear that it is not PayPal.

00:01:26.060 --> 00:01:27.583
See if you can find those.

00:01:29.850 --> 00:01:33.430
Well, the biggest clue is up
here on the email address.

00:01:33.430 --> 00:01:38.430
So, it says service@intl.paypal.com
as its name,

00:01:38.770 --> 00:01:40.220
but when you look at the actual

00:01:40.220 --> 00:01:41.880
email address right over here,

00:01:41.880 --> 00:01:45.240
notice it actually isn't
a PayPal email address.

00:01:45.240 --> 00:01:48.570
It says @outlook.com.

00:01:48.570 --> 00:01:52.350
So, this is a pretty good clue
that this is not from PayPal.

00:01:52.350 --> 00:01:53.940
And so, what is this?

00:01:53.940 --> 00:01:58.090
Well, this is known as a phishing attack.

00:01:58.090 --> 00:02:00.400
Why is it called a phishing attack?

00:02:00.400 --> 00:02:03.270
Well, I think it's
probably based on the idea

00:02:03.270 --> 00:02:05.610
that when you're trying to catch fish,

00:02:05.610 --> 00:02:07.290
you dangle some bait for the fish

00:02:07.290 --> 00:02:09.680
and you see which fish are going to bite.

00:02:09.680 --> 00:02:11.300
And so, this isn't exactly fishing.

00:02:11.300 --> 00:02:14.030
They spelled the "Fuh" sound P-H

00:02:14.030 --> 00:02:15.330
because what they're really doing

00:02:15.330 --> 00:02:17.630
is they're dangling some
bait in front of you

00:02:17.630 --> 00:02:20.760
and see if you're going to metaphorically

00:02:20.760 --> 00:02:22.950
get your cheek cut by the fish hook

00:02:22.950 --> 00:02:25.780
or whatever happens to fish
before they get pulled out.

00:02:25.780 --> 00:02:28.010
And how would that happen metaphorically?

00:02:28.010 --> 00:02:29.680
Well, when you click on this,

00:02:29.680 --> 00:02:34.680
it probably goes to this phishy
company or person's website.

00:02:36.280 --> 00:02:39.180
And that website might look like PayPal,

00:02:39.180 --> 00:02:42.170
but it's not going to be paypal.com.

00:02:42.170 --> 00:02:44.800
It's going to be some other web address.

00:02:44.800 --> 00:02:47.730
And so, one way to avoid
doing that beyond looking

00:02:47.730 --> 00:02:50.510
at that this is a phishy email address

00:02:50.510 --> 00:02:53.532
is that in some browsers
or in some email readers,

00:02:53.532 --> 00:02:55.010
you can scroll over this

00:02:55.010 --> 00:02:57.280
and you'll see what the website would be.

00:02:57.280 --> 00:02:58.840
Or you can right click on that.

00:02:58.840 --> 00:03:01.000
You could, say, copy the URL

00:03:01.000 --> 00:03:02.590
and you could put that in a text document

00:03:02.590 --> 00:03:04.600
to see what the actual URL is.

00:03:04.600 --> 00:03:05.870
And it's very likely

00:03:05.870 --> 00:03:08.350
that that is not going to be a PayPal URL.

00:03:08.350 --> 00:03:10.040
In fact, I would
guarantee you in this case

00:03:10.040 --> 00:03:11.360
it would not be.

00:03:11.360 --> 00:03:13.110
It would look like PayPal
when you get there,

00:03:13.110 --> 00:03:15.400
and what they'll probably
try to get you to do

00:03:15.400 --> 00:03:17.990
is type in your username and password

00:03:17.990 --> 00:03:19.850
for your PayPal account.

00:03:19.850 --> 00:03:21.420
Why is that valuable for them?

00:03:21.420 --> 00:03:24.180
Well, you just would have
then given them your username

00:03:24.180 --> 00:03:26.610
and password for your PayPal account,

00:03:26.610 --> 00:03:29.950
which then they could use
to steal money from you

00:03:29.950 --> 00:03:32.600
or to do something else to you.

00:03:32.600 --> 00:03:33.940
So, be very careful

00:03:33.940 --> 00:03:36.990
where you get these
urgent emails or texts.

00:03:36.990 --> 00:03:38.857
I got a text recently saying that,

00:03:38.857 --> 00:03:41.457
"Your Amazon account has been compromised.

00:03:41.457 --> 00:03:43.747
"Click here fast in order to make sure

00:03:43.747 --> 00:03:45.820
"that no more fraud
happens on your account."

00:03:45.820 --> 00:03:47.870
Well, it turns out that the URL,

00:03:47.870 --> 00:03:51.310
the web address there was not amazon.com.

00:03:51.310 --> 00:03:53.210
It was going to take
me to a shady website,

00:03:53.210 --> 00:03:55.680
and that shady website
looked a lot like Amazon.

00:03:55.680 --> 00:03:56.890
And so, if I acted really quickly,

00:03:56.890 --> 00:04:01.400
I would've given them my
Amazon username and password.

00:04:01.400 --> 00:04:04.510
So, be on the lookout for
these phishing attacks,

00:04:04.510 --> 00:04:07.890
and the main way to catch them
is be skeptical of anything

00:04:07.890 --> 00:04:09.250
that's talking about fraud,

00:04:09.250 --> 00:04:12.267
about something that you
would scare you and say,

00:04:12.267 --> 00:04:14.850
"Hey, do I really think
this is happening?"

00:04:14.850 --> 00:04:18.020
And then, if you really
think it might be happening,

00:04:18.020 --> 00:04:22.060
verify the email addresses,
verify the web addresses

00:04:22.060 --> 00:04:25.190
that they're really coming
from who they say they're from.

00:04:25.190 --> 00:04:29.160
And it doesn't matter if the
name is @somethingpaypal.com.

00:04:29.160 --> 00:04:31.330
You have to look at the
actual email address

00:04:31.330 --> 00:04:33.030
and it doesn't matter what it says here.

00:04:33.030 --> 00:04:35.510
It matters what the actual URL is

00:04:35.510 --> 00:04:40.010
that it clicks to to make
sure that it isn't fishy.

00:04:40.010 --> 00:04:43.033
No pun intended, or actually,
that pun was intended.


Tracking users on the Internet

WEBVTT
Kind: captions
Language: en

00:00:00.320 --> 00:00:01.490
- So there's a bunch

00:00:01.490 --> 00:00:04.130
of reasons why a website
might want to track you.

00:00:04.130 --> 00:00:05.420
And depending on your opinion,

00:00:05.420 --> 00:00:06.840
you might think some
of these are reasonable

00:00:06.840 --> 00:00:09.460
and you might think some
of them are unreasonable.

00:00:09.460 --> 00:00:10.450
Just to understand,

00:00:10.450 --> 00:00:12.730
imagine if you were to
go to say Khan Academy

00:00:12.730 --> 00:00:14.060
and you were to do some work,

00:00:14.060 --> 00:00:15.610
well it might be nice that if you were

00:00:15.610 --> 00:00:17.720
to come back another day that,

00:00:17.720 --> 00:00:19.020
that work isn't lost.

00:00:19.020 --> 00:00:20.680
And so that might be a reason

00:00:20.680 --> 00:00:23.980
why you would want Khan
Academy to know who you are.

00:00:23.980 --> 00:00:25.080
Now, there's a bunch

00:00:25.080 --> 00:00:27.200
of different ways that this could happen.

00:00:27.200 --> 00:00:28.340
The most obvious way is

00:00:28.340 --> 00:00:30.840
by having an account with
a username and a password.

00:00:30.840 --> 00:00:32.980
So when you type in your
username and password

00:00:32.980 --> 00:00:34.820
the site knows exactly who you are.

00:00:34.820 --> 00:00:36.820
It can retrieve your data from a database

00:00:36.820 --> 00:00:39.490
and then you can pick up
right where you left off.

00:00:39.490 --> 00:00:41.300
That's probably the
most obvious to people.

00:00:41.300 --> 00:00:44.410
And it's also the most
obvious how to not be tracked

00:00:44.410 --> 00:00:46.410
in that way is that you log out.

00:00:46.410 --> 00:00:48.260
But just because you logged out or just

00:00:48.260 --> 00:00:50.940
because you don't have a username
and password doesn't mean

00:00:50.940 --> 00:00:53.330
that you can't be tracked by a site.

00:00:53.330 --> 00:00:55.400
There's several other
ways that can be tracked

00:00:55.400 --> 00:00:56.780
that you should know about

00:00:56.780 --> 00:00:59.910
and also know how to
undo them if possible.

00:00:59.910 --> 00:01:03.080
Another way is leveraging
something called cookies.

00:01:03.080 --> 00:01:06.200
Cookies, even if you don't
have an account on a site,

00:01:06.200 --> 00:01:09.490
most web browsers are
going to allow the website

00:01:09.490 --> 00:01:12.810
to place a little bit of
text on your computer.

00:01:12.810 --> 00:01:14.360
So the browser, which is running

00:01:14.360 --> 00:01:16.260
on your computer is gonna place it,

00:01:16.260 --> 00:01:17.760
so that next time your browser goes

00:01:17.760 --> 00:01:19.480
to that site again, the site will say,

00:01:19.480 --> 00:01:22.130
oh this is the same person
whose cookie I put there.

00:01:22.130 --> 00:01:24.060
And then there might that
cookie might have a little bit

00:01:24.060 --> 00:01:26.430
of data associated with it and say, okay

00:01:26.430 --> 00:01:28.461
there could be some useful things.

00:01:28.461 --> 00:01:29.294
We can pick up where we left off.

00:01:29.294 --> 00:01:31.120
We can customize for what
you were looking for.

00:01:31.120 --> 00:01:32.840
Or you might say that's
a little bit creepy,

00:01:32.840 --> 00:01:34.570
that a site that I
didn't get permission to

00:01:34.570 --> 00:01:35.880
is able to keep track of me.

00:01:35.880 --> 00:01:38.470
And so you might want
to delete your cookies

00:01:38.470 --> 00:01:41.210
which your browser will allow you to do.

00:01:41.210 --> 00:01:44.410
Now cookies, as I saId,
they have their benefits.

00:01:44.410 --> 00:01:45.243
This one of the reasons

00:01:45.243 --> 00:01:47.520
why you can often stay logged

00:01:47.520 --> 00:01:50.120
into a website because the website says,

00:01:50.120 --> 00:01:50.953
oh, this is a cookie.

00:01:50.953 --> 00:01:53.830
This is the person who keeps logging in.

00:01:53.830 --> 00:01:55.490
You might want the personalization

00:01:55.490 --> 00:01:56.820
of the advertisements

00:01:56.820 --> 00:01:59.280
or any other customizations
without logging in.

00:01:59.280 --> 00:02:01.040
And that's where a cookie could be useful.

00:02:01.040 --> 00:02:03.710
But if you don't want it, of
course, you can delete it.

00:02:03.710 --> 00:02:05.530
Now, another way that a
website can keep track

00:02:05.530 --> 00:02:06.840
is your IP address.

00:02:06.840 --> 00:02:08.490
When your web browser

00:02:08.490 --> 00:02:11.090
which is running on your
computer or on your phone

00:02:12.100 --> 00:02:13.540
wants to look at a website,

00:02:13.540 --> 00:02:15.100
it sends a request to that website,

00:02:15.100 --> 00:02:16.970
and then that request sends the data,

00:02:16.970 --> 00:02:18.400
sends the website back.

00:02:18.400 --> 00:02:20.400
And so in order to send the data back

00:02:20.400 --> 00:02:23.170
it needs an address for your
phone or for your computer

00:02:23.170 --> 00:02:26.340
and that's going to be in
the form of an IP address.

00:02:26.340 --> 00:02:29.610
Now you can imagine if that
site knows your IP address

00:02:29.610 --> 00:02:31.350
and then if you were to
come from the same device

00:02:31.350 --> 00:02:33.270
with the same IP address,
again, it'll say, okay,

00:02:33.270 --> 00:02:34.820
it's at least the same device.

00:02:34.820 --> 00:02:36.220
Maybe it's the same person.

00:02:36.220 --> 00:02:38.810
And then they might be able
to track you in that way.

00:02:38.810 --> 00:02:39.870
Once again, it might be

00:02:39.870 --> 00:02:42.030
for some good uses, like customization

00:02:42.030 --> 00:02:45.580
or maybe it's things that you
aren't so comfortable with.

00:02:45.580 --> 00:02:48.020
Now, what gets extra interesting

00:02:48.020 --> 00:02:50.380
and might be useful or not useful,

00:02:50.380 --> 00:02:53.140
depending on your point
of view is that it's not

00:02:53.140 --> 00:02:56.100
necessarily just your
relationship with one website.

00:02:56.100 --> 00:02:59.380
For example, you might have an
advertiser that puts cookies

00:02:59.380 --> 00:03:02.280
on a bunch of websites,
and so can keep track

00:03:02.280 --> 00:03:04.740
of you as you go from site to site.

00:03:04.740 --> 00:03:07.520
And so then it's getting, at least for me,

00:03:07.520 --> 00:03:10.320
I don't like the fact that people can see

00:03:10.320 --> 00:03:12.800
how I'm moving around on the internet.

00:03:12.800 --> 00:03:15.230
Or I remember recently I was looking

00:03:15.230 --> 00:03:19.440
for a mountain bike and I
did it on one eCommerce site.

00:03:19.440 --> 00:03:20.350
And then all of a sudden it seemed

00:03:20.350 --> 00:03:21.450
like the whole internet knew

00:03:21.450 --> 00:03:22.790
that I wanted to buy a mountain bike.

00:03:22.790 --> 00:03:24.220
I didn't end up buying a mountain bike.

00:03:24.220 --> 00:03:25.362
Now some of you might say, that's nice.

00:03:25.362 --> 00:03:27.670
You know, the internet knows
I want a mountain bike.

00:03:27.670 --> 00:03:29.570
I'd like to keep being presented

00:03:29.570 --> 00:03:31.230
with ads on mountain bikes.

00:03:31.230 --> 00:03:32.670
Some of you might say,
hey, that's not so cool.

00:03:32.670 --> 00:03:34.530
It was just, well, you
know, a random search I did.

00:03:34.530 --> 00:03:35.363
And it's kind of weird

00:03:35.363 --> 00:03:37.250
that the internet is starting
to build this profile of me

00:03:37.250 --> 00:03:40.110
of someone who might be in
the market for mountain bikes.

00:03:40.110 --> 00:03:43.880
And so once again, deleting
your cookies can go a long way

00:03:43.880 --> 00:03:45.020
to preventing that type of thing,

00:03:45.020 --> 00:03:46.620
if you're uncomfortable with it.

00:03:46.620 --> 00:03:49.430
And then IP addresses, that's
a little bit harder to hide.

00:03:49.430 --> 00:03:51.710
Sometimes you have dynamic IP addresses

00:03:51.710 --> 00:03:55.190
sometimes it changes, but the clearest way

00:03:55.190 --> 00:03:57.060
of protecting your IP address is

00:03:57.060 --> 00:03:58.950
if you use something like
a virtual private network

00:03:58.950 --> 00:04:02.450
which does get a little bit more complex.

00:04:02.450 --> 00:04:03.640
Now related to all of this,

00:04:03.640 --> 00:04:05.100
some of you also might be thinking

00:04:05.100 --> 00:04:06.890
about being tracked when you do a search.

00:04:06.890 --> 00:04:07.980
You might see that,

00:04:07.980 --> 00:04:10.170
hey, these suggested searches

00:04:10.170 --> 00:04:11.710
that the site is giving,

00:04:11.710 --> 00:04:14.010
it seems like it's kind of specific to me.

00:04:14.010 --> 00:04:16.080
And that's because in many cases it is.

00:04:16.080 --> 00:04:17.890
The search engine probably

00:04:17.890 --> 00:04:21.350
has placed cookies, or it's
keeping with an IP address

00:04:21.350 --> 00:04:23.900
of things that you have
searched for before.

00:04:23.900 --> 00:04:25.940
And the things that you have clicked on.

00:04:25.940 --> 00:04:27.410
And so it could use that maybe

00:04:27.410 --> 00:04:28.990
to give you different search results,

00:04:28.990 --> 00:04:31.430
maybe to change what the auto-complete is.

00:04:31.430 --> 00:04:34.450
It also might be keeping
track of a search history.

00:04:34.450 --> 00:04:36.270
So the search history could be useful,

00:04:36.270 --> 00:04:37.150
if you wanna look

00:04:37.150 --> 00:04:39.340
at other sites that
you have been to before

00:04:39.340 --> 00:04:40.910
or you might not want that around.

00:04:40.910 --> 00:04:45.190
You might not want the
site or someone else

00:04:45.190 --> 00:04:47.500
who if you just happen
to be using your computer

00:04:47.500 --> 00:04:49.130
to see what you've been searching for.

00:04:49.130 --> 00:04:51.410
So most browsers, sorry

00:04:51.410 --> 00:04:54.650
most search engines are
going to let you delete that.

00:04:54.650 --> 00:04:56.403
So there's a lot more to it.

00:04:56.403 --> 00:04:59.540
This is just kind of
the tip of the iceberg,

00:04:59.540 --> 00:05:02.150
but think about how you
may or may not be tracked

00:05:02.150 --> 00:05:04.600
and think about how you may
or may not want to be tracked.

00:05:04.600 --> 00:05:06.140
And good hygiene is,

00:05:06.140 --> 00:05:08.770
especially if you're at a public
computer log out of things.

00:05:08.770 --> 00:05:11.720
That's also so other people
can't use use your account,

00:05:11.720 --> 00:05:12.730
really be thoughtful about

00:05:12.730 --> 00:05:15.000
whether you even want to
create an account for a site.

00:05:15.000 --> 00:05:16.820
Is this something that you really need?

00:05:16.820 --> 00:05:18.560
What are going to be the benefits for you?

00:05:18.560 --> 00:05:20.970
Think about whether you
want to accept cookies?

00:05:20.970 --> 00:05:23.810
I would recommend deleting
cookies pretty regularly.

00:05:23.810 --> 00:05:24.840
It might have some negatives.

00:05:24.840 --> 00:05:26.470
You might have to re-log into a few sites,

00:05:26.470 --> 00:05:28.550
but there's probably a
lot of other shady sites

00:05:28.550 --> 00:05:31.740
that no longer can
track what you're doing.

00:05:31.740 --> 00:05:33.720
But even if you do all of those things

00:05:33.720 --> 00:05:36.513
still be very careful
and very conscientious.


Importance of Data Security

WEBVTT
Kind: captions
Language: en

00:00:01.370 --> 00:00:03.610
- I'm going to make a bold prediction.

00:00:03.610 --> 00:00:07.350
You probably don't like
people stealing your identity

00:00:07.350 --> 00:00:09.840
which allows them to steal your money.

00:00:09.840 --> 00:00:12.620
Or maybe tell the whole
universe what you're up to

00:00:12.620 --> 00:00:14.800
and being able to track
you and your family,

00:00:14.800 --> 00:00:16.800
and compromise your security.

00:00:16.800 --> 00:00:18.950
These don't feel like good things.

00:00:18.950 --> 00:00:21.780
And so, if that is true
of you, it's true of me.

00:00:21.780 --> 00:00:23.330
I don't like any of those things.

00:00:23.330 --> 00:00:26.540
I wanna keep my private
information private,

00:00:26.540 --> 00:00:29.460
then you should care about data security.

00:00:29.460 --> 00:00:32.020
And that's what we're
going to do in this unit.

00:00:32.020 --> 00:00:32.910
You're gonna learn a lot

00:00:32.910 --> 00:00:35.470
about personally identifiable information.

00:00:35.470 --> 00:00:36.910
Your name is one example,

00:00:36.910 --> 00:00:39.070
but also things like your
social security number,

00:00:39.070 --> 00:00:42.050
or things that are indirectly,
personally identifiable

00:00:42.050 --> 00:00:44.630
like your address, or your phone number,

00:00:44.630 --> 00:00:46.420
why that's important.

00:00:46.420 --> 00:00:47.960
And then we're going to learn the ways

00:00:47.960 --> 00:00:50.100
that people are going to
try to get ahold of it,

00:00:50.100 --> 00:00:51.670
and why they want to get ahold of it.

00:00:51.670 --> 00:00:54.430
Because they might wanna misrepresent you,

00:00:54.430 --> 00:00:57.180
or or publish things
about you on the Internet,

00:00:57.180 --> 00:00:59.030
or control your presence on the internet,

00:00:59.030 --> 00:01:03.430
or steal money from you or from
others that you care about.

00:01:03.430 --> 00:01:04.330
And then we're going to learn

00:01:04.330 --> 00:01:05.760
about ways to protect from those.

00:01:05.760 --> 00:01:08.110
A lot of that's going to be
behavior change on your part

00:01:08.110 --> 00:01:09.890
to be a little bit more vigilant,

00:01:09.890 --> 00:01:13.360
but also technology ways of
keeping your data secret,

00:01:13.360 --> 00:01:15.650
encrypting your data, authentication,

00:01:15.650 --> 00:01:18.530
making sure that the person
who says they are who they are,

00:01:18.530 --> 00:01:20.530
are actually them.

00:01:20.530 --> 00:01:23.180
So enjoy this unit on data security.

00:01:23.180 --> 00:01:25.620
It isn't just interesting, which it is.

00:01:25.620 --> 00:01:28.400
It could save you a lot of money,

00:01:28.400 --> 00:01:31.023
a lot of pain, and a lot of embarrassment.


Personally Identifiable Information (PII)

WEBVTT
Kind: captions
Language: en

00:00:00.573 --> 00:00:01.710
- Hi everyone.

00:00:01.710 --> 00:00:03.360
Sal Khan here from Khan academy.

00:00:03.360 --> 00:00:06.250
My Social Security Number is 857,

00:00:06.250 --> 00:00:07.180
- 32

00:00:07.180 --> 00:00:08.133
- 5567.

00:00:10.600 --> 00:00:11.433
No, it's not.

00:00:11.433 --> 00:00:14.320
I wouldn't tell you my Social
Security Number like that.

00:00:14.320 --> 00:00:15.153
And that's because

00:00:15.153 --> 00:00:20.153
it is personally identifiable
information, or PII.

00:00:20.360 --> 00:00:22.630
And there's a reason why
you want to keep that

00:00:22.630 --> 00:00:26.493
to yourself, or at least
limit who has access to PII.

00:00:27.630 --> 00:00:31.950
Because if someone has access,
they can expose your privacy,

00:00:31.950 --> 00:00:34.290
tell the world where you
live, they could track you

00:00:34.290 --> 00:00:36.310
and they could tell the
world what you've been up to,

00:00:36.310 --> 00:00:37.560
maybe when you should be working

00:00:37.560 --> 00:00:38.740
what websites you're visiting,

00:00:38.740 --> 00:00:43.380
or, even worse, potentially,
they could steal your identity,

00:00:43.380 --> 00:00:44.790
take money out of your bank account,

00:00:44.790 --> 00:00:46.410
take a credit card in your name,

00:00:46.410 --> 00:00:48.493
do some other form of identity theft

00:00:48.493 --> 00:00:52.890
that could be embarrassing,
or super costly.

00:00:52.890 --> 00:00:55.340
So, if you have some type of a service,

00:00:55.340 --> 00:00:57.850
either online or otherwise,
that's asking for something

00:00:57.850 --> 00:00:59.650
like your Social Security Number,

00:00:59.650 --> 00:01:02.840
or your birthday, which might
be a little bit more indirect,

00:01:02.840 --> 00:01:05.603
or your email address,
or your phone number,

00:01:05.603 --> 00:01:07.430
you might ask why.

00:01:07.430 --> 00:01:09.230
Sometimes there's a legitimate reason

00:01:09.230 --> 00:01:10.197
why they need to know these things

00:01:10.197 --> 00:01:13.570
but many times, I'd argue
even most of the time,

00:01:13.570 --> 00:01:15.350
there might not be a legitimate reason.

00:01:15.350 --> 00:01:16.900
And so you need to ask yourself, well

00:01:16.900 --> 00:01:18.075
what are they going to do with it?

00:01:18.075 --> 00:01:21.220
And if you don't feel comfortable
giving that information,

00:01:21.220 --> 00:01:23.960
ask yourself, do you
really need that service?

00:01:23.960 --> 00:01:26.200
So think seriously about your PII.

00:01:26.200 --> 00:01:28.640
Unfortunately, bad actors
on the Internet are coming

00:01:28.640 --> 00:01:32.630
up with new ways of
leveraging both direct PII,

00:01:32.630 --> 00:01:34.300
personally identifiable information

00:01:34.300 --> 00:01:35.700
like Social Security Numbers,

00:01:35.700 --> 00:01:38.360
even biometrics, even your name,

00:01:38.360 --> 00:01:41.760
and indirect measures, or
indirect pieces of PII,

00:01:41.760 --> 00:01:46.430
like your birthday, or your
address, or your email address,

00:01:46.430 --> 00:01:48.640
or your phone number,
that can be put together

00:01:48.640 --> 00:01:51.070
to do shady things with your identity.

00:01:51.070 --> 00:01:53.333
So be very careful.


Lunar eclipses

WEBVTT
Kind: captions
Language: en

00:00:00.120 --> 00:00:01.720
- [Narrator] Have you
ever seen the full moon

00:00:01.720 --> 00:00:03.490
appear to change from this,

00:00:03.490 --> 00:00:05.490
to this, to this

00:00:05.490 --> 00:00:07.570
all in a couple hours?

00:00:07.570 --> 00:00:10.070
If so, you've witnessed a lunar eclipse.

00:00:10.070 --> 00:00:12.100
The word eclipse comes from a Greek word

00:00:12.100 --> 00:00:13.170
meaning "to leave."

00:00:13.170 --> 00:00:14.850
For centuries, people have marveled

00:00:14.850 --> 00:00:16.340
at how the full moon appears to leave

00:00:16.340 --> 00:00:17.820
during a lunar eclipse.

00:00:17.820 --> 00:00:19.770
The Incas believed that
lunar eclipses happened

00:00:19.770 --> 00:00:21.820
when a giant jaguar ate the full moon.

00:00:21.820 --> 00:00:23.790
It turns out, lunar eclipses happen

00:00:23.790 --> 00:00:26.130
when the moon is covered
by Earth's shadow.

00:00:26.130 --> 00:00:27.220
We can only see the moon

00:00:27.220 --> 00:00:28.960
because it reflects light from the sun.

00:00:28.960 --> 00:00:31.360
The moon doesn't generate
any light of its own.

00:00:31.360 --> 00:00:33.730
The sun lights up half of
the sphere of the moon.

00:00:33.730 --> 00:00:35.780
When Earth is between
the sun and the moon,

00:00:35.780 --> 00:00:38.260
we can see the entire
lit part of the moon.

00:00:38.260 --> 00:00:40.540
We call this the full moon.

00:00:40.540 --> 00:00:42.200
But sometimes during a full moon,

00:00:42.200 --> 00:00:44.620
Earth, the moon, and the sun all line up

00:00:44.620 --> 00:00:46.950
in such a way that Earth
casts a shadow onto the moon.

00:00:46.950 --> 00:00:49.460
This creates a lunar eclipse.

00:00:49.460 --> 00:00:50.670
Lunar eclipses can be seen

00:00:50.670 --> 00:00:52.520
from anywhere on the night side of Earth.

00:00:52.520 --> 00:00:54.720
The two most dramatic
types of lunar eclipses

00:00:54.720 --> 00:00:56.120
are total and partial.

00:00:56.120 --> 00:00:57.522
During a total lunar eclipse,

00:00:57.522 --> 00:01:00.100
Earth's shadow completely covers the moon.

00:01:00.100 --> 00:01:02.640
This means that no direct
sunlight is reaching the moon.

00:01:02.640 --> 00:01:05.780
However, the moon is still
visible during the eclipse.

00:01:05.780 --> 00:01:06.780
Why is this?

00:01:06.780 --> 00:01:08.820
As sunlight passes through our atmosphere,

00:01:08.820 --> 00:01:10.610
some of it gets bent slightly

00:01:10.610 --> 00:01:11.820
allowing it to reach the moon

00:01:11.820 --> 00:01:13.750
as indirect sunlight.

00:01:13.750 --> 00:01:16.180
Most of the light that
gets bent is red or orange,

00:01:16.180 --> 00:01:18.120
meaning that the moon
appears reddish orange

00:01:18.120 --> 00:01:19.480
during the eclipse.

00:01:19.480 --> 00:01:21.010
During a partial lunar eclipse,

00:01:21.010 --> 00:01:23.540
Earth's shadow only
partially covers the moon.

00:01:23.540 --> 00:01:26.420
So some direct sunlight is
still reaching the moon.

00:01:26.420 --> 00:01:28.850
Lunar eclipses only
happen during a full moon

00:01:28.850 --> 00:01:30.840
since it's the only
time in the moon's orbit

00:01:30.840 --> 00:01:32.950
where Earth is between
the sun and the moon.

00:01:32.950 --> 00:01:35.570
And you might be wondering,
"why isn't there a lunar eclipse

00:01:35.570 --> 00:01:37.010
during every full moon?"

00:01:37.010 --> 00:01:39.070
Well, the moon's orbit around Earth

00:01:39.070 --> 00:01:41.480
is tilted relative to
Earth's orbit around the sun.

00:01:41.480 --> 00:01:42.420
This means that the moon

00:01:42.420 --> 00:01:45.600
often passes just above or
just below Earth's shadow.

00:01:45.600 --> 00:01:47.600
Partial lunar eclipses
happen when the sun,

00:01:47.600 --> 00:01:50.730
the moon, and Earth almost,
but not quite exactly,

00:01:50.730 --> 00:01:53.360
line up so that the moon
is only partially covered

00:01:53.360 --> 00:01:54.450
by Earth's shadow.

00:01:54.450 --> 00:01:56.880
Total lunar eclipses
happen only when the sun,

00:01:56.880 --> 00:01:59.540
the moon, and Earth all line up precisely.

00:01:59.540 --> 00:02:01.900
So if you ever get to see a lunar eclipse,

00:02:01.900 --> 00:02:04.510
you can thank our planet for
blocking the moon's sunlight

00:02:04.510 --> 00:02:06.760
and letting us enjoy
the celestial spectacle.


Cellular respiration

WEBVTT
Kind: captions
Language: en

00:00:00.250 --> 00:00:01.770
- [Instructor] So let's
say I was preparing

00:00:01.770 --> 00:00:03.890
to go on a long hike.

00:00:03.890 --> 00:00:06.720
Besides packing water,
dressing for the weather

00:00:06.720 --> 00:00:08.060
and mapping my route,

00:00:08.060 --> 00:00:10.520
I'd probably also want to eat a snack

00:00:10.520 --> 00:00:13.450
before leaving to make
sure I have enough energy

00:00:13.450 --> 00:00:14.550
for the hike.

00:00:14.550 --> 00:00:17.710
We as humans need food
to nourish our bodies.

00:00:17.710 --> 00:00:20.880
But how exactly does
that food give us energy?

00:00:20.880 --> 00:00:24.280
How does something like an
apple or a piece of chocolate

00:00:24.280 --> 00:00:27.630
get converted into something
our bodies can use?

00:00:27.630 --> 00:00:29.770
The answer to this question can be found

00:00:29.770 --> 00:00:32.630
in a process called cellular respiration.

00:00:32.630 --> 00:00:35.920
Which is how organisms get
their energy from food.

00:00:35.920 --> 00:00:36.930
In other words,

00:00:36.930 --> 00:00:40.120
cellular respiration
helps make life possible.

00:00:40.120 --> 00:00:42.250
It's happening right now in your cells

00:00:42.250 --> 00:00:43.290
and in mine,

00:00:43.290 --> 00:00:45.860
in my little brothers pet hamster cells

00:00:45.860 --> 00:00:48.760
and in the cells of the
tree outside the window.

00:00:48.760 --> 00:00:50.900
It's providing all of us with the energy

00:00:50.900 --> 00:00:52.560
that we need to function.

00:00:52.560 --> 00:00:54.510
So let's dive into this process

00:00:54.510 --> 00:00:57.090
to find out more about how it works.

00:00:57.090 --> 00:01:00.700
Cellular respiration is a
series of chemical reactions

00:01:00.700 --> 00:01:04.110
that happen in an organized
way inside our cells.

00:01:04.110 --> 00:01:06.310
It's these chemical reactions that result

00:01:06.310 --> 00:01:10.400
in an overall release of
energy that our bodies can use.

00:01:10.400 --> 00:01:11.740
Although cellular respiration

00:01:11.740 --> 00:01:15.240
involves many chemical
reactions, this entire process

00:01:15.240 --> 00:01:17.740
for plants and animals
can be summarized here

00:01:17.740 --> 00:01:19.380
by this equation.

00:01:19.380 --> 00:01:22.520
On the left side of this
equation are the inputs;

00:01:22.520 --> 00:01:25.060
Glucose, which is a type of sugar,

00:01:25.060 --> 00:01:26.500
and oxygen.

00:01:26.500 --> 00:01:29.630
Glucose comes from our
food and oxygen comes

00:01:29.630 --> 00:01:31.690
from the air we breathe.

00:01:31.690 --> 00:01:34.310
The right side of this
equation shows the outputs,

00:01:34.310 --> 00:01:36.700
carbon dioxide and water.

00:01:36.700 --> 00:01:39.220
The air in the middle shows
that during the process

00:01:39.220 --> 00:01:40.830
of cellular respiration,

00:01:40.830 --> 00:01:43.850
glucose and oxygen molecules
are are broken apart

00:01:43.850 --> 00:01:46.060
and their atoms are rearranged

00:01:46.060 --> 00:01:49.130
to eventually form
carbon dioxide and water.

00:01:49.130 --> 00:01:51.430
This whole process releases energy,

00:01:51.430 --> 00:01:55.020
similar to how firewood
releases energy as it burns.

00:01:55.020 --> 00:01:59.010
Also, no atoms are lost
during cellular respiration.

00:01:59.010 --> 00:02:01.700
You can see the same
number of each type of atom

00:02:01.700 --> 00:02:04.320
on both sides of the arrow, for example,

00:02:04.320 --> 00:02:06.720
six carbon atoms on both sides.

00:02:06.720 --> 00:02:10.030
It's similar to how you could
take apart a brick house

00:02:10.030 --> 00:02:13.650
and use those bricks to build
something else, like a bridge.

00:02:13.650 --> 00:02:15.710
You're not throwing
away any of the bricks,

00:02:15.710 --> 00:02:18.790
but instead you're creating
something new out of them.

00:02:18.790 --> 00:02:22.100
So we know that cellular
respiration involves a series

00:02:22.100 --> 00:02:23.650
of chemical reactions,

00:02:23.650 --> 00:02:26.720
but where in the cell
do these steps happen?

00:02:26.720 --> 00:02:29.580
To find out, let's walk
through the process together.

00:02:29.580 --> 00:02:32.010
After eating, your food is broken down

00:02:32.010 --> 00:02:34.870
into small molecules during digestion.

00:02:34.870 --> 00:02:37.670
These small molecules
which include glucose

00:02:37.670 --> 00:02:39.520
can enter your cells.

00:02:39.520 --> 00:02:41.950
Then cellular respiration can begin.

00:02:41.950 --> 00:02:45.120
The first set of chemical
reactions happen in the cytosol,

00:02:45.120 --> 00:02:47.860
which is the jelly-like
fluid containing all

00:02:47.860 --> 00:02:49.110
of the cells organelles,

00:02:49.110 --> 00:02:51.840
and they involve glucose as an input.

00:02:51.840 --> 00:02:54.860
The rest of the reactions
happen in mitochondria,

00:02:54.860 --> 00:02:58.380
with oxygen as an input and carbon dioxide

00:02:58.380 --> 00:03:00.380
and water as outputs.

00:03:00.380 --> 00:03:02.710
Together, these chemical reactions result

00:03:02.710 --> 00:03:05.600
in an overall release of energy.

00:03:05.600 --> 00:03:07.150
It might be a little mind boggling

00:03:07.150 --> 00:03:09.680
for you to think about how
the food we eat provides

00:03:09.680 --> 00:03:11.130
the energy our bodies need

00:03:11.130 --> 00:03:13.630
to carry out all of lives processes.

00:03:13.630 --> 00:03:15.460
And I know it was for me.

00:03:15.460 --> 00:03:18.740
After all, it's not every day
you take a bite of an apple

00:03:18.740 --> 00:03:20.860
and wonder how that apple's molecules

00:03:20.860 --> 00:03:23.270
are rearranged inside your body.

00:03:23.270 --> 00:03:24.680
What's important to know though,

00:03:24.680 --> 00:03:26.270
is that cellular respiration

00:03:26.270 --> 00:03:29.410
is the way our cells get usable energy.

00:03:29.410 --> 00:03:30.930
Through cellular respiration,

00:03:30.930 --> 00:03:32.880
you and I get the energy that we need

00:03:32.880 --> 00:03:34.670
to do the things we want to do,

00:03:34.670 --> 00:03:37.260
including accomplishing our goals.

00:03:37.260 --> 00:03:39.430
So, the next time you feel
proud of your yourself

00:03:39.430 --> 00:03:43.090
for finishing a big hike
or acing your biology quiz,

00:03:43.090 --> 00:03:45.883
make sure to thank your mitochondria.


Food and energy in organisms

WEBVTT
Kind: captions
Language: en

00:00:00.140 --> 00:00:02.220
- [Instructor] Hey,
quick question for you.

00:00:02.220 --> 00:00:04.670
You ever look at a person's baby pictures

00:00:04.670 --> 00:00:08.300
and wonder how people go from
being small to, well, big?

00:00:08.300 --> 00:00:10.040
I mean, yes, I get it.

00:00:10.040 --> 00:00:12.450
People grow up, but
here, I'm thinking more

00:00:12.450 --> 00:00:14.540
on the level of the atoms and molecules

00:00:14.540 --> 00:00:15.640
that make up the body

00:00:15.640 --> 00:00:19.090
because A, I'm a scientist
and that's kind of what we do,

00:00:19.090 --> 00:00:21.560
and then also B, because after all,

00:00:21.560 --> 00:00:23.650
all the changes we see
on these larger scales

00:00:23.650 --> 00:00:26.410
are just reflections of
very many changes occurring

00:00:26.410 --> 00:00:28.360
on the molecular scale.

00:00:28.360 --> 00:00:30.790
And so if you think about it that way,

00:00:30.790 --> 00:00:33.040
then it's likely reasonable to assume

00:00:33.040 --> 00:00:35.230
that because the adult's body is bigger,

00:00:35.230 --> 00:00:38.020
it has more molecules
and/or larger molecules

00:00:38.020 --> 00:00:39.200
than the baby's body.

00:00:39.200 --> 00:00:42.960
And so this means that there
are some molecules in this baby

00:00:42.960 --> 00:00:46.200
and those molecules are
interacting and combining

00:00:46.200 --> 00:00:48.890
with some other source
of molecules in the world

00:00:48.890 --> 00:00:50.920
in order to become this adult.

00:00:50.920 --> 00:00:52.210
And generally speaking,

00:00:52.210 --> 00:00:55.200
the source of those molecules
is going to be our diet,

00:00:55.200 --> 00:00:56.660
AKA our food.

00:00:56.660 --> 00:00:58.540
And to kind of understand this,

00:00:58.540 --> 00:01:00.690
we can actually make a comparison here

00:01:00.690 --> 00:01:03.360
between food and wood.

00:01:03.360 --> 00:01:05.330
So what I mean by that

00:01:05.330 --> 00:01:06.760
is that the molecules in food

00:01:06.760 --> 00:01:09.250
interact with the molecules on our bodies

00:01:09.250 --> 00:01:11.160
in two primary ways.

00:01:11.160 --> 00:01:14.720
The first is as a source of
molecular building blocks,

00:01:14.720 --> 00:01:15.553
or in other words,

00:01:15.553 --> 00:01:18.690
molecules the body can use
to build new structures.

00:01:18.690 --> 00:01:20.240
And the second is going to be

00:01:20.240 --> 00:01:22.360
as a source of molecules for fuel,

00:01:22.360 --> 00:01:26.560
much like a campfire or
firewood, like what we have here.

00:01:26.560 --> 00:01:27.990
But in order to understand

00:01:27.990 --> 00:01:30.000
how and why this can happen,

00:01:30.000 --> 00:01:33.820
we need to briefly discuss
the molecular basis of food.

00:01:33.820 --> 00:01:35.530
So what are the molecules in food?

00:01:35.530 --> 00:01:36.670
Let me introduce you.

00:01:36.670 --> 00:01:38.090
All right, 'cause generally speaking,

00:01:38.090 --> 00:01:41.520
food is made up of these
three classes of molecules.

00:01:41.520 --> 00:01:43.750
First up are fats,

00:01:43.750 --> 00:01:45.550
then we've got sugars,

00:01:45.550 --> 00:01:48.230
and finally some protein.

00:01:48.230 --> 00:01:51.490
I'd imagine some of these
sound reasonably familiar.

00:01:51.490 --> 00:01:53.760
These molecules are made basically

00:01:53.760 --> 00:01:55.440
from just a few elements.

00:01:55.440 --> 00:01:59.300
So this is color-coded and
the gray balls are carbon.

00:01:59.300 --> 00:02:01.610
The white ones are hydrogen.

00:02:01.610 --> 00:02:02.600
Those are the big ones.

00:02:02.600 --> 00:02:04.030
So most of life's molecules

00:02:04.030 --> 00:02:06.350
are made mostly of carbon and hydrogen.

00:02:06.350 --> 00:02:09.040
But we've also got oxygen here in red

00:02:09.040 --> 00:02:10.740
and nitrogen in blue,

00:02:10.740 --> 00:02:12.630
those are the other two big ones.

00:02:12.630 --> 00:02:13.570
And every now and then,

00:02:13.570 --> 00:02:15.880
we'll also find small amounts
of some other elements,

00:02:15.880 --> 00:02:18.210
like this sulfur here in yellow.

00:02:18.210 --> 00:02:20.110
But the super interesting part here

00:02:20.110 --> 00:02:23.050
is that these are actually
the same exact elements

00:02:23.050 --> 00:02:26.020
that make up most of
the cells in your body.

00:02:26.020 --> 00:02:27.500
So you may notice on this right-hand side

00:02:27.500 --> 00:02:30.380
the same colors is what
we have on the left.

00:02:30.380 --> 00:02:33.930
So this is where the whole
Molecular Lumber thing comes in.

00:02:33.930 --> 00:02:36.190
Our cells can take food

00:02:36.190 --> 00:02:38.880
and break it down into
small building blocks

00:02:38.880 --> 00:02:40.680
and then use those building blocks

00:02:40.680 --> 00:02:43.130
in order to build new
structures in our body.

00:02:43.130 --> 00:02:45.410
So is how we grow.

00:02:45.410 --> 00:02:48.000
This is how babies become adults.

00:02:48.000 --> 00:02:50.320
Turns out, we actually are what we eat.

00:02:50.320 --> 00:02:52.140
It's pretty amazing.

00:02:52.140 --> 00:02:54.090
All right, but before we get too excited,

00:02:54.090 --> 00:02:54.923
let's bring it in.

00:02:54.923 --> 00:02:56.880
So let's switch gears for a second here

00:02:56.880 --> 00:02:58.830
to talk about the other side of things

00:02:58.830 --> 00:03:02.170
because I told you before
that food is like wood.

00:03:02.170 --> 00:03:04.930
And we can use wood to
build new structures, sure.

00:03:04.930 --> 00:03:05.780
But when we need to,

00:03:05.780 --> 00:03:09.250
we can also burn wood to get energy.

00:03:09.250 --> 00:03:10.820
So we can start a campfire.

00:03:10.820 --> 00:03:13.250
And if we do, we know that
we're gonna get some energy

00:03:13.250 --> 00:03:14.530
in the form of light,

00:03:14.530 --> 00:03:16.660
we'll get some energy in the form of heat,

00:03:16.660 --> 00:03:19.300
and maybe some other things like sound.

00:03:19.300 --> 00:03:21.440
And food is actually the same way,

00:03:21.440 --> 00:03:23.610
and so we can take those
same food molecules

00:03:23.610 --> 00:03:25.980
that we broke down before
to get building blocks

00:03:25.980 --> 00:03:30.710
and instead use them as fuel
to generate cellular energy.

00:03:30.710 --> 00:03:33.020
And then we can use that cellular energy

00:03:33.020 --> 00:03:36.170
to fuel all of the building
that we just talked about.

00:03:36.170 --> 00:03:39.500
And likewise, if our cells
work together, which they do,

00:03:39.500 --> 00:03:42.290
they can use this energy
to do things like running,

00:03:42.290 --> 00:03:46.190
thinking, and all the other
things that we humans do.

00:03:46.190 --> 00:03:47.390
All right.

00:03:47.390 --> 00:03:49.620
Let's step back just one more time

00:03:49.620 --> 00:03:51.730
because what we'll see is
that these two processes

00:03:51.730 --> 00:03:53.130
that we've just described,

00:03:53.130 --> 00:03:55.950
so food is lumber and food is fuel

00:03:55.950 --> 00:03:58.500
actually explain so much of life.

00:03:58.500 --> 00:04:00.100
So this is not just us.

00:04:00.100 --> 00:04:02.620
Every living thing on
this planet is doing this.

00:04:02.620 --> 00:04:03.850
So you feed your dog

00:04:03.850 --> 00:04:07.293
to fuel his or her molecular
construction projects as well.

00:04:08.450 --> 00:04:09.820
So right there and then,

00:04:09.820 --> 00:04:12.520
we've already kind of answered
our question from before,

00:04:12.520 --> 00:04:14.060
which, reminder, was:

00:04:14.060 --> 00:04:16.830
how do people go from small to big?

00:04:16.830 --> 00:04:19.420
So what's happening is that
this baby becomes an adult

00:04:19.420 --> 00:04:22.520
by eating food, milk,
formula, gushy stuff,

00:04:22.520 --> 00:04:24.090
I don't know, whatever babies eat.

00:04:24.090 --> 00:04:25.700
And some of the molecules in that food

00:04:25.700 --> 00:04:28.580
will be used as fuel to generate energy,

00:04:28.580 --> 00:04:30.150
and then some of that energy

00:04:30.150 --> 00:04:32.550
will be used to combine food molecules

00:04:32.550 --> 00:04:34.500
with molecules in the baby

00:04:34.500 --> 00:04:37.690
to build up a larger baby, AKA an adult.

00:04:37.690 --> 00:04:39.410
All right, I hope that helps.

00:04:39.410 --> 00:04:40.370
Let's wrap it here.

00:04:40.370 --> 00:04:41.570
See you in the next one.


Fossils and rock layers

WEBVTT
Kind: captions
Language: en

00:00:00.033 --> 00:00:02.690
- [Instructor] Have you ever
wanted to travel back in time?

00:00:02.690 --> 00:00:04.720
Would you go meet your younger self?

00:00:04.720 --> 00:00:07.130
Would you go and ride a dinosaur?

00:00:07.130 --> 00:00:09.750
Or would you meticulously
create a timeline

00:00:09.750 --> 00:00:12.610
of the Earth's
4.6-billion-year long history

00:00:12.610 --> 00:00:14.780
based on major geological events?

00:00:14.780 --> 00:00:17.070
Even though geologists
can't go back in time,

00:00:17.070 --> 00:00:19.240
they've been able to do just that.

00:00:19.240 --> 00:00:22.150
Their timeline is called
geologic timescale

00:00:22.150 --> 00:00:24.000
and it breaks up all of Earth's history

00:00:24.000 --> 00:00:26.350
into units called eons and eras.

00:00:26.350 --> 00:00:28.540
And you may be wondering,
"How can we map out

00:00:28.540 --> 00:00:30.720
what happened on Earth
billions of years ago?"

00:00:30.720 --> 00:00:32.620
The answer is rocks.

00:00:32.620 --> 00:00:35.550
Geologists look for clues
in sedimentary rock layers,

00:00:35.550 --> 00:00:37.520
which we call strata.

00:00:37.520 --> 00:00:40.240
The fossil record, which
are the remains of organisms

00:00:40.240 --> 00:00:42.290
that have been preserved in rock layers

00:00:42.290 --> 00:00:45.750
can give us glimpses of
creatures that breathe long ago.

00:00:45.750 --> 00:00:48.050
Also, the difference
in mineral composition

00:00:48.050 --> 00:00:49.280
in different rock layers

00:00:49.280 --> 00:00:51.570
can tell geologists when a volcano erupted

00:00:51.570 --> 00:00:53.340
or an asteroid hit.

00:00:53.340 --> 00:00:55.380
But how did geologists
know when one rock layer

00:00:55.380 --> 00:00:56.850
is older than another?

00:00:56.850 --> 00:00:58.720
Well, when sedimentary rocks form,

00:00:58.720 --> 00:01:01.690
they're deposited in layers,
one on top of the other.

00:01:01.690 --> 00:01:04.460
So unless the layers are
disturbed or turned over,

00:01:04.460 --> 00:01:05.670
the layers at the bottom

00:01:05.670 --> 00:01:08.000
are always older than
the layers at the top.

00:01:08.000 --> 00:01:11.340
Geologists call this rule
the Law of Superposition.

00:01:11.340 --> 00:01:14.140
So if a geologist finds
a fossil of an ammonite

00:01:14.140 --> 00:01:17.250
in a layer of rock above a
fossil of a Dunkleosteus,

00:01:17.250 --> 00:01:19.310
the scientists would know
that the Dunkleosteus

00:01:19.310 --> 00:01:20.750
is older than the ammonite.

00:01:20.750 --> 00:01:23.200
This process is called relative dating

00:01:23.200 --> 00:01:25.470
because it helps scientists
determine the relative ages

00:01:25.470 --> 00:01:27.540
of rock layers and fossils.

00:01:27.540 --> 00:01:30.010
But what does relative ages mean?

00:01:30.010 --> 00:01:31.850
Let's say that I told you my friend Ava

00:01:31.850 --> 00:01:33.130
is younger than her sister,

00:01:33.130 --> 00:01:34.560
but older than her cat.

00:01:34.560 --> 00:01:37.430
Then, I wouldn't be telling
you Ava's exact age,

00:01:37.430 --> 00:01:41.290
but her relative age in relation
to her sister and her cat.

00:01:41.290 --> 00:01:44.010
Let's take a look at another
example of relative ages,

00:01:44.010 --> 00:01:45.630
this time, with rocks.

00:01:45.630 --> 00:01:47.890
Imagine that one day you found a big rock

00:01:47.890 --> 00:01:49.760
with many layers like this.

00:01:49.760 --> 00:01:52.070
Because the rock is a sedimentary rock

00:01:52.070 --> 00:01:54.420
and you remember the Law of Superposition,

00:01:54.420 --> 00:01:56.990
you know that the layers
at the bottom are older

00:01:56.990 --> 00:01:59.940
and you know that the
layers up here are younger.

00:01:59.940 --> 00:02:02.030
But what about this
section of rock right here

00:02:02.030 --> 00:02:04.450
that slices through the other layers?

00:02:04.450 --> 00:02:07.740
Geologists would call this
section an igneous intrusion

00:02:07.740 --> 00:02:10.980
since it was formed for
molten rock that has cooled.

00:02:10.980 --> 00:02:12.980
This particular igneous intrusion

00:02:12.980 --> 00:02:14.300
isn't clearly on top of

00:02:14.300 --> 00:02:16.560
or below any of the
sedimentary rock layers.

00:02:16.560 --> 00:02:19.230
So we can't use the Law
of Superposition here.

00:02:19.230 --> 00:02:21.640
Luckily, geologists have
figured out another rule

00:02:21.640 --> 00:02:24.370
called the law of
crosscutting relationships.

00:02:24.370 --> 00:02:26.650
This rule says that when
two geologic features cross

00:02:26.650 --> 00:02:27.770
or intersect,

00:02:27.770 --> 00:02:30.280
the feature that cuts
through the other is younger,

00:02:30.280 --> 00:02:31.290
and this makes sense

00:02:31.290 --> 00:02:34.120
because you can't break
something before it even exists.

00:02:34.120 --> 00:02:35.640
So since our igneous intrusion

00:02:35.640 --> 00:02:37.710
cuts through the layers
of the sedimentary rock,

00:02:37.710 --> 00:02:40.540
we know that it must be even
younger than the rock layers.

00:02:40.540 --> 00:02:43.360
And what about this
fault or break over here?

00:02:43.360 --> 00:02:45.350
Well, since it slice
through all the layers,

00:02:45.350 --> 00:02:46.880
as well as the igneous rock,

00:02:46.880 --> 00:02:48.810
the law of crosscutting relationships

00:02:48.810 --> 00:02:49.740
tells us that the faults

00:02:49.740 --> 00:02:52.680
must be the very youngest
geologic feature here.

00:02:52.680 --> 00:02:54.840
Other pieces of evidence, like fossils,

00:02:54.840 --> 00:02:56.580
could be used for relative dating.

00:02:56.580 --> 00:02:59.010
For example, suppose a
geologist found a rock

00:02:59.010 --> 00:03:01.410
containing fossils of extinct organisms

00:03:01.410 --> 00:03:04.550
and another rock that contained
fossils of modern organisms.

00:03:04.550 --> 00:03:06.010
The geologist could then deduce

00:03:06.010 --> 00:03:08.820
that the rock with the
extinct organisms is older.

00:03:08.820 --> 00:03:11.810
Certain kinds of fossils,
called index fossils,

00:03:11.810 --> 00:03:13.570
are especially helpful when determining

00:03:13.570 --> 00:03:15.010
the relative age of a rock.

00:03:15.010 --> 00:03:17.230
Index fossils are fossils
that are only found

00:03:17.230 --> 00:03:19.910
on a specific section of
the geologic timescale.

00:03:19.910 --> 00:03:22.690
I always remember what an
index fossil is like this.

00:03:22.690 --> 00:03:24.330
Just like I use my index finger

00:03:24.330 --> 00:03:26.230
to point to give directions,

00:03:26.230 --> 00:03:29.440
index fossils can point to
when on the geologic timescale

00:03:29.440 --> 00:03:30.750
a rock was formed.

00:03:30.750 --> 00:03:33.160
So if a geologist finds
the same index fossil

00:03:33.160 --> 00:03:35.230
in rock layers in two different rocks,

00:03:35.230 --> 00:03:37.150
they know that those rock
layers must have been formed

00:03:37.150 --> 00:03:38.830
around the same time period,

00:03:38.830 --> 00:03:40.450
but fossils aren't the only thing

00:03:40.450 --> 00:03:43.540
that can help geologists figure
out a rock's relative age.

00:03:43.540 --> 00:03:46.200
For example, if a geologist
found two rock layers

00:03:46.200 --> 00:03:48.520
that contained evidence of
the same geologic event,

00:03:48.520 --> 00:03:51.230
like a layer of ash from
a major volcanic eruption,

00:03:51.230 --> 00:03:52.610
the geologists could deduce

00:03:52.610 --> 00:03:54.770
that those rock layers
were made at the same time.

00:03:54.770 --> 00:03:56.710
Relative dating is how
geologists figured out

00:03:56.710 --> 00:03:58.320
that Stegosauruses were extinct

00:03:58.320 --> 00:04:00.720
long before T-Rex's even existed.

00:04:00.720 --> 00:04:02.070
It also helped them figure out

00:04:02.070 --> 00:04:03.670
the first single cellular life

00:04:03.670 --> 00:04:06.270
formed about 3.8 billion years ago

00:04:06.270 --> 00:04:08.080
and the first multicellular life

00:04:08.080 --> 00:04:10.460
formed about 600 million years ago,

00:04:10.460 --> 00:04:13.300
and they figured out that
modern humans didn't even exist

00:04:13.300 --> 00:04:15.360
until about 200,000 years ago,

00:04:15.360 --> 00:04:18.740
which is right at the very end
of the geologic time scale.

00:04:18.740 --> 00:04:21.270
In other words, it took a
really, really long time

00:04:21.270 --> 00:04:23.810
for life to evolve into
what it looks like today.

00:04:23.810 --> 00:04:25.530
We, humans, are very young

00:04:25.530 --> 00:04:27.770
in the grand scheme of
the Earth's history.

00:04:27.770 --> 00:04:29.260
Now, if you'll excuse me,

00:04:29.260 --> 00:04:31.540
I'm gonna go saddle and
ride this Brontosaurus.

00:04:31.540 --> 00:04:33.014
Let's go, ginger snap!

00:04:33.014 --> 00:04:33.847
Hyah!


Phases of the moon

WEBVTT
Kind: captions
Language: en

00:00:00.350 --> 00:00:01.740
- [Narrator] Imagine that one day,

00:00:01.740 --> 00:00:04.650
all of the clocks and
computers on Earth broke,

00:00:04.650 --> 00:00:06.840
and all the calendars disappeared.

00:00:06.840 --> 00:00:09.470
How would you keep track of
how much time had passed?

00:00:09.470 --> 00:00:11.680
Well, you could look to the Moon.

00:00:11.680 --> 00:00:13.760
Humans have used the Moon
to keep track of time

00:00:13.760 --> 00:00:15.290
for thousands of years.

00:00:15.290 --> 00:00:17.460
It isn't a coincidence that the word moon

00:00:17.460 --> 00:00:20.020
is related to the word
month in old English.

00:00:20.020 --> 00:00:22.910
The Moon is Earth's
only natural satellite.

00:00:22.910 --> 00:00:25.290
A natural satellite is a
naturally occurring body

00:00:25.290 --> 00:00:26.840
that orbits a planet.

00:00:26.840 --> 00:00:28.490
Some of the planets in our solar system

00:00:28.490 --> 00:00:30.760
have more than 50 satellites or moons,

00:00:30.760 --> 00:00:32.600
but the Earth just has one.

00:00:32.600 --> 00:00:35.150
The Moon does not generate its own light.

00:00:35.150 --> 00:00:36.560
We can see the Moon from the Earth,

00:00:36.560 --> 00:00:39.130
because it is partially lit
by the light from the sun.

00:00:39.130 --> 00:00:41.360
In fact, moonlight is just sunlight

00:00:41.360 --> 00:00:43.360
reflected from the Moon onto Earth.

00:00:43.360 --> 00:00:45.280
The Moon takes about 27 days

00:00:45.280 --> 00:00:47.110
to make a full orbit around Earth.

00:00:47.110 --> 00:00:49.530
And as it does, the lit part of the Moon

00:00:49.530 --> 00:00:51.940
appears to change shape
to us here on Earth.

00:00:51.940 --> 00:00:56.310
These shapes are called the
moon phases, or lunar phases.

00:00:56.310 --> 00:00:58.870
So why do we see different lunar phases?

00:00:58.870 --> 00:01:02.690
Well, the 27 days it takes the
Moon to orbit the Earth once

00:01:02.690 --> 00:01:03.600
is the same amount of time

00:01:03.600 --> 00:01:06.050
it takes the Moon to
rotate on its axis once.

00:01:06.050 --> 00:01:07.680
This means that the same side of the Moon

00:01:07.680 --> 00:01:09.170
is always facing us.

00:01:09.170 --> 00:01:11.210
At the same time, the sun always lights up

00:01:11.210 --> 00:01:12.750
half of the sphere of the Moon.

00:01:12.750 --> 00:01:14.970
However, the side of the
Moon that's facing us

00:01:14.970 --> 00:01:16.590
isn't always the same part of the Moon

00:01:16.590 --> 00:01:17.930
that the sun lights up.

00:01:17.930 --> 00:01:19.928
This causes the Moon to appear
to have different shapes,

00:01:19.928 --> 00:01:21.300
or faces in the sky,

00:01:21.300 --> 00:01:22.870
depending on the time of the month.

00:01:22.870 --> 00:01:25.330
Let's take a closer look
at the Moon's phases.

00:01:25.330 --> 00:01:27.200
First, we have the new moon,

00:01:27.200 --> 00:01:29.360
which happens when the
Moon is closest to the sun

00:01:29.360 --> 00:01:30.330
in its orbit.

00:01:30.330 --> 00:01:32.160
During this phase, the
lit side of the Moon

00:01:32.160 --> 00:01:34.020
is completely facing away from Earth.

00:01:34.020 --> 00:01:36.040
So it looks like the Moon has disappeared.

00:01:36.040 --> 00:01:38.820
In a day or two, we'd be able
to see a little sliver of moon

00:01:38.820 --> 00:01:40.410
in the sky.

00:01:40.410 --> 00:01:41.900
Over the next few days,

00:01:41.900 --> 00:01:44.660
the crescent moon will appear
to get bigger and bigger.

00:01:44.660 --> 00:01:46.050
When the Moon appears to get bigger

00:01:46.050 --> 00:01:48.800
from one day to the next, we
say that the Moon is waxing.

00:01:48.800 --> 00:01:49.780
So this phase of the Moon

00:01:49.780 --> 00:01:52.010
is called the waxing crescent moon.

00:01:52.010 --> 00:01:53.330
You might notice that sometimes

00:01:53.330 --> 00:01:55.680
we can still see the rest
of the Moon in the shadow.

00:01:55.680 --> 00:01:58.450
This is because the Earth
reflects sunlight onto the Moon,

00:01:58.450 --> 00:02:00.570
just like the Moon
reflects light onto Earth.

00:02:00.570 --> 00:02:03.090
Eventually, the Moon appears
to change shape so much

00:02:03.090 --> 00:02:04.710
that it isn't a crescent anymore,

00:02:04.710 --> 00:02:06.700
but a half circle in the sky.

00:02:06.700 --> 00:02:08.990
This is called a first quarter moon.

00:02:08.990 --> 00:02:10.080
There are two ways to think about

00:02:10.080 --> 00:02:12.250
why this phase is called a quarter moon.

00:02:12.250 --> 00:02:14.840
Even though it looks like
the Moon is half illuminated,

00:02:14.840 --> 00:02:16.550
the Moon is a sphere.

00:02:16.550 --> 00:02:19.420
So we can only ever see
half of the Moon from Earth.

00:02:19.420 --> 00:02:20.540
During a quarter moon,

00:02:20.540 --> 00:02:23.460
the Moon forms a right angle
with Earth and the sun.

00:02:23.460 --> 00:02:25.450
This means that we a half lit portion

00:02:25.450 --> 00:02:27.460
of the half of the Moon
that's always facing us.

00:02:27.460 --> 00:02:30.260
It's half of a half, so it's a quarter.

00:02:30.260 --> 00:02:31.950
Also, a first quarter moon

00:02:31.950 --> 00:02:33.950
occurs when the Moon is a
quarter of the way through

00:02:33.950 --> 00:02:35.490
its new cycle.

00:02:35.490 --> 00:02:37.930
Next, there's the waxing gibbous moon.

00:02:37.930 --> 00:02:41.160
The word gibbous comes from the
Latin word meaning humpback.

00:02:41.160 --> 00:02:43.880
Once the Moon is farthest
from the sun in its orbit,

00:02:43.880 --> 00:02:46.350
the full sun lit side
of the Moon faces Earth.

00:02:46.350 --> 00:02:48.610
We call this phase the full moon,

00:02:48.610 --> 00:02:51.000
but the Moon is not done yet.

00:02:51.000 --> 00:02:53.630
It's only finished half of the cycle.

00:02:53.630 --> 00:02:56.470
Next, we have the same
phases, but in reverse.

00:02:56.470 --> 00:02:58.840
As the Moon appears to
get smaller and smaller,

00:02:58.840 --> 00:03:00.520
we say that it's waning.

00:03:00.520 --> 00:03:02.500
The full Moon appears to shrink,

00:03:02.500 --> 00:03:04.900
and then we see a waning gibbous.

00:03:04.900 --> 00:03:06.810
Then there's the third quarter moon.

00:03:06.810 --> 00:03:08.700
This happens when the
Moon is three quarters

00:03:08.700 --> 00:03:09.940
the way done with its cycle,

00:03:09.940 --> 00:03:11.580
and the Moon forms another right angle

00:03:11.580 --> 00:03:12.930
with the sun and the Earth.

00:03:12.930 --> 00:03:15.140
The Moon appears to shrink even more,

00:03:15.140 --> 00:03:17.520
and it becomes a waning crescent,

00:03:17.520 --> 00:03:20.550
and the cycle starts anew
with another new moon.

00:03:20.550 --> 00:03:23.760
Even though the Moon completes
an orbit every 27 days,

00:03:23.760 --> 00:03:27.810
the lunar phases actually
repeat about every 29.5 days.

00:03:27.810 --> 00:03:29.833
This is because the Earth
is revolving around the sun

00:03:29.833 --> 00:03:31.830
while the Moon completes its orbit.

00:03:31.830 --> 00:03:34.960
So the Moon has to travel
a little extra to catch up.

00:03:34.960 --> 00:03:36.570
The Moon isn't just something beautiful

00:03:36.570 --> 00:03:37.740
to look at in the sky,

00:03:37.740 --> 00:03:40.010
or just an easy way to keep track of time.

00:03:40.010 --> 00:03:42.240
The Moon's gravity controls the tides,

00:03:42.240 --> 00:03:44.660
which are the rise and
fall of water in oceans,

00:03:44.660 --> 00:03:46.180
lakes, and rivers.

00:03:46.180 --> 00:03:50.320
Tides allow for unique ecosystems,
like tide pools to exist.

00:03:50.320 --> 00:03:52.400
And we can use the tides
to create electricity,

00:03:52.400 --> 00:03:53.900
and tidal power plants.

00:03:53.900 --> 00:03:56.800
The Moon also helps keep
Earth's access stable.

00:03:56.800 --> 00:03:59.130
Without it, our planet would
wobble more dramatically

00:03:59.130 --> 00:04:01.370
on its axis over long periods of time,

00:04:01.370 --> 00:04:03.950
which would change up our
weather and our seasons.

00:04:03.950 --> 00:04:05.230
So even though your calendar

00:04:05.230 --> 00:04:08.050
is pretty unlikely to
spontaneously combust tomorrow,

00:04:08.050 --> 00:04:09.350
you could still thank the Moon

00:04:09.350 --> 00:04:11.240
for being such a stabilizing influence,

00:04:11.240 --> 00:04:12.953
and good companion to our planet.


Potential energy

WEBVTT
Kind: captions
Language: en

00:00:00.330 --> 00:00:01.410
- [Narrator] Hello, everyone.

00:00:01.410 --> 00:00:03.960
Let's talk about potential energy.

00:00:03.960 --> 00:00:07.090
Potential energy is energy
that is stored in an object,

00:00:07.090 --> 00:00:08.310
and this energy is related

00:00:08.310 --> 00:00:10.780
to the potential or the future possibility

00:00:10.780 --> 00:00:12.890
for an object to have a
different type of energy,

00:00:12.890 --> 00:00:14.900
like kinetic energy for motion,

00:00:14.900 --> 00:00:17.310
that is converted from
that potential energy.

00:00:17.310 --> 00:00:19.060
There are many kinds of potential energy,

00:00:19.060 --> 00:00:21.230
but they all arise from
an object's relation

00:00:21.230 --> 00:00:23.703
to a position, or an original shape.

00:00:25.490 --> 00:00:26.520
So while in general,

00:00:26.520 --> 00:00:28.620
there are many different
types of potential energy,

00:00:28.620 --> 00:00:30.786
there are several specific
types that are very common.

00:00:30.786 --> 00:00:33.200
So, let's talk about these.

00:00:33.200 --> 00:00:34.770
Gravitational potential energy

00:00:34.770 --> 00:00:37.650
is the potential energy
that an object with mass has

00:00:37.650 --> 00:00:40.290
due to the force of gravity
from another object with mass,

00:00:40.290 --> 00:00:42.190
like say, the Earth.

00:00:42.190 --> 00:00:44.350
And in fact, we often use
the surface of the Earth

00:00:44.350 --> 00:00:45.748
to compare an object's position with

00:00:45.748 --> 00:00:47.620
to see how much potential energy it has

00:00:47.620 --> 00:00:50.570
in the Earth's gravitational field.

00:00:50.570 --> 00:00:52.230
Gravity is an attractive force,

00:00:52.230 --> 00:00:53.810
so objects with mass want to move

00:00:53.810 --> 00:00:55.490
towards the surface of the Earth.

00:00:55.490 --> 00:00:57.110
If we move them further away,

00:00:57.110 --> 00:00:59.430
or opposite the direction
of the gravitational force,

00:00:59.430 --> 00:01:02.150
we increase their
gravitational potential energy.

00:01:02.150 --> 00:01:04.593
And the opposite is
true if it gets closer.

00:01:05.910 --> 00:01:07.680
When an object is on the surface of Earth,

00:01:07.680 --> 00:01:09.970
we typically say it has
no potential energy,

00:01:09.970 --> 00:01:12.320
but you could use any
point to be this comparison

00:01:12.320 --> 00:01:15.180
where potential energy is zero.

00:01:15.180 --> 00:01:16.900
Consider a book on a bookshelf.

00:01:16.900 --> 00:01:18.570
If the book is on this shelf,

00:01:18.570 --> 00:01:22.330
we can use this shelf as
the 0.4 potential energy.

00:01:22.330 --> 00:01:23.670
Moving it to a higher shelf

00:01:23.670 --> 00:01:26.070
would mean it has
gravitational potential energy

00:01:26.070 --> 00:01:28.430
relative to that lower shelf,

00:01:28.430 --> 00:01:30.040
or relative to the floor

00:01:30.040 --> 00:01:32.490
if we want to use that as
our comparison instead.

00:01:34.070 --> 00:01:36.500
Next, we have elastic potential energy,

00:01:36.500 --> 00:01:37.780
which is the potential energy

00:01:37.780 --> 00:01:40.790
some objects have due to
their shape being changed.

00:01:40.790 --> 00:01:44.020
These types of objects are
called elastic objects.

00:01:44.020 --> 00:01:46.540
Elastic objects are made
of materials and designed,

00:01:46.540 --> 00:01:49.050
so they have internal or inside forces

00:01:49.050 --> 00:01:52.260
that try to return them
to their original shape.

00:01:52.260 --> 00:01:55.120
One very common example
of this is a spring.

00:01:55.120 --> 00:01:58.310
When you stretch or compress a
spring, you change its shape.

00:01:58.310 --> 00:02:00.420
And the shape of the spring
causes internal forces

00:02:00.420 --> 00:02:04.300
that try to return the
spring to its original shape.

00:02:04.300 --> 00:02:05.797
Now electric potential energy,

00:02:05.797 --> 00:02:08.970
which is the potential
energy a charged object has

00:02:08.970 --> 00:02:12.560
due to the electric force
from another charged object.

00:02:12.560 --> 00:02:15.470
Opposite electric charges
are attracted to one another,

00:02:15.470 --> 00:02:18.210
and similar electric charges are repelled.

00:02:18.210 --> 00:02:19.380
So the potential energy

00:02:19.380 --> 00:02:21.087
depends on what type of charges there are,

00:02:21.087 --> 00:02:23.810
and how far apart they are.

00:02:23.810 --> 00:02:25.500
Potential energy increases

00:02:25.500 --> 00:02:27.192
when the charges move
opposite the direction

00:02:27.192 --> 00:02:28.710
of the electric force,

00:02:28.710 --> 00:02:33.030
for example, when two negative
charges get closer together.

00:02:33.030 --> 00:02:35.250
Similarly, magnetic potential energy

00:02:35.250 --> 00:02:37.920
is the potential energy
a magnetic object has

00:02:37.920 --> 00:02:41.140
due to the magnetic force
from another magnet.

00:02:41.140 --> 00:02:44.210
Magnetic force causes similar
poles to repel one another,

00:02:44.210 --> 00:02:46.290
and opposite poles to attract.

00:02:46.290 --> 00:02:49.180
And because magnets have
north and south poles,

00:02:49.180 --> 00:02:51.110
the potential energy depends not only

00:02:51.110 --> 00:02:52.640
on the position within a field,

00:02:52.640 --> 00:02:55.470
but also the magnets orientation.

00:02:55.470 --> 00:02:57.830
Again, you could increase
the potential energy

00:02:57.830 --> 00:03:00.010
by moving the magnets
opposite the direction

00:03:00.010 --> 00:03:01.250
of the magnetic force.

00:03:01.250 --> 00:03:05.240
For example, by pulling apart
a North Pole and a South Pole.

00:03:05.240 --> 00:03:07.900
All of these types of energy
are due to different forces,

00:03:07.900 --> 00:03:10.400
and are calculated differently
from different equations,

00:03:10.400 --> 00:03:11.830
which we won't cover here,

00:03:11.830 --> 00:03:14.570
but they are all potential energy.

00:03:14.570 --> 00:03:16.550
And these are just a few
of the most common types

00:03:16.550 --> 00:03:18.940
of potential energy, but there are more.

00:03:18.940 --> 00:03:21.470
In summary, potential
energy is the stored energy

00:03:21.470 --> 00:03:23.720
in an object due to its
position, its properties,

00:03:23.720 --> 00:03:25.730
and the forces acting on it.

00:03:25.730 --> 00:03:26.890
Potential energy is measured

00:03:26.890 --> 00:03:29.290
relative to some comparison
position or shape,

00:03:29.290 --> 00:03:32.050
and describes the potential
for other forms of energy,

00:03:32.050 --> 00:03:35.630
commonly kinetic energy
for motion, to exist.

00:03:35.630 --> 00:03:37.610
There are many forms of potential energy,

00:03:37.610 --> 00:03:41.100
including gravitational,
elastic, magnetic, and electric.

00:03:41.100 --> 00:03:41.933
Thanks for watching,

00:03:41.933 --> 00:03:44.053
and I hope you learned a
little bit of something.


Worked example: analyzing a generic food web

WEBVTT
Kind: captions
Language: en

00:00:00.550 --> 00:00:03.470
- [Narrator] What we have here
is a diagram of a food web

00:00:03.470 --> 00:00:05.650
that shows us how matter and energy

00:00:05.650 --> 00:00:09.420
are transferred between
organisms in an ecosystem.

00:00:09.420 --> 00:00:10.550
But it's a little bit abstract,

00:00:10.550 --> 00:00:12.370
they don't tell us what
these organisms are.

00:00:12.370 --> 00:00:14.310
They just say organism one, organism two,

00:00:14.310 --> 00:00:16.950
organism three, and so forth.

00:00:16.950 --> 00:00:19.680
But even this gives us some information

00:00:19.680 --> 00:00:22.250
about which organism are the producers,

00:00:22.250 --> 00:00:25.120
the primary consumers,
the secondary consumers,

00:00:25.120 --> 00:00:27.310
and the decomposers.

00:00:27.310 --> 00:00:30.240
So the first thing I want
you to think about is

00:00:30.240 --> 00:00:35.020
which arrows show us going from producers,

00:00:35.020 --> 00:00:36.500
I'll write it like,

00:00:36.500 --> 00:00:39.860
to primary consumers?

00:00:39.860 --> 00:00:41.210
Pause the video and think about that.

00:00:41.210 --> 00:00:44.793
Which arrows show producers
to primary consumers?

00:00:46.310 --> 00:00:48.320
All right, now in a food web,

00:00:48.320 --> 00:00:51.070
the giveaway that something is a producer

00:00:51.070 --> 00:00:53.990
is that it doesn't have
arrows coming into it,

00:00:53.990 --> 00:00:56.360
it only has arrows coming out of it.

00:00:56.360 --> 00:01:01.210
And so organism one is a producer.

00:01:01.210 --> 00:01:05.730
Organism five is also a producer.

00:01:05.730 --> 00:01:07.890
Where are they getting their
matter and energy from?

00:01:07.890 --> 00:01:10.330
Well, they're getting their
matter from the environment

00:01:10.330 --> 00:01:13.970
and the energy, in most
cases, is coming from the sun.

00:01:13.970 --> 00:01:16.350
And the things that eat the producers,

00:01:16.350 --> 00:01:18.350
those are primary consumers.

00:01:18.350 --> 00:01:20.720
So this is an arrow that
goes from a producer

00:01:20.720 --> 00:01:22.310
to a primary consumer.

00:01:22.310 --> 00:01:24.520
This is an arrow that goes from a producer

00:01:24.520 --> 00:01:26.100
to a primary consumer.

00:01:26.100 --> 00:01:29.350
And this is an arrow
that goes from a producer

00:01:29.350 --> 00:01:31.840
to a primary consumer.

00:01:31.840 --> 00:01:33.500
Now, with that out of the way,

00:01:33.500 --> 00:01:38.400
which arrows show us going
from a primary consumer

00:01:39.290 --> 00:01:42.900
to a secondary consumer?

00:01:42.900 --> 00:01:45.440
Pause the video and think about that.

00:01:45.440 --> 00:01:47.670
Well, I just said that these things

00:01:47.670 --> 00:01:49.470
that are consuming the producers,

00:01:49.470 --> 00:01:52.930
these are primary, I'll
just say P for primary,

00:01:52.930 --> 00:01:54.580
primary consumer.

00:01:54.580 --> 00:01:57.070
This is a primary consumer.

00:01:57.070 --> 00:02:00.320
This is a primary consumer, as well.

00:02:00.320 --> 00:02:02.350
Now secondary consumers are by definition

00:02:02.350 --> 00:02:04.120
things that aren't decomposers,

00:02:04.120 --> 00:02:06.620
but they're eating primary consumers.

00:02:06.620 --> 00:02:08.710
So they're going to have arrows coming in

00:02:08.710 --> 00:02:11.400
from primary consumers and out

00:02:11.400 --> 00:02:15.040
to either other secondary
consumers or to decomposers.

00:02:15.040 --> 00:02:20.040
So organism three right over
here is a secondary consumer.

00:02:20.540 --> 00:02:22.070
So we're going from a primary consumer

00:02:22.070 --> 00:02:23.140
to a secondary consumer.

00:02:23.140 --> 00:02:25.610
So this arrow is from a primary consumer

00:02:25.610 --> 00:02:27.530
to a secondary consumer.

00:02:27.530 --> 00:02:29.780
This arrow over here is interesting.

00:02:29.780 --> 00:02:32.260
It's a secondary consumer being consumed,

00:02:32.260 --> 00:02:33.790
but you can see that organism four

00:02:33.790 --> 00:02:35.900
only has arrows going into it,

00:02:35.900 --> 00:02:39.070
which is a pretty good clue
that this is a decomposer.

00:02:39.070 --> 00:02:43.003
So I'm not going to call
organism four a secondary,

00:02:43.920 --> 00:02:45.850
a secondary consumer.

00:02:45.850 --> 00:02:47.580
So let's keep going.

00:02:47.580 --> 00:02:50.960
What about the arrow that
goes from organism six

00:02:50.960 --> 00:02:52.110
to organism seven?

00:02:52.110 --> 00:02:55.770
That looks like primary
consumer to primary consumer.

00:02:55.770 --> 00:02:57.060
Well, it turns out that something can be

00:02:57.060 --> 00:03:00.260
both a primary consumer
and a secondary consumer.

00:03:00.260 --> 00:03:03.010
So this is also a secondary consumer.

00:03:03.010 --> 00:03:06.230
Why, because it's eating
a primary consumer

00:03:06.230 --> 00:03:07.830
and it's not a decomposer,

00:03:07.830 --> 00:03:09.470
so this is also another example

00:03:09.470 --> 00:03:11.600
of an arrow from a primary consumer

00:03:11.600 --> 00:03:14.230
to a secondary consumer.

00:03:14.230 --> 00:03:15.770
Last but not least,

00:03:15.770 --> 00:03:19.200
what are the arrows
that go from a consumer,

00:03:19.200 --> 00:03:23.210
that go from a consumer, to a decomposer?

00:03:23.210 --> 00:03:25.330
And we already broke
this down a little bit,

00:03:25.330 --> 00:03:27.340
no pun intended.

00:03:27.340 --> 00:03:29.880
Pause the video and try
to think about that.

00:03:29.880 --> 00:03:32.290
Well, this is the only decomposer

00:03:32.290 --> 00:03:34.050
that's depicted in this diagram,

00:03:34.050 --> 00:03:37.420
and so this is going from
a consumer to a decomposer,

00:03:37.420 --> 00:03:38.600
right over here.

00:03:38.600 --> 00:03:42.570
This is from a consumer to a decomposer,

00:03:42.570 --> 00:03:44.210
and that's all we have here.

00:03:44.210 --> 00:03:46.069
And to be clear, you don't have to go

00:03:46.069 --> 00:03:48.500
only from a consumer to decomposer.

00:03:48.500 --> 00:03:50.500
You could have gone from a producer

00:03:50.500 --> 00:03:51.880
straight to a decomposer.

00:03:51.880 --> 00:03:54.340
You could have arrows that
look like that, as well,

00:03:54.340 --> 00:03:58.330
because if a plant dies
and it gets decomposed,

00:03:58.330 --> 00:04:00.270
well, it's going to be,
that matter and energy

00:04:00.270 --> 00:04:02.523
is going to be used by that decomposer.