Human evolution overview

WEBVTT
Kind: captions
Language: en

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If we were to rewind the clock
back about 70 million years,

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you would see dinosaurs
roaming the Earth.

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And this is a very nice picture
here of a dinosaur enjoying

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a sunset at the beach.

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But unfortunately
for the dinosaurs,

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about 65 million years ago, we
believe that a huge meteorite

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struck the earth and essentially
wiped out the dinosaurs.

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And it probably wiped out a
bunch of other species with it.

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Because you can
imagine, the shock wave

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itself would just
exterminate tons of species.

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Then you would have the
tsunami of unimaginable size

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that would just
envelop the continents

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for some period of time.

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And then you would have
all of the soot that

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would go into the air and maybe
make it impossible for most

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of the plant species
to live, because it

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would be blocking out
all of the sunlight.

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And so in an
environment like that,

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we could imagine that
an animal like this

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would be well suited to survive.

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It's sitting there underground.

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Maybe it can
hibernate in some way,

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so it doesn't need food
for long periods of time.

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Maybe it has its own food
stash under there someplace.

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And so we believe that our
ancient, ancient, ancient,

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ancient, ancient ancestors,
after this mass extinction

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event, might have been
something like this-- kind

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of a mole-looking, rodent animal
that was protected from all

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of this craziness that was
happening on the surface,

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because they like to hang
out underground and have

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all their food nearby them.

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And maybe they could
hibernate in some way.

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So you could imagine, once
everything settled down--

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and now we're
talking, who knows,

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hundreds of years, thousands of
years, even millions of years--

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some of this guy's descendants
start to poke their head out

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of the ground.

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And they're like, you know what?

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There's food in trees.

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And there's no one
else in the trees.

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And trees are a good
place to maybe get away

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from some of the
other predators that

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have managed to survive
this mass extinction event.

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And some of its
descendants, I should say,

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that were good at climbing
trees decide, hey, let's

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try this tree thing out.

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And so you started to have some
selection for the descendants

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of this rodent that
could climb trees well.

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They were able to find
food where their ancestors

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couldn't .

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They could find protection in
the trees where their ancestors

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couldn't.

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And so you could imagine that
some subset of this guy's

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descendants evolved
into something

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that might have
looked like this guy.

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And all the pictures
I'm showing you,

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these are of modern
animals, except for,

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of course, the dinosaur.

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I'm sure this was kind of
Photoshopped in some way.

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This is a modern bush baby.

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But I show this
picture because it

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could have been what some
of these primitive primates

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looked like.

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Because a bush baby, it
kind of a climbs trees.

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It kind of looks like it's
starting to get a hand here

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to start climbing the trees.

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But it also has
rodent-like qualities.

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But this is, of course,
a modern version of it.

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So this bush baby's ancient,
ancient, ancient ancestor

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might have been that
primitive primate

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or that species of
primitive primate

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that was a descendant of rodents
that starts to say, hey, let's

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see if we can climb these
trees and find some food.

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And then some of its
descendants might

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have had just the right
adaptations, found

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their own little niche
in the right ecosystems.

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And they would have
evolved into monkeys.

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Once again, this
is a modern monkey,

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but you could imagine some
type of primitive monkey.

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And then some of those
primitive monkeys' descendants,

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they turn into these
modern monkeys eventually.

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But some of them, they
grow larger in size.

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They spend more time
outside of trees.

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They lose their tail.

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They don't need it
as much for balance.

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Maybe it's actually
a bad thing to have,

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because someone
else could grab it

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when you're in a fight
or something like that.

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And they evolve into apes, and
in particular, the great apes.

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So one of the great apes.

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The great apes involve
gorillas and chimpanzees

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and the ancestor.

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Or really, the great apes
also include humanity.

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So let me just review
back on this timeline,

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just so that we
don't get confused.

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I'll review what we
just talked about.

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So before this mass
extinction event,

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65 million years ago, you had
all these types of species

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here.

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Maybe this right up here.

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Actually, if I'm
talking about species,

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maybe this was
Tyrannosaurus Rex,

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because the dinosaurs
involve whole bunch

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of-- so this might
have been T Rex.

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And there's a bunch of species
that we could list over here.

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But after that mass
extinction event,

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that was an endpoint
for a ton of species,

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except for maybe this primitive
rodent mole-like thing.

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Maybe a lot of them
died in this event.

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But just enough of them survived
because they were underground

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or just in the
right place or they

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were in a mountain someplace.

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Who knows where they were?

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And some of them were able to
evolve into primitive primates.

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And once again, these are
pictures of primitive primates.

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And when I say primitive, these
are modern versions of them.

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So primitive doesn't necessarily
mean worse, because obviously,

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these guys, even
in today's world,

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they have a niche
for themselves.

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They're able to find
food and reproduce

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in ways that don't get in
the way of other people

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and the way people don't
get in the way of them.

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When I talk about
primitive primate,

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I'm just talking about kind
of an ancestral primate, maybe

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something that's
not there today.

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Although maybe some of those
descendents look very much

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like it.

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But anyway, some
of those primates

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evolve into primitive monkeys.

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Some of those primitive
monkeys' descendants

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become modern monkeys.

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So I'll call it M monkeys,
for Modern monkeys.

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And some of them evolve
into primitive apes.

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And apes, their
distinctive characteristic

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is that they're like monkeys,
but they don't have tails,

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and they're larger
than most monkeys.

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And so these primitive apes,
some of their descendants

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are modern gorillas.

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At some point, they break off.

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Some of these descendants
are an ancestor

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of both modern chimpanzees
and of human beings.

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And we think, just looking
at the DNA evidence,

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we think that this
departure right

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here-- and the
fossil evidence-- was

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about seven million years ago.

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That's our best guess for
when we, as human beings,

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had a common ancestor
with the chimpanzees.

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Now, you have that
common ancestor.

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Some of that common
ancestor's descendants

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became modern chimpanzees.

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And some of them-- maybe they
explored the right ecosystem,

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where it was more
advantageous to do so--

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started to walk on two legs.

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And the most famous
fossil of this

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is the australopithicine
fossil of Lucy

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that was discovered
3.2 million years-- it

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was discovered more recently.

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It's 3.2 million years old.

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So the whole
genus-- and genus is

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kind of one level of
categorization above species.

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The whole genus of
australopithecine, these

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were four to two
million years ago.

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And we never know.

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You could always
find a fossil that's

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older than this,
maybe newer than this.

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I read one account that says,
maybe one million years ago.

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But give or take,
the Lucy fossil,

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which is the most
well established

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australopithecine fossil, is
about three million years old.

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And this is a reconstruction
I have over here of Lucy.

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So this is probably
what Lucy looked like.

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And once again, there
were many Lucys.

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It wasn't just
there was one Lucy.

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And we're all
descended from Lucys.

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And it's actually not
even clear that we're even

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descended directly
from australopithecine.

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We might be a cousin species or
a cousin genus, I should say.

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Genus is the category
right above species.

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So if you fast forward
a little bit more-- you

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go to about 2.3 to 1.4
million years ago--

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we see fossils that
they're standing upright.

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The brain size is bigger.

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Because if you look at the
australopithecine fossils,

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they are standing upright.

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But they're cranial
capacity isn't

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that different than chimpanzees.

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You fast forward to 2.3 million
to 1.4 million years ago,

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we start to see fossils where
they're standing upright still.

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And the cranial
capacity has grown.

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And you're starting
to see primitive stone

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tools around the bone fossils.

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And so we believe that
these are one of the first.

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And this is really just
how we categorize it.

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But these are some of the first
fossils that we categorize

00:08:01.700 --> 00:08:04.750
as belonging to the
same genus as ours.

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And the genus is Homo.

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And Homo just means man.

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So it's the group right
above species of man.

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And we call them similar
to man, because it

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looks like they're starting
to make primitive stone tools.

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And they stand upright like us.

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And they have larger
cranial capacities

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than the australopithecine
fossils or modern chimpanzees.

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And once again, we don't know
if Homo habilis, which literally

00:08:31.382 --> 00:08:32.840
means-- so the Homo
part means man.

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Habilis means handy, because he
liked to, I guess, make tools

00:08:36.520 --> 00:08:37.419
or whatever else.

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We don't know if Homo habilis is
a descendant of Lucy's species

00:08:41.840 --> 00:08:45.140
of Australopithecus or
maybe a cousin species.

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Maybe they're both descendents
from some common ancestor.

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We're not quite sure.

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Then you fast forward
a little bit more.

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We're talking now about 1.8
to 1.38 million years ago.

00:09:00.200 --> 00:09:03.880
And we start seeing fossils
where the cranial capacity

00:09:03.880 --> 00:09:07.360
larger than Homo habilis,
getting closer in size

00:09:07.360 --> 00:09:12.530
to what our notion is of
kind of a modern person's

00:09:12.530 --> 00:09:15.820
cranial capacity, at least
relative to body size.

00:09:15.820 --> 00:09:18.225
And this is Homo erectus.

00:09:18.225 --> 00:09:20.100
And once again, we don't
know if Homo erectus

00:09:20.100 --> 00:09:21.920
is the descendant
of Homo habilis.

00:09:21.920 --> 00:09:24.050
Maybe they have a
common ancestor.

00:09:24.050 --> 00:09:24.640
Who knows?

00:09:24.640 --> 00:09:26.280
And it looks from
the fossil evidence

00:09:26.280 --> 00:09:28.990
that there was, especially when
you look at this range here,

00:09:28.990 --> 00:09:32.180
some overlap where you had
both Homo erectus and Homo

00:09:32.180 --> 00:09:36.210
habilis living on the same
planet at the same time.

00:09:36.210 --> 00:09:38.340
Now, you fast forward even more.

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And we think about 600,000
to 300,000-- once again,

00:09:43.570 --> 00:09:45.890
all of these are
constantly being modified,

00:09:45.890 --> 00:09:48.370
as we get better at
finding new fossils

00:09:48.370 --> 00:09:49.880
or interpreting
the fossils we have

00:09:49.880 --> 00:09:51.920
or we look at DNA
evidence or whatever.

00:09:51.920 --> 00:09:56.980
About 600,000 to 300,000 years
ago, the Neanderthals appear.

00:09:56.980 --> 00:10:00.340
And Neanderthals are in
the same genus as humans.

00:10:00.340 --> 00:10:03.534
So it's really Homo
neanderthalensis.

00:10:03.534 --> 00:10:04.950
I always have
trouble saying this.

00:10:04.950 --> 00:10:08.330
So this is still part of Homo.

00:10:08.330 --> 00:10:10.890
And a common misconception
is that the Neanderthals are

00:10:10.890 --> 00:10:13.405
somehow a more primitive
version of humans,

00:10:13.405 --> 00:10:15.530
that they're somehow cavemen,
and we're modern men.

00:10:15.530 --> 00:10:17.210
That's not the case.

00:10:17.210 --> 00:10:18.960
The belief is that
Neanderthals are either

00:10:18.960 --> 00:10:21.730
cousin species-- we
have a common ancestor--

00:10:21.730 --> 00:10:25.670
or that they're actually a
sub-species of human beings.

00:10:25.670 --> 00:10:27.380
And there's some
belief that they

00:10:27.380 --> 00:10:29.690
might have interbred
with Homo sapiens.

00:10:29.690 --> 00:10:34.900
And maybe some or a good number
of us have a Neanderthal genes.

00:10:34.900 --> 00:10:37.090
And it's nothing
to be ashamed of.

00:10:37.090 --> 00:10:39.260
It's just something,
unfortunately,

00:10:39.260 --> 00:10:43.080
that Neanderthals just get a
bad name, because of, I guess,

00:10:43.080 --> 00:10:44.710
our popular culture.

00:10:44.710 --> 00:10:47.297
So this is a drawing
of a Neanderthal brain.

00:10:47.297 --> 00:10:49.380
They actually had a fairly
large cranial capacity.

00:10:49.380 --> 00:10:52.215
Although scientists, they kind
of make one reason or another

00:10:52.215 --> 00:10:53.590
why we think that
they might have

00:10:53.590 --> 00:10:55.270
been more primitive
than Homo sapiens.

00:10:55.270 --> 00:10:56.040
But who knows?

00:10:56.040 --> 00:10:57.750
We don't know.

00:10:57.750 --> 00:11:00.430
We're constantly learning
things every day.

00:11:00.430 --> 00:11:02.080
But of course, the
whole point of this

00:11:02.080 --> 00:11:05.470
is to talk about how humans
showed up on this planet.

00:11:05.470 --> 00:11:08.480
And the first
really human fossils

00:11:08.480 --> 00:11:12.020
we find about 200,000 years ago.

00:11:12.020 --> 00:11:15.120
And remember, we're
in the genus Homo.

00:11:15.120 --> 00:11:17.920
And now, we've finally found
something that looks just

00:11:17.920 --> 00:11:19.590
like us, anatomically, at least.

00:11:19.590 --> 00:11:21.790
We can't study its
behavior and all the rest.

00:11:21.790 --> 00:11:24.800
And now we get to Homo sapiens.

00:11:24.800 --> 00:11:27.150
The Homo part, once
again, means man.

00:11:27.150 --> 00:11:31.640
And the sapiens means thinking.

00:11:31.640 --> 00:11:34.400
So we can debate whether
it's an appropriate title

00:11:34.400 --> 00:11:36.160
for our species, but
it's "thinking man."

00:11:36.160 --> 00:11:38.800
So once again, the
Neanderthals, they

00:11:38.800 --> 00:11:41.776
were either a cousin species
for a lot of this time,

00:11:41.776 --> 00:11:43.400
especially once Homo
sapiens showed up.

00:11:43.400 --> 00:11:45.440
And maybe Homo sapiens
showed up before this.

00:11:45.440 --> 00:11:47.150
We just haven't found
the fossils yet.

00:11:47.150 --> 00:11:49.440
They were maybe both
inhabiting the same planet.

00:11:49.440 --> 00:11:51.360
Maybe there was
some interbreeding.

00:11:51.360 --> 00:11:54.810
But the Neanderthals disappeared
about 30,000 years ago.

00:11:54.810 --> 00:11:57.550
30,000 years ago,
these guys disappeared.

00:11:57.550 --> 00:11:59.550
Maybe some of them
kind of got mixed

00:11:59.550 --> 00:12:01.000
in with the Homo
sapiens, started

00:12:01.000 --> 00:12:02.020
to interbreed with them.

00:12:02.020 --> 00:12:04.300
Or they might have
just been killed off,

00:12:04.300 --> 00:12:07.910
because they were fighting
over the same ecosystems.

00:12:07.910 --> 00:12:13.230
And I've made a little
sample here of Homo sapiens.

00:12:13.230 --> 00:12:16.000
Well, I'm assuming most of you
watching this video are one.

00:12:16.000 --> 00:12:20.140
But just in case,
here's my little sample.

00:12:20.140 --> 00:12:23.840
We can debate how representative
a sample of our species

00:12:23.840 --> 00:12:25.950
this really is.


US and Japanese Quantitative Easing

WEBVTT
Kind: captions
Language: en

00:00:00.610 --> 00:00:04.290
When Japan faced its own banking
and debt crisis in the 1990s,

00:00:04.290 --> 00:00:05.790
the first thing it
did is it started

00:00:05.790 --> 00:00:09.450
to lower its target
interest rate or the rate

00:00:09.450 --> 00:00:11.880
that banks borrow
reserves from each other.

00:00:11.880 --> 00:00:13.820
And the way to do that
is you print money.

00:00:13.820 --> 00:00:17.300
In the case of Japan, the
central break prints yen.

00:00:17.300 --> 00:00:19.250
It buys short-term
government securities.

00:00:19.250 --> 00:00:22.160
But the byproduct of that
is it increases the amount

00:00:22.160 --> 00:00:25.190
of currency or reserves
in circulation.

00:00:25.190 --> 00:00:27.650
All banks have more reserves.

00:00:27.650 --> 00:00:29.890
So the demand for that
reserves will go down

00:00:29.890 --> 00:00:32.479
or the cost of borrowing
it will go down.

00:00:32.479 --> 00:00:35.050
And so it lowers
the interest rate.

00:00:35.050 --> 00:00:36.910
But Japan did that
enough so that it

00:00:36.910 --> 00:00:38.674
got to a 0% interest rate.

00:00:38.674 --> 00:00:40.840
But then it really couldn't
lower that interest rate

00:00:40.840 --> 00:00:41.340
anymore.

00:00:41.340 --> 00:00:42.990
And that's exactly
what Bernanke is

00:00:42.990 --> 00:00:45.340
faced with the US credit crisis.

00:00:45.340 --> 00:00:47.450
So the next thing
that Japan said is OK,

00:00:47.450 --> 00:00:50.380
we still want more money
to enter into circulation.

00:00:50.380 --> 00:00:54.460
So we're going to keep
printing more yen.

00:00:54.460 --> 00:00:56.340
We're going to keep
printing more yen.

00:00:56.340 --> 00:00:58.650
But since it's
really of no use just

00:00:58.650 --> 00:01:00.299
to buy the short-term
debt anymore

00:01:00.299 --> 00:01:02.840
because we've already kind of
priced those as high as we can.

00:01:02.840 --> 00:01:04.599
We've lowered short-term
interest rates

00:01:04.599 --> 00:01:06.250
as much as possible.

00:01:06.250 --> 00:01:09.070
Let's use this stuff
to buy other things.

00:01:09.070 --> 00:01:10.860
Let's just get this
money into circulation

00:01:10.860 --> 00:01:12.390
any which way we can.

00:01:12.390 --> 00:01:15.790
So let's by long-term
Japanese treasuries.

00:01:15.790 --> 00:01:18.346
Let's buy corporate debt.

00:01:18.346 --> 00:01:19.720
So they did buy
a bunch of stuff,

00:01:19.720 --> 00:01:21.470
but their intention
was literally just

00:01:21.470 --> 00:01:26.890
to increase the
quantity of money.

00:01:26.890 --> 00:01:28.620
So what the Japanese
did was kind

00:01:28.620 --> 00:01:30.860
of pure quantitative easing.

00:01:30.860 --> 00:01:32.760
They were trying to
print money at any cost

00:01:32.760 --> 00:01:35.660
and let that money
go into circulation

00:01:35.660 --> 00:01:37.130
in any which way possible.

00:01:37.130 --> 00:01:39.430
And they would buy a
bunch of stuff to do it.

00:01:39.430 --> 00:01:41.710
What Bernanke's
doing mechanically

00:01:41.710 --> 00:01:44.530
is not that different than
what the Japanese did.

00:01:44.530 --> 00:01:47.452
He started off trying to lower
short-term interest rates so he

00:01:47.452 --> 00:01:48.785
would buy short-term securities.

00:01:48.785 --> 00:01:51.500
It would increase the amount
of reserves in circulation,

00:01:51.500 --> 00:01:53.540
lower the overnight
borrowing rate,

00:01:53.540 --> 00:01:56.030
lower the federal funds rate.

00:01:56.030 --> 00:02:01.050
But when that went to 0%, so
they both hit this floor at 0%,

00:02:01.050 --> 00:02:03.220
Bernanke is like,
well, how do I solve

00:02:03.220 --> 00:02:05.110
the logjam in the
credit markets?

00:02:05.110 --> 00:02:06.980
And Bernanke, just
like Japan, says,

00:02:06.980 --> 00:02:08.919
well, I'm going to start
printing more money

00:02:08.919 --> 00:02:10.960
and I'm going to
use it to buy assets

00:02:10.960 --> 00:02:13.280
that the Fed does not
traditionally buy.

00:02:13.280 --> 00:02:15.920
And Japan did this as well.

00:02:15.920 --> 00:02:18.910
The difference-- and this
is how a Bernanke explains

00:02:18.910 --> 00:02:20.790
the difference-- is
he doesn't view this

00:02:20.790 --> 00:02:23.970
as pure quantitative easing,
not because it's mechanically

00:02:23.970 --> 00:02:26.880
different, because it really
is mechanically the same thing.

00:02:26.880 --> 00:02:28.760
But he calls it credit easing.

00:02:28.760 --> 00:02:31.500
And in his mind, the difference
between quantitative and credit

00:02:31.500 --> 00:02:35.830
easing is the intent and where
you direct that extra money

00:02:35.830 --> 00:02:37.890
that you've printed.

00:02:37.890 --> 00:02:39.886
In Japan's case,
they printed money

00:02:39.886 --> 00:02:41.510
for the sake of
printing money and they

00:02:41.510 --> 00:02:44.210
bought all of this stuff
just to get that money

00:02:44.210 --> 00:02:45.590
into circulation.

00:02:45.590 --> 00:02:48.160
In Bernanke's case,
he is printing money.

00:02:48.160 --> 00:02:50.110
He does want their
money in circulation,

00:02:50.110 --> 00:02:52.800
but that's not the end that
he's trying to achieve.

00:02:52.800 --> 00:02:56.390
The end is to increase
demand for some

00:02:56.390 --> 00:02:59.420
of these types of securities
where maybe there's a logjam.

00:02:59.420 --> 00:03:01.750
So even though mechanically
they're the same,

00:03:01.750 --> 00:03:03.770
Bernanke says this is
credit easing because I'm

00:03:03.770 --> 00:03:06.430
trying to fix a problem in
the commercial debt market,

00:03:06.430 --> 00:03:09.290
or I'm trying to fix the problem
in the mortgage backed security

00:03:09.290 --> 00:03:12.400
market, while Japan was
just trying to print money

00:03:12.400 --> 00:03:15.020
for the sake of printing money.


Another Quantitative Easing Video

WEBVTT
Kind: captions
Language: en

00:00:00.540 --> 00:00:02.270
Let's say the United
States economy

00:00:02.270 --> 00:00:04.440
is going into a
recession or maybe

00:00:04.440 --> 00:00:06.090
even worse than a recession.

00:00:06.090 --> 00:00:08.400
And you are the Chairman
of the Federal Reserve

00:00:08.400 --> 00:00:10.194
and you need to do
something about it.

00:00:10.194 --> 00:00:11.610
Well, the first
thing you would do

00:00:11.610 --> 00:00:14.060
is that you would lower
the federal funds rate.

00:00:14.060 --> 00:00:17.199
And that's the rate that banks
lend to each other overnight.

00:00:17.199 --> 00:00:19.490
And the way that you lower
it, if the banks don't do it

00:00:19.490 --> 00:00:22.190
on their own after you
say you want to lower it,

00:00:22.190 --> 00:00:27.410
is that you print money
as the Federal Reserve.

00:00:27.410 --> 00:00:31.160
And you use it to buy usually
short-term treasury securities.

00:00:31.160 --> 00:00:33.660
And then that money
gets deposited in banks.

00:00:33.660 --> 00:00:35.410
So the demand for
reserves, because that's

00:00:35.410 --> 00:00:38.750
what these things are, the
demand for reserves goes down,

00:00:38.750 --> 00:00:42.620
supply goes up, and the federal
funds rate should go down.

00:00:42.620 --> 00:00:44.560
But what happens if
you keep doing this

00:00:44.560 --> 00:00:47.160
and you keep lowering the
federal funds rate all the way

00:00:47.160 --> 00:00:48.710
down so that the
overnight borrowing

00:00:48.710 --> 00:00:52.080
rate is approximately 0%?

00:00:52.080 --> 00:00:54.570
What do you do then
if the economy still

00:00:54.570 --> 00:00:56.820
looks like it's in
a bit of a tailspin?

00:00:56.820 --> 00:01:00.990
Well you could
still print money,

00:01:00.990 --> 00:01:03.504
but using that money
to buy short-term debt

00:01:03.504 --> 00:01:04.879
won't help any
because you're not

00:01:04.879 --> 00:01:08.460
going to lower the short-term
overnight interbank interest

00:01:08.460 --> 00:01:09.670
rate anymore.

00:01:09.670 --> 00:01:12.670
So you can go out
and buy other things.

00:01:16.310 --> 00:01:22.680
And those other things can
be longer term treasuries

00:01:22.680 --> 00:01:25.790
or it could be other
types of securities.

00:01:25.790 --> 00:01:30.560
You could buy
mortgage-backed securities.

00:01:30.560 --> 00:01:32.620
You could buy commercial debt.

00:01:35.200 --> 00:01:39.540
And this idea of printing money,
not just for target interest

00:01:39.540 --> 00:01:43.050
rate, but essentially, to get
that money into circulation

00:01:43.050 --> 00:01:45.710
and maybe to affect other
parts of the market,

00:01:45.710 --> 00:01:47.765
this is called
quantitative easing.

00:01:51.230 --> 00:01:54.880
And in Bernanke's mind, although
that's exactly what he's doing,

00:01:54.880 --> 00:01:56.807
he's printing money
to buy other things

00:01:56.807 --> 00:01:58.890
than what the Fed traditionally
does when he cares

00:01:58.890 --> 00:02:00.880
about the overnight
borrowing rate,

00:02:00.880 --> 00:02:03.390
he calls it, not necessary
quantitative easing,

00:02:03.390 --> 00:02:04.950
but credit easing.

00:02:04.950 --> 00:02:07.220
And in his mind, even
though mechanically they

00:02:07.220 --> 00:02:09.729
are the same thing, in
his mind, he saying, look,

00:02:09.729 --> 00:02:12.770
I'm printing this money not
just for the sake of printing

00:02:12.770 --> 00:02:14.850
the money and putting
it into circulation,

00:02:14.850 --> 00:02:20.130
I'm printing money so that I
can buy particular assets where

00:02:20.130 --> 00:02:24.210
it seems like there might be a
log jam in the credit markets.

00:02:24.210 --> 00:02:26.470
Because with just printing
money and buying government

00:02:26.470 --> 00:02:29.130
securities, maybe the interest
rates on government debt

00:02:29.130 --> 00:02:32.680
goes down, but maybe
because of panic or crisis,

00:02:32.680 --> 00:02:37.520
interest or the prices on these
things don't behave properly.

00:02:37.520 --> 00:02:42.390
So in order to fix that, credit
easing, in the Bernanke sense,

00:02:42.390 --> 00:02:46.800
would be to go out and
buy this type of asset.


AMT overview

WEBVTT
Kind: captions
Language: en

00:00:00.618 --> 00:00:03.570
Voiceover: Let's say we have
2 people in identical jobs.

00:00:03.570 --> 00:00:05.937
Person A and Person B.

00:00:05.937 --> 00:00:08.604
This past year, they both got paid

00:00:08.604 --> 00:00:10.070
in their identical jobs,

00:00:10.070 --> 00:00:14.710
they got paid $350,000 in salary.

00:00:14.710 --> 00:00:19.473
Now let's assume that
Person A has no deductions.

00:00:19.473 --> 00:00:21.070
They just calculate their taxes,

00:00:21.070 --> 00:00:23.228
and for the sake of simplicity,

00:00:23.228 --> 00:00:24.740
I'm just going to make up a number.

00:00:24.740 --> 00:00:25.939
I'm not going to go through all of it,

00:00:25.939 --> 00:00:28.405
especially because the tax
code changes every year.

00:00:28.405 --> 00:00:33.072
Let's just say their
regular taxes are $150,000.

00:00:33.072 --> 00:00:37.866
150,000 in regular taxes.

00:00:37.866 --> 00:00:40.609
Regular taxes, when you just file taxes,

00:00:40.609 --> 00:00:43.959
not the straightforward,
but just the regular way.

00:00:43.959 --> 00:00:45.736
Let's say Person B, on the other hand,

00:00:45.736 --> 00:00:47.551
even though they have the exact same job,

00:00:47.551 --> 00:00:49.216
they donate a bunch to charity;

00:00:49.216 --> 00:00:50.743
they have all of these deductions;

00:00:50.743 --> 00:00:51.806
they have all of these things

00:00:51.806 --> 00:00:53.805
that they can write off from their income,

00:00:53.805 --> 00:00:56.807
and so Person B's taxable income,

00:00:56.807 --> 00:00:59.070
let's say that it goes down,

00:00:59.070 --> 00:01:00.739
with all of these deductions,

00:01:00.739 --> 00:01:05.067
the taxable income goes down to $200,000.

00:01:05.067 --> 00:01:08.629
On that taxable income of $200,000,

00:01:08.629 --> 00:01:14.267
Person B has to pay
$70,000 in regular taxes.

00:01:14.267 --> 00:01:16.136
Once again, I'm just
making up simple numbers,

00:01:16.136 --> 00:01:18.635
just for the sake of simplicity.

00:01:18.635 --> 00:01:19.626
I'm just actually figuring out

00:01:19.626 --> 00:01:22.134
exactly what Person B's taxes are.

00:01:22.134 --> 00:01:24.805
70,000 in regular taxes.

00:01:24.805 --> 00:01:27.475
Now, the US government, or the IRS, says,

00:01:27.475 --> 00:01:29.805
"Hey, look; Person B
actually made a lot of money;

00:01:29.805 --> 00:01:31.815
"made a similar amount
of money to Person A;

00:01:31.815 --> 00:01:33.209
"they did all of these deductions;

00:01:33.209 --> 00:01:37.137
"allowed them to pay a lot less in taxes.

00:01:37.137 --> 00:01:38.741
"We don't necessarily like that.

00:01:38.741 --> 00:01:40.297
"This person's making a lot of money.

00:01:40.297 --> 00:01:41.964
"We think that they should

00:01:41.964 --> 00:01:45.540
"pay some alternative minimum tax."

00:01:45.540 --> 00:01:48.397
The way that's calculated
is, for either party,

00:01:48.397 --> 00:01:51.471
there's this completely separate tax code.

00:01:51.471 --> 00:01:55.268
So, Alternative Minimum Tax.

00:01:55.268 --> 00:01:57.629
You calculate your regular taxes,

00:01:57.629 --> 00:01:59.675
so that's this number and this number,

00:01:59.675 --> 00:02:01.934
and then in parallel you calculate

00:02:01.934 --> 00:02:04.001
an alternative minimum tax,

00:02:04.001 --> 00:02:06.071
and in the case of either of these people,

00:02:06.071 --> 00:02:07.527
what happens is you don't get

00:02:07.527 --> 00:02:09.935
most of these deductions right here.

00:02:09.935 --> 00:02:11.684
That's really done, basically,

00:02:11.684 --> 00:02:13.104
for simplicity purposes,

00:02:13.104 --> 00:02:17.011
on your gross income,

00:02:17.011 --> 00:02:19.677
and it's a much simpler tax code.

00:02:19.677 --> 00:02:21.603
It's almost a flat tax.

00:02:21.603 --> 00:02:26.429
At the $350,000 level, you
get no standard deduction,

00:02:26.429 --> 00:02:29.476
and it's really, it's 26% right now,

00:02:29.476 --> 00:02:32.267
on the first 175,000,

00:02:32.267 --> 00:02:36.141
and then it is 28% on the next 175,000,

00:02:36.141 --> 00:02:37.680
if you're making this much money.

00:02:37.680 --> 00:02:40.603
You have a deduction if
you make less than that,

00:02:40.603 --> 00:02:42.684
and all the rest; I won't
go into the details,

00:02:42.684 --> 00:02:44.733
but the general idea is you calculate this

00:02:44.733 --> 00:02:47.429
for either party, and in either situation,

00:02:47.429 --> 00:02:49.350
the alternative minimum tax

00:02:49.350 --> 00:02:51.019
for either of these people

00:02:51.019 --> 00:02:54.806
is going to be $94,500.

00:02:54.806 --> 00:02:57.850
$94,500.

00:02:57.850 --> 00:03:00.765
This guy, Person A,
will calculate his AMT.

00:03:00.765 --> 00:03:02.678
He gets $94,500.

00:03:02.678 --> 00:03:05.541
He's like, "Well, my
regular taxes are $150,000,

00:03:05.541 --> 00:03:07.676
"so I pay the higher of the 2."

00:03:07.676 --> 00:03:09.516
He pays his regular taxes.

00:03:09.516 --> 00:03:11.469
This is just done, just to make sure

00:03:11.469 --> 00:03:13.271
that his AMT isn't higher.

00:03:13.271 --> 00:03:14.934
Person B, on the other hand,

00:03:14.934 --> 00:03:17.432
his regular taxes, after
all of this deductions,

00:03:17.432 --> 00:03:22.185
came out to $70,000, so
he has to pay the AMT,

00:03:22.185 --> 00:03:25.350
because the AMT is higher
than his regular taxes,

00:03:25.350 --> 00:03:27.016
so this is what he pays.

00:03:27.016 --> 00:03:29.544
The general idea, you
compute your regular taxes;

00:03:29.544 --> 00:03:32.743
you compute the AMT; 2 separate tax codes;

00:03:32.743 --> 00:03:34.933
you pay the higher of the 2,

00:03:34.933 --> 00:03:36.269
and the whole idea of this

00:03:36.269 --> 00:03:38.600
is to make sure that people
who have a certain income

00:03:38.600 --> 00:03:40.539
aren't able to deduct it all away,

00:03:40.539 --> 00:03:43.802
and pay a very, very low income tax.


Open market operations and Quantitative Easing Overview

WEBVTT
Kind: captions
Language: en

00:00:00.670 --> 00:00:06.870
When the Federal Reserve
does traditional open-market

00:00:06.870 --> 00:00:11.280
operations, what they
do is the Fed over here

00:00:11.280 --> 00:00:14.180
will literally print money.

00:00:14.180 --> 00:00:16.630
So it prints money.

00:00:16.630 --> 00:00:18.340
It doesn't necessarily
have to be cash,

00:00:18.340 --> 00:00:20.010
it could be electronic money.

00:00:20.010 --> 00:00:24.750
And it uses that money to buy
usually short-term treasury

00:00:24.750 --> 00:00:26.990
securities in the open market.

00:00:26.990 --> 00:00:29.740
That's why it's called
open market operations.

00:00:29.740 --> 00:00:32.419
So in exchange it gets
treasury securities.

00:00:35.460 --> 00:00:37.350
Now, the whole
purpose of this, it

00:00:37.350 --> 00:00:39.670
does increase the
demand for treasuries,

00:00:39.670 --> 00:00:42.070
and, therefore, increases
the price on treasuries

00:00:42.070 --> 00:00:43.680
and lower the interest rate.

00:00:43.680 --> 00:00:46.500
But the main point is it
takes this printed money,

00:00:46.500 --> 00:00:48.520
and it puts it in
the banking system.

00:00:48.520 --> 00:00:51.510
Because it buys treasuries just
from people, or from banks,

00:00:51.510 --> 00:00:54.010
or institutions, and then
those people take that cash,

00:00:54.010 --> 00:00:56.390
that they just got
for these treasuries,

00:00:56.390 --> 00:00:58.840
and they'll deposit it in banks.

00:00:58.840 --> 00:01:01.890
So they'll go and they'll
deposit it in, maybe,

00:01:01.890 --> 00:01:06.140
Bank 1 over here, then
over here in Bank 2.

00:01:06.140 --> 00:01:09.520
And since there's more
money in Bank 1 and Bank 2,

00:01:09.520 --> 00:01:14.420
you have the supply
of money going up,

00:01:14.420 --> 00:01:17.110
and also the demand for
reserves is going up.

00:01:17.110 --> 00:01:19.420
This cash right here,
these are reserves.

00:01:22.780 --> 00:01:25.119
So you have the demand
for reserves going down.

00:01:25.119 --> 00:01:26.910
Maybe before this money
entered the system,

00:01:26.910 --> 00:01:29.260
maybe Bank 2 is running
low on reserves.

00:01:29.260 --> 00:01:31.770
But now people have
deposited money in Bank 2,

00:01:31.770 --> 00:01:34.130
so Bank 2 doesn't
need it as much.

00:01:34.130 --> 00:01:36.360
And if you have the
supply of money going up,

00:01:36.360 --> 00:01:38.390
you have the demand
for money going down--

00:01:38.390 --> 00:01:40.590
where in particular I'm
talking about reserves.

00:01:40.590 --> 00:01:43.180
I'm talking about
base-money right over here--

00:01:43.180 --> 00:01:46.000
then the overnight
borrowing rate between banks

00:01:46.000 --> 00:01:47.350
will go down.

00:01:47.350 --> 00:01:49.360
The price of money will go down.

00:01:49.360 --> 00:01:51.400
And that's what the
federal funds rate is.

00:01:51.400 --> 00:01:52.800
It's the target rate.

00:01:52.800 --> 00:01:56.690
So I'll say fed funds rate.

00:01:56.690 --> 00:01:58.850
It's the target
rate that the Fed

00:01:58.850 --> 00:02:02.800
sets for the overnight borrowing
of reserves between banks.

00:02:02.800 --> 00:02:04.990
That's the federal funds
rate, and it will go down.

00:02:04.990 --> 00:02:08.570
And that's how the Fed tries
to set the federal funds rate.

00:02:08.570 --> 00:02:12.350
Now, fast forward to a
situation like we are right now.

00:02:12.350 --> 00:02:15.570
And the federal funds
rate is already at 0,

00:02:15.570 --> 00:02:19.690
but the Fed still wants to pump
more money into the economy

00:02:19.690 --> 00:02:22.520
and it wants to do it
in a more directed way.

00:02:22.520 --> 00:02:25.210
So now what it's doing,
it's still printing money,

00:02:25.210 --> 00:02:28.160
but it's using that money
to buy other things.

00:02:28.160 --> 00:02:30.490
It could buy longer-term debt.

00:02:30.490 --> 00:02:34.220
So it could buy longer
duration treasuries.

00:02:34.220 --> 00:02:36.290
So things that are
maybe going to,

00:02:36.290 --> 00:02:40.200
maybe 10-year treasury bonds,
or further out than even that.

00:02:40.200 --> 00:02:43.150
Or it could even buy
completely different assets.

00:02:43.150 --> 00:02:47.820
It could maybe buy
mortgage backed securities.

00:02:47.820 --> 00:02:51.520
And the point here isn't just
to increase the money supply.

00:02:51.520 --> 00:02:54.340
The point in quantitative
easing is, maybe,

00:02:54.340 --> 00:02:57.230
to kind of smooth
over what's happening

00:02:57.230 --> 00:02:58.660
in certain parts of the market.

00:02:58.660 --> 00:03:01.201
So if they think that there's
a logjam in the mortgage backed

00:03:01.201 --> 00:03:03.980
security market, that's why
they're participating there.

00:03:03.980 --> 00:03:09.996
So this right over here,
that is quantitative easing.


Salman Khan on Marketplace (NPR) on 5-24-2011

WEBVTT
Kind: captions
Language: en

00:00:00.147 --> 00:00:01.680
(music)

00:00:01.680 --> 00:00:02.955
Voiceover: It's pretty
rare to have a conversation

00:00:02.955 --> 00:00:05.278
about education policy in which the word

00:00:05.278 --> 00:00:07.629
"technology" isn't used at some point.

00:00:07.629 --> 00:00:09.750
Occasionally, in the administrative sense,

00:00:09.750 --> 00:00:11.453
as a way to make education more efficient;

00:00:11.453 --> 00:00:14.275
but mostly in the classroom
sense, helping kids learn.

00:00:14.275 --> 00:00:16.551
Which gets us to Salman Khan.

00:00:16.551 --> 00:00:19.280
He's a former hedge fund
manager turned educator

00:00:19.280 --> 00:00:21.360
as the founder and sole faculty member

00:00:21.360 --> 00:00:22.650
of the Khan Academy.

00:00:22.650 --> 00:00:24.550
It started as a tutoring service

00:00:24.550 --> 00:00:26.198
for his cousins on YouTube.

00:00:26.198 --> 00:00:27.650
It's become a library of thousands

00:00:27.650 --> 00:00:29.360
of instructional videos on topics

00:00:29.360 --> 00:00:31.865
from basic arithmetic to organic chemistry

00:00:31.865 --> 00:00:32.851
to the French Revolution

00:00:32.851 --> 00:00:34.357
with financial backing from,

00:00:34.357 --> 00:00:36.440
among others, the Gates Foundation.

00:00:36.440 --> 00:00:38.181
Sal Kahn, good to have you with us.

00:00:38.181 --> 00:00:39.322
Sal: Great to be here.

00:00:39.322 --> 00:00:41.442
Voiceover: How, exactly, did you wind up

00:00:41.442 --> 00:00:42.740
putting videos on YouTube?

00:00:42.740 --> 00:00:44.638
Sal: I was a little
dismissive of it at first.

00:00:44.638 --> 00:00:46.852
I didn't think YouTube was
for serious mathematics.

00:00:46.852 --> 00:00:48.764
I thought it was more
for dogs on skateboards

00:00:48.764 --> 00:00:51.642
or whatever else, but I
decided to give it a shot

00:00:51.642 --> 00:00:53.765
and people all over the
world started watching them.

00:00:53.765 --> 00:00:55.266
Some of them would say,

00:00:55.266 --> 00:00:56.540
"Hey, this helped me on an exam."

00:00:56.540 --> 00:00:57.194
But some of them would say,

00:00:57.194 --> 00:00:59.058
"Hey, this helped me not
drop out of high school"

00:00:59.058 --> 00:01:00.923
or "This helped me get into the school

00:01:00.923 --> 00:01:02.143
"that I wanted to get into,"

00:01:02.143 --> 00:01:04.730
so it became a pretty
exciting thing to work on.

00:01:04.730 --> 00:01:06.419
Voiceover: What's the
education problem, though,

00:01:06.419 --> 00:01:08.227
that you think this technology can solve?

00:01:08.227 --> 00:01:11.029
Sal: It's a pretty
straightforward problem,

00:01:11.029 --> 00:01:13.732
is that everyone learns at different paces

00:01:13.732 --> 00:01:17.030
and right now everyone's
forced to go at the same pace.

00:01:17.030 --> 00:01:19.148
It's a more serious
problem than just people

00:01:19.148 --> 00:01:21.649
being bored or people being
lost in one classroom.

00:01:21.649 --> 00:01:23.330
What happens when everyone
moves at the same pace is,

00:01:23.330 --> 00:01:26.065
you and and I are in the
exam or we're learning

00:01:26.065 --> 00:01:29.062
a basic subject; I don't
get 5% of the subject,

00:01:29.062 --> 00:01:30.730
you don't get 20% of the subject,

00:01:30.730 --> 00:01:33.028
the whole class moves on
to a more advanced subject.

00:01:33.028 --> 00:01:35.730
I have a 5% gap, you have a 20% gap.

00:01:35.730 --> 00:01:38.141
Those gaps build up over time.

00:01:38.141 --> 00:01:40.483
It pretty much guarantees
that most students,

00:01:40.483 --> 00:01:41.928
by the time they get
to algebra or calculus,

00:01:41.928 --> 00:01:42.928
have so many of these gaps

00:01:42.928 --> 00:01:44.230
that no matter how hard they try,

00:01:44.230 --> 00:01:46.429
they just can't understand
what's going on.

00:01:46.429 --> 00:01:47.983
What we're trying to address

00:01:47.983 --> 00:01:49.646
is every student can go at their own pace,

00:01:49.646 --> 00:01:52.647
make sure that they master
something before moving on.

00:01:52.647 --> 00:01:55.923
When you do that, then
those gaps shouldn't happen.

00:01:55.923 --> 00:01:58.060
Voiceover: It's an
accumulation of failure, right?

00:01:58.060 --> 00:01:58.830
Isn't that your phrase?

00:01:58.830 --> 00:02:00.830
Sal: Yeah, I would say it's
an accumulation of gaps.

00:02:00.830 --> 00:02:03.329
The failure thing is
another interesting ...

00:02:03.329 --> 00:02:06.148
Right now, when you take
an assessment, a test,

00:02:06.148 --> 00:02:08.058
in school, you get a label.

00:02:08.058 --> 00:02:09.642
You get an A, B or C or D.

00:02:09.642 --> 00:02:11.229
The A kids kind of feel
good about themselves,

00:02:11.229 --> 00:02:12.230
they get self confidence.

00:02:12.230 --> 00:02:13.734
B students are a little bit neutral.

00:02:13.734 --> 00:02:16.145
You get a C, D or F,
it's not viewed as, hey,

00:02:16.145 --> 00:02:17.481
you didn't understand 30%.

00:02:17.481 --> 00:02:19.522
Why don't you go and try to
learn it a little bit better?

00:02:19.522 --> 00:02:21.029
It's viewed as you're not so smart.

00:02:21.029 --> 00:02:23.111
Don't try to become an
engineer or a physicist.

00:02:23.111 --> 00:02:24.728
Voiceover: Where do you fit in, though?

00:02:24.728 --> 00:02:26.531
Where does Khan Academy
fit in in the larger

00:02:26.531 --> 00:02:28.647
application of technology to education?

00:02:28.647 --> 00:02:29.645
How do you slide in there?

00:02:29.645 --> 00:02:31.329
Sal: For a while, whenever people talk

00:02:31.329 --> 00:02:32.431
about technology in education

00:02:32.431 --> 00:02:34.063
they've just been talking about putting

00:02:34.063 --> 00:02:36.231
computers or iPads or whatever in a room

00:02:36.231 --> 00:02:37.930
and hoping something good happens.

00:02:37.930 --> 00:02:40.065
Even when there was something
to do on a computer,

00:02:40.065 --> 00:02:42.731
it was always viewed as separate
from the core curriculum.

00:02:42.731 --> 00:02:44.230
It was viewed separate of what normally

00:02:44.230 --> 00:02:45.229
goes on in a math class.

00:02:45.229 --> 00:02:47.563
What we're saying is now we
can actually use technology,

00:02:47.563 --> 00:02:49.566
we can use these videos,
we can use this software,

00:02:49.566 --> 00:02:51.977
to allow every student to
work at their own pace.

00:02:51.977 --> 00:02:54.142
It's not an either/or proposition anymore.

00:02:54.142 --> 00:02:55.642
There's always this debate

00:02:55.642 --> 00:02:57.481
of do you do more of the core skills

00:02:57.481 --> 00:02:59.647
or do more of the projects
and the investigations?

00:02:59.647 --> 00:03:01.329
We're saying that you can do both.

00:03:01.329 --> 00:03:02.729
You can use the technology to handle

00:03:02.729 --> 00:03:04.628
a lot of the core skills, free up a lot

00:03:04.628 --> 00:03:06.832
of the teacher's time to do
more of the human interactions.

00:03:06.832 --> 00:03:10.828
Voiceover: For the price
of a login, right ...

00:03:10.828 --> 00:03:12.428
You either login through
Facebook or Google,

00:03:12.428 --> 00:03:14.149
you get access to all these things.

00:03:14.149 --> 00:03:15.645
Is there a thought in your mind

00:03:15.645 --> 00:03:17.729
of somehow making people pay for this?

00:03:17.729 --> 00:03:19.981
Sal: We want to at some
point be sustainable

00:03:19.981 --> 00:03:22.065
as a not-for-profit, but we
want all of this material

00:03:22.065 --> 00:03:24.431
to be 100% accessible by everyone.

00:03:24.431 --> 00:03:28.430
On the web and our core
tools will always be free.

00:03:28.430 --> 00:03:30.647
Right now, nothing on
our radar is non free,

00:03:30.647 --> 00:03:31.628
I guess is the simple answer.

00:03:31.628 --> 00:03:33.231
Voiceover: What's the next
step for the Khan Academy?

00:03:33.231 --> 00:03:35.227
Sal: Right now, we have
about 2 million students

00:03:35.227 --> 00:03:37.029
a month who use our
site on a regular basis.

00:03:37.029 --> 00:03:38.830
We want to start leveraging them

00:03:38.830 --> 00:03:40.027
so that they can help each other.

00:03:40.027 --> 00:03:41.397
If you're in a classroom,

00:03:41.397 --> 00:03:43.032
your teacher knows that you need help;

00:03:43.032 --> 00:03:44.149
but if you're not in a classroom

00:03:44.149 --> 00:03:45.731
or you need a supplement to a classroom,

00:03:45.731 --> 00:03:47.428
maybe one of the other community members

00:03:47.428 --> 00:03:49.728
of the Khan Academy can tutor you

00:03:49.728 --> 00:03:51.478
or help you out or get
you passed your hurdle.

00:03:51.478 --> 00:03:53.328
Voiceover: Salman Khan.

00:03:53.328 --> 00:03:55.061
He's the founder of the Khan Academy.

00:03:55.061 --> 00:03:56.029
Thanks a lot.

00:03:56.029 --> 00:03:59.000
Sal: Great, thanks.


Detectable civilizations in our galaxy 5

WEBVTT
Kind: captions
Language: en

00:00:00.600 --> 00:00:02.846
In the last video on the Drake equation

00:00:02.846 --> 00:00:04.625
we tried out some numbers

00:00:04.625 --> 00:00:05.929
we just made some assumptions

00:00:05.929 --> 00:00:07.785
that seemed reasonable at least to me

00:00:07.785 --> 00:00:10.805
and we got that there should be 12.5

00:00:10.805 --> 00:00:14.569
detectable civilizations in the Milky Way Galaxy

00:00:14.569 --> 00:00:16.098
and I've talked about a bunch of reasons

00:00:16.098 --> 00:00:18.267
about why we are not detecting them

00:00:18.267 --> 00:00:20.846
but I left out one of the most obvious reasons

00:00:20.846 --> 00:00:21.836
that we are not detecting them

00:00:21.836 --> 00:00:24.123
and it was rightfully pointed out in the comments

00:00:24.123 --> 00:00:25.523
below that video

00:00:25.523 --> 00:00:27.790
and thats just the signal might be too weak

00:00:27.790 --> 00:00:29.144
if theres 12.5

00:00:29.144 --> 00:00:34.129
if there's on the order of 10, 11, 12 detectable

00:00:34.129 --> 00:00:35.713
civilizations in our galaxy

00:00:35.713 --> 00:00:37.667
they could be quite far from us

00:00:37.667 --> 00:00:39.056
this isn't the Milky Way

00:00:39.056 --> 00:00:40.964
but this is a galaxy that probably doesn't look

00:00:40.964 --> 00:00:42.379
too different from our Milky Way

00:00:42.379 --> 00:00:44.652
we could obviously never get this vantage point

00:00:44.652 --> 00:00:46.179
of our galaxy

00:00:46.179 --> 00:00:47.764
well at least not for a while

00:00:47.764 --> 00:00:50.052
not unless we can travel quite far away from it

00:00:50.052 --> 00:00:52.313
but lets say we are over here

00:00:52.313 --> 00:00:55.277
you could imagine if the ten civilizations

00:00:55.277 --> 00:00:57.333
or the twelve civilizations are

00:00:57.333 --> 00:01:01.087
here, one, two, three, four

00:01:01.087 --> 00:01:02.738
there's probably a lot more at the center actually

00:01:02.738 --> 00:01:04.975
because that's where our density is higher

00:01:04.975 --> 00:01:05.969
so let me put it here

00:01:05.969 --> 00:01:10.585
so one, two, three, four, five, six, seven

00:01:10.585 --> 00:01:14.267
eight, nine, ten, eleven, twelve

00:01:14.267 --> 00:01:16.795
the closest of them might be

00:01:16.795 --> 00:01:19.877
tens of thousands of light years away from us

00:01:19.877 --> 00:01:21.779
and there might be a lot of stuff in between

00:01:21.779 --> 00:01:23.559
all sorts of crazy things happening

00:01:23.559 --> 00:01:25.267
stars exploding

00:01:25.267 --> 00:01:27.036
all sorts of signals that we are receiving

00:01:27.036 --> 00:01:27.867
and it might just be

00:01:27.867 --> 00:01:29.754
that the signals from those civilizations

00:01:29.754 --> 00:01:31.775
are too weak to reach us

00:01:31.775 --> 00:01:34.862
or that there is too much interference

00:01:34.862 --> 00:01:36.098
from all of the other craziness

00:01:36.098 --> 00:01:37.944
that's happening around the galaxy

00:01:37.944 --> 00:01:39.118
there's also these other reasons

00:01:39.118 --> 00:01:40.585
that I've talked about in the last video

00:01:40.585 --> 00:01:42.477
maybe they've gone beyond

00:01:42.477 --> 00:01:45.979
using radio as a form of communication

00:01:45.979 --> 00:01:47.462
and thats why..

00:01:47.462 --> 00:01:49.148
or they never used it to begin with

00:01:49.148 --> 00:01:50.569
and that's why we don't even see them

00:01:50.569 --> 00:01:51.579
ever using it

00:01:51.579 --> 00:01:53.354
or they used if for a very short period

00:01:53.354 --> 00:01:54.600
a kind of transition period

00:01:54.600 --> 00:01:57.646
and maybe in a hundred years we'll discover the next best thing

00:01:57.646 --> 00:02:02.748
the other idea behind why we're probably

00:02:02.748 --> 00:02:06.338
or maybe why we might not be able to detect civilizations

00:02:06.338 --> 00:02:07.082
is that

00:02:07.082 --> 00:02:09.436
well there might be a lot fewer than ten

00:02:09.436 --> 00:02:11.908
when I did the Drake equation right over here

00:02:11.908 --> 00:02:13.333
I just made a bunch of assumptions

00:02:13.333 --> 00:02:14.354
none of these seemed crazy

00:02:14.354 --> 00:02:18.200
but I assumed a reality

00:02:18.200 --> 00:02:22.000
where you didn't have these kind of cataclysmic events

00:02:22.000 --> 00:02:26.431
in the galaxy at regular intervals

00:02:26.431 --> 00:02:28.692
but we know there are cataclysmic events

00:02:28.692 --> 00:02:30.785
that happen in our galaxy

00:02:30.785 --> 00:02:32.015
in other galaxies

00:02:32.015 --> 00:02:33.979
the one we know the most about

00:02:33.979 --> 00:02:35.867
although there are all sorts of things that we

00:02:35.867 --> 00:02:36.918
don't know much about

00:02:36.918 --> 00:02:38.267
are gamma ray bursts

00:02:38.267 --> 00:02:41.179
and these are still kind of trying to be understood

00:02:41.179 --> 00:02:46.236
GAMMA RAY BURSTS

00:02:46.236 --> 00:02:48.005
and you can watch the video on quasars

00:02:48.005 --> 00:02:52.010
those are essentially of highly energetic rays

00:02:52.010 --> 00:02:54.098
being released when all this material

00:02:54.098 --> 00:02:58.508
is being kind of absorbed into super massive black holes

00:02:58.523 --> 00:02:59.985
at the centers of galaxies

00:02:59.985 --> 00:03:03.267
that tend to be very very very often

00:03:03.267 --> 00:03:04.492
billions of light years away

00:03:04.492 --> 00:03:07.538
and gamma rays are one of the things that get emitted from those

00:03:07.569 --> 00:03:10.856
but you can also have gamma ray bursts within galaxies

00:03:10.856 --> 00:03:14.308
we believe maybe certain types of stars when they collapse

00:03:14.308 --> 00:03:15.877
into black holes

00:03:15.877 --> 00:03:17.477
you have this burst of gamma rays

00:03:17.477 --> 00:03:20.144
there might be certain kinds of neutron stars

00:03:20.144 --> 00:03:22.596
with the right properties that might every now and then

00:03:22.596 --> 00:03:23.729
release gamma rays

00:03:23.729 --> 00:03:25.267
and the view is

00:03:25.267 --> 00:03:28.246
is that if there is a civilization

00:03:28.246 --> 00:03:31.575
that is within a few thousand light years

00:03:31.575 --> 00:03:35.733
near one of these gamma ray bursts

00:03:35.733 --> 00:03:36.713
and its in wrong place

00:03:36.713 --> 00:03:38.554
its kind of in the path of the burst

00:03:38.554 --> 00:03:42.231
then its a good chance that those civilizations will

00:03:42.231 --> 00:03:43.646
be completely wiped out

00:03:43.646 --> 00:03:45.471
that those planets will become sterilized

00:03:45.471 --> 00:03:47.692
because there is so much radiation

00:03:47.692 --> 00:03:49.487
coming out from that gamma ray

00:03:49.487 --> 00:03:51.302
there's even some theories

00:03:51.302 --> 00:03:55.005
that some of the extinction events that have happened in Earth's history

00:03:55.005 --> 00:03:56.769
we are not talking about the dinosaurs

00:03:56.769 --> 00:03:58.415
we are talking about billions of years ago

00:03:58.415 --> 00:03:59.523
maybe a billion years ago

00:03:59.523 --> 00:04:00.662
or two billion years ago

00:04:00.662 --> 00:04:02.964
that these might have been caused by

00:04:02.964 --> 00:04:05.744
relatively local gamma ray bursts

00:04:05.744 --> 00:04:08.169
the theory is that these might hit earth

00:04:08.169 --> 00:04:10.698
on the order of once every billion years

00:04:10.698 --> 00:04:13.800
and if you think about the galaxy as a whole

00:04:13.800 --> 00:04:15.333
we're kind of in..

00:04:15.333 --> 00:04:19.077
our solar system is orbiting the galaxy

00:04:19.077 --> 00:04:21.795
its kind of a nice distance from the center of the galaxy

00:04:21.795 --> 00:04:23.513
the closer you get into the center

00:04:23.513 --> 00:04:25.729
the higher densities of stars you have

00:04:25.729 --> 00:04:28.959
so you can imagine if earth gets hit with

00:04:28.959 --> 00:04:30.200
one of these gamma rays bursts

00:04:30.200 --> 00:04:32.769
every couple of billion years

00:04:32.769 --> 00:04:35.569
you can imagine something closer the center of the galaxy

00:04:35.569 --> 00:04:38.329
gets hit with these gamma ray bursts

00:04:38.329 --> 00:04:40.200
much much much more frequently

00:04:40.200 --> 00:04:41.867
just because there is more activity there

00:04:41.867 --> 00:04:43.621
there are more stars that are closer by

00:04:43.621 --> 00:04:44.964
more stars that are aging

00:04:44.964 --> 00:04:47.308
more stars that might be collapsing into black holes

00:04:47.308 --> 00:04:50.221
so the simple answer is we don't know

00:04:50.221 --> 00:04:53.077
there could be a thousand civilizations out there

00:04:53.077 --> 00:04:55.810
and we're not sophisticated enough to notice them just yet

00:04:55.810 --> 00:04:57.733
or there might be very very few

00:04:57.733 --> 00:04:59.871
because all of this craziness that happens

00:04:59.871 --> 00:05:01.554
in the galaxy

00:05:01.554 --> 00:05:03.359
or who knows there might be none

00:05:03.359 --> 00:05:04.795
although I find that kind of...

00:05:04.795 --> 00:05:06.502
that's not too exciting

00:05:06.502 --> 99:59:59.999
so I try not to think about that one


Dependent probability example 2

WEBVTT
Kind: captions
Language: en

00:00:00.680 --> 00:00:04.070
Let's do another one of these
dependent probability problems.

00:00:04.070 --> 00:00:06.670
You have 4 coins in a bag.

00:00:06.670 --> 00:00:09.460
3 of them are
unfair in that they

00:00:09.460 --> 00:00:14.440
have a 45% chance of coming
up tails when flipped.

00:00:14.440 --> 00:00:15.640
The rest are fair.

00:00:15.640 --> 00:00:18.640
So for the rest of them, you
have a 50% chance of tails

00:00:18.640 --> 00:00:20.910
or a 50% chance of heads.

00:00:20.910 --> 00:00:23.860
You randomly choose
one coin from the bag

00:00:23.860 --> 00:00:26.310
and flip it 4 times.

00:00:26.310 --> 00:00:30.720
What is the percent
probability of getting 4 heads?

00:00:30.720 --> 00:00:32.189
So let's think about it.

00:00:32.189 --> 00:00:36.150
When we put our hand in the bag
and we take one of the coins

00:00:36.150 --> 00:00:40.430
out, there's some probability
that we get an unfair coin.

00:00:40.430 --> 00:00:43.240
And 3 of the 4 coins are unfair.

00:00:43.240 --> 00:00:50.080
So there's a 3/4 probability
that we get an unfair coin.

00:00:50.080 --> 00:00:53.230
And then there is only 1 out
of the 4 coins that's fair.

00:00:53.230 --> 00:00:58.995
So there was a 1/4 probability
that I get a fair coin.

00:01:02.240 --> 00:01:03.780
So unfair, let's
remind ourselves--

00:01:03.780 --> 00:01:08.290
an unfair coin has a 45%
chance of coming up tails.

00:01:08.290 --> 00:01:13.580
So this means that I have a
45% chance of tails, which also

00:01:13.580 --> 00:01:15.220
means-- and we have
to be careful here

00:01:15.220 --> 00:01:17.520
because they're asking us
about heads-- if I have

00:01:17.520 --> 00:01:19.580
a 45% chance of
getting tails, that

00:01:19.580 --> 00:01:24.929
means I have a 55%
chance of getting heads.

00:01:24.929 --> 00:01:26.970
I have a 100% chance of
getting one of these two.

00:01:26.970 --> 00:01:31.740
If it's 45% for tails, 100
minus 45 is 55 for heads.

00:01:31.740 --> 00:01:35.430
For the fair coin, I have
a 50% chance of tails

00:01:35.430 --> 00:01:38.600
and a 50% chance of heads.

00:01:38.600 --> 00:01:41.340
50% heads.

00:01:41.340 --> 00:01:42.400
Fair enough.

00:01:42.400 --> 00:01:44.580
Now I want to know, in
either of these scenarios,

00:01:44.580 --> 00:01:48.170
what is the percent probability
of getting four heads?

00:01:48.170 --> 00:01:52.540
So given I've got
the unfair coin,

00:01:52.540 --> 00:01:54.420
the probability of
getting four heads

00:01:54.420 --> 00:01:57.580
is going to be 55% for
each of those flips.

00:01:57.580 --> 00:01:59.610
So the probability of
getting exactly four heads

00:01:59.610 --> 00:02:10.860
is going to be 0.55 times
0.55 times 0.55 times 0.55.

00:02:10.860 --> 00:02:14.410
And so the probability
of picking an unfair coin

00:02:14.410 --> 00:02:18.300
and getting four
heads in a row is

00:02:18.300 --> 00:02:22.130
going to be equal to 3/4 times
all of this business over here.

00:02:22.130 --> 00:02:27.230
So that's 3/4 times--
and this is 0.55 times

00:02:27.230 --> 00:02:32.274
itself four times, so I
could write it as 0.55

00:02:32.274 --> 00:02:35.070
to the fourth power.

00:02:35.070 --> 00:02:37.500
And we'll get the
calculator out in a second

00:02:37.500 --> 00:02:40.020
to actually calculate
what this is.

00:02:40.020 --> 00:02:42.090
Now let's do the same
thing for the fair coin.

00:02:42.090 --> 00:02:44.370
If I did pick a fair
coin, the probability

00:02:44.370 --> 00:02:49.650
of getting heads four times in
a row is going to be 0.5 times

00:02:49.650 --> 00:02:55.130
0.5 times 0.5 times 0.5.

00:02:55.130 --> 00:02:58.110
Or the probability of
getting the fair coin, which

00:02:58.110 --> 00:03:02.050
is 1/4 chance, times
the probability--

00:03:02.050 --> 00:03:06.150
and getting four heads in a
row is going to be 1/4 times

00:03:06.150 --> 00:03:06.710
all of this.

00:03:06.710 --> 00:03:11.850
So it's going to be 1/4 times--
this is just 0.5 times itself

00:03:11.850 --> 00:03:16.297
four times, so that's
0.5 to the fourth power.

00:03:16.297 --> 00:03:18.130
So let's get the
calculator out to calculate

00:03:18.130 --> 00:03:20.210
either one of these.

00:03:20.210 --> 00:03:28.520
So we get 3 divided
by 4 times-- and it

00:03:28.520 --> 00:03:30.390
knows that when I do
the multiplication,

00:03:30.390 --> 00:03:32.320
it's not in the
denominator here.

00:03:32.320 --> 00:03:34.809
So it's 3/4 times-- and I'll
just do it in parentheses,

00:03:34.809 --> 00:03:36.600
which I don't have to
do it in parentheses,

00:03:36.600 --> 00:03:38.183
because it knows
order of operations--

00:03:38.183 --> 00:03:45.690
so 0.55 to the fourth
power is equal to 0.--

00:03:45.690 --> 00:03:47.370
let me write it down.

00:03:47.370 --> 00:03:50.224
Let me take it off the screen
so I can write it down properly.

00:03:50.224 --> 00:03:52.390
Actually, let me just do
both of these calculations.

00:03:52.390 --> 00:03:54.820
So this probability is
that one right over there.

00:03:54.820 --> 00:04:01.840
And then this one down here
is 1 divided by 4 times 0.5

00:04:01.840 --> 00:04:04.470
to the fourth power.

00:04:04.470 --> 00:04:07.040
So it's equal to that
right over there.

00:04:07.040 --> 00:04:09.940
And so let's be clear.

00:04:09.940 --> 00:04:12.420
The probability of
picking the unfair coin

00:04:12.420 --> 00:04:16.070
and then getting four heads
in a row is this top number.

00:04:16.070 --> 00:04:21.720
It's like roughly 6.9 chance
that you get the unfair coin

00:04:21.720 --> 00:04:23.350
and then get four
heads in a row.

00:04:23.350 --> 00:04:25.560
The probability that
you get the fair coin

00:04:25.560 --> 00:04:28.480
and then get four heads
in the row is even lower.

00:04:28.480 --> 00:04:31.460
It's only a 1.6% chance.

00:04:31.460 --> 00:04:34.640
Now the probability of getting
four heads in a row either way

00:04:34.640 --> 00:04:37.180
is going to be the
sum of this and this,

00:04:37.180 --> 00:04:39.740
or the sum of that
and that, which

00:04:39.740 --> 00:04:42.350
is going to be-- let me
keep my calculator out--

00:04:42.350 --> 00:04:44.900
so it's going to be
equal to-- I can just

00:04:44.900 --> 00:04:46.040
take the previous answer.

00:04:46.040 --> 00:04:48.360
Let me just retype it
so I don't confuse you.

00:04:48.360 --> 00:05:07.030
So 0.015625 plus 0.0686296875.

00:05:07.030 --> 00:05:09.530
I'm going to round it anyway,
so it won't matter too much.

00:05:09.530 --> 00:05:12.750
So if I take the sum-- let
me take this off screen

00:05:12.750 --> 00:05:14.980
so I can still see it
and then let me write it.

00:05:14.980 --> 00:05:23.040
So what I got here,
this one is 0.068629.

00:05:23.040 --> 00:05:23.990
And I'll round it, 7.

00:05:26.720 --> 00:05:33.670
This down here was 0.015625
and when you add these two up--

00:05:33.670 --> 00:05:36.902
because we just care about
getting four heads either way.

00:05:36.902 --> 00:05:38.360
There's a probability
of getting it

00:05:38.360 --> 00:05:39.849
this way with the unfair coin.

00:05:39.849 --> 00:05:42.140
This is the probability of
getting it with a fair coin.

00:05:42.140 --> 00:05:43.490
We want it either way.

00:05:43.490 --> 00:05:46.380
So let's add the two, which we
already did on our calculator.

00:05:46.380 --> 00:05:49.080
So if you add that
number to that number.

00:05:49.080 --> 00:05:54.950
You get 0.08425
and it keeps going,

00:05:54.950 --> 00:05:58.280
but I'm just going to round it.

00:05:58.280 --> 00:06:02.980
This is equal to
8.425%, or if I want

00:06:02.980 --> 00:06:06.880
to round it a little
bit more, 8.43%

00:06:06.880 --> 00:06:11.610
chance of getting
four heads in a row.

00:06:11.610 --> 00:06:15.170
And once again, that's
a slightly higher number

00:06:15.170 --> 00:06:17.580
than if all of the
coins were fair.

00:06:17.580 --> 00:06:21.110
Because there's a
3/4 chance that I

00:06:21.110 --> 00:06:23.780
get a coin that has a better
than even chance of getting

00:06:23.780 --> 00:06:24.280
heads.

00:06:24.280 --> 00:06:26.780
So that's why this number is
going to be a little bit higher

00:06:26.780 --> 00:06:29.470
than the probability if I had
a fair coin, of just getting

00:06:29.470 --> 00:06:32.470
four heads in a row.


Dependent probability example

WEBVTT
Kind: captions
Language: en

00:00:00.710 --> 00:00:03.080
You have eight coins in a bag.

00:00:03.080 --> 00:00:05.490
Three of them are
unfair in that they

00:00:05.490 --> 00:00:09.180
have a 60% chance of coming
up heads when flipped.

00:00:09.180 --> 00:00:11.430
The rest are fair coins.

00:00:11.430 --> 00:00:15.270
So if three or unfair,
the rest are eight coins.

00:00:15.270 --> 00:00:17.390
When this problem says
that they are fair coins,

00:00:17.390 --> 00:00:20.020
it means that they have a
50/50 chance of coming up

00:00:20.020 --> 00:00:22.090
either heads or tails.

00:00:22.090 --> 00:00:25.370
You randomly choose
one coin from the bag

00:00:25.370 --> 00:00:27.270
and flip it two times.

00:00:27.270 --> 00:00:31.980
What is the percent probability
of getting two heads?

00:00:31.980 --> 00:00:33.860
So this is an
interesting question,

00:00:33.860 --> 00:00:35.360
but if we break it
down, essentially

00:00:35.360 --> 00:00:37.790
with a decision tree,
it'll help break it

00:00:37.790 --> 00:00:39.330
down a little bit better.

00:00:39.330 --> 00:00:43.170
So let's say that we have a
bag, three of them are unfair.

00:00:43.170 --> 00:00:44.730
So we could even
visualize a bag.

00:00:44.730 --> 00:00:47.727
You don't have to do
this all the time.

00:00:47.727 --> 00:00:49.060
I'll do the fair coins in white.

00:00:49.060 --> 00:00:55.020
One, two, three, four,
five fair coins, and we

00:00:55.020 --> 00:00:56.240
have three unfair coins.

00:00:56.240 --> 00:00:58.190
One, two, three.

00:00:58.190 --> 00:01:01.530
And this whole thing is
my bag, right over here.

00:01:01.530 --> 00:01:03.680
That is my bag of coins.

00:01:03.680 --> 00:01:05.349
When I take my
hand in, if I were

00:01:05.349 --> 00:01:07.250
to take any of
these white coins,

00:01:07.250 --> 00:01:10.600
there's a 50% chance that
it gets heads on any flip.

00:01:10.600 --> 00:01:14.480
The odds of getting two heads
in a row would be 50% times 50%

00:01:14.480 --> 00:01:16.082
for these white coins.

00:01:16.082 --> 00:01:18.040
But I don't know I'm
going to get a white coin.

00:01:18.040 --> 00:01:19.920
If I get one of
these orange coins,

00:01:19.920 --> 00:01:24.280
I have a 60% chance
of coming up heads.

00:01:24.280 --> 00:01:28.087
If I have picked one
of these orange coins,

00:01:28.087 --> 00:01:29.670
the probability of
getting heads twice

00:01:29.670 --> 00:01:32.450
is going to be 60% times 60%.

00:01:32.450 --> 00:01:35.060
So how do I factor
in this idea that I

00:01:35.060 --> 00:01:38.380
don't know if I've
picked a white fair coin

00:01:38.380 --> 00:01:40.130
or an orange unfair coin.

00:01:40.130 --> 00:01:41.831
We'll assume that
the coins actually

00:01:41.831 --> 00:01:42.830
aren't white and orange.

00:01:42.830 --> 00:01:45.110
They all look like
regular coins.

00:01:45.110 --> 00:01:48.890
So what I'll do is I'll draw a
little bit of a decision tree

00:01:48.890 --> 00:01:50.090
here.

00:01:50.090 --> 00:01:52.730
I guess maybe I could call
it a probability tree.

00:01:52.730 --> 00:01:55.550
So there's some probability
that I pick a fair coin.

00:01:58.870 --> 00:02:04.090
And there's some probability
that I pick an unfair coin.

00:02:04.090 --> 00:02:08.139
And so what is the probability
that I pick a fair coin?

00:02:08.139 --> 00:02:12.110
Well, one, two, three, four,
five out of the total eight

00:02:12.110 --> 00:02:16.040
coins are fair, so there
is a 5/8 probability.

00:02:18.960 --> 00:02:21.190
I'll write it here on
the branch, actually.

00:02:21.190 --> 00:02:25.020
So there's a 5/8 chance
that I pick a fair coin,

00:02:25.020 --> 00:02:29.410
and then there is a 3-- one,
two, three, out of 8 chance

00:02:29.410 --> 00:02:31.089
that I pick an unfair coin.

00:02:31.089 --> 00:02:32.630
So if I were to just
tell you, what's

00:02:32.630 --> 00:02:33.950
the probability of
picking a fair coin?

00:02:33.950 --> 00:02:34.760
You'd say oh, 5/8.

00:02:34.760 --> 00:02:36.180
What's the probability
of an unfair coin?

00:02:36.180 --> 00:02:36.730
3/8.

00:02:36.730 --> 00:02:39.021
And you could convert that
to a decimal or a percentage

00:02:39.021 --> 00:02:40.400
or whatever you'd like.

00:02:40.400 --> 00:02:43.930
Now, given that I have
picked a fair coin,

00:02:43.930 --> 00:02:49.870
what is the probability
that I will get heads twice?

00:02:49.870 --> 00:02:52.740
So let me write it this way.

00:02:52.740 --> 00:02:54.500
Now this is just
notation right here.

00:02:54.500 --> 00:02:59.090
So the probability of--
I'll call it heads heads--

00:02:59.090 --> 00:03:02.430
so I get two heads
in a row, given

00:03:02.430 --> 00:03:08.485
that I have a fair coin-- it
looks like very fancy notation,

00:03:08.485 --> 00:03:11.460
but it's just like look,
if you knew for a fact

00:03:11.460 --> 00:03:14.173
that coin you had is
absolutely fair-- that it

00:03:14.173 --> 00:03:17.310
has a 50% chance of
coming up heads-- what

00:03:17.310 --> 00:03:19.886
is the probability of
getting two heads in a row?

00:03:19.886 --> 00:03:21.510
Then we can just say,
well, that's just

00:03:21.510 --> 00:03:32.890
going to be 50%, so 50% times
50%, which is equal to 25%.

00:03:32.890 --> 00:03:34.213
Which is equal to 25%.

00:03:40.810 --> 00:03:43.280
What is the probability
that you picked a fair coin

00:03:43.280 --> 00:03:46.460
and you got two heads in a row?

00:03:46.460 --> 00:03:48.560
So given that you
have a fair coin,

00:03:48.560 --> 00:03:51.410
it's a 25% chance that you
have two heads in a row.

00:03:51.410 --> 00:03:54.810
But the probability of
picking a fair coin and then

00:03:54.810 --> 00:03:56.920
given the fair coin
getting two heads in a row,

00:03:56.920 --> 00:03:59.430
will be the 5/8 times the 25%.

00:04:02.250 --> 00:04:04.384
So this whole branch--
I should maybe

00:04:04.384 --> 00:04:05.800
draw it this way--
the probability

00:04:05.800 --> 00:04:09.050
of this whole series
of events happening.

00:04:09.050 --> 00:04:10.910
So starting with you
picking the fair coin

00:04:10.910 --> 00:04:13.110
and then getting
two heads in a row

00:04:13.110 --> 00:04:15.200
will be-- I'll
write it this way--

00:04:15.200 --> 00:04:24.792
it will be 5/8 times this right
over here, times the 0.25.

00:04:24.792 --> 00:04:26.000
I want to make it very clear.

00:04:26.000 --> 00:04:28.750
The 0.25 is the
probability of getting

00:04:28.750 --> 00:04:30.930
two heads in a
row given that you

00:04:30.930 --> 00:04:33.154
knew that you got a fair coin.

00:04:33.154 --> 00:04:34.820
But the probability
of this whole series

00:04:34.820 --> 00:04:36.278
of events happening,
you would have

00:04:36.278 --> 00:04:39.090
to multiply this times the
probability that you actually

00:04:39.090 --> 00:04:41.850
got a fair coin.

00:04:41.850 --> 00:04:43.580
So another way of
thinking about it

00:04:43.580 --> 00:04:50.280
is this is the probability
that you got a fair coin

00:04:50.280 --> 00:04:55.730
and that you have
two heads in a row.

00:04:55.730 --> 00:04:59.020
Now let's do the same
thing for the unfair coin.

00:04:59.020 --> 00:05:03.400
So the probability-- I'll do
that in the same green color--

00:05:03.400 --> 00:05:06.780
the probability that
I get heads heads

00:05:06.780 --> 00:05:11.160
given that my coin is unfair.

00:05:11.160 --> 00:05:14.690
So if you were to somehow
know that your coin is unfair,

00:05:14.690 --> 00:05:18.910
what is the probability of
getting two heads in a row?

00:05:18.910 --> 00:05:21.600
Well in this unfair
coin, it has a 60% chance

00:05:21.600 --> 00:05:23.390
of coming up heads.

00:05:23.390 --> 00:05:32.650
So it will be equal to 0.6
times 0.6, which is 0.36.

00:05:32.650 --> 00:05:35.010
If you have an unfair coin--
if you know for a fact

00:05:35.010 --> 00:05:37.980
that you have an unfair
coin, if that is a given--

00:05:37.980 --> 00:05:42.355
you have a 36% chance of
getting two heads in a row.

00:05:42.355 --> 00:05:43.980
Now if you want to
know the probability

00:05:43.980 --> 00:05:45.980
of this whole series of
events-- the probability

00:05:45.980 --> 00:05:50.190
that you picked an
unfair coin and you

00:05:50.190 --> 00:05:57.010
get two heads in a row, so
the probability of unfair

00:05:57.010 --> 00:06:00.990
and two heads in a row given
that you had that unfair coin--

00:06:00.990 --> 00:06:06.490
you would multiply this
3/8 times the 0.36.

00:06:06.490 --> 00:06:17.510
So this will be equal
to 3/8 times 0.36.

00:06:17.510 --> 00:06:21.430
And so let's get a calculator
out and calculate these.

00:06:21.430 --> 00:06:36.540
So if I take 5 divided by 8
times 0.25, I get 0.15625.

00:06:36.540 --> 00:06:40.690
So this is equal to 0.15625.

00:06:40.690 --> 00:06:45.200
And then if I do the
other part, so if I have 3

00:06:45.200 --> 00:06:53.360
divided by 8 times 0.36,
that gives me 0.135.

00:06:53.360 --> 00:06:57.159
So this is 0.135.

00:06:57.159 --> 00:06:58.700
So if someone were
to ask you, what's

00:06:58.700 --> 00:07:01.590
the probability of
picking the fair coin

00:07:01.590 --> 00:07:04.740
and then getting two heads
in a row with that fair coin,

00:07:04.740 --> 00:07:05.832
you would get this number.

00:07:05.832 --> 00:07:08.040
If someone were to say,
what's the probability of you

00:07:08.040 --> 00:07:10.020
picked the unfair
coin and then get

00:07:10.020 --> 00:07:12.110
two heads in a row
with that unfair coin,

00:07:12.110 --> 00:07:13.570
you would get this number.

00:07:13.570 --> 00:07:17.150
Now, if someone were
to say, either way,

00:07:17.150 --> 00:07:19.700
what's the probability of
getting two heads in a row?

00:07:19.700 --> 00:07:21.600
Because that's what
they're asking us here.

00:07:21.600 --> 00:07:24.010
What is the probability
of getting two heads?

00:07:24.010 --> 00:07:27.380
So we could get it through this
method-- by chance, picking

00:07:27.380 --> 00:07:30.660
the fair coin-- or through this
method-- by chance, picking

00:07:30.660 --> 00:07:32.036
the unfair coin.

00:07:32.036 --> 00:07:33.410
So since we can
do it either way,

00:07:33.410 --> 00:07:35.080
we can sum up the probabilities.

00:07:35.080 --> 00:07:39.270
Either of these events
meet our constraints.

00:07:39.270 --> 00:07:41.930
So we can just add
these two things up.

00:07:41.930 --> 00:07:43.240
So let's do that.

00:07:43.240 --> 00:07:56.210
So we can add 0.135 plus
0.15625 gives us 0.29125.

00:07:56.210 --> 00:08:08.170
So point 0.29125, that's when
we add 0.15625 plus 0.135

00:08:08.170 --> 00:08:09.120
will equal this.

00:08:09.120 --> 00:08:11.080
And if we want to write
it as a percentage,

00:08:11.080 --> 00:08:14.030
you essentially just
multiply this times 100

00:08:14.030 --> 00:08:16.200
and add the
percentage sign there.

00:08:16.200 --> 00:08:21.260
So this is equal to 29.125%.

00:08:21.260 --> 00:08:25.030
Or if we were to round to
the nearest hundredths,

00:08:25.030 --> 00:08:26.570
then this would be
the exact number,

00:08:26.570 --> 00:08:30.410
or we could say it's
approximately 29.13%,

00:08:30.410 --> 00:08:32.620
depending on how much
we need to round it.

00:08:32.620 --> 00:08:36.450
So we have a little less than
a 1/3 chance of this happening.

00:08:36.450 --> 00:08:40.990
And the reason why-- if
everything in the bag

00:08:40.990 --> 00:08:44.740
was a fair coin, there'd be a
25% chance of this happening

00:08:44.740 --> 00:08:48.320
because you just say, OK any
of these, they're all the same.

00:08:48.320 --> 00:08:50.720
Flip it twice, 25% chance.

00:08:50.720 --> 00:08:52.320
Our chance is a
little bit higher

00:08:52.320 --> 00:08:54.420
because there's some
probability-- there's a 3/8

00:08:54.420 --> 00:08:58.120
chance-- that we pick a coin
that has a higher than even

00:08:58.120 --> 00:09:00.338
chance of coming up heads.


Detectable civilizations in our galaxy 4

WEBVTT
Kind: captions
Language: en

00:00:00.850 --> 00:00:02.810
I've talked a bunch
about the Drake equation,

00:00:02.810 --> 00:00:04.920
or our own version
of the Drake equation

00:00:04.920 --> 00:00:08.850
that starts with the number
of stars in the galaxy,

00:00:08.850 --> 00:00:10.520
but I haven't given
it a shot yet.

00:00:10.520 --> 00:00:12.830
I haven't tried my own
attempt at thinking

00:00:12.830 --> 00:00:15.750
about how many detectable
civilizations there are.

00:00:15.750 --> 00:00:18.370
So let's actually do that here.

00:00:18.370 --> 00:00:23.840
So let's just assume that
there are 100 billion stars.

00:00:23.840 --> 00:00:26.070
100 billion stars.

00:00:26.070 --> 00:00:28.680
So that's my first
term right over there.

00:00:28.680 --> 00:00:33.925
Let's say that 1/4
will develop planets.

00:00:36.520 --> 00:00:40.030
And let's say of the solar
systems that develop planets,

00:00:40.030 --> 00:00:45.640
on average let's say
that they develop

00:00:45.640 --> 00:00:50.110
an average of 0.1 planets
capable of sustaining life.

00:00:50.110 --> 00:00:52.590
Or really, that you'll have
one planet for every 10

00:00:52.590 --> 00:00:54.570
of these solar
systems with planets.

00:00:54.570 --> 00:00:55.970
That's just my assumption there.

00:00:55.970 --> 00:00:57.880
I don't know if that's right.

00:00:57.880 --> 00:01:00.850
Now let's multiply
that times the fraction

00:01:00.850 --> 00:01:02.660
of these planets
capable of sustaining

00:01:02.660 --> 00:01:05.230
life that actually
will get life.

00:01:05.230 --> 00:01:08.354
And I don't know what that is,
but I hinted in previous videos

00:01:08.354 --> 00:01:10.020
that life is one of
those things that it

00:01:10.020 --> 00:01:11.660
seems like if you have
all the right ingredients,

00:01:11.660 --> 00:01:12.640
it's so robust.

00:01:12.640 --> 00:01:15.060
And you have life it these
underwater volcanoes,

00:01:15.060 --> 00:01:16.630
you have bacteria
that can process

00:01:16.630 --> 00:01:18.260
all sorts of weird things.

00:01:18.260 --> 00:01:20.240
So let's say that
probability is pretty high.

00:01:20.240 --> 00:01:24.840
Let's say that is 50%,
or half of the plans that

00:01:24.840 --> 00:01:27.456
are capable of getting
life actually do have life.

00:01:27.456 --> 00:01:29.330
I would guess that that
might even be higher.

00:01:29.330 --> 00:01:32.100
But once again, just a guess.

00:01:32.100 --> 00:01:34.860
Now we have to think
about of the life, what

00:01:34.860 --> 00:01:37.430
fraction becomes intelligent?

00:01:37.430 --> 00:01:40.380
What becomes intelligent over
some point in the history?

00:01:40.380 --> 00:01:42.440
Well, I'll say it's a tenth.

00:01:42.440 --> 00:01:44.440
A tenth of all--
maybe if the asteroids

00:01:44.440 --> 00:01:45.510
didn't kill the
dinosaurs, it wouldn't

00:01:45.510 --> 00:01:46.468
have happened on Earth.

00:01:46.468 --> 00:01:47.660
Who knows?

00:01:47.660 --> 00:01:50.010
Or maybe we'd just have some
very intelligent dinosaurs

00:01:50.010 --> 00:01:50.510
around.

00:01:50.510 --> 00:01:52.019
We don't know.

00:01:52.019 --> 00:01:54.060
And maybe there's other
forms of intelligent life

00:01:54.060 --> 00:01:56.434
even on our own planet that
we haven't fully appreciated.

00:01:56.434 --> 00:01:58.570
Dolphins are a good candidate.

00:01:58.570 --> 00:02:01.600
Some people believe
that octopuses,

00:02:01.600 --> 00:02:04.700
because they have
such flexible arms,

00:02:04.700 --> 00:02:07.310
there's a theory that they
could develop eventually

00:02:07.310 --> 00:02:11.039
the ability to kind one
day, if their brains mature,

00:02:11.039 --> 00:02:13.720
and all of the rest, make tools
the same way primitive primates

00:02:13.720 --> 00:02:16.356
eventually were able to
have larger brain sizes

00:02:16.356 --> 00:02:18.230
and actually manipulate
things to make tools.

00:02:18.230 --> 00:02:18.839
So who knows?

00:02:18.839 --> 00:02:20.380
I don't want to get
into all of that.

00:02:20.380 --> 00:02:25.260
So there's a 1 in 10 chance
that you get intelligent life,

00:02:25.260 --> 00:02:27.670
and then assuming that
intelligent life shows up,

00:02:27.670 --> 00:02:31.640
what fraction is going
to become detectable?

00:02:31.640 --> 00:02:32.500
I don't know.

00:02:32.500 --> 00:02:36.520
I don't know whether dolphins
will ever communicate via radio

00:02:36.520 --> 00:02:37.560
or not.

00:02:37.560 --> 00:02:39.790
So let's just say that
is-- I don't know.

00:02:39.790 --> 00:02:48.210
Let's say that is another 1
in 10 chance, or I'll say 0.1.

00:02:48.210 --> 00:02:51.160
And then we have to multiply
it times the detectable life

00:02:51.160 --> 00:02:53.990
of the civilization on average.

00:02:53.990 --> 00:02:56.070
Once again, huge
assumptions being

00:02:56.070 --> 00:02:58.790
here, but the detectable
life of a civilization,

00:02:58.790 --> 00:03:03.060
let me just put it
at 10,000 years.

00:03:03.060 --> 00:03:04.770
Either they destroy
themselves, or they

00:03:04.770 --> 00:03:07.990
get beyond that type of
radio type communication,

00:03:07.990 --> 00:03:09.490
electromagnetic
type communication.

00:03:09.490 --> 00:03:12.200
Maybe they start doing all
sorts of weird, wacky things.

00:03:12.200 --> 00:03:13.840
Probably it won't
take you 10,000 years

00:03:13.840 --> 00:03:14.673
to even progress it.

00:03:14.673 --> 00:03:15.940
That might take you less time.

00:03:15.940 --> 00:03:18.440
But let's just do this
just for the sake of fun.

00:03:18.440 --> 00:03:20.300
And then the lifespan
of your average star,

00:03:20.300 --> 00:03:21.240
that's probably
one of the things

00:03:21.240 --> 00:03:22.880
that we have the best sense of.

00:03:22.880 --> 00:03:25.900
So on average, let's put
it at 10 billion years,

00:03:25.900 --> 00:03:27.839
10 billion years.

00:03:27.839 --> 00:03:29.130
So let's calculate all of this.

00:03:29.130 --> 00:03:32.580
Let's get my handy TI-85 out.

00:03:32.580 --> 00:03:34.260
And so we're going
to have 100 billion.

00:03:34.260 --> 00:03:37.060
That's 1 times 10 to the 9th.

00:03:37.060 --> 00:03:40.000
Sorry, that's 100
times 10 to the ninth.

00:03:40.000 --> 00:03:41.260
So let me clear it.

00:03:41.260 --> 00:03:44.590
Or you could have 1
times 10 to the 11th.

00:03:44.590 --> 00:03:55.510
That is 100 billion times
0.25 times 0.1 times .05 times

00:03:55.510 --> 00:04:04.960
0.1 again, times 0.1
again, times 10,000

00:04:04.960 --> 00:04:06.090
divided by 10 billion.

00:04:08.680 --> 00:04:15.670
So times 10,000, 1, 2,
3, divided by 10 billion.

00:04:15.670 --> 00:04:18.769
So that's one 1e10.

00:04:18.769 --> 00:04:20.339
1 times 10 to the 10th power.

00:04:20.339 --> 00:04:21.440
1 with 10 zeroes.

00:04:21.440 --> 00:04:23.830
So let's see what we get.

00:04:23.830 --> 00:04:26.820
We get 12.5, which is
kind of a neat number,

00:04:26.820 --> 00:04:29.200
but these are heavily
dependent on this.

00:04:29.200 --> 00:04:31.490
So we're saying if
given these assumptions,

00:04:31.490 --> 00:04:37.740
there should be 12.5
detectable civilizations

00:04:37.740 --> 00:04:41.510
in our galaxy right now.

00:04:41.510 --> 00:04:44.550
So the question is, why
aren't we detecting it?

00:04:44.550 --> 00:04:48.240
Maybe their radio signals, maybe
their electromagnetic waves

00:04:48.240 --> 00:04:51.900
are getting to us, but we can't
differentiate it from noise

00:04:51.900 --> 00:04:52.400
right now.

00:04:52.400 --> 00:04:54.525
And that's what the whole
SETI project's all about,

00:04:54.525 --> 00:04:57.760
of trying to keep track
of all this information,

00:04:57.760 --> 00:05:00.810
all of these radio waves, and
electromagnetic waves that

00:05:00.810 --> 00:05:03.410
are coming from outer
space towards Earth,

00:05:03.410 --> 00:05:06.519
and seeing if any of them
actually have any non noise

00:05:06.519 --> 00:05:08.810
signal, that actually look
like they're being generated

00:05:08.810 --> 00:05:11.180
by some type of
intelligent civilization.

00:05:11.180 --> 00:05:13.830
So maybe we're getting them, and
we're just not detecting them,

00:05:13.830 --> 00:05:15.380
or maybe something
else is at play.

00:05:15.380 --> 00:05:17.660
Maybe we've overestimated
one of these.

00:05:17.660 --> 00:05:19.830
Maybe there is a lot a
life, but maybe they're

00:05:19.830 --> 00:05:23.256
not using electromagnetic
waves to communicate.

00:05:23.256 --> 00:05:25.630
Maybe that's some type of
primitive way of communicating.

00:05:25.630 --> 00:05:27.974
Maybe they start doing
telepathy, or something crazy,

00:05:27.974 --> 00:05:29.890
or they start using some
type of quantum thing

00:05:29.890 --> 00:05:33.110
that allows them to communicate
more directly without having

00:05:33.110 --> 00:05:35.150
to wait for the speed of light.

00:05:35.150 --> 00:05:37.054
That is a very slow
way to communicate.

00:05:37.054 --> 00:05:38.720
And it is a slow way,
frankly, if you're

00:05:38.720 --> 00:05:41.290
trying to communicate
across solar systems,

00:05:41.290 --> 00:05:43.930
and stars, and planets,
or even across galaxies,

00:05:43.930 --> 00:05:45.030
one could imagine.

00:05:45.030 --> 00:05:48.320
So maybe we're just kind
of at a transition state

00:05:48.320 --> 00:05:51.417
of communication, that
electromagnetic waves, radio

00:05:51.417 --> 00:05:53.250
and all the rest is
just a transition state.

00:05:53.250 --> 00:05:54.708
Maybe in 100 years
we'll figure out

00:05:54.708 --> 00:05:57.060
another, better way
that's not detectable

00:05:57.060 --> 00:05:58.320
in our traditional ways.

00:05:58.320 --> 00:06:01.300
Maybe we're being bombarded with
another type of communication

00:06:01.300 --> 00:06:03.870
mechanism that we're just
not ready to perceive yet.

00:06:03.870 --> 00:06:07.040
Who knows, but it's just
a fun thought experiment

00:06:07.040 --> 00:06:08.855
to say that hey, given
these assumptions,

00:06:08.855 --> 00:06:10.980
there should be at least
a couple of civilizations,

00:06:10.980 --> 00:06:12.840
or a handful of
civilizations that we

00:06:12.840 --> 00:06:15.260
might be able to detect.