Hey guys this is Astronomical thoughts where
I discuss really cool ways of thinking about
astronomy phenomena.
And in this video, I'm going to be discussing
how scientists discovered dark matter.
So we know that any object that has mass will
be attracted to any other object that also
has mass due to gravity.
And the further away any two objects with
mass are from each other, the less gravity
they will impose on each other.
In our solar system, for example, most of
the mass comes from the sun so all the planets
are attracted to the sun due to gravity.
and so in our solar system we see that as
we go further out, planets start to feel less
and less gravity.
So for example, earth feels more gravity from
the sun than pluto because earth is much closer
to the sun than pluto.
And because pluto feels less gravity from
the sun than earth, pluto orbits the sun at
a much lower speed than the earth.
So the further a planet is in our solar system
from the sun, the lower its orbital speed
is.
Now, much like in our solar system, our whole
galaxy has a centre much like the sun and
the whole galaxy orbits around it much like
the planets in our solar system.
So if we apply the same logic as in our solar
system,
it should be that the further we go from the
centre of the galaxy, the slower the orbital
speed should be but that's not the case.
The further we go from the centre of a galaxy,
the orbital speed does not decrease.
Now this implies that there must be additional
mass that is there but
we cannot see it that is responsible for increasing
the orbital speeds of objects at the end of
the galaxy.
Scientists call that additional mass ' Dark
matter'.
Thanks for watching and take care.
