What's the matter with the dark matter?
I'm going to explain you with the help of
the Galaxy Rotation problem.
So first, we know how our solar system works,
with the help of the equations of Newton.
So here are the orbits and so on...
Here's the Mercury, the Venus, the Neptune
and the Pluto.
Mercury moves much faster in it's orbit than
Venus, than Neptune and than the Pluto, respectively.
So the speed of planets slows down as we go
far from sun.
And this all makes a perfect sense according
to the Newton's law of Gravity.
That Gravity is inversly proporstional to
the square of the distance.
So as we go far, Gravity decreases...
But astronomers in 19th century observed some
strange thing in Galaxies.
The stars in the galaxy were not behaving
as they should, according to Newton's law
of Gravity.
There was lot of discussion going on back
then.
So here we have a typical Galaxy.
So first we know that stars at edge must move
slowly as compared to the stars at centre.
But the stars closer to the edge were moving
faster than the stars closer to the centre.
Not just the same but much faster.
An astronomer, Vera Rubin first observed it
in the Andromeda Galaxy, so then she studied
it in more than 60 different Galaxies, same
story.
Disobeying Newton's law of Gravity...
So is it wrong, is Newton Wrong?
Consider a Galaxy.
Stars located here and here, here and here.
So we draw the angle to it and we find it
that Star at the edge covers more distance
in same time then the Stars closer to the
centre.
So there must be something in between the
Stars, some sort of matter which lets the
Galaxy to Rotate, the whole of it.
So an Astronomer named Fritz Zwicky named
it 'Dark Matter'.
So it isn't that Newton had got the Law of
Gravity wrong but it was the weird way Physics
behaved.
Therefore Newton was right.
So what about the Dark Matter?
Dark Matter is not just ordinary matter.
We know it's existance with the help of the
light it bends around it.
Not like a Black Hole.
But differently.
We can't see it.
But we can feel it's existance.
Infact, Dark Matter fills up the universe
way more than than ordinary matter.
I'll surely tell about whats Dark Energy in
future Videos...
But till then WONDER, leave comments down
below about your views...
