So, the universe is made up, the matter in
the universe, is made up primarily of dark matter.
80 per 7, 87% of the universe is dark matter, 13%
is normal matter, the kind of stuff we're made out of.
And what that tells you is, we really, it's pretty amazing for all
of our accomplishments, we still don't know what the universe is made out of.
This stuff we call dark matter, we have no
idea what it actually is, we only know, we can only infer its presence
based on things like the motion of the luminous matter that we can see.
The the gravitational lensing, the effect on space
time that we see around superclusters, or clusters, etcetera.
So it's really a remarkable fact that as, as much progress as
astronomy has made, we're still literally in the dark, about the largest constituent
structure, or largest constituent constituents of the universe.
So and finally, if we, you know, look at
all the matter that makes up the observable universe,
what we see is that it covers a space
that is roughly 91 billion light years in diameter.
So there you have it, space is pretty big and it is full of stuff.
And of course, what we're talking about here is the observable universe.
The part of the universe that we
can see that where light has had enough time
since the beginning of the universe to actually reach us.
There is, from what we understand right now,
this is the subject of our next lectures.
cosmologically, we believe that the universe is infinite.
So there's an infinite amount of stuff out there.
And infinite amount, infinite parts of the universe that
we cannot see and we don't know anything about.
Which is a mind boggling idea So okay.
That's it for lecture for our third week.
Now we go on to ask truly cosmological questions.
And that will be where we start next time.
Thank you.