THE REAL STORY OF THE "BIG BANG"...
So let me explain to you what the big bang really is. So forget
that old picture which many of you might have brought with you.
I want to take these galaxies, and you saw the galaxies, they
are randomly spread around, but to make this more understandable,
I am going to pretend that they are laid out in a regular array
(that's a detail that doesn't really matter) but it will help
you visualize what is going on.
So here is the universe, just laid out in regular array
just for the purposes of teaching. Now, what Hubble observed
was that the galaxies, let's pick our own galaxy, which one is
us, it doesn't matter, let's pick this one. What he observed
is that these galaxies are all moving away from us and that the
ones that are further away are moving away twice as fast, so this
is Hubble's law in pictures.
What will the galaxy look like 2 billion years from
now? Well, just put those galaxies, I have marked them in red,
just move them to their new locations and here is what it will
look like. So we are going from this to this, the universe is
getting bigger, all the galaxies are getting further apart, and
yet it doesn't look so much like the Milky Way is special. In
fact, here I put the Milky Way right there, put the Milky Way
right there and then you drew these little arrows. But let's say
someone is sitting out here on this one, well they say "oh
I'm not moving, my galaxy is stationary, after all I'm still here",
so you put that one as the one that is not moving, you move it
over like that and guess what that person observes? You're right
--- it's the same Hubble's Law. So there is no center to the universe.
Or, you might say, everyone thinks they are in the center, regardless
of where they are.
An analogy that I like to make and you may have seen this in books
is that the universe is like raisin bread and here we are the
raisins, and the raisin bread is rising and you are sitting on
one raisin. There is your friend raisin over there; it is moving
away from you and your friend over there is moving away from you
and everywhere you look your friends are moving away from you.
It looks like you are at the center and everything is moving
away from you, but to your friend, everything is moving away from
them, everything is just getting further apart. When that happens
you get Hubble's law because the raisin that is twice as far away
will be moving away twice as fast. So this is the picture of
In fact, the picture of the universe that all people who
work in this field hold is that the universe is more or less uniformly
filled with galaxies. Not quite as regularly as we show here
but it is filled everywhere with galaxies, that they are all moving
apart from each other. "Oh, yeah," your student will
ask you, "where is the crust?" At some point you must
run out of space. The remarkable answer is "NO". You
can have expansion of the universe without having additional space
at the edges that you move into. In fact, as far as we know,
there is no region of the universe that we know of that is different
from what we see here today. The universe is full of matter everywhere
and in every cosmological theory that is taken seriously. I'll
show you the evidence for this; I'll show it to you in a moment.
The evidence seems to be that the universe is completely filled
with matter, everywhere, but that this matter is all moving apart
from itself. Where is the space coming from?