Todd, welcome, it's so good to see you.
>> Thank you, It's good to be here.
>> As a cosmologist and as a person who's teaching science for
the larger public, I'm delighted to have you here and to share your knowledge.
We'll begin with the big scale.
Shall we? >> Okay.
>> Let's begin with the story of galaxies and the fact that 100 years ago
we were thinking the Milky Way was the only galaxy in the universe.
>> Mm-hm.
>> What happened to expand our knowledge of the size and
scale of the universe and galaxies?
>> Yeah, so that's probably one of the most amazing stories of human history,
actually, is the fact that we've gone from thinking that all the little
fuzzy spiral things that you could see and
telescopes spiral nebulae, which basically means spiral cloud fairly nearby,
just clouds like other kinds of clouds you'd see in the night sky.
And really the key piece that
broke through that was being able to have telescopes and techniques to
be able to measure distances to those objects by actually finding stars in them.
And this was pioneered by lots of people but Henrietta Levitt
is one of the astronomers who play the key role and being able to make that happen.
And Edwin Hubble and around the early 1900s, people
started being able to measure distances to galaxies like our Andromeda galaxy and
found out the modern distance is about 2.5 million lightyears away.
And so that was just the beginning sort of a waiting out into the surf,
a little bit, of being able to realize that now we can actually measure distances
to galaxies that are over ten billion light years away,
which means that it takes light going at 300,000 kilometers a second
ten billion years to get from that object to us.
It's really hard to wrap your mind around how much that expands,
how big our universe is.
You know if you stand and look out on a field or you look out at the ocean and
you sort of comprehend how big the earth is and
then you try to picture how much bigger.
You know it takes like way less than second to go around the earth and
to be able to talk about distances where it takes.
10 billion years it's just
hard to comprehend how much that changes your perspective.
>> It's staggering, isn't it?
And the fact that Andromeda we can see
with the naked eye even on a clear night and so on.
But tell us about galaxies, are there different kinds of galaxies and
then how are they formed?
>> The general type like our own is actually a barred spiral galaxy.
So it's just like the name sounds it's a spiral shape with
kind of a bar shape in the middle.
Then there are just pure spiral galaxies is another class.
And then there are irregular galaxies, which as the name implies,
they're just sort of funny looking shaped things, little blobs.
And then there are elliptical galaxies, which are sort of football shaped and
the basic formation process for galaxies is, I think, a really fun example of
how simple principles can produce complex, interesting, varied systems.
Basically they're all driven by gravity.
So, the way I like to think it, the whole evolution of the universe
from a cosmologist point of view is going from at one end, from simple and
smooth at the early parts of the universe, about 14 billion years ago,
to clumpy and complex, which is what we have now.
So, a lot of cosmology is understanding how we got from simple and
smooth to clumpy and complex, which of course,
we're very grateful for because we're clumpy and complex.
>> Complex, exactly.
>> So, the basic understanding of the process is that at the early stage,
the universe was very, very hot and dense and smooth,
dominated by light radiation.
And so everything was very evened out, so
you could picture it just like a, maybe a lot like if you were inside the sun.