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This is the second of the talks sponsored by RDF
A few years ago, I was at a conference and taking questions at the end and uh...
I don't usually get hostile questions except from
religious people and they're extremely easy to handle
but then I got a hostile question which was not so easy to handle
uh... it was a very tricky and difficult question
and I thought: who is this
it turned out to be one of those I'm-an-atheist-BUT
questions
which are always the most difficult to deal with
it was of course Lawrence Krauss
and um... i didn't take very kindly to it at the time We've since become
the firmest of friends
and I have enormous respect for what he's doing
in the field of the public understanding of science which is the
field that I recently retired from
professing
He is of course a most distinguished physicist
uh... author of
many books
He interests himself in science generally and in the promotion of the understanding of science
generally
He's recently moved to Arizona
to start, what I think, is an extremely exciting initiative
and he is
associate director of the Beyond Center
and co-director of the
Cosmology Initiative and director of the New Origins initiative at Arizona State University
so the study of origins
origins of all kinds
right across the board from the origin of the universe
To the origin of life, to the origin of everything you can think of. What an amazingly
uh... exciting initiative to get started
At a university
I'm delighted that Lawrence is talking to us today
Please welcome him
Thanks, Richard
Actually, let me just say that my friendship with Richard has been
uh... a unique one in many ways, but one that's caused me every time that we're together
To think about things slightly differently
I hope mutually
and uh... And a true pleasure and honor to be here.
Richard asked me to talk about cosmology
uh... and I originally gave...
I talked to...
Miss Cornwell who was organizing this and told her what I was gonna talk about and gave her several titles...
she thought they were too depressing, so she said: Why don't you just make it...
We're all ***!
but uh...
But I decided not to use that title
the uh...
I put this quote up here, well I like to have quotes for people when I'm being introduced
So people have something to read
but uh
it's kind of useful, I think, because I want to, I'm gonna talk about modern
picture of cosmology and how it's changed our view of the universe - the past
and the future
and in some sense how that picture is
clearly remarkable
and far more remarkable than the fairy tales
that are made up
in most religious
situations
but the key point is mystery. That's one of the things that make science so special
I think is that
scientists love mysteries
they love not knowing!
that's a key part of science
the excitement of learning about the universe. And that again is so different
than these sterile
aspects of religion where the
excitement is apparently knowing everything
although
clearly knowing nothing
now
in any case, so that's one of the reasons I put this quote up here
but I'm gonna talk to you about mystery stories
so uh...
Now, I live in
in Phoenix now and people know what these are. I used to live in Cleveland
and then I had to tell people these were stars
and uh
and this is a picture of a globular cluster
and it's uh... a beautiful thing in a nice, clear night
but what I want to talk to you about is how our picture's changed, of the universe, so much that
the really important stuff in the universe is not the stars and galaxies
but the stuff you can't see
the mysterious stuff
that dominates nature.
uh... okay so it's mystery story, so let's begin
It was a dark
and stormy night
and Einstein had just developed his general theory of relativity in 1916
At an interesting time because he had developed that theory
which was the first theory
of not just how objects move through space but how space itself
could expand and contract and be dynamical a remarkable theory that told us that space
curves in the presence of matter. And it was beautiful and he kind of knew it was correct
but at the time, it disagreed with observation
which used to bother physicists of the old days
and uh...
the uh
and the observation was
that the universe was static and eternal - that was the conventional wisdom
In science, at the time, that the universe had been around forever and would be around forever
and his theory didn't agree with that because his theory of general relativity suffered
from the same
problems that
Newtonian gravity suffers from - gravity sucks it always pulls, it never pushes.
and if you put stars and galaxies out there, they will not just stay there
gravity will produce a universal attraction that will pull them together
so he tried to figure what to do and and he was able to
Change his theory slightly, consistent with the Mathematical symmetries
that have allowed him to develop it.
so I wanted to show you how he did this. So I have his equations which is a good thing to do at 9:45 in the morning
but I do have them in a user friendly fashion here
uh... okay
this is for the biologists...
uh... no, I'm just joking
so it's not completely festicious because the left hand side of Einstein's equations
tells you about the geometry of the universe
how things are curved in the presence of the source of curvature
which in this case is the energy and the momentum of the universe
so that's fine. And in fact, I'm a theoretical physicist, so I have to write the actual stuff
the Greek letters
that's much more illuminating to you, I'm sure
But, so, this was the theory that didn't work that explained the universe we didn't live in
Or so he thought
And, so he was able to change it a little bit
by adding an extra term to the left-hand side
which he called the Cosmological Term
This term on the left-hand side would produce a small repulsive force throughout empty space
so small, that it wouldn't affect
Newton's laws which, of course, had described beautifully Or were developed, in fact, to describe
the motion of the planets around the sun
and he wouldn't wanna destroy that. So small, you’d never measure it in the solar system
But it could build up on the scale of galaxies
and hold galaxies apart
and so that's how he thought he'd save his theory.
uh... now shortly after he introduced this term, it became clear that it was a problem and, in fact uh...
here's a postcard I got when I was on leave once in Switzerland at um...
In, in Zurich and it's from Einstein
to Hermann Weyl, who was a very famous mathematical physicist
and it's in German and some of your German is better than mine but this basically says,
it's already 1923 And he's already saying
if you get rid of the quasi-static universe then out with the cosmological constant
because he realized that
if the universe is really expanding which is what we now know and I'll talk to you about how
we know that
then you don't need a cosmological constant anymore, if the universe is expanding, gravity can be
universally attractive
And just slow the expansion. And the big question of twentieth century cosmology became -
Is there enough gravity to stop the expansion?
How'll the universe end, will it end with a *** or a whimper?
Will it end with the Big Crunch - the reverse of the Big *** Or will it expand forever.
In fact, that's the reason why I, as a particle physicist, got involved in cosmology - because I wanted to be the first person
to know how the universe would end. It seemed like a good idea
and you'll see
where that came from, but anyway
so in 1923
Einstein said, you know, I wish I hadn't put it in and threw it out, but it was really not 1923
but 1929
when we really knew the universe was expanding
and this is the person who convinced us
This is someone, and I always say this, so some of you may have already heard me say it before, but it’s true
He, this guy, always gives me faith in humanity
this is Edwin Hubble
and he began life as a lawyer
and became an astronomer
And so
there is hope
and he made many discoveries and I think, cause I'm little short on time and I won't talk about the
one of the biggest ones he made, but the biggest one he made, of course,
was the discovery that the universe
is, in fact, expanding
And it changed everything
This is what he discovered, now, these are not ***, these are galaxies
These are, uh
Again - for the biologists
the, uh
so our galaxy is here and when we look out
we see, uh, what he discovered was that all other galaxies are moving away from us
On average
and those that are twice as far away
are moving twice as fast, those that are three times as far away are moving three times as fast as that, etc.
and so, uh, and we codify this as velocity is proportional to distance
and um
Now, what does this tell you?
well uh... it obviously tells you we are the center of the universe
and it actually does, and, in fact, my wife reminds me of that
On a daily basis
and uh
uh... what it really means is that the universe is expanding
Uniformly, in all directions
Now, why is that?
why is this ridiculous observation
that wherever we are, things are moving away from us
tell us that
and I spent a lot of time trying to figure different ways to explain this, none of which have been particularly satisfactory
This, this i think the only way to understand it, is to get
outside the universe
We're in California, it's easy to do that here but uh...
But, but let me do it this way here's the universe
that's two-dimensional
and that you could stand outside of
uh... here's, you know, I put the galaxies at nice uniform distances here
and again here, and you could see at a later time the universe is bigger, the galaxies are a little bit further apart.
So if you were standing outside of that universe, it'd be obvious
that it was expanding uniformly
in all directions
now what would you see if you were on that universe, well just pick a galaxy, any galaxy
and the way we could figure out what you'd see from the galaxy
is to superimpose this image on top of this one, placing this galaxy on top of itself
and what do you see?
You see precisely
what Hubble saw - every galaxy is moving away from this galaxy
those that are twice as far away have moved
twice the distance in the same time
those that are three times as far away have moved three times the distance
and it doesn't matter which
galaxy you're on
Everywhere, you see the same thing, everywhere you think you're the center of the universe
so depending upon your mood, either every place is center the universe
or no place is the center of the universe
It doesn't matter!
The universe is expanding
and that really did change everything and, by the way, it had profound
religious implications, at least.
As some of you may know that in response to this and other things,
the pope , at the time
Gave an encyclical that science approved genesis
and uh...the interesting person, the first person that actually showed there had to be a Big ***
was a Belgian priest, who was also a physicist, named Georges Lemaitre
and uh... the really interesting thing about Lemaitre is when, when the pope
said that
Lemaitre wrote him a letter and said: Stop saying that!
just really amazing for priest, cause he said: This is scientific theory
you can take it, if you believe in god and believe in genesis, to validate your beliefs
but you can also take it
to be, and, in fact, the laws of physics take us right back to the beginning of time
Without god
what you take from it
depends upon your religious and metaphysical
beliefs
but, whatever you say, the big *** happened
and I think uh... that's, that if we could just convince a lot of people, just that,
That simple thing, that the universe is the way it is, whether we like it or not
I think we'd overcome a lot of problems in this country
And I'd have to waste far too much time on that
but this is a science talk, although I'll throw in little bits of
commentary throughout, I suppose
how do we know
the universe is expanding? It's such an important thing I wanna spend a few minutes on that
well we do, but, as these two guys on the plain out there in, in, in uh...
near Arizona
say to one another:
I love hearing that lonesome wail of the train whistle as the magnitude of the frequency of the wave
changes due to the Doppler effect
what they're pointing out is that when a train comes towards you, the train whistle sounds higher
When the train moves away from you, the train whistle sounds lower
and that same principal was used by Hubble and others and same is true for light
For very different reasons
so when we look at distant galaxies
if they're moving away from us - the light - which is a wave, gets stretched out, the longer wavelength
of a particle of light, is the red end of the spectrum so it's called red-shifted
and galaxies are more and more red-shifted
the further and further they are away from us so that’s how we know
their velocity
The velocity is easy
How do you know distance?
That's really hard
The universe is a big place
and we don't know how to take measures that big
we have to find some, a way of determining distance
without actually going to a place and that's hard
and um
in fact
one of the ways, well of course, the way we do this is we use physics
we could determine the distance to the back of the room if I turned out all the lights and
only one light was on and I knew it would have a 100 watt light bulb
by having an old-fashioned camera
which none of us have anymore that had light meter on it
and uh...
if there were a 100 watts there and if I was receiving one watt of light here
I know how that light spreads out as one over the square of distance
and so I could determine
by how much wattage I was receiving here, knowing the wattage of that light bulb, how far away it was
It's undergraduate or high-school physics exercise
the problem is the universe isn't full of hundred watt light bulbs
if it was, life would be easier so we have to try and find the equivalent.
we have to try and find what's called the standard candle
something whose intrinsic brightness we understand
therefore we look at it through a telescope, we see how bright it appears to the telescope
And we work backwards to figure out how far it is
that's the hard part. That's why it's been so hard to determine the rate of expansion of the universe,
cause it's hard to find standard candles