HOW WE GOT HERE:
THE BIG BANG, HOW IT HAPPENED, AND WHY

OCTOBER 27, 2002
Alan MacRobert
Editor of Sky and Telescope Magazine


Good morning! I'm Alan MacRobert from the First Parish UU church in Bedford. I'm also the news editor of Sky & Telescope magazine in Cambridge, which I guess makes me an astronomer. At least I've been an amateur astronomer for most of my life, and now I'm one of the few people whose day job is to try to keep up with all the astronomy research news happening around the world. I met Jim and Joyce Pickel at a UU conference on Star Island a few years ago. And that's how I come to be here today.

Astronomy is about the big picture - everything in the universe, beyond our little planet Earth. What I'm here to talk about this morning is what astronomy has been uncovering about the origin of the universe itself - how everything began. And what I think this may tell us, or not, about ultimate purposes and meanings behind the very fact of existence.

These are big topics that humans have wrestled with since the beginning of history. The amazing thing is that we have now been actually finding out the genuine answers to how creation came to be.

How the material world came to exist is one of the deepest questions that religions everywhere try to tackle. Where did everything come from, and how did it get started?

For most of history, nobody had any way to know. It was a subject beyond hope of any rational detective work. So, people made up stories. Every culture has had its creation stories. There have been thousands of different creation stories around the world. All were dreamed up from the minds of their authors, with no way to choose among them.

Most of these creation tales have one thing in common. They picture the world being made from scratch pretty much the way it is now. All the world's incredible detail and complexity had to be made piece by piece, by gods or other supernatural beings. Early peoples could imagine no other way how things could come to be.

With a few exceptions. some ancient Greek philosophers, such as Anaximander of Miletus, proposed that the present complexity of the world could have grown or evolved naturally out of simpler conditions in the past - so the gods would only have to make a simpler, less formed world - presumably an easier job for them to do.

In the last few hundred years we've learned an enormous amount about the actual origins of things. In biology, evolution of species from a few simpler forms is as well proven as can be, and it is the basic engine by which all modern biology functions. At this point telling someone who works in biology that you don't believe in evolution is about like telling your auto mechanic that you don't believe in the existence of internal combustion. He'll think you're a fool, and you will be. All you need to account for the present diversity of life on Earth is a few simple beginnings in the chemistry of an early age - not millions of separate creations of life, one for each species.

The origin of the Earth itself, all the air and water on it, and the Moon, Sun, and the rest of the solar system - is also well known now. All you need in order to get a solar system like ours going is a large enough gas cloud in space that starts falling together under its own gravity. This is how the Earth, Sun, and solar system formed 4.6 billion years ago. We see the same thing happening elsewhere right now, to form many other stars, many other solar systems. Astronomers now actually have pictures of just about every step in the process.

This makes the job of creation look much easier. God the Creator just has to get a lot of gas going in space, write a few equations of physics to work on it, and set it loose. Everything happens by itself from there.

In every age, people say the hand of God did what they cannot account for themselves. When we do account for something, direct intervention by a creator moves back one step, and the job that he has to do becomes simpler. This has been the whole history of science. No longer does God need to labor over shaping the details of a whole planet, every lake and mountain. Gas in space is all it takes.

But, what made that?

This question, the origin of the universe as a whole, has occupied astronomers in recent decades and has gotten especially exciting in just the last five years.

For a long while astronomers fell into two camps: Those who thought the stuff of the universe was created at some particular time - and those who said it might have always been around, getting processed through stars and planets and back again over and over forever. This so-called steady state universe would be infinitely old. That way, it would sidestep the issue of creation. If the universe has always been around, then it was never made - and no one was needed to make it.

But the steady state universe was ruled out about 35 years ago. The origin of everything in a Big Bang 13 or 14 billion years ago is now quite thoroughly proven. In fact at this point it's about as definite as the fact that the Earth is round instead of flat. All the galaxies, including ours, are flying away from each other as a result of the Big Bang explosion. (Galaxies are the largest building blocks of cosmic structure.)

We find that no stars are older than a maximum of about 13 billion years - and we would know it if they were.

The mix of chemical elements that the nuclear pressure cooker of a Big Bang ought to cook up, given its particular temperatures and pressures, is exactly the mix of elements that we see the universe was originally made of.

Most importantly, radio astronomers found as early as 1964 that the sky is filled with the faint microwave afterglow, as it were, of the early Big Bang itself. And it has exactly the characteristics it should if it were in fact the remnant of the Big Bang's original white light.

The exciting breakthroughs in the last few years have come from our new ability to analyze this cosmic microwave background radiation in detail. At first it appeared very smooth and uniform, but if you look at it with sensitive enough instruments, you find that it is full of slight irregularities, slight ripples, that differ in brightness from one place to another by no more than 1 part in 30,000. These ripples are the fossilized signatures of events at the Big Bang's very first instant.

By analyzing the strength and abundance of these ripples at different size scales, as seen on the sky today, you can tell an amazing amount about the universe's very early history and its total contents. Right now more than two dozen teams are racing to map these patterns using various instruments on the ground, carried by balloons, or in space.

For instance, we found out in 1998 from these studies that the universe must have started out containing exactly the right amount of matter and energy to keep it balanced between expanding forever and recollapsing into a Big Crunch. We have found out that ordinary matter, such as stars and planets and gas in space - everything made of atoms - amounts to only 4 percent of this total matter and energy budget making up the universe. Another 24 percent or so is some kind of invisible dark matter, probably made of particles physics has yet to discover. And the remaining 70 percent or so is some kind of unknown "dark energy" that acts like a kind of reverse gravity on the very largest cosmic scales and is making the expansion of the universe actually speed up, a completely unexpected discovery. Five years ago no one had a hint of this.

These studies of the patterns in the microwave background radiation from the Big Bang also support a 22-year-old theory called the "inflationary universe" - which successfully explains how events in the first tiny fraction of a second after the beginning shaped many features of the universe that would otherwise be inexplicable. The inflation theory involves an extremely rapid expansion that took place for about the first 10 to the -32 second. In addition to solving several other mysteries, it naturally creates the largest structures we see in the universe today - clusters of galaxies - out of microscopic, purely random quantum fluctuations in the superhot, superdense substance of the universe at that very early moment.

So here we are today looking right at the light of the Big Bang explosion - what appears to be a creation event that gave birth to the entire cosmos at a certain, definite time in the past.

What caused the Big Bang?

The answer used to be, "Nobody has any idea." It looked as if all the matter in the universe, and even space and time themselves, just burst into existence out of literally nothing. Science could not address the question of where the Big Bang came from, or whether it had any cause at all. A basic everyday law of physics is the conservation of matter and energy, which says you can't get something from nothing. The Big Bang was getting everything from nothing. The ultimate free lunch.

If I were giving this talk some years ago, that would be the end of the story. The need to invoke the hand of God had been pushed back to the very first instant of existence, and all he had to was reach down, with one finger like on the ceiling of the Sistine Chapel, and create the simplest thing possible - a single, infinitely dense point of undifferentiated mass. No divine intervention is required after the Big Bang. It's all you need, to account for everything that exists today.

I remember the Reader's Digest magazine, where my mother used to work, seizing on the Big Bang as proof of divine creation. "Have Astronomers Found God?" was the title of a Reader's Digest article by Robert Jastrow that he later expanded into a book.

But remember, what is inexplicable to the scientists of one generation often gets figured out by those of the next. Supposedly profound philosophers who think that the unknowns of their own particular time are ultimate and final unknowns - proof of supernatural intervention - tend to be made fools of by new discoveries very quickly.

And so it has turned out with the Big Bang. The creation of everything from nothing, which a few years ago seemed truly impossible - the epitome of a miracle - is now being explained in terms of natural processes of the sort that happen every day and can be observed in the laboratory.

(pause)

The first suggestion of how the creation of everything from nothing could be achieved in a purely natural context was published in 1973 by Edward P. Tryon, a physics professor at Hunter College in New York. He called attention to the fact that, by the so-called uncertainty principle of quantum mechanics, the entire cosmos could have burst into existence out of literally nothing - if certain constraints on its total mass and energy, total electric charge, and other quantities were met.

As Tryon tells it, the idea first hit him one afternoon in his Manhattan apartment. He had been wondering why the universe's total mass seems to be equal to its total gravitational potential energy - that is, the energy in the gravity that every bit of mass exerts on every other bit of mass. There was no apparent reason why these two very large numbers should have anything to do with each other. Yet they match to the accuracy with which they are known. Tryon realized that if they were exactly equal they would cancel out, since potential energy is negative - as maybe you remember from high school physics. The universe would then have a net energy of zero.

(slow!) According to quantum mechanics, any system with a very small net energy, like an atomic particle, can appear literally from nothing, uncaused - exist for a brief moment - and vanish. These so-called vacuum fluctuations, or virtual particles, are detected in the laboratory. They appear spontaneously throughout empty space all the time. The lower the total energy of a particle or system, the longer it can exist this way. A system with a net energy of exactly zero could appear from nothing under the laws of quantum mechanics and exist forever.

Tryon realized there is no limit to the size of the vacuum fluctuations always occurring in empty space. Larger ones are just much less common than smaller ones. Given enough time even the largest conceivable ones must inevitably occur, spontaneously, purely by chance. A big enough one might be indistinguishable from the Big Bang.

It worked. Tryon had come up with the first explanation for the existence of the universe that does not require supernatural help. I'm talking about this now-rather-dated historical point because I interviewed him in New York not long after that for a magazine article. He remembered the moment when he was sitting on his couch when it all fell into place. "The instant I saw the possibility I was just so taken with it," he told me. "I just felt, 'This is it!' That it was simple and beautiful and natural. That it was inevitable, in the impersonal beauty of its logic."

That was in 1973. Tryon's conjecture became an interesting sidelight of physics and astronomy. But it did not seem to lead anywhere. There wasn't much that a researcher could do with the idea - to test whether it was true or false. You could only say it was an interesting guess.

However, that changed. New developments in physics have led to ways in which universe-creation processes are being tackled productively in mathematical detail.

One key has been the inflationary universe paradigm I mentioned earlier of how the Big Bang happened. It was first worked out by Alan Guth at MIT around 1980. It explains many details about how the universe came to be the way it is today, by having it undergo a very brief period of extremely rapid growth just after getting started. There's lots of concrete evidence now that inflation is true. And this has opened up a much wider picture of what made the Big Bang - and what came before.

The picture that has been taking shape is that our universe, our space-time, began as a tiny bit that budded off, and separated from, a much larger, underlying, superhot, superdense space that continues inflating at a superfast rate forever. Our space is now completely separated from that larger space, or other dimension - it has gone on its way without us.

A key point about this picture is that the creation of a universe like ours doesn't happen just once. Our Big Bang was just one of many, happening all the time, bubbling away and separating from an underlying, outer dimension of superdense matter all the time. These separate Big-Bang universes quickly become disconnected, disjoint, from this underlying space and from each other.

If this is so, what we are used to calling "the universe" is not the whole of existence, but merely a tiny, incidental spinoff of natural processes happening in some much larger, underlying realm.

What is the nature of the larger realm that contains these many Big-Bang universes? Exactly how many other universes are there, and what are they like? Are they like ours, or are they perhaps terribly different? These are now recognized as real questions that have real answers.

In losing the neat, simple picture of one Big Bang created by the hand of God, we have gained a look into a much larger vista of universes without end, great and small, in numberless profusion.

I should explain what would make something "another universe," rather than just a very distant part of ours. It would be in no way connected to our space and time. That is, you can't get there from here. Even if you traveled infinitely far and explored everywhere there is to get to. These other universes, the products of other Big Bangs, are separated from us by some unknown dimension. No information from them, no sign of them, can ever come to us.

In that case, you might ask, how can we ever find out if these ideas are true? We'll never be able to send a space probe into another universe to send back photographs, or bring back a sample of its material.

(slow) But, many scientists think there is one indirect piece of evidence that other universes really do exist. And it has caused quite a lot of ferment.

There are certain remarkable coincidences in the laws of physics. It turns out that only some very special coincidences in the numbers that appear in physics allow the existence of any form of life at all. For instance, there's a number called the fine-structure constant that governs the behavior of atoms. If that number were just a tiny bit different one way, the Sun and stars would be cold and dark because hydrogen fusion reactions wouldn't work, and there could never be light or warmth to allow life to develop on planets anywhere. If that number were just a tiny bit different the other way, the Sun and stars would all burn up so fast that life would not have time to evolve. Either way, we wouldn't be here.

That's just one example. There are many others like that among the basic laws and constants built into physics. Many of these numbers seem to be extremely fine-tuned to make possible the existence of intelligent life, or any form of organized matter at all. It's as if the laws of nature themselves were deliberately designed for our benefit.

Is this, finally, a proof of God's finger at work? Under the old, simple version of a single Big Bang, it looked very much like it, and many people got quite excited about it.

But there's another possibility. Try to follow this. If there indeed exist many universes, as the new explanations for the Big Bang imply there are, the situation can be explained naturally. You just suppose that the laws and numbers of physics assume random values in each different universe. Most universes will not have the special conditions that allow the formation of any kind of life because they will not allow the formation of any kind of organized matter. Not even atoms other than hydrogen. Only a very rare universe will happen, purely by luck, to come out with just the right mix.

Since we are living things, when we look around us we will necessarily find ourselves inside one of those rare, lucky universes that allow for any kind of life. It will look to us like this universe was specially fine-tuned for our benefit - even though it came about at random like all the others. Most of the others will be forever barren - going through their existences, in the words of Paul Davies, "in roaring heat or silent cold, unknown, unobserved, and apparently pointless."

So the new universe-creation theories of the last few years kill two theological birds with one stone. They remove the need for the hand of God to create our Big Bang, and because they seem to require there to be many universes, they remove the need for God to fine-tune the laws of physics specially for us.

(pause)

So the need for the hand of creation has been pushed farther back, by a very big step, one more time. This is the way it always seems to go.

I find this wider picture that we are getting wonderful and beautiful and fascinating but also bleak. We know well enough from our lives and experiences right here that if there is a God, or any kind of cosmic purpose, he or it really doesn't appear to care much about us. He doesn't lift a finger to stop the most horrible tragedies. He let Paul Wellstone's plane go down. Nature is uncaring. For that matter the whole world could get wiped out by a random asteroid. But at least one could take faith in Creation happening for a reason - a God leaning down and starting the Big Bang from his fingertip like he meant what he was doing. I liked that idea.

Now it really looks more and more like the Big Bang happened just as naturally and randomly as anything else: for no particular reason. It just, well, sort of happened, along with lots of other, sterile creations that really do look purposeless. Everything we know indicates that our universe was just kind of coughed up by blind forces.

This talk was supposed to be answering the question why the Big Bang happened. I think I can really give you the likely answer to that: For no particular reason at all.

If you are looking for ultimate, human meaning and purpose in existence, I have to tell you astronomy isn't the place to look. If we want meaning and purpose, we have to create them right here, ourselves.

This conclusion may be bleak, but it is also liberating. We create our own meaning. Nobody has done it for us. This was the genius behind the impassioned humanist thinkers who did so much to create UUism a century and more ago. I don't see other religions facing up to this job - they just keep making up stories to try to pull in meaning from elsewhere, and the things they end up with have often served humanity poorly.

We're the church where you don't have to pretend to believe in someone's made-up stories. Our great humanist heritage (even if it doesn't seem to be much to the fore in UUism right now) says we can look reality in the face and take it for what it is. And that if we want meaning and love and direction and progress and purpose, we won't find them in the stars... we won't find them in what science tells us about how the world actually did begin... we have to create them here and now, ourselves.