Bob McDonald

What was the Big Bang (and what came before it)?

… In the beginning (you know we had to start like this) the Universe seems to have been an infinitely hot, infinitely dense concentration of energy, not that we are entirely sure that the words beginning, hot, and dense have any meaning in this context, as we don’t have a working theory of physics to describe how anything behaves in these conditions. Once the Big Bang was underway, however we’re on slightly more familiar territory. Space started to exist, and the clock began to tick. Then something unusual and important happened: the Universe blew up.

It didn’t blow up in the sense of an explosion that blasts energy and matter outward, but in the sense of a balloon inflating. The Universe expanded exponentially, and it did so very quickly — faster than the speed of light. This idea is known as inflation, and it’s become the dominant theory to explain this time in the Universe because it neatly deals with several problems physicists have struggled with. One is how the Universe can be as big as it is (which it couldn’t be without this sudden early inflation) and another is how it later evolved, developing the concentrations of mass and energy that became galaxies and stars. These questions are complicated, to say the least, but the theory of inflation solves them, so physicists have become quite fond of it. In any case, the Universe experienced a brief burst of incredible growth in a very short time — far less than a billionth of a second.

Then it ends. The Universe was tiny at this point, only tens of centimetres across. For the next few billionths of a second it grew at a fantastic rate, more slowly than in the burst of inflation, but faster than the speed of light. This might seem a bit confusing: as nothing can travel faster than the speed of light, how could the Universe have expanded faster than the speed of light? The explanation is that expansion is not the same as travel. Aclumsy
analogy is two airplanes flying in opposite directions at their maximum speed — say 500 kilometres an hour. They’re flying apart at 1,000 kilometres an hour, but neither is travelling faster than 500 kilometres an hour. The analogy isn’t exactly correct, as there were no objects in the Universe at this point, but space itself was getting larger. We did say this was confusing.

During all of this early expansion there was no ordinary matter in the Universe. It was simply too hot for anything like an atom to exist. Things cooled off, though, as space expanded as there was less pressure constraining the energy of the Big Bang, and less pressure means less heat. As the Universe cooled, the building blocks of ordinary matter began to form. First subatomic particles like quarks took shape and then as they cooled they combined into protons and neutrons. At this point, the Universe was only one second old, and things were still pretty hot — about a trillion degrees. It took about four more minutes for things to cool enough that atomic nuclei could form as protons and neutrons come together to form deuterium (heavy hydrogen) and helium. The Universe now is filled with plasma — a hot soup of atomic nuclei and electrons. It stayed like this for a very long time.

Around 400,000 years after the Big Bang, the plasma had cooled enough for electrons to settle into co-existence with
protons. What existed was a fog of hydrogen, deuterium, and helium. This was the only normal matter in the Universe. It was plenty hot, at a temperature of about 3,000 degrees. Because these electrons were no longer free, they were not intercepting photons any more, and the Universe became transparent. Before this stage it was impossible for light to travel through the plasma — plasma is opaque. There was, however, not much to see. This was the Universe’s dark age. There were no stars to illuminate the Universe.

Eventually, the hot fog condensed into discrete clouds, and these clouds collapsed to form the first stars and galaxies, and when the stars lit up, the Universe was something like what we see in the skies today. These first stars burned fast and hot, and in only a few million years they exploded in massive supernovae. Their ashes formed the next generations of stars, which populated the Universe we live in.

This succinct explanation omits a wealth of detail about the Universe’s dark ages and how the first stars formed, one of the hottest areas of astronomy today.

That takes care of the time after the Big Bang. The natural question that comes next is where did the Big Bang come from. This is a different question from what was before the Big Bang. When you think about it, that question doesn’t make sense, as time as we understand it came into existence with the Big Bang. So where did the Big Bang come from?

Unfortunately that’s not a question for which science has a good answer. Observational astronomy, along with particle physics, theoretical physics, and mathematics, has developed the picture of what happened when the Big Bang banged and time started. We’re still reaching for understanding about the infinite energy and density that had to exist as a precondition for the Big Bang. At best, this is the realm of (educated) speculation. So little is known that this section of the book might as well be labelled like medieval maps of unknown territories with a large illustrated inscription: “Here be Dragons.”

Theoretical physicists aren’t scared of dragons, however. Physicists working on String Theory and Loop Quantum Gravity and Quantum Cosmology and the Grand Unified Theory are attempting to develop physical and mathematical models that would describe the conditions that created the Big Bang. These theories are very difficult for laypeople to understand as in essence they are mathematical, and the metaphors used to describe them — like strings — aren’t always helpful.

So for now, at least, the question of what caused the Big Bang is best answered with a shrug — or maybe a polite change of subject. After all, what fun would it be if we knew everything?

I’m Not Listening

Why does a snorer never hear him or herself? The noise can be truly awesome, as any victim can attest, and I’m at a loss as to how anyone can sleep through the echoing thunder coming from the pillow next to our own. Why are we the only ones to hear it? Why can’t the snorers?

Dr. Meir Kryger, Professor of Medicine at the University of Manitoba and Director of the Sleep Disorders Centre at the St. Boniface Hospital Research Centre in Winnipeg:

This listener is going through something that many people go through, and it can certainly seem mystifying that a snorer can sleep through the tremendous racket they make. The explanation lies, of course, in our brains. Our brain basically ignores information that it doesn’t consider important. The snorer’s brain just decides that the noise from its own snoring is not going to wake it up.

We used to think that the sleeping brain was basically in neutral, idling and not doing much. All sorts of experiments have proved that this isn’t the case, that the brain is extremely active during sleep. We know that it is “hearing,” but that it does a lot of filtering and signal processing, so that it will only respond to the kinds of sounds it knows are important. Mothers, for example, become sensitive to the softest cries of their babies when they need to be fed, but will ignore the louder noise of an airplane flying overhead at four in the morning.

A lot of this filtering is going on in a region of the brain called the thalamus. We don’t understand the mechanism, though, and we certainly don’t understand how the brain decides what’s important and what’s not important. It is a quite amazing ability. Snorers can reach eighty decibels, louder than a barking dog, and sleep through the whole thing. When you play them a tape of themselves snoring, they can’t believe they are able to sleep through it.

Of course, an interesting question is, if the snorer’s brain can ignore the noise, then why can’t the brain of the person lying next to them do the same thing? The answer is that it can and often does. Snoring is very common, especially in Canada, it seems. In a study done in Toronto several years ago, about 80 per cent of wives claimed that their husbands snored. Other studies from around the world have found that about 30 per cent of adult men and about 15 per cent of women snore. There would be a lot of sleep-deprived women and men out there if they could not adapt to their partner’s snoring. Studies have shown that if the bed partner can fall asleep before the snorer, she or he will very often sleep through the snoring. However, the bed partner who doesn’t fall asleep before the snoring spouse may be doomed for the night, since the unconscious mind seems to be better than the conscious mind at filtering out that infernal racket.

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Sticky Feet

Why don’t flies fall off the ceiling?

Dr. Hugh Danks, Entomologist with the Canadian Museum of Nature in Ottawa:

The first thing to note is that flies are light in weight and they’re small in size. They have an external skeleton that is relatively light, and, in contrast, humans have a heavy internal skeleton made of bones. If we were to try to hang from the ceiling, we would need some pretty sophisticated hardware. But flies are light, so they don’t need the hardware. They are light enough that they aren’t really fighting much gravity to stay suspended.

Flies use tiny pads on their feet to hang from the ceiling. Each foot has a couple of claws, mainly used for hanging on to rough surfaces, and two tiny pads that allow them to attach themselves to smooth surfaces. We are not certain how these pads work, but there are very minute hairs on the pads and an oily secretion. It seems that, when the pad is applied to a surface, molecular forces, in effect, stick the fly to the surface and keep it there. There are really micro suction pads on the bottom of their feet.

Staying on the ceiling is a balancing act between the pads being so sticky that the fly can’t release from the surface, and not sticky enough to hold the fly up. But luckily for the fly, it is light enough not to need a very strong glue, and, along with the action of the pads, its walking and flying strength can break the bonds with the ceiling when it wants to move its feet. The system works well enough that many insects use it. It is a pretty common strategy.

As well as walking on the ceiling, a fly has to get there in the first place. How it does that is an interesting question that was solved a number of years ago using high-speed photography. Flying upside down is a bit of a trick. You might think that flies would do a barrel roll like an airplane, so they would first turn upside down and then land on the ceiling. But if they’re upside down, both their wing action and gravity are pulling them down, so flies have developed a different strategy. As a fly gets close to the ceiling, it flies in at an upward angle, and then touches its front feet to the surface. When the front feet touch down, the fly’s momentum pivots it over its front feet and it flips over to land upside down. It is like a trapeze artist with his hands on the bar, whose feet flip up at the highest point in the arc.

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Lost at “c”

If one were to travel vast interstellar distances at a rate faster than the speed of light, would we be able to see much along the way?

Dr. Ann Gower, Professor of Physics and Astronomy at the University of Victoria:

According to the laws of physics, as we understand them, it is not possible for us to travel at the speed of light, let alone faster, so there isn’t really an answer to this question. What can be answered is what you would see if you travelled through the galaxy at very close to the speed of light.

First of all, looking out the front window, any light from stars in front of you would be shifted to shorter wavelengths, or blue-shifted, because you’re moving so fast. If you were going very fast indeed, really close to the speed of light, the light would be shifted out of the visible range completely, into the X-ray or gamma-ray wavelengths. Very high energy radiation would be hitting you very hard from straight ahead. It would be really dangerous, and you would likely be baked!

But whereas the light from stars in front of the ship would be blue-shifted, the opposite would happen behind you. The light from those stars would be red-shifted to longer wavelengths. These would be below our visible range, right down into radio wavelengths, so they would be invisible to the naked eye. This means the sky behind us would be dark, without much to see.

When you looked out the sides of the ship, you would also see very little. There is a very dramatic effect on the geometry of space, due to relativity, when you travel close to light speed. If you’re going very fast, the stars will appear to be bunched close together in front of you. Everything will be compressed into a cone ahead of you, in the direction you’re moving. It is rather like driving in a shower of rain. When you drive through a rainstorm, it looks as though all the drops are coming from the front. The same effect would happen in a spaceship as you approached the speed of light, but it would be much more extreme. All the stars would appear to be in front of you. So you’re not going to see much out of the side windows.

Light waves aren’t the only thing affected by travelling close to the speed of light. The universe is filled with cosmic background radiation, left over from the Big Bang. Like the light, the energy from the cosmic radiation would appear blue-shifted in front of the ship, making it much hotter and more energetic. It would become another source of X-rays raining down on the ship. Added to the light from the stars, it would create a very high energy situation!

Another form of energy, which we know must exist throughout the universe, is gravity waves. We haven’t yet detected them, but we know they are there. These will also be intensified. As you travel closer to the speed of light, you would feel them as stronger and stronger bumps. So, even if you survive being baked by the shifted starlight and background radiation, you are liable also to be shaken violently by intensified gravity waves. Perhaps we could call it “shake and bake” travel!