Theories of the Universe

Jezen Thomas

F5C

There are many theories on the topic of ‘everything’, but as physicists are simple folk they can only settle for one simple answer. Just one.

Most theoretical physicists have believed that, ultimately, there must be just one possible universe, the physical manifestation of a set of laws so compelling that no other option would be viable. One universe. One theory. One defining way.

It was a lovely idea, but increasingly it seems a fantasy. In recent years, theory and experiment are leading to the conclusion that, far from being the only option, our universe may be just one among an almost infinite array of possible worlds. It may be that ours is simply one member of a vast cosmological swarm.

Several paths seem to be leading in this direction. The most notable is string theory, which is the leading contender for a so-called theory of everything. Many physicists are convinced that some version of string theory will prove to be the final description of all physical reality, unification under one mathematical umbrella of matter, force, space and time.

As the name so charmingly implies, string theory proposes that, at its core, the universe is composed of minute strings. To get a sense of what this means, imagine a subatomic particle as a tiny point; now further imagine that, as you look closer, this point turns out to be a tiny closed loop, not a simple point but a minute circle. According to string theory, everything in the universe can be explained in terms of these microscopic loops or strings.

The trouble is that there are many versions of the string theory equations. Making matters worse, each version allows for many solutions. Physicist Joseph Polchinski has recently estimated that there may be as many as 10 to the power of 60 solutions to these equations, and every solution represents a different possible universe. That's a million billion billion billion billion billion billion potential universes. To put this into perspective, there are about 400 billion stars in our galaxy.
Figures like this are difficult enough to grasp when talking about individual stars, but when talking about entire universes they are beyond comprehension.

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The idea that there might be more than one universe actually dates back to early last century when Albert Einstein proposed his General Theory of Relativity. General relativity describes the large-scale structure of the cosmos and any theory of everything will have to incorporate its insights.

Like string theory, general relativity is a set of equations that admits many solutions - and, again, every solution describes a different possible universe. One of the major problems in cosmology over the past century has been trying to determine which version of the Einsteinian solution fits our particular universe.

Many physicists had hoped that, eventually, one solution would emerge as a natural winner, but with the advent of string theory the problem has only compounded. Today, most physicists admit they are suffering a bad case of cosmological overload.

Which one of these potential universes do we actually live in? Polchinski says it is not clear if there will ever be enough data to sift through all the possibilities. He says, however, that understanding our universe is not a lost cause. It is just that it might simply take physicists a very long time to fathom it out. He notes that physics itself is a continually evolving science that is regularly invigorated with radical new ideas and mathematical tools.

String theory itself is a prime example, having been invented only about 20 years ago. In the next 50 years, Polchinski expects there to be at least two conceptual revolutions that should help to sort through the morass.

Armed with this information I decided to try and think of my own little theory. I failed at an actual theory of the creation of the universe, however in the process I got into a very nice debate with some friends about the concept of light.

It started with people discussing what ‘white’ is. Some thought of it as a colour. Some thought of it as all colours combined. I intervened and said that that is only when ‘white light’ is refracted. Then people started talking about the opposites of light, and there were some good answers and some not so good ones.

Debater 1: Nothing but space is dark as everything gives off light.

Debater 2: We're talking about visible light here, so dark is the absence of light. This got me thinking. What is light? Light is an electromagnetic wave of positively charged photons. So surely the opposite of light is a wave of negatively charged photons? Anti-Light.

Me: Light is made from waves of photons. Darkness is not made of anti-photons or whatever. If there were, then we could shoot rays of darkness, and also make the opposite of a shadow. Also, there would have to be a third factor. Transparency? Doubtful. I would like to see a transparent universe. Then perhaps we could see what is beyond our universe, IF our eyes could see that distance. Which they can't.

Debater 2: That argument would work, but the opposite of light is not dark. Dark is merely the absence of light. Light is a collection of positively charged photons. Therefore theoretically negatively charged photons could exist, hence anti-light.

Commenter: Hah, 'Anti-Light'.

It's like something out of 'Star Wars'...

Me: Dark is the opposite of light, because that’s all the human mind can comprehend it as. It isn't seen as space.

At that point, the argument kind of dissipated. My conclusion is that darkness is often seen as space, because there is nothing in place of the darkness. I figured that darkness is simply the three dimensional canvas onto which the universe is portrayed. There is no energy, hence no ‘light’. People often get confused with darkness, because in space there is an abundance of darkness, and therefore see the lowest possible light level (not including anything fancy that can suck light from something) as measurements from both scales of light level AND volume. Why does it have to be so confusing? In the end physicists are only simple folk…

Peer Reviews

Here's what a star student thought of this essay

pictureperfect

8th of Jul 2012

Quality of writing

The candidate discusses scientific concepts accurately, they have used a good range of vocabulary and there are no grammatical or spelling errors. However the candidate has included dialogue between themselves and their friends this has no real purpose and actually detracts from the essay. You should discuss your own ideas and opinions but adding in what seems to be an unrelated conversation between friends is inappropriate and meaningless.

Level of analysis

The candidate seems to have a good understanding of the theories they have discussed and they have given a great deal of detail especially relating to string theory. For this topic in particular I feel that candidate has made a good attempt at keeping the information simple, making it easier to read and to understand. In addition, the candidate makes a good attempt to conclude this essay, they give personal opinions and manage to link back to their introduction, which is a nice way to draw an essay to a close. However they should have summarised their key points, stating their importance, as this helps you write a final statement linking to your essay title.

Response to question

The candidate gives a reasonably in depth response but it lacks balance, the topic is to discuss theories of the universe yet the candidate fails to mention the hot big bang model, which is the current scientific explanation for how the universe begin. In addition to this the candidate’s response seems to trail off and in the end its not clear what the essay is about. It is often useful to write out a rough plan before beginning an essay, this allows you to think about the topics you wish to discuss and this can help you stay on track and give a clear and balanced account.

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