Probing the Very Early Universe (Part III)

Apologies for the delay in this post, I had started writing this ages ago, it was taking me forever to get the images right, and when I thought I was done, I lost both the post and the images!! I lost the will to live.

Catch up with the saga: part I, part II

A Neat Solution, Inflation

In the early 1980s, physicists started to take note of a theory that seemed to hold all the answers. The theory, cutely called ‘Inflation’ by MITs Alan Guth, offers a neat solutions to The Three Paradoxes of the Universe. In this post I will attempt to explain what inflation is, when it happened, and how it works.

What is Inflation?

Inflation is basically the very rapid expansion of the universe, where two points move away from each other at the speed of light(1). This does not contradict the special theory of relativity, since at the time this happened, the universe was classically empty, only energy existed at this time.

When did it happen?

Hard to quantify too precisely, but we can take on board two bits of information from two different sources in order to give a ball-park figure on this. Inflation must obey the physical laws of nature, there is no escape, however we are not entirely sure what these laws looked like such a long time ago.

[Extra Reading] The origin of the fundamental laws of physics:

One of the fundamental ideas of physics is that all the physical forces that we see as independent today (i.e. the force of gravity is seen as independent of say the theory of electromagnetism), were actually all ‘united’ many years ago, when the energy of the universe was ‘free’ (i.e. not bounded by structure, like atoms and such). That is, billions of years ago, physicists think only one law of nature existed, and that as the universe grew and cooled, this one law subdivided into a few sub-laws of nature. If you’re a bioligist or are more comfortable with the ideas of biology, think of this evolution as a top down process, as opposed to biology’s bottom up approach to evolution. So if a physicist had come up with a theory for the origin and diversity of the species she would have imagined one super-being (not divine, just super, as in ‘super duper’) that then spawned lots of other species, who then spawned even more species! But this spawning of mutants was already encoded in the first super-being, i.e. all the DNA any animal/plant needed existed within the chromosomes of that first super-being, and the genes ‘came to life’ as it were in response to the environment. That is the basic idea of the unification and subsequent diversification of the laws of physics, with the environment being the temperature/size of the universe.

Now, the physics world has managed to unite all the fundamental forces… except for one: Gravity. But that is not what we’re talking about, we assume that gravity did somehow unite with the other forces, and generally, gravity appears after what is known as the Planck epoch. The Planck epoch defines a time when the early universe was only a Planck length in diameter. This Planck length is special, in that it defines the smallest size that we know how to analyse physically i.e. we have a theory of how things behave when they are very small, or very very close together, but not if they measure less than or are closer than a Planck length. Since inflation deals with the expansion of space time, it needs general relativity (aka gravity) in order to operate, so Inflation takes place after the appearance of gravity.

So as a first guess Inflation takes place at least billion billion billion billionth of a second after the Big Bang. But to be brutally honest, since the theory of inflation is still work on progress, then inflationary cosmologists also look at scenarios when inflation took place at or before the Plank time, that is: less than 10 million billion billion billion billionth of a second after the Big Bang.

The second bit of information we need is when did the contents of the Universe become dominated by radiation? That occurred about a 10 millionth of a second after the Big Bang, and we need the universe to have ‘settled down’ by this time, because our theories of what happened after this time (the `standard’ Big Bang evolution) hold up pretty well under scrutiny, and we dont want to change things too much.

So inflation took place between a billion billion billion billionth of second after the big bang and 10 millionth of a second after the Big Bang. This would seem pretty precise for most people, but remember in the early universe aLOT of stuff could have happened within this time, after the universe became radiation dominated it took only 3 minutes for the temperature to drop 999,999,999,999,999,999,900,000,000 degrees Celsius. So we may have nailed the epoch of inflation to a few millionth of a second, but that still leaves alot of room for uncertainty.

 

How does it work? i.e. how does it solve the Three Paradoxes of Cosmology

How inflation explains the causality, homogeneity and isotropy of the universe?

This is a schematic diagram of the expansion of the universe. The figure on the left represents the standard big bang expansion, assuming only radiation and matter. The figure on the right represents big bang + inflation. To understand this diagram, you need to imagine that our universe is contained within the black lines, and that it grows as you follow the arrows.

Looking at the figure I have included (click on it for a better view), I have attempted to illustrate how the two different scenarios (Standard Big Bang vs. Inflation and Big Bang) expand. You need to imagine that our universe is contained within the two vertical black lines, so it grows as you follow the arrows.  Now, what we know of the age of the universe, and what we know about how radiation and matter (regular stuff) effect the rate of expansion, then it turns out that there were 50,000 parts of the universe not in causal contact. That is, the universe could not have been small enough for these parts to communicate. That is, 14 billion(ish) years ago, according to standard lore, the universe was made up of 50,000 independent regions. So why did these regions all evolve in the same way?

This is where inflation comes in, because inflation stretches the universe out in such a tiny amount of time (see previous section), it means that the universe could have started out much smaller than was actually thought, and expanded very quickly, all this without effecting the evolution of the universe from light to atoms to galaxies to us (i.e. Big Bang Nucleosynthesis). Referring back to the figure, the red and blue circles represent two regions in the universe, in the inflationary picture they start off very close to each other, so information gets shared between them, or more to the point the universe mixes and homogenizes. 

How does it solve the problem of the age of the universe? (or why isn’t it older?)

Since inflation causes the universe to grow to the size required by the theories which govern Big Bang Nucleosynthesis in a teeny fraction of a second, our theory of universal evolution now accounts for the age of the universe. We no longer need to add to the age of the universe to account for phenomena.

How does it solve the origin of structure? (or where did all this stuff come from?)

The answer to this one is quite involved, we need to look at how one gets inflation, i.e. what causes the universe to expand so rapidly? Once we answer this question, we discover that inflation also explains the origin of structure AND why it started expanding in the first place.. for next time though 🙂

(1)this is one scenario, but the other one is too complicated to explain right now

Next up: Negative pressure, exotic particles, and the emergence of something out of nothing

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The Muhammed Institute for Science of the Cosmos

Cosmology may be coming to an institution near you. The Middle East is surprisingly uninterested in cosmology, even though we have at least one eminent cosmologist that I know of (Qaisar Shafii from Egypt), cosmology has failed to take root in the academic institutions in the region. This I always found surprising, for research into theoretical cosmology is cheap to fund, all we need is a computer with an internet connection, and a supply of paper, pencils and erasers. I also find that arabs are very curious about cosmology, most arabs I meet quizz me about the Big Bang theory, the origins of the universe and such. Stephen Hawking was met with a huge crowd when he visited the university of Birzeit in 2006, yet the Centre for Excellence in Theoretical Physics and Applied Mathematics due to be built with EU funds sometime in the future do not have cosmology on their list of research aims (in fairness though they were very open to the idea of possibly including it). Apparently attempts to establish cosmology research groups in Lebanon, Egypt and Morroco have failed, due to apathy, and lack of a conducive research environment. This was a wakeup call to me, I had always thought that moving back to the Middle East and establishing such research would be a doddle. I do find it surprising on another level, since the Middle East is predominantly Muslim (except Lebanon, but even there we make up 50% of the population!), and the Quran strongly urges “looking up at the stars and pondering their origins” (c.f. Aal Imraan verse 191 + many more).

As a result of these unpromising experiences Dr Al Fakir has established the Muhammed Institute for Science of the Cosmos (MISC) and they have just launched their website.

WHAT THE MISC DOES
The end product of MISC operations are substantial advances in astrophysics, cosmology, and space exploration, in the form of scientific papers in internationally recognised refereed journals, and collaborative experimental projects. To that end, MISC activities include (1) organising annual conferences brining together the MISC research community at large, (2) supporting specific research collaborations between groups of MISC researchers, (3) supporting senior researchers in dedicating extended stretches of time to the MISC, (4) planning and promoting Earth-based and space-born experiments that have bearing either on the physics of the Universe (gravitation, microwave background, etc) or on the origin of life (solar system exobiology, astrobiology, etc), (5) creating and nurturing branches of the MISC in various parts of the Muslim world, (6) creating opportunities for promising young researchers from the Muslim world to collaborate with seasoned MISC researchers.

Of particular interest is the list of eminent non-muslim cosmologists who support the institute, Alexander Vilenkin, Robert Wald and William Unruh, which I find extremely promising. Eventually they plan on being able to fund visits to institutions in the Muslim world with a resident cosmologist, or visits from cosmologists based in the Muslim world, with the possibility of funding postdoctoral and permanent staff members. The potential increase in job opportunities aside (something of extreme interest to someone at my level), this will be great for the middle east (and muslim world as a whole) on many levels. It will foster creativity and ‘outside the box thinkin’, something I find to be lacking in the arab countries at least, interaction with experienced cosmologists, and the potential in excelling in something other than conflict and commerce (as in the UAE). The Muslim world has a strong history in Astronomy (see 1001 Muslim Inventions and George Saliba’s site for a summary), that even though we managed to severley neglect, makes us naturally disposed to this branch of science and we really should foster it once more.