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Biggest Bang

Welcome to the -EST blog! Here we’ll chat about some of the awesome astronomical superlatives that exist in our universe – biggest, smallest, brightest, coldest, densest, and whatever else we come up with.

As this is my first -EST blog, I thought it would make sense to start with something that is a natural beginning – how about THE beginning? Let’s try to tackle the biggest bang. The Big Bang is theorized to have been the biggest bang in the history of the universe, also the one that created the universe. The Big Bang and early development of the universe is a hugely complex subject, so this is going to be a somewhat brief-ish overview and not designed to cover every explicit detail.

Time Line of the Universe
Credit: NASA

The Big Bang theory is the prevailing cosmological model for explaining the very early history and development of the universe (everything that follows will be according to this model and others like it). The theory goes that about 13.7 billion years ago, our entire universe only took up a space the size of an atom’s nucleus, which is what you get if you run the clock backwards in time to as close to the beginning of the universe as we can know. In the most common models, the very small, very hot, very dense universe was pretty uniform and was expanding and cooling VERY quickly. At about 10-37 seconds, the universe went through a phase known as inflation, during which the universe expanded exponentially (faster than it had been before).

After this inflation stopped, the universe was still too hot for even protons and neutrons to form, but the particles that make them up do exist by now. So the universe is now a seething hot soup made of these particles – electrons and quarks. After about 10-11 seconds the picture becomes clearer because the particle energies can be reached experimentally (and keep in mind now that we’ve already gone from 10-37 seconds to 10-11 seconds… a very, very small fraction of the time it takes to blink an eye, and we haven’t even created protons yet). Around a thousandth of a second (10-3 seconds) the universe has cooled enough to allow protons and neutrons to form. At this point, with all these charged particles flying around, the light can’t shine, leaving the universe as a super hot fog.

After about 3 minutes, these protons and neutrons are cool enough to form atomic nuclei. It then takes a much longer jump, about 380,000 years, for the universe to cool enough for the electrons to settle down with the nuclei to form atoms – about 75% of the stuff in the whole universe is now hydrogen and about 25% is helium. Once electrons and nuclei combined to form atoms, the light that filled the early universe was free to move out through space without running into as many free electrons and protons. We can still see the leftovers of this light today – it’s called the Cosmic Microwave Background radiation (CMB for short).

We then enter the much longer time period on our universe’s history where slightly denser gas clouds begin to collapse and eventually lead to the first stars and galaxies. Billions of years then go by and our universe evolved into what it is today.

I had the opportunity to talk with Dr. Alan Kogut Ph.D., a scientist here at Goddard, who is studying the cosmic microwave background for clues about the early universe. Dr. Kogut told me about all the information that is buried in the CMB, what it could tell us, and why it’s so important. According to Dr. Kogut, the CMB is a remarkable piece of evidence that tells us that the current theory of inflation in the early universe seems to be pretty spot on.

Credit NASA / WMAP Science Team

When you look at a picture of the CMB, like the one above, it looks like a jumble of colors. But buried within this cosmic kaleidoscope are many pieces of evidence that can tell us much about what our early universe looked like. What you are actually looking at are super tiny temperature fluctuations from when the universe was only 380,000 years old. These temperature fluctuations have told us several things already and most likely hold even more secrets. For example, the sizes of the temperature fluctuations have told us that our universe is flat, on a grand scale (this is a strange concept to think about in more than two dimensions but tells us a lot about the probable fate of our universe as well). This is one spot where the inflation model comes in – it predicts this flatness and the temperature background. The universe is, on average, glowing at 2.7 Kelvin (-270 Celsius, -455 Fahrenheit), but why that temperature? Why should the universe be that uniform? Dr. Kogut explained this with a cool analogy. Imagine a giant kick line on a stage, if there are only five dancers it would be pretty easy for those five to be synchronized with each other and kicking at the same time. Now imagine there are one hundred dancers on a huge stage – the two ends are much farther apart so it would be more likely that they would not be kicking in sync with one another. Expand this to a kick line the size of the universe and it would seem almost impossible that the line could be synced up. Inflation, however, has an answer for this – it is like the entire kick line started much closer together and then spread out quickly. If all of the dancers started together it’s more likely that they would be able to remain in sync with one another, much like the fairly even temperature of the CMB.

So that’s cool, the CMB light can tell us about the early universe. But so what? That was 13.7 billion years ago, right? Why should that matter to people today? Why should we continue to study something that happened so long ago? There are a couple reasons. For the practically minded – those who are looking for tangible technological development – science has a way of producing technological advancements on the side. In the quest for a better way to detect a certain kind of wave, say, scientists might produce a new and better antenna that can be used for communications. The quest for knowledge can lead to scientific advancements naturally. On the other hand, there’s the quest for knowledge itself! It’s part of human nature to be interested in our past and where we came from. Some of us can remember things from 15 years ago, other (older) people might be able to remember things from 50 years ago. Studying the light from the early universe is like looking back in time to BILLIONS of years ago! I don’t know about most people, but I have a hard time wrapping my brain around that many years of history. For me and many scientists who have made this their focus of study, like Dr. Kogut, the intellectual curiosity that drives us to pursue that knowledge is reason enough.

Thanks for checking out the biggest bang, and check back soon for my next post where I’ll tackle one of the brightest things in our universe!

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