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Timeline of Natural History - Part 1

June 4, 2008 on 9:49 am | In big bang, cosmology | 25 Comments

Sometimes people ask me what I do, and if I’m being completely honest, I’ll tell them I’m a cosmologist. When they ask for more details (because it isn’t hair, nails, and makeup), I tell them that I study the Universe, and try to figure out and understand the story of how we came to live in the world we live in here and now. Then they either smirk and ask, “Is that all,” or tell me that we already know this, and they saw it on PBS.

But I think you might enjoy hearing the most up-to-date version of the story that we have. So, dear readers, I present to you the most accurate timeline ever composed of what has happened in the Universe to bring us to the present day, and telling you the age of the Universe at that time. I’ll do this in three parts, and so today I bring you part 1, from inflation to the first stars:

  1. 10-35 seconds: The Universe expands exponentially fast, stretching space to make it flat and giving it the same properties everywhere. We call this inflation.

  2. 10-30 seconds: Inflation ends, and all the energy that was stored in space, causing the exponential expansion now becomes an incredibly dense bath of hot particles of matter, anti-matter, and radiation. The birth of all the energy in what we know as our Universe is what we call the Big Bang.

  3. Somewhere between 10-30 and 10-10 seconds: natural processes create slightly more matter than anti-matter in the Universe. Even though there is only one extra matter particle for every one billion pairs of matter-antimatter particles, that’s enough to explain all the matter in the Universe today. We call this process baryogenesis.

  4. 3 minutes: After all the antimatter annihilates away with the matter, there’s a little bit of matter left over in a sea of radiation. At three minutes, the Universe cools enough so that protons and neutrons can fuse together to form heavier nuclei without being blasted apart. This is where nearly all the hydrogen, deuterium, helium, and lithium in the Universe is created. (Most of it is hydrogen, about 75%, and most of the rest is helium, about 25%. The rest is less than 0.01%.) We call this part Big Bang Nucleosynthesis.

  5. 380,000 years: The first neutral atoms form. Up until this point, all of the radiation energy in the Universe has been too cold to blast the nuclei of atoms apart, but that energy has also been too hot to allow neutral atoms to form. It takes almost 400,000 years for the Universe to expand and cool enough for the leftover radiation from the Big Bang to chill out. Finally, at this point, electrons and nuclei can meet to form neutral atoms. When this happens, that leftover radiation simply flies off in all directions; this is what we see as the Cosmic Microwave Background.

  6. 50 Million Years: The first stars in the Universe begin to form. It takes about 50 million years for gravity to collapse matter into volumes that are dense enough and massive enough to ignite nuclear fusion. These first stars are huge, hundreds or even thousands of times as massive as our Sun, and are responsible for creating many of the heavy elements and metals that our Universe has today. These stars will all die as supernovae or even hypernovae, and will blast their remnants all over the Universe.

Come back tomorrow for Part 2, where we’ll walk through the formation of galaxies to the creation of Earth and our Solar System!

Astronomers make use of… molecules?

May 14, 2008 on 10:42 am | In Astronomy, big bang | 3 Comments

When I think of molecules, I think of Conan O’Brien doing his skit where he plays Moleculo…

the molecular man! I don’t think of astronomy, and I certainly don’t think of the leftover radiation from the big bang (known as the cosmic microwave background)! But somebody over at the European Southern Observatory put these two together and made an incredibly tasty science sandwich.

See, we can measure the cosmic microwave background today, because we have photons (particles of light) coming at us in all directions at all locations, with a temperature of 2.725 Kelvin. Theoretical cosmology tells us that when the Universe was younger, it was also smaller. Because the expansion of space stretches the photons in it, causing them to lose energy, it means that photons were hotter when the Universe was younger.

But we’ve never been able to measure that, of course. After all, how can you measure the temperature of something in a place where you aren’t? (Hint: read the title of this post.) Use molecules as thermometers! Using a carbon monoxide molecule (CO to you chemists) in a distant galaxy, they were able to measure the temperature of the microwave background when the Universe was only about 3 billion years old! The temperature they measured was 9.15 +/- 0.70 Kelvins; and this compares pretty well with the predicted temperature of 9.315 Kelvin. Not bad! Here’s an incomprehensible graph for you to look at while you take it all in:

What’s nice about this is that, even though it’s just what we expected, it rules out or constraints a lot of crazy alternatives (such as theories where the fundamental constants vary), because the temperature of the microwave background evolves according to standard theoretical predictions. Here’s a link to the actual scientific paper, if you’re into that sort of thing.

By the way, while I’ve got you thinking about astronomy, NASA just announced that their X-ray satellite, Chandra, found a supernova in our own galaxy that went off in the 1800’s, making it the most recent supernova ever to occur in our galaxy! Why’d it take so long to find? Because the whole damned galaxy was in the way: the explosion happened on the opposite side!

How “Quantum” is the Big Bang?

May 13, 2008 on 11:36 am | In Quantum, Scientific papers, big bang | 12 Comments

There is a very techincal paper this morning by Martin Bojowald that asks the question, How Quantum Is The Big Bang? Let me break it down for you.

If you took a look at empty space and zoomed in on it, looking at spaces so small that they made a proton look like a basketball, you’d find that space wasn’t so empty after all, but was filled with stuff like this:

What are these? They’re little pairs of matter particles and anti-matter particles. They spontaneously get created, live for a brief fraction of a second, and then run into each other and disappear. That’s what happens on very small scales, in the quantum world. (This is known as the Heisenberg Uncertainty Principle, and it actually happens!)

Well, the Universe today is huge. But it wasn’t always; back when the Big Bang was happening, all the matter and energy in the Universe was concentrated into a volume so small that these quantum effects were important!

So now, we can ask the question: how important were these quantum effects at the time of the Big Bang? (FYI: this is talking about what happens at a singularity, so this is even before inflation!) And what he basically found is that at these super-high densities, you start to run into something very interesting. Remember the Pauli Exclusion Principle? It says that no two fermions (e.g., protons, neutrons, or electrons) can occupy the same quantum state. You put all the matter in the Universe into a small enough volume, and you wind up “squeezing” everything together!

And what he found, as best as I understand it, is that the quantum state of whatever’s in the Universe determines what type of Big Bang you get! Is it the same in all directions? Well, that depends on what the quantum state of the Universe is. Will it start expanding, contracting, or oscillating? Again, depends on the quantum state. We don’t know what that state is, especially in the context of inflation (which might wipe out all of that information), but this is what they’re trying to figure out! No definitive answers yet, but at least the quantum gravity people have gotten to the point where they can start to ask this question!

How to Destroy the Entire Universe

April 23, 2008 on 8:49 am | In big bang, inflation | 31 Comments

Since the dawn of time man has yearned to destroy the sun. - C. M. Burns

There’s no need to stop at the Sun, though. Since yesterday was Earth day, I thought it was only appropriate to spend today telling you how not only to destroy the Earth, but to effectively destroy the entire Universe. To tell you this story, we have to go all the way back to the beginning, to just before the big bang.

The big bang was when the Universe was hot, dense, full of energy, and expanding very quickly. The Universe was also spatially flat and the same temperature everywhere, and full of both matter and antimatter. It may have looked something like this:

(Image credit: Stephen Van Vuuren, created from a simulation of 80,000 star images.) The thing is, we need something to make the Universe this way; we need something to set up the big bang. What makes the Universe flat? What forces the Universe to be the same temperature everywhere? What creates the fluctuations that allow stars, galaxies, and clusters to form from gravitational collapse? What pushes all the weird stuff that might have existed before the big bang away?

The best theory is cosmic inflation, or a theory that says that the Universe went through a period where space expanded exponentially fast. That expansion pushes everything that existed before away, removing it from what we know as our Universe. It takes whatever shape space is and stretches it flat. It takes a small, uniform area and stretches it, giving every point in our Universe the same temperature. And it takes tiny, quantum-scale fluctuations and stretches them across the Universe, creating those fluctuations that allow the formation of stars, galaxies, and clusters. It even gave the correct predictions for the amplitude and spectrum of those fluctuations, more than a decade before we were able to measure them!

So to destroy the Universe, all we have to do is make one tiny point near us expand exponentially fast again, even just for a tiny fraction of a second (~ 10-30 seconds), and that will remove everything we know of entirely, creating a new Universe in its wake. Kind of like a Phoenix (left).

Some of you may object. You may say that it’s wrong to do this; that this would be playing God. Look, people, if you want to destroy the Universe, there are some things you’re just going to have to suck up.

So how do we do this? In some sense, it’s as simple as pushing a ball up a hill; you just need enough energy. All we have to do is make the particle that causes inflation, called an inflaton, with enough energy to make the Universe inflate again. For instance, if we made an inflaton at the low energies we’re used to in big accelerators (you know, like 1012 Electron-Volts), we couldn’t get it out of the bottom of the valley that it’s stuck in, like this:

In fact, supermassive black holes produce cosmic rays that are about 1020 Electron-Volts, so we know we need more energy than that. But if we can get up to about 1026 Electron-Volts, we’re sure to do it. “Do it” means push that inflaton up the hill; push it up high enough, and you get inflation! And that’s how you destroy the Universe!

All you need is a bigger particle accelerator or stronger magnetic fields. We can get up to 1012 eV with a ring with 4 Tesla magnets and about a 1 km radius. So we’d really need a ring with a 1014 km radius (and the same magnetic field) to do this, or an accelerator ring about the radius of our distance to the nearest star. So support your particle physics research and the development of stronger magnetic fields, otherwise we’ll be doomed to celebrate many more Earth days!

Interesting note: Some of you were upset by my post that said string theory is untestable in principle. All you have to do is build a powerful enough accelerator. Guess what, the energy it takes to destroy the Universe like this is less than the energy it takes to test string theory (which is 1028 Electron-Volts). Have a nice day!

Genesis Teaser Trailer is Up!

April 18, 2008 on 2:05 am | In Video, big bang | 3 Comments

What is the future of this website? I’m going to be creating videos for the web about the Universe. I’ll be answering questions ranging from what the Universe is like today to how it got to be that way. I’m going to address every step that we know of, from the Big Bang up to the present day.

And I’m going to do it naturally, by telling the story as the Universe tells it directly to us. I call this project Genesis. Check out the teaser trailer below, and tell your friends, because this is coming in January.

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