[SCI]The Universe is 13.73 +/- .12 billion years old!

[Fredfredson]

Check the original for links and images!

The Universe is 13.73 +/- .12 billion years old!

Posted at 6:12 pm in Astronomy, Cool stuff, NASA, Science

http://www.badastronomy.com/bablog/2...ion-years-old/

Happy birthday, Universe!

Kinda. It’s not really the Universe’s birthday, but now we do know to high accuracy just how old it is.

How?

NASA’s WMAP is the Wilkinson Microwave Anisotropy Probe (which is a mouthful, and why we just call it WMAP). It was designed to map the Universe with exquisite precision, detecting microwaves coming from the most distant source there is: the cooling fireball of the Big Bang itself.

WMAP image of the sky in microwaves; the cooling fireball of the Big Bang

New results just released from WMAP have nailed down lots of cool stuff — literally — about the Universe.

I am about to explain the early Universe to you. I’ll be brief, but if you want to skip to the results, then go ahead.

Here’s the quick version: the Big Bang was hot. The Universe itself expanded outward from a single point — actually, it’s space itself that expands, not the objects in it — and like any expanding gas it cooled. After about a microsecond, it had cooled enough for protons and neutrons to form. Three minutes later (yes, just three minutes) it had cooled enough for protons and neutrons to stick together. Hydrogen, helium, and just a dash of lithium were created, and these would be the only elements for some time (hundreds of millions of years, in fact). The Universe was a thick soup of matter and energy.

It kept expanding and cooling. At this point, it was opaque to light. A photon couldn’t travel an inch without smacking into an electron and then getting sent off in some other random direction. However, after a few hundred thousand years, an amazing thing happened: neutral hydrogen could form. Before this point, the Universe was still too hot; as soon as an electron bonded with a proton, some ultraviolet photon would come along and whack it off. But at that golden moment the cosmos had cooled off enough that a lasting atomic relationship was in the offing. Neutral hydrogen was born. At that moment — astronomers call it recombination, which is a misnomer, since it was the first time electrons and protons could combine — the Universe became transparent; without all those pesky electrons floating around, photons found themselves free to travel long distances.

It’s those photons WMAP sees. After 13.7 billion years, the expansion of the Universe has cooled the light, stretched its wavelength from ultraviolet to microwave. Another way to think about it is that the temperature associated with each photon went from thousands of Kelvins down to just a few, less than 3, in fact. That’s -270 Celsius, and -454 Fahrenheit.

Brrrr.

That light emitted just after recombination tells us a vast amount about the Universe at that time. By carefully mapping the exact wavelength of the light and the direction from where it came, we can tell the density and temperature of the matter at that time. Incredibly we can also tell how much dark energy there was, and even the geometry of the Universe: whether it is flat, open, or closed.

All this, from the dying glow of the Big Bang itself.

WMAP Results

A lot of this information was determined a while back, just a couple of years after WMAP launched. But now they have released the Five Year Data, a comprehensive analysis of what all that data means. Here’s a quick rundown:

1) The age of the Universe is 13.73 billion years, plus or minus 120 million years. Some people might say it doesn’t look a day over 6000 years. They’re wrong.

2) The image above shows the temperature difference between different parts of the sky. Red is hotter, blue is cooler. However, the difference is incredibly small: the entire temperature range from cold to hot is only 0.0002 degrees Celsius. The average temperature is 2.725 Kelvin, so you’re seeing temperatures from 2.7248 to 2.7252 Kelvins.

3) The age of the Universe when recombination occurred was 375,938 years, +/- about 3100 years. Wow.

4) The Universe is flat.

5) The energy budget of the Universe is the total amount of energy and matter in the whole cosmos added up. Together with some other observations, WMAP has been able to determine just how much of that budget is occupied by dark energy, dark matter, and normal matter. What they got was: the Universe is 72.1% dark energy, 23.3% dark matter, and 4.62% normal matter. You read that right: everything you can see, taste, hear, touch, just sense in any way… is less than 5% of the whole Universe.

We occupy a razor thin slice of reality.

There are other important things that have come from the WMAP data, and if you’re interested, you can read all about them on the WMAP site and in the professional journal papers.

But if you only want to peruse the results I’ve highlighted here, that’s fine too. But remember this, and remember it well: you are living in a unique time. For the first time in all of human history, we can look up at the sky, and when it looks back down on us it reveals its secrets. We are the very first humans to be able to do this… and we have the entire future of the Universe ahead of us.

[Francois Cellier]

Originally Posted by Fredfredson

4) The Universe is flat.

This is a highly interesting story. Thanks for sharing it, Fred. I predict a Nobel prize in physics is in the wings.

The most interesting statement is the one outlined above: The Universe is flat.

What does this mean? Let me offer an analogy. You throw a stone up into the air. If you don't throw hard enough, the stone will decelerate, come to a standstill, and then fall again back to the ground. If you throw harder, you may be able to overcome the gravity pull of planet Earth, and the stone may leave the gravity well of Earth forever. After overcoming gravity, it will still have a remaining velocity > 0. Between these two scenarios, there is a borderline case: the stone has enough energy to overcome gravity, but by the time it does so, its remaining energy has become exactly zero.

Until now, the question has remained unanswered, whether the energy of the Big Bang is sufficient to overcome the gravitational pull of the universe. If it is, the universe will expand forever, and we live in an "open" universe that will continue to cool down and expand forever. If it isn't, expansion will eventually end, and the universe will start contracting itself again due to its own gravitational pull. The universe will heat up again and "end" in a big collapse. We then live in a "closed" universe.

Until now, different types of experiments, i.e., different types of measurements, have produced conflicting results. Some suggested that the universe is open, whereas others suggested that it is closed. Yet, all these measurements were characterized by a sufficiently large margin of uncertainty to make them inconclusive. It all depended on the amount of dark matter (and dark energy) in the universe that we were unable to estimate well enough to make our case for us.

I have suspected for a long time that the final answer would be neither nor, i.e., that the universe is flat, i.e., that there is exactly as much dark matter in the universe to eventually end its expansion without making it contract. It just seemed to be too much of an accident that the answer should be as close to this borderline value to be an accident at all. In my own belief system (you may call it religion), there had to be a plan (whatever that may mean) that the universe was supposed to be flat ... and the new measurements now indicate more clearly than ever that this is indeed the case.

Why is the universe flat? That question hasn't been answered by the new measurements, but surely, this will be the most important question that the next generation of physicists will have to ponder.