Space: Who Knew, #12

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Absolute Zero

Today's rant will be on Absolute Zero.

So what is Absolute Zero anyways? If we were to convert it to Fahrenheit, the Absolute Zero wouldn't be zero at all- it'd be a staggering -459.67 degrees. Nor would it be zero if we converted it to Celsius, Absolute Zero would still be -273.15 degrees. Now that's somewhat chilly!

So in what system is Absolute Zero actually equal to zero? That would be the Kelvin scale. It is defined more precisely as "the theoretical absence of all thermal energy". That means that on the molecular level, all atomic movement slows. As the temperature drops closer to absolute zero, atoms and even light, or the particles that make up light (the photon) behave different than at higher temperatures.

You'd think that the outer reaches of space might grow this cold, but in reality, the closest we humans have cataloged to absolute zero thus far is 1 degree K, recorded in the Boomerang Nebula:

In February 2003, the Boomerang Nebula, was found to be −272.15 °C; 1 K, the coldest place known outside a laboratory. The nebula is 5,000 light-years from Earth and is in the constellation Centaurus.^[7]

http://en.wikipedia.org/wiki/Absolute_zero

And actually, scientists have been able to push temperatures down far closer to absolute zero (but can never feasibly reach absolute zero) in the lab than has ever been observed in space. At these temperatures even light behaves differently, check it out:

The speed of light, as we've all heard, is a constant: 186,171 miles per second in a vacuum. But it is different in the real world, outside a vacuum; for instance, light not only bends but also slows ever so slightly when it passes through glass or water. Still, that's nothing compared with what happens when Hau shines a laser beam of light into a BEC: it's like hurling a baseball into a pillow. "First, we got the speed down to that of a bicycle," Hau says. "Now it's at a crawl, and we can actually stop it—keep light bottled up entirely inside the BEC, look at it, play with it and then release it when we're ready."

http://www.smithsonianmag.com/science-nature/12359501.html

What an amazing concept...

So what does all this really have to do with space? Well, I recently read Michio Kaku's book "Parallel Worlds", and am currently chewing through Brian Green's "The Elegant Universe". In Parallel Worlds, he speaks a little about what our universe looks like, and the properties it exhibits. Scientists widely believe that the universe is still expanding, but many hypothesized that the expansion was slowing. Recent studies have shown that the data suggests otherwise- the expansion of the universe is actually speeding up.

From the moment of the big bang, the universe, like the outside of a balloon, seems to be expanding. Just as if you were inflating the balloon. He talked a little about what would happen if the expansion kept going, pushing our galaxy, and our solar system further away from the known cosmos. He called it the Big Freeze I believe:

The idea of heat death stems from the second law of thermodynamics, which states that entropy tends to increase in an isolated system. If the universe lasts for a sufficient time, it will asymptotically approach a state where all energy is evenly distributed. In other words, in nature there is a tendency to the dissipation (energy loss) of mechanical energy (motion); hence, by extrapolation, there exists the view that the mechanical movement of the universe will run down in time due to the second law.

http://en.wikipedia.org/wiki/Big_Freeze

So anyways, theres no real need to fret, because as Sir Martin Rees so elequently puts it in his TED talk: "...by that time... human beings will look nothing like they do now..."

Who knew???