Friday, March 22, 2013

How Old Is It?

Space ... it's big. Really big. And it's getting bigger all the time.

Case in point: recently, the American Geophysical Union reported that the Voyager 1 spacecraft had left the Solar System, based upon a press release from NASA's Jet Propulsion Laboratory. Except, that's not quite what the JPL press release said. What JPL said was that Voyager had entered a new region of space, but hasn't quite left the Sun's influence yet. They're still waiting for the final sign, the direction of the magnetic field lines, to tell them that Voyager has crossed over into genuine interstellar space.

It won't be the first time we thought a spacecraft has left the Solar System. Back in 1983, Pioneer 10 crossed the orbit of Neptune, at that time the most distant planet from the Sun. Back then, the common thought was that that was the border. But the more we learn, the farther back the border is pushed.

(Incidentally, Neptune is once again the most distant planet from the Sun, now that Pluto has been demoted to a dwarf planet. But that's neither here nor there ... except that asking whether or not Pluto should be a planet is still a good question for starting a bench-clearing brawl at an astronomical conference.)

Likewise, the Universe itself gets bigger and older every time we look at it.

NASA and the European Space Agency have released the latest results from the Planck Space Telescope, launched in May 2009. Its mission was to expand on the work already done by the earlier COBE and WMAP probes. Basically, what they're trying to do is to capture the Universe's very first light, or what's left of it. As the current theory holds, 380,000 years after the Big Bang, the Universe cooled down enough to become transparent. That's as far back as we can see with any of our telescopes. COBE made the very first map of the microwave background radiation. It broadly confirmed the theory, but turned up some interesting results. To wit, the background radiation is lumpy, non-uniform. The patterns, if there were any, might yield some interesting clues as to the nature of the early Universe. So the WMAP mission was launched as a follow-up, with more sensitive instruments. WMAP was stunningly successful, and its map of the background radiation provided proof for the Lambda-CDM model of the early Universe. We still don't know what that "cold, dark matter" is, but the data provided by WMAP matches very closely with what's predicted by the theory. The Planck spacecraft was launched in 2009 to provide a more detailed data set, which was expected to refine our knowledge still further.

So far, Planck is delivering the goods.

The new map of the microwave background radiation is the most detailed yet, able to display structure and features no one imagined could be seen. For one, the data refines our estimate for the age of the Universe. The new estimate is about 100 million years older than we thought it was, or about 13.8 billion years old. Also, the Universe is not expanding quite as fast as we thought it was. There's less dark energy and more dark matter than we'd previously measured. (Not that we know what the Hell either one of those are, mind you.) But that's not even the most baffling bit.

This is.

Against all expectations, the Universe looks fundamentally different in one direction than it does in another. There's an enormous cold spot. If it's a genuine structure, and not an artifact of measurement, it's the biggest thing ever seen by humans. Some irregularities were visible on the WMAP data, causing Roger Penrose to hypothesize that those irregularities could be signs of a previous Universe, "echoes" of the last Big Crunch.

They said Penrose was mad. Maybe they were wrong?

We don't know yet. It's going to take a long time to digest just what all this means. No current theory accounts for the Cold Spot. Which means someone is going to have to cook up a new one that will. That won't happen tomorrow, or next week, or maybe even next year. But it will, and it'll be fascinating to find out what the implications are.

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