Monday, January 04, 2010

A Change in Perspective

Emerging from the vacation cave is never easy, and today is no exception. Remembering what it's like to schedule my day around anything other than naps and cookies seems strange, even though it's only been two weeks. I'm motivated, however, by how hard every astronomer in the world appears to have been working over the past month.

I'm cruising news sites and blogs and am overwhelmed by all the awesome astronomy news. There's been stars eaten alive, celebrating the holidays in space, pregnant gas clouds, and dancing black holes, to name a few. All the news got me thinking (a few days late) about the past, the present, and the future. New Year's is a time for personal reflection, and for many that may include reflecting on our place in the cosmos.

In 2009, scientists studying images from the Hubble Space Telescope determined that some of the galaxies they saw were the most distant galaxy ever detected. Now, researchers looking at data from the upgraded Hubble believe they have found even more distant galaxies, about 13.2 billion light years from Earth, meaning they formed when the Universe was only a few hundred thousand years old (it's total age is estimated to be somewhere around 14 billion).


Scientists can tell how far away a galaxy is by its redshift, or the degree to which the light is distorted by the motion of the star away from us. Galaxies further away are moving away from us more rapidly than those close by. The galaxies found earlier in 2009 had a redshift of 7 or 8, while the newly found galaxies have redshifts of about 10.

Because the galaxies are so far away, the light that we see is actually from that galaxy's early life. The new light that it emitted last week, or even a few billion years ago, hasn't finished it's journey from the galaxy to our telescopes. The galaxy may have changed drastically from what we see of it. We are looking at the galaxy as it existed in the past.

For astronomers, staring at this image might be like looking at a photograph of someone who lived long before we were born. We may wonder what similarities we have with the person in the picture? What differences? What fate did this galaxy meet? Is it still out there? Can it fill in a piece of our universe's history? Can it tell us about where we come from and where we are headed?

Human history can only be kept if people take the time to do so, but the universe provides us with a very natural historical timeline. If we are seeing the most distant galaxies the way they were 13 or so billion years ago, then we can also see what galaxies in our universe looked like at 11 billion years, 5 billion years, 1 billion and so on. The challenge for us is learning to read this history, and better telescopes are a big part of that.

Knowing your history isn't just for the benefit of having good stories to tell, or finding out whether or not you will lose your hair when you get older. Unless you know where you've been, it's hard to figure out where you are. Our pursuit of cosmic history will tell us where we are in the cosmic timeline, and our place on it may soon change. New research is suggesting that we need to reevaluate the age of our own solar system. The age of the solar system has historically been placed at about 4.5 billion years. That number is too large to try and figure out what happened during, say, the first ten million years when most of the cores of our current planets formed. For that you would need a number like 4.56 or better (where a change of ten million years would mean a change to 4.57).


Besides the lack of precision, the value may be very different than we previously knew because it is based on some out-dated assumptions.

To figure out the age of a very old rock (like the planets or meteorites from the solar system's early days) we use radioactive isotopes. If we know how long it takes for a radioactive element to decay into a secondary element, then the amounts of the primary and secondary elements should tell us how old that thing is. For the age of the universe, scientists compared the decay of uranium-235 and uranium-238.

But this comparison is based on the assumption that the ratio of these isotopes is constant. And it has been known for some time now that this isn't true. So now scientists are reevaluating previous estimates of how old our solar system is, with much higher precision than before. New studies are showing that levels of uranium-235 are higher than previously believed. This doesn't change the fundamental way in which we evaluate the age of the universe, but it could give slightly different values to previous measurements and new ones. Most of all, it will hopefully increase the precision.

Correcting our mistakes is part of growing. Learning from the past, improving on our present, and acknowledging that what we hold dear today may prove to be not-quite-right tomorrow, is part of our intellectual evolution. Civilization cannot progress without scientific progress, which not only builds on the ideas of yesterday, but is open to changing them.

That's a large view of the future; the large steps we will take over decades. There is still the decision of what to do tomorrow. You know that old saying, about how a journey of a thousand miles starts with a single step? Like building a timeline of the Universe starts with a trip to the coffee maker (Ha! Am I right?! Is this thing on?).

Well, NASA announced that it has narrowed down its candidates for the next space mission down to three: Venus, an Asteroid, or the Moon. Which will be our next step on this journey?


1 comment:

  1. Just FYI: These galaxies (if they are as distant as posited--not a sure thing by any means)would postdate the big bang by hundreds of millions of years, not by 'hundreds of thousands'.

    And a pair of factoids that may really cause some headpopping is that these galaxies (again if as distant as supposed) would actually be _40_ some billion light years from planet earth. (see "If the Universe is only 14 billion years old, how can we see objects that are now 47 billion light years away?" at http://www.astro.ucla.edu/~wright/cosmology_faq.html#DN for a good explanation as to how *that* is possible in a universe only 14 billion years old...) However (2nd factoid)...when these galaxies actually emitted the light that we have used to detect them--they were only around *5* billion LY distant!

    Fun, eh?

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