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Cosmic Variance

Digging Up the Early Universe

2 Oct 2012, 15:31 UTC
Digging Up the Early Universe
(200 words excerpt, click title or image to see full post)

I wrote another column for Discover (the actual magazine), which is now available online. It’s about how far back in cosmological time we can push our knowledge on the basis of actual data, not mere theory.
Of course we literally look back in time every time we peer into a telescope, since it takes time for light to travel to us from distant objects. But there’s an earliest moment we can possibly see using light — the moment of recombination, about 380,000 years after the Big Bang, when electrons hooked up with protons and other nuclei to form atoms. Earlier than that, the electrons were floating around freely, bumping into photons, and generally making the universe opaque.
So we have to be a bit more clever. And we have been: using the fact that the early universe was a nuclear fusion reactor, and observing the surviving abundances of light elements to pin down what conditions were like at that time. This technique gets us within seconds of the Big Bang. But if things break just right — the dark matter turns out to be a weakly-interacting particle, whose properties we can study here on Earth — we might be able ...

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