critical density
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Cosmology Demystified
That has got to be the single strangest post title I’ve ever written. Of all the whacky branches of science out there, cosmology almost takes the cake — second only, I think, to the downright trippy world of quantum mechanics.…
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The Proof in the Afterglow
In 1915, Einstein published his theory of general relativity. This theory predicts that, since gravity works by bending space-time, it also determines the shape of space — and the shape of the universe as a whole. In 1929, Edwin Hubble…
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The Big Bang Theory, Revised
Imagine a time before stars and galaxies existed, before free-floating subatomic particles combined to form the first atoms, before the synthesis of the first atomic nuclei… Wait a second — this sounds familiar! Way back in May, we rewound the…
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The Problem of Matter
At first glance, this is an ordinary image of a galaxy cluster: specifically, Abell 1689. If we look closer, though, we see that there’s something weird going on with the more distant, background galaxies in the image. Many of those…
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Could the Universe be Curved?
I know…that seems like a strange question to ask, doesn’t it? Out of context, it makes no sense at all. What are we even talking about? The curvature of what? Cosmology is full of questions like this — questions that…
