advanced: cosmology
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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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Dark Matter: What We Don’t Know
Okay, I know…weird way to start a post, right? Isn’t this blog supposed to teach science? How can we teach something we don’t know? This is actually one of the most important concepts in the realm of astrophysics, and even…
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Dark Matter: How Do We Know?
In theoretical physics, there are countless theories as to what dark matter is. But how do we know it’s not a wild goose chase? Technically speaking, we don’t. But fortunately for us, this question comes back to one of the…
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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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Geometry is Destiny…or is it?
Cosmologists used to think that gravity alone determined the shape of the universe, and that shape, in turn, determined its future. But that raised a lot of problems. Gravity works by curving space-time, so it can also force the fabric…
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The Discovery of Dark Energy
In 1998, astronomers made an extraordinary discovery. Contrary to expectation, the expansion of the universe is accelerating. Astronomers wondered at first if their measurements were wrong; further measurements confirmed the results. And then confirmation of the expansion came in the…
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Should Expanding Space be Slowing Down?
Einstein’s theory of general relativity holds that matter curves the fabric of space-time. That’s how gravity works. In turn, that gravity shapes the fabric of the universe. Depending on how much mass is in the universe, gravitation can curve the…
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Why do Galaxies Exist?
When we look out into the sky, we see a universe filled with galaxies. Galaxies are the second-largest “structure” we’ve covered in depth on this blog. The largest so far have been galaxy clusters, which are just what the name…
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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…
