Cosmology
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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…
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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…
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The Shape of Space
I’ll admit it: when I hear something like “the shape of space,” my first thought is, whaaaaa? It’s hard to talk about the science behind space itself because we first have to wrap our minds around what that even means.…
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Cosmological Redshift Demystified
If you’ve been following my recent posts, cosmological redshift will likely be a familiar idea. I introduced it in my post on the Hubble Law. We revisited it again in our discussion of the size and brightness of galaxies. When…
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What is the Cosmological Principle?
What if I were to ask you: Are there any unique places in the universe? That is, does any one location in the universe have a special vantage point? Does the universe look different from different locations? You might say…
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From the First Nuclei to First Light
When we talk about the first 30 minutes of time, we describe the universe expanding and cooling. As the universe cooled, the nuclear reactions that produced the first atomic nuclei slowed and stopped. But it was only relatively cool. The…
