general relativity
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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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Cosmology: How Do We Know?
Have you ever wondered how the heck astronomers think we know anything about cosmology? It’s a truly mind-blowing field of study, full of whacky concepts like the shape of empty space, the expansion of the universe, and dark energy. More…
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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 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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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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Is Dark Matter Real?
Here we are, people — it’s finally time to talk about dark matter! I’ve teased this subject in my last few posts. We’ve discussed how the idea originated — with observations of the rotation of galaxies. We’ve touched on the…
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Binary Neutron Stars
Way back when we spent a number of posts surveying the stars, we covered binary systems. These are star systems that contain multiple stars. Imagine if our sun had a companion, and two stars rose and set in our sky…
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Einstein: Space-Time Curvature
When you hear about “space-time,” it’s just a way to say that space is related to time. And the curvature of space-time, as Albert Einstein predicted, is the way space and time alike literally bend around a mass such as the…
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Einstein: General Relativity
Albert Einstein may have been the genius among physicists, but like all others before his time, he stood on the shoulders of giants. Einstein did not propose that the sun was the center of the solar system; that idea was…
