center of mass
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What is a Black Hole, Really?
If you’re a sci-fi fan, you’ve probably seen these in movies. And I’m guessing you’ve heard a lot about them in pop culture. The problem is, pop culture and movies don’t do a very good job of describing black holes.…
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What Happens in an Expanding Star’s Core?
Depending on their mass, stars can remain stable for millions and even billions of years. The most massive stars live for “only” about 10 million years, but models predict that the least massive live for much longer — longer than…
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Binary Stars
We know how big stars are; they range from the size of the Earth to over a thousand times the size of the sun (which is in itself over one hundred times the size of the Earth). We know they’re…
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How Orbits Work
Since Aristotle’s time over 2000 years ago, we have accepted that the moon orbits the Earth. We didn’t always know why, and we didn’t always accept this for the right reasons. We used to assume that it happened just because…
