escape velocity
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How Massive are Galaxies?
If you needed to measure the mass of, say, a brick — or some other Earthly object — you could just set it on a scale. (Yes, scales measure mass, not weight.) With galaxies, it’s not so easy! I don’t…
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How to Find a Black Hole
Okay, good question. How the heck do you find an object that emits no radiation? Astronomers find — and study — just about everything in the universe using the radiation it emits or reflects. So…what happens when the object we’re…
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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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Moving with the Tides
Have you ever been to the beach? If you’re from California like me, then I’m betting you have. If you’re from a place that’s not near an ocean and you’ve never been near the water all your life, then I’ll…
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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…
