Marc
  • Member for 8 years, 1 month
  • Last seen more than 2 years ago
  • San Diego, CA
Do solar systems have to evolve in a galaxy?
Accepted answer
6 votes

Probably not. You'd need a could of gas dense enough to contract under its own gravity. In the space between galaxies, matter is spread too thin for a solar-system sized cloud to exist. A much larger ...

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Why is liquid water considered a requirement for life?
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6 votes

"Life" seems to be an emergent phenomenon, a complex result of a very large number of simple parts or interactions. The whole is more than the sum of it's parts, unpredicted by the properties of the ...

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How did Kepler determine the orbital period of Mars?
5 votes

Kepler did know the orbital period of the Earth, Mars, Venus, Mercury, Jupiter, and Saturn. He had access to observations going back centuries, including Brahe's most excellent data. What couldn't ...

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Is it possible to be 'still' in space?
5 votes

There is no 'still' that is not relative to some other object. So yes, you can be still with respect to one object, but you'll be moving with respect to every other object. As for using it as a form ...

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How is the magnitude of a star measured?
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5 votes

A device called a photomultiplier is attached to a telescope. The telescope is pointed at the target star and an aperture is closed down to avoid as much spurious light as possible, and a reading is ...

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Why does time get slow near a black hole?
3 votes

Time does not pass slower near a black hole. Stay-Home-Sally far from a black hole observing Astro-Bob descending into a black hole would see Bob's time passing slower as Bob neared the event horizon,...

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If NASA is going to capture an asteroid with a spacecraft, wouldn't a UFO be able to manuever a celestial body?
3 votes

You are assuming there are extraterrestrial space travelers those travelers have technologies we know nothing of those technologies we know nothing of allow "levitation" and "vectoring themselves" ...

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What is the formula to figure out how far away a star is?
3 votes

One method involves finding a cepheid variable in the vicinity of the star, or even in the galaxy you are investigating. These stars vary in brightness with a period closely related to their absolute ...

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Why don't we feel the speed of earth moving
2 votes

If you're big enough and fluid enough, like an atmosphere, you would feel acceleration do to the Earth's motion. Hadley cells are patterns of warm air rising in the tropics, flowing north, and sinking ...

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What happened before the big bang?
2 votes

"What happened before the Big Bang" is like asking what Alexander the Great's phone number was. It's a nonsensical question. Space and time began with the Big Bang. "When" and "where" began with the ...

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Why can you see the space station on some days but not on others?
2 votes

Best viewing will be shortly before sunrise or shortly after sunset so your sky is dark, but not so late that everything above you will be in the Earth's shadow. It will be brightest when it's near ...

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Which is really larger, Big Dipper or Small Dipper, in 3D
1 votes

It's hard to say without some research, but I don't think the answer really matters much. Both constellations are chance alignments that have little or nothing to do with how close the stars really ...

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Would it be possible to calculate the expected frequency of impact craters of all sizes on Earth
1 votes

Yes. By looking at a nearby object that hasn't been subject to erosion and has been subject to the same position around the sun, you could estimate the distribution of impacts on the Earth in time and ...

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Why are planets spherical?
1 votes

If the planet was made of gas or liquid, and was not spinning it would be a perfect sphere, because with each atom settling as close to the center as possible, that's the shape you get. We can see ...

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Radioactive decay is the main source of the earth's interior heat: fact or theory?
0 votes

There are really only six ways you could heat the interior of a planet. Gravitational collapse and compression, fission, fusion, crystallization, a very large impactor, and tidal flexing. Fusion is ...

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Why do objects burn when they enter earth's atmosphere?
0 votes

An object hitting the Earth at high speed has a lot of kinetic energy, \begin{align} \frac{1}{2}mv^2 \end{align} where m is the object's mass and v is it's velocity. If the velocity goes from lots ...

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