Death From the Skies!: These Are the Ways the World Will End...
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To be specific, this should say “collisions between large galaxies.” Big galaxies eat small ones all the time; the Milky Way is cannibalizing two dwarf galaxies right now. Both have been torn apart by the galaxy’s gravity, and their stars are slowly becoming integrated with the original Milky Way population. This has happened many times in the past as well.
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One prediction of Einstein’s relativity is that merging black holes will actually cause a ripple in the fabric of space and time, like taking a bedsheet and frantically whipping it up and down. However, the gravitational waves resulting from two SMBHs merging are probably not strong enough to have any real effect on stars and other matter around them.
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On the other hand, you can argue that since the Universe is all there is, everything there is, then the explosion happened everywhere all at once, and so it was big. That’s just semantics, though.
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That means 0.0000000000000000000000000000000000000000001 second old.
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To paraphrase the great philosopher-scientist Nigel Tufnel from This Is Spinal Tap: “How much more north could it be? The answer is none. None more north.”
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Anything’s possible.
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Literally, the creation of new nuclei, new elements.
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A little math: Like gravity, the brightness of a star decreases with the square of the distance to the star—double the distance to a star and it will appear one-quarter as bright. But if stars are distributed evenly throughout the Universe, you’re basically adding up all the light from stars at a given distance from you, and they form the surface of a sphere. The area of the surface of a sphere depends on the square of its radius. So brightness drops with the distance squared, and the number of stars goes up with the distance squared—canceling each other out.
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I am using the word theory as a scientist means it: a set of ideas so well established by observations and physical models that it is essentially indistinguishable from fact. This is different from the colloquial use that means “guess.” To a scientist, you can bet your life on a theory. Remember, gravity is “just a theory” too.
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Light reflecting off water and metal can get polarized as well. Sunglasses that are polarized can block just the type of light waves that are aligned in that way, greatly reducing the glare of light reflected off cars and puddles.
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Gas does get recycled in galaxies: stars explode, other stars lose mass in a stellar wind, and so on. It’s possible in some galaxies that stellar birth may continue for as long as another trillion years, but those are the exceptions, not the rules. In a trillion years or so, star formation will effectively cease.
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In fact, it’s exactly like that: gas in a dwarf circulates in precisely this manner.
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In reality, the explanation of this is far more complicated and involves invoking Einstein’s theory of relativity. I’ll spare you that and just leave you with the treadmill analogy, which is close enough.
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Remember, as discussed earlier, that space can expand faster than the speed of light. The distant galaxies aren’t really moving faster than light; the space in between the galaxy and us is expanding such that it appears the galaxy is moving faster than light. Think of it as the track on the treadmill stretching as you’re running on it.
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I’m at a loss for a name for this galaxy . . . MilkLocalGroupeda? Androgroupyway?
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There are some theories stating that, depending on what’s driving the acceleration, the Universal expansion may overwhelm gravity. Eventually, all of space will stretch, including space in between bound gravitational objects. If that’s the case, then the horizon will continue to move in while space stretches. Eventually, everything will stretch—galaxies, stars, planets, even atoms. At some point, everything will get torn asunder as space itself shreds apart. For some reason, scientists call this idea the Big Rip. This turn of events seems pretty unlikely given what we know about the Universe, but it’s something to consider.
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There will still be planets; they will orbit white dwarfs and brown dwarfs, and probably many more will wander the Universe after being ejected from their home stars during planetary formation. However, planets don’t generate energy, so they aren’t of much interest to us here. They’ll be frozen solid.
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Binary brown dwarfs are common: two brown dwarfs in orbit around each other. Owing to some weird effects of Einstein’s relativity, the orbits of the objects will slowly decay with time. For a typical pair, the two objects will collide after about 1019 years, which is in the Degenerate Era. A merging of two brown dwarfs this way will almost certainly create a disk of material around them in the same way as an off-center collision would. This may be a “common” event during this era.
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Astronomers use the term collision to mean any encounter where two or more objects interact with each other through gravity, and not necessarily to mean direct physical contact like a car crash.
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Unlike smaller black holes, which will tear a star apart because of tidal forces, a supermassive black hole’s tides are far, far smaller, so stars will get eaten whole. There will be no accretion disk, and so no light emitted by the consumption of a star. Eating gas clouds, on the other hand, still will cause the black hole cosmic indigestion.
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We don’t have to wait that long to see one decay: if we collect enough together, say 1037 of them, then we should see one decay every year. This has been attempted, and still no protons have decayed while scientists watched. If the decay time is off by a little bit—say it’s 1038—then this makes the process more difficult to detect . . . but 1038 years is still small compared to the time we’re talking about in this chapter.
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Or whatever non-proton-based food they eat while watching movies.
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Because of the bizarre nature of degenerate matter, lower-mass objects actually increase in size when they lose mass, the opposite of what we expect. White dwarfs start out roughly the size of the Earth, but in 1039 years or more, they’ll actually expand to be as big as Jupiter.
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This released energy mostly gets converted into sound (footsteps) and motion (momentum as you travel down).
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Yes, I had to look up those two words.