I see, hear, and read about black holes and their consumption power often. They grow as they consume. Eventually, as they keep growing and consuming, wouldn’t they combine and continue the process until they become so large as to devour everything in existence?
In: Physics
Nah, the universe won’t eat itself. It’s big, but not infinite. Plus, expansion is happening too.
We’re not sure because we don’t know everything.
We know that space is expanding while gravity is pulling everything together. If the universe keeps acting like it does today, where the expansion outpaces gravity pulling things together, everything will get pulled apart (or, at least large objects like galaxy groups).
If the expansion of the universe slows, though, everything will get pulled together into a single point.
No, for a number of reasons.
First, black holes are much, much, much, much smaller than the size of the universe. The universe is continually expanding in every direction, and black holes, despite being massively larger than anything we can conceptualize, are still orders of magnitude smaller than the size of the universe.
Second, black holes don’t grow forever. Steven Hawking’s research showed that black holes will actually slowly evaporate if they don’t have matter to consume. Black holes also don’t grow *that* quickly. Creating a black hole requires a relatively specific set of circumstances, so it’s not like they’re going to pop into exist everywhere.
We’re not really sure what might happen over trillions of years, but afaik the current understanding is that black holes can’t grow big enough to swallow the universe.
I’m sure there are plenty of astronomers with more knowledge than me that can add more detail and/or correct me in the comments haha
It’s been theorized that Black Holes eventually evaporate because of something called “Hawking Radiation”. It would take a very long time to happen though. Alongside that and continuous expansion, it would be very unlikely for the universe to eat itself.
The expansion of the universe is currently accelerating faster than gravity can slow it down, so at very large scales, galaxies are being pushed apart, not pulled together. In that sense the universe is going to continue to expand indefinitely, not get eaten.
However, in the very distant future, there is likely to come an era when black holes dominate the universe because, as you’ve guessed here, they’ve pulled in all the available matter around themselves. The last generations of stars will be dying out, there will be fewer and fewer gas clouds left to collapse into new stars, and so the debris of dead stars — like black holes — will dominate the universe.
Weirdly enough, collapsing into black holes actually has the exact opposite effect.
Earth spins around its own centre once every 24 hours (give or take). As a result, anything that’s orbiting Earth far enough away to take more than 24 hours to go all the way around – such as the Moon for example – is actually getting very slowly *pushed away* (or pulled away rather) by the Earth’s gravity.
Very, *very*, slowly. The Moon was probably twice as close a few billion years ago. With a B.
This pulling-away gravity effect is known as a tidal force, named after the tides we see on Earth when the oceans pull-push the Moon (and to a lesser extent, the Sun).
If Earth suddenly collapsed into a black hole, its mass wouldn’t change. Its angular momentum would be the same. But its radius would be much smaller, so it’d spin much faster, so instead of sucking in and eating the Moon, Earth would actually push/pull it away *faster*.
We think. We’re pretty sure that’s how black holes work, but for obvious reasons we’ve never observed it directly. We do know it’s how they work when two black holes orbit each other.
No. Black holes are no different than a star, of you turned the sun into a black hole then the movement of the planets would not change. Black holes don’t just suck shit it, they have not all gravity according to their mass, shot just gets a little weird after you cross a certain threshold very very close to the center. Outside of that it’s business as usual. All galaxies are built around enormous black holes like how solar systems orbit stars, it works the same way.
The universe is constantly expanding at almost the speed of light. Eventually everything will be spaced out so much no galaxies will be able to see each other, in a billions year it’ll look our galaxy is alone in the universe because no other light will reach us. Assuming our galaxy still exists
Black holes are somewhat self-limiting. As matter falls in, it contributes to the mass, yes. However, angular momentum is always conserved – meaning, stuff is orbiting around the black hole, and the stuff itself is spinning. That rotational energy becomes part of the black hole system, making it spin faster. As it does, it twists and pulls space, too, which drags everything around the black hole faster.
Orbit distance is a function of the speed. If something orbits faster, its orbit will be higher. As the black hole spins faster and faster, the stuff around it gets flung *outward*. Eventually, the orbits will be too fast and too high, and stuff will no longer fall into the black hole.
Moreover, when stuff falls into the black hole, it smashes and grinds against all the stuff swirling around. This is what makes the accretion disc, the bright glowing rings around the black hole. The accretion disks of a supermassive black hole are among the brightest objects in the universe, often outshining every other star in the galaxy around the black hole *combined*. Light has momentum and all that light blasting outwards creates a pressure that pushes against the matter being drawn in. Again, at some point the pressure from the light will reach equilibrium with the gravity pulling inwards (as long as it’s beyond the event horizon), and no more stuff can fall in.
Between these two things, and the evaporation of black holes due to Hawking radiation, black holes all stop “feeding” and eventually completely disappear. Although, the “disappearing” part takes a very very long time – like, 10^67 years for a black hole only the size of the Sun. A supermassive black hole will take much much longer than that, something along the lines of 10^100 years.
The three possible ends of the universe are:
Big Crunch – In this scenario, the expansion of the universe slows down before it can overcome gravity. The collective gravity of all the matter pulls inwards until everything slows down and then reverses, falling inwards towards itself. The universe collapses into another Big Bang.
Big Rip – In this scenario, expansion continues to accelerate until it outpaces not only the gravity of superclusters, and then clusters, and then local groups…and so on, until space is expanding so fast that even solar systems are flung apart. Then, space will expand fast enough that the gravity of stars and planets holding themselves together fails, and they fall apart. Then, expansion goes so fast that it overcomes the forces holding molecules and atoms together, and the entire universe falls apart at the most fundamental level, faster than light.
Heat Death – In this scenario, expansion doesn’t keep accelerating, but it’s still too fast for gravity to pull inwards to the Big Crunch. Over an incomprehensibly long timeline, every star runs out of fuel until only black holes are left, and then those evaporate, too, until literally nothing is left except lone protons and photons too spread out to ever meet.
Conservatation of mass (as it relates to chemical reactions): matter can not be created nor destroyed, only change form. Thus the big bang theory.
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