If you have a question you’d like an expert to answer, send it to curiouskids@theconversation.edu.au.
Can Earth be affected by a black hole in the future? – Rakovi, age 12, Dimapur, India.
That is a great question.
As you know, black holes are called that because the gravity in their centre is so strong, it sucks all nearby light in. None can escape. That’s how strong a black’s hole’s gravitational pull is.
Black holes create the strongest gravitational pull in the universe (that we know of). So you really don’t want to get very close to one.
If you get too close, the pull of gravity from the black hole is so strong that you would never be able to escape, even if you were travelling at the speed of light.
This point of no return is called “the event horizon”.
Another reason you don’t want to get too close to a black hole is because of something we call “spaghettification”.
Imagine an object in space, like a star. As the star gets closer to a black hole, one side of it is pulled harder than the other. That’s because one side of the star will be closer to the black hole than the other.
The pull from gravity will be stronger on the side closest to the black hole, and weaker on the side that’s further away.
This difference in the pull of gravity (which is called a “tidal force”) would cause the star to get pulled apart. It’s kind of like pulling a lump of pasta dough into spaghetti.
Sometimes astronomers can observe this happening in other galaxies. The technical name is a “tidal disruption event” but it just means that a star got too close to a black hole and got pulled apart.
Here’s an artist’s impression of what spaghettification might look like:
The closest black hole is too far away to hurt us
Thankfully, though, we don’t need to worry. There are no black holes close enough to Earth to affect us. The closest black hole to Earth that we know of is named V616 Monocerotis. It is also known as A0620-00.
This black hole is 6.6 times more massive than our Sun. (That means it has a lot of mass, which means it has a really strong gravitational pull – much stronger than even our Sun’s gravitational pull.)
If Earth gets within about 800,000 kilometres (3.7 light seconds) of this black hole it will get pulled apart. But that’s unlikely to happen and certainly not in your lifetime.
V616 Monocerotis is about 3,300 light years away. That’s very, very far away.
Black holes do not go around in space eating stars, moons and planets. Earth will not fall into a black hole because no black hole is close enough to the solar system for Earth to do that. The sun will never turn into a black hole. The sun is not a big enough star to make a black hole.
Despite their abundance, there is no reason to panic: black holes will not devour Earth nor the Universe. It is incredibly unlikely Earth would fall into a black hole because, at a distance, their gravitational pull is no more compelling than a star of the same mass.
Eventually, in theory, black holes will evaporate through Hawking radiation. But it would take much longer than the entire age of the universe for most black holes we know about to significantly evaporate. Black holes, even the ones around a few times the mass of the Sun, will be around for a really, really long time!
"[But] even a large stellar-mass black hole, say 30 solar masses, would have to be closer than Neptune (roughly 30 times the Earth-sun distance) to begin to have gravitational impacts on Earth, and about the distance of Jupiter (roughly five times the Earth-sun distance) to pull on Earth with roughly equal ...
Our Sun is too small a star to end its life as a black hole. But what would happen if the Sun were suddenly replaced with a black hole of the same mass? Contrary to popular belief, the Solar System would not be sucked in: a solar-mass black hole would exert no more gravitational pull than our Sun.
The possibility that a black hole could actually impact Earth may seem straight out of science fiction, but the reality is that microscopic primordial black holes could actually hit Earth. If one did, it wouldn't just impact like an asteroid, it'd pass straight through the entire Earth and exit the other side.
The black hole would need to be roughly 100 million kg, and it will take many hours or days to fully destroy Earth. Very low-mass black holes are expected to undergo rapid decay through.
“If you were to stand just outside the event horizon of Sagittarius A*, and you stood there for one minute, 700 years would pass because time passes so much slower in the gravitational field there than it does on Earth.” Some have suggested that black holes could be used for time travel.
When matter falls into or comes closer than the event horizon of a black hole, it becomes isolated from the rest of space-time. It can never leave that region. For all practical purposes the matter has disappeared from the universe.
A clock near a black hole will tick very slowly compared to one on Earth. One year near a black hole could mean 80 years on Earth, as you may have seen illustrated in the movie Interstellar. In this way, black holes can be used to travel to the future.
Near a black hole, the slowing of time is extreme. From the viewpoint of an observer outside the black hole, time stops. For example, an object falling into the hole would appear frozen in time at the edge of the hole. Inside a black hole is where the real mystery lies.
The volume of neutrinos that would be coming from the cluster of stars near a black hole would be enough to radioactively heat up whatever they slam into. The planet would absorb neutrinos, warming up its core, eventually making the planet unbearably hot. It would be like living in a nuclear reactor.
White holes are the opposite of black holes, in that they spit out light and matter, rather than trapping it. So far, white holes are purely hypothetical objects, but astronomers are contemplating how they could form in reality.
The most alarming consequence of a collision between Jupiter and a black hole would be the relentless onslaught of asteroids directed toward Earth. As the black hole traverses our solar system, it would strip away the gases enveloping the gas giants, forming an accretion disk of superheated gas and dust around itself.
D Astrophysics, University of Leicester, said a 1mm black hole would still have a mass of 10 percent that of Earth. If it was to hover on Earth's surface, its gravitational pull would cover a third of the planet, tearing it up at 12 kilometres per second.
If the earth stood still, the oceans would gradually migrate toward the poles and cause land in the equatorial region to emerge. This would eventually result in a huge equatorial megacontinent and two large polar oceans.
That being said, we shouldn't be too worried about Gaia BH1, since 1,500 light years is still very far away, and there's not much chance of us falling in anytime soon.
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