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Topic: Are we going to be safe on the moon if Earth turns into a black hole? (Read 1920 times)
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Zanthius
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The moon is currently within Earth's gravity field, but I don't think it will be if Earth turns into a black hole. To increase the depth of a gravity field without increasing the mass I think you need to reduce the diameter or circumference of the gravity well. So I think we would be safe on the moon.
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« Last Edit: January 20, 2018, 01:13:36 pm by Zanthius »
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Krulle
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*Hurghi*! Krulle is *spitting* again!
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Yes, and no.
The Earth's attraction on the moon will change marginally. The mass of Earth remains the same, but instead of the mass being distributed of a rather large volume, it will be a point in space. This may change the equation marginally. I presume, Earth and Moon will drift apart slightly faster than they already do, but it'll still take centuries to become noticeable (instead of millions of years).
So we can plan our next step i to the stars from the stepping stone, if need would arise.
But we don't know if the black hole will have some kind of devastating radiation at it's poles, or any magnetic field, and how all that might affect the moon or artificial installations there....
Not gonna put my further thoughts into text now (like the effect of the loss of the tides on Earths attraction on the moon (marginal effect, but apparently measurable),...)
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« Last Edit: January 20, 2018, 01:22:43 pm by Krulle »
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Zanthius
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Another question. If tiny black holes with masses of around a few hundred million metric tons are drifting around in space, would they be easy for us to detect?
If not. Could such a tiny black hole crash into earth at any moment and turn earth into a black hole?
Also. Could such tiny black holes be the missing dark matter?
You can calculate the estimated lifespan for different black holes here:
http://xaonon.dyndns.org/hawking/
As you can see, black holes start to get quite significant lifespans already with a few hundred million metric tons.
A black hole of 100 million metric tons should have a lifespan of about 2.67 billion years and have about the size of a proton.
look what I found:
https://m.phys.org/news/2017-08-theory-heavy-elements-primordial-black.html
What I am curious about is how far away will a black hole the size of a proton be able to attract matter from.
Some people seem to think that a black hole the size of a proton will go straight through the earth without turning the earth into a black hole.
"Asteroid-mass black holes, if they were all of the dark matter, might pass through the Earth once a millennium or so, but would be very, very hard to detect," Brandt told Business Insider. "If you had somebody right there, they might be able to observe one."
http://www.iflscience.com/space/miniature-black-holes-may-be-hitting-earth-once-every-1000-years/
It would be interesting to know the smallest sized black hole that would turn earth into a black hole. And if there are lots of those black holes.
The mass of Pluto compressed to a black hole would be 0.015 mm. That should be more than big enough to turn earth into a black hole.
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« Last Edit: January 21, 2018, 12:23:28 am by Zanthius »
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Krulle
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It depends on distance, and relativ speed between the black hole and Earth.
If the black hole just flies extremely fast through Earth, it won't collect much mass before it leaves Earth again.
There are plenty of scenarios where it can still be desastrous, and just as many where nothing measurable happens.
Until we observe it happening, or be able to prove something which has hapened must've been caused by a micro black hole, we won't know.
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Zanthius
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I think it is highly unlikely that a black hole with the size of a proton will be able to consume Earth, because it is very unlikely that it will crash into large amounts of Earth matter. Even if it crashes into a nucleus, it will have almost no effect on the trajectory, since the nucleus has so little mass in comperison. It would need to crash into billions of nucleuses in order for it to slow down enough to be able to consume Earth, and that is highly unlikely when it is so small. It might however be able to consume a neutron star, since matter is much more dense there.
I made this graph to show how large I think a tiny black hole needs to be in order to consume Earth:
Black holes that are bigger than atoms should crash into lots of Earth matter, and they should therefore be able to consume Earth.
I think the black holes that are between 10^9 metric tons and 10^14 metric tons, could constiute most of the dark matter, since they are so weakly interacting with normal matter.
Also, black holes that are smaller than 10^9 metric tons should already have evaporated due to hawking radiation. Could hawking radiation from these black holes be the dark energy we are looking for?
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« Last Edit: January 21, 2018, 08:07:02 pm by Zanthius »
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Death 999
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We did. You did. Yes we can. No.
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The surface acceleration of gravity of such a hole is around 10^32 meters per second per second, so I think most of the lost energy would be by pulling on but not absorbing the matter around it. That could dampen its motion enough that it would slow down and become captured, at which point it would have plenty of time to suck the thing up.
I thought these were not viable as dark matter candidates, but now that I've looked into it a bit more it seems a bit more viable.
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Zanthius
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Here is a graph showing the black holes I think have caused the expansion of the universe:
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Krulle
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*Hurghi*! Krulle is *spitting* again!
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The black holes still have mass, and thus will attract and consume other matter.
But if the relative speed is high, the other matter has "escape velocity" from the black holes and herefore the interaction will be limited to attraction/gravity forces.
Damage will still happen. And the friction this mass attraction causes will also reduce the relative speed.
There are too many factors to consider to be able to forecast a general way such a "collission" would have.
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Death 999
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We did. You did. Yes we can. No.
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I ran some basic numbers. Falling into our solar system and passing through the sun would probably slow a 100MT hole down by less than 1%, unless I'm missing the dominant braking effect. Not so likely to capture.
But if there are a lot of them - enough to account for the bulk of dark matter - then the law of large numbers would suggest that one would eventually become gravitationally bound, and then repeat the process enough times that it would eat the sun.
Also, I haven't run the numbers on the required number density for them, but I suspect it would be high,
I'd also want to figure out how much such a hole would disrupt materials it passes through. By my calculations, the acceleration it would apply to every atom within 1 nm of its path is around 10^18 m/s/s, for around 10^-15 s. Within a radius of 10 nm, it would be 10^16 m/s/s for 10^-14 s. This is not obviously a force that a material can simply shrug off without becoming defective all along the line.
We could look at ancient materials to see if there are such defects.
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