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Well, my crazy question is whether it would be possible to make a "dyson sphere", but with the sonic black hole made with Bose-Einstein condensate (and whether it would be possible to create a black hole itself with that sonic black hole).

There is a fifth state of matter called "Bose-Einstein Condensate" (the 4th one is plasma), which is achieved by cooling a material close to absolute zero (in case you don't know, the term "absolute zero" refers to the Kelvin scale, which is more accurate than that the Celsius scale that we use, would be equivalent to -273.15 °C).

Basically, in this state, the matter is like a "cloud" (hence the name "condensate"). The interesting part is that scientists used this state of matter to prove Hawkin's paradox (yes, Stephen Hawkin, that guy in the wheelchair), where black holes waste energy with virtual particles and "die" after some ages in the universe (it is a paradox because nobody knows where the energy sucked to the black hole goes).

They did this by using Bose-Einstein Condensate to create a sound black hole (which acts like a normal black hole, but only with sound waves).

"The Black Hole Bomb and the Black Hole Civilizations": https://youtu.be/ulCdoCfw-bY

Well, the point is that there is a type of "Dyson sphere" for black holes, which is simply a "sphere" made of mirrors.

Certain types of black holes, the rotating ones, can accelerate anything that passes close to them. As if you are swimming in the same direction as the tide.

With this, if you turn on a lamp on one side, on the other you will receive a faster and more energetic light. Technically generating "infinite" energy (until the black hole "dies").

Well, my crazy question is whether it would be possible to do that same thing, but with the sound black hole made with Bose-Einstein condensate.

My second crazy question is whether it would be possible to create an artificial black hole using this bomb.

Basically, as shown in the video, if you do this with a black hole and do not open this sphere of glass to release the energy, the light will bounce and gain energy until the mirror can not take it anymore, releasing the energy equivalent to that of a supernova.

Assuming that the audible black hole would work the same way, you would create a super bomb without explosives. Because when the sound (which in itself is just vibrations in the air) reaches a certain volume, it stops being vibrations and becomes impact waves (like an explosion). The point is that if you reach a certain volume (1100 decibels), the shock waves compress the air enough to create micro-black holes.

Thus, with vibrations large and constant enough, it would be possible to create an artificial black hole using a sonorous black hole.

Again: assuming that this audible black hole behaves in the same way as a rotating black hole.

Well, if this is physically impossible, at least it is a cool sci-fi concept...

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    $\begingroup$ The maximum sound intensity in air at a pressure of 1 atmosphere is about 194 decibels. Because at 194 decibels the sound pressure is 1 atmosphere, which means that the peaks of the sound waves are at 2 atmospheres and the valleys are at 0 atmospheres... and you cannot go more vacuum than a vacuum. Above 194 decibels you get a shock front, not a wave. And shock fronts do not "vibrate". $\endgroup$
    – AlexP
    Mar 18, 2021 at 22:29
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    $\begingroup$ By definition, light is already moving at c, and therefore it can't be accelerated by spinning black holes. $\endgroup$ Mar 18, 2021 at 22:38
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    $\begingroup$ Also, the man's name was Stephen Hawking. $\endgroup$
    – jdunlop
    Mar 18, 2021 at 23:15
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    $\begingroup$ We recommend that you wait for 48 hours after asking a question before accepting an answer. We have an international community and not all time zones are awake at the time of asking the question, also awarding a tick early discourages other potentially helpful answers. You may withdraw the tick and then re-award it later. $\endgroup$ Mar 19, 2021 at 2:29
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    $\begingroup$ First thing first a sonic blackhole is a way to show the one way flow using soundwave and so probably the math can reveal some other interesting things, but the analogy breaks down since spacetime isn't soundwave so I think maybe you took it too literally ;D $\endgroup$
    – user6760
    Mar 19, 2021 at 4:59

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Well, my crazy question is whether it would be possible to do that same thing, but with the sound black hole made with Bose-Einstein condensate.

To a point.

A black hole is not a source of infinite energy; a rotating black hole (so-called Kerr black hole) can yield the energy associated to its momentum. When the momentum is being depleted (granted, you have lots of available energy), the ergosphere shrinks and eventually vanishes, the black hole reverting to the Schwarzschild type.

Your "sound black hole" might work the same way, exhibiting an event horizon that nothing can break free from while moving slower than sound.

But it wouldn't have an ergosphere, because the ergosphere is a space-time distortion, and the sound black hole would have no such distortion.

Even if it had - if we could model a Kerr black hole using sound - such a black hole would still be artificial, and the energy you could harvest from it would be just the energy you put inside in the first place (minus thermodynamic losses).

A sound black hole's energy doesn't come from the rotation of a massive star core, as a real black hole's does.

What you'd get would then be... a battery. Something you can recharge and deplete, up to capacity (this "battery" capacity would be connected with the maximum energy storable in whatever medium is vibrating inside the "sound black hole").

As for the Bose-Einstein condensate, you've got a problem - the condensate isn't stable except at really low temperatures, so a large condensate structure in space would require massive, complex refrigerators to overcome the microwave background radiation heating it to normal matter states. And a black hole made of condensate would be exactly identical to any other black hole of the same mass, charge and momentum.

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A black hole is a body that has enough mass to cause the escape velocity in its vicinity to be greater than the speed of light in a vacuum. I could nerd on about this for hours, and indeed there are many books and papers just about them; You can also spend a lot of time reading about them in our sister site physics.se, or find enough math and definitions to entertain yourself for hours on Wikipedia.

The important thing is that if you smash a lot of air (or any other gas) as you propose in a point - or any other material, really, even the Bose-Einstein condensate itself - eventually you can get a black hole. But all that material will be made of something else. We don't know the states of matter in the insides of a black hole, but the gravity around the event horizon is strong enough to break down anything that is not an elementary particle.

However, the pressure involved in the creation of a black hole is usually found in the core of collapsing, very massive starts (more than eight solar masses, depending on whom you ask). I do not think you would be able to create a black hole bigger than a harmless experimental micro-black hole just with machines on a planet.

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    $\begingroup$ Just to note, "the gravity around the event horizon is strong enough to break down anything that is not an elementary particle" - this is a common misconception, and its wrong. The event horizon is simply the notional (mathematical) surface within which all futures are directed inward towards the black hole. Its where nature places its visibility curtain. Its not necessarily or by definition, the surface at which gravity can rip all non fundamental particles apart, especially for a sufficient large BH. $\endgroup$
    – Stilez
    Mar 24, 2021 at 3:35

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