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Ignoring the impossibility of the sun suddenly collapsing, and the energy release (which would kill us): If the sun suddenly turned into a black hole, could we survive if we had sufficient energy for heat, light, etc?

Qmechanic
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DarkLightA
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  • I'm quite confused by your question. Can you explain me your last sentence..? – Waffle's Crazy Peanut Mar 03 '13 at 14:26
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    I'm asking whether us orbiting around a black hole rather than the sun would make it impossible for us to survive, even if we have enough energy from oil and other sources for heating and light? – DarkLightA Mar 03 '13 at 14:34
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    Re the "sufficient energy" bit: reading this question immediately reminded me of a classic Fritz Leiber short story "A Pail of Air" - http://en.wikipedia.org/wiki/A_Pail_of_Air - which is concerned with what could happen to the earth if it was ejected from the solar system (removing the warmth of the sun by replacing it with a black hole amounts to the same thing of course). – timday Mar 25 '13 at 19:13
  • I'm voting to close this question as off-topic because that's not a question about physics. – stafusa Mar 08 '19 at 12:53

1 Answers1

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I assume that what you basically mean is that

Suppose there is infinite food and energy for our survival, but if the Sun turns to a Black Hole, will it pose a threat to us?

The answer is NO. We would just be orbiting it as we do now. There is no reason why should there be any effect on gravitational force on Earth from the Sun, since it is dependent on total mass and distance from Sun's center to Earth's center. None of these factors change.

If you're still confused, pay attention to the fact that there is a supermassive(about a million times the Sun) black hole at the center of our Galaxy and the whole Galaxy is orbiting it in a way, nothing really happens to it.

Always remember that black holes are not something which sucks everything around it. If that would have been the case, the universe would be far more empty. They have got a bad impression just because they don't let light escape, not because they suck everything around them.

Cheeku
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  • Alright, I'll start building my survival pack!

    Haha, no, but I'm wondering: if an object gets close to a black hole will it actually be sucked in, or will it just get "slingshotted" back out?

     – DarkLightA Mar 03 '13 at 14:50
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    No, it will be sucked in. I mean a black-hole is harmless if you're at Earth behaving like a good boy to it. But if you get close enough, you'll be ripped apart.

    The point is this: Although, the gravitational force at any point will remain same, the tidal forces will increase. So, while a normal Sun will just push you in at a particular distance, a black hole Sun will rip you apart. That's why black-holes have a bad reputation.

     – Cheeku Mar 03 '13 at 14:56
  • Right. Does this mean it will be more likely to gain mass than the sun? – DarkLightA Mar 03 '13 at 14:58
  • Ya..it's a black-hole after all. It'll definitely be more likely to gain mass. It "may" even gather an accretion disk, which is in theory supposed to be a beautiful sight from earth. http://en.wikipedia.org/wiki/Accretion_disc – Cheeku Mar 03 '13 at 15:00
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    Huh, why though? When the gravity remains constant, won't everything that would hit the black hole also have hit the Sun? – DarkLightA Mar 03 '13 at 15:03
  • Those disks look sweet! – DarkLightA Mar 03 '13 at 15:04
  • @DarkLightA Those things would never have got so close. The surface of Sun is a limitation, and even if you go inside, the sphere which influences gravitation reduces in size so the gravitation is pretty sweet. But a black-hole is really small. You have a possibility of going too close to it, but you don't stand a chance with the sun. The point is this : When you're already inside a massive body, the gravitation depends on density and distance from center. A black-hole is really dense, so can pull with a greater force after you get close enough to it as compared to Sun. – Cheeku Mar 03 '13 at 15:07
  • @DarkLight And yes, you're right, those things would have already hit the Sun, but they would(like comets) have gone around it and came back. A black-hole gathers accretion disk by ripping those objects(like comets) apart. Sun, doesn't do that. It simply gobbles them or lets them go, depending on distance. The influence is same. But a black-hole rips and a sun swallows. – Cheeku Mar 03 '13 at 15:09
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    But any object getting so close to a black hole would already have hit the sun, thereby increasing its mass, right? – DarkLightA Mar 03 '13 at 15:09
  • let us continue this discussion in chat – Cheeku Mar 03 '13 at 15:10
  • Yes you will be slingshot if it is a super massive black hole, but not too far you will be again pulled by the black hole infact it happen's at the center of our galaxy. Here is the image (http://upload.wikimedia.org/wikipedia/commons/thumb/c/c1/Galactic_centre_orbits.svg/220px-Galactic_centre_orbits.svg.png) and here is the video (http://en.wikipedia.org/wiki/Supermassive_black_hole) – Deiknymi Mar 03 '13 at 15:13
  • @DarkLightA Yep...Akash is right. Slingshot is what causes it to cause an accretion disk, while the sun can't. The thing doesn't go away out to form an orbit. If it gets too close, the kinetic energy pulls it away, but in the end, it is either consumed by the black-hole or in an equally common case, formed to an accretion disk. But the disk will also go in eventually. :) – Cheeku Mar 03 '13 at 15:16
  • "They have got a bad impression just because they don't let light escape [...]"--This is a problematically posed statement. First of all, they don't let anything escape once the thing is inside the horizon just as much as they don't let light escape. Moreover, if we consider only the outward radial motion, a photon outside the event horizon will never fall back into the black hole--but a massive particle will if it has low enough energy. –  Mar 06 '19 at 20:56