Black hole density












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How does more compression relate to a stronger gravitational pull. Like, when we say that a black hole is a tiny space that has 20-30 suns compressed in it, how does this increase its density and gravitational pulling power (I'm open to mathematical answers but I prefer a layman type answer for better understanding)






black-hole supermassive-black-hole density







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    From a distance, a BH of 20 solar masses has the same gravity as a normal star that size, from the same distance. It has no extra sucking power, although tidal effects get extreme when you get close, simply due to your distance from the centre. Any light or matter that falls into a BH quickly falls to the centre. Pure general relativity says it gets crushed out of existence, but we expect quantum effects to modify that, but the core of a BH will still be tiny, probably smaller than an atom under quantum gravity.
    $endgroup$
    – PM 2Ring
    yesterday






  • 1




    $begingroup$
    When stuff falls into a BH, it gets heavier, so its gravity gets stronger. There's no limit to how much a BF can consume, but if too much stuff tries to fall in at once you get a kind of traffic jam just outside the BH, and since that stuff collides at speeds approaching lightspeed, the collisions are extremely spectacular, emitting huge amounts of radiation across the spectrum, and spewing out collision debris, sometimes more than 1000 lightyears for a big active BH like M87*.
    $endgroup$
    – PM 2Ring
    yesterday






  • 1




    $begingroup$
    I've cut it down to one question, this isn't too broad.
    $endgroup$
    – James K
    yesterday






  • 1




    $begingroup$
    Similar question by the same user on Physics.
    $endgroup$
    – rob
    yesterday






  • 2




    $begingroup$
    @PM2Ring "There's no limit to how much a BF can consume" Did he eat everything in the fridge again?
    $endgroup$
    – David Richerby
    yesterday
















3












$begingroup$


How does more compression relate to a stronger gravitational pull. Like, when we say that a black hole is a tiny space that has 20-30 suns compressed in it, how does this increase its density and gravitational pulling power (I'm open to mathematical answers but I prefer a layman type answer for better understanding)






black-hole supermassive-black-hole density







share|improve this question









New contributor




noorav is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.







$endgroup$








  • 1




    $begingroup$
    From a distance, a BH of 20 solar masses has the same gravity as a normal star that size, from the same distance. It has no extra sucking power, although tidal effects get extreme when you get close, simply due to your distance from the centre. Any light or matter that falls into a BH quickly falls to the centre. Pure general relativity says it gets crushed out of existence, but we expect quantum effects to modify that, but the core of a BH will still be tiny, probably smaller than an atom under quantum gravity.
    $endgroup$
    – PM 2Ring
    yesterday






  • 1




    $begingroup$
    When stuff falls into a BH, it gets heavier, so its gravity gets stronger. There's no limit to how much a BF can consume, but if too much stuff tries to fall in at once you get a kind of traffic jam just outside the BH, and since that stuff collides at speeds approaching lightspeed, the collisions are extremely spectacular, emitting huge amounts of radiation across the spectrum, and spewing out collision debris, sometimes more than 1000 lightyears for a big active BH like M87*.
    $endgroup$
    – PM 2Ring
    yesterday






  • 1




    $begingroup$
    I've cut it down to one question, this isn't too broad.
    $endgroup$
    – James K
    yesterday






  • 1




    $begingroup$
    Similar question by the same user on Physics.
    $endgroup$
    – rob
    yesterday






  • 2




    $begingroup$
    @PM2Ring "There's no limit to how much a BF can consume" Did he eat everything in the fridge again?
    $endgroup$
    – David Richerby
    yesterday














3












3








3





$begingroup$


How does more compression relate to a stronger gravitational pull. Like, when we say that a black hole is a tiny space that has 20-30 suns compressed in it, how does this increase its density and gravitational pulling power (I'm open to mathematical answers but I prefer a layman type answer for better understanding)






black-hole supermassive-black-hole density







share|improve this question









New contributor




noorav is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.







$endgroup$




How does more compression relate to a stronger gravitational pull. Like, when we say that a black hole is a tiny space that has 20-30 suns compressed in it, how does this increase its density and gravitational pulling power (I'm open to mathematical answers but I prefer a layman type answer for better understanding)






black-hole supermassive-black-hole density




black-hole supermassive-black-hole density






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share|improve this question









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edited yesterday









James K

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asked yesterday









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  • 1




    $begingroup$
    From a distance, a BH of 20 solar masses has the same gravity as a normal star that size, from the same distance. It has no extra sucking power, although tidal effects get extreme when you get close, simply due to your distance from the centre. Any light or matter that falls into a BH quickly falls to the centre. Pure general relativity says it gets crushed out of existence, but we expect quantum effects to modify that, but the core of a BH will still be tiny, probably smaller than an atom under quantum gravity.
    $endgroup$
    – PM 2Ring
    yesterday






  • 1




    $begingroup$
    When stuff falls into a BH, it gets heavier, so its gravity gets stronger. There's no limit to how much a BF can consume, but if too much stuff tries to fall in at once you get a kind of traffic jam just outside the BH, and since that stuff collides at speeds approaching lightspeed, the collisions are extremely spectacular, emitting huge amounts of radiation across the spectrum, and spewing out collision debris, sometimes more than 1000 lightyears for a big active BH like M87*.
    $endgroup$
    – PM 2Ring
    yesterday






  • 1




    $begingroup$
    I've cut it down to one question, this isn't too broad.
    $endgroup$
    – James K
    yesterday






  • 1




    $begingroup$
    Similar question by the same user on Physics.
    $endgroup$
    – rob
    yesterday






  • 2




    $begingroup$
    @PM2Ring "There's no limit to how much a BF can consume" Did he eat everything in the fridge again?
    $endgroup$
    – David Richerby
    yesterday














  • 1




    $begingroup$
    From a distance, a BH of 20 solar masses has the same gravity as a normal star that size, from the same distance. It has no extra sucking power, although tidal effects get extreme when you get close, simply due to your distance from the centre. Any light or matter that falls into a BH quickly falls to the centre. Pure general relativity says it gets crushed out of existence, but we expect quantum effects to modify that, but the core of a BH will still be tiny, probably smaller than an atom under quantum gravity.
    $endgroup$
    – PM 2Ring
    yesterday






  • 1




    $begingroup$
    When stuff falls into a BH, it gets heavier, so its gravity gets stronger. There's no limit to how much a BF can consume, but if too much stuff tries to fall in at once you get a kind of traffic jam just outside the BH, and since that stuff collides at speeds approaching lightspeed, the collisions are extremely spectacular, emitting huge amounts of radiation across the spectrum, and spewing out collision debris, sometimes more than 1000 lightyears for a big active BH like M87*.
    $endgroup$
    – PM 2Ring
    yesterday






  • 1




    $begingroup$
    I've cut it down to one question, this isn't too broad.
    $endgroup$
    – James K
    yesterday






  • 1




    $begingroup$
    Similar question by the same user on Physics.
    $endgroup$
    – rob
    yesterday






  • 2




    $begingroup$
    @PM2Ring "There's no limit to how much a BF can consume" Did he eat everything in the fridge again?
    $endgroup$
    – David Richerby
    yesterday








1




1




$begingroup$
From a distance, a BH of 20 solar masses has the same gravity as a normal star that size, from the same distance. It has no extra sucking power, although tidal effects get extreme when you get close, simply due to your distance from the centre. Any light or matter that falls into a BH quickly falls to the centre. Pure general relativity says it gets crushed out of existence, but we expect quantum effects to modify that, but the core of a BH will still be tiny, probably smaller than an atom under quantum gravity.
$endgroup$
– PM 2Ring
yesterday




$begingroup$
From a distance, a BH of 20 solar masses has the same gravity as a normal star that size, from the same distance. It has no extra sucking power, although tidal effects get extreme when you get close, simply due to your distance from the centre. Any light or matter that falls into a BH quickly falls to the centre. Pure general relativity says it gets crushed out of existence, but we expect quantum effects to modify that, but the core of a BH will still be tiny, probably smaller than an atom under quantum gravity.
$endgroup$
– PM 2Ring
yesterday




1




1




$begingroup$
When stuff falls into a BH, it gets heavier, so its gravity gets stronger. There's no limit to how much a BF can consume, but if too much stuff tries to fall in at once you get a kind of traffic jam just outside the BH, and since that stuff collides at speeds approaching lightspeed, the collisions are extremely spectacular, emitting huge amounts of radiation across the spectrum, and spewing out collision debris, sometimes more than 1000 lightyears for a big active BH like M87*.
$endgroup$
– PM 2Ring
yesterday




$begingroup$
When stuff falls into a BH, it gets heavier, so its gravity gets stronger. There's no limit to how much a BF can consume, but if too much stuff tries to fall in at once you get a kind of traffic jam just outside the BH, and since that stuff collides at speeds approaching lightspeed, the collisions are extremely spectacular, emitting huge amounts of radiation across the spectrum, and spewing out collision debris, sometimes more than 1000 lightyears for a big active BH like M87*.
$endgroup$
– PM 2Ring
yesterday




1




1




$begingroup$
I've cut it down to one question, this isn't too broad.
$endgroup$
– James K
yesterday




$begingroup$
I've cut it down to one question, this isn't too broad.
$endgroup$
– James K
yesterday




1




1




$begingroup$
Similar question by the same user on Physics.
$endgroup$
– rob
yesterday




$begingroup$
Similar question by the same user on Physics.
$endgroup$
– rob
yesterday




2




2




$begingroup$
@PM2Ring "There's no limit to how much a BF can consume" Did he eat everything in the fridge again?
$endgroup$
– David Richerby
yesterday




$begingroup$
@PM2Ring "There's no limit to how much a BF can consume" Did he eat everything in the fridge again?
$endgroup$
– David Richerby
yesterday










3 Answers
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We can understand gravity as following a set of mathematical equations called "General Relativity" which were discovered by Einstein (and others) around the start of the 20th century. The same gravitational equations apply to black holes, stars, planets, people, apples etc. These equations are very hard to solve. Fortunately there is a very good approximation, that was discovered by Isacc Newton about 350 years ago.



It says that there is a force between any two objects that is proportional to the mass of the each object and inversely proportional to the square of the distance between the objects. The closer the objects are to each other, the stronger is the gravitational force. For normal objects (like you, and an apple) the size of this force is so small that it is almost undetectable. But if one of the objects is very big (like a planet) then it becomes a very strong force.



So if you get a couple of balls of styrofoam. They have some mass and so there is a force of gravity between them. But because they are not very dense they cannot come very close together. If you crush the styrofoam, you make it more dense. This would let you get the balls closer together, and so the force of gravity on the surface would be larger. If you don't push the balls closer together then the force between the balls would stay the same. It is the distance between the masses that is important.



A star is very massive, and its own gravity would be enough to crush it, if it didn't have a nuclear furnace inside which provides the energy to stop this. But when a star runs out of fuel, its own gravity is enough to crush the core of the star. Since you now have the same amount of mass in a smaller ball, the gravity on the surface is greater.



For a black hole this process runs away (in a way that can only be described accurately by General Relativity). The gravity gets so strong that nothing can prevent the star's complete collapse to a single point (it is a lot weirder than this, because space and time are bent by the mass). Around this is a region of space from which even light can't escape, which is why black holes look black. Furtherout from the black hole, gravity is normal. Black holes don't "suck" they just have strong gravity.



None of this answers the question "why does gravity get weaker as distance increases. Perhaps that is due to how gravity spreads out from a mass. It gets weaker in a way that is analogous to how light gets weaker as you get further from a lamp.



Nor does this explain why gravity is proportional to mass. There doesn't seem to be an answer to this (except that in a universe with no gravity, it seems likely that no structures with living creatures could form, so we wouldn't be here to ask the question)






share|improve this answer









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    It's simply because you can "get closer" to it, that's all. No special sauce.



    You know how gravity is pretty weak far away, and gets stronger close by? The closer you get to the Sun - more specifically to the center of the Sun, because that's how you measure the distance - the greater the pull.



    However, once you reach the Sun's surface, there's a problem. As you dive under the surface, the stuff above you, the layers of the Sun you're leaving behind as you keep diving in more deeply, are pulling you in the opposite direction. Part of the Sun is pulling you towards the center as before, but the other part is pulling you up. They fight each other. So gravity actually gets weaker when you dive under the surface.



    But what if the Sun was smaller? Same mass, just more compressed. Then you could get closer to it (measured to the center) without diving under the surface (which would weaken the pull). Gravity could get stronger.



    Now make it even smaller. You could get pretty freakin' close to it without touching the surface. The pull of gravity could be enormous, and from the same mass, too. It's just that the distance to the center could get smaller before you even touch it, that's what makes the difference.



    Black holes are just an extreme example of this. There's no magic, they're just super-tiny for their mass. So you can get very close to them, and gravity just keeps increasing A LOT as you do so. Eventually you reach the event horizon where gravity is so strong that space itself gets weird and you can't get out anymore.






    share|improve this answer











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    • 1




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      That last sentence is important! It's not merely that you can't get enough speed or acceleration, the spacetime is curved so much that as you go forward in time you must travel towards the core. There are no paths away from the core, or even paths that keep the same distance. (The only way out is to go backwards in time, and as far as we know that's physically impossible).
      $endgroup$
      – PM 2Ring
      22 hours ago










    • $begingroup$
      +1 for a good answer Florin, but that last sentence is wrong. You can plot gravitational potential by plotting the "coordinate" speed of light using a gedanken string of light clocks. The steeper the gradient in gravitational potential at some location, the stronger the gravity at that location. But at the event horizon, the coordinate speed of light is zero, and it can't go lower than that. So there's no more slope.
      $endgroup$
      – John Duffield
      15 hours ago












    • $begingroup$
      @JohnDuffield Are you back with crackpot "theories" again?
      $endgroup$
      – Florin Andrei
      10 hours ago



















    0












    $begingroup$

    Black hole has very high gravitational pull not because it is small but because it has huge mass. Gravitational pull does not depend on SIZE but only MASS.



    For example is EARTH is compressed to a pebble size( 10 mm in diameter) it will become a tiny black hole. However it will not affect the moon!. Moon will not understand where the earth has gone!. It will remain in the same orbit as before.






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    • $begingroup$
      This is true, but one-sided. At the same distance, it's true that only the mass of the central body matters. However, if the body is highly dense, you can get very close to it - and there the gravitational field can get extremely intense in the case of such bodies as black holes.
      $endgroup$
      – Florin Andrei
      10 hours ago












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    3 Answers
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    3 Answers
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    $begingroup$

    We can understand gravity as following a set of mathematical equations called "General Relativity" which were discovered by Einstein (and others) around the start of the 20th century. The same gravitational equations apply to black holes, stars, planets, people, apples etc. These equations are very hard to solve. Fortunately there is a very good approximation, that was discovered by Isacc Newton about 350 years ago.



    It says that there is a force between any two objects that is proportional to the mass of the each object and inversely proportional to the square of the distance between the objects. The closer the objects are to each other, the stronger is the gravitational force. For normal objects (like you, and an apple) the size of this force is so small that it is almost undetectable. But if one of the objects is very big (like a planet) then it becomes a very strong force.



    So if you get a couple of balls of styrofoam. They have some mass and so there is a force of gravity between them. But because they are not very dense they cannot come very close together. If you crush the styrofoam, you make it more dense. This would let you get the balls closer together, and so the force of gravity on the surface would be larger. If you don't push the balls closer together then the force between the balls would stay the same. It is the distance between the masses that is important.



    A star is very massive, and its own gravity would be enough to crush it, if it didn't have a nuclear furnace inside which provides the energy to stop this. But when a star runs out of fuel, its own gravity is enough to crush the core of the star. Since you now have the same amount of mass in a smaller ball, the gravity on the surface is greater.



    For a black hole this process runs away (in a way that can only be described accurately by General Relativity). The gravity gets so strong that nothing can prevent the star's complete collapse to a single point (it is a lot weirder than this, because space and time are bent by the mass). Around this is a region of space from which even light can't escape, which is why black holes look black. Furtherout from the black hole, gravity is normal. Black holes don't "suck" they just have strong gravity.



    None of this answers the question "why does gravity get weaker as distance increases. Perhaps that is due to how gravity spreads out from a mass. It gets weaker in a way that is analogous to how light gets weaker as you get further from a lamp.



    Nor does this explain why gravity is proportional to mass. There doesn't seem to be an answer to this (except that in a universe with no gravity, it seems likely that no structures with living creatures could form, so we wouldn't be here to ask the question)






    share|improve this answer









    $endgroup$


















      4












      $begingroup$

      We can understand gravity as following a set of mathematical equations called "General Relativity" which were discovered by Einstein (and others) around the start of the 20th century. The same gravitational equations apply to black holes, stars, planets, people, apples etc. These equations are very hard to solve. Fortunately there is a very good approximation, that was discovered by Isacc Newton about 350 years ago.



      It says that there is a force between any two objects that is proportional to the mass of the each object and inversely proportional to the square of the distance between the objects. The closer the objects are to each other, the stronger is the gravitational force. For normal objects (like you, and an apple) the size of this force is so small that it is almost undetectable. But if one of the objects is very big (like a planet) then it becomes a very strong force.



      So if you get a couple of balls of styrofoam. They have some mass and so there is a force of gravity between them. But because they are not very dense they cannot come very close together. If you crush the styrofoam, you make it more dense. This would let you get the balls closer together, and so the force of gravity on the surface would be larger. If you don't push the balls closer together then the force between the balls would stay the same. It is the distance between the masses that is important.



      A star is very massive, and its own gravity would be enough to crush it, if it didn't have a nuclear furnace inside which provides the energy to stop this. But when a star runs out of fuel, its own gravity is enough to crush the core of the star. Since you now have the same amount of mass in a smaller ball, the gravity on the surface is greater.



      For a black hole this process runs away (in a way that can only be described accurately by General Relativity). The gravity gets so strong that nothing can prevent the star's complete collapse to a single point (it is a lot weirder than this, because space and time are bent by the mass). Around this is a region of space from which even light can't escape, which is why black holes look black. Furtherout from the black hole, gravity is normal. Black holes don't "suck" they just have strong gravity.



      None of this answers the question "why does gravity get weaker as distance increases. Perhaps that is due to how gravity spreads out from a mass. It gets weaker in a way that is analogous to how light gets weaker as you get further from a lamp.



      Nor does this explain why gravity is proportional to mass. There doesn't seem to be an answer to this (except that in a universe with no gravity, it seems likely that no structures with living creatures could form, so we wouldn't be here to ask the question)






      share|improve this answer









      $endgroup$
















        4












        4








        4





        $begingroup$

        We can understand gravity as following a set of mathematical equations called "General Relativity" which were discovered by Einstein (and others) around the start of the 20th century. The same gravitational equations apply to black holes, stars, planets, people, apples etc. These equations are very hard to solve. Fortunately there is a very good approximation, that was discovered by Isacc Newton about 350 years ago.



        It says that there is a force between any two objects that is proportional to the mass of the each object and inversely proportional to the square of the distance between the objects. The closer the objects are to each other, the stronger is the gravitational force. For normal objects (like you, and an apple) the size of this force is so small that it is almost undetectable. But if one of the objects is very big (like a planet) then it becomes a very strong force.



        So if you get a couple of balls of styrofoam. They have some mass and so there is a force of gravity between them. But because they are not very dense they cannot come very close together. If you crush the styrofoam, you make it more dense. This would let you get the balls closer together, and so the force of gravity on the surface would be larger. If you don't push the balls closer together then the force between the balls would stay the same. It is the distance between the masses that is important.



        A star is very massive, and its own gravity would be enough to crush it, if it didn't have a nuclear furnace inside which provides the energy to stop this. But when a star runs out of fuel, its own gravity is enough to crush the core of the star. Since you now have the same amount of mass in a smaller ball, the gravity on the surface is greater.



        For a black hole this process runs away (in a way that can only be described accurately by General Relativity). The gravity gets so strong that nothing can prevent the star's complete collapse to a single point (it is a lot weirder than this, because space and time are bent by the mass). Around this is a region of space from which even light can't escape, which is why black holes look black. Furtherout from the black hole, gravity is normal. Black holes don't "suck" they just have strong gravity.



        None of this answers the question "why does gravity get weaker as distance increases. Perhaps that is due to how gravity spreads out from a mass. It gets weaker in a way that is analogous to how light gets weaker as you get further from a lamp.



        Nor does this explain why gravity is proportional to mass. There doesn't seem to be an answer to this (except that in a universe with no gravity, it seems likely that no structures with living creatures could form, so we wouldn't be here to ask the question)






        share|improve this answer









        $endgroup$



        We can understand gravity as following a set of mathematical equations called "General Relativity" which were discovered by Einstein (and others) around the start of the 20th century. The same gravitational equations apply to black holes, stars, planets, people, apples etc. These equations are very hard to solve. Fortunately there is a very good approximation, that was discovered by Isacc Newton about 350 years ago.



        It says that there is a force between any two objects that is proportional to the mass of the each object and inversely proportional to the square of the distance between the objects. The closer the objects are to each other, the stronger is the gravitational force. For normal objects (like you, and an apple) the size of this force is so small that it is almost undetectable. But if one of the objects is very big (like a planet) then it becomes a very strong force.



        So if you get a couple of balls of styrofoam. They have some mass and so there is a force of gravity between them. But because they are not very dense they cannot come very close together. If you crush the styrofoam, you make it more dense. This would let you get the balls closer together, and so the force of gravity on the surface would be larger. If you don't push the balls closer together then the force between the balls would stay the same. It is the distance between the masses that is important.



        A star is very massive, and its own gravity would be enough to crush it, if it didn't have a nuclear furnace inside which provides the energy to stop this. But when a star runs out of fuel, its own gravity is enough to crush the core of the star. Since you now have the same amount of mass in a smaller ball, the gravity on the surface is greater.



        For a black hole this process runs away (in a way that can only be described accurately by General Relativity). The gravity gets so strong that nothing can prevent the star's complete collapse to a single point (it is a lot weirder than this, because space and time are bent by the mass). Around this is a region of space from which even light can't escape, which is why black holes look black. Furtherout from the black hole, gravity is normal. Black holes don't "suck" they just have strong gravity.



        None of this answers the question "why does gravity get weaker as distance increases. Perhaps that is due to how gravity spreads out from a mass. It gets weaker in a way that is analogous to how light gets weaker as you get further from a lamp.



        Nor does this explain why gravity is proportional to mass. There doesn't seem to be an answer to this (except that in a universe with no gravity, it seems likely that no structures with living creatures could form, so we wouldn't be here to ask the question)







        share|improve this answer












        share|improve this answer



        share|improve this answer










        answered yesterday









        James KJames K

        35k257119




        35k257119























            4












            $begingroup$

            It's simply because you can "get closer" to it, that's all. No special sauce.



            You know how gravity is pretty weak far away, and gets stronger close by? The closer you get to the Sun - more specifically to the center of the Sun, because that's how you measure the distance - the greater the pull.



            However, once you reach the Sun's surface, there's a problem. As you dive under the surface, the stuff above you, the layers of the Sun you're leaving behind as you keep diving in more deeply, are pulling you in the opposite direction. Part of the Sun is pulling you towards the center as before, but the other part is pulling you up. They fight each other. So gravity actually gets weaker when you dive under the surface.



            But what if the Sun was smaller? Same mass, just more compressed. Then you could get closer to it (measured to the center) without diving under the surface (which would weaken the pull). Gravity could get stronger.



            Now make it even smaller. You could get pretty freakin' close to it without touching the surface. The pull of gravity could be enormous, and from the same mass, too. It's just that the distance to the center could get smaller before you even touch it, that's what makes the difference.



            Black holes are just an extreme example of this. There's no magic, they're just super-tiny for their mass. So you can get very close to them, and gravity just keeps increasing A LOT as you do so. Eventually you reach the event horizon where gravity is so strong that space itself gets weird and you can't get out anymore.






            share|improve this answer











            $endgroup$









            • 1




              $begingroup$
              That last sentence is important! It's not merely that you can't get enough speed or acceleration, the spacetime is curved so much that as you go forward in time you must travel towards the core. There are no paths away from the core, or even paths that keep the same distance. (The only way out is to go backwards in time, and as far as we know that's physically impossible).
              $endgroup$
              – PM 2Ring
              22 hours ago










            • $begingroup$
              +1 for a good answer Florin, but that last sentence is wrong. You can plot gravitational potential by plotting the "coordinate" speed of light using a gedanken string of light clocks. The steeper the gradient in gravitational potential at some location, the stronger the gravity at that location. But at the event horizon, the coordinate speed of light is zero, and it can't go lower than that. So there's no more slope.
              $endgroup$
              – John Duffield
              15 hours ago












            • $begingroup$
              @JohnDuffield Are you back with crackpot "theories" again?
              $endgroup$
              – Florin Andrei
              10 hours ago
















            4












            $begingroup$

            It's simply because you can "get closer" to it, that's all. No special sauce.



            You know how gravity is pretty weak far away, and gets stronger close by? The closer you get to the Sun - more specifically to the center of the Sun, because that's how you measure the distance - the greater the pull.



            However, once you reach the Sun's surface, there's a problem. As you dive under the surface, the stuff above you, the layers of the Sun you're leaving behind as you keep diving in more deeply, are pulling you in the opposite direction. Part of the Sun is pulling you towards the center as before, but the other part is pulling you up. They fight each other. So gravity actually gets weaker when you dive under the surface.



            But what if the Sun was smaller? Same mass, just more compressed. Then you could get closer to it (measured to the center) without diving under the surface (which would weaken the pull). Gravity could get stronger.



            Now make it even smaller. You could get pretty freakin' close to it without touching the surface. The pull of gravity could be enormous, and from the same mass, too. It's just that the distance to the center could get smaller before you even touch it, that's what makes the difference.



            Black holes are just an extreme example of this. There's no magic, they're just super-tiny for their mass. So you can get very close to them, and gravity just keeps increasing A LOT as you do so. Eventually you reach the event horizon where gravity is so strong that space itself gets weird and you can't get out anymore.






            share|improve this answer











            $endgroup$









            • 1




              $begingroup$
              That last sentence is important! It's not merely that you can't get enough speed or acceleration, the spacetime is curved so much that as you go forward in time you must travel towards the core. There are no paths away from the core, or even paths that keep the same distance. (The only way out is to go backwards in time, and as far as we know that's physically impossible).
              $endgroup$
              – PM 2Ring
              22 hours ago










            • $begingroup$
              +1 for a good answer Florin, but that last sentence is wrong. You can plot gravitational potential by plotting the "coordinate" speed of light using a gedanken string of light clocks. The steeper the gradient in gravitational potential at some location, the stronger the gravity at that location. But at the event horizon, the coordinate speed of light is zero, and it can't go lower than that. So there's no more slope.
              $endgroup$
              – John Duffield
              15 hours ago












            • $begingroup$
              @JohnDuffield Are you back with crackpot "theories" again?
              $endgroup$
              – Florin Andrei
              10 hours ago














            4












            4








            4





            $begingroup$

            It's simply because you can "get closer" to it, that's all. No special sauce.



            You know how gravity is pretty weak far away, and gets stronger close by? The closer you get to the Sun - more specifically to the center of the Sun, because that's how you measure the distance - the greater the pull.



            However, once you reach the Sun's surface, there's a problem. As you dive under the surface, the stuff above you, the layers of the Sun you're leaving behind as you keep diving in more deeply, are pulling you in the opposite direction. Part of the Sun is pulling you towards the center as before, but the other part is pulling you up. They fight each other. So gravity actually gets weaker when you dive under the surface.



            But what if the Sun was smaller? Same mass, just more compressed. Then you could get closer to it (measured to the center) without diving under the surface (which would weaken the pull). Gravity could get stronger.



            Now make it even smaller. You could get pretty freakin' close to it without touching the surface. The pull of gravity could be enormous, and from the same mass, too. It's just that the distance to the center could get smaller before you even touch it, that's what makes the difference.



            Black holes are just an extreme example of this. There's no magic, they're just super-tiny for their mass. So you can get very close to them, and gravity just keeps increasing A LOT as you do so. Eventually you reach the event horizon where gravity is so strong that space itself gets weird and you can't get out anymore.






            share|improve this answer











            $endgroup$



            It's simply because you can "get closer" to it, that's all. No special sauce.



            You know how gravity is pretty weak far away, and gets stronger close by? The closer you get to the Sun - more specifically to the center of the Sun, because that's how you measure the distance - the greater the pull.



            However, once you reach the Sun's surface, there's a problem. As you dive under the surface, the stuff above you, the layers of the Sun you're leaving behind as you keep diving in more deeply, are pulling you in the opposite direction. Part of the Sun is pulling you towards the center as before, but the other part is pulling you up. They fight each other. So gravity actually gets weaker when you dive under the surface.



            But what if the Sun was smaller? Same mass, just more compressed. Then you could get closer to it (measured to the center) without diving under the surface (which would weaken the pull). Gravity could get stronger.



            Now make it even smaller. You could get pretty freakin' close to it without touching the surface. The pull of gravity could be enormous, and from the same mass, too. It's just that the distance to the center could get smaller before you even touch it, that's what makes the difference.



            Black holes are just an extreme example of this. There's no magic, they're just super-tiny for their mass. So you can get very close to them, and gravity just keeps increasing A LOT as you do so. Eventually you reach the event horizon where gravity is so strong that space itself gets weird and you can't get out anymore.







            share|improve this answer














            share|improve this answer



            share|improve this answer








            edited 20 hours ago

























            answered yesterday









            Florin AndreiFlorin Andrei

            12.6k12844




            12.6k12844








            • 1




              $begingroup$
              That last sentence is important! It's not merely that you can't get enough speed or acceleration, the spacetime is curved so much that as you go forward in time you must travel towards the core. There are no paths away from the core, or even paths that keep the same distance. (The only way out is to go backwards in time, and as far as we know that's physically impossible).
              $endgroup$
              – PM 2Ring
              22 hours ago










            • $begingroup$
              +1 for a good answer Florin, but that last sentence is wrong. You can plot gravitational potential by plotting the "coordinate" speed of light using a gedanken string of light clocks. The steeper the gradient in gravitational potential at some location, the stronger the gravity at that location. But at the event horizon, the coordinate speed of light is zero, and it can't go lower than that. So there's no more slope.
              $endgroup$
              – John Duffield
              15 hours ago












            • $begingroup$
              @JohnDuffield Are you back with crackpot "theories" again?
              $endgroup$
              – Florin Andrei
              10 hours ago














            • 1




              $begingroup$
              That last sentence is important! It's not merely that you can't get enough speed or acceleration, the spacetime is curved so much that as you go forward in time you must travel towards the core. There are no paths away from the core, or even paths that keep the same distance. (The only way out is to go backwards in time, and as far as we know that's physically impossible).
              $endgroup$
              – PM 2Ring
              22 hours ago










            • $begingroup$
              +1 for a good answer Florin, but that last sentence is wrong. You can plot gravitational potential by plotting the "coordinate" speed of light using a gedanken string of light clocks. The steeper the gradient in gravitational potential at some location, the stronger the gravity at that location. But at the event horizon, the coordinate speed of light is zero, and it can't go lower than that. So there's no more slope.
              $endgroup$
              – John Duffield
              15 hours ago












            • $begingroup$
              @JohnDuffield Are you back with crackpot "theories" again?
              $endgroup$
              – Florin Andrei
              10 hours ago








            1




            1




            $begingroup$
            That last sentence is important! It's not merely that you can't get enough speed or acceleration, the spacetime is curved so much that as you go forward in time you must travel towards the core. There are no paths away from the core, or even paths that keep the same distance. (The only way out is to go backwards in time, and as far as we know that's physically impossible).
            $endgroup$
            – PM 2Ring
            22 hours ago




            $begingroup$
            That last sentence is important! It's not merely that you can't get enough speed or acceleration, the spacetime is curved so much that as you go forward in time you must travel towards the core. There are no paths away from the core, or even paths that keep the same distance. (The only way out is to go backwards in time, and as far as we know that's physically impossible).
            $endgroup$
            – PM 2Ring
            22 hours ago












            $begingroup$
            +1 for a good answer Florin, but that last sentence is wrong. You can plot gravitational potential by plotting the "coordinate" speed of light using a gedanken string of light clocks. The steeper the gradient in gravitational potential at some location, the stronger the gravity at that location. But at the event horizon, the coordinate speed of light is zero, and it can't go lower than that. So there's no more slope.
            $endgroup$
            – John Duffield
            15 hours ago






            $begingroup$
            +1 for a good answer Florin, but that last sentence is wrong. You can plot gravitational potential by plotting the "coordinate" speed of light using a gedanken string of light clocks. The steeper the gradient in gravitational potential at some location, the stronger the gravity at that location. But at the event horizon, the coordinate speed of light is zero, and it can't go lower than that. So there's no more slope.
            $endgroup$
            – John Duffield
            15 hours ago














            $begingroup$
            @JohnDuffield Are you back with crackpot "theories" again?
            $endgroup$
            – Florin Andrei
            10 hours ago




            $begingroup$
            @JohnDuffield Are you back with crackpot "theories" again?
            $endgroup$
            – Florin Andrei
            10 hours ago











            0












            $begingroup$

            Black hole has very high gravitational pull not because it is small but because it has huge mass. Gravitational pull does not depend on SIZE but only MASS.



            For example is EARTH is compressed to a pebble size( 10 mm in diameter) it will become a tiny black hole. However it will not affect the moon!. Moon will not understand where the earth has gone!. It will remain in the same orbit as before.






            share|improve this answer








            New contributor




            Mohan Mone is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
            Check out our Code of Conduct.






            $endgroup$













            • $begingroup$
              This is true, but one-sided. At the same distance, it's true that only the mass of the central body matters. However, if the body is highly dense, you can get very close to it - and there the gravitational field can get extremely intense in the case of such bodies as black holes.
              $endgroup$
              – Florin Andrei
              10 hours ago
















            0












            $begingroup$

            Black hole has very high gravitational pull not because it is small but because it has huge mass. Gravitational pull does not depend on SIZE but only MASS.



            For example is EARTH is compressed to a pebble size( 10 mm in diameter) it will become a tiny black hole. However it will not affect the moon!. Moon will not understand where the earth has gone!. It will remain in the same orbit as before.






            share|improve this answer








            New contributor




            Mohan Mone is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
            Check out our Code of Conduct.






            $endgroup$













            • $begingroup$
              This is true, but one-sided. At the same distance, it's true that only the mass of the central body matters. However, if the body is highly dense, you can get very close to it - and there the gravitational field can get extremely intense in the case of such bodies as black holes.
              $endgroup$
              – Florin Andrei
              10 hours ago














            0












            0








            0





            $begingroup$

            Black hole has very high gravitational pull not because it is small but because it has huge mass. Gravitational pull does not depend on SIZE but only MASS.



            For example is EARTH is compressed to a pebble size( 10 mm in diameter) it will become a tiny black hole. However it will not affect the moon!. Moon will not understand where the earth has gone!. It will remain in the same orbit as before.






            share|improve this answer








            New contributor




            Mohan Mone is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
            Check out our Code of Conduct.






            $endgroup$



            Black hole has very high gravitational pull not because it is small but because it has huge mass. Gravitational pull does not depend on SIZE but only MASS.



            For example is EARTH is compressed to a pebble size( 10 mm in diameter) it will become a tiny black hole. However it will not affect the moon!. Moon will not understand where the earth has gone!. It will remain in the same orbit as before.







            share|improve this answer








            New contributor




            Mohan Mone is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
            Check out our Code of Conduct.









            share|improve this answer



            share|improve this answer






            New contributor




            Mohan Mone is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
            Check out our Code of Conduct.









            answered 18 hours ago









            Mohan MoneMohan Mone

            82




            82




            New contributor




            Mohan Mone is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
            Check out our Code of Conduct.





            New contributor





            Mohan Mone is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
            Check out our Code of Conduct.






            Mohan Mone is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
            Check out our Code of Conduct.












            • $begingroup$
              This is true, but one-sided. At the same distance, it's true that only the mass of the central body matters. However, if the body is highly dense, you can get very close to it - and there the gravitational field can get extremely intense in the case of such bodies as black holes.
              $endgroup$
              – Florin Andrei
              10 hours ago


















            • $begingroup$
              This is true, but one-sided. At the same distance, it's true that only the mass of the central body matters. However, if the body is highly dense, you can get very close to it - and there the gravitational field can get extremely intense in the case of such bodies as black holes.
              $endgroup$
              – Florin Andrei
              10 hours ago
















            $begingroup$
            This is true, but one-sided. At the same distance, it's true that only the mass of the central body matters. However, if the body is highly dense, you can get very close to it - and there the gravitational field can get extremely intense in the case of such bodies as black holes.
            $endgroup$
            – Florin Andrei
            10 hours ago




            $begingroup$
            This is true, but one-sided. At the same distance, it's true that only the mass of the central body matters. However, if the body is highly dense, you can get very close to it - and there the gravitational field can get extremely intense in the case of such bodies as black holes.
            $endgroup$
            – Florin Andrei
            10 hours ago










            noorav is a new contributor. Be nice, and check out our Code of Conduct.










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