4 ms·
The use of the term "bigger" here is frustrating. Mass or volume?
by iameli 4y ago
The use of the term "bigger" here is frustrating. Mass or volume?
- jmyeet 4y agoBlack hole volume is entirely a function of mass.
- philipov 4y agoBlack holes don't have a volume, they only have a surface area, and it depends strictly on their mass.
- ravi-delia 4y agoAnd spin/charge, no?
- nathan_compton 4y agoThis isn't true at least in the case of the ordinary black hole solutions in general relativity. These solutions tend to be valid throughout the volume of the black hole (except at the singularity, which takes on different shapes depending on spin or charge but doesn't occupy the whole interior volume of the black hole if you think of the event horizon as bounding the volume).
- tyfon 4y agoI thought they were valid throughout the volume/radius, but that the solution only gives you the surface area for that radius, not the volume. Perhaps I have misunderstood though as I am just a hobbyist :)
- nathan_compton 4y agoThe volume inside the event horizon isn't what you would expect if you consider the black hole as a sphere with its external area, but it has a volume. It might be the case that in quantum gravity there isn't an interior, but in GR the idea of the volume is a little weird, but not problematic.
- unclenoriega 4y agoDefinitely mass. (It is "ultramassive", after all.) An explanation of black hole volume I found from NASA [1]: > Our intuitive sense of volume breaks down in the strong gravitational region in a black hole. So while the "size" of a black hole is given by the radius of its event horizon, it's volume is not determined by the usual 4/3pir3. Instead, relativity makes it more complicated than that. As you pass the event horizon, the spatial direction 'inwards' becomes 'towards the future'-- you WILL reach the center, it's as inevitable as next Monday. The direction outsiders think of as their future becomes a spatial dimension once you are inside. The volume of a black hole, therefore, is its surface area times the length of time the hole exists (using the speed of light to convert from seconds to meters). Since a black hole last practically forever, the black hole's volume is almost infinite. (This is also a way of explaining the fact that you can pour stuff into a black hole forever and never fill it up. Another reason why black holes never fill up is that the radius of the event horizon increases as the mass of the black hole increases.) [1] https://imagine.gsfc.nasa.gov/ask_astro/black_holes.html https://imagine.gsfc.nasa.gov/ask_astro/black_holes.html
- cal85 4y agoThank you for quoting this passage. My mind is spinning after reading it.
- dustingetz 4y agoa particle falls into a black hole. does it ever stop falling, from the particle’s reference frame?
- r0uv3n 4y agoFor a non spinning black hole in general relativity, the particle reaches the singularity within finite time in its own reference frame.
- dustingetz 4y agothanks, does it fall infinitely far to do so?
- deleted 4y ago[deleted]
- trilbyglens 4y agoBBC article innit. Hardly a scientific paper.