Inside a sphere of constant density, gravity is linearly related to distance from the center.
So for example the Earth has a radius of ~4000 miles. Assuming it has constant density, a 200 pound man would be weightless at its center, weigh 0.2 pounds at 4 miles from the center, weigh 2 pounds at 40 miles from the center, weigh 100 pounds at halfway to the surface, and so on.
So the larger the star, given that most (or all) aren’t uniform, there will come a gradient of gravity at its center that one can’t even call it low gravity - it’s heavy material is simply churning too much for their to be a stable center of gravity?
I think the best way to visualize it is that when you are inside a star, you are effectively “standing” on a smaller star. Everything behind you can theoretically be ignored. When you are very close to the center, you are standing on a very tiny star.
Imagine you are standing on the surface of Earth, and you weighed 200 pounds.
Now imagine Earth were magically transported to the center of the sun, completely replacing an equal volume of solar core. Inside the very middle of the sun, standing on planet earth, you would still weigh 200 pounds. The gravity of all the solar mass surrounding the Earth would cancel out.
If you traveled upwards, to the surface of the sun, your weight would increase. At the sun’s surface, you would weigh 5400 pounds.
“If the body is a spherically symmetric shell (i.e., a hollow ball), no net gravitational force is exerted by the shell on any object inside, regardless of the object’s location within the shell.”
If you had a planet that was hollow in the center*, the entire hollow region would have zero gravity. You could have a thin-skinned planet with the entire interior an empty weightless void. I doubt any planets like this actually exist.
Assuming radial symmetry. If you can represent the planet as concentric spherical shells then you’re good.
You’re right but that was not the point. The comment just explained that at any point inside a hollow sphere gravity forces cancel out so that effectively there is no gravity.
If you had a planet that was hollow in the center*, the entire hollow region would have zero gravity. You could have a thin-skinned planet with the entire interior an empty weightless void. I doubt any planets like this actually exist.
Assuming radial symmetry. If you can represent the planet as concentric spherical shells then you’re good.
Yeah it’s a pretty counter intuitive result. I’d expect a greater pull of gravity towards the nearer side, but it turns out to be exactly cancelled out by the greater mass on the further side.
E: oops, looking at your edited comment, I should stress this is only for hollow bodies. Your comment pre-edit was correct for non-hollow bodies. If you’re part way to the middle of a planet, you can think of the planet as two sections, a small sphere for the part that’s below you, and a larger hollow shell for the rest. You experience no gravity from the outer shell, so only feel gravity of the smaller mass below. 10m from the earth’s center, you feel equivalent gravity to if you were on a 10m radius iron sphere.
Nothing will happen to the black hole, except for its continued growth. At least not anything on time scales that are meaningful for humanity. We’ll be long gone before any observable changes happens to any black holes.
I don’t think it’s likely that there is a minimum volume, at least not a discrete quantized one. It would have to be a [regular honeycomb tessellation](en.wikipedia.org/wiki/Honeycomb_(geometry)) that shows no bias towards any particular direction (i.e. no corners). There are no shapes that fulfill both of those conditions in 3D space.
String Theory has been folded into (no pun intended) Quantum Field Theory, which fixes some of what the original theory got wrong. Have you seen any videos from PBS Space Time, on YouTube? If not, I’d highly recommend the following videos on the subject (probably in this order):
I sure do love the implications of our universe consisting of interactions between excitations in a bunch of fields, the rays of which carry energy much like a plucked string. If that’s right, it could be rendered as audio; we would be listening to the music of the universe. It might not be good, but it would be beautiful! 😂
Why is #1 an issue? You’re assuming physics at a subatomic level works the same as that at a macroscopic level, but they don’t. Things don’t have well defined boundaries.
I think the premise of a „pixel“ being the smallest entity in software is not right. Rasterization, i.e. translating (actually reducing) a defined subset of the software state into a 2D grid of colored pixels, is only a very limited view on that software.
This might be the reason for the different answers we‘re getting here. Most aim for subatomic physics, it we could also go to light theory (photons and wave frequencies/resolution) and human retinas, general optics and electron microscopes, which again would end up at subatomic physics (you got my circle-train of thought here).
A better question would be, “when does hair know when to fall off?”
Hair never stops growing.
Edit: when I say “hair,” I mean one single strand of hair. That single strand of hair will eventually fall off. The thing is that not all strands fall off at the same time. So hair, the full head of hair, seems to be of the same length (especially if we keep getting haircuts.) But it’s not like all hairs grow and then all of them collectively say “ok, everyone, let’s stop growing!” and stop. No, each single strand of hair falls off, but at different times.
What’s „unhelpfully pedantic“ about a correct answer that explains OPs misconception? 🤡
The person above said hair doesn’t stop growing. That’s wrong. It does. It grows, then it stops growing, then the dead hair falls out. Why does it know when to fall out? Because it’s dead, Jim.
OPs question was why the hair on their head grows longer. Answer: because it’s growing cycles are longer.
I’d say you’re unhelpfully pedantic telling other people giving helpful and correct explanations they’re „unhelpfully pedantic“.
I’d say you’re extremely unhelpful because you give an „explanation“ that’s just complete bullshit and doesn’t explain anything.
So I have a follow up question, let’s say someone has 20cm long hair, all of them are that long, we don’t see 5/10cm hair still growing to get to 20, I’m confused, how does that work?
Have you ever seen someone’s arm after they have a cast taken off? Your arm hair is short because it’s being rubbed off by random interactions with things (rubbing against shirts you take off/put on, your body, general use). A person with a cast on their arm protects those hairs, and when they finally get the cast off, they look like a werewolf.
It’s weird how often I get comments from people days later, who think they know what they’re talking about about, but are missing a piece that explains it.
If you’re going to comment on old threads, try asking a question. I probably would have explained for you and you could have learned something.
That was 3 hours later, not really old besides he’s correct: hair doesn’t grow differently because of it’s lenght but because of it’s placement on the body.
See the other answers for why this isn’t really right, but given 4 dimensional spacetime, if that ‘pixel’ did exist, it would look like a hypercube/tessaract. A constantly stretching and twisting but approximate one, anyway.
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