Hi all

Just a quick question that popped into my mind. If there is a huge black hole in the centre of galaxies does that mean eventually it will 'eat/suck in' that galaxy??

Thanks,
Star

think of the sun, planet orbits, the sun is very big and the gravity is very strong but we are not pulled into it, just around it. even mercury is not pulled in, maybe in time the orbit will degrade but that will take a very long time. the same goes for the stars the stuff that is too close will get pulled in, everything else would just be in a large orbit.

This idea would contradict the idea of the universe expanding and would instead mean that we are on a path of imploding into this destructive black hole, which so far the evidence is there that we are in fact expanding out.

But just the thought that the center of all of this amazing universe lies the darkest and massive of forces sometimes makes me wonder if the birth of the universe is from this point...does everything just end up becoming a black hole at some point.

Each black hole has something known as the event horizon or the point of no return. Basically, if you cross the horizon, you are going to get sucked in. Let's assume that our sun is a black hole with 1 solar mass. In that case, all of the planets would still revolve around the black hole without any orbital changes because the planets are well outside of the event horizon.

most scientists believe in what i'm about to say. Super massive black holes (ones in the center of all galaxies) have the ability to destroy and create at the same time its true stars get sucked in to them. A black hole gets larger the more it sucks in the more it feeds the morepowerful the pull becomes the matter streamming into these black holes reaches the speed of light and that creates lage amounts of heat and radiation these areas are called "quasars"the can also emmit lots of light.if the circumstances are right these areas can interact with incomming matter in just the right way to for brand new stars, some blackholes can give birth to 100's if not 1000's of stars a year. Blackholes could be the orgin of all the stars in the universe all that needs for the recipe of our universe is hydrogen mixed with helium using the new handy superduper mixer i call massive blacky.lol. Black holes not only make stars but they destroy them as well. Blackholes giveth and the blackholes hath taketh away.

Thank you for the responses. So basically we live in a very weird balancing act...

Also if they create stars on such a big scale where do these stars go? Do they just travel outward from the black hole until they 'bump' into something and then start a new star system or do the immediately start star systems right by the black hole because of their gravity?

This is not really a correct analysis. The overall expansion of the universe takes place on a scale much larger than that of individual galaxies. Individual galaxies (of which some 100 billion are currently visible) expand away from one another. The stars within each galaxy are affected very little by this cosmological expansion since their motions are mainly determined by much stronger gravitational forces local to their own galaxy (e.g. the central, supermassive, black holes that exist within most galaxies). Stars that are close to the central black hole will often get pulled in. Those farther away will just rotate around it for a very, very, long time as an earlier poster has suggested. As to whether everything just ends up becoming a black hole at some point, that depends. If the density of matter in the universe, the universe's rate of expansion, the value of the cosmological constant, and other parameters fall within certain ranges, General Relativity dictates that the universe will eventually cease expanding and recollapse ("big crunch"). At the present time, the best observational evidence indicates that this is not the case and that the universe will keep expanding forever.

I think you're getting the word galaxy mixed up with the word universe.

My best guess is that most stars just travel outward. From what I remember, the light created from the black hole can be millions of light years long and at this point, a star is well outside the event horizon.

I don't believe I did, do you mind explaining your statement? I was simply trying to state that as a whole the universe is at a state of expansion and I was not speaking about individual galaxies.

As Sagredo stated:



Please help direct me if I'm interpreting this information incorrectly.

The universe, as a whole, is expanding no doubt. The point is only that this has very little to do with Stargirl's question. The fact that galaxies many millions of light years away are receding from me owing to the gradual expansion of the space separating us has hardly any effect on what happens when I drop a stone. The stone falls to the ground. It does not get slowly carried up into the sky! This is simply because the local spacetime curvature (i.e. gravity) associated with the Earth massively overwhelms any tiny influences from the universe's large-scale behavior. Likewise, if a star gets too close to a black hole, it will be pulled into the accretion disk and, eventually, consumed. The slow recession of distant galaxies can do nothing to save it. Hope this clarifies things.

-Regards

Thank you for the explanation, actually this does help clarify Stargirl's question, I guess I was a bit off track on responding to her, my apologies for misdirecting the thread.

the spin of the galaxy is so fast because of the black hole and that means the frame dragging will keep most mass from entering the core, and over time black holes degrade into small particles, so it is like a really fat man on a diet in a Chinese place, he wants to but cannot.

We basically live in a weird balancing act yes. But if we were pulled into the "black hole" it will be by the time our little sun has made its own black hole.

Our sun will die not with a bang but a whimper. It is too small to go supernova and so will simply burn out. It will not produce a black hole.

I didn't really think about that. I've read all kinds of things about our sun, how it will eventually become a red giant, etc. But that's good to know that the fate of earth wont' be sucked into a giant vacuum.

Ok next question:

If the black hole consumes the nearest stars that stray over its event horizon does that not expand/add to the black hole thereby altering its density which leads it to it having a greater gravitational force? This would mean that it would then gobble up more stars as the event horizon has moved further out? Am I going off on a tangent here?

Thanx Star

hey even if it were possible, (even though its not) you wouldn't have to worry thats will take billions of years and you won't be able to see that.

They don't get bigger because the matter they suck in gets crushed into a single point known as a singularity.

Ok but here is what I dont understand if the matter is crushed into a single point where does its properties go? (like mass?) If matter cannot be destroyed then where does this go to? Surely it has to be added to something else then if it is not added to the Black holes properties...

According to scientists, inside a black hole nothing is the same as outside of it, the physics totally change (quantom physics or quantom mechanics).

Everything that falls into a black hole falls into this point, of course it is not crushed but transformed, "Matter cannot be created or destroyed, but transformed".

According to general relativity, a black hole's mass is entirely compressed into a region with zero volume, which means its density and gravitational pull are infinite, and so is the curvature of space-time that it causes. These infinite values cause most physical equations, including those of general relativity, to stop working at the center of a black hole. So physicists call the zero-volume, infinitely dense region at the center of a black hole a "singularity".

The singularity in a non-rotating, uncharged black hole is a point, in other words it has zero length, width, and height.

Thank you for that explaination

Anytime, that's what I'm here for.

Pretending that the Sun was able to become a black hole, the Earth wouldn't be pulled in. It would continue to orbit normally because gravitational field strength is proportional to the mass of an object, the Sun wouldn't gain any mass when becoming a black hole.

In fact if anything it may lose mass as it becomes a supernova.