How is this possible?

[blinky1983]

Take a Black hole for example... The closer we get to one the slower time passes till we get so close that time stops. So how does anything enter it if time comes to a stand still?.If we were to observe an object nearing the event horizon that object would appear to freeze and never enter it.So how do we know that anything enters a black hole? The same can be said at the Big bang. At that moment time does not exist so how does anything become to exist??? Also how on earth does something so powerful just appear from nothing??? The mind boggles...

[Telrad]

Take a Black hole for example... how on earth does something so powerful just appear from nothing???

Yes, mind boggling. There are many theories to that question. The most common theory is where a colossal star with a mass of more than 3 times the Sun’s reaches the end of its life, it gets crushed under its own gravity, leaving behind a compact blackhole. I'm sure the others will provide interesting insight and perspectives into other theories, of course the net is another resource.

You could post your question in this forum too: Physics, Space Science and Theories - Stargazers Lounge

[Jessun]

Time will slow down for the guy travelling towards the black hole - so he thinks it's taking ages. An outside observer will see it as happening very quickly since he is not affected by the acceleration. This is boggling enough leaving only a handful of people to understand it.

For your other questions, there's no longer even a handful...

[blinky1983]

An outside observer will see it as happening very quickly since he is not affected by the acceleration.

I believe so, But The outside observer could not observe anything entering the black hole as the object being observed would remain static or frozen at the event horizon to our eyes, even though that object has already passed the event horizon...

[jgs001]

I've moved this over to the theories section... Sorry, no other comments from me on the subject... as has been said, there aren't many can follow this stuff.

[Nova]

From what I understand about one theory is that a black hole doesnt apear from no where and there are lots of different types (theoretically) of black holes. As mentioned one type, a stellar mass black hole is infact the remains of a dead star. Stars a constantly battleing there own emense gravitational forces. Neuclear reactions are working against the gravity to keep the star from collapsing. when it comes to the end of its life and has no more gas to burn gravity finally wins and the star collapses or is crushed into a small neutron star. These small stars can be only tens of killometers in diameter but are so dense that a single teaspoon of the material of a neutron star on earth would weigh millions and millions of tons. Due to the incredible, unimaginable levels of Gravity involved nothing can escape its draw, not even light which is why if we were to look at a neutron star we wouldnt be able to see it as the light can not get to our eyes, all we would see is empty space or a "black hole". This is only my understanding of this particular theory and may not be spot on as im not an astrophysicist. Feel free to pull me up on anything thats not correct

[Ant]

Time will slow down for the guy travelling towards the black hole - so he thinks it's taking ages. An outside observer will see it as happening very quickly since he is not affected by the acceleration. This is boggling enough leaving only a handful of people to understand it.

For your other questions, there's no longer even a handful...

I think it's the other way around.

To an outside observer the light takes longer and longer to escape the black hole (hence giving the appearance of slowing down and eventually stopping).

But to the person entering the black hole they accelerate into it quicker and quicker and eventually get pulled apart by gravitational forces...

Cheers

Ant

[Tutankhpip]

nothing can escape its draw, not even light which is why if we were to look at a neutron star we wouldnt be able to see it as the light can not get to our eyes, all we would see is empty space or a "black hole"

Nova I dont think this is right. As far as I know we can see neutron stars. Although they do have immense gravitational pull they are still nowhere near as powerful as black holes. Light cannot escape the pull of a black hole which is why they havent yet been directly observed

[themos]

The black hole horizon is a short cut to the end of the universe: to people watching from afar things appear to slow down as they reach the horizon. They appear to take forever to take the plunge. Which is intellectually pleasing as we don't get a preview of the end of the universe. If you actually are the one falling in though, nothing dramatic happens: you feel squished by the intense gravitational field at some point and then you arrive at the end of the universe.

[gdheib0430]

I honestly think a black hole and a neutron star are one in the same...As with neutron stars and stellar mass black holes, they are both dead stars, but the difference is said to be the size of the star that is dying. I think a black hole is the same make up of a neutron star, but because it has more mass than a neutron star the bend in space time due to gravitational forces causes the light to bend back in on the black hole hence the abscence of light. As for time slowing down, the theory of relativity is pretty much the theory to go with. I would have to re read the theories so I don't mix up what I am saying. Before I got into astronomy I have been a 10 year fanatic on watching every single cosmos show and read up on as much as possible as I find theories very fascinating.

As for the other black holes...super massive ones to be exact, for all we know they seem to just be older black holes that have sucked up enough mass to be that large.

neutron star on earth would weigh millions and millions of tons

Apparently, a sugar cube of neutron star material should weigh as much as 8000 aircraft carriers or 100 billion metric tons.

nothing can escape its draw, not even light

Material can escape a neutron star (pulsars) and have learned material can escape a black hole (quasars). This is because black holes and neutron stars spin so fast from material being drawn in that charged particles will move so close to the speed of light that they will get sling shot out along the masses magnetic fields and shot out of the weaker poles of the mass...this is why we see pulsar and quasar jets through infrared and xray telescopes. Not saying a human can escape a black hole though as they will have already been stretched and pulled apart by the time their particles get close enough to possible get ejected.

Hope this makes sense

[JulianO]

Black holes and neutron stars aren't quite the same - but are formed by similar processes. When a star runs out of fuel, it loses the ability to press out against gravity pulling it in. There are three or four possible stop points for it collapsing.

Something really small, like the Earth basically becomes very dense in the center, but its basically normal atoms.

A white dwarf has more mass, and collapses harder. Normal atomic forces can't compete against the gravity, and atoms are so squashed together that normal electron orbits and stuff can't happen, and things are squashed into quantum states, which causes a form of pressure (degenerecy pressure) which halts the collapse.

However a bit heavier, and this degeneracy pressure isn't enough to stop the collapse, and electrons are squashed into the nucleus where they combine with protons to form neutrons. This causes another type of pressure, sufficient again to stop it getting crushed up to a certain mass.

Go above this mass (which is somewhere around 1.5-2 solar masses) even the neutron pressure isn't sufficient. There may possibly be quark stars where everything is squashed to quarks and another pressure arises, but eventually you get beyond the limit (~3 solar masses if I recall) and thats when you get a black hole. Of course the 3 solar masses has to be whats left, and most big stars blow off a lot of their mass just before and during their supernova phase.

Galaxies typically have supermassive black holes at their centre, and quite how they form is a bit of a mystery still. Yes black holes consume stuff, but the accretion disk radiates a lot of energy from the infalling particles, which is sufficient to limit the flow of material. Therefore there is a limit to how quickly a black hole can consume stuff without blowing it away. Above a certain limit it can't consume stuff any faster, so quite how they get so big (and relatively quickly based on very distant early stuff) is still a mystery.

[gdheib0430]

Makes sense...would be really interesting to verify this in our lifetimes but never knew we are getting sound theories about this...was unaware neutron stars can collapse further...figured that was pretty much the most dense form of matter.

[blackparticle]

The same can be said at the Big bang. At that moment time does not exist so how does anything become to exist??? Also how on earth does something so powerful just appear from nothing??? The mind boggles...

A tricky one this.

If quantum mechanics is correct and the physical universe only exists when under the direct observation of an intelligent mind, then the 'creation' of the universe itself from nothingness could imply that it was formed from the imagination of an intelligence that existed within 0-dimensional voidic non-space.

Time itself can exist without dimensional space so the big-bang could have happened when that intelligence finally got bored and gave up existing in 0-D and all those thoughts and possibilities then came into existence.

[Klesk14]

Time didn't exist before the big bang nothing did. Which means that nothing created it because they would need time to do so when time hadn't start.

A theory of Stephen Hawkings describes how sub atomic particles behave and when the universe was that time it could have behaved in a similar way, being against all laws of science and physics where the creation of the universe simply just happened.

[blackparticle]

Time didn't exist before the big bang nothing did.

Not necessarily true. 3D space/time as defined by our science didn't exist. 0D non-space/time is perfectly possible.. In fact, an infinite amount of time could have passed before the big-bang brought this universe into creation.

[Nova]

Nova I dont think this is right. As far as I know we can see neutron stars. Although they do have immense gravitational pull they are still nowhere near as powerful as black holes. Light cannot escape the pull of a black hole which is why they havent yet been directly observed

some are visible yes. I think it takes a certain type of colapsing star to create a neutron star dense enough to be a black hole.

[DarkStar7]

Take a Black hole for example... The closer we get to one the slower time passes till we get so close that time stops. So how does anything enter it if time comes to a stand still?.If we were to observe an object nearing the event horizon that object would appear to freeze and never enter it.So how do we know that anything enters a black hole? The same can be said at the Big bang. At that moment time does not exist so how does anything become to exist??? Also how on earth does something so powerful just appear from nothing??? The mind boggles...

As an objects time is observed to slow as seen by an a stationary observer there are other relativistic effects at work that you are overlooking. An object also is subject to Lorenz contraction. Towards Zero time is towards zero size and towards infinite energy in another direction... Such as a gamma ray burst!

[George Jones]

Take a Black hole for example... The closer we get to one the slower time passes till we get so close that time stops. So how does anything enter it if time comes to a stand still? If we were to observe an object nearing the event horizon that object would appear to freeze and never enter it.So how do we know that anything enters a black hole?

Below is an analogous example that uses only special relativity, not the curved spacetime of black holes.

The inhabitants of planet Claxon have hostile intentions. We launch a preemptive missile at Claxon when our starship is 0.194 light-years from Claxon and stationary with respect to Claxon. If the missile is launched directly towards Claxon and the missile moves with constant speed 25% the speed of light, how much time elapses before the missile impacts Claxon?

Answer: time = distance/speed = 0.194/0.25 = 0.77 years.

After launching the missile, we accelerate away from Claxon at constant 1 g (to simulate Earth's gravity). We use a powerful telescope to watch the missile as it approaches Claxon. When launched, the missile was 0.19 light-years from Claxon. After watching the missile: for one year, we see the missile 0.069 light-years from Claxon; for two years, we see the missile 0.025 light-years from Claxon; for ten years, we see the missile 0.00064 light-years from Claxon.

No matter how long we watch, we never see the missle impact Claxon. We see the missile "hover" just above claxon. Yet, according to Claxon, the missile only takes 0.77 years to reach Claxon. I think most people would agree that the missile impacts Claxon, even though the people in the starship don't see this happen, no matter how long they observe. The starship also observes: light from the missile to be increasingly redshifted; a clock strapped to the missile to slow down and stop.

These are the same things that we would see if we launched a missile at a black hole.

If, however, the starship had remained stationary with respect to Claxon, the starship would see the missile impact Claxon. What the starship is able to see depends on the the path that the starship takes through spacetime. Similarly, what we are able to see in a black hole spacetime depends on the path we choose to take through spacetime. If we choose to enter the black hole, we can see the missile inside the black hole.

[blinky1983]

I love the way you explained that, Thanks

[barkis]

Frames of reference. I once heard a physics teacher use that term. It seems to embrace a lot about time, and speed. The observed, and the observers. I didn't get it then, and I still don't get it now.

Ron.

[nmoushon]

I have a question for George Jones. Well anyone really that wants to try an answer.

If what you said is correct then is it possible that "known distances" for all the stellar object that we can see are actually incorrect? That objects could actually be closer or farther away than what we think? Which ties into another question.

If black holes have so much gravitational force as to trap light then wouldn't it also suggest that it speeds up light? I.E. Sling shooting the light that is not close enough to get pulled in? If that is true or a possibility then that brings back up the question could stellar objects be closer or farther away than what we think?

[themos]

speeds up light

No! All observers must agree on the speed of light in their vicinity, that's relativity and we'd like to keep it. What gravitation can do is shrink space or time.