[MasTaBlau]

Here is some interesting information about black holes that does not get extremely technical.
http://www.phys.vt.edu/~jhs/faq/blackholes.html#q2

[Kk21pwa9]

I'm not totally convinced that one would not feel anything different in a slower-than-Earth rate of time, especially in an environment as severe as a black hole, because the time dilation is unique only to the person at the black hole. If he were to observe another person a good distance away from the hole, he should notice that this other person's time is faster than his; however, since his actual rate of time is slower, his own rate of observations cannot be "normal". What your brain would make of this is a quite a puzzle.

[MiniBoy]

this question makes me feel kind of weird. :/

if two black holes come together, will they join forces to become super duper or will they try and kill each other?

Black holes dont annihilate one another, they will eventually merge to become supermassive (a relatively active supermassive black hole actually powers quasars and blazars). Using the term black hole doesnt really describe what the object really is. First off they arent black, you cant actually see a black hole but you can either see its accretion disc or detect one by observing gravitational lensing caused by the black hole itself

Black holes arent actually holes either, a black hole is the result of gravity winning out. Its basically a lot of matter condensed onto one single point. a black hole actually has the mass of thousands/billions/trillions of stars and therefore has a tremendously powerful gravitational field. The more massive the object the more attraction or force it exerts on another. You can see this effect by observing the relationship between our sun, earth and its moon. The Sun exerts a pull on the earth but the earth also exerts a pull on the Sun. The sun also exerts a pull on the moon, but because its much closer to the earth the pull of the sun on the moon is negligable in comparison. The moons pull on the earth is what causes our tides, you can see the effects of the earths pull on the moon also because its tidally locked so we always see the same side as is rotates around the earth. The moon is actually moving away from us so as our solar system evolves the moon will eventually fall out of orbit around the earth and will eventually assume an orbit around the sun when its so far away from earth.

In the case of two merging black holes, the actual mass of both would eventually merge together and make a new black hole even more dense than either of the two were previously. the newly formed one would then be considered a Supermassive black hole, before this formation the two would orbit eachother slowly getting closer over time, this would be a binary black hole. Black hole triplets have actually been observed, at the beginning of last year, 3 quasars were found orbiting each other in the virgo constellation

As long as your far enough away from the black hole your not in any danger of being pulled into it. At a certain distance its gravity isnt enough to actually pull anything towards it. It can still effect the trajectory of an object and even light in which it can slightly bend it as it passes. Earth is in no way in danger of being pulled into a black hole. The closest star to earth our sun doesnt have enough mass to form a black hole when it dies, Neither do any of the stars in the Alpha Centauri system which is the closest system to ours, just about 4.5 light years. The largest star in Alpha Centauri is just a tiny bit more massive and brighter than our sun

[Kk21pwa9]

The moon is actually moving away from us so as our solar system evolves the moon will eventually fall out of orbit around the earth and will eventually assume an orbit around the sun when its so far away from earth.

I don't know where you've read that but whoever has suggested that, doesn't have any evidence for it and for two reasons: (1) the Earth's orbit is also increasing in size due to the Sun constantly losing mass, thus the Sun's influence on the Moon is decreasing, and (2) computational models of the Moon's orbit predict it to remain Earth-bound for any reasonable meaning of the word "future" and beyond that, the models are too unreliable.

[MiniBoy]

I'm not totally convinced that one would not feel anything different in a slower-than-Earth rate of time, especially in an environment as severe as a black hole, because the time dilation is unique only to the person at the black hole. If he were to observe another person a good distance away from the hole, he should notice that this other person's time is faster than his; however, since his actual rate of time is slower, his own rate of observations cannot be "normal". What your brain would make of this is a quite a puzzle.

If time relative to us was to slow down to half the speed we wouldnt know about it, our brain would process things at a slower rate. only an outside observer could observe the dilation as you already know

However as you get closer to it, just like tidal forces would differ throughout your body so could the passage of time, blood flowing in your head (if you were going in feet first) would flow faster than the blood at your feet. it would get even stranger if the black hole was spinning, because of the difference in time your feet would be orbiting slower than your head. If tidal forces didnt pull you apart in the direction of the black hole that would pull you apart in the direction of the spin.

I would highly recommend to stay away from black holes just in case

[MiniBoy]

I don't know where you've read that but whoever has suggested that, doesn't have any evidence for it and for two reasons: (1) the Earth's orbit is also increasing in size due to the Sun constantly losing mass, thus the Sun's influence on the Moon is decreasing, and (2) computational models of the Moon's orbit predict it to remain Earth-bound for any reasonable meaning of the word "future" and beyond that, the models are too unreliable.

I didnt read it anywhere, hypothetically if it moved far beyond earth and it had enough time the next strongest pull would likely be the sun. but yeah the sun will be long dead before the sun in its current stage could have more of a pull on the moon than the earth. i didnt actually think about what i said though considering if its orbit moved far enough out mars could even exert more of a tug than the earth on it

[Kk21pwa9]

If time relative to us was to slow down to half the speed we wouldnt know about it, our brain would process things at a slower rate. only an outside observer could observe the dilation as you already know

That would only be the case if you observed nothing but items within the same gravitation potential as yourself - the moment you observe anything else, the difference would be apparent. Your point also assumes that the brain would function "normally" in such gravitational conditions, whereas I believe otherwise (and thus would be the indication to the person that they are in a "slower time region"), but, alas, there's currently no means of testing this.

However as you get closer to it, just like tidal forces would differ throughout your body so could the passage of time, blood flowing in your head (if you were going in feet first) would flow faster than the blood at your feet. it would get even stranger if the black hole was spinning, because of the difference in time your feet would be orbiting slower than your head. If tidal forces didnt pull you apart in the direction of the black hole that would pull you apart in the direction of the spin. If the change in gravitation potential was sufficient enough to cause noticeable differences in time dilation across one's own body, the tidal forces would sadly also be large enough to ensure that the sudden awareness of the dilation would be rather short-lived.

[treawittelf]

would not all brain process slow by the same amount? meaning we wouldn't notice the slowing of time at all?

i know you said we are not sure how the slowing of time would affect each part of the brain but i don't understand how the slowing of time could affect parts of the brain differently.

[Kk21pwa9]

Although it's never been my field, I've not yet come across any specific theoretical work that tackles what would happen to biological systems in extreme cases of time dilation. It's simple enough for unstable sub-atomic particles (they just "last" longer), and on a quantum level there's no problem either, but who knows what effects it might produce on macroscopic scale. But even if our body continued to function as normal, we would certainly notice the dilation effect the moment we try to observe something that's not in the same region as us.

[fabrizioitwloch]

I reckon that we would become increasingly less aware of what's going on around us - to the point that we'd be totally "duhhh" long before hitting the event horizon.

So that's what is wrong with society these days....

I was just about to mention that I work with people whose lives reflect that first statement.

[mpegdvdclip]

neeyik, you seem pretty knowledgeable in this subject, what kind of field did you study in or did it come to you through just plain pleasure reading?

[SeLvesTr]

I never see a black hole before so I don't know

[gWhya5ct]

I was just about to mention that I work with people whose lives reflect that first statement.

You've dicovered black holes on earth! [shocked]

[Kk21pwa9]

neeyik, you seem pretty knowledgeable in this subject, what kind of field did you study in or did it come to you through just plain pleasure reading?

My first degree was in Physics & Maths, and I specialised a bit in astrophysics, but it mostly comes from being a physics teacher for 10 years, before joining FM!

[IoninnyHaro]

I'm guessing black holes work similarly to tornadoes. When two combine they join forces. But my question is, what if the two where spinning in the opposite direction. Would they cancel each other out? We are talking about two black holes with equal gravitational pull and size. Or do black holes spin in only one direction. And if so, why?

[Kk21pwa9]

I'm guessing black holes work similarly to tornadoes. When two combine they join forces. But my question is, what if the two where spinning in the opposite direction. Would they cancel each other out? We are talking about two black holes with equal gravitational pull and size. Or do black holes spin in only one direction. And if so, why?

Black holes, like any stellar object, can spin in either direction but if just take our own particular galaxy, the majority of objects whose spin is known rotate in the same direction - the reasons for this are multiple and complex, but they all revolve around the conservation of angular momentum (e.g. this is why all the planets and asteroids orbit the Sun in the same direction that it's rotating). Spinning black holes also drag space-time around them, like a mad dog with a toy, so it's likely to be a very "messy" merger, but they would still merge (and because of the conservation of angular momentum, the resulting new black hole would be spinning even faster).

[9rCR9hWL]

yup, that's why I mentioned spin would make things very messy in my previous post - there is also the "problem" of the magnetic fields andI'm sure you've all seen pictures of 'holes with streams of ejecta from the poles due to the magnetic fields - these can be hundreds, if not thousands, of light years long.
Get two of these at 90 degrees and all sorts of interesting things may be evident.

[IoninnyHaro]

I know I'm getting a little off topic here. But don't blackholes create a radiation I believe is known as Hawkins radiation? Is it possible to create that radiation in a science lab?

[9rCR9hWL]

Neeyik will be able to answer properly but, as I understand it, it is electromagnetic emmisions and is irreguler. As such, it can't really be reproduced but I would assume the frequencies could be although the energy levels may be a bit harder to reproduce.

[Kk21pwa9]

Hawking radiation is not only photons but all kinds of particles, constantly emitted by black holes (which therefore makes them "non-black"!). Although it's never been directly detected, neither have black holes, and if one accepts the theoretical propositions behind black holes, then Hawking radiation is a likely must too. It's caused by the fact the particle pairs of matter and antimatter continuously pop in and out of existence, but never long enough to be directly detected (although their accumulative presence can be: do a Google search on the Lamb shift or Casimir effect to see what I mean).

However, particle pairs that pop into existence right on the edge of the event horizon of a black hole run the chance that one of the particles may cross over that boundary - if that happens, then the pair can never recombine again, causing various problems with physicists brains, as the conservation of energy is the most fundamental rule that all of nature follows (regardless as to whether it's physics, biology, chemistry, geology, etc). The problem is saved by assuming that the particle that passes the event horizon has negative energy, leaving us to observe a positive energy particle being emitted by the "edge" of the black hole. In other words, the black hole appears to be emitting mass.

The reason why the theory has not yet been verified is that the rate of "evaporation" (the emission of Hawking radiation) is pathetically slow, and most stellar black holes would need longer than the age of the universe to completely disappear (the rate increases over time, so in the final moments, the black hole emits the last of its mass in an almighty burst of particles).

There's nothing particularly special about Hawking radiation though, it is just the same particles that we experience in the world about us.