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Thanks. So, building a ray gun, that's 100,000,000,000 batteries? I better start saving up my money!

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My dogs too lazy! He finds it much easier to sit in the middle of the floor and cry until someone just gives him the sausage!

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Earl... is this "nothing" the dark energy i keep hearing about? :undecided:

Edited by Vince1963

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Unless of course the Laws of Physics are different within a black hole, but that, my friends we may never know!

But isn't this true, that some scientists believe that this could be the case?. that black holes defy all physical laws, and could black holes just be the curved fabric of space (Albert Einstein) with no actual opening or exit (like water going down a plug hole but with no actual exit)(i'm not very good at explaining this) where all matter collects going round and round the vortex adding to the mass creating ever more energy...Till one day (who knows) it implodes on itself (big bang) creating the birth of a new universe maybe parallel to the one we know maybe there's others. maybe this is where we started from and its a continuous cycle.. We may never know. I'm sure you may have an answer for me Badgerchap lol :icon_salut:

Edited by Vince1963

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What confuses me is that Black Holes do not emit light, yet they have sufficient mass and probably sufficient supplies of hydrogen (from cannibalising other stars) to ignite, and the question is, why are they completely black? Surely the core would emit some light..

Just read the answer, but couldn't it ignite? Could a Black Hole already be ignited, and be living as a star surrounded by dark matter...hm..?

Edited by Naemeth

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What confuses me is that Black Holes do not emit light, yet they have sufficient mass and probably sufficient supplies of hydrogen (from cannibalising other stars) to ignite, and the question is, why are they completely black? Surely the core would emit some light..

Just read the answer, but couldn't it ignite? Could a Black Hole already be ignited, and be living as a star surrounded by dark matter...hm..?

Pretty sure they are pretty much supermassive stars in essence. It isnt that they dont emit light, its that any light past the event horizon doesnt have sufficient energy to escape the gravity of them.

Which begs the question - does gravity have a top speed? The sun is 8 light minutes away, if we were to remove it instantly, we would still see light for 8 minutes, but would we still be influenced by its gravity for 8 minutes?

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Well Stephen Hawking's 'solution' to the information paradox says that black holes eventually evaporate - I'll happily expand on this in the morning if you;re interested. Otherwise, there are two (generally pointless) arguments here:

1) There is nothing to suggest that the laws of Physics are different within a black hole, and

2) There is nothing to suggest that the laws of Physics are not different within a black hole,

We are entering into the realms of conjecture now - if you're up for it, I'll happily enter into a debate in the morning, but right now I've had a few shandies, and wouldn't want to put my foot in my mouth!

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The singularity is where modern physics breaks down (last time i read a book anyway hehe)

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if you're up for it, I'll happily enter into a debate in the morning, but right now I've had a few shandies, and wouldn't want to put my foot in my mouth!

...

go for it :)

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Ahh OK, I'm going to attempt to address some of this right now.

Black holes do not emit any light in the way that we understand. The mass of a black hole is so great that any matter or energy of which we are currently aware cannot escape. However, Hawking suggested that a certain form of radiation can be emitted, and this radiation has since been observed.

To understand this, we have to look at something called 'virtual particles'.

We must first address the nature of a true vacuum. For centuries, the nature of the vacuum has been the subject of extremely complex investigation.

If you have a region of space with no matter in it, is it a vacuum if light passes through it?

No, because light may pass through it and light carries energy, and therefore mass. So if we have an area of space with no matter and no light, is it a vacuum? Well that depends on whether or not electric and magnetic fields pass through it.

So what if we have a region of space with no matter, no light, and no electromagnetic fields, is this a vacuum?

No.

It has been proven (I'm not going to tackle this now - too inebriated!) that within a perfect vacuum, such a thing as vacuum energy causes vertial particles to spontaniously appear from nothingness for a tiny period of time. ( I think this is the Caismir effect, but would appreciate a correction if I'm wrong!)

The edge of a black hole can be thought of in the same light (no pun) as a vacuum, in that any light/matter etc beyond the event horizon is permanently consumed, and any before the event horizon is still within the realms of normal physics.

However, from time to time, virtual particles will appear (as they do throughout the universe) exactly on the border between the event horizon of a black hole and normal space. Now if both particles appeared on one particular side of the EH, they would annihilate, leaving nothing but vacuum energy, but when one virtual particle (called a) appears on our side of the EH, and one particle (called B) appears on the far side of the EH, we achieve an inequilibrium. Particle b cannot escape the black hole and is consumed, whereas particle a escapes the black hole and is released into the universe, carrying a small amount of energy with it. In this way, the black hole slowly loses energy, and so will eventually run out of energy and evaporate (on the scale of 10 to the power of a heck of a lot of years).

So black holes cannot emit light, or any other kind of energy in ways which we might ordinarily recognise, but they do eventually lose energy over a long period of time.

PHEW! My inebriated brain is now immensely tired and needs to sleep. Doubtlessly I will be corrected by others, but this is what I understand of black hole's radioactive emission!

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Thanks for the info, very interesting stuff! Isn't it true that (hypothetically speaking), time itself is dilated to a point of practical infinitum when you approach a black hole, so if you were, as it were, falling into a black hole, you'd be "screaming" for a infinitely long (or certainly very long) time?

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PM me!

It was a light hearted request :)

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Earl... is this "nothing" the dark energy i keep hearing about? :undecided:

No one has defined exactly what Dark energy is, the jury is still out as they say

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Although Dark Energy is supposed to be what is causing the Universe to expand at an accelerating rate, if that is, it is still expanding.

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Yes, Time dilation and also length contraction occur when either in the vicinity of a massive object (a black hole) or when an object gets close to the speed of light. However, it is only the time as measured by an observer that changes, to the person falling into the black hole or travelling at the speed of light, the experience of time does not change.

The degree of time dilation cannot cause an infinite time though. At the point the 'scream' would become infinite, the person falls past the event horizon and is lost, or in the other case reaches light speed, which as we saw earlier is impossible :)

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Well that's black holes sorted out (sort of) so on to the next subject!

White Holes!

Some scientists theorize that the could exist the problem is that we haven't detected one yet. Presumably you could actually see a white hole. I wonder though, could you (several thousand years into the future) pilot a ship into a white hole (providing you don't crash) and survive?

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Well we're seriously into the realms of conjecture now! I'll be completely frank - I can only give you my personal opinions on White Holes. Some physicists have done serious work on this, but I have read little of it as they are more of a mathematical curiosity than a known physical phenomenon (but so were black holes not that long ago!).

If we were to assume that White Holes did exists, and that they were the perfect opposit of a black hole, then some physicists have suggested that it might be possible to fly into a black hole and out through a white hole.

However, as a black hole cannot be escaped, we must assume that the opposit of this would be that a white hole could never be reached, i.e. that they would curve spacetime so steeply that you could never have enough energy to reach it.

Wormholes have also been suggested, and there are some truly amazing things that emerge when they are taken into consideration. For example, they could transport a person or ship between two very distant places instantaneously, thus circumventing the light speed limit (you still wouldn't exceed the speed of light - rather you would be taking a shorter route). However, this opens up a can of worms too ugly for most physicists to digest. They open up the highly prohibited world of paradoxes.

This is a bit mind bending for me, so I'm going to wimp out and direct you to wikipedia:

http://en.wikipedia.org/wiki/Twins_paradox

Just replace the light-speed spaceship with a wormhole, and look what happens! If you look at the page on paradoxes as well, note the grandfather paradox, which also prevents backwards time travel!

Sorry I'm not explaining all this myself - I could, but it'd be mightily long winded, and as you can see, someone's kindly already taken on this complcated task on wikipedia!

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Could it be possible that the light contained within a black hole is actually a white hole, and all the light that this produces is bound by the outer black hole? It would at least explain why we haven't found one, it may also explain why black holes have such immense gravity.

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Well, a model for a black hole is where an incredibly heavy ball is dropped onto a sheet and It creates a nearly infinite dip in it, but not a hole. If a white hole is opposite then it would create an almost infinite bulge. So if a white hole and a black hole where in the same place then presumably these effects would cancel each other out.

My brainstorming just then triggered another theory!

A model for a white hole should be an incredibly heavy ball dropped onto a sheet from the other side! In 2D with sheets then you would think " a heavy ball dropped on the other side of the sheet would fall to the floor" but when you look at it in a 3D point of view then you realize than another dimension, or another universe, must be involved!

I am only in Yr9 at school so I am missing a lot of the basic physics so the chances are I've missed something. till, quantum physics is fun!

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By the way badgerchap. If I have a physics exam next year I will probably be asking you for help!

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Why we cannot see white holes.

Science fiction fans love the possibility of other universes, even more so contemplating the possibility of being able to travel between them through exotic configurations of spacetime, notably wormholes, which are pretty much just black holes with an opening poking through the singularity.

Less well known is the equally exotic (and purely hypothetical) possibility of "white holes:" the opposite of black holes. Whereas matter and light can fall into a black hole and never escape, white holes would emit light and matter but wouldn't take anything in, for example.

But while we see evidence for black holes in space, thus far there hasn't been any observational evidence of white holes. Now a physicist at the University of Oregon in Eugene thinks he might be able to explain why.

Here's the standard analogy for the formation of a wormhole: Picture a bed sheet stretched taut. Place a large bowling ball in the center of the sheet, and the sheet will bend inward in response, creating a gravitational pull.

Now imagine that the bowling ball is being squeezed, so that the same amount of mass must fit into a smaller and smaller space. The ball will become denser and denser as it becomes smaller and smaller. This causes the sheet to dip lower and lower, until finally the ball has been squeezed down to the size of a pinhead.

At that point, its density becomes so great and the gravitational force so strong that it pokes a small hole in the center of the sheet. That’s what would happen if a wormhole formed at the center of a black hole.

But what lies on the other side?

Always a stickler for symmetry in his equations, Einstein hypothesized that a “mirror universe” must exist on the other side: a "white hole."

If you think of a black hole as a large funnel with a long throat and then “cut” the throat and merge it with a second black hole that has been flipped over (a “white hole”), you end up with something that looks like an hourglass or a funnel, with the two ends connected by a thin filament. This so-called Einstein-Rosen bridge (named for Einstein and his collaborator, Nathan Rosen) is an early theoretical incarnation of a wormhole.

Back in 1971, an astrophysicist named Robert Hjellming of the National Radio Astronomy Observatorypublished a paper in Nature proposing that white holes could be more than mirror images of their black counterparts. Matter could actually fall into a black hole and re-emerge elsewhere in space -- or even in a completely different universe, a notion proposed by British physicist Roger Penrose a few years earlier -- via a white hole.

Hjellming even speculated that white holes might account for the huge amount of energy being emitted from distant quasars and the centers of galaxies -- far more than scientists could account for at the time by known physical processes.

That was 1971; this is now. Scientists know quite a bit more about our vast universe than they did 40 years ago. That excess energy coming from quasars? It's probably coming from supermassive black holes as matter falls in and emits telltale radiation in the process.

That doesn't mean the properties and characteristics of white holes aren't mathematically interesting, and thus worth contemplating, Hsu argues. After all, for decades black holes were mostly hypothetical, too.

Is it possible that white holes are hiding in plain sight? In the 1970s, Stephen Hawking demonstrated that when a white hole and a black hole are in thermal equilibrium with their surroundings, they absorb and emit the same amount of radiation -- and thus it's impossible to tell them apart. So maybe some of the objects we think are black holes could be white holes in disguise.

But that's a very specific circumstance. Hsu decided to investigate how white holes might behave in a vacuum (i.e., in isolation), when they would not be in thermal equilibrium with their black hole counterparts.

Prevailing theory is that black holes evaporate slowly over time, gradually shedding matter in the form of "Hawking radiation," but the white hole would neither absorb or emit radiation when isolated in space.

What happens to a white hole that is thus, well, constipated? Hsu postulates that it must explode, thereby releasing huge amounts of energy: "quasithermal radiation." He concludes that stable white holes simply can't exist in empty space, and that's why we see no evidence for them. They most likely exploded into quasithermal radiation long before we had the tools with which to observe them.

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also on another note white holes as we know are the opposite of black holes, objects into which nothing can enter but are constantly spewing out matter. They were thought to be completely hypothetical, more a mathematical oddity than a real thing, , but they say, they may have seen one. White holes have been talked about before in some detail, but the basic idea behind them is the law of physics aren't comfortable with things that happen in only one direction. In other words, if black holes exist, then it should be possible to reverse the equations governing them so that you get something that's reversed but otherwise identical. That's what a white hole is.

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Could it be possible that the light contained within a black hole is actually a white hole, and all the light that this produces is bound by the outer black hole? It would at least explain why we haven't found one, it may also explain why black holes have such immense gravity.

I'd better try and explain what black holes are, or at least are expected to be:

When a dying star of above about 3 or 4 solar masses (at the time of death - would be much more massive at birth!), after a number of fusion reactions are exhausted, the pressure of radiation pushing outward ceases to be strong enough to resist the force of gravity pulling inwards. The star collapses, there is a ginormous explosion - a core collapse supernova - and the whole lot continues to force itself inwards into a black hole.

Now I'm massively glossing over the details here, but this is, in the simplest of terms, why a black hole has so much gravitational influence. The star before the black hole had the same (more in fact), but because of the radius of the star due to radiation pressure (when the star was in a state of hydrostatic equilibrium), this gravitational influence is spread out over a large volume. In a black hole, the 'singularity' has, essentially, no dimensions, so all of this matter is concentrated within an infinitessimally small point.

Here's a crazy figure for you: At a hypothetical point 1 meter from a 4 solar mass singularity (it would be a naked one, but ignore that for now that's for another time), acceleration due to gravity (g) would be:

g=GM/r^2

g=(6.67 x 10^-11) x (7.95568 x 10^30)/1^2

g = 5.31 x 10^20 ms^-2

That's over 531 million trillion meters per second per second! And that is why absolutely nowt could escape, because within a fraction of a second, any object at this distance would be travelling at light speed towards the centre!

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