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Time Travel (pg. 3)
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| eye_03 |
| quote: | Originally posted by zarathustra
Your assumption is wrong because the boat example is flawed. If the speedometer of the boat reads 10 mph, then the boat is travelling at 10 mph no matter what the velocity of the river current. It's the same as for a car. The speedometer says 50 mph even though the Earth is rotating much faster than that. To accelerate the beam of light, your breath would have to travel faster than the beam. |
if your reference point is the shore, then he is correct, the boat is going at 30 mph
ty physics:whip: |
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| DJ Mikey Mike |
| quote: | Originally posted by Acid Junkie
some astronomers believe that when u travel through a black hole, u go through a tunnel callde a wormhole where u are changed changed into pure energy (according to einstein.) then u come out of a so-called white hole. if a white hole exists, it should be asmall body in space that sends out a lot of pure energy. other astronomers believe a worm hole is a portal to other univreses. they believe that matter changes going through a black hole and creates a new universe with its own spacetime continiuum.
in other words worm hole = tunnel to a white hole at some other point in spacetime
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hmmm i always liked the theory that the opposite end of a black hole is a quasar (ie. a white hole)..
but the term worm hole in its simplest term i guess would be a shortcut thru space by the folding of space. Like for example, if u are at one end of a piece of paper and u want to get to the other side in the quickest possible time, the best way to do it would be to fold the piece of paper in half and just step across. And as far as time travel goes, at the moment, the only way to do this would require worm holes to actually exist (which atm we dont even no if they do exist) and we would also need to be able to reach greater speeds than that of light. As already explained a few posts above, when travelling at the speed of light you dont encounter the same time as everyone else. Like you could go speeding away from earth at the speed of light and come back within minutes to find everyone on earth has ages thousands of years. But in theory it is this that makes time travel possible. If you could somehow take hold of one end of a worm hole and go flying off with it at a velocity of over the speed of light, then come back to the starting point, then in theory what you have done is made one end of the worm hole one time period, and the end which u dragged flying off into space at great speeds in a different time period.. and therefore if u were to step thru that worm hole ud be stepping from one time frame into another.. hurrah! uve just travelled thru time 
hope i havnt bored anyone there but i find this sort of topic fascinating. |
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| Acid Junkie |
| quote: | Originally posted by DJ Mikey Mike
but the term worm hole in its simplest term i guess would be a shortcut thru space by the folding of space. Like for example, if u are at one end of a piece of paper and u want to get to the other side in the quickest possible time, the best way to do it would be to fold the piece of paper in half and just step across. And as far as time travel goes, at the moment, the only way to do this would require worm holes to actually exist (which atm we dont even no if they do exist) and we would also need to be able to reach greater speeds than that of light. |
ya, that's what they often wright in science fiction stories. what they don't say is that even if worm holes really exist, chances are u will be torn apart and fried long before u've gotten to the other end :stongue: |
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| DrUg_Tit0 |
| quote: | Originally posted by DJ Mikey Mike
hmmm i always liked the theory that the opposite end of a black hole is a quasar (ie. a white hole)..
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Nice point you made, but just so you know, a quasar is not a white hole. Quasars infact consist of a black hole in the middle and a very hot cloud of gas around it that's generating large amounts of energy when it is falling into the hole. And while the existance of black holes and quasars is a quite common phenomenon, the existance of white holes has so far not even been hinted at. Infact, most physicist consider their existance very unprobable. Unlike a black hole, a white hole is in contradiction with the simple laws of thermodynamics. A white hole is spewing matter out of nowhere, while a black hole is gathering matter into a singularity, but at a same time radiating thermal energy equal in amount to the swallowed matter. When a wormhole is left with no matter around it to feed itself, it basically converts all of it's matter and energy into thermal energy which it radiates into the surrounding area, and eventually, it deteriorates itself to nothingness. |
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| DrUg_Tit0 |
| Btw, if anyone is interested, there's a nice book I'm just reading, "The Nature of Space and Time" from Stephen Hawking and Roger Penrose. The book is pretty interesting, but to understand it fully I'd say you need at least two years of university-level physics/mathematics worth of knowledge. Anyway it says a lot about black holes and the nature of space-time, but it doesn't say much about time travel and such. |
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| Acid Junkie |
| stephen hawking? is he the guy who speculated that black holes supposedly radiate with a black body spectrum and thus lose their mass and eventually die :conf: sounds good except no one was ever able to detect that radiation ;) |
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| DrUg_Tit0 |
| Yes, that's him, but it's not just a speculation, it's a physical model that does make sense. But the radiation hasn't been detected because all black holes we observed so far are surrounded by clouds of hot gas, which make it impossible to detect fainter radiation those black holes might emit. |
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| djSlain |
| I did a research project on Isaac Asimov and he states (or theorizes) that wormholes are open randomly throughout space for only fractions of MORE fractions a second. I'm guessing that if we ever want a chance to ride into one, we need to slow down time so we can see and enter the wormhole, and see where it leads to |
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| occrider |
| quote: | Originally posted by DrUg_Tit0
Yes, that's him, but it's not just a speculation, it's a physical model that does make sense. But the radiation hasn't been detected because all black holes we observed so far are surrounded by clouds of hot gas, which make it impossible to detect fainter radiation those black holes might emit. |
Dammit just found this intersting thread. Anyway yes blackholes can die because they radiate.
| quote: |
In classical Newtonian physics, black holes are black. But on a quantum mechanics level, they radiate an exceedingly small number of particles, mostly photons.
Nobody has verified this weird phenomenon, called "Hawking Radiation", but it makes sense in a strange way.
According to Heisenberg's Uncertainty Principle, our space vacuum teems with invisible particles that flash into and out of existence like virtual fireflies.
Suppose a pair of particle-antiparticles pops into being, conveniently enough, within effective range of the black hole's gravity.
Before the pair can annihilate each other, the black hole grabs the pair and, using the hole's rest-mass energy, pulls it into two particles. "...one particle has negative energy and the other has positive energy," says Andrew J.S. Hamilton, astrophysical and planetary sciences professor at the University of Colorado. "And the black hole swallows the negative energy, allowing the positive energy particle to go to infinity."
The black hole loses the energy contained in the escaped positive-energy particle, consequently loses an equal amount of rest mass, and eventually--after enough positive-energy particles escape-loses all rest mass and dies.
Don't hold your breath. The death of a black hole can take ten raised to the 61st power times the age of the Universe for a 30 solar-mass black hole. Mini black holes-the mass of a small mountain-can evaporate in less than the age of the Universe.
The black hole glows extremely dimly. The Hawking luminosity of a 30 solar-mass black hole is a miserable ten raised to the minus 31 watts. Bigger black holes are colder and dimmer.
So, on a quantum mechanics level, a black hole isn't completely black. It glows faintly.
Emitted x-rays are another matter completely. The black hole doesn't emit the x-rays. Rather it pulls hot gas away from its Sun-like companion star if it has one. The gas forms a flattened disk swirling around the hole. The gas particles knock into each other zillions of times as they rotate and heat to extreme temperatures: hot enough to emit x-rays.
The gas particles reach the right temperature when they are close to the event horizon. (The event horizon marks the critical limit where the escape velocity of a collapsing body becomes equal to the speed of light and hence no information can reach an external observer). Then they spit X-rays in all directions and less than a second later disappear. See illustration.
In the figure, the swirling material (white circles) is hot gas pulled from the black hole's companion star. The gas reddens and dims due to a gravitational red shift as it approaches the event horizon (black center dot). Photons lose energy in the presence of a strong gravitational field and this causes a shift to lower frequencies, i.e., a red shift. When the gas crosses the event horizon, it disappears.
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So if the universe is forever expanding as is indicated then the entire universe will eventually die out into nothingness. |
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| occrider |
| quote: | Originally posted by DrUg_Tit0
Btw, if anyone is interested, there's a nice book I'm just reading, "The Nature of Space and Time" from Stephen Hawking and Roger Penrose. The book is pretty interesting, but to understand it fully I'd say you need at least two years of university-level physics/mathematics worth of knowledge. Anyway it says a lot about black holes and the nature of space-time, but it doesn't say much about time travel and such. |
Also a good book that I'm reading is the Whole Shebang Theory by timothy ferris. Again some college phsyics is a plus. If you want something a little bit lighter maybe try Hawking's The Universe In a Nutshell. |
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| DrUg_Tit0 |
| quote: | | Before the pair can annihilate each other, the black hole grabs the pair and, using the hole's rest-mass energy, pulls it into two particles. "...one particle has negative energy and the other has positive energy," says Andrew J.S. Hamilton, astrophysical and planetary sciences professor at the University of Colorado. "And the black hole swallows the negative energy, allowing the positive energy particle to go to infinity." |
This kinda doesn't make sense. The hole has equal chances of grabbing both negative and positive particles. So if we rely on vacuum fluctuations alone, positive and negative energy fluctuations should cancel each other out on a large scale. |
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| occrider |
It is not up to you or I to question why but to do or die.
But seriously I'm sure the actual explanation goes a little bit more in depth. I'm not going to even try (unless I get bored) and look up specifics since I'm sure it's very complicated and likely over my head. |
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