Tachyons, perhaps.
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Tachyons, perhaps.
- Sy Borg
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Re: Tachyons, perhaps.
My favourite dark energy hypothesis is that it's caused by clumps of antimatter exerting repulsive gravity (antigravity) from the relative voids of intergalactic space. news.nationalgeographic.com/news/2012/0 ... e-science/
It makes me wonder if intergalactic travel is physically even possible - I can't imagine good things happening to a space craft made of matter passing through a vast antimatter field. Or maybe it would have the potential to act as wormholes?
Yep, it's fun to speculate
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Re: Tachyons, perhaps.
I can definitely see a case for antimatter being the cause of an accelerating universe, if the clumps were as big as planets. This would seem to give rise to a sort of "annihalition buffer zone" , where matter and antimatter encounter each other. A tremdendous amount of energy to be had there, as well. This is assuming space is a generally uniform construct, which we can not know for sure.
- Sy Borg
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Re: Tachyons, perhaps.
I wonder if experimental clues could be found in the experiments by physicist, Kater Murch, where quantum particles were found to be affected by affected by future observations? ibtimes.co.uk/time-runs-bizarre-quantum ... re-1487456. We knew quantum particles were affected by current observations but they are also equally pulled and pushed by the past and future.
Maybe something moving faster than light is involved in those interactions?
- Diploid
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Re: Tachyons, perhaps.
Time travel to the future is possible, but there's a catch (see below). Believe it or not, EVERY time you move with respect to something else, you travel into the future with respect to the not-moving object. This is a consequence of the theory of Special Relativity.
The time predictions of the theory have long ago been confirmed experimentally and are actually used in practical applications like GPS where very accurate timing is important. If the very slight time travel of the GPS satellites were not corrected for in the equations that characterize the system, GPS would not work. I mean this literally. GPS satellites time travel into the future. Really!
In fact, everything that moves with respect to something else time travels. When you fly somewhere in an airliner, you time travel. The only reason you don't notice it is because at ordinary day-to-day human speeds, the effect is very tiny so your wrist watch can't detect it. But this has been confirmed using very accurate atomic clocks. Two atomic clocks are exactly synchronized, then one is left on the ground while the other flies in an airplane. When the plane lands, the two clocks are compared and the result is that the flying clock's time is a few nanoseconds ahead of the one that remained on the ground. This effect is called Time Dilation and it's a central theme in relativity theory. The faster the moving object goes, the more time dilation occurs.
Weird, eh? Well, it gets weirder.
Light (or radio waves which are just light at a frequency our eyes can't detect) takes about 10 minutes to get from here to Mars. If we sent an astronaut to Mars, we couldn't have an ordinary radio conversation with him. We'd have to say something into the microphone, then wait 10 minutes for him to get the message. When he replies, we'd have to wait another 10 minutes to hear the reply.
Now imagine you hop on a rocket that travels very close to c (physicists use the lower-case letter "c" to represent the speed of light). Understand that when I say "very close" I mean REALLY very close. Even though there's a tiny numerical difference between 99.999% c and 99.999999999999999999999999% c, there's a very big difference in the resulting time dilation. It's what math geeks call asymptotic. So I'm talking 99.(a million more nines)% c here. Extremely close to c but just a hair less. So imagine you hop on a rocket that travels that fast and head out to Mars. When you get there, it will have seemed (to you) like only one second passed. Your heart beat once and you're there. Your watch second hand ticked just once and you're there. But time will seem normal to you. You wouldn't notice anything different at all, just the passing of one second of time.
But back on Earth, everyone watching your trip saw it take a whole 10 minutes. Their heart beat many times and the minute hand on their watch ticked off 10 minutes.
If you had a telescope looking at people on earth, in the one second that passed for you during the trip, you saw people on Earth zipping around very quickly. If you pointed your telescope at Big Ben, the clock tower in London, you would have seen the minute hand zip across 10 minutes during your one heartbeat that it took to get to Mars.
Meanwhile, if someone back on Earth pointed a telescope at you in the rocket, he would have seen you nearly frozen still for the whole trip. He would have seen the second hand on your watch tick off one second during the 10 minutes your trip took from his point of view.
So you see that if you get to Mars and immediately turn around and return to Earth, when you got back, you would have experienced two heartbeats and your watch's second hand would have ticked twice. But if you compare with every else's watch, you would notice that your watch would be 20 minutes behind everyone else's.
Now weirder still. Imagine that instead of Mars, your trip was WAY out to the Andromeda Galaxy. Here's a pic I made in 1993:
Andromeda is 2.5 million light years away. It takes light (from our point of view) 2.5 million years to cover the distance there. Now imagine hopping on your rocket again and taking off for Andromeda. When you get there, it will seem like to you as if an hour passed. You wouldn't have to wait 2.5 million years because, again, due to your very high speed, time dilation makes your personal time pass differently than it does on Earth. But again, you wouldn't notice anything different. You'd walk around, maybe have some lunch, read a book, then an hour later (to you) you're at Andromeda.
But back on Earth, 2.5 million years passed. If someone on Earth pointed a telescope at you, they would have seen you almost frozen still because you will have done one-hour's worth of activity during 2.5 million years from Earth's point of view. If you pointed a telescope back at Earth, you would have seen a blur of activity. For every second that ticked off on your watch, 40,000 years will have passed back on Earth. Civilizations would have come and gone every time your watch ticked off one second. But other than the strange sight in your telescope, everything else would seem perfectly normal to you. One hour would pass and your trip is over.
Now here's the catch I mentioned. If you get to Andromeda then turn around and head back to Earth, you'd arrive in another hour from your point of view. A two-hour round trip (for you). But Earth will have experienced another 2.5 million years during your return trip. A total of 5 million years will have passed on Earth after your 2-hour round trip. All your friends and family will be long dead and you'd have a huge electric bill from that night-light you forgot to turn off when you left.
So in this sense it IS possible to time travel into the future. In two hours (to you) 5 million years (to Earth) passed and so you time traveled 5 million years into the future. And again, this is not hypothetical. This is a verified effect and so well-understood that it allows us to create the GPS system which wouldn't work without this understanding.
OK, now time travel into the past.
Although there is no known hard limit on time travel into the past, most physicists consider it unlikely to be possible. There are mathematical results that show backward time travel can hapen, but it's believed with high confidence that they're spurious. Here's a simple example of how these results can come about and why they're unlikely to have any physical relevance.
Recall from high school geometry class how to figure the surface area of a square. Say you have a square piece of plywood with a surface area of 9 square centimeters. What is the length of each side?
Well, if the square's surface area is 9 square cm, then each side must be square root of 9 centimeters long. The square root of 9 is 3 because 3 x 3 = 9.
The piece of wood is 3cm x 3cm. That gives you a total of 9 square cm of wood. The problem occurs in that 9 has two square roots, 3 and -3 because 3 * 3 = 9 and also -3 * -3 = 9.
But it is meaningless to say that the square in question has sides of length -3 cm even though the math tells you that such a square with negative length sides would indeed have a surface area of 9 cm. The math is interesting from an academic point of view, but it has no relevance to the physical world because pieces of wood can't have negative lengths.
This theme repeats in the concept of the Tachyon (faster than light particle) which is another mathematical curiosity that has nothing to do with reality. If tachyons existed, they would have a mass of something absurd like square root of -1 grams, which is meaningless (actually, it would be square root of -1 times some coefficient, but that's not important here).
I never say never, but it seems likely that time travel into the past is a similar curiosity but with no physical relevance. I'd love to be proven wrong though.
There's a related question that hasn't been settled regarding the quantization (granularity) of time. Is there a minimum interval of time that has physical meaning? There are some good theoretical reason that this might be true and some experimental evidence that suggests it.
This might be a little too technical for this thread, but the geeks in the audience will get it so I'll throw it out. Consider the energy of a photon. It is the product of a physical constant (Planck's constant) times the frequency of the light the photon represents. Because E = hc / lamda and c = lamda * v, therefore E = hv. But frequency (v) is the reciprocal of time, so they're in lock-step. Each frequency represents exactly one period (one time interval).
It is known that only discrete frequencies are possible for a photon. No in-between frequencies are allowed by the quantization of quantum mechanics. So if there is a one-to-one mapping from frequency to period (time interval), and only certain frequencies are possible, then only certain time intervals are possible. No in-between time intervals can occur in the wavelength of light. At least with respect to photon energy.
That's not anywhere near proof that time is quantized, but it one point of evidence (and there are others) that has some potentially deep implication. The time it takes for a photon to experience one wavelength is discontinuous. It can take a certain amount of time or a certain longer amount of time, but it can never take an in-between amount of time. Again, not proof, but food for thought.
I'll shut up now.
- Mgrinder
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Re: Tachyons, perhaps.
An interesting question, I don't know. There is no reason to think that tachyons, if they exist, would not have gravity too. Thus would not be a source for dark energy. However, I suppose it could be a source for dark matter, like neutrinos. Dark energy is usually hypothesized to be a field that permeates all space by physicists, and this field creates a repulsive "pressure" on the universe, but it is not a force. The tachyons would have to create such a field somehow.Shado wrote:If tachyons exits, is it possible that some of them are somehow slowed to the speed of light? Wouldn't this cause them to radiate some type of energy, and possibly quite a lot of it? Might this be the nature of "dark" energy, or possibly a source for "dark" matter? I sure don't know, but it is fun to speculate!! I do know, howver, it is possible to solve some actual inductive-capacitive circuits using "imaginary" numbers.
The thing about tachyons is that you can use them to telephone yourself in the past. Creating time paradoxes, so they probably don't exist. At one point there appeared to be evidence that neutrinos were tachyons, so there was this joke: "The bartender says 'Hey, we don't serve neutrinos in here'. A few minutes later, a neutrino walks into the bar". He hee.
BTW, quantum mechanics uses imaginary numbers too, and wouldn't work without them.
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Re: Tachyons, perhaps.
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Re: Tachyons, perhaps.
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Re: Tachyons, perhaps.
Think about what tachyons would look like in a Newtonian universe, where photons have infinite speed and cause and effect can't exists...Shado wrote: ↑June 16th, 2015, 7:58 pm If tachyons exits, is it possible that some of them are somehow slowed to the speed of light? Wouldn't this cause them to radiate some type of energy, and possibly quite a lot of it? Might this be the nature of "dark" energy, or possibly a source for "dark" matter? I sure don't know, but it is fun to speculate!! I do know, howver, it is possible to solve some actual inductive-capacitive circuits using "imaginary" numbers.
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Re: Tachyons, perhaps.
It's a pitty the link dont work no more. Antimatter causing repulsive gravity? Ain't the energy of antimatter positive?Sy Borg wrote: ↑June 16th, 2015, 8:22 pm How do you visualise them? Like neutrinos, just whizzing around with no obvious purpose or function, barely interacting with matter?
My favourite dark energy hypothesis is that it's caused by clumps of antimatter exerting repulsive gravity (antigravity) from the relative voids of intergalactic space. [url=http://news.nationalgeographic.com/news/2012/02/120215-dark-energy-antimatter-physics-alternate-space-science/]news.nationalgeographic.com/news/2012/0 ... e-science/[/url]
It makes me wonder if intergalactic travel is physically even possible - I can't imagine good things happening to a space craft made of matter passing through a vast antimatter field. Or maybe it would have the potential to act as wormholes?
Yep, it's fun to speculate
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