Is it possible to send super-luminal messages?

Question

In other words; Is it possible to send messages faster than the "speed of light"? Has it been done already. .or are scientists still working on this? How is it done (if it's possible), etc? Thanks to all who respond to the question.

Answer 1

Some scientisits have performed experiments where it is believed that pulses actually travelled faster than the speed of light. Check this article out :
http://news.bbc.co.uk/1/hi/sci/tech/781199.stm
It is important to note however, that they have not managed to find a way to send information faster than light, and that is the real gist of the thoery of relativity : that information cannot travel faster than the speed of light.
Some interesting experiments in quantum physics dealing with nonlocality and entanglement have also displayed what seems to be FTL travel, but again, no meaningful information could be sent with those methods - not yet, anyway.

Answer 2

In a strict sense, no. The speed of light limits how fast energy can be moved from one point to another and without energy being moved, you can't send information (a signal).

Now some particles that always travel faster than light have been postulated - they're called tachyons. With these particles, one could send information faster than the speed of light but then you get into interesting causality problems. For instance, you want to signal your friend whois vacationing on Mars and you go to your tachyon transmitter to send a message. However, your friend can receive this message before you send it - space and time are no longer neatly divided into past, present and future beccause the tachyons can be incredibly fast. Now if your friend gets the message before you send it, cna you chose not to send it? Will you get a reply before your message is even sent?

There is another class of faster than light (FTL) phenomenon related to quantum mechanics. It is teh famous Einstein-Rosen-Padowsky paradox and it goes like this. Suppose you create two photons by a quantum mechincal event like the annihilation of an electron and positron. Now the two photons have correlated properties: their momentum is such that it conserves the total linear momentum of the elctron positron pair, and their spins are such that the total spin of the electron positron pair is conserved. Photons can have spin equal to 1, 0, and -1 and electrons and positrons can have spins equal to 1/2 and -1/2. So suppose the two particles have opposite spins, the net spin is zero. The photons can have spins (1,-1), (0,0), and (-1,1). Quantum theory assigns a probability to each of these spin pairs meaning that we don't know which spin pair is realized until we make a measurement. Further, each photon has a probability of having a specific spin state and again, we don't what it really has until we make a measurement. Note we need measure the spin of only one photon as soon as we do, we know the spin of the other.

Now Einstein posed the problem that if the two photons move very far apart without interacting with anything else, and you measure the spin of one of them, the other instantly has the appropriate spin to conserve angular momentum. In quantum terms, the collapse of the wavefunction of the measured photon determined the collapse of the wavefunction of the spatially separated photon instantaneously. Light doesn't have time to travel between them. Einstein called this "spooky action at a distance" and was one of his arguments to show quantum mechanics couldn't be a true model of reality.

Researchers are trying to exploit this effect to dothings like quantum cryptography, quantum teleportation etc.

Answer 3

contrary to popular belief, there is nothing in relativity which prevents objects or information from traveling faster than light.

the problem is that nothing with any rest mass can travel AT the speed of light, and in order to get faster, if you start out slower, you have to pass through that barrier, which is impossible.

there is a principle in quantum physics called "non-locality" which states that 2 objects that were once in a system together are always related through certain physical properties. this leads to something that looks like information being passes faster than the speed of light, but really no information is transmitted, the 2 objects, though physically separated, are part of the same physical system.

Answer 4

No. If it were possible, then reference frames in which the past could communicate with the future would exist, which violates causality.

There are a lot of tests going on right now related to quantum entanglement, which give the implication of faster-than-light communication of some sort, yet, each test ends up with a hitch of some kind to prevent the possibility of actual communication. Some seem so bizarre that it's almost tempting to wonder if something "funny" is going on...


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Answer 5

No, information can't be sent at speeds above that of light. An example would be, the spot light from a search light, the search light could be rotated quickly enough to move the spot faster than the speed of light on a high, overcast layer of clouds, but it could convey no information.

Answer 6

According to what we know, it is not possible without doing some serious warping of the shape of spacetime. And some argue that it's not possible even then.

It has not been done already. And not enough theory has developed yet for scientists to be working on it.