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Einstein-A Life in Science – Particles which travel faster than light
Einstein - a life in science Book on Amazon
There are various books available in the market but recently I read a book "Einstein-A Life In Science" by Michael White and John Gribbin. This book is meant for education for both children and adults. It is not a sort of fantasy book or a total science fiction book but it is also about truth in which I believe and also you will believe after reading it.
In this book, the author describes about some signals in the particle world, which according to quantum uncertainty principle travel faster than light. Like twins who claim they always know when something happens to the other, these particles have an uncanny connection. No matter how far apart they get, the pair of particles will always share certain characteristics. It's as if one particle always had to be red and the other one always had to be blue. If you make one of the particle red, then no matter how far away the other one is, it's going to have to switch to blue. Instantly. Faster than even a message traveling at the speed of light could tell it to change. This phenomenon is called quantum entanglement or spooky action. At a distance, this transfer of signals occurs at more than the velocity of light.
Quantum theory also allows particles to travel faster than speed of light for very short time of a moment. Do you remember Stephen Hawkings theory (which is proven to be a fact now) that even black holes emit radiations (very very small amount of radiation but they do). How do they emit particles such as neutrinos when not even light can come out of the trap of black holes? It is because for very very short time period due to uncertainty principle, these subatomic particles can travel at more than speed of light when they are passing through event horizon! If you do not believe, read BLACK HOLES AND BABY UNIVERSE by Stephen Hawking
Now the million dollar question is, does it mean faster than light communication? I am afraid the answer is still no since no useful information can be transferred using this method. It is wrong to think that entanglement means something as clear as measuring something as blue or red. The simplest message one can transmit is either yes or no. Now to decipher such message, one has to distinguish something called as the density operators but that is impossible in such cases. This is what is proved by the no communication theorem, which says that quantum entanglement doesn't allow faster than light communication.
Anyone who has studied quantum mechanics knows that the wave function or the probability wave is not real. So even if it travels at a speed far, far greater than light (which is certainly not the case), it DOES NOT imply faster than light travel or faster than light communication.