faster than light?

Question

alright, here's my question

A----------------------------------- B

person a is 10,000 light years away from person b. person a sends a signal to person b that reaches him instantly. why is this not possible?

I guess what i'm driving at is why do people always say that person b would get the signal before it was sent?

Answer 1

"Just some guy" has got it. We don't understand everything and things can be connected in ways we don't understand. Linked particles when separated have been shown in some tests to react to forces put upon the other particle at the exact moment the event occurred even though they had been separated by some distance. Twins have been known to feel things that occur to their twin on the other side of the world.

Quantum physics deal with many intangibles, theoreticals. There absolutely could be something faster than light. There could be things that predate the universe or even time and energy the way we understand it.

But, as far as science goes in the way that we understand it, you could say that there is no way that a person a could send a message to person b ten feet away and they receive it instantly. The amount of time may be negligible, but time passes nonetheless.

To assume we understand all things completely is arrogance. Just because something can't be proved doesn't mean it is incorrect.

Answer 2

Wow, 20 answers and not a single one of them is correct.

The question has nothing to do with quantum mechanics or Bell's Inequality. The QM signals those people are talking about don't qualify as "signals" since they can carry no information.

The correct answer to the question is that in Relativity, different observers disagree on which events are simultaneous. A and B are in the same reference frame (they're not moving relative to one another) and so they both agree that B received the message at the same time A sent it.

However, consider a third observer, C, who is moving to the right. As measured by C, the two events "A sends the message" and "B receives the message" are not simultaneous. In fact, C will measure that B receives the message before A sends it.

This is because the two events (sending and receiving) in your question have a space-like separation; a light beam cannot connect them. Observers disagree on which of two space-like events happens first. As long as nothing can travel faster than light, this disagreement makes no difference. But if there are things that travel faster than light, then events A and B can affect each other, but it is undefined which one comes first, and this violates the law of causality (AKA "Cause and Effect.") This is one of the reasons we say that nothing can travel faster than light.

Events that can be connected by a light ray or any other object have time-like separation. People still disagree about how much time passes between the two events, but there's no disagreement about which one came first.

This disagreement about which events are simultaneous is a direct consequence of the constant speed of light, and is true for the same reasons that length-contraction and time-dilation are true. But it's a long discussion to get from "speed of light is constant" to "different observers disagree on which events are simultaneous."

For the full answer, read David Mermin's book, "Space and Time in Special Relativity."

Answer 3

All signals use the electromagnetic spectrum to send data. All frequencies of the EM spectrum propagate at the speed of light. There is no energy, signal, or process that can move faster than the speed of light, that restriction is built into the structure of the Universe. Person B will always get the signal 10,000 years after person A sends it.

Answer 4

When you person A tosses a baseball to person B, who is 20 feet away, the ball has a specific speed and requires a specific amount of time to cover the distance.

Through a vacuum (i.e. space) electromagnetic radiation travels at about 300,000,000 meters per second. A light year is the distance light travels in a year. So, the message you sent to person B would be received 10,000 years after you sent it, and probably person B would be dead.

To send an instant message, you would have to go through the 5th dimension, which is quite impossible for us to do. For an explanation of dimensions, see:
Part 1: http://www.youtube.com/watch?v=JkxieS-6WuA
Part 2: http://www.youtube.com/watch?v=ySBaYMESb8o

Answer 5

Because nothing travels faster than light. So it would take at least 10,000 years for the signal to reach (from the view of an outside observer)

Answer 6

There's no GMT or Universal Time in the Universe (pardon the pun), so that's why it's meanginless to talk about what happens "before", "after" or "simultaneously" in vastly separated regions of the Cosmos. It all depends on your frame of reference, which in turn depends on how fast you yourself are travelling. An observer at B could receive a signal from A, even though in his frame of reference the A doesn't even exist yet (or is 10,000 years behind) thus creating a paradox.

Answer 7

Read the book "Faster Than Light - Superluminal Loopholes In Physics" by Nick Herbert.......Very illuminating! Also, study "Bell's Theorem": John Stewart Bell stated and proved that a superluminal connection exists in nature, between any two phase-entangled systems. However, actual signalling or communications, except via the Tachyonic Antitelephone, have not yet been achieved by us mortals.

Answer 8

It is possible, in a certain sense. But first, what do you mean by "instantly"? That is, what does A observe? What does B observe? I will allow A and B to look at clocks and measuring sticks close to them. I will even allow that A and B are not moving relative to each other, and that they have synchronized their clocks (Einstein synchronization).

Even in quantum mechanics (QM), the so-called "instant signal" (quantum entanglement) can not be used to pass any information faster than light. Relativity does NOT say that nothing can travel faster than light in vacuum. It does say that nothing material, or carrying information, can travel faster than light. Even in QM, this is still true.

Answer 9

Because it would take 10,000 years for even the fastest moving thing ever, (light) to reach person B.... so by the time person B got the signal he/she would be dead

Answer 10

While nothing can travel faster than light, there are some theories in physics that could potentially allow for this type behavior.

One is a wormhole connecting these two distant points in space. The second is called "spooky action at a distance" and deals with quantum entanglement.

The later could be used to manupulate remote particles from that distance possibly allowing for this type of communications