http://www.youtube.com/watch?v=BFcKxL0z4lM Now, I'm just a layman who's read too many pop science books, so correct me if I'm wrong, but that chappie in the youtube clip seems to be suggesting that neutrinos have been measured travelling faster than the speed of light. If we can create these particles, and detect them, and they are tachyons, theoretically we should be able to construct a Dirac radio and start receiving messages from the future. I hope they start looking at ways to improve the efficiency of neutrino creating and detection so as to make these devices a practical possibility.
This was debunked last year: http://en.wikipedia.org/wiki/Faster-than-light_neutrino_anomaly There was a measurement that seemed to give a result suggesting a speed above c, but while that caused something of a stir among the press and laypeople, the scientists involved never took it for anything more than a measurement glitch, and they eventually found the causes of the error: an improperly attached cable and a miscalibrated clock.
Yep. Since it was measured in an Italian experiment at CERN, in Italy the media went apeshit about it. Politicians wrested to claim the measurement as the result of their own party's commitment to scientific research (one famously claimed they build a physical tunnel between Geneva and the Gran Sasso Laboratory in Central Italy), opinion leaders and gossip celebrities all wanted to say their 2 cents about the result, etc. The scientific community performed flawlessly, but the media circus around it was pretty awful.
Here is something that has always bothered me. I am also a lay person, so I am hoping someone can show me what I am misunderstanding. I do not see how traveling faster than light speed (or sending information faster than light speed) would mean you could receive messages from the future. Even if information were transmitted at 10 times the speed of light, nobody receives that information until after the event creating it happens. In this hypothetical they would simply receive it 10 times faster than it would take the light from the event to get there, but the event still happened in the past. I see no bridge between the past and present being created in the relativistic sense just based on sending information faster than light speed. Where am I off on this?
I'll take a stab at a layman's view of it, but someone correct me if I'm wrong: Relativistic effects change the perception of time for you as you approach the speed of light. The world around you moves slower and slower the closer you get to c. If you actually reach c, the world around you appears to stop altogether. Logically then, if you move faster than c, you should see the world moving in reverse. You'd witness the same events as you did as you approached c, but played backwards. Effectively you'd be traveling into the past. So, envisioning "you" as that message traveling faster than light, you would arrive before you left. Am I off base here? I'm just using the usual explanation of time dilation and extending it.
Special relativity includes the relativity of simultaneity: You have POV S, for which two events happen simultaneously in places 1 and 2. In a coordinate system, the line connecting these two events is the axis of simultaneity for POV S. You have POV G, for which two events happen simultaneously in places 1 and 2. In a coordinate system, the line connecting these two events is the axis of simultaneity for POV G. The axis of simultaneity of POV S and the axis of simultaneity of POV G are NOT parallel. They intersect at an angle, and then, if you are in POV S, the axis of simultaneity of POV G goes into your past (if you are in POV G, it's the other way around). I recommend you google for a coordinate system depicting this. The problem is - if you're limited to the speed of light, no matter how fast you send a signal from POV G, along the axis of simultaneity of POV G, it can't reach the past of POV S; the signal is not fast enough, it takes too long to travel along the axis of simultaneity of POV G. If you can travel FTL, though, the signal can travel fast enough along the axis of simultaneity of POV G to reach into POV S's past. If you have FTL, you can always find POVs where the FTL signal travels into the past. Most designs for time machines you might have heard of use frame dragging to make an object travel slightly faster than light. As per general relativity, they should work, too - but you must have a rotating singularity/etc at your disposal. Some are using wormholes - for them, you need negative pressure AKA antigravity, etc. But all are based on the relativity of simultaneity.
Read the tachyon pistol duel thought experiment. I would take the actual physics of it with a grain of salt (I've been told there are issues with them), but it is a good way to wrap your head around the notion. I also happen to like the train-lightning example of relativity: [yt]https://www.youtube.com/watch?v=wteiuxyqtoM[/yt] You imagine the lightnings to be non-corporeal lifeforms equipped with subspace communicators. Because they happen simultaneously, the rear lightning could reasonably tell the front lightning to miss the train, and the passenger would witness the effect happen before the cause. If there were also two conductors equipped with subspace communicators at both ends of the train, they would also witness the cause before the effect and would be able to warn the back lightning not to send the message, creating a grandfather paradox. Though that would require conductors with lightspeed reactions or a very very long train.