Physicist Trying To Send a Signal Back In Time

phil reed writes "University of Washington physicist John Cramer is attempting to send a signal back through time." From the article: "We're going to shoot an ultraviolet laser into a (special type of) crystal, and out will come two. lower-energy photons that are entangled," Cramer said. For the first phase of the experiment, to be started early next year, they will look for evidence of signaling between the entangled photons. Finding that would, by itself, represent a stunning achievement. Ultimately, the UW scientists hope to test for retrocausality — evidence of a signal sent between photons backward in time. The test will involve sending one of the photons down 10 miles of fiber optic cable, delaying it by 50 microseconds, then testing a quantum-mechanical aspect of the delayed photon. Due to quantum entanglement, the non-delayed photon would need to reflect the measurement made 50 microseconds later on the delayed photon. In order for this to happen, some kind of signal would need to be sent 50 microseconds back in time from the delayed photon to the non-delayed photon. (Confusing? Quantum physics is like that.)

Comments

any lawyers available?

[Patrik_AKA_RedX]

I have a question: Is it legal to use a timetravel device to chea^H^H^H^Haid in winning the lottery?

Isn't this axiomatically impossible?

[rubberpaw]

IANAP, but when I studied some basic quantum theory, I thought that one of the issues that arose in the EPR/Bell research was that in order for entanglement to be valid, it could not be used to transmit information, except via quantum teleportation, which has strong limitations due to being a classical information channel. Does anyone care to clarify for me?

Not the only scientist trying this

[tjl2015]

Aside from the undoubtedly numerous crackpots who are attempting to build a time machine, I know of at least one more legitimate scientist who is working on something similar. Professor Ronald Mallet, at the University of Connecticut, is working on sending particles back in time. He is basing his on General Relativity, not quantum mechanics, using a circular path of lasers:

http://en.wikipedia.org/wiki/Ronald_Malett

The importance of both of these projects is that if you can send photons back in time, you can send signals back in time, and send messages. For years people have wondered about temporal paradoxes and how they may be resolved. With a system such as these, paradoxes can be tested. We'll finally have an answer to the Grandfather paradox.

Even with paradoxes such as this, a temporal communication device would have incredible application. The scientist in the article might only be working with a few microseconds, but it sounds like that if you have a long enough fiber optic cable, you can send a signal as far back as you want. You might not be able to, say use it to prevent someone from having a fatal accident, since if the accident never happened, you would have never sent the message. But there are many useful applications, especially in forewarning events beyond human control. What if we knew exactly when and where every earthquake and hurricane was going to hit in a particular year? What if we knew rainfall patterns in advanced and could plan for draught ahead of time?

You wouldn't be able to use it to prevent the next 9/11, but you could probably use a temporal communicator to prevent the next hurricane Katrina disaster. The hurricane or earthquake will still devastate the city, but that doesn't mean there has to be anyone in it at the time.

don't be too sure

[PopeRatzo]

I heard this Cramer physicist dude on the radio the other night. He's deadly serious, and he's for real. He's also looking to get financing for building a time machine for sending tiny bits of information back in time (and he's getting a fair amount, too). You'd need a transmitter and a receiver. What would it be worth to find out that the Challenger mission was going to end badly (that was one of his examples)?

My biggest fear would be that the system works, and we start getting messages from 5 years from now 8 years from now, but ten years from now...nothing.

Re:Exciting Applications

[niktemadur]

Holy cow, the ice is getting thinner as I go along here.

Aw, what the hell, let 'er rip:

The moment we (present) invent it, they (future) will already have it, so we might be in for a barrage of information the moment we go online.

But who's to say what their agenda will be? They might be military or corporate totalitarians in disguise, leading us right into their paws. By what evidence can we trust what they tell us? Or why would we assume that it's in their best interest to warn us to change course, which might lead to their eventual non-existence?

Referring to my previous post, where I mention keeping the dialogue open to different points in the future. Could we possibly detect if time hackers are intercepting and blocking the lines, then transmiting us misinformation? Before believing in a utopian future, we must proyect past and present trends to generally visualize a future, and by these standards, how can we trust potential power-hungry bastards ten generations down the line? The future will have its' own agenda, and it might be completely opposed to our own. We might not be welcome in their future.

Here's another: what if the Karl Rove of 2005 could have a conversation with the Karl Rove of November 2006? After all, those in power will be among the first to gain access to the technology. Or maybe a Pentagon general in charge of the project will find a way to make himself into an emperor for life. Temptations will be humongous.

Now, working under the assumption that the future is relatively benevolent, somebody will have to make incredibly harsh decisions. In order to save a billion lives a hundred years down the line, who's willing to make a decision that permits the destruction of cities or nations? The death of ten or a hundred million people in the current generation? It's more than likely that the invention of a temporal communications network may diminish the worth of the individual, who becomes an abstraction that serves the species, or something more petty: an ism.

An example on a smaller scale that might hit home: What if the message we get from 2056 is: UNPLUG THE INTERNET! NOW!

Man, this is getting weirder and weirder.

How could you get messages w/o a receiver?

[Dr. Manhattan]

I don't think it's possible though, otherwise we would probably be getting messages from the future, wouldn't we?

That's like saying in 1870 that radio waves are impossible because nobody's received any. There weren't any receivers then. Or like saying neutrinos didn't exist before there were detectors for them. It's quite possible that the as soon as we have something that can receive such messages it'll be flooded with spam from the future.

Anyway, I've thought about time travel rather more than anyone probably should, if you're interested. I address that point and a lot of others.