BABlogee Doris Bailey sent me a link to an article about a physicist who is trying to send signals backward in time.
Seriously!
I can’t add much to the article; it’s written well enough that you’ll figure out what it’s saying. But man, it’s weird stuff. I’ll be interested to see how his experiment turns out. Of course, if it works, he should be able to tell himself it worked by sending a message back to when he first started his experiment. So if it works, we’ll know sooner than we think!
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Phil Plait, the creator of Bad Astronomy, is an astronomer, lecturer, and author. After ten years working on Hubble Space Telescope and six more working on astronomy education, he struck out on his own as a writer. He has written two books, dozens of magazine articles, and 12 bazillion blog articles. He is a skeptic, and fights misuses of science as well as praising the wonder of real science.
Contact me: The Bad Astronomer "at" gmail "dot" com
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November 15th, 2006 at 5:40 pm
So does that mean that since he didn’t announce before starting the experiment that he’d got a message that it works, it doesn’t?
jbs
November 15th, 2006 at 6:32 pm
I think it’s a perfectly legitimate experiment, but I also think it’s the sort of experiment I’d rather have completely finished before going public.
November 15th, 2006 at 6:37 pm
Yeah, Phil! He wouldn’t even need to run the experiment because if it worked, he would know already! (A connundrum, because he couldn’t succeed if he never ran the experiment!)
Unless, of course, you adhere to the idea that there are an infinite number of realities, each peeling off from another every time there is a decision made. In that case, the reality line that we are in would think the experiment failed, but another would know it didn’t. What I mean is that, if he is successful, what he would really do is peal off another reality where he succeeded, but we (and he) would never know it.
I have a headache!
November 15th, 2006 at 6:42 pm
Is this one of those “chicken and egg” things?
Or better yet, choose one of the following:
Deja Vu: that feeling like you’ve been there before
Vuja De: that feeling like you should have never been ther in the first place
Clear skies
November 15th, 2006 at 6:51 pm
ooo freak show. what if he receives a message “i did it!!” so he decides “eh.. been there done that” and just gives up . time paradox!
November 15th, 2006 at 6:51 pm
No– the egg came first. We know that.
November 15th, 2006 at 7:49 pm
So if I’ve got it right, the longer the fiber optic cable used to “trap” the second photon, the farther back in time you can send a message.
Hmmm…
I just got a phone call from someone sounding suspiciously like me who told me to invest in companies that make fiber optic cable.
November 15th, 2006 at 8:31 pm
“The Bad Astronomer
Says:
November 15th, 2006 at 6:51 pm
No– the egg came first. We know that.”
That SHOULD be commen knowlege, doesn’t anyone ever read Do Fish Drink Water? anymore?!?
Back on topic now, that sounds cool, it reminds me when scientists made water run uphill. If it does work that would be the coolist thing EVAR!!!
November 15th, 2006 at 8:53 pm
One of the consequences of relativity was the concept of the temporal worm hole, one in which one end was traveling at a velocity approaching C, the other fixed. It was reasoned that a space craft entering one end could theoreticall move BOTH forward and backward in time. Furthur analysis indicated the wormhole would likely collapse the moment a material body entered it, destroying the craft and destabilizing the wormhole. Some scientists thought that some kind of exotic matter might be able to keep the wormhole stable, but it was all supposition however, the very equations that implied the wormholes existence also imply that the past MUST continue to exist, in some sense/form, in order to maintain the integrity of the relativistic theory. So maby INFORMATION can travel both ways,,,
It would be cool if he succeeds and after all, relativity HAS been right about everything else it predicted,,,
Gary 7
PS
There’s really no paradox here, as the delayed entangled photon doesn’t even exist UNTIL the experiment is initiated, so the “later” photon can’t be “undone”.
November 15th, 2006 at 10:43 pm
Message received: “Save the cheerleader, save the world.”
- Hiro!
November 15th, 2006 at 10:53 pm
I’m imagining a cartoon here… scientist at telegraph gets a message from the future “it didn’t work”.
An interesting experiment, science ususally progresses on experimental success, but experimental failure can sometimes be useful as we..
November 15th, 2006 at 10:55 pm
Taken from the article:
Ugh, this has to be one of the most common misperceptions of quantum mechanics made by scientists. Entanglement isn’t that powerful; it applies to the collapse of a wavefunction only. What this means is that if two particles are entangled, and you simultaneously measure them without perturbing them beforehand, you’ll get correlated results. If you do perturb one, nothing happens to the other particle.
Granted, what actually goes on is still a bit wierd. You have a single wavefunction for both particles, split up into two possibly distant locations in space. If you measure it at one of the particles, you cause it to collapse into a single eigenstate. Since the other particle shares the wavefunction with this one, it will also collapse into its correlated state. Is it a signal going between them? Personally, I don’t think it is. Seems to me it’s more like the universe exerting logical inference over a distance (it must do this to some extent; otherwise conservation of energy would be at risk).
November 16th, 2006 at 1:19 am
When I first got an email account in 1990, my very first message was from futureself@timgsfuture.com. The message was simply:
MSFT WMT DELL
What the heck does that mean?
November 16th, 2006 at 2:42 am
If this worked, wouldn’t it allow one to build an infinitely faster computer?
Remote rover piloting (as mentioned in the article) seems like small potatoes comparted to that.
November 16th, 2006 at 4:59 am
“Deja Vu: that feeling like you’ve been there before
Vuja De: that feeling like you should have never been ther in the first place”
Paranoia (1): Feeling that somebody is following you.
Narapoia (1): Feeling that you are following somebody.
Paranoia (2): Feeling that somebody is out to do you harm.
Narapoia (2): Feeling that somebody is out to do you good.
November 16th, 2006 at 5:02 am
Has no one noticed this little leap of implications here:
“If it does work, you could receive the signal 50 microseconds before you send it.”
Uh, huh … what? Wait a minute. What is that supposed to mean?
Roughly put, Cramer is talking about the subatomic equivalent of arriving at the train station before you’ve left home, of winning the lottery before you’ve bought the ticket, of graduating from high school before you’ve been born — or something like that.
Since when does it take less than 50 microseconds to reach a train station from home, buy a lottery ticket or go from the womb to your high school graduation?
The words, ’subatomic equivalent’ are quite buried in that description.
There was another experiment where data in the form of photons traveled faster than light through a solid object (don’t quote me on the details this is one of the ‘little about a lot’ areas of my knowledge base). Later I understand critics of the conclusion claimed it had to do with the front of the wave reaching the destination sooner than the back of the wave rather than something traveling faster than light. I haven’t heard much more about that experiment since then.
There seems to be something in this newest experiment related to the one above. Regardless, I find these quantum discoveries very exciting. Science loves mysteries.
November 16th, 2006 at 5:02 am
“No– the egg came first. We know that.”
Wrong!
The rooster came first!
November 16th, 2006 at 9:04 am
Kaptain K: You must be a fan of Robin Williams,,,
Reminds me of the question,” If a prostitute and a nun switched places, who would have the most fun?,,,,
Answer:The pope
I hope the experiment works. It would validate the concept, “,,,and then, everything happened all at once, but it took us forever to see it,,,”
Gary 7
November 16th, 2006 at 9:28 am
Umm… if this experiment worked, wouldn’t he already know, having already received his signal?
Or is he still working on the receiver?
November 16th, 2006 at 10:01 am
He will only know 50 milliseconds before he triggers the reading of the second photon. So unless he’s 50 milliseconds from triggering the reading of the second photon, he has not received his signal yet.
skeptigirl said:
>The words, ’subatomic equivalent’ are quite buried in that description.
I had the same complaint. There’s something fishy going on when people are leaping from “I can possible get a reading that corresponds to a decision I make 50 milliseconds later” to sending messages back in time. Yes, the principle becomes established, but there’s still a huge leap to go to practical application. And the mechanism relies on miles of fiberoptic cable to delay one photon. Seems a challenge to use that effectively.
We may get some interesting and perplexing info from the experiment, but it’s a far cry from time travel or time communication.
November 16th, 2006 at 10:41 am
Ahhh, but if he is successful, he proves that time travel is possible. Then is it just a matter of working out the details (admittedly HUGE details) to go from milliseconds to hours or days or years!
November 16th, 2006 at 10:45 am
Okay, I’ve just read through the explanation, and it seems to me that there’s a big point they’re missing, even using their own bad physics. They claim that when the second photon is detected, it will resolve as a particle or as a wave, and this will cause the first photon to resolve the same way. Only the problem is that the first particle is detected first, and this detection also causes it to resolve into a particle or wave, which will then effect the second particle 50 milliseconds before it hits its own detector. No time travel is necessary to send this message.
Now, even after you take that into consideration, their physics is still wrong. Simply put, the problem is that photons always travel as waves, and then resolve as single particles when they’re measured. Detecting the first particle would force the second to resolve somewhere, but after that it spreads out into a wave again before it hits the detector.
With that in mind, my hypothesis for this experiment is that they will simply detect both photons as waves. They may then go on to incorrectly interpret this as confirmation of their own hypothesis.
This just goes to show: Even quantum physicists don’t always understand quantum physics.
Aside: Now, if we were to take two particles and have one move at a relativistic speed, and the other at a non-relativistic speed, we might be able to see something interesting, but that’s another story.
November 16th, 2006 at 11:54 am
Hmmm, maybe the entire experiment is one suggested by Steven Colbert?
April fools,,,just a bit early, eh???
Oh, wait, didn’t someone just say that,,,,
Ack,,,Deja, vuja,,
I think Bill the Cat just bit me. But then, I may have already said that?
Heck, I’m going back to bed,,,
GAry 7
November 16th, 2006 at 1:32 pm
“So if it works, we’ll know sooner than we think!”
ouch, my head hurts….
November 16th, 2006 at 2:59 pm
Infophile I have a stupid question for you. You said that
[i]Now, even after you take that into consideration, their physics is still wrong. Simply put, the problem is that photons always travel as waves, and then resolve as single particles when they’re measured. Detecting the first particle would force the second to resolve somewhere, but after that it spreads out into a wave again before it hits the detector.[/i]
Well, how do scientists know photons travel as waves when every time they take a measurement they see a particle?
November 16th, 2006 at 3:02 pm
Infophile Says: “This just goes to show: Even quantum physicists don’t always understand quantum physics.”
Maybe they need one of Chief Quinn’s “Quantum Mechanics” (they guys with the really tiny wrenches…).
For the reference impaired: That’s from “Forbidden Planet”, the 50th anniversary restoration DVD of which was released this week. They did a great job, you should check it out.
- Jack
November 16th, 2006 at 3:28 pm
avataru says: “Well, how do scientists know photons travel as waves when every time they take a measurement they see a particle?”
Because photons exhibit wave interference just as sound waves or ripples on a pond. http://en.wikipedia.org/wiki/Double-slit_experiment
November 16th, 2006 at 3:31 pm
Avataru said: “Well, how do scientists know photons travel as waves when every time they take a measurement they see a particle?”
Because photons exhibit wave interference just as sound waves or ripples on a pond. http://en.wikipedia.org/wiki/Double-slit_experiment
November 16th, 2006 at 3:31 pm
Avataru said: “Well, how do scientists know photons travel as waves when every time they take a measurement they see a particle?”
Because photons exhibit wave interference just as sound waves or ripples on a pond. Search Double-slit experiment on Wikipedia.
November 16th, 2006 at 4:30 pm
Tim G said:
“MSFT WMT DELL – What the heck does that mean?”
It means you’re late!!
Jack Hagerty: regarding “Forbidden Planet” – Just got my 50th Anniversary DVD today. I’ve seen the movie many times, of course – I’ll have to keep my ears open for the tiny wrenches.
jbs
November 16th, 2006 at 6:38 pm
What Justin said (thrice). Also there’s the fact that photons diffract when they pass through a small slit. Additionally, in most quantum mechanical interpretations, any particle acts as a wave when moving, and many molecules too (up to Bucky Balls have shown wave-nature).
November 16th, 2006 at 6:47 pm
Please forgive a possibly ignorant question, but given that every other law of physics seems to break down at the quantum level, couldn’t the linear passage of time also appear to break down? I mean, It may sound wierd (what part of quatum physics doesn), but would it be possible that the signal only *appears* to travel backwards in time? Does that make any sense whatsoever?
November 16th, 2006 at 9:06 pm
That could be, but the evidence leads us to an even more profound conclusion about the nature of time in Quantum Mechanics. In essence, the arrow of time being what it is is caused by a Quantum Mechanical effect. This is because every law of physics and every physical interaction but one is reversible in time, meaning they can give no direction. This single non-reversible phenomenon is the Quantum Mechanical collapse of a wavefunction, wherein a wave resolves into a single state.
Many scientists claim that it’s entropy that gives time its direction, but this is only partly true. The problem with this is that entropy isn’t a physical law; it’s a statistical one, and simply describes a trend. Entropy may give time its direction, but we still need something to give entropy its direction. The collapse of a wavefunction is what accomplishes this.
November 17th, 2006 at 1:11 am
Infophile: thx… I think I sorta understood that.
November 17th, 2006 at 6:43 am
Infophile: I had pretty much the same thought as you – but read the article a few more times, and finally understood that the detector for the photon that had gone through the fibre could be positioned to DETERMIONE how the particle would be detected – thereby intentionally influencing the “decision” on particle-ness or Wave-ness:
“The other photon will be sent toward … a movable detector, he said.
Adjusting the position of the detector … determines whether it is detected as a particle or a wave. ”
So – the first one detects what it is, the second one is influenced to be a P or W, thereby (in theory tested) influencing the first one.
JC
November 17th, 2006 at 6:45 am
Determione?? Sheesh – I shouldn’t type after being on pager duty all night…
November 17th, 2006 at 10:38 am
Infophile, the first photon will be sent through a double slit and hit the detector. It will register as either a particle or a wave. The second detector will be manually varied and the operator will decide to measure a detector or a wave. The decision is made on the second photon, the after the first photon has been detected either as a particle or a wave. Compare results.
>Now, even after you take that into consideration, their physics is still wrong. Simply put, the problem is that photons always travel as waves, and then resolve as single particles when they’re measured. Detecting the first particle would force the second to resolve somewhere, but after that it spreads out into a wave again before it hits the detector.
This is an interesting suggestion. Someone should email it to the researchers.
>With that in mind, my hypothesis for this experiment is that they will simply detect both photons as waves. They may then go on to incorrectly interpret this as confirmation of their own hypothesis.
They will get the first detected however it hits (50% split? I don’t know what is typical). The second will register depending upon what they look for. This will leave them perplexed, but conflict with their hypothesis.
And I don’t think avataru was unaware of interference, I think he/she was picking on your wording.
Except when they’re measured as waves (interference).
November 17th, 2006 at 11:08 am
Ah, I didn’t see that, thanks. I’ll have to see if I can find a more scientific description of their procedure, then I’ll be able to form a bit more informed of an opinion on it.
As for detecting whether the photon is a particle or wave, it’s not really a simple case of “Okay, now it’s a wave… now it’s a particle.” The meaning of wave-particle duality is that some experiments show photons exhibiting properties we expect from waves (such as diffraction and interference), while others show them exhibiting properties we’d expect from particles (such as being quantized into single photons).
When you get into a full QM picture, our old definitions of “particle” and “wave” just don’t cut it. Everything we’ve tested on this scale appears to propagate as a probability, but then resolve into a single point when “measured.”
So, with that in mind, here’s basically how the double-slit detector works. A photon is fired out of some source, and its propagation wave can pass through one of two slits. The wave then propagates out of both slits and hits a detector screen. If the photon were acting like a particle, we would expect the resulting pattern on the screen to be the sum of the diffraction patterns from each individual slit. If it were acting like a wave, we’d expect a much stranger interference pattern.
So then we run this experiment. With many photons being shot out, we see the interference pattern form, so they act like a wave here. If we shoot out the photons one at a time, then surprisingly we also see this pattern in the probability distribution of where they hit. The result is the surprising fact that a single photon seems to propagate as a wave which gives its probability of resolving at a given point if measured.
With this in mind, I don’t why a photon would ever register as a “particle” in a detector like that. Yes, a light distribution matching that predicted for a particle would imply this, but all the evidence we’ve seen tells us that that won’t happen.
Aside: That being said, it is possible to get the “particle” distribution to appear if we alter the experiment slightly. What we have to do is force the photon to resolve its wavefunction when it’s in one of the slits. This is tricky to do with a photon, but if we switch to electrons and shine light on them, we can do this (and yes, electrons normally will show wave-like interference if we don’t do this).
November 18th, 2006 at 7:43 pm
Here is what I don’t follow on this – at least, I don’t follow the thought process involved.
Let’s assume the following:
There is a detector that determines the “type” of photon – particle or wave – as the photon passes the detector. This will be called “Detector A”. It is not “adjustable” and will report faithfully what type of photon passes.
There is a type of detector that, by manipulation, will “influence” the type of photon you detect – whether it is “read as” a particle or a wave. This will be called “Detector B”
The detector that cannot be manipulated reads a photon that has only passed through free space.
The detector that can be manipulated is reading (and influencing) the photon that has run through the fibre and is delayed by 30 ms.
Now – here is what I fail to understand about this experiment:
The photon that is detected by A is detected “first”, the photon detected by B is detected 30ms later – BUT B can influence the detected type of the photon, presumably at A.
If we know that A has detected a particle, and then (one presumes a computer does this) we then “influence” B to detect a wave, does our detection of the particle at A then change?
To me, it seems to say that A influences the detection at B, but I may just be missing the entire point. If B’s positioning is determined ahead of time, the photons are emitted and detection at A must then agree with what is seen at B. If B is set to detect a wave, then all photons at A should be seen to be waves.
However, if you detect the photon at A and then change B so that it it is opposite to what you just saw at A………
I guess I just don’t understand the experiment well enough.
JC
November 22nd, 2006 at 7:14 am
Infophile said (at 6.38pm)…
“Also there’s the fact that photons diffract when they pass through a small slit.”
I have a problem with that statement. It seems to be illogical. I understand that ‘diffraction’ is the process whereby a wave, or a wavefront is split into many parts, as it passes through a narrow slit or close to an edge. We see that effect in a rainbow display, or a prism where light is split into various colors depending upon its wavelength.
I take it that means broken into photons, but I guess that could mean many different sized bits, depending on the actual ‘roughness’ of the edge (edges) involved. Maybe even single photons. However our correspondent is implying that the diffraction (subsequently ?) also has an effect on photons, and they diffract, ie, also break down to componant parts.
And is a photon considered a ‘particle”, or are *they*
made up of particles, or vicky-virky?
Sorry, but I need a Q.M. 101 course.
Ivan.
November 23rd, 2006 at 3:18 pm
JackC, you recognize the dilemma that the scientists are studying. They don’t know what will happen. Theory isn’t clear.
icemith, from what I gather, each photon will follow the interference distribution. That is the surprising result – the wave is not made up of a lot of component photons, each photon has wave aspects and particle aspects.