# Is response faster than light? **URL:** \ **Category:** Factual Questions\ **Created:** [May 13, 2000, 8:22pm UTC](https://boards.straightdope.com/t/is-response-faster-than-light/19448 "2000-05-13T20:22:48Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![GX-9900](https://avatars.discourse-cdn.com/v4/letter/g/f19dbf/32.png) [@GX-9900](https://boards.straightdope.com/u/GX-9900)\ **Post date:** [May 13, 2000, 8:22pm UTC](https://boards.straightdope.com/t/is-response-faster-than-light/19448/1 "2000-05-13T20:22:48Z")
I might have gotten the title a little confusing, but to me this question is interesting. I was thinking, what if you have a steel pole long enough to stretch it all the way up to Alpha Centauri and located there is a non-moving space station. The space station chains its end of the pole to a lever that is pointing at the opposite direction of where the rope is coming from. At the other end, the steel pole ends at Earth at another non-moving space station. At the Earth’s end, a machine or a man pulls on the steel pole and the lever is pulled on the end where the Alpha Centauri station is and is now pointing at the direction of where the pole is coming from. Now, here is my question: What is faster, the speed of light or the response in which one end of the pole is pulled to reach the other end? Also, below is a link linking to a picture I made of how this stuff might look like. If you think that it is a virus of some sort, don’t download it if you don’t want to. [Picture of what all this might look like](http://www.geocities.com/sakezero/Picture.bmp) ---
**Author:** ![JonF](https://avatars.discourse-cdn.com/v4/letter/j/cab0a1/32.png) [@JonF](https://boards.straightdope.com/u/JonF)\ **Post date:** [May 13, 2000, 9:15pm UTC](https://boards.straightdope.com/t/is-response-faster-than-light/19448/2 "2000-05-13T21:15:09Z")
Well, there are a few practical problems … The Alpha Centauri system is moving noticably relative to us, and connecting anything between something “non-moving” in our solar system to anything “non-moving” in another solar system is going to result in a broken connection pretty quickly. And then there’s the problem of defining “non-moving” … But to answer your question: physical effects propagate along material bodies no faster than the speed of sound in that material. The speed of sound in steel is around 4,500 m/sec, or about 0.0015% of the speed of light in a vacuum. So, when you pull on the end of the steel rod in our solar system, the other end of the rod will move approximately 385,000 years later. It’s not _nice_ to try to fool Motehr Nature! {grin} ---
**Author:** ![CurtC](https://avatars.discourse-cdn.com/v4/letter/c/ce73a5/32.png) [@CurtC](https://boards.straightdope.com/u/CurtC)\ **Post date:** [May 13, 2000, 9:18pm UTC](https://boards.straightdope.com/t/is-response-faster-than-light/19448/3 "2000-05-13T21:18:35Z")
Boy, this is confusing. If you boil it all down, are you really asking: if you pull on one end of a really long steel pole, will the “tug” travel down the pole faster than the speed of light? If this is what you’re asking, the answer is a resounding “no”. ---
**Author:** ![Occam](https://avatars.discourse-cdn.com/v4/letter/o/e9bcb4/32.png) [@Occam](https://boards.straightdope.com/u/Occam)\ **Post date:** [May 13, 2000, 9:23pm UTC](https://boards.straightdope.com/t/is-response-faster-than-light/19448/4 "2000-05-13T21:23:26Z")
Douglas Adams once said that nothing travels faster than the speed of light except bad news. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [May 14, 2000, 12:12am UTC](https://boards.straightdope.com/t/is-response-faster-than-light/19448/5 "2000-05-14T00:12:22Z")
I was going to say exactly what JonF just said, except that I wouldn’t have known the actual numbers. In general, the rule of thumb is that you can’t send a signal anywhere faster than the speed of light. There are some “things” that can travel faster than the speed of light, but they can’t carry information. ---
**Author:** ![Zor](https://avatars.discourse-cdn.com/v4/letter/z/848f3c/32.png) [@Zor](https://boards.straightdope.com/u/Zor)\ **Post date:** [May 14, 2000, 1:22am UTC](https://boards.straightdope.com/t/is-response-faster-than-light/19448/6 "2000-05-14T01:22:30Z")
Usenet Relativity FAQ: [Is Faster Than Light Travel or Communication Possible?](http://math.ucr.edu/home/baez/physics/FTL.html) ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [May 14, 2000, 2:45am UTC](https://boards.straightdope.com/t/is-response-faster-than-light/19448/7 "2000-05-14T02:45:21Z")
> [@](#): > > Douglas Adams once said that nothing travels faster than the speed of light except bad news. And I think someone did invent a spaceship powered by bad news, but it was so unwelcomed anywhere it went that there was no point going there. Anyway, as for the original question: when you push on a steel bar, what you are doing is compressing the steel immediately in front. This compression propagates along the bar. But this is exactly what sound is, so the “push” propagates at the speed of sound. ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [May 14, 2000, 3:33am UTC](https://boards.straightdope.com/t/is-response-faster-than-light/19448/8 "2000-05-14T03:33:19Z")
Way out of my depth here, and I only have a fuzzy recollection of what I saw on The Discovery Channel. There was an experiment in which a particle of some sort was sent in one direction, and a similar particle was sent in another. Could have been a theoretical particle. Anyway, if the particle’s charge was reversed, the other’s charge would reverse at exactly the same time. The other particle “knew” it had to change it’s charge, even though it was far away from the first. This would point to faster-than-light communication. Sorry i don’t have all of the specifics, but I saw this a couple of years ago. Does anyone know what I’m talking about? ---
**Author:** ![Alphagene](https://avatars.discourse-cdn.com/v4/letter/a/8e7dd6/32.png) [@Alphagene](https://boards.straightdope.com/u/Alphagene)\ **Post date:** [May 14, 2000, 5:13am UTC](https://boards.straightdope.com/t/is-response-faster-than-light/19448/9 "2000-05-14T05:13:22Z")
This sounds a lot like the “[Superluminal Scissors](http://math.ucr.edu/home/baez/physics/scissors.html)” thought experiment: > [@](#): > > Imagine a huge pair of scissors, with blades one light-year long. The handle is only about two feet long, creating a huge lever arm, initially open by a few degrees. Then you suddenly close the scissors. This action takes about a tenth of a second. Doesn’t the contact point where the two blades touch move down the blades _much_ faster than the speed of light? The short answer is that “no matter what material you use for the scissors, {special relativity} sets a theoretical upper limit to the rigidity of the material. In short, when you close the scissors, they bend.” Does that help? ---
**Author:** ![Philbuck](https://avatars.discourse-cdn.com/v4/letter/p/e9a140/32.png) [@Philbuck](https://boards.straightdope.com/u/Philbuck)\ **Post date:** [May 14, 2000, 5:32am UTC](https://boards.straightdope.com/t/is-response-faster-than-light/19448/10 "2000-05-14T05:32:24Z")
> [@](#): > > There was an experiment in which a particle of some sort was sent in one direction, and a similar particle was sent in another. Could have been a theoretical particle. Anyway, if the particle’s charge was reversed, the other’s charge would reverse at exactly the same time. The other particle “knew” it had to change it’s charge, even though it was far away from the first. This would point to faster-than-light communication. > > Sorry i don’t have all of the specifics, but I saw this a couple of years ago. Does anyone know what I’m talking about? Until someone more knowledgeable can explain things better, type in “quantum entanglement” in your favorite search engine. I went to a lecture on this stuff (quantum computing, actually) the other day; gave me a headache. ---
**Author:** ![John\_Kentzel-Griffin](https://avatars.discourse-cdn.com/v4/letter/j/ccd318/32.png) [@John\_Kentzel-Griffin](https://boards.straightdope.com/u/John_Kentzel-Griffin)\ **Post date:** [May 14, 2000, 6:00am UTC](https://boards.straightdope.com/t/is-response-faster-than-light/19448/11 "2000-05-14T06:00:30Z")
> [@](#): > > **Johnny L.A.** recalled from the Discovery Channel: > There was an experiment in which a particle of some sort was sent in one direction, and a similar particle was sent in another. Could have been a theoretical particle. Anyway, if the particle’s charge was reversed, the other’s charge would reverse at exactly the same time. The other particle “knew” it had to change it’s charge, even though it was far away from the first. This would point to faster-than-light communication. You are referring to Bell’s theorem or Bell’s inequality. It is not the charge, but the spin. Also you can’t change it; you detect the spin in various directions. Essentially, Bell showed that if you assume 1) QM, 2) Objective reality, and 3) Local causality, the you get a contradiction. A contradiction means one (or more) of your assumptions is false. QM has withstood all experimental tests, so it is not in doubt. Objective reality says a propertity, in particular the spin, has a definite value whether you measure it or not. Local causality says that no information can travel faster than light. The standard interpretation of the result is to deny objective reality. Even if you choose the other possibility, what actually would travel faster than light is a correlation between the particles. And you can’t know the correlation until you bring the results of the measurements together. In other words, if you assume objective reality and assume there is faster than light transmission of information, _you_ can’t use it to actually transmit information. The problem with the idea in the OP is there are no rigid rods. Every attempt at faster than light transmission of information has failed. (even thought experiments) ---
**Author:** ![JonF](https://avatars.discourse-cdn.com/v4/letter/j/cab0a1/32.png) [@JonF](https://boards.straightdope.com/u/JonF)\ **Post date:** [May 14, 2000, 2:08pm UTC](https://boards.straightdope.com/t/is-response-faster-than-light/19448/12 "2000-05-14T14:08:56Z")
**DrMatrix** ’s explanation is correct. The point as it relates to this thread is that you can’t transmit any information by exploiting this phenomenon. ---
**Author:** ![Boris\_B](https://avatars.discourse-cdn.com/v4/letter/b/fbc32d/32.png) [@Boris\_B](https://boards.straightdope.com/u/Boris_B)\ **Post date:** [May 15, 2000, 3:41am UTC](https://boards.straightdope.com/t/is-response-faster-than-light/19448/13 "2000-05-15T03:41:39Z")
[http://boards.straightdope.com/sdmb/showthread.php?threadid=8019](http://boards.straightdope.com/sdmb/showthread.php?threadid=8019) In this thread I asked about entangled states. It is much the same question as **Johnny LA** ’s from above. It looks like the consensus is that no information can travel faster than light. ---
**Author:** ![MetallicAsh](https://avatars.discourse-cdn.com/v4/letter/m/7feea3/32.png) [@MetallicAsh](https://boards.straightdope.com/u/MetallicAsh)\ **Post date:** [May 15, 2000, 4:22pm UTC](https://boards.straightdope.com/t/is-response-faster-than-light/19448/14 "2000-05-15T16:22:56Z")
Let it never be said that the government wouldn’t try to repeal the laws of nature if given the authority. The US Patent office granted a patent to application number US1997000942824 which claims: (copied from the IBM Intellectual Property Network web page) A method to transmit and receive electromagnetic waves which comprises generating opposing magnetic fields having a plane of maximum force running perpendicular to a longitudinal axis of the magnetic field; generating a heat source along an axis parallel to the longitudinal axis of the magnetic field; generating an accelerator parallel to and in close proximity to the heat source, thereby creating an input and output port; and generating a communications signal into the input and output port, thereby sending the signal at a speed faster than light. ^^^^^^^^^^^^^^^^^^^^^^^^^^ I haven’t had a chance to read the application in detail, so I wont dismiss it outright, but since I haven’t seen a Nobel awarded for this, I’m guessing the USPTO was in over its head in theoritical physics. ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [May 15, 2000, 5:55pm UTC](https://boards.straightdope.com/t/is-response-faster-than-light/19448/15 "2000-05-15T17:55:21Z")
> [@](#): > > The US Patent office granted a patent to application number US1997000942824 which claims: > […] > …, thereby sending the signal at a speed faster than light. So in 50 years, when someone realy does invent FTL communication, and tries to patent it, “Sorry, someone beat you to it. But their patent has expired, so at least you won’t be infringing.” ---
**Author:** ![JonF](https://avatars.discourse-cdn.com/v4/letter/j/cab0a1/32.png) [@JonF](https://boards.straightdope.com/u/JonF)\ **Post date:** [May 15, 2000, 7:40pm UTC](https://boards.straightdope.com/t/is-response-faster-than-light/19448/16 "2000-05-15T19:40:44Z")
> [@](#): > > In this thread I asked about entangled states. It is much the same question as Johnny LA’s from above. It looks like the consensus is that no information can travel faster than light. Actually, to throw a little fuel on the fire (and somewhat contradict my earlier statement) it appears that you _can_ transmit information, specifically a cryptographic key, over the channel between entangled photons. IBM researches have done this over a distance of 30 cm. But Mother Nature has her way in the end; the information is not usable/decodable/whatever until one end has sent and the other end has received a message that must travel by means that are restricted to the speed of light or less. Of course, you might not call this “transmitting information”. See [What is Quantum Cryprography?](http://www.iks-jena.de/mitarb/lutz/security/cryptfaq/q110.html), [Quantum Cryptography](http://www.scitec.auckland.ac.nz/~king/Preprints/book/quantcos/aq/qcrypt.htm), and [About Quantum Cryptography](http://www2.ecst.csuchico.edu/~atman/Crypto/quantum/quantum-crypto-inf.html).