4 ms·

I sent this to my friend who has a phd in physics and is a post-doc at Cambridge and he said it's bogus.

by digz 14y ago

ChrisClark 14y ago
Then he didn't understand what you were asking. It can easily be faster than the speed of light because no information can be transmitted through this phenomenon.
- dasil003 14y ago
  Whoah you're jumping to a strange conclusion here. How do you know he didn't actually look at the paper and respond based on the contents rather than first thing that happened to pop into your mind?
- n3rdy 14y ago
  > Then he didn't understand what you were asking. It can easily be faster than the speed of light because no information can be transmitted through this phenomenon. If its observable then how could information not be transmitted? I'm the furthest thing from a physicist but if quantum entanglement causes an atoms polarity to change because millions of miles away another atom it is entangled with did the same, that would seem like an excellent way to encode information into bits, supposing you can change the atoms polarity at a whim.
  - gambiting 14y ago
    Because just observing the polarity changes it, so you can never be sure what position it was in originally. So you can affect an object that is light years away from you instantly, but it's useless for transmitting information, because while you know which state it is in, the party on the other end does not,and has no way of finding out without affecting the information and making it useless.
    - n3rdy 14y ago
      > Because just observing the polarity changes it, so you can never be sure what position it was in originally. That does put a crimp in my universal router plans, but that's really interesting by itself that just looking at the atom affects its polarity.
      - gambiting 14y ago
        Well it does not _really_ change the polarity. Think about it this way: You have two cards(A and B) - you and your friend pick one randomly. Until you look at yours, it's both A and B at the same time. It's the same with your friend's card. So you both own cards that are in a "mixed" A/B state. And then, when you and your friend look at them, the state is "decided". Therefore, you could send your friend and his card on a rocket million years away from Earth, and then look at the card. Then,you can tell with 100% guarantee which card your friend has. Is that information useful? No,not really. You were able to instantaneously find out the state of an object millions of light years away,but you can't use it to communicate.
  - tedsanders 14y ago
    It's like you and a friend have a deck of cards. You each take a card from the deck, and then travel a million miles away. Then, at the crack of noon (synchronized to GST, of course), you both look at your cards. Your card is the 3 of Clubs. You travel back to meet your friend, and discover that his card (which he measured at noon, just like you) was the 7 of Diamonds. You repeat this experiment a gazillion times and are amazed!! No matter how many times you run it, you and your friend never get the same card!!! It's as if the cards are sending spooky signals to each other. And after you double check that you and your friend are both looking only at 1200 GST, you realize that this spooky signal travels faster than the speed of light (since the it takes no time to "travel" a million miles). It's like magic, eh? Not really. The fact there is one of each card means it's impossible for you and your friend to have the same card. No magical spooky signals are being sent. (I think the quantum mechanical case is analogous to this contrived example. The difference in real quantum mechanics it that you really don't know what card you have until you look at it. However, that doesn't mean that your card is sending a faster-than-light spooky signal to tell the other card what to be. And you certainly can't use it for signalling or anything useful.) ((Reposted to main thread with some slight edits, in case people find this comment useful or interesting.))
    - XorNot 14y ago
      Still implying hidden local variables - i.e. "the card was always the 3 of clubs". Thusfar that isn't the case - so it does seem to be spooky action at a distance. It's not just an inability to perform a suitable measurement beforehand.
  - DanBC 14y ago
    I have a box. Inside the box my cat is alive and dead until I open the box. I open my box. Now my cat is either alive or dead. The cat in the box a billion miles away is instantly !alive or !dead. But! Cat_A being alive is paired with Cat_B being dead. We know this. When we discover Cat_A being alive and thus Cat_B being dead we're not really finding out anything about Cat_B; we're just finding out something about the Cat_A / Cat_B pairing, and Cat_A is local to us. (http://everything2.com/title/Quantum+entanglement+and+faster+than+light+communication http://everything2.com/title/Quantum+entanglement+and+faster...) Also, you can't change the polarity at a whim.
- tedsanders 14y ago
  If no information or energy is transmitted, then what exactly is traveling faster than the speed of light? Nothing. It's just as if you and a distant friend pre-agree to lift a flag at 1200 GST. The "flag-raising interaction" is instant, "travelling" faster than the speed of light, but really nothing is travelling faster than the speed of light. You and your friend just pre-agreed to do something at the same time in different locations.
  - Cushman 14y ago
    Things can travel faster than light. Say you sweep a spotlight across the moon. You could easily observe a spot of light traveling from one side of the moon to the other much faster than the speed of light. The spot of light is a "thing" the way we describe it; look at it, it's moving. But it can't be used to send information from one side of the moon to the other, so it's not a "thing" the way the universe describes it.
- mratzloff 14y ago
  My understanding is there are scientists working on quantum entanglement communication. If so, I'm not sure why you assert no information transfer. (Not a physicist.)
  - DanBC 14y ago
    Isn't that just tamper-proofing, rather than FTL communication? (http://www.newscientist.com/article/dn12786-quantum-cryptography-to-protect-swiss-election.html http://www.newscientist.com/article/dn12786-quantum-cryptogr...)
    - tedsanders 14y ago
      Right. Entanglement doesn't send information. It just protects it by giving you a private one-time pad to use for cryptography.

I sent this to my friend who has a phd in physics and is a post-doc at Cambridge and he said it's bogus.

by digz 14y ago

I sent this to my friend who has a phd in physics and is a post-doc at Cambridge and he said it's bogus.

Then he didn't understand what you were asking. It can easily be faster than the speed of light because no information can be transmitted through this phenomenon.

dasil003 14y ago
Whoah you're jumping to a strange conclusion here. How do you know he didn't actually look at the paper and respond based on the contents rather than first thing that happened to pop into your mind?
n3rdy 14y ago
> Then he didn't understand what you were asking. It can easily be faster than the speed of light because no information can be transmitted through this phenomenon. If its observable then how could information not be transmitted? I'm the furthest thing from a physicist but if quantum entanglement causes an atoms polarity to change because millions of miles away another atom it is entangled with did the same, that would seem like an excellent way to encode information into bits, supposing you can change the atoms polarity at a whim.
- gambiting 14y ago
  Because just observing the polarity changes it, so you can never be sure what position it was in originally. So you can affect an object that is light years away from you instantly, but it's useless for transmitting information, because while you know which state it is in, the party on the other end does not,and has no way of finding out without affecting the information and making it useless.
  - n3rdy 14y ago
    > Because just observing the polarity changes it, so you can never be sure what position it was in originally. That does put a crimp in my universal router plans, but that's really interesting by itself that just looking at the atom affects its polarity.
    - gambiting 14y ago
      Well it does not _really_ change the polarity. Think about it this way: You have two cards(A and B) - you and your friend pick one randomly. Until you look at yours, it's both A and B at the same time. It's the same with your friend's card. So you both own cards that are in a "mixed" A/B state. And then, when you and your friend look at them, the state is "decided". Therefore, you could send your friend and his card on a rocket million years away from Earth, and then look at the card. Then,you can tell with 100% guarantee which card your friend has. Is that information useful? No,not really. You were able to instantaneously find out the state of an object millions of light years away,but you can't use it to communicate.
- tedsanders 14y ago
  It's like you and a friend have a deck of cards. You each take a card from the deck, and then travel a million miles away. Then, at the crack of noon (synchronized to GST, of course), you both look at your cards. Your card is the 3 of Clubs. You travel back to meet your friend, and discover that his card (which he measured at noon, just like you) was the 7 of Diamonds. You repeat this experiment a gazillion times and are amazed!! No matter how many times you run it, you and your friend never get the same card!!! It's as if the cards are sending spooky signals to each other. And after you double check that you and your friend are both looking only at 1200 GST, you realize that this spooky signal travels faster than the speed of light (since the it takes no time to "travel" a million miles). It's like magic, eh? Not really. The fact there is one of each card means it's impossible for you and your friend to have the same card. No magical spooky signals are being sent. (I think the quantum mechanical case is analogous to this contrived example. The difference in real quantum mechanics it that you really don't know what card you have until you look at it. However, that doesn't mean that your card is sending a faster-than-light spooky signal to tell the other card what to be. And you certainly can't use it for signalling or anything useful.) ((Reposted to main thread with some slight edits, in case people find this comment useful or interesting.))
  - XorNot 14y ago
    Still implying hidden local variables - i.e. "the card was always the 3 of clubs". Thusfar that isn't the case - so it does seem to be spooky action at a distance. It's not just an inability to perform a suitable measurement beforehand.
- DanBC 14y ago
  I have a box. Inside the box my cat is alive and dead until I open the box. I open my box. Now my cat is either alive or dead. The cat in the box a billion miles away is instantly !alive or !dead. But! Cat_A being alive is paired with Cat_B being dead. We know this. When we discover Cat_A being alive and thus Cat_B being dead we're not really finding out anything about Cat_B; we're just finding out something about the Cat_A / Cat_B pairing, and Cat_A is local to us. (http://everything2.com/title/Quantum+entanglement+and+faster+than+light+communication http://everything2.com/title/Quantum+entanglement+and+faster...) Also, you can't change the polarity at a whim.
tedsanders 14y ago
If no information or energy is transmitted, then what exactly is traveling faster than the speed of light? Nothing. It's just as if you and a distant friend pre-agree to lift a flag at 1200 GST. The "flag-raising interaction" is instant, "travelling" faster than the speed of light, but really nothing is travelling faster than the speed of light. You and your friend just pre-agreed to do something at the same time in different locations.
- Cushman 14y ago
  Things can travel faster than light. Say you sweep a spotlight across the moon. You could easily observe a spot of light traveling from one side of the moon to the other much faster than the speed of light. The spot of light is a "thing" the way we describe it; look at it, it's moving. But it can't be used to send information from one side of the moon to the other, so it's not a "thing" the way the universe describes it.
mratzloff 14y ago
My understanding is there are scientists working on quantum entanglement communication. If so, I'm not sure why you assert no information transfer. (Not a physicist.)
- DanBC 14y ago
  Isn't that just tamper-proofing, rather than FTL communication? (http://www.newscientist.com/article/dn12786-quantum-cryptography-to-protect-swiss-election.html http://www.newscientist.com/article/dn12786-quantum-cryptogr...)
  - tedsanders 14y ago
    Right. Entanglement doesn't send information. It just protects it by giving you a private one-time pad to use for cryptography.