# The Naked Scientists Forum

### Author Topic: How "fast" does force "travel"  (Read 12435 times)

#### imatfaal

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##### Re: How "fast" does force "travel"
« Reply #25 on: 28/06/2012 17:58:29 »
Letoll - not sure about that at all.  There is no transfer of information (and a force would imply that) which travels faster than c.  Entanglement is a lovely sci-fi buzz word (and a highly serious physics subject) - but it most certainly does not allow greater than c communication of any information.

#### Phractality

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##### Re: How "fast" does force "travel"
« Reply #26 on: 29/06/2012 00:55:29 »
Letoll - not sure about that at all.  There is no transfer of information (and a force would imply that) which travels faster than c.  Entanglement is a lovely sci-fi buzz word (and a highly serious physics subject) - but it most certainly does not allow greater than c communication of any information.
It's not that info isn't transferred FTL; but a second message must follow at the speed of light before the information can be extracted. So entanglement cannot communicate FTL.
However, if it can be verified after a SOL delay that the info was transferred instantaneously, that would prove that there is a preferred reference frame. Special relativity proves that nothing can be simultaneous at different location in all reference frames. A good candidate for the preferred reference frame is the CMB, relative to which our solar system is moving toward Virgo at about 627 km/s (different sources give different speeds). The SR formula for time as a function of position in the direction of motion is
t' = γ(t-vx/c2)
So clocks synchronized in Earth's frame have different times in the CMB frame at the rate of 9 ns/km. Earth clocks closer to Virgo show later times. A transfer of information across 10 km in the direction of Virgo, which is instantaneous in the CMB frame, would arrive 90 ns before it is sent according to Earth clocks. This does not violate causality because info sent back to the starting point would be delay by the same amount. If this method could be used for instantaneous communication (which it probably can't), the 2-way communication would be instantaneous, but you could not send a message into your own past.

#### kowalskil

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##### Re: How "fast" does force "travel"
« Reply #27 on: 01/07/2012 13:38:20 »
is the transmission of force instantaneous? if yes does this mean information travels faster than light?

if I have a long stick, say 10 light years long, OK so its a really long stick. If I push on the near end of the stick, how long until the force can be measured at the far end of the stick? does it take 10 years?
I would have thought it would go much slower than the speed of light - the speed of sound would be what I would expect in that particular instance.

Me too.

#### Robro

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##### Re: How "fast" does force "travel"
« Reply #28 on: 06/07/2012 03:07:20 »
I think force propagates at the speed of light, although, as force travels through various mediums there is a loss in efficiency due to reaction times in molecules and atoms. Use the force Luke.

#### The Naked Scientists Forum

##### Re: How "fast" does force "travel"
« Reply #28 on: 06/07/2012 03:07:20 »