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Faster than the speed of light?
Posted: 10 April 2010 12:21 PM   [ Ignore ]   [ # 211 ]
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From the wiki on faster-than-light

A 2008 quantum physics experiment also performed by Nicolas Gisin and his colleagues in Geneva, Switzerland has determined that the “speed” of the quantum non-local connection (what Einstein called spooky action at a distance) is at least 10,000 times the speed of light.

Space can expand faster than the speed of light. Here is an interesting article on the expansion of the universe by CHARLES H. LINEWEAVER and TAMARA M. DAVIS, astronomers at Mount Stromlo Observatory near Canberra, Australia.

Does this prediction of faster-than-light galaxies mean that Hubble’s law is wrong? Doesn’t Einstein’s special theory of relativity say that nothing can have a velocity exceeding that of light? This question has confused generations of students. The solution is that special relativity applies only to “normal” velocities…motion through space. The velocity in Hubble’s law is a recession velocity caused by the expansion of space, not a motion through space. It is a general relativistic effect and is not bound by the special relativistic limit. Having a recession velocity greater than the speed of light does not violate special relativity. It is still true that nothing ever overtakes a light beam.

Also, like Alice in Wonderland:

Running to Stay Still

The idea of seeing faster-than-light galaxies may sound mystical, but it is made possible by changes in the expansion rate. Imagine a light beam that is farther than the Hubble distance of 14 billion light-years and trying to travel in our direction. It is moving toward us at the speed of light with respect to its local space, but its local space is receding from us faster than the speed of light. Although the light beam is traveling toward us at the maximum speed possible, it cannot keep up with the stretching of space. It is a bit like a child trying to run the wrong way on a moving sidewalk. Photons at the Hubble distance are like the Red Queen and Alice, running as fast as they can just to stay in the same place.

And the edge of the observable universe:

What does mark the edge of observable space? Here again there has been confusion. If space were not expanding, the most distant object we could see would now be about 14 billion light-years away from us, the distance light could have traveled in the 14 billion years since the big bang. But because the universe is expanding, the space traversed by a photon expands behind it during the voyage. Consequently, the current distance to the most distant object we can see is about three times farther, or 46 billion light-years.

However:

The recent discovery that the rate of cosmic expansion is accelerating makes things even more interesting. Previously, cosmologists thought that we lived in a decelerating universe and that ever more galaxies would come into view. In an accelerating universe, however, we are surrounded by a boundary beyond which occur events we will never see…a cosmic event horizon. If light from galaxies receding faster than light is to reach us, the Hubble distance has to increase, but in an accelerating universe, it stops increasing. Distant events may send out light beams aimed in our direction, but this light is trapped beyond the Hubble distance by the acceleration of the expansion.

An accelerating universe, then, resembles a black hole in that it has an event horizon, an edge beyond which we cannot see. The current distance to our cosmic event horizon is 16 billion light-years, well within our observable range. Light emitted from galaxies that are now beyond the event horizon will never be able to reach us; the distance that currently corresponds to 16 billion light-years will expand too quickly. We will still be able to see events that took place in those galaxies before they crossed the horizon, but subsequent events will be forever beyond our view.

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Posted: 01 May 2010 11:42 PM   [ Ignore ]   [ # 212 ]
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I am a stumbler.

I know this topic is huge and I don’t feel like reading through the entire thing, and it’s been a little bit off the original topic for a couple days.

Some people are saying that this rather long pencil moves faster than light, using the proof that the pencil doesn’t have to move the entire distance. This logic is fallible in the same sense that yelling into a pipe does not mean the sound will travel faster than the normal speed of sound, because “the air molecules themselves aren’t moving along the entire length of the pipe”. Instead of the actual physical object shifting, a wave must propagate through the system and it is that function which brings the speed down to below light-speed.

Consider that the pencil is of arbitrary thickness, say one atom thick. Let’s say this one atom thick pencil is perfectly rigid, and is incapable of bending. This, one would think, would be the most perfect, simple way to transmit data above lightspeed. But it is not that simple. Each atom in the chain is composed of protons, neutrons, and electrons. The protons and the electrons primarily hold the atom together through the electrostatic force, which is carried by photons. When George pushes his end of the pencil, he pushes on the electrons on the outer shell of the first atom. The electrons push against the protons with the electrostatic force via photons, and the protons then push against the electrons on the other side. Those electrons then push against the neighbouring atom’s electrons, repeating the process. The physical movement is all done in interactions in electrostatic fields in the atoms, which each rely on photons. Photons are, in other words, the same things that make up light.

Here is a beautiful picture. Note the use of Pizza Hut font. As George writes with one end of the pencil, he is manipulating the atoms on one end of the pencil. This slightly deforms the first atom, which transmits his writing to the next atom and so on. The resulting thing is a sort of pressure wave that propagates all the way to Earth. But it cannot propagate faster than light, as the wave is carried using photons which are the main component of the electrostatic force and each photon in the chain is limited by the speed of light.

george_and_his_big_stupid_pencil.jpg


Therefore, movement of the rigid pencil and thus movement in any physical object is limited by the speed of light.

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Posted: 28 May 2011 10:39 PM   [ Ignore ]   [ # 213 ]
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I think narwhol said it without realising; exchange photons transfer the signal. And since photons travel at the speed of light…it would take over 8 minutes.

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Posted: 29 May 2011 03:42 PM   [ Ignore ]   [ # 214 ]
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I read the opening post to mean that space can expand faster than light because it expands into a “nothingness” where natural laws and restrictions have no meaning.
However, inside the expanding space (bounded something) natural laws are in effect and events are restricted to quantum operating under a quantum constant of SOL.

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Posted: 29 May 2011 07:01 PM   [ Ignore ]   [ # 215 ]
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If George’s pencil was replaced by the medium mentioned earlier, we established that FTL is possible, right?

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Posted: 29 May 2011 07:31 PM   [ Ignore ]   [ # 216 ]
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The unfolding of the universal fractal (geometric).

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Posted: 30 May 2011 06:06 AM   [ Ignore ]   [ # 217 ]
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traveler - 29 May 2011 07:01 PM

If George’s pencil was replaced by the medium mentioned earlier, we established that FTL is possible, right?

No. Nothing in this universe can move through space faster than the speed of light, not even information. Every physics experiment designed to test relativity has confirmed Einstein’s ideas, therefore we have no reason to think they are wrong. Anyone who says otherwise needs to present some very compelling evidence.

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Posted: 30 May 2011 06:48 AM   [ Ignore ]   [ # 218 ]
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DarronS - 30 May 2011 06:06 AM
traveler - 29 May 2011 07:01 PM

If George’s pencil was replaced by the medium mentioned earlier, we established that FTL is possible, right?

No. Nothing in this universe can move through space faster than the speed of light, not even information. Every physics experiment designed to test relativity has confirmed Einstein’s ideas, therefore we have no reason to think they are wrong. Anyone who says otherwise needs to present some very compelling evidence.

Right, but that’s through empty space. FTL speed is possible through a medium. Let’s face it, George’s pencil is a fantasy. All I’m saying is if that pencil was made of a medium that does allow for pulses at FTL, then he can save the world.  cheese

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Posted: 30 May 2011 06:58 AM   [ Ignore ]   [ # 219 ]
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traveler - 30 May 2011 06:48 AM

Right, but that’s through empty space. FTL speed is possible through a medium. Let’s face it, George’s pencil is a fantasy. All I’m saying is if that pencil was made of a medium that does allow for pulses at FTL, then he can save the world.  cheese

Nope. Light slows down when it passes through matter, such as water. I haven’t waded through the entire thread this morning, although I was following it when it was new, so I don’t know where you got the idea that light speeds up when it passes through a medium, but that is 180 degrees wrong.

Think of it this way. We call the maximum speed allowed through space the Speed of Light, but that is just nomenclature. The speed light travels does not define the ultimate speed limit in our universe, light just happens to travel at the maximum possible speed when in a vacuum. When light encounters any medium it slows down, much the same way a car traveling the speed limit on a highway slows down when encountering heavy traffic.

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Posted: 30 May 2011 07:14 AM   [ Ignore ]   [ # 220 ]
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DarronS - 30 May 2011 06:58 AM
traveler - 30 May 2011 06:48 AM

Right, but that’s through empty space. FTL speed is possible through a medium. Let’s face it, George’s pencil is a fantasy. All I’m saying is if that pencil was made of a medium that does allow for pulses at FTL, then he can save the world.  cheese

Nope. Light slows down when it passes through matter, such as water. I haven’t waded through the entire thread this morning, although I was following it when it was new, so I don’t know where you got the idea that light speeds up when it passes through a medium, but that is 180 degrees wrong.

Think of it this way. We call the maximum speed allowed through space the Speed of Light, but that is just nomenclature. The speed light travels does not define the ultimate speed limit in our universe, light just happens to travel at the maximum possible speed when in a vacuum. When light encounters any medium it slows down, much the same way a car traveling the speed limit on a highway slows down when encountering heavy traffic.

It is a long thread. You missed a link provided earlier (understandable, and I’ve noticed you don’t miss much smile ). Check out THIS LINK.

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Posted: 30 May 2011 01:09 PM   [ Ignore ]   [ # 221 ]
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After doing a bit of research on this I have found that only one group, Boyd, et al., at the University of Rochester has conducted these experiments. Even their results do not show information traveling faster than light. The Department of Physics at the University of Illinois at Urbana-Champagne has a good explanation.

George cannot save the world.

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Posted: 30 May 2011 03:38 PM   [ Ignore ]   [ # 222 ]
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That’s a good link Darron. I see its answer, but I will have to think more before I understand it. Helping George save the world is tough. Perhaps he should just save the cheerleader.

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Posted: 30 May 2011 07:39 PM   [ Ignore ]   [ # 223 ]
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What cheerleader, traveler? I never get your jokes, guys, grrr…

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Posted: 31 May 2011 04:57 AM   [ Ignore ]   [ # 224 ]
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George - 30 May 2011 07:39 PM

What cheerleader, traveler? I never get your jokes, guys, grrr…

Have no fear George. The only reason you don’t get this one is because you didn’t watch a silly (but very popular) TV show. In this case, the show was “Heroes” in which one actor was a cheerleader. “Save the cheerleader,” was key to saving the world. I respect you more for NOT knowing this one.  smile

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Posted: 22 June 2011 11:00 AM   [ Ignore ]   [ # 225 ]
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If you can send signals faster than light, you can build a device that allows you to send signals into your own past, see here:

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

(the math is straightforward)

This leads to a paradox, because if you receive a phonecall on Sunday form yourself on Monday, then you can decide not to call yourself up the next day, while if you don’t receive such a phonecall, you call yourself up the next day.

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