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Speed-of-light experiments yield baffling result at LHC

bbc.co.uk

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Re: Speed-of-light experiments yield baffling result at LHC

#31

Post by adrianN »

Terretta wrote: post #18
coffeenut wrote: post #5

If I calculated correctly, that's only about .0025% faster than c. Practical implications?

> Practical implications? Using ion propulsion and gravitationally assisted slingshot trajectories, you'd get to Proxima Centauri about 173 days 12 hours sooner, which sounds pretty cool if you ignore that that's 173 days of a 19,000 year trip. By nuclear pulse propulsion (EDIT: invented, but still theoretical, thanks adrianN) taking 85 years, you'd get there about 18 hours sooner.

Nuclear pulse propulsion is actually invented, we just didn't build it yet.

Re: Speed-of-light experiments yield baffling result at LHC

#32

Post by ajuc »

dholowiski wrote: post #15
coffeenut wrote: post #5

If I calculated correctly, that's only about .0025% faster than c. Practical implications?

I'm not smart enough to explain it properly, but basically if information can be transmitted faster than the speed of light, it makes time travel possible. Read "Black Holes and Time Warps" By Kip S. Thorne for a 624 page explanation of why. More likely, it's experimental error. .0025% is meaningless compared to the scale of the earth, but over hundreds of light years it's huge.

http://en.wikipedia.org/wiki/Time_travel#Via_faster-than-lig...

If we can send information even a little to the past, we can then send it a little more to the past, and by induction we can send information anywhere in time.

So we have infinite power computers. Singularity starts here.

Re: Speed-of-light experiments yield baffling result at LHC

#34

Post by Confusion »

jxcole wrote: post #19
DenisM wrote: post #12

There was an experiment where an impulse of light came out the other end of a material faster than light could have traveled through vacuum in the same space. The eventual explanation was as follows - imagine that your outgoing bunch of photons looks like this: :::... The first three photons are "invisible" because there is so few of them that they are below the equipment sensitivity. The second group of six particle…

That is such a well known result in physics that the likelihood of it occurring here is almost zero. I remember first reading about it and the scientists basically said "we broke the speed of light" without looking for further explanations. These guys seem like they generally don't believe that they have broken the light barrier, but they need help figuring out what they actually did do from the broader community. Du…

What DenisM is describing is not the result of a systemic error. It is not an error at all. 'Something' is travelling faster than light in that experiment. The problem is that the 'something' isn't a physical object.

The common example is the beam of a lighthouse. Suppose a lighthouse revolves once per minute. At one lightyear distance from the lighthouse, the angular velocity of the beam is 2*Pi lightyears per minute, which is much faster than the speed of light. However, this is not a problem: the beam is not a physical entity. There is no single particle actually travelling faster than the speed of light. It's just some construct in our minds to which we assign that velocity.

Something similar is happening in the experiment described by your parent and possibly in the experiment in the linked article.

Re: Speed-of-light experiments yield baffling result at LHC

#35

Post by [deleted] »

felipemnoa wrote: post #29
dholowiski wrote: post #16

Earlier quoted context omitted.

Don't forget... c is the speed of light 'in a vacuum'. Light travels slower through gas, water or glass. Light has even been slowed down to walking speed in a laboratory. The speed of light is not constant. The speed of light in a vacuum is. We assume.

>>The speed of light is not constant I think this is wrong. Regardless of the medium the speed of light is always constant. It seems to slow down because the photons are getting absorbed and re-transmited by atoms. But the speed of light is always the same regardless.

[deleted]

Re: Speed-of-light experiments yield baffling result at LHC

#36

Post by sp332 »

tsycho wrote: post #33

"...the researchers noticed that the particles showed up a few billionths of a second sooner..." I am impressed that their measuring instruments have a precision that is (statistically significant-ly) smaller than a billionth of a second.

How do you think gigabit ethernet works?

Re: Speed-of-light experiments yield baffling result at LHC

#37

Post by jxcole »

gaika wrote: post #2

It wouldn't break current theory, it would just mean that photons travel slower than "speed of light" and have non-zero rest mass. Constant c in relativity instead of speed of photons would just mean fastest speed possible.

I have a comment about this. C, as is used in general relativity, is involved in a lot more than just the speed that light travels. It is also relevant to a lot of other equations, like time dilation in a gravitational field. Now, if this experiment resulted in changing our concept of c as the "speed of light" to the "speed of neutrinos", then your probably right. But I have to imagine that c has been verified experimentally in non-light related experiments.

For example, there is a certain speed where if you exceed it you are able to violate causal time relationships. I can't think of any experiments that would validate this. However, there is also the fact that theoretically, if you attempt to accelerate matter to the speed of light it's mass will increase infinitely. So if you accelerate it a little bit it's mass should increase a little bit, and you should be able to confirm the speed of light through an experiment where you measure infinitesimal increases in mass during large acceleration.

So my comment is that if he just broke the speed at which light travels, then everything is fine. But if he broke the speed at which you are able to violate causality, or the speed at which the mass of an object is infinite, then our entire understanding of physics is likely to be invalid.

Related reading - tachyon pistols

http://sheol.org/throopw/tachyon-pistols.html

Re: Speed-of-light experiments yield baffling result at LHC

#39

Post by ErrantX »

DanielBMarkham wrote: post #3

A news article where both the scientists and the reporter understate the claims, publish the data, and ask other teams to please prove them wrong. I like this. Most of the time the reporters overstate the research, the scientists keep the data secret, and the general public is left scratching their heads.

Indeed. Compare that with the other article about this currently on the first page of HN: http://hosted.ap.org/dynamic/stories/E/EU_BREAKING_LIGHT_SPE...

Which is less cautious and more of the standard fare of not-very-well-reported science.

sigh

Re: Speed-of-light experiments yield baffling result at LHC

#40

Post by Confusion »

felipemnoa wrote: post #29
dholowiski wrote: post #16

Earlier quoted context omitted.

Don't forget... c is the speed of light 'in a vacuum'. Light travels slower through gas, water or glass. Light has even been slowed down to walking speed in a laboratory. The speed of light is not constant. The speed of light in a vacuum is. We assume.

>>The speed of light is not constant I think this is wrong. Regardless of the medium the speed of light is always constant. It seems to slow down because the photons are getting absorbed and re-transmited by atoms. But the speed of light is always the same regardless.

That's splitting hairs in a way that makes you deviate from standard usage of the term. Physicists say things like "the speed of light in water is lower than the speed of light in a vacuum".
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