Faster than light -- can it be? Watch

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BCHL85
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#1
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As my teacher has just taught m = mo/rt(1-v^2/c^2), so if something can travel with speed of light, its mass is infinite --> nothing is faster than light.
But I heard ...there was something invented that faster than light, so I look up Google and find a news in BBC.
http://news.bbc.co.uk/1/hi/sci/tech/781199.stm
Do you think it's true or not?
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aiman
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I have read alot of articles about this as I have been quite intrested in this topic as well.
There have been many experiments where the theoratical speed of light(299792458 m/s) has been broken.
An experiment was done where the speed light was broken by a factor of 300.
The articles abouth this experiment are avalilable on these links:
http://news.bbc.co.uk/1/hi/sci/tech/841690.stm
http://www.space.com/scienceastronom..._c_000719.html
http://partners.nytimes.com/library/...ics-light.html

Yet many physists are not yet convinced thta these experiments prove anything(read aricles for more info on this).
But having read about at least 10 experiments where speed of light has been broken I am inclined to believe its true.
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eurasianfeline
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i can't remember where i heard this before...but there have been hypothesis that the speed of light when the universe just began after the big bang is much faster than the speed of light now.
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elpaw
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barticles called tachyons have been theorised to travel faster than light, but they cannot travel slower than light. (i.e. they cannot cross the light barrier - same as "normal" particles)
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VCVT17
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I read the book of Stephen Hawking, and it said that some of elementary particles can travel through the space by jumping in the high level energy. It might not be proved. However, It seems to make me think a lots the way it happens.
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Erased Citizen
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Read the book by Joao Magueijo - who was the guy who put forward the idea. Its very informative about the subject, and a good read too.
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jpowell
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All that is happening in this case is a wave is travelling faster than the speed of light. But it cannot transfer any useful information.

Imagine you are inside a cylinder that is a light year in radius, and you are at the centre.

Now you shine a laser pointer towards the cylinder wall and then turn around 180 degrees.

Now one year later the light will reach the cylinder, and anyone who watches the laser dot will see it appear to move faster than the speed of light. This doesn't break any laws of physics because the "dot" isn't a real thing, it is just a source of light.

Likewise the thing they measured to travel faster than the speed of light in that mentioned experiment wasn't a real "thing" they measured something similar to a laser dot, or a shadow, i.e. not something in itself, but the result of another thing.
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danguetta
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Slightly unrelated (but still interesting) is the following question, which I was asked at my interview at Manchester:

"We have a source of light which shines onto an opaque plate of constant arbitrary length, at a perpendicular distance L1 from the source of light. The plate is moving with velocity v with respect to the light bulb and the floor. The shadow of the plate is projected onto the floor, at a perpendicular distance L2 from the plate. The plate and floor are parallel to each other. Is it possible for the shadow to move faster than the speed of light?"

(Assuming no matter can travel faster than the speed of light, of course )

Rather tricky, don't you think !?


Daniel
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jpowell
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A shadow isn't matter. So it could indeed travel faster than the speed of light.
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danguetta
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(Original post by AntiMagicMan)
A shadow isn't matter. So it could indeed travel faster than the speed of light.
Aha - but think about it...

You're assuming shadows move instantly as the object moves. But at very high speeds (if v approaches the speed of light) this need not be the case, because shadows are caused by the movement of light, and by the time the light gets from the plate to the floor, the plate will have moved on !

Rather spiky, isn't it !!

Daniel
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jpowell
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No I am not. Eventually the effect will propagate to the wall, and then you will see the shadow move faster than light. Of course nothing is actually moving faster than light.

http://math.ucr.edu/home/baez/physic...ght/FTL.html#3 See this for more info. And information on other "trivial" cases of things moving faster than light.
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