How fast is the speed of dark?

eXSBass said:
Hang on, how did Arcade Fire conduct that experiment with super fast stop watch fingers? :p
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I actually got my mate to help me. First we worked out the speed of sound by him shouting at me and waving at the same time. Then I timed how long it was between me seeing the wave and hearing the shout, in order to deduce the speed of sound. I made it approximately 330 m/s.

Then I got him to say "go" exactly 1/66 seconds before he hit the 'on' button on the torch, so that me hearing him say the word would coincide with him turning the torch on.Then I timed the interval between the word and me seeing the light, and used that to calculate the speed of light. From there I was able to use the results of my previous experiment to calculate the speed of dark.

And yes, we just have really fast fingers and a really sensitive stopwatch.
 
Arcade Fire said:
I actually got my mate to help me. First we worked out the speed of sound by him shouting at me and waving at the same time. Then I timed how long it was between me seeing the wave and hearing the shout, in order to deduce the speed of sound. I made it approximately 330 m/s.

Then I got him to say "go" exactly 1/66 seconds before he hit the 'on' button on the torch, so that me hearing him say the word would coincide with him turning the torch on.Then I timed the interval between the word and me seeing the light, and used that to calculate the speed of light. From there I was able to use the results of my previous experiment to calculate the speed of dark.

And yes, we just have really fast fingers and a really sensitive stopwatch.
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So instead of going to the pub/going out with your gf you and your buddies conduct scientific experiments? :D :p (kidding)
 
Arcade Fire said:
I actually got my mate to help me. First we worked out the speed of sound by him shouting at me and waving at the same time. Then I timed how long it was between me seeing the wave and hearing the shout, in order to deduce the speed of sound. I made it approximately 330 m/s.

Then I got him to say "go" exactly 1/66 seconds before he hit the 'on' button on the torch, so that me hearing him say the word would coincide with him turning the torch on.Then I timed the interval between the word and me seeing the light, and used that to calculate the speed of light. From there I was able to use the results of my previous experiment to calculate the speed of dark.

And yes, we just have really fast fingers and a really sensitive stopwatch.
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Aha, but your method for finding the speed of sound is no adequately accurate for the purposes of this experiment, you would have to take into account the speed of light in the first place!

Seems this new fangled Science malarkey you're going on about isn't all it's cracked out to be!
 
kidkhaos said:
sorry not to take the thread off topic, but ive got a question. I always thought particles with no mass can pass through solid objects, but light cant why? :confused:
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Particles with mass can pass through materials too. Eg. Neutrinos.

Here's something to screw with your head:

In the IRF (inertial reference frame) of a photon that strikes your retina, from it's creation it is in contact with your retina. So whilest in the earth's IRF it takes 8 minutes for light to reach your eye. From the point of view of the photon, it was always there.
 
Lashout_UK said:
I'm shocked at some of the things said in this thread - Getting black by mixing coloured light? Egads! :o
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I'm shocked at the people believing that people were being serious.
 
Inquisitor said:
Aha, but your method for finding the speed of sound is no adequately accurate for the purposes of this experiment, you would have to take into account the speed of light in the first place!

Seems this new fangled Science malarkey you're going on about isn't all it's cracked out to be!
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You see i'm with this guy. I wanted to say that but didn't know how! :p

Anyone else with theories of darkness? :D
 
Visage said:
Not quite. Photons do not have mass, but they do have momentum. Force = rate of change of momentum, ergo gravity bends light.
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Hang on a minute. Equation for momentum: p=mv right? Momentum = mass x velocity. So how can something with no mass hold any momentum?
 
eXSBass said:
Think about it, when you switch the light on, you get light speed. When you see lightning you see a flash. When you watch a movie you view pictures. All from light, which is fast light.

But then, when you switch the light off, you get dark speed? When the lightning dissappears, you get darkness. When you switch the television off, you see no pictures.
So then, at what speed is Dark Speed?
I might even be way off, WHAT is the speed of dark?

Is it just simply -299,792,458m/s? How would you measure the speed of dark when the Universe is dark?

Any ideas? :)
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Whilst I don't have any figures to hand for the speed of dark, I can tell you emphatically that it's got to be faster than the speed of light, as it's always dark before the light catches up.
 
Smithy said:
Hang on a minute. Equation for momentum: p=mv right? Momentum = mass x velocity. So how can something with no mass hold any momentum?
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p=h/lambda (planck's constant over wavelength) is the momentum.

It comes from a relativistic energy/mass equivalence equation http://online.cctt.org/physicslab/content/PhyAPB/lessonnotes/dualnature/Compton.asp


Werewolf said:
Whilst I don't have any figures to hand for the speed of dark, I can tell you emphatically that it's got to be faster than the speed of light, as it's always dark before the light catches up.
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:confused: :(
 
Werewolf said:
Whilst I don't have any figures to hand for the speed of dark, I can tell you emphatically that it's got to be faster than the speed of light, as it's always dark before the light catches up.
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Dark is the absence of light. An absence of something cannot have velocity :p. Try this thought experiment:
Say you turn on a torch at a mirror a good distance away. The light gets reflected back and gets to you at a certain time later. The instant you turn the torch off, you are illuminated for a further d/c seconds where d is the distance from torch to the reflector and back again and c is the speed of light. So the time for darkness to "appear" is simply the time delay between the last photon leaving the torch, and it returning once reflected. Ergo empirically the time for the 'signal' of an absence of light, is the speed of light itself.

Otherwise it’s like saying, when at a bus stop "the absence of a bus is quicker than the bus". It’s pure nonsense :)
 
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Smithy said:
Hang on a minute. Equation for momentum: p=mv right? Momentum = mass x velocity. So how can something with no mass hold any momentum?
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Because Newton was wrong :p
There are many situations where Netwon's laws break down and no longer work. It's just they work fine for most situations you'd have to deal with.
 
Smithy said:
Hang on a minute. Equation for momentum: p=mv right? Momentum = mass x velocity. So how can something with no mass hold any momentum?
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Because p does not equal mv. It is approximately mv for massive bodies at low speeds.
 
i see, well this is the only formula for momentum ive learnt so far in my physics course. I guess even though we study particle physics also, we dont study to the extent of involving other concepts such as laws of momentum etc.
Interesting though.
 
Smithy said:
i see, well this is the only formula for momentum ive learnt so far in my physics course. I guess even though we study particle physics also, we dont study to the extent of involving other concepts such as laws of momentum etc.
Interesting though.
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A Level right ;)
 
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