Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: bizerl on 04/10/2012 01:37:58
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Or indeed, any sort of sub-atomic particle. It seems that most of the references to them involve movement through radiation etc., could any sub-atomic particles be described as stationary?
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Does it count if I can ride my bicycle (downhill) faster than a photon?
The speed of light is normally about 186,000 miles per second, or fast enough to go around the world seven times in the wink of eye.
Scientists succeeded in slowing it down to 38 mph.
They did this by shooting a laser through extremely cold sodium atoms, which worked like “optical molasses” to slow the light down.
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Only if you can ride your bicycle through extremely cold sodium atoms. [:D]
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"stationary" or very slow moving photons are essentially bouncing around between atoms without loss in an atomic trap.
It is true that all matter and subatomic particles are usually moving around quite quickly but they can be slowed down, however as you slow them down because of the uncertainty principle their positions get more and more indistinct, and their De Broglie wavelength (QV look this up in Google) longer. if a particle became totally "stationary" it would in theory be a big as the universe however we cannot know what "stationary" is with respect to the universe and that would almost certainly not be stationary with respect to the observer.
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Depends how you look at it. We have two definitions right? A recoil and a annihilation. It's the last case that will represent the 'photon' itself, interacting with your detector. But you can make a really convincing argument for that the recoil also must represent that 'photon' as without that argument all ideas of a 'speed' becomes meaningless. So let's assume :) that both are descriptions of the same phenomena, a recoil and a subsequent annihilation.
Between those two there will be a distance, and a time passed using your wristwatch and ruler.
But, the annihilation itself is 'instant' as far as I think, it's happening at 'c' which is the fastest description we have even though that it will take time to be treated and communicated to the detectors 'senses'. So, can we imagine a speed faster than 'c'? Sure, but not according to our experiments, there 'c' is a limit. And so is the 'recoil' letting that 'photon' go, also immediately at 'c'.
Now, those two events, what do they represent? Each one a measurable 'time', or not? I say 'not' :)
And the distance and time measured between them then? Yeah that's what we define as the 'time and distance' it takes for that 'photon' to propagate.
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"Is there such thing as a stationary photon?"
Yes. Write "photon" on a paper and make sure it stays stationary [;D]