 | | From: | Martin Johansen | | Subject: | Is light perpetual motion? | | Date: | Mon, 24 Jan 2005 03:01:03 +0100 |
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 | A few questions on the topic of light.
1. Is light an example of perpetual motion?
2. Does the frequence of light remain the same as it travels in vacum?
3. Since the speed of light does not depend on the speed of the transmitter,
then what determines the speed at which it travels?
4. The infamous redshift is used as an argument of an expanding universe,
fine, but does light suffer noe energy loss at this distance, even due to
other factors?
It seems *very* coincidental that more remote objects gives more redshift.
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| | From: | Franz Heymann | | Subject: | Re: Is light perpetual motion? | | Date: | Mon, 24 Jan 2005 07:43:45 +0000 (UTC) |
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"Martin Johansen" wrote in message
news:EFYId.5716$IW4.117722@news2.e.nsc.no...
> A few questions on the topic of light.
>
> 1. Is light an example of perpetual motion?
No more so than any other object in motion in free space.
> 2. Does the frequence of light remain the same as it travels in
vacum?
Yes
> 3. Since the speed of light does not depend on the speed of the
transmitter,
> then what determines the speed at which it travels?
It is a constant of nature whose numerical value depends on the system
of units in use.
If you know anything about relativity and space-time, you will knoe
what I mean when I say it is the conversion factor for converting the
units for a measurement in the time direction to those for one in a
space direction
> 4. The infamous redshift
There is nothing infamous about it.
is used as an argument of an expanding universe,
> fine, but does light suffer noe energy loss at this distance, even
due to
> other factors?
No
>
> It seems *very* coincidental that more remote objects gives more
redshift.
No, not now that the reason is understood
Franz
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| | From: | Old Man | | Subject: | Re: Is light perpetual motion? | | Date: | Mon, 24 Jan 2005 02:48:16 -0600 |
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"Martin Johansen" wrote in message
news:EFYId.5716$IW4.117722@news2.e.nsc.no...
>A few questions on the topic of light.
>
> 1. Is light an example of perpetual motion?
Light propagation is friction-free. Light doesn't get tired.
> 2. Does the frequence of light remain the same as it travels in vacum?
Locally, yes, but globally, the wavelength increases because
the "vacuum" is expanding while light is in transit between
source and detector.
> 3. Since the speed of light does not depend on the speed of the
> transmitter, then what determines the speed at which it travels?
The space-time metric of free-space has but one parameter:
the locally observed speed of light. The explanation goes no
deeper than that. The speed of light isn't predicted from
theory. It's measured.
> 4. The infamous redshift is used as an argument of an expanding universe,
> fine, but does light suffer noe energy loss at this distance, even due to
> other factors?
Astronomers are aware that space isn't entirely free of matter.
Light can loss energy via multiple Compton scatterings from
electrons.
> It seems *very* coincidental that more remote objects gives more redshift.
Not ad-hoc, BBT is consistent with the laws of physics and
generates a multitude of empirically falsifiable predictions.
There aren't any proofs or necessary conditions in physics.
The predictions of physics are at most empirically sufficient
to Nature.
[Old Man]
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| | From: | robert j. kolker | | Subject: | Re: Is light perpetual motion? | | Date: | Sun, 23 Jan 2005 21:15:05 -0500 |
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Martin Johansen wrote:
> A few questions on the topic of light.
>
> 1. Is light an example of perpetual motion?
No.
>
> 2. Does the frequence of light remain the same as it travels in vacum?
not if the light interacts with some kind of matter.
>
> 3. Since the speed of light does not depend on the speed of the transmitter,
> then what determines the speed at which it travels?
nothing. Light goes as fast in a vacuum as it goes. Its speed is a fact.
Bob Kolker
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| | From: | Greg Neill | | Subject: | Re: Is light perpetual motion? | | Date: | Sun, 23 Jan 2005 22:28:17 -0500 |
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| "robert j. kolker" wrote in message news:35j41cF4jofpcU1@individual.net...
> > 2. Does the frequence of light remain the same as it travels in vacum?
>
> not if the light interacts with some kind of matter.
Or if it travels far enough and long enough that its
wavelength is "stretched" by the universe's expansion.
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| | From: | Sam Wormley | | Subject: | Re: Is light perpetual motion? | | Date: | Mon, 24 Jan 2005 02:44:48 GMT |
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| Martin Johansen wrote:
> A few questions on the topic of light.
Relativistic Redshift
http://scienceworld.wolfram.com/physics/RelativisticRedshift.html
Gravitational Redshift
http://scienceworld.wolfram.com/physics/GravitationalRedshift.html
Doppler Effect
http://scienceworld.wolfram.com/physics/DopplerEffect.html
Did you ever wonder "What the heck is a photon, anyway?"
http://math.ucr.edu/home/baez/photon/schmoton.htm
Read Ned Wright's Cosmology Tutorial
http://www.astro.ucla.edu/~wright/cosmolog.htm
http://www.astro.ucla.edu/~wright/cosmology_faq.html
WMAP: Foundations of the Big Bang theory
http://map.gsfc.nasa.gov/m_uni.html
WMAP: Tests of Big Bang Cosmology
http://map.gsfc.nasa.gov/m_uni/uni_101bbtest.html
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