| Topic: |
Science > Physics |
| User: |
"Pentcho Valev" |
| Date: |
24 Nov 2006 01:12:46 AM |
| Object: |
EINSTEINIANS TEACH |
http://www.math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/speed_of_light.html
"Is c, the speed of light in vacuum, constant? At the 1983 Conference
Generale des Poids et Mesures, the following SI (Systeme International)
definition of the metre was adopted: The metre is the length of the
path travelled by light in vacuum during a time interval of 1/299 792
458 of a second. This defines the speed of light in vacuum to be
exactly 299,792,458 m/s. This provides a very short answer to the
question "Is c constant": Yes, c is constant by definition!.....Any
such possible photon rest mass is certainly too small to have any
practical significance for the definition of the metre in the
foreseeable future, but it cannot be shown to be exactly zero--even
though currently accepted theories indicate that it is. If it wasn't
zero, the speed of light would not be constant; but from a theoretical
point of view we would then take c to be the upper limit of the speed
of light in vacuum so that we can continue to ask whether c is
constant."
Pentcho Valev
.
|
|
| User: "Helmut Wabnig .... --. .- -... -. .. .-- @ .- --- -. DOT .- -" |
|
| Title: Re: EINSTEINIANS TEACH |
24 Nov 2006 02:51:22 AM |
|
|
On 23 Nov 2006 23:12:46 -0800, "Pentcho Valev" <pvalev@yahoo.com>
wrote:
http://www.math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/speed_of_light.html
"Is c, the speed of light in vacuum, constant? At the 1983 Conference
Generale des Poids et Mesures, the following SI (Systeme International)
definition of the metre was adopted: The metre is the length of the
path travelled by light in vacuum during a time interval of 1/299 792
458 of a second. This defines the speed of light in vacuum to be
exactly 299,792,458 m/s. This provides a very short answer to the
question "Is c constant": Yes, c is constant by definition!.....Any
such possible photon rest mass is certainly too small to have any
practical significance for the definition of the metre in the
foreseeable future, but it cannot be shown to be exactly zero--even
though currently accepted theories indicate that it is. If it wasn't
zero, the speed of light would not be constant; but from a theoretical
point of view we would then take c to be the upper limit of the speed
of light in vacuum so that we can continue to ask whether c is
constant."
Pentcho Valev
Sure you can, if you can.
Measure c to an accuracy below 1 m/sec. If you can.
That's the reason why they decided to give up :-)
(NIST & Co).
w.
.
|
|
|
|
| User: "Sue..." |
|
| Title: Re: EINSTEINIANS TEACH |
24 Nov 2006 03:18:44 AM |
|
|
Pentcho Valev wrote:
http://www.math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/speed_of_light.html
"Is c, the speed of light in vacuum, constant? At the 1983 Conference
Generale des Poids et Mesures, the following SI (Systeme International)
definition of the metre was adopted: The metre is the length of the
path travelled by light in vacuum during a time interval of 1/299 792
458 of a second. This defines the speed of light in vacuum to be
exactly 299,792,458 m/s. This provides a very short answer to the
question "Is c constant": Yes, c is constant by definition!.....Any
such possible photon rest mass is certainly too small to have any
practical significance for the definition of the metre in the
foreseeable future, but it cannot be shown to be exactly zero--even
though currently accepted theories indicate that it is. If it wasn't
zero, the speed of light would not be constant; but from a theoretical
point of view we would then take c to be the upper limit of the speed
of light in vacuum so that we can continue to ask whether c is
constant."
Pentcho Valev
The metrologist's 'c' is not the same as the physicicist's 'c'.
They find some common ground here:
http://physics.nist.gov/cuu/Constants/alpha.html
The 'squishy' factors mu_0 and eps_0 used by a
Maxwell compliant physicist:
http://en.wikipedia.org/wiki/Wave_impedance
....don't fit well with the metrologist's goal of
producing repeatable standards for measurment.
Indeed, we continue to ask if alpha is constant.
Sue...
.
|
|
|
|
|
Related Articles |
|
|
