On 8/11/2011 12:03 AM, Stephen P. King wrote:
On 8/11/2011 2:54 AM, meekerdb wrote:
On 8/10/2011 11:24 PM, Stephen P. King wrote:
And interesting choice of examples since that exactly what man has
done. The speed of light is nothing but a conversion constant
between units. In 1983 the speed of light in SI units was
*defined* to be 299,792,458 m/s.
Umm, not so fast. The permitivity and permiability of the vacuum
are not set by prior theory! It is still only a known fact due to
measurement.
No. The length of the meter was set as the distance traveled by
light in 1/299792458 of a second. So permitivity and permiabilty are
not fundamental but are derived values (for the vacuum).
Brent
Hi Brent,
Seriously? The speed of light in a vacuum is proportional to the
ration of permeability to permittivity of the vacuum (see Maxwell's
equations). Those quantities are not derived from any theory. So we
measure the time it takes a beam of light to travel some distance in a
vacuum.... how is the vacuum achieved?
You're still assuming it's measured. It's not measured; it's used to
define the meter so it's an exact number.
What determines the accuracy of the clocks used?
Accuracy compared to what? The second is the duration of 9 192 631 770
periods of the radiation corresponding to the transition between the two
hyperfine levels of the ground state of the cesium 133 atom.
Brent
We can go around and around on this, for what? In your accounting what
defined that the speed of light in SI units is not
299,792,458.000000000000000000000000001212423452345 m/s or
299,792,458.00000000000000000000000000000000000000000004567 m/s or ... ?
Onward!
Stephen
--
You received this message because you are subscribed to the Google Groups
"Everything List" group.
To post to this group, send email to everything-list@googlegroups.com.
To unsubscribe from this group, send email to
everything-list+unsubscr...@googlegroups.com.
For more options, visit this group at
http://groups.google.com/group/everything-list?hl=en.
