Re: Will Somebody PleaseTell bz What an Inertial Frame is.

"Arthur Dent" <jp006t2227@xxxxxxxxxxxxxxxx> wrote in
news:1120263553.618481.170050@xxxxxxxxxxxxxxxxxxxxxxxxxxxx:

>
>
> bz wrote:
>> "Arthur Dent" <jp006t2227@xxxxxxxxxxxxxxxx> wrote in
>> news:1120166750.294775.113260@xxxxxxxxxxxxxxxxxxxxxxxxxxxx:
>>
>> >
>> >
>> > bz wrote:
>> >> "Arthur Dent" <jp006t2227@xxxxxxxxxxxxxxxx> wrote in
>> >> news:1120153968.252223.60740@xxxxxxxxxxxxxxxxxxxxxxxxxxxx:
>> >>
>> >> >
>> >> >
>> >> > bz wrote:
>> >> >
>> >> >> That usually happens with good ideas.
>> >> >>
>> >> >> > Newsgroups: sci.physics.relativity
>> >> >> > From: "Androcles" <androc...@xxxxxxxx> - Find messages by this
>> >> >> > author Date: 1999/02/23
>> >> >> > [quote]
>> >> >> > Send a laser
>> >> >> > and a maser into orbit, bounce a signal to the moon and back at
>> >> >> > moon-rise
>> >> >> > and time it. Repeat at moon-noon and moon-set 45 minutes later.
>> >> >> > Get the difference. Then we'll know.
>> >> >> > [unquote]
>> >> >>
>> >> >> If Henri is right, photons, even from a surface laser, at
>> >> >> moonrise and moonset, should do. Compare to 'at zenith. Correct
>> >> >> for the atmosphere.
>> >> >
>> >> > Phooey, what does Henri know...
>> >> >
>> >> > Tangential speed of Moon relative to Earth: 360 degrees/month.
>> >> > Radial speed of Moon relative to Earth: (Apogee - Perigee)/14 days
>> >> > = practically zilch.
>> >>
>> >> tangential speed of earth = circumference/24 hr = 1038 mph
>> >
>> > Ok... that's quite lot slower than an orbiter, Concorde and most
>> > military fighters could outpace it.
>>
>> Of course.
>>
>> >> > Speed of light in atmosphere c/n, n the refractive index, but n
>> >> > tends to 1 as the density goes down.
>> >> > Speed of light from Earth to Moon, c.
>> >>
>> >> > Tangential speed of ISS and shuttle orbiters relative to Earth, >
>> >> > 5 km/sec
>> >> > Speed of light from orbiter to moon, c + cos(phi) * 5 km/sec, not
>> >> > zilch.
>> >> > Beats me when people are going to wake up to the concept of
>> >> > relative speed, even for light.
>> >>
>> >> You might only be able to count on the c +/- 1038 mph for the earth
>> >> to moon leg. Figure that the trip back will be made at c.
>> >
>> > Wasn't it you that said a mirror wouldn't change the VELOCITY of
>> > light, and I that said it would, v = -v, and then you agreed? So how
>> > come you are contradicting yourself now? Get a grip, old son.
>>
>> Lunar corner reflectors are not mirrors.
>> http://physics.ucsd.edu/~tmurphy/apollo/lrrr.html
>
> "a trio of mutually perpendicular surfaces such as is found at the
> corner of a cube (look up into the corner of the room where the ceiling
> hits the walls). If these three surfaces are reflective "
>
> I call a reflective surface a "mirror". What do you call it?

Transparent materials, such as glass, appear to limit photons to the speed
of light in the material. The extinction length for c' photons would be
very short.

Front surface mirror would be the only kind I would expect to allow the
photons to retain their velocity [and I am not even sure that can be
counted on].

.....
>>
>> However, the main problem is that the corner reflector returns the
>> reflection along the incoming beams line. We can lead the target with
>> our outgoing beam to compensate for propagation delay but the return
>> beam will miss us unless we purposely spread the beam. If we do that,
>> we increase the path losesses.
>
> Just speed up the light, then :-)

kinda hard to do, at will, otherwise there would be no point in our
discussion.


.....
>> Cost/return ratio?
> Yep. Seems that is what we've been discussing, in orbit vs on the
> ground.

I thought ground might be worth trying. Orbit is, of course better.

> You want the power upped to break through atmosphere and are willing to
> measure the wind of the upper atmosphere for every trial, I want less
> (or the same) power and no atmosphere at all.
> Since I'm not the CFO of any organization, I'd have to guess that
> putting a laser into obit woud have other uses as well. Sooner or later
> some bright spark
> on the ISS is going to point a laser at the mooon anyway.

won't help much unless the rest of the apparatus is there at the same time.

.....
>> > Phooey. I see the light from my headlights corner-reflected from the
>> > car in front, and my eyes are not down at the headlight.
>>
>> That is because automotive tail-light corner reflectors are designed to
>> spread the beam by a certain amount. So are the glass beads use on
>> signs.
>>
>> The lunar corner reflectors are designed to avoid spreading the beam.
>
> "The palette is 0.45 meters square, and carefully designed to minimize
> thermal gradients across the corner cubes as the array is slammed into
> and out of the sun's rays as the moon's phase changes. This prevents
> thermal distortions from seriously degrading the amount of light
> returned by the reflectors."
> Minimize is not synonymous with "eliminate".

Minimize thermal gradient...prevent thermal distortion from seriously
degrading....

"Eliminate" would not fit any part of the sentence.

.....
>> What I suggest would be no more costly that a small celestron, a 5 watt
>> laser diode, a ccd, and some computer power. Less than 20k bux should
>> do it fine.
>
> How are you going to get 5 watts of light through the Earth's
> atmosphere when the moon is on the horizon and you have the full 1038
> mph? You don't have that speed with the moon overhead. Up the power, I
> thought you said.

The 5 watts was for an ISS apparatus.
>From Earth, 50 watts would be more likely.

>> >> GPS is fine for knowing where the ISS is, but its orbit is known
>> >> accurately.
>> > That's no problem then. :-)
>>
>> Not quite. The location of the ranging telescope is going to need to be
>> known very accurately.
>
> That's no problem, then. You've just said it WAS known accurately.
>
> I think the experiment can be done, should be done and will be done.
> The question is when?
> Until then this newsgroup will go on arguing about twins staying home
> and hurtling off to Alpha Centauri or wherever, coming back younger,
> poles fitting in barns and calling the other "idiot". Heck, we still
> have some dyed-in-the-wool aetherialists spouting off away. Pitting
> logic against faith doesn't work.




--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

bz+sp@xxxxxxxxxxxxxxxxxxxx remove ch100-5 to avoid spam trap
.

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