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ESA looking to define a time standard for the Moon
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Stray Electron:

--- Quote from: tggzzz on March 02, 2023, 03:20:42 pm ---I see three main issues:

* defining a time system for on and orbiting the moon
* accounting for the astronomical and relativistic differences
* defining the time visible on earth
The first seems tractable, and relatively boring.

The second is well known from physical principles, but the details are probably difficult to resolve.

The third I simply don't understand. Imagine sending pings between the earth and moon. If someone sends ping1 the earth at time t, the signal will take 1s to reach the moon, and an instantaneous ping2 response would arrive back on earth at time t+2. Earth then sends ping3.

At what time do all parties agree  the ping1 received on the moon?
At what time do all parties agree the ping2 received on earth?
At what time do all parties agree  the ping3 received on the moon?


--- End quote ---

   I wonder if they'll want to divide Moon Time into zones like they did with time zones on the earth?   If local Moon Time roughly follows the lunar sun rise and sun set as it does on earth, then Moon Time Zones will be completely out of sync with anything that we're familiar with.

   It sounds like someone is about to propose a very complex answer to a problem that really doesn't exist yet.
tggzzz:

--- Quote from: karpouzi9 on March 02, 2023, 06:09:09 pm ---
--- Quote from: tggzzz on March 02, 2023, 03:20:42 pm ---

* defining the time visible on earth

The third I simply don't understand. Imagine sending pings between the earth and moon. If someone sends ping1 the earth at time t, the signal will take 1s to reach the moon, and an instantaneous ping2 response would arrive back on earth at time t+2. Earth then sends ping3.

At what time do all parties agree  the ping1 received on the moon?
At what time do all parties agree the ping2 received on earth?
At what time do all parties agree  the ping3 received on the moon?

--- End quote ---

There's one simple answer: take the average relativistic dilation factor between Earth's surface and the Moon's surface. Then, change the number of seconds in an hour by that factor. A lunar hour might have 60.0000005 Earth seconds in it.

--- End quote ---

That answer may turn out to be relevant to the part of my post that you didn't quote. It isn't relevant to the part you did quote.
tggzzz:

--- Quote from: karpouzi9 on March 03, 2023, 08:59:50 pm ---The difference between the terrestrial HFT mob and the Moon is that there's no significant relative time dilation between points on Earth's surface. Everyone is co-moving around the core at the same distance in the same gravity well.

This source claims the effect is only 0.66 parts per billion, so about 2 seconds every 100 years. Significant for GPS/RTK applications but not much else.

--- End quote ---

That is a difference. It is not the only difference, nor is it the most interesting and difficult to resolve difference.
nctnico:

--- Quote from: karpouzi9 on March 03, 2023, 08:59:50 pm ---The difference between the terrestrial HFT mob and the Moon is that there's no significant relative time dilation between points on Earth's surface. Everyone is co-moving around the core at the same distance in the same gravity well.

--- End quote ---
Not quite. Due to the rotational speed of the earth, network packets (or better put: the electrical or optical signals that represent the data) will move at different speeds depending on which direction they are travelling. https://en.wikipedia.org/wiki/Sagnac_effect Precise time distribution systems have to compensate for this effect.
Alex Eisenhut:
Will there also be a Moonlight Savings Time?
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