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Why scientists say we need to send clocks to the moon

cnn.com

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Re: Why scientists say we need to send clocks to the moon

#21

Post by westurner »

lxgr wrote: post #17
westurner wrote: post #2

"Private moon lander will carry Nokia's 4G cell network to the lunar surface this year" https://www.space.com/nokia-4g-cell-network-on-the-moon Doesn't 4G include a time synchronization service for receivers with no GPS; and is the SI second unit (which is currently defined in terms of the cesium decay) const hardcoded in the new system?

> Doesn't 4G include a time synchronization service for receivers with no GPS Yes, but I believe accuracy is on the order of minutes. > is the SI second unit (which is currently defined in terms of the cesium decay) const hardcoded in the new system? Are you saying that a moon second should be defined to be slightly longer/shorter than an earth second to compensate for the relativistic difference? That wouldn't help,…

"Matrix Theory: Relativity Without Relative Space or Time" https://youtube.com/watch?v=B94o-P93ExU&

Does the time difference due to time dilation due to relativity change suddenly upon orbiting or landing on another planet spherical reference frame?

Re: Why scientists say we need to send clocks to the moon

#22

Post by vel0city »

lxgr wrote: post #17
westurner wrote: post #2

"Private moon lander will carry Nokia's 4G cell network to the lunar surface this year" https://www.space.com/nokia-4g-cell-network-on-the-moon Doesn't 4G include a time synchronization service for receivers with no GPS; and is the SI second unit (which is currently defined in terms of the cesium decay) const hardcoded in the new system?

> Doesn't 4G include a time synchronization service for receivers with no GPS Yes, but I believe accuracy is on the order of minutes. > is the SI second unit (which is currently defined in terms of the cesium decay) const hardcoded in the new system? Are you saying that a moon second should be defined to be slightly longer/shorter than an earth second to compensate for the relativistic difference? That wouldn't help,…

4G and 5G need devices to be synchronized to each other by like 1.5 microseconds or they'll start getting a lot of errors. They do a lot of time division duplexing, so if things are not well synchronized people start talking all over each other.

Now, that's just synchronized with each other, so if the Moon is off by whatever difference in time that's not a problem. It is not like that 4/5G cell is also participating in the same RF environment as cells on Earth.

Re: Why scientists say we need to send clocks to the moon

#23

Post by lxgr »

vel0city wrote: post #22
lxgr wrote: post #17

Earlier quoted context omitted.

> Doesn't 4G include a time synchronization service for receivers with no GPS Yes, but I believe accuracy is on the order of minutes. > is the SI second unit (which is currently defined in terms of the cesium decay) const hardcoded in the new system? Are you saying that a moon second should be defined to be slightly longer/shorter than an earth second to compensate for the relativistic difference? That wouldn't help,…

4G and 5G need devices to be synchronized to each other by like 1.5 microseconds or they'll start getting a lot of errors. They do a lot of time division duplexing, so if things are not well synchronized people start talking all over each other. Now, that's just synchronized with each other , so if the Moon is off by whatever difference in time that's not a problem. It is not like that 4/5G cell is also participating…

Yeah, that’s what I mean: They don’t need an absolute time reference; they can just respond with whatever delay/frequency offset compensates for the one observed as they communicate.

S-CDMA did have close timing requirements between cells, as far as I know, but the GSM/3GPP family of standards never did.

Re: Why scientists say we need to send clocks to the moon

#24

Post by lxgr »

westurner wrote: post #21
lxgr wrote: post #17

Earlier quoted context omitted.

> Doesn't 4G include a time synchronization service for receivers with no GPS Yes, but I believe accuracy is on the order of minutes. > is the SI second unit (which is currently defined in terms of the cesium decay) const hardcoded in the new system? Are you saying that a moon second should be defined to be slightly longer/shorter than an earth second to compensate for the relativistic difference? That wouldn't help,…

"Matrix Theory: Relativity Without Relative Space or Time" https://youtube.com/watch?v=B94o-P93ExU& Does the time difference due to time dilation due to relativity change suddenly upon orbiting or landing on another planet spherical reference frame?

Not suddenly, but gradually as you enter/leave the gravitational well.

The dominating relativistic factor is the gravitational potential (ie general relativity), not the orbital velocity (special relativity), as far as I understand.

GPS compensates for both by offsetting the frequency standard of the satellites’ atomic clocks accordingly.

Re: Why scientists say we need to send clocks to the moon

#25

Post by Aaron2222 »

ARandomerDude wrote: post #15

> On the lunar surface, a single Earth day would be roughly 56 microseconds shorter than on our home planet — a tiny number that can lead to significant inconsistencies over time. Given that there are 86,400,000,000 microseconds in a day, we will need a leap year every 1.5 billion years to stay in sync. I think we’ll be fine.

Or more realistically, a leap second every ~49 years.

Re: Why scientists say we need to send clocks to the moon

#26

Post by nitwit005 »

krisoft wrote: post #10

Idk. Is this actually needed in practice? Most RTC chips are off by several seconds per day. If you need accurate time you sync them to an outside source (a network time server or GPS). Does it matter if your oscillator is 56 microseconds off because of relativistic effects if it is off by multiple seconds because the chip is cheap? You need some sort of network connections back to Earth anyway, can't you just spare…

> Is this actually needed in practice?

No.

The actual problem is a political one. Past missions have used the local time from where the mission was based. They want an agreed time for international missions.

This talk of ultra precise clocks being sent to the moon seems very unlikely to happen, as it isn't relevant to solving the political problem.

Re: Why scientists say we need to send clocks to the moon

#27

Post by g_p »

lxgr wrote: post #23
vel0city wrote: post #22

Earlier quoted context omitted.

4G and 5G need devices to be synchronized to each other by like 1.5 microseconds or they'll start getting a lot of errors. They do a lot of time division duplexing, so if things are not well synchronized people start talking all over each other. Now, that's just synchronized with each other , so if the Moon is off by whatever difference in time that's not a problem. It is not like that 4/5G cell is also participating…

Yeah, that’s what I mean: They don’t need an absolute time reference; they can just respond with whatever delay/frequency offset compensates for the one observed as they communicate. S-CDMA did have close timing requirements between cells, as far as I know, but the GSM/3GPP family of standards never did.

TDD networks (where the same frequency is used for downlink and uplink, but with timeslots for each) do need tight timing between cells though, but it doesn't have to be absolute - just in sync with each other so one cell doesn't blast out a full power downlink while adjacent and nearby cells are quietly trying to listen for the (much quieter) uplink transmissions of their user devices.

Re: Why scientists say we need to send clocks to the moon

#28

Post by yencabulator »

nitwit005 wrote: post #26
krisoft wrote: post #10

Idk. Is this actually needed in practice? Most RTC chips are off by several seconds per day. If you need accurate time you sync them to an outside source (a network time server or GPS). Does it matter if your oscillator is 56 microseconds off because of relativistic effects if it is off by multiple seconds because the chip is cheap? You need some sort of network connections back to Earth anyway, can't you just spare…

> Is this actually needed in practice? No. The actual problem is a political one. Past missions have used the local time from where the mission was based. They want an agreed time for international missions. This talk of ultra precise clocks being sent to the moon seems very unlikely to happen, as it isn't relevant to solving the political problem.

Then it's a lot of hot air where UTC would suffice.

Re: Why scientists say we need to send clocks to the moon

#29

Post by yencabulator »

lxgr wrote: post #16
krisoft wrote: post #10

Idk. Is this actually needed in practice? Most RTC chips are off by several seconds per day. If you need accurate time you sync them to an outside source (a network time server or GPS). Does it matter if your oscillator is 56 microseconds off because of relativistic effects if it is off by multiple seconds because the chip is cheap? You need some sort of network connections back to Earth anyway, can't you just spare…

> Is this actually needed in practice? For scientific experiments of the type one might be running on the moon? Almost certainly for at least some of them.

What's the difference between correcting a lunar-bound oscillator for this new time standard versus correcting it for UTC?
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