Recent comments in /f/space

scratch_post t1_j63ojl2 wrote

Reply to comment by Head_Weakness8028 in What time is it on the Moon? - Satellite navigation systems for lunar settlements will require local atomic clocks. Scientists are working out what time they will keep. by speckz

Universal time doesn't make sense in the context of General Relativity. The only thing two observers in different reference frames can agree on is what is known as the 'spacetime interval.' Caused by the Lorentz contraction. This interval is both a distance and a time measurement, which you're likely already familiar with. Afterall, when you want to meet with someone, you have to give a minimum of two abstract things, a location, and time. spacetime interval^2 = ({change of time}*c)^(2) - {change of x}^(2) - {change of y}^(2) - {change of z}^(2)

3

KTNH8807 t1_j63nujo wrote

Reply to comment by therestruth in NASA's Annual Day of Remembrance today, Jan. 26, honors the astronauts who died during the Apollo 1 fire and the Challenger and Columbia space shuttle disasters. by clayt6

Probably should have said “In” instead of “over” . Once we die, our matter that makes us up will stay with the earth, then once the earth is absorbed by the sun in its red giant phase it will stay with the sun, then the sun sheds its outer layers in a planetary nebula and leaves a white dwarf. THEN over a very very very long time after that, all that matter will be absorbed by a black hole.

2

Sharlinator t1_j63i31s wrote

Reply to comment by JustAPerspective in Earth's inner core may be slowing down, but “Nothing cataclysmic is happening,” says Hrvoje Tkalcic, a geophysicist at Australian National University. “The inner core is now more in sync with the rest of the planet than a decade ago when it was spinning a bit faster.” by clayt6

It’s not a “magnetic engine” in any relevant sense. It’s a huge rotating ball of iron and nickel and conservation of angular momentum is a thing! Truly ludicrous amounts of momentum would have to be transferred somewhere else for it to stop rotating.

(Now, to be fair, a mechanism does exist that slowly bleeds off Earth’s rotational momentum, and has done so for billions of years: the moon and its tidal forces. In the far future Earth would become tidally locked with the moon, and rotate very slowly, if the sun didn’t become a red giant first. But somehow only slowing down the core? That would require magic.)

Anyway, my use of “absolutely” should be taken in the context of the discussion, just like everything else. There’s no reason to add some sort of an “except via magic” to every other sentence, pedantic Redditors notwithstanding.

4

JustAPerspective t1_j63ge95 wrote

Reply to comment by Sharlinator in Earth's inner core may be slowing down, but “Nothing cataclysmic is happening,” says Hrvoje Tkalcic, a geophysicist at Australian National University. “The inner core is now more in sync with the rest of the planet than a decade ago when it was spinning a bit faster.” by clayt6

>There’s absolutely nothing that could make it actually
>
>stop
>
>.

The limits of human imagination in no way apply to reality.

Also, a magnetic engine can cease to function rather quickly when specific criteria change, so you may want to throttle back on "Absolutely".

1