TIL Mars has a Moon that travels in the wrong direction.
Then shortly after, I learnt it doesn’t.
Phobos's orbit and its apparent motion across the Martian sky
31–40 of 50 posts
Re: Phobos's orbit and its apparent motion across the Martian sky
#32Jupiter has some moons that really do go the "wrong" way: the Carme, Ananke, and Pasiphae groups.
Neptune's moon Triton as well: https://en.wikipedia.org/wiki/Triton_(moon)
Re: Phobos's orbit and its apparent motion across the Martian sky
#33Earlier quoted context omitted.
I thought it was an interesting article. Also, your comment breaks the guidelines: > Please don't post shallow dismissals, especially of other people's work. A good critical comment teaches us something. https://news.ycombinator.com/newsguidelines.html
It's a good comment because it summarizes the article better than the title does. Every article with a misleading title should have a top comment like that.
Ok, we've replaced the title with a substring of the subtitle that is presumably less misleading.
(in keeping with "Please use the original title, unless it is misleading or linkbait" - https://news.ycombinator.com/newsguidelines.html)
Re: Phobos's orbit and its apparent motion across the Martian sky
#34To capture our attention obviously. What nobody is mentioning is that the moon is actually unnaturally round .
Unnaturally?
Re: Phobos's orbit and its apparent motion across the Martian sky
#35Fun fact.. we could slow down phobos, sending it crashing into mars.. it would be human possible, with todays technologies right now.. we even could pick a spot.. and start with this smash a terraforming program.
Re: Phobos's orbit and its apparent motion across the Martian sky
#36This is a whole lotta words and graphics to explain something that literally takes two sentences: Phobos orbits Mars faster than Mars rotates itself, while Deimos rotates slower than Mars. Thus from the ground their apparent motion is opposing in the sky; Deimos rises in the east and sets in the west, while Phobos does the opposite. Done.
This Earth has many artificial satellites that do that.
There's not that many satellites outside of GEO, and even those that go beyond are usually not circularized (e.g. Molniya orbits), so tend to have shorter periods. Unless you count things in GEO graveyard orbits (which rise very, very slowly in the west -- their orbit is just slightly less than synchronous), I can't think of a significant population of artificial satellites that orbit slower than earth rotates.
Re: Phobos's orbit and its apparent motion across the Martian sky
#37Earlier quoted context omitted.
That’s actually fairly common. The really unsettling question is “why is the moon exactly the same size in the sky as the sun?”. A little bit smaller and we wouldn’t see full solar eclipses, a little bit bigger and we wouldn’t see the suns corona during an eclipse. Another unsettling feature is that the moon is moving further away from the earth so in a few million years’ time, we won’t even have full solar eclipses.…
chances are if weren’t in that phase, there would be some other phenomena we’d be observing in awe and feeling special about it
Exactly :)
https://numbergenerator.org/randomnumbergenerator/1-10000000...
Wow! 197100522! (what i got on my first hit)
Out of all the possible numbers, what are the odds? 1 in a billion! Two consecutive 0's! And two consecutive twos! What do you think they mean? And 5 in between? Well 5 times 2 is 10 which ends in a 0. But it starts with 1971, which is only 1 year off from the start of Unix time, which can't be a coincidence! etc.
Re: Phobos's orbit and its apparent motion across the Martian sky
#38What I find unsettling is that our Moon rotates at a the precise perfect speed to make us "see always the same side". From all the possible speed values in the universe, why precisely that one?!
That’s actually fairly common. The really unsettling question is “why is the moon exactly the same size in the sky as the sun?”. A little bit smaller and we wouldn’t see full solar eclipses, a little bit bigger and we wouldn’t see the suns corona during an eclipse. Another unsettling feature is that the moon is moving further away from the earth so in a few million years’ time, we won’t even have full solar eclipses.…
> The really unsettling question is “why is the moon exactly the same size in the sky as the sun?”
Can't wait until the moment in the future where
DISTANCE_FROM_EARTH_TO_MOON / DISTANCE_FROM_EARTH_TO_SUN = FINE_STRUCTURED_CONSTANTRe: Phobos's orbit and its apparent motion across the Martian sky
#39Earlier quoted context omitted.
chances are if weren’t in that phase, there would be some other phenomena we’d be observing in awe and feeling special about it
Exactly :) https://numbergenerator.org/randomnumbergenerator/1-10000000... Wow! 197100522! (what i got on my first hit) Out of all the possible numbers, what are the odds? 1 in a billion! Two consecutive 0's! And two consecutive twos! What do you think they mean? And 5 in between? Well 5 times 2 is 10 which ends in a 0. But it starts with 1971, which is only 1 year off from the start of Unix time, which can't be a co…
Not to mention that it contains the digits of 1215 - the year of Magna Carta.
Re: Phobos's orbit and its apparent motion across the Martian sky
#40Fun fact.. we could slow down phobos, sending it crashing into mars.. it would be human possible, with todays technologies right now.. we even could pick a spot.. and start with this smash a terraforming program.
1. We have human technologies to impact 625m/s of delta-V to a moon that weighs 10,000,000,000,000 tonnes? [1]
2. What exactly would that accomplish?
[1] Should 'only' take 2 * 10^21 joules of energy[2].
[2] Humanity's annual energy consumption is 5.8 * 10^20 joules.