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From a million miles away, NASA camera shows moon crossing face of Earth

nasa.gov

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Re: From a million miles away, NASA camera shows moon crossing face of Earth

#151

Post by coldsmoke »

Sakes wrote: post #150
coldsmoke wrote: post #140

Earlier quoted context omitted.

But the satellite is at the L1 Lagrange point which is between the earth and the sun. So if you see the moon pass in front of the earth from L1 shouldn't the moon then also be directly between the earth and the sun? And as someone in another post noted: you can see the suns reflection in the ocean. And the moon passes directly over this spot.

All you can take away from the moon passing over the sun's reflection is this. The moon crossed over the sunlight reflected from the earth. To create a shadow, the moon must cross through the light emitted from the sun. This image might better help explain. Since the earth's orbital plane is in a different xy plane than the moon's, the moon crossing over the reflection guarantees nothing about whether it crossed the…

Ah, yes of course. And as cyanoacry noted in another comment, the satellite isn't actually in the Lagrange point - it is orbiting it. Thanks for clearing that up.

Re: From a million miles away, NASA camera shows moon crossing face of Earth

#152

Post by dredmorbius »

murbard2 wrote: post #139
vinhboy wrote: post #119

Earlier quoted context omitted.

Dang.. it never occurred to me how big the moon is. Looking at this picture, it's hard for me to comprehend why the moon would orbit the earth and not fall into the sun.

The moon is falling into the sun, just like the earth.

Falling but missing the ground.

RIP D.A.

Re: From a million miles away, NASA camera shows moon crossing face of Earth

#153

Post by krallja »

gojomo wrote: post #30

These pictures, at this angle, imply that the Earth regions under the moon were experiencing a solar eclipse, right? (Odd that the NASA article doesn't mention this.) EDIT: There was no solar eclipse at the "last month" time-frame these pictures were taken. So that isn't a real earth-shadow under the leading edge of the moon, and as close as the moon seems to pass over the perspective-center of Earth, it must have ac…

see discussion on this topic at https://news.ycombinator.com/item?id=10015354

Re: From a million miles away, NASA camera shows moon crossing face of Earth

#154

Post by Tuna-Fish »

sahaj wrote: post #147
Tuna-Fish wrote: post #125

Earlier quoted context omitted.

The gravitational influence of the Sun on the Moon is greater than the gravitational influence of the Earth. In a very real way, the moon is orbiting the Sun. However, the orbit it flies around the Earth only very slightly modifies it's orbit around the Sun. The lunar orbital speed around the earth is ~1km/s, while the orbital speed around the sun is ~30km/s. That is, it never loops backwards on it's path around the…

Is this also true of Jupiter's moons?

No. Europa and all the moons closer to Jupiter than it do in fact occasionally travel backwards in relation to their orbit around the Sun. This is also true of Dione and all the moons of Saturn lower than it, all the inner moons of Uranus, and all the regular moons of Neptune.

The gas giants are much more massive than earth, while also being much further away, and many of their moons orbit closer to them. This all combined makes some of their moons pulled more strongly by them than they are pulled by the sun.

Re: From a million miles away, NASA camera shows moon crossing face of Earth

#155

Post by Sakes »

coldsmoke wrote: post #151
Sakes wrote: post #150

Earlier quoted context omitted.

All you can take away from the moon passing over the sun's reflection is this. The moon crossed over the sunlight reflected from the earth. To create a shadow, the moon must cross through the light emitted from the sun. This image might better help explain. Since the earth's orbital plane is in a different xy plane than the moon's, the moon crossing over the reflection guarantees nothing about whether it crossed the…

Ah, yes of course. And as cyanoacry noted in another comment, the satellite isn't actually in the Lagrange point - it is orbiting it. Thanks for clearing that up.

Oh nice, ya, I didn't address the Lagrange point because I didn't have any knowledge of it.

Re: From a million miles away, NASA camera shows moon crossing face of Earth

#156

Post by mattlutze »

bmm6o wrote: post #136
mattlutze wrote: post #97

Earlier quoted context omitted.

Completely unnecessary side note: It's run by one of my old professors[1]! The whole physics department at Michigan Tech is a cool little diamond in the middle of the Upper Peninsula rough. 1: http://www.phy.mtu.edu/faculty/Nemiroff.html

(Totally off-topic, but that's not a very apt usage of "diamond in the rough": https://en.wiktionary.org/wiki/diamond_in_the_rough )

The UP is sparsely populated and not nationally known for high-tech industries or science, but rather wilderness, logging, mining, hunting, and general backwoods-ish-ness.

Houghton is the exception; hidden under that rough-and-wild exterior are some rather outstanding minds, particularly in physics and atmospheric sciences.

I think it works, but to each their own :)

Re: From a million miles away, NASA camera shows moon crossing face of Earth

#157

Post by PhantomGremlin »

rogeryu wrote: post #13
aspirin wrote: post #2

Is this the real reflectance of the moon? Seems so dark. Usually we see the moon at night surrounded by night sky, which probably skews our perception of the real color of the surface material.

Probably because that's the Dark Side of the Moon? https://en.wikipedia.org/wiki/The_Dark_Side_of_the_Moon

Thank you thank you thank you. I couldn't stop chuckling for at least five minutes.

I waited 24+ hours to respond because I didn't want to call undue attention to your comment. I didn't want anyone to downvote you for violating HN's unwritten proscript about humor.

Re: From a million miles away, NASA camera shows moon crossing face of Earth

#158

Post by vinhboy »

Tuna-Fish wrote: post #125
vinhboy wrote: post #119

Earlier quoted context omitted.

Dang.. it never occurred to me how big the moon is. Looking at this picture, it's hard for me to comprehend why the moon would orbit the earth and not fall into the sun.

The gravitational influence of the Sun on the Moon is greater than the gravitational influence of the Earth. In a very real way, the moon is orbiting the Sun. However, the orbit it flies around the Earth only very slightly modifies it's orbit around the Sun. The lunar orbital speed around the earth is ~1km/s, while the orbital speed around the sun is ~30km/s. That is, it never loops backwards on it's path around the…

Dude this is amazing. I did not know this. TIL.

Re: From a million miles away, NASA camera shows moon crossing face of Earth

#159

Post by bdavisx »

kjs3 wrote: post #105
bdavisx wrote: post #75

Earlier quoted context omitted.

But also don't underestimate the stupidity, ignorance and/or anti-intellectualism of the general American (as well as other countries) population. Remember that 1/3 of Americans do not believe in evolution...

Why do you automatically think all or even most Twitter comments are from Americans?

That was why I put "(as well as other countries)" on the comment; but I probably wasn't as clear as I could have been.

I specifically mentioned America because that's what I had the statistics around belief in evolution for. Also, I feel more qualified to comment on the "stupidity, ignorance and/or anti-intellectualism" of American's because I see/hear it every day.

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