#### Comment Preferences

• ##### Live and learn(4+ / 0-)

There's a lot in this that I don't quite understand (especially about Lagrange points), but it's very interesting.

"The smartest man in the room is not always right." -Richard Holbrooke

• ##### What don't you understand? I guess I should have (6+ / 0-)

explained better.

Anytime you have one body orbiting another, there are points of gravitational stability (where the gravity of the two bodies basically cancel each other out). These are spots where anything that is there or was put there would stay, mostly, without having to be in its own orbit.

Hopefully that is clearer.

Getting Democrats together and keeping them that way is like herding cats that are high on meth, through L.A., during an earthquake, in the rain -6.25, -6.10

[ Parent ]

• ##### L1 and L2(4+ / 0-)

Well, that helped. But if L1 and L2 are points where the moon's and the earth's gravity cancel each other out, why are they outside the orbit of the moon, whereas L3, L4 and L5 are on the orbit of the earth?

"The smartest man in the room is not always right." -Richard Holbrooke

[ Parent ]

• ##### Well, the chart is of the Earths Lagrange points (4+ / 0-)

L1 is always between the body that is orbiting and the primary it orbits around. L2 is always opposite that on the outside of the orbit of the body circling the primary.

So the Moon would have an L1 point between it and the Earth and a L2 point outside its orbit.

Getting Democrats together and keeping them that way is like herding cats that are high on meth, through L.A., during an earthquake, in the rain -6.25, -6.10

[ Parent ]

• ##### The diary is garbled(0+ / 0-)

Lagrangian points exist in relation to two bodies. L1, L2 and L3 are relative to earth/sun, L4 and L5 to moon/earth.

• ##### Sorry, just reviewed the graphic(4+ / 0-)

Those are all earth/sun, it seems.

• ##### They are, there are also ones for the Earth/Moon(3+ / 0-)
Recommended by:
AndyT, Demi Moaned, Bill White

pair, but I don't have a diagram for them.

Getting Democrats together and keeping them that way is like herding cats that are high on meth, through L.A., during an earthquake, in the rain -6.25, -6.10

[ Parent ]

• ##### Have your pick, there is a genric one on the right(1+ / 0-)
Recommended by:
Something the Dog Said

FDR 9-23-33, "If we cannot do this one way, we will do it another way. But do it we will.

[ Parent ]

• ##### Thang-Q! eom (0+ / 0-)

Getting Democrats together and keeping them that way is like herding cats that are high on meth, through L.A., during an earthquake, in the rain -6.25, -6.10

[ Parent ]

• ##### This describes the E/M L2 for Webb scope(1+ / 0-)
Recommended by:
Something the Dog Said

FDR 9-23-33, "If we cannot do this one way, we will do it another way. But do it we will.

[ Parent ]

• ##### Actually, there are five L points for(5+ / 0-)

each two body system.

To identify these locations, many people label the bigger body 1st and the smaller body 2nd as in

Earth Moon Lagrange point 1 = EML1 which is located between the Earth and Moon.

or

Sun Earth Lagrange point 2 = SEL2 which is located further from the Sun than the Earth as shown in the image contained in the diary.

EML points are primarily controlled by gravitational interactions between Earth and Moon. SEL points are primarily controlled by gravitational interactions between Sun and Earth.

Sun Venus Lagrange points would be SVL1, etc . . .

Sun Mars Lagrange points would be SML1, etc . . .

= = = = =

What is way way cool is that travel between various L points (EML to SML for example) can be accomplished with very little fuel if you are willing to allow sufficient time.

See Interplanetary Transport Network

http://en.wikipedia.org/...

Using this network, it is possible that life evolved first on Mars and was carried here by asteroid fragments ejected from Mars after a massive meteorite strike on Mars.

• ##### Whew, thank you(3+ / 0-)

My understanding is that the smaller moon was in the same orbit as the larger moon. the daughter moon was drawn to the larger moon.

One issue I see, is why wasnt the daughter moon caught by the Earth Moon L4 or L5? Vs being drawn to the Larger Moon.

FDR 9-23-33, "If we cannot do this one way, we will do it another way. But do it we will.

[ Parent ]

• ##### Could be the sun's(0+ / 0-)

gravity happened to wiggle it to instead of fro.

--

Republicans chap my ass

Me

[ Parent ]

• ##### At 600 miles across it likely had the mass(0+ / 0-)

and momentum to pass L4.

FDR 9-23-33, "If we cannot do this one way, we will do it another way. But do it we will.

[ Parent ]

• ##### Lagrange point geometry is complex(3+ / 0-)

but way way cool and if we humans ever get off this rock, using the leverage this geometry offers will make human space exploration and settlement very much easier.

Robert Heinlein famously said low Earth orbit is halfway to anywhere, however,

EML1 is 80%+ of the way to anywhere

• ##### L1 and L2 because they are easy to get in(2+ / 0-)

and out of....are close to LEO...... L4 and L5 good for Large constructs, they are more likely to stay put.

So we put gas stations at L1 and L2, Hotels  at L4 and L5?

FDR 9-23-33, "If we cannot do this one way, we will do it another way. But do it we will.

[ Parent ]

• ##### Maybe we ought to put some telescopes there (2+ / 0-)
Recommended by:
Roger Fox, zett

first. After all anything we want at L4 or L5 we have to take there ourselves. They did find a pretty small asteroid at L4 recently but it is the very first we've ever found.

Getting Democrats together and keeping them that way is like herding cats that are high on meth, through L.A., during an earthquake, in the rain -6.25, -6.10

[ Parent ]

• ##### Where was the Webb scope supposed to be?(0+ / 0-)

FDR 9-23-33, "If we cannot do this one way, we will do it another way. But do it we will.

[ Parent ]

• ##### IIRC it is supposed to be parked at L5(0+ / 0-)

but I'd have to look it up to be sure. It is a great place for a telescope, but we better not have to fix it like Hubble. We don't have anything (and that includes the Russians) that can go out there and come back with humans aboard.

We could send some kind of ROV but it would have to be special built and launched.

Getting Democrats together and keeping them that way is like herding cats that are high on meth, through L.A., during an earthquake, in the rain -6.25, -6.10

[ Parent ]

• ##### In back of Earth(1+ / 0-)
Recommended by:
Something the Dog Said

FDR 9-23-33, "If we cannot do this one way, we will do it another way. But do it we will.

[ Parent ]

• ##### Yeah but now that I think about it (0+ / 0-)

it should be L2 not L5, much closer. But still hard to get to if you need to fix it.

Getting Democrats together and keeping them that way is like herding cats that are high on meth, through L.A., during an earthquake, in the rain -6.25, -6.10

[ Parent ]

• ##### Bill White found it below(1+ / 0-)
Recommended by:
Something the Dog Said

FDR 9-23-33, "If we cannot do this one way, we will do it another way. But do it we will.

[ Parent ]

• ##### I like the Gravity Lens scope idea at 550 AU(1+ / 0-)
Recommended by:
Something the Dog Said

FDR 9-23-33, "If we cannot do this one way, we will do it another way. But do it we will.

[ Parent ]

• ##### Yes, gas stations at EML1 & EML2(1+ / 0-)
Recommended by:
Roger Fox

And in terms of energy needed, if we start from EML2, Mars is surprisingly close.

In my opinion, while EML4 & EML5 are stable, they aren't really on the way to or from anywhere and therefore I don;t see much point in sending stuff there.

SEL2 is an awesome place for a telescope because the Earth can be used to eclipse the Sun allowing observations without solar interference.

= = =

As for EML1 space station here is an old Daily Kos diary of mine:

http://www.dailykos.com/...

• ##### Where was the Webb supposed to go?(0+ / 0-)

S/E L2 ?

FDR 9-23-33, "If we cannot do this one way, we will do it another way. But do it we will.

[ Parent ]

• ##### Wikipedia says: "Yes"(2+ / 0-)
The JWST will orbit the Sun approximately 1,500,000 kilometres (930,000 mi) beyond the Earth at the L2 Lagrange point. Objects at the L2 point orbit the Sun in synchrony with the Earth, which allows the JWST to use one radiation shield, positioned between the telescope and the Sun, to protect it from the Sun's heat and light (and a small amount of additional infrared from the Earth, also). The telescope will be in a very large 800,000 kilometres (500,000 mi) radius halo orbit around L2, and so will avoid any part of Earth's shadow.[Note 1] From the JWST's position, the Earth will be very close to the Sun's position but not eclipse it, while the Moon will show a tiny crescent phase during its maximum angular distance from the Sun
• ##### JPG Describes an L2 halo orbit(1+ / 0-)
Recommended by:
Bill White

FDR 9-23-33, "If we cannot do this one way, we will do it another way. But do it we will.

[ Parent ]

• ##### Thanks for that image(1+ / 0-)
Recommended by:
Roger Fox

I have been looking for something like that for quite a while.

• ##### Yeah, looking at it, it clicked for me.(1+ / 0-)
Recommended by:
Bill White

The plain of the orbit means an object @ L2 keeps the same approximate distance to the Earth and Sun. My brain went "oh yeah, I get it".

FDR 9-23-33, "If we cannot do this one way, we will do it another way. But do it we will.

[ Parent ]

• ##### Remember the 3rd stage of Apollo 13?(1+ / 0-)
Recommended by:
Bill White

FDR 9-23-33, "If we cannot do this one way, we will do it another way. But do it we will.

[ Parent ]

• ##### Nice depiction of a gravity assist flyby(1+ / 0-)
Recommended by:
Roger Fox
• ##### Sorry Apollo 12(0+ / 0-)

FDR 9-23-33, "If we cannot do this one way, we will do it another way. But do it we will.

[ Parent ]

• ##### Don't go fuzzy on the gravity(2+ / 0-)
Recommended by:
Bill White, Roger Fox

The objects are drawn to each other, and when Bill White refers to 'bigger' and 'smaller' he is obviously talking about mass, not volume, the convention being useful because it identifies to the center of mass of which the center of mass of both is nearer... or something like that.

• ##### IIRC Moons not iron rich(1+ / 0-)
Recommended by:
Something the Dog Said

This theory say that the daughter Moon formed by L3 100,000 yrs before the collision, and passed or bumped over L4 to collide.

So we have 2 bodies that are not on the densest end of the chart and the daughter had the momentum to pass thru L4. I just find that interesting because of the Trojans. Of course there is an upper limit for Trojan collection, and the daughter would have had to exceed that upper limit or it would have collected itself in L4. And at 600 miles across !

FDR 9-23-33, "If we cannot do this one way, we will do it another way. But do it we will.

[ Parent ]

• ##### Didn't Luna also pass through(0+ / 0-)

the E('Daughter moon')L5?

• ##### Larger body dominates.(0+ / 0-)

FDR 9-23-33, "If we cannot do this one way, we will do it another way. But do it we will.

[ Parent ]

• ##### The graphic shows no Earth/Moon(3+ / 0-)

Lagrange points.

Plus L1 and L2 points generally dont collect things, L4 and L5 do.

FDR 9-23-33, "If we cannot do this one way, we will do it another way. But do it we will.

[ Parent ]

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