Moon's Rotation Post-Breakaway

[tx4]

Greetings. I was recently referred to this forum, and besides it looking like an interesting forum, the referrer indicated one of my unanswered questions in another forum might get some responses here.

In Earth orbit, the Moon turns/turned -- funny, I don't know which tense to use in the context of /Space: 1999/ -- once on its axis every 27.321 days, this being the "sidereal period." (I am thus not referring to the more familiar new-moon-to-new-moon synodic period, which would not have any stable meaning out of an orbit of some sort.)

I have two distinct situations to ask about....

1) Breakaway. Assume two things:

* The Moon survived Breakaway (or this would be a pointless question about a very brief TV series!); and

* The Breakaway explosion at Area Two, once it progressed beyond the initial individual explosions to full scale critical, blew outwardly evenly, deflected and concentrated only by the lunar surface or whatever passes for bedrock on the Moon.

Would the Breakaway explosion, in moving the Moon into high velocity away from Earth, have imparted or removed any rotational momentum, increasing or decreasing the Moon's rotation rate / sidereal period at all? If so, would it have been negligible, or could it have been of minutes or even more?

2) "Near" approaches to other planets. Would a fly-by, on either side of a planet, made any significant change to the Moon's rotation? Though most lunar flybys were at moderate distances, some were close. If there would be any effect at all, would it be different if the Moon flew by the planet's leading side vs. its trailing side?


For both questions, I am just asking for general thoughts on potential (speculative) scale, such as nothing vs. negligible vs. seconds or minutes or more. I say this because I realize this, especially Q#1, is tricky ground (science fiction / whatever suspension of disbelief is needed / etc.) for physics at best. Still, I am wondering if anyone has any thoughts.

Thanks!

[cricket]

Welcome! Glad you made it. I anticipate hypotheses falling from the stars at any point now...

(yo, CR! )

[Howard]

One word.
Asimov.

[Bishop]

Welcome tx4. Another question you could ask is what effect does the moon have on planets it passes by, particularly those it passes closest too?

Good questions.

[CR]

Huh? Some tech-geeky-astronomy-sci-fi-something or other to try to justify the 'reality' of Space: 1999? OK, I'm here!

But first: Asimov's famous blasting of the series premise has been so over-used (especially by Star Trek fans), that I've grown to ignore it whenever it's invoked. (Nothing personal, Howard; just stating a point.) Also, I believe selection bias plays a strong part in the whole Asimov thing, since he also said (I'm going to have to paraphrase here) that in spite of its shortcomings, Space: 1999 was one of the few new sf programs on tv, and as such was worth a look. I wish I could remember where I'd read that so that I could let you all see what he actually said (great for the next 'debate' wherein a Star Trek fan wants to shore up his/her anti-S99 rant by invoking Asimov)... it may have been in John Kenneth Muir's book, Exploring Space: 1999.
Commander Eagle, look away for a sec or two.. OK, now that he's not paying attention, for the record, I'm not anti-Star Trek. OK, Sir, you can look back again now! I'm against Star Trek fans who exhibit a superiority complex over anything non-Star Trek.
All right, enough ranting/politicising... on with the rotational stuff...

I'm just going to throw some factoids out here. I touched on some of this ages ago on another thread somewhere at this forum; I'll state now what I did then: these facts as they apply to the moon's travels in Space: 1999 are simplified for the sake of making the story work. Real physics is a lot more complex (yet sublime, too) than what our 'common sense' for the sake of storytelling would have us believe. So...

The moon is tidally locked with Earth; in other words, the same side of the moon faces Earth, which is why we only see the same face (what we call the Nearside). There is slight precession (wobble) of the moon that allows us to see just a little bit more or less of either limb (edge) of the moon as viewed from Earth, but for all practical purposes, the Nearside always faces toward Earth.
Part of the reason for this (and I'm going strictly from memory here, though I've got enough books that I should look it up to confirm) has to do with the density of the moon itself; if I recall correctly, the denser part faces Earth. Conversely, the crust of the moon isn't even, with the thicker part of the lunar crust mostly comprising the Farside; hence, the Farside has lots of craters, but very few--and very small-- maria, or lava plains. The Nearside, with its thinner crust, is covered with maria, which have burried many of the Nearside's oldest craters. (Of course, that's the current theory; going back to the moon with much more extensive geologic surveys will allow confirmation or refutation of that idea.)
So what?
Well, perhaps the density of the wandering moon itself, as it passes other planets, causes the same face to 'gravitate' toward a planet. Hence, as we see in episodes, the moon looks similar to its pre-Breakaaway appearance when viewed from a planet's surface. (I know, the real reason is because the sfx gang used the same photo cut-out each time... I'm talking about reality here. Um, you know what I mean.)
Would the moon passing by a planet affect that planet's rotation? You bet, as well as that planet's orbital path around its sun, if the moon got too close. Ultimately, the orbital path might correct itself after the moon's passing, but the planet's rotation rate and axial tilt might be skewed pretty badly for a long time.
For that matter, Earth would have been knocked askew by the moon's Breakaway. Not only would Earth's rotation rate increase slightly (the moon's presence slows it down a bit), the axis might have gotten jarred, enhancing the precession that currently takes centuries to have noticable change. "Another Time, Another Place" sort of dealt with this by having Earth's axial tilt changed by five or six degrees, but the writers kept Earth's rotation unchanged. Oops! Or maybe not 'oops', since the duplicate moon had been in orbit around Earth for five years, and had slowed Earth's rotation back to its pre-Breakaway rate. Hmm...
Back to the Breakaway for a sec... NDA2 must have been on the moon's trailing side (relative to the moon's orbital direction around Earth) in order to push it away from Earth. Had it been on the middle of the lunar Farside directly opposite Earth, it more likely would have pushed the moon toward Earth (though not necessarily on a collision course, due to the moon's orbital velocity). Had NDA2 been on the leading edge as seen from Earth, it would have slowed the moon's orbit, possibly enough to stop it. Of course, Earth's gravity would have then pulled the moon inward, but don't worry, the Roche Limit would have torn the moon assunder before it actually collided with Earth, and instead Earth would have been pelted as if by a shotgun. Party!
As for approaching a planet's leading or trailing side (relative to its orbital direction), I guess there might be an effect. I'm way too tired to try to figure it out at this point, and this post is already a mile too long, but one might look at the 'gravity assists' that current real-life space probes use to gain extra velocity with minimal fuel expenditure (as the probes 'slingshot' around the planet, it 'steals' a little of the planet's momentum).
Sorry for the abrupt halt to this post. I hope I've at least given enough 'food for thought' to keep readers satisfied for now, and inspired to look up the real orbital mechaincs stuff in books and on the web. Reality is more exciting than fiction, but the math is a lot harder!

[CR]

Quick follow-up:
Roche's Limit, the point where a large body in orbit around a larger body is torn apart by gravitational stress, might be overcome if the moon were moving fast enough, thus resulting in a collision. After all, current scientific thought suggests that the moon itself was created by a collision between a nearly Mars-sized proto-planet and the nascent Earth. While proto-Earth wasn't completely annihilated (obviously), a lot of it (and the colliding object) were liquified; the 'wreckage' thrown into space coalesced into what we now know as the moon.
Also, the moon was much closer to Earth in those early days, and has steadily been moving away. Perhaps in a million years, total solar eclipses will not be possible, because the moon will be too far away to completely block the sun. (Of course, in the S99 universe, the moon will be really far away!)

[tx4]

CR and all, thank you for the replies!

Isaac Asimov is one of my long-time favorite authors, for both his science and science fiction. I like Asimov's technical yet clear way of writing, in his various works. Yet I really like S19 as well, so I just never had much concern about his article (S19 being science fiction and all). I think I have Asimov's article somewhere too, CR, but not very handy either.

It wasn't Asimov (I don't think), but someone else (a television reviewer perhaps) who argued that if the dumps on the far side blew, then why didn't the Moon just hit Cleveland (I don't know why Cleveland; maybe it was a TV reviewer from Ohio). I posted a counter-argument to that in another forum some years back, on the simple basis that the "far side" is a full half the Moon, and there is actually a lot of space between us and the Moon's current orbit.

I had no idea that part of the Moon's tidal lock is due to the near side being denser; and though aware that the vast majority of the maria are on the near side, had not known it is probably because the crust is apparently thinner there (though it does make sense, with the maria's its apparent molten origin).

I always wondered about the Roche Limit in regard to "Collision Course," but was never sure (from a real physics perspective) whether the Roche Limit is implied for *any* approach or refers more to medium to large satellites not being to form within the Roche Limit or cracking up if their orbit slowly degrades to the point it enters within the Roche Limit and is broken up (isn't that one of the theories for planetary rings?).

There was sort of a different case of the Roche Limit, maybe, in "New Adam New Eve," where the planet Magus was on ("New Earth" he called it) was so unstable he was having to hold it together against the Moon's gravity -- though that may not be a proper application of the term Roche Limit, on my part (the episode itself did not refer to such, I am pretty sure).

Your discussion, CR, about how close approaches (or departures) could radically alter axial tilts and rotation rates was very helpful.

Thank you.

[CR]

You're welcome!
Just a reminder, I may be wrong about the moon's density having to due with it being tidally locked; I've been unable to get to my materials that would confirm or deny this, and since many of the books I own are at least a couple years old (if not older!), an internet search might be more helpful! Even if I'm wrong according to real-life physics, it makes for an interesting sci-fi explanation for the moon's appearance in the show.

Oh, and yes, the Roche Limit has a relation to planetary rings... forgot to mention that. Saturn's ring system, for example, is believed to have formed when an icy moon broke apart eons ago, and the debris has slowly been grinding down to smaller & smaller pieces. Larger chunks known as Shepherd Moons help keep the rings in shape, though their gravity makes for interesting wave-like patterns along the fringes of the rings as they pass.
Interestingly, we just recently discovered that the moon Enceladus has icy guysers which actually add material to the rings. Check out the Cassini imaging site for updates and a spectacular collection of images sent back by the Cassini Probe currently orbiting Saturn: http://ciclops.org/index.php?flash=1&js=1

[john_trek]

When discussing Space:1999 you either have to :
- completely throw out physics
- place our heros in a slightly different universe with a couple minor physical law differences.

I usually take the second option, because I really hate completely throwing away all sense of reality (even if a few memorable episodes like "Ring Around the Moon" did it).

Rotation Rate: Very good question.
Nobody ever brings it up, but the explosion (or series or explosions, or nuclear fusion rocket motor formerly known as NWD-2) would have probably imparted at least some new rotational energy to the moon. Basically, unless the thrust was precisely pointed through the exact center of the moon, there would have been at least some lateral push on the moon. So even if 99.99 percent of the energy went to pushing the moon out of orbit, the rest of the rather considerable ammount of thrust would have changed the moons rotation in some way.
If the nuclear waste dumps were located precisely on the lunar equator, and the sideways thrust was coincidentally aligned either due west, or due east, then the rotation rate of the moon would have either speeded up or slowed down. If none of those conditions were true, then the moon would have started to do a slow tumble.
So... since a slow tumble is rather annoying visually on the screen, it's best to just accept the rather unplausable coincidence that every planet the moon passed by just happened to be visible just above the lunar horizon from where Moonbase Alpha was located (and never seemed to move from that spot during the next few days).

As for my theory that we "place them in a slightly different universe" .... I prefer to think that the Earth that our Alphans live on is in a universe where the stars are all only a few light days apart, instead of light years. And there are somewhat fewer of them, so the night sky is not just ablaze with stars. This gets around the whole "how did they get to the next solar system so soon after last week's episode?" problem.

The "how did they happen to pass so close to the planets?" problem is a litttle tricker. It's those darn special effects people... they made the planets look bigger on screen so you could see them on the small TV set screens. Usually the Eagles had to set out on missions where the planet was perhaps ten times furthur away than the Earth-Moon distance.

Then, we have the "even if the explosions were powerful enough, why didn't parts of the moon (especially all the loose soil and rocks) just fall off during the roughly 10 gravity acceleration rate away from the Earth? "

Or: "Howcome the Alphans couldn't escape back to Earth in the first few hours after the disaster, but every time they encounter a new planet they are in Eagle flight range for several days?"

So.... best to just watch the show for the nice model work, and interesting metaphysical plot lines (series 1) or if you must, the scary rubber monster suits (series II ).

[CR]

Good points, john_trek! But I especially liked how you summed it all up:

Originally Posted by john_trek

So.... best to just watch the show for the nice model work, and interesting metaphysical plot lines (series 1) or if you must, the scary rubber monster suits (series II ).

[tx4]

Thanks again for the continued feedback. It has been very thought-provoking. I am also starting to realize I may have neglected to include a little extra context for my questions....

I guess I take Space: 1999 in two different ways when it comes to these sort of astronomical/physics points, depending on whether I am watching it or writing. I think I agree with everyone about the points in regard to what we see on the screen is often conveniently (and probably in some cases intentionally) simplified; but when I write, I do like to invoke in some places the vastness of real space, the immense distance between stars, that the Moon is not always going to turn the same face to planets, that the Moon may not always approach closely, sometimes hardly close at all, and other such cases.

At the same time, there is still the *fiction* side of science fiction too, occasionally mixing in plenty of familiar or occasionally unfamiliar science fictional terminology where "necessary" (trying not to devolve into the problems inherent in technobabble, however), to get the Moon to travel between the stars, etc.

I guess I just have something of a technical and scientific side to me that I like to use a mix of fictional and more realistic aspects, to lay down background "scenery" or some other aspects.

This was indeed a good place to ask such questions about a fictionally-wandering Moon making close approaches to alien planets (and suffering a "Breakaway" explosion that was still highly fictional, even if I do wish to *partially* mix in a little in the way of "real" practical effects too).

The responses have all been helpful, and appreciated, and have given me some things to look further into. Thanks again!

[tx4]

(Forgot something....)

Speaking of mixing science and fiction, I stumbled on this when doing a web search today. Maybe it is a familiar link to everyone else, but as it is also somewhat timely (topic and day), I'll post it, in case anyone is interested:

http://home.swipnet.se/moonbasealpha...imulation.html

[cricket]

Cool!

[tx4]

Cricket,

Since I noticed you posted this a few minutes ago and are right now at 1500 posts, let me be the first to congratulate you on your promotion from Communications Officer to Life Support Officer.

[cricket]

Huh , and so I am. Well, now, thanks!

(Still holding out for the CMO spot, though )

[Bishop]

Aren't we all, not long to go Cricket.... but don't you already have that post

[cricket]

Originally Posted by Tony42

Aren't we all, not long to go Cricket.... but don't you already have that post

Nope, just a contented cog inside a giant wheel. That's why I gotta dream big!

[DX-SFX]

Some of the physics problems were addressed in Earthfall, the expanded novelisation of Breakaway. Bergman postulates that the huge titanic forces of the explosion momentarily caused a rift removing the Moon from real space where it had no mass thus allowing it to be set in motion without being destroyed in the process. OK, it's hokey but at least the problem wasn't ignored.

[stargazer]

Originally Posted by john_trek

When discussing Space:1999 you either have to :
- completely throw out physics
- place our heros in a slightly different universe with a couple minor physical law differences.

I usually take the second option, because I really hate completely throwing away all sense of reality (even if a few memorable episodes like "Ring Around the Moon" did it).

Rotation Rate: Very good question.
Nobody ever brings it up, but the explosion (or series or explosions, or nuclear fusion rocket motor formerly known as NWD-2) would have probably imparted at least some new rotational energy to the moon. Basically, unless the thrust was precisely pointed through the exact center of the moon, there would have been at least some lateral push on the moon. So even if 99.99 percent of the energy went to pushing the moon out of orbit, the rest of the rather considerable ammount of thrust would have changed the moons rotation in some way.
If the nuclear waste dumps were located precisely on the lunar equator, and the sideways thrust was coincidentally aligned either due west, or due east, then the rotation rate of the moon would have either speeded up or slowed down. If none of those conditions were true, then the moon would have started to do a slow tumble.
So... since a slow tumble is rather annoying visually on the screen, it's best to just accept the rather unplausable coincidence that every planet the moon passed by just happened to be visible just above the lunar horizon from where Moonbase Alpha was located (and never seemed to move from that spot during the next few days).

As for my theory that we "place them in a slightly different universe" .... I prefer to think that the Earth that our Alphans live on is in a universe where the stars are all only a few light days apart, instead of light years. And there are somewhat fewer of them, so the night sky is not just ablaze with stars. This gets around the whole "how did they get to the next solar system so soon after last week's episode?" problem.

The "how did they happen to pass so close to the planets?" problem is a litttle tricker. It's those darn special effects people... they made the planets look bigger on screen so you could see them on the small TV set screens. Usually the Eagles had to set out on missions where the planet was perhaps ten times furthur away than the Earth-Moon distance.

Then, we have the "even if the explosions were powerful enough, why didn't parts of the moon (especially all the loose soil and rocks) just fall off during the roughly 10 gravity acceleration rate away from the Earth? "

Or: "Howcome the Alphans couldn't escape back to Earth in the first few hours after the disaster, but every time they encounter a new planet they are in Eagle flight range for several days?"

So.... best to just watch the show for the nice model work, and interesting metaphysical plot lines (series 1) or if you must, the scary rubber monster suits (series II ).

1999 is for sure one of those deals where you have to 'suspend disbelief' to watch it (I have to anyway) Fact is the moon could not be moved from its orbit by an explosion or anything else. Anything large enough to 'move it' would shatter it.

Just enjoy 1999 for what it is.

[cmdrkoenig67]

Originally Posted by tx4

CR and all, thank you for the replies!

Isaac Asimov is one of my long-time favorite authors, for both his science and science fiction. I like Asimov's technical yet clear way of writing, in his various works. Yet I really like S19 as well, so I just never had much concern about his article (S19 being science fiction and all). I think I have Asimov's article somewhere too, CR, but not very handy either.

It wasn't Asimov (I don't think), but someone else (a television reviewer perhaps) who argued that if the dumps on the far side blew, then why didn't the Moon just hit Cleveland (I don't know why Cleveland; maybe it was a TV reviewer from Ohio). I posted a counter-argument to that in another forum some years back, on the simple basis that the "far side" is a full half the Moon, and there is actually a lot of space between us and the Moon's current orbit.

That other person you mentioned may have been Harlan Ellison, he had said that any explosion on the far side would have sent the moon crashing down on the Earth.

Neither he nor Mr. Asimov take into account the MUF (Mysterious Unknown Force), that was a very important plot-point during the first Year of Space:1999. Several episodes of Year one postulated that something they couldn't understand was protecting them and guiding them...Surely any force that may have been protecting them, wouldn't let the moon be blasted to dust in the initial breakaway explosion.

Dana