Importance of a moon to motivating spaceflight - Really necessary?

Phobos · 2002-10-08 22:10:15

There seems to be a popular idea out there that spacefaring civilizations are rare because planets that harbor life, like Earth, aren't very likely to have large moons. The proponents of the idea seem to think that the moon was the motivating factor that got us into space somehow. I don't buy it, space is immensely useful even if you don't have a moon and I think any civilization capable of spaceflight would realize that. And most of the early rocket/space pioneers like Von Braun, Goddard, Korolev, etc, seemed to have as much interest in sending people to Mars as they did the moon from everything I've read. So who knows, if we didn't have a moon, maybe the USA and USSR would have competed to see who could get to Mars first instead. Yeah I know, I'm in a strange mental state tonight.

nebob2 · 2002-10-08 22:42:11

Who knows, without the moon we may not even have intelligent life on Earth. The moon allowed wide tides early in Earth's history, providing a requirement for life to start developing the ability to survive on dry land. The moon also stablizes the Earth's axil tilt, preventing the planet from wobbling as bad as Mars. And who knows what effect the event which created the moon had on Earth's development. The planet was not always a haven for life, life turned it into one.

Palomar · 2002-10-09 15:27:52

There seems to be a popular idea out there that spacefaring civilizations are rare because planets that harbor life, like Earth, aren't very likely to have large moons. The proponents of the idea seem to think that the moon was the motivating factor that got us into space somehow. I don't buy it, space is immensely useful even if you don't have a moon and I think any civilization capable of spaceflight would realize that. And most of the early rocket/space pioneers like Von Braun, Goddard, Korolev, etc, seemed to have as much interest in sending people to Mars as they did the moon from everything I've read. So who knows, if we didn't have a moon, maybe the USA and USSR would have competed to see who could get to Mars first instead. Yeah I know, I'm in a strange mental state tonight.

*I disagree as well. The concept that *only* a large satellite orbiting a planet would and could engender the idea and desire for space exploration is so childishly simple that it's laughable.

--Cindy

Josh Cryer · 2002-10-10 03:40:24

The only reason I invoke the moon in a discussion about intelligent alien life, is for one reason: The moon keeps Earth's core molten, and the Earth's molten core is what creates our magnetic field.

It's that simple.

I have yet to see anyone suggest that the moons are supposed to be ?inspirational? to aliens. It's silly.

The fact is, we've understood the physics necessary to get into space long before we were able to go there. If anything really compelled us to go, it's war, since war did help us build lots of neat rockets. But I suspect even peacful civilizations would curiously try to travel to the beyonds.

Phobos · 2002-10-10 20:35:58

I have yet to see anyone suggest that the moons are supposed to be ?inspirational? to aliens. It's silly.

I've seen it or I wouldn't have brought it up. Some "rare-Earth" advocates sometimes make the argument that a civilization won't have a desire to spread into space if there's no easily reachable target for them to look to, and they use the Moon as an example.

Who knows, without the moon we may not even have intelligent life on Earth. The moon allowed wide tides early in Earth's history, providing a requirement for life to start developing the ability to survive on dry land. The moon also stablizes the Earth's axil tilt, preventing the planet from wobbling as bad as Mars. And who knows what effect the event which created the moon had on Earth's development. The planet was not always a haven for life, life turned it into one.

Your arguments kind of kills the panspermia theory that defends the notion that life was likely deposited on Earth from an extraterrestrial source. Personally, it just seems more likely that Earth life first became life on Earth, but I could be wrong. After all it is a little fishy why some bacteria have developed the ability to thrive in environments bombarded with ungodly amounts of radiation unless they had to survive unprotected in space somehow. So I guess it's fairly probably life could have arose on this planet either natively or not.

Shaun Barrett · 2002-10-10 21:14:57

Josh, Oct 10, 2002:-

The only reason I invoke the moon in a discussion about intelligent alien life, is for one reason: The moon keeps Earth's core molten, and the Earth's molten core is what creates our magnetic field.
It's that simple.

I think I know what you mean about the Moon keeping Earth's core molten. You're invoking the tidal effect which you're suggesting is flexing Earth's structure and generating the heat necessary to keep the core liquid. Am I right?
If this is the case, I'm not sure you're correct.
In all the stuff I've read about Earth's internal heat, I don't remember tidal flexing being considered a major contributor. Naturally, tidal flexing must have some effect, but my impression is that it's very small in comparison to the accepted source of most of the heat, radioactive decay.
Of course, I could easily be missing something here. And I'm ready to be proven wrong.
Another possible 'fly in the ointment' is the recently postulated hypothesis that planets commonly have cores of uranium undergoing fission. The originator of this hypothesis, J. Marvin Herndon, maintains that Earth started with a ball of uranium 8 miles wide, and now has a ball 5 miles wide. He has theorised that ongoing fission in such a core would be sufficient to explain all the volcanism over the past 4.5 billion years, and can even account for the global magnetic field.

To further complicate the issue, we have the planet Mercury. Mercury has a very respectable internally-generated magnetic field.
Current theory, as you indicated, cites a molten core in a RAPIDLY ROTATING planetary body as the source of a global field. Mercury is a very small planet and its heat of formation must have long ago dissipated. The conventional radioactive decay model for internal heat production, in a planet of such small volume, predicts that that source of heat must also be largely exhausted. In addition, Mercury has no moon.
Thus every model for internal heat production, including the tidal model (but excluding the uranium core model), fails to endow Mercury with a molten core.
And, as we all know, Mercury rotates very slowly, thus driving one more nail into the coffin of the conventional hypothesis for global magnetic field production! According to our present understanding of planetary magnetic fields, Mercury shouldn't have one. But it does!!

All I'm saying here Josh, (apart from touting Herndon's new hypothesis of planetary reactor cores, which I think deserves further serious consideration) is that in the current confusion about planetary magnetic fields, it's a brave man or woman who dogmatically commits him/herself to a particular viewpoint.

Josh Cryer · 2002-10-12 06:06:38

Hmm, well, why doesn't this phenomena occur on Venus or Mars? It's common sense that heavier metals will sink to the core, so there really is no argument against uranium being there. But by the same token, there is no argument against uranium being inside the core of Venus or Mars. If anything, the assumption should be that there is.

Now that I've agree that uranium is probably in the core, I don't think it's enough to keep it molten; I think gravity alone is enough to do that. We're talking a whole lot of pressure down there in the core. From what I've read, this fission uranium would be like firecrackers in a hot oil vat, going off every now and then, nothing like the process in fission reactors. It would definitely add to the total energy inside the planet, but this doesn't explain why we don't observe magnetic fields elsewhere.

Something else has to be going on here. I suspect tidal forces from the moon play a larger roal than you think. Ocean floors raise by a few milimeters, and indeed, the whole planet physically squishes in and out due to the pull of the moon and sun. I think this is enough to get the internal dynamo going, inertia and basic fluid dynamics would keep everything spining nicely. The internal dynamo is responsible for the magnetic field; tidal forces would explain why we don't observe a magnetic field over Venus or Mars (Mars could have depleated its uranium by now, but Venus?) . Mecury is an exception, because of its proximity to the Sun. It's like a big piece of metal suspended next to an even bigger magnet. So it's going to be magnetized, at least, this is my understanding of it.

It would be very interesting if we proved that Earth was the only planet with an active uranium fission reactor in it, that Venus never had one, and that Mars had one for a very short while. But I don't think we're going to find that. The evidence just isn't there. At least not yet.

nebob2 · 2002-10-12 11:27:22

What about Jupiter's solid hydrogen core? Jupier has no moons of consequence to enact tidal forces, and is far less effected than Earth by the Sun's own forces. Yet it has a massive magnetic field. Just as the Earth's crust relies on plate techtonics, and Mars' doesn't, planet's geologic process are not always the same. Venus' core might not remain as liquid as Earth's beacuse the two act entirely different. Without analysis of the layout of Venus' interior, we can't tell.

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#1 2002-10-08 22:10:15

Re: Importance of a moon to motivating spaceflight - Really necessary?

#2 2002-10-08 22:42:11

Re: Importance of a moon to motivating spaceflight - Really necessary?

#3 2002-10-09 15:27:52

Re: Importance of a moon to motivating spaceflight - Really necessary?

#4 2002-10-10 03:40:24

Re: Importance of a moon to motivating spaceflight - Really necessary?

#5 2002-10-10 20:35:58

Re: Importance of a moon to motivating spaceflight - Really necessary?

#6 2002-10-10 21:14:57

Re: Importance of a moon to motivating spaceflight - Really necessary?

#7 2002-10-12 06:06:38

Re: Importance of a moon to motivating spaceflight - Really necessary?

#8 2002-10-12 11:27:22

Re: Importance of a moon to motivating spaceflight - Really necessary?

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