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telford
11-10-2010, 12:41 PM
I'm in over my head with the tech stuff and hope that someone can help me out with this problem. So, in the book there is a solar system with one planetary body apart from the primary. It is hugh and habitable. The other planets in the system have been pulverised (don't ask how) and have been attracted to the planet, causing it to be surrounded by a massive asteroid field. So here's the problem. If the planet is habitable to humans then it would have to be within one AU of the strongest graviational field (the primary) in the system. I can go down the track of writer's bs but if anyone could think of a way of justifying this I would be grateful to hear from you.

Lhun
11-10-2010, 04:34 PM
If you're going to write in that asteroid field, don't worry about the small stuff.

To be inhabitable by humans, a planets needs to have about 1g of gravity, i.e. same mass as earth, and about the temperature (well, and water, oxygen and other such details). Temperature is not determined by distance to the star alone, what matter is how much light per mē hits the planet. If the star is twice as bright as the sun, the planet would get the same amount of light at 1,4 AU. (inverse square law)
For that matter, you can vary the orbit of the earth quite a bit (at least by a third in either direction) and still have it inhabitable, at least partly, by humans.

Kenn
11-10-2010, 04:37 PM
I don't really know what you are after. But here are a few points. If the planet is in an asteroid belt, then a possible explanation might be that the belt was formed by the disintegration of a Trojan planet at the Lagrangian point on the opposite side of the star. Since no Trojan planets are known, it is a long shot and it would be an unstable system anyhow. It seems unlikely that the planet would attract the asteroids from other orbits (in the same way that the asteroid belt in our Solar System has not formed a cloud around Jupiter).

There is no reason for the planet to be 1 AU away from its sun. You could just alter the size of the star to make the planet habitable.

If the planet is huge, then gravity might be a problem. One way around that might be to make it spin very quickly on its axis.

LBlankenship
11-10-2010, 05:00 PM
The other planets in the system have been pulverised (don't ask how) and have been attracted to the planet, causing it to be surrounded by a massive asteroid field. So here's the problem. If the planet is habitable to humans then it would have to be within one AU of the strongest graviational field (the primary) in the system.

Is the habitable planet orbiting the star or the gravity sink? are we talking about a habitable moon of some gas giant?

Plus, putting a planet in the middle of an asteroid field would tend to mean a lot of asteroids hitting your planet, it seems to me. That tends to be rough on the living things on it...

Hallen
11-10-2010, 08:43 PM
Is the habitable planet orbiting the star or the gravity sink? are we talking about a habitable moon of some gas giant?

Plus, putting a planet in the middle of an asteroid field would tend to mean a lot of asteroids hitting your planet, it seems to me. That tends to be rough on the living things on it...

The reason for having asteroids all around the planet escapes me. And I think Carlavii is correct in that if there were, the planet would be hit on a pretty regular basis.

However, if the planet previously had multiple moons, and those moons collided recently, then you might get asteroids around the entire planet. Eventually, you'll just have rings like Saturn though.

I don't think you can make the planet "really big" though. The bigger it is, the less dense it can be to maintain something close to 1g. The less dense it is, the more trouble it will have holding onto things in orbit and obviously, the less chance of having any kind of solid surface.

PeterL
11-10-2010, 10:48 PM
Unless you have a really, really good reaason for having the planet as you mentioned, huge and surrounded by asteroids, then you should drop those. A huge planet would either have a high mass that would lead to more gravity than humans could stand, or it would be of extremely low density, so that it couldn't have a solid surface.

An ordinary rocky planet of roughly the size of Earth would be appropriate. Something that recently created a lot of rocky debris might be O.K., but only if it serves the story.

telford
11-11-2010, 09:06 AM
Hello Lhun,
Thanks for that. I see the planet as large and having a gravity of 1.6g of Earth. Yes, hard going for humans; but who said it was inhabited by humans? You make a good point about the output of the sun and your idea of placing at 1.4 au's works for me. I really appreciate you looking at this. Cheers.

telford
11-11-2010, 09:12 AM
Hello Kenn,
Thanks for taking the time. Yes, it would appear that I have written myself into a corner with this one. As I mentioned to Lhun, the gravity must be in the 1.6g range. This is science Fiction after all so I shall have to think on this a bit more and see if writing believeable bs will get me out of this. Thanks again.

telford
11-11-2010, 09:16 AM
Hello Carla the eighth,
Yes, problems becoming greater. Anyhoo, the planet is large so that I can justify the 1.6g. How to get those asteroids into position and keep them there is the problem. Thank you for taking the time.

telford
11-11-2010, 09:20 AM
Hello Hallen,
Yep, as discussed with the other crits, high gravity is not a problem. The problem is justifying something that, on the surface, cannot be. Did I mention that this planet is one of many that are encased within a region of space lock space called the Tunguska Fault. It is unlike any region of space known to exist and has very special and dangerous anomolies. Perhaps I need to use this special quality to justify this. Anyhoo, thanks for taking the time.

telford
11-11-2010, 09:24 AM
Thanks for that PeterL. Yes, as mentioned I have written myself into a corner all right. As I see the story now it is vital that this environment work. I guess that I will have to take a bit more time to think this throught. I appreciate you taking the time.

PeterL
11-11-2010, 05:41 PM
Thanks for that PeterL. Yes, as mentioned I have written myself into a corner all right. As I see the story now it is vital that this environment work. I guess that I will have to take a bit more time to think this throught. I appreciate you taking the time.

1.6g is not very large, so you don't have that much of a problem there, except that it would be very unlikely to capture all that many asteroids. You might consider giving the planet multiple moons. A dozen or two moons would knock some chunks off each other, but they would establish stable orbits fairly quickly. The debris would be swept to other orbits.

DavidZahir
11-12-2010, 05:10 AM
The universe is a really really big place. I mean REALLY big. Seems possible that somewhere or other a planet might end up with what amounts to a huge number of big rocks in stable orbits. Unlikely (very!), but it doesn't seem impossible.

Lhun
11-12-2010, 08:11 AM
The universe is a really really big place. I mean REALLY big. Seems possible that somewhere or other a planet might end up with what amounts to a huge number of big rocks in stable orbits. Unlikely (very!), but it doesn't seem impossible.It's impossible because huge amounts of rock cannot have a stable orbit. They will condense down to a single body per orbit. Even different orbits that are too close together (so close that minor alterations cause collisions) don't work.
It's the same reason you can't have asteroid fields like you see them on StarWars or nebulae like the ones on Star Trek. Gravity sucks.

telford
11-12-2010, 08:43 AM
Peter, Lhun & David,
Thanks guys for the input. Yes, by the physics we currently understand, this is an impossible situation. But in the first book I altered the laws of physics and got away with it (I think). This is, after all, a science fiction book, so perhaps a bit of latitude could be expected if I apply the bs with a very delicate brush. Thanks again guys.

Lhun
11-12-2010, 09:29 AM
Peter, Lhun & David,
Thanks guys for the input. Yes, by the physics we currently understand, this is an impossible situation. But in the first book I altered the laws of physics and got away with it (I think). This is, after all, a science fiction book, so perhaps a bit of latitude could be expected if I apply the bs with a very delicate brush. Thanks again guys.Well, maybe it works. But you need some serious physics alterations to make those asteroids work. There'd need to something that keeps those asteroids from bumping into each other, but at the same time does not prevent planets from forming. (which happens by asteroids bumping into each other)

DavidZahir
11-12-2010, 12:39 PM
Maybe I'm coming at this with a different sense of just how many rocks we're talking about here?

telford
11-12-2010, 12:58 PM
Lhun & David,
I'm open to ideas but I see a massive field formed from dozens of destroyed planets (perhaps during the ancient war 5000 years ago). A thought that jumped into my head recently was this: If the asteroids and the planet contained an element that attracted one another that would solve the first problem. Then perhaps like two magnets pushing against one another this would create a stable situation. Attraction at a distance, repulsion up close, with both scources constantly working against one another to maintain the stability. If you like you may call this element bullshitium. (just kidding guys)
Any thoughts?

Kenn
11-12-2010, 02:09 PM
It's impossible because huge amounts of rock cannot have a stable orbit. They will condense down to a single body per orbit. Even different orbits that are too close together (so close that minor alterations cause collisions) don't work.
It's the same reason you can't have asteroid fields like you see them on StarWars or nebulae like the ones on Star Trek. Gravity sucks.
Except that there is the Asteroid Belt in our own Solar System. I'm not sure what the latest theories are on its formation, but it has been proposed that it was caused by the destruction of a planet (Phaeton). There are also fields of asteroids at the Lagrangian points in Jupiter's orbit (these are stable points on the same orbit). It is possible that a planet corresponding to a Lagrangian point on the same orbit as the planet in the story created the asteroid field. This type of planet is called a Trojan planet; although none are known there are Trojan moons (orbiting Saturn).

Mac H.
11-12-2010, 03:12 PM
It's impossible because huge amounts of rock cannot have a stable orbit. They will condense down to a single body per orbit.Sure they will. But over how long?

After a few million years? Ten million?

Couldn't it just be a fairly 'young' asteroid field - with scientists guessing that it was only formed in the last 100,000 years or so - but really not sure?

Mac

Lhun
11-12-2010, 05:29 PM
Except that there is the Asteroid Belt in our own Solar System. I'm not sure what the latest theories are on its formation, but it has been proposed that it was caused by the destruction of a planet (Phaeton). There are also fields of asteroids at the Lagrangian points in Jupiter's orbit (these are stable points on the same orbit). It is possible that a planet corresponding to a Lagrangian point on the same orbit as the planet in the story created the asteroid field. This type of planet is called a Trojan planet; although none are known there are Trojan moons (orbiting Saturn).The asteroid belt in the solar system contains considerably less rock than, say, the vacuum inside a light-bulb. It's total mass is a small fraction of the moon's, and even that is concentrated mostly in few big asteroids.


Sure they will. But over how long?

After a few million years? Ten million?Well, that's a question of how many rocks there are, and how they are spread out.

Couldn't it just be a fairly 'young' asteroid field - with scientists guessing that it was only formed in the last 100,000 years or so - but really not sure?

MacThat leaves the question where all the rock came from. And even if it's just around a planet, not a whole belt, that can be a whole lot of rock. Smashing a planet or even moon into separately orbiting fragments takes an insane amount of energy, so much that it's kind of impossible that it could happen in the orbit of another planet and leave that one undisturbed.

LBlankenship
11-12-2010, 06:34 PM
Lhun & David,
I'm open to ideas but I see a massive field formed from dozens of destroyed planets (perhaps during the ancient war 5000 years ago). A thought that jumped into my head recently was this: If the asteroids and the planet contained an element that attracted one another that would solve the first problem. Then perhaps like two magnets pushing against one another this would create a stable situation. Attraction at a distance, repulsion up close, with both scources constantly working against one another to maintain the stability. If you like you may call this element bullshitium. (just kidding guys)
Any thoughts?

As Lhun mentioned, if we're talking about recently destroyed planets (and 5,000 years is recent, as these things go) then you're throwing orbital changes into the mix too. The web of interplays between the star's gravity and all of the planets tugging on each other has been broken up. Your planet's orbit could still be adjusting to the change.

Which could make for interesting situations, like a frozen planet sliding a little closer to its star and starting to thaw out...

I could be talked into the planet picking up a debris ring like Saturn's from all the mess. But yeah, if you want to put some kind of protective field around your planet to protect it from bombardment, that would be bullshitium.

Kenn
11-12-2010, 07:14 PM
The asteroid belt in the solar system contains considerably less rock than, say, the vacuum inside a light-bulb. It's total mass is a small fraction of the moon's, and even that is concentrated mostly in few big asteroids...

That is an odd comparison, since there is no rock floating around inside a light bulb.

The mass of the asteroid belt is still pretty much unknown (despite what Wikipedia might say!). Of course it has become depleted with time, thanks to Jupiter's influence, but it hasn't always been like that. You only have to look at the surface of the moon to see how much more stuff was kicking around in the past. Don't forget there are a lot of meteor strikes on earth every year also.

I imagine the asteroid fields in sci-fi films are explained as being the remnants of planets. I am not quite sure why a planet would disintegrate, or even if it could, but you can't make sweeping statements about the energy it would require. For example, you might imagine gravitational resonance could shatter a crystaline core or crust.

Lhun
11-12-2010, 07:53 PM
That is an odd comparison, since there is no rock floating around inside a light bulb.And to a similar degree of accuracy, there are no rocks floating around in the asteroid belt. It's emptier than the best man-made vacuum.

The mass of the asteroid belt is still pretty much unknown (despite what Wikipedia might say!).No it's not. We haven't found every pebble floating around there, but that's it: they're just pebbles. It doesn't really matter if we don't know the mass of the asteroid belt to the tenth decimal or only the ninth.

Of course it has become depleted with time, thanks to Jupiter's influence, but it hasn't always been like that. You only have to look at the surface of the moon to see how much more stuff was kicking around in the past. Don't forget there are a lot of meteor strikes on earth every year also.All of that is small stuff. You could scatter the whole moon across the asteroid belt and it'd still empty. Not even dense enough to see two asteroids at once.

I imagine the asteroid fields in sci-fi films are explained as being the remnants of planets. I am not quite sure why a planet would disintegrate, or even if it could, but you can't make sweeping statements about the energy it would require. For example, you might imagine gravitational resonance could shatter a crystaline core or crust.Again, gravity prevents all this. Planets can't shatter because they're not really solid anyway. The problem is that what you're used to on earth, doesn't work like that when scaled up a couple of billion times in space. A rock holds together because of intermolecular bonds, and if you break rock into pieces, they don't stick together. You can break a rock and scatter it across the ground.
But it doesn't work that way in space. Planets are for all intents and purposes just liquids, the hardness of the materials is completely irrelevant because of the forces involved. A planet isn't spherical because it's a piece of rock that just happens to be spherical, but because the pull of gravity is so strong that it simply forms a sphere. I you pick a planet made of solid rock, and crush it to dust, you still end up with a spherical pile of dust floating around. To completely scatter a planet you need to accelerate all its matter to escape velocity. Which can easily exceed the energy required to vaporize the matter. In which case you'd still end up with a spherical blob of vaporized rock.

Lhun
11-12-2010, 07:57 PM
A thought that jumped into my head recently was this: If the asteroids and the planet contained an element that attracted one another that would solve the first problem.Gravity does that anyway.

Then perhaps like two magnets pushing against one another this would create a stable situation. Attraction at a distance, repulsion up close, with both scources constantly working against one another to maintain the stability. If you like you may call this element bullshitium. (just kidding guys)
Any thoughts?The problem with scenarios like these is that they're rarely self-correcting. If the balance tips just a little, the whole system comes (metaphorically) crashing down.
But sure, magically repellent bolognium that keeps the rocks from falling on the planet and from forming a moon works. Though you should find some kind of explanation why the bolognium in the rocks keeps them from forming a single body, but the bolognium in the planet doesn't cause it to fly apart.

Kenn
11-13-2010, 12:43 AM
And to a similar degree of accuracy, there are no rocks floating around in the asteroid belt. It's emptier than the best man-made vacuum.
This doesn't make sense. Empty of what? There are obviously no rocks in your light bulb yet there clearly are in the Asteroid Belt. So how can that be to a similar degree of accuracy?


No it's not. We haven't found every pebble floating around there, but that's it: they're just pebbles. It doesn't really matter if we don't know the mass of the asteroid belt to the tenth decimal or only the ninth.
All of that is small stuff. You could scatter the whole moon across the asteroid belt and it'd still empty. Not even dense enough to see two asteroids at once.
And how exactly do you think the mass of the asteroid belt became 'known'? There have been various calculations based on various assumptions (obviously nobody has weighed it!). It is not known to the umpteenth decmal point. All of this is getting away from my original point however, which was that you said asteroid belts could not exist because of gravity. Clearly they can and they do.

Again, gravity prevents all this. Planets can't shatter because they're not really solid anyway. The problem is that what you're used to on earth, doesn't work like that when scaled up a couple of billion times in space. A rock holds together because of intermolecular bonds, and if you break rock into pieces, they don't stick together. You can break a rock and scatter it across the ground.
But it doesn't work that way in space. Planets are for all intents and purposes just liquids, the hardness of the materials is completely irrelevant because of the forces involved. A planet isn't spherical because it's a piece of rock that just happens to be spherical, but because the pull of gravity is so strong that it simply forms a sphere. I you pick a planet made of solid rock, and crush it to dust, you still end up with a spherical pile of dust floating around. To completely scatter a planet you need to accelerate all its matter to escape velocity. Which can easily exceed the energy required to vaporize the matter. In which case you'd still end up with a spherical blob of vaporized rock.
Loads of assumptions here and I don't know where to start. Firstly, nobody knows how planets were formed, so you can't say that they are rocks (or behave as liquids, as you suggest). Secondly, there is a difference between something that is hard and something that is difficult to break up. Thirdly, if an asteroid field was formed by the disintegration of a planet, then I don't see the relevance of reducing it to dust first (and if you did, then it would only remain as a spherical ball of dust if the system was perfectly symmetrical and static).

It is not inconceivable (for the purposes of science fiction at least) that a planet could cool unevenly so it contained fault lines. Then through further contraction or grativational resonance, you could see how it might break up. Of course there have been no observations of anything like that happening because we have information on only a handful of planets (and in not much detail at that). So it is all speculation. But then again, Telford is writing a plausible novel and not applying for a research grant from NASA;)

I'm open to ideas but I see a massive field formed from dozens of destroyed planets (perhaps during the ancient war 5000 years ago). A thought that jumped into my head recently was this: If the asteroids and the planet contained an element that attracted one another that would solve the first problem. Then perhaps like two magnets pushing against one another this would create a stable situation. Attraction at a distance, repulsion up close, with both scources constantly working against one another to maintain the stability. If you like you may call this element bullshitium. (just kidding guys)
Any thoughts?
What you are describing is electrostatic attraction. A positive charge being attracted to a negatively charged atmosphere (or via induced charge), but then gets repelled by a positive charge at the opposing core. Not sure if such an environment would be hospitable though!

Lhun
11-13-2010, 01:54 AM
This doesn't make sense. Empty of what? There are obviously no rocks in your light bulb yet there clearly are in the Asteroid Belt. So how can that be to a similar degree of accuracy?Because no human-made vacuum is perfect, and because the asteroid belt contains much less rock per volume than the best human-made vacuum does.

And how exactly do you think the mass of the asteroid belt became 'known'? There have been various calculations based on various assumptions (obviously nobody has weighed it!).Oh please. That's almost as bad as creationists claiming we can't know the age of the earth because no-one was there to see it. There's considerably less assumption involved in measuring the mass of the asteroid belt than there is assumption involved in me thinking i'm talking to an actual human over the internet right now.

All of this is getting away from my original point however, which was that you said asteroid belts could not exist because of gravity. Clearly they can and they do.I said asteroid belts like the ones you see on StarWars or StarTrek can't exist. The type most people imagine when hearing about asteroid belts, rocks, lots of them, densely packed, all swirling around. The real type of asteroid belt can obviously exist, but looks very different. Mostly absolutely nothing, with a pebble floating around every couple of thousand kilometres and a handful of big rocks distributed so thinly that you can shoot a probe through the belt on a random course and odds are you'll never see one.

Loads of assumptions here and I don't know where to start. Firstly, nobody knows how planets were formed, so you can't say that they are rocks (or behave as liquids, as you suggest).Yes we know how planets formed. And how they behave has nothing to do with how they formed, only with what materials they are made out of, and the forces involved in holding them together.

Secondly, there is a difference between something that is hard and something that is difficult to break up.So what? Hardness doesn't matter. In fact, there is no actual hardness at the energy levels involved. That was the whole point of pointing out that planets are essentially liquid.

Thirdly, if an asteroid field was formed by the disintegration of a planet, then I don't see the relevance of reducing it to dust first (and if you did, then it would only remain as a spherical ball of dust if the system was perfectly symmetrical and static).Planets don't disintegrate. Something needs to scatter the mass. Any energy sufficient to scatter the mass of planet is easily sufficient to break it into very fine dust or even vaporize it.

It is not inconceivable (for the purposes of science fiction at least) that a planet could cool unevenly so it contained fault lines. Then through further contraction or grativational resonance, you could see how it might break up.Planets don't break up. Planets can't break up because what holds them together isn't the hardness of the rock or the stickiness of the green cheese, but simple gravity.
So you've got some nice mechanism that causes a solid rock planet to resonate and break into a lot of shards. So what? The shards are all still sitting where they were before, and gravity keeps them there. No-one's even going to notice. Planets don't drift apart just because there's a crack in them. Just take a look at a freaking gas giant. Those things don't only have cracks, they have internal pressure. The only thing that keeps them from becoming a quickly dispersing cloud of gas is gravity, and gravity will hold a bunch of pieces of rock just as easily together as it holds a bunch of gas molecules.

Of course there have been no observations of anything like that happening because we have information on only a handful of planets (and in not much detail at that). So it is all speculation.I'm sorry to say it so bluntly, but that's rubbish. Science doesn't depend on people observing with their own eyes every possible occurrence. There is good reason why human testimony is actually pretty much the weakest kind of evidence of all.

DavidZahir
11-13-2010, 03:42 AM
You know, the more I think on this the more it seems to me that what you need is someone to have actually put all those rocks in orbit with fantastic care and some kind of self-correcting mechanism in place, presumably on a technological level mind-bobblingly advanced (a machine built of dark matter or existing in hyperspace or something).

telford
11-13-2010, 09:56 AM
Wow, I just wanted to float an idea out there; not start a debating war. The feedback from everyone has been great; so thanks guys. I think that I will have to fall back on the second law of sf writing: Write whatever you like as long as no one can prove you wrong. Thanks again for all the input.

Kenn
11-13-2010, 04:41 PM
Don't worry about Lhun, telford, he always gets stroppy if anyone tells him he is wrong;) I think that you are right, in that as long as it is at least feasible then it is good enough. After all, science fiction is about different scenarios and despite what Lhun seems to think, nobody knows how planets are formed (and we have only a handful of them on which to base our observations).

Lhun, you need to appreciate that 'popular' science underplays the uncertainties that really exist. Theories have a tendency to become facts and in areas such as astrophysics, especially, they are only that - theories. I am happy to debate your points further, but only if you become less aggressive.

telford
11-14-2010, 08:04 AM
Thanks Kenn,
Yes, I think you make a good point. Now you two boys slow down and behave yourselves; okay? Cheers.

ProtoMatic
11-14-2010, 05:44 PM
The asteroids would fall out of orbit. Eventually. Gravity from the primary would create drag on the asteroids, slowing them down, making their orbit too short, thus crashing them into the planet. If your stellar object has enough gravity to trap asteroids in any kind of orbit, it'll have enough gravity to create drag. This is even the case with the moon, or any object orbiting any other object. To remain in the same orbit, you have to add energy as movement.

As for the density of the asteroid field, that pretty much depends on the time it's been hanging around. Planets form from massive dust-clouds, slowly coalescing into bigger and bigger chunks, which in turn coalesces into even bigger bits. Once it's gravity reaches a certain point the friction within "ignites", and the core becomes a mass of flowing liquid rock and metal. This is what creates the magnetic poles, and the reason why you can easily say a planet is liquid, because the amount of liquid rock and metal far outweighs the amount of solid. And there is also an upper limit to how big a solid, rocky planet can be, although that is quite a lot bigger than the earth for example.

Lhun
11-15-2010, 12:39 AM
You know, the more I think on this the more it seems to me that what you need is someone to have actually put all those rocks in orbit with fantastic care and some kind of self-correcting mechanism in place, presumably on a technological level mind-bobblingly advanced (a machine built of dark matter or existing in hyperspace or something).Not a bad idea. The self-correcting mechanism doesn't even need to be terribly advanced. The problem with gravitationally unstable system is that they build up an unstoppable amount of momentum over time, but if you counteract any disturbance early on, even a little rocket can do it (well, unless it's a massive disturbance). Placing and supervising all those asteroid would be pretty challenging though.

Wow, I just wanted to float an idea out there; not start a debating war.Debating is what the internet is for. ;) At least the non-picture, forumy part.
The feedback from everyone has been great; so thanks guys. I think that I will have to fall back on the second law of sf writing: Write whatever you like as long as no one can prove you wrong. Thanks again for all the input.Sure. Just make sure you know what you're writing about, otherwise there's no way to tell if someone can prove you wrong. ;)

Once it's gravity reaches a certain point the friction within "ignites", and the core becomes a mass of flowing liquid rock and metal. This is what creates the magnetic poles, and the reason why you can easily say a planet is liquid, because the amount of liquid rock and metal far outweighs the amount of solid.Not quite. While it's true that some planets (like earth) are even physically liquid, the reason why you can treat all planet as liquid is because the strength of the chemical bonds producing rigidity in, for example rocks, is completely negligible compared to the gravitational forces acting upon something with the mass of a planet. It's in the very definition, i.e. planets are only those stellar bodies big enough to be pulled into spherical shape by their own gravity. The difference in "hardness" between a planet made of water and a planet made of rock matters no more than the difference in hardness between water and oil matter when you try to cut them with a knife.



Lhun, you need to appreciate that 'popular' science underplays the uncertainties that really exist. Theories have a tendency to become facts and in areas such as astrophysics, especially, they are only that - theories.Wow. Seriously, dude? I don't know if it's accidental, but using sound-bites like these, that are so strongly associated with the usual peddlers of pseudoscience will immediate give the impression that you don't actually know what you are talking about. Even if it really was accidental.
I am happy to debate your points further, but only if you become less aggressive.No thanks. I don't have the patience for that kind of post-modernist silliness. Accidental or no.

Kenn
11-15-2010, 02:42 AM
Wow. Seriously, dude? I don't know if it's accidental, but using sound-bites like these, that are so strongly associated with the usual peddlers of pseudoscience will immediate give the impression that you don't actually know what you are talking about.

Even if it really was accidental.No thanks. I don't have the patience for that kind of post-modernist silliness. Accidental or no.
You can't seem to help yourself can you Lhun. But, somehow I knew you would back off from a serious scientific debate.

You are still going on about planets being liquids, but I really don't know what you are trying to say. There are planets that exhibit fluid properties, but there is no reason to assume that every one of them will act like that. It will depend on its age and how it was formed. The formation of a planet will be influenced (strongly) by gravity and that obviously favours a spherical object - but so what? I don't think anyone was arguing against a round planet.

You go on about the asteroid belt in Star Wars and the nebula in Star Trek being impossible. I am not an avid follower of either, but I thought the latter, where Kirk dodged Khan, was supposed to be a star formation area (as in the current theory). I thought the asteroid field in Star Wars was supposed to be debris of a planet destroyed by the Death Star (and hence recent, albeit unstable). It is some years since I have watched either of these films, however.

You are confused about your light bulb as well. There are no rocks in it and it is not one of the best man-made vacuums (by a factor of about a billion!). I think you are confusing it with the number of molecules in interplanetary space.

Now your jibe about post-modernism is interesting (I asume you were talking about Thomas K). I wonder if you would care to elaborate on that as I think much of his work on scientific philosophy is very interesting? Philosophy plays an important role in science and, as I have told you before, I am a physicist by profession. So I will welcome a debate with you on either this or on science. But only if you can stop trying to make personal remarks, mind. What's the bet you're too busy though;)

Lhun
11-15-2010, 07:06 PM
You can't seem to help yourself can you Lhun. But, somehow I knew you would back off from a serious scientific debate.I don't back off from serious scientific debates, but there is nothing of the kind to be found here. Claiming to know better than wikipedia makes an argument neither scientific nor serious. If you want to start a serious argument, i suggest referencing your claims.

Now your jibe about post-modernism is interesting (I asume you were talking about Thomas K).No i wasn't. In my opinion Kuhn should have stuck to doing physics instead of trying to do philosophy, but why is besides the point here since Kuhn wasn't post-modernist anyway.

But only if you can stop trying to make personal remarks, mind. What's the bet you're too busy though;)It's really quite funny to read a request for no personal remarks in a post so full of them. Even in the sentence just after the request.

Kenn
11-15-2010, 09:58 PM
No i wasn't. In my opinion Kuhn should have stuck to doing physics instead of trying to do philosophy, but why is besides the point here since Kuhn wasn't post-modernist anyway.
What was he then? Why should he have stuck to physics? Did you know what I meant when I referred to Thomas K? So what did you mean by post-modernism then and why did you bring it up?

The problem with your (scientific) points is that they are all absolutes (i.e. 'is', 'cannot', 'impossible', etc.) and they are the ones that need backing up. The idea in science is not to provide a consensus or opinion, but to provide a rational argument based on material facts (referenced if appropriate, although there is nothing in this thread that has really needed referencing). That said, much of astrophysics is concept and concensus based, because of a shortage of hard data (for obvious reasons). The problem I have is that I do not know the scientific basis for your statements (and they have been statements).

Wikipedia has been widely criticised for being biased; in that it represents popular rather than expert information. It has also been criticised for being inaccurate too. That doesn't mean to say it is not a valuable reference tool, but rather it is one that should be used critically. I am not the first person to say that either. The danger is that people simply copy parts of it (and this does happen). I am not saying you have done that, but I don't know where you get your ideas from.

So let's debate the science. Where shall we start?:)

jvc
11-15-2010, 10:51 PM
Yes, debate the science. Don't get personal and respect is the name of the game. I was actually enjoying the discussion before it veered off. Bring it back on course or let it drop.

Lhun
11-17-2010, 06:47 PM
What was he then?A physicist.
Why should he have stuck to physics?Because he was a physicist. And him not doing terribly well in his attempts at philosophy shows that he should've stuck to what he knew. It's not that SSR is godawful, Kuhn is no Rand, but his attempts at philosophy are, if well-meaning, amateurish, just as for example Dawkins attempts at psychology are.

So what did you mean by post-modernism then and why did you bring it up?Your "Theories don't become facts" statement is used almost exclusively by two types of people: Post-modernists and Creationists.

The problem with your (scientific) points is that they are all absolutes (i.e. 'is', 'cannot', 'impossible', etc.) and they are the ones that need backing up.Every physics textbook or even wikipedia will back that up. We know how orbital mechanics work, we know in what way gravity acts, and we know how a bunch of big rocks floating around in space behave. When i say dense asteroid fields cannot exist, it is because we know how such a bunch of rock behaves, and the way it behaves is different from just calmly floating around in place.

The idea in science is not to provide a consensus or opinion, but to provide a rational argument based on material facts (referenced if appropriate, although there is nothing in this thread that has really needed referencing).I'm not the one claiming wikipedia or "popular science" are wrong. I'd call that a claim which requires evidence.

That said, much of astrophysics is concept and concensus based, because of a shortage of hard data (for obvious reasons). The problem I have is that I do not know the scientific basis for your statements (and they have been statements).I explained the basis several times. It all pretty much comes down to the fact that gravity simply prohibits all these things, because gravity would destroy dense asteroid fields or nebulae in short order, and gravity prevents planets from being destroyed by breaking. I'd be thrilled to hear of an expert disagreeing with that.

Wikipedia has been widely criticised for being biased; in that it represents popular rather than expert information. It has also been criticised for being inaccurate too.Criticizing wikipedia is a complete waste of time, because wiki is not a scientific source. Wiki does however reference all statements made from scientific sources, and if one disagrees with a statement on wikipedia, one has to criticize that source directly.

I am not saying you have done that, but I don't know where you get your ideas from.My physics class in university actually. I only use wikipedia if need to look up formulae i don't remember. (it's been a while since i had physics at university) But i haven't found any problem with wikipedia regarding the natural sciences so far.

Kenn
11-17-2010, 10:21 PM
You are diverging away from science again Lhun. You are entitled to your opinions on philosophy, Dawkins, Kuhn (or anyone else for that matter), but you should argue your point. All you are really doing is name-calling and making (often slanderous) statements. As for my comments on Wikipedia, I have said nothing that the site owners have not said themselves already. So I suppose my best reference would be Wikipedia. Now try and keep to the scientific debate.

Someone sent me a message, which I wish they had posted on here. It was about our own moon and its orbit. It used to be thought that it was a captured planet, but that doesn't seem to work out in terms of its orbit somehow. The current consensus seems to be that it was formed by a large object hitting the Earth. All of this is supposed to have happened many moons ago (groan!) and it has not come crashing down to earth yet. In fact, its orbit is getting wider (it is not being attracted towards the Earth by gravity). This is because of its angular momentum and tidal effects transferring the Earth's rotational energy to it. The Earth's orbit is getting wider around the Sun also and it was thought this might be because of the Sun getting lighter (in mass I mean!) due to all the energy it is burning off. Now I think the popular theory is because of a tidal effect aslo. Thankfully, the distances are very small:)

Lhun
11-18-2010, 12:12 AM
You are diverging away from science again Lhun. You are entitled to your opinions on philosophy, Dawkins, Kuhn (or anyone else for that matter), but you should argue your point.I'm not the one who brought up Kuhn.

All you are really doing is name-calling and making (often slanderous) statements. As for my comments on Wikipedia, I have said nothing that the site owners have not said themselves already. So I suppose my best reference would be Wikipedia. Now try and keep to the scientific debate.I explained the scientific side of things several times. Whether you did not notice, did not understand or choose to ignore it i cannot say. So far however you haven't addressed the arguments i presented. "Wikipedia is unreliable" is not a counter-argument to anything, it's just a general observation. At the very least you need to point out which of the things we're talking about are being wrongly presented on wikipedia.

Someone sent me a message, which I wish they had posted on here. It was about our own moon and its orbit. It used to be thought that it was a captured planet, but that doesn't seem to work out in terms of its orbit somehow. The current consensus seems to be that it was formed by a large object hitting the Earth. All of this is supposed to have happened many moons ago (groan!) and it has not come crashing down to earth yet. In fact, its orbit is getting wider (it is not being attracted towards the Earth by gravity). This is because of its angular momentum and tidal effects transferring the Earth's rotational energy to it. The Earth's orbit is getting wider around the Sun also and it was thought this might be because of the Sun getting lighter (in mass I mean!) due to all the energy it is burning off. Now I think the popular theory is because of a tidal effect aslo. Thankfully, the distances are very small:)Yes, that's correct. But your point is?
The orbital mechanics of two large bodies (including tidal forces) have nothing whatsoever to do with destroying planets, asteroid fields and nebulae or any of the things we talked about in this thread so far.

Kenn
11-18-2010, 01:17 AM
What exactly is your problem Lhun? You seem to be hell bent on destroying this thread. For the final time I will state the points I am making.

Firstly, astrophysics relies heavily on concepts and theories. There are no 'certains' and uncertainty is seldom reflected in popular science (and this is not restricted to astrophysics). It is something that is often debated when regarding the communication of science (especially in topical fields). If you want a reference to this in another field, go and read this month's magazine from the Royal Meteorological Society. Describing a philosopher who has debated such issues as 'amateurish' and someone you do not respect, without reason, does not further the debate.

The time scales on which you are basing your 'science' are sufficiently long for what you regard as 'unstable' systems to exist in a semi-permanent state. For example, if nebulae cannot exist, then you need to rewrite the currently believed theory of star formation. If planets cannot break up, then you need to rewrite the current theory of our own moons formation. If bodies are always attracted by gravity, then the moon and the sun's orbits cannot be widening.

Now it might be that I have misunderstood the rationale behind your statements. If I have, then it is up to you to reinforce your argument. But not by shouting or making obtuse comments; rather, by providing illustrations. I think everyone would welcome that. But otherwise, do us all a favour and stop posting responses like your recent ones on this thread.

telford (if you are still listening!) I think the range of possibilities for the formation, behaviour and types of planets in the universe is immense. I wouldn't get too bogged down about what some people say might be impossible.

Amadan
11-18-2010, 01:48 AM
Okay, I'm going to step over the debate between post-modernist faffle and science, and address this:


Thanks guys for the input. Yes, by the physics we currently understand, this is an impossible situation. But in the first book I altered the laws of physics and got away with it (I think). This is, after all, a science fiction book, so perhaps a bit of latitude could be expected if I apply the bs with a very delicate brush. Thanks again guys.


Wow, I just wanted to float an idea out there; not start a debating war. The feedback from everyone has been great; so thanks guys. I think that I will have to fall back on the second law of sf writing: Write whatever you like as long as no one can prove you wrong. Thanks again for all the input.

Telford, apparently you want your premise to be scientifically sound. That's a good instinct in writing sci-fi. You're right that the degree to which your "science" must stand up to rigid scrutiny is completely up to you. That's what Mohs Scale Of Science Fiction Hardness (http://tvtropes.org/pmwiki/pmwiki.php/Main/MohsScaleOfScienceFictionHardness) is about. You can ignore science altogether and write pure fantasy with sci-fi trappings (e.g., Star Wars) or you can make sure that everything in your story would stand up to peer review in a scientific journal (difficult to do unless -- or even if! you have a PhD in physics...)

That said... blowing off plausibility because it makes your story too difficult and "it's just fiction after all" is not a good way to earn the respect of science fiction readers. Sure, some will put up with blatant violations of the laws of physics if the story is good enough, but when you simply ignore physics because it interferes with the "cool" factor, it smacks of lazy writing, and unless you've got some fantastic writing chops, sci-fi fans usually expect to see at least an attempt made to justify things they know aren't actually possible (or at least likely).

So, I'd recommend you listen to Lhun.

I know the pain. Right now I am still trying to work out the details of my desert planet that is scoured by hurricane-strength sandstorms but still has mountains. I've come to the conclusion that I'm going to have to change my setting, because I just don't think the planet can exist precisely the way I pictured it in my mind and still be both habitable and physically possible. I could just go ahead and write it that way anyway -- many readers wouldn't notice, and many of the rest probably wouldn't care that much. But a few would, and more importantly, I would.

Cath
11-18-2010, 07:30 AM
Guys, you want to have a heated debate over this take it somewhere else please. If you're having a problem with any one personality, I heartily recommend the Ignore feature.

Kenn
11-18-2010, 10:46 PM
Okay, I'm going to step over the debate between post-modernist faffle and science...
I think you've got a hold of the wrong end of the stick here, Amadan. Post-modernist philosophy in science is about the way that contemporary theories change or develop, and it is not about the science per se. It is a bit of a red herring in this debate. The disagreement between me and Luhn is he is saying that gravity is the over-riding consideration. I agree that it is highly important, but there are also other factors that need to be taken into consideration in a non-static universe, which contains individual bodies with varying levels of spin and angular momentum. In other words, you don't just have to satisfy one law of physics, you have to satisfy them all. In doing so there is not a unique solution. I think a lot of the misunderstanding might have been about distance and time scales (i.e. what is 'stable' and what are the spatial dimensions of an 'asteroid field', for example). But I have said enough on the matter and will not contribute further on it.

Why are you having problems with your desert planet? If it is geologically active then mountains and sand storms should be able to co-exist. If it is because there is no food or water...well that's different;)

Amadan
11-18-2010, 11:14 PM
I think you've got a hold of the wrong end of the stick here, Amadan.

No.


Why are you having problems with your desert planet? If it is geologically active then mountains and sand storms should be able to co-exist. If it is because there is no food or water...well that's different;)

The thread is here (http://absolutewrite.com/forums/showthread.php?t=193668).

Kenn
11-18-2010, 11:59 PM
Yes; see your thread.

blacbird
11-19-2010, 02:12 AM
A real science story that may be relevant:

http://hubblesite.org/newscenter/archive/releases/2010/34/full/