Half a croissant, on a plate, with a sign in front of it saying '50c'
h a l f b a k e r y
Replace "light" with "sausages" and this may work...

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Many Pairs of Earths

Re-engineering other star systems
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As you may already know, astronomers have been discovering planets around various stars in the sky. A great many of these stars are younger than our Sun, and their planetary systems are peculiarly different than the Sun's. Giant planets, often more massive than Jupiter, are orbiting closer than Venus!

The astrophysicists have found that when the percentage of "metals" in a star-system is greater than a certain amount, big planets tend to form that ALSO migrate inward toward their stars, as the eons go by. (Note: astrophysicists consider all chemical elements beyond helium to be "metals".) There is no room for any equivalent of Earth in those star systems.

Worse, as the Galaxy ages and more and more supernovas manufacture metals and spew them into space, the percentage of metals that are part of new star systems can only go up. NO new star systems can ever be expected to naturally produce an Earth-equivalent, therefore. Any Earth-equivalents that we can find among the stars will be found around stars approximately as old as our Sun (plus or minus 20 percent, maybe).

This is not acceptable! If we want more Earths for our descendants to live on, then we are going to have to Do Something about this particular uncooperativeness of Nature. So, Engineers, start your 'dozers!...

The neatest thing about this Idea is, you will see, that we can operate on a very wide range of star-systems, from red dwarfs to pretty hot stars that may have "main sequence" lifespan of a billion years max. (The hotter they are, the less a star lives; red dwarfs can shine for a hundred billion years.)

The first thing we do is build a huge close-orbiting ring of mirrors around the chosen star. They are placed in a special polar orbit. Then, starting with the nearest planet, all the mirrors are focused on that planet. The special orbit for the mirrors lets the PLANE of the mirror-ring stay aligned with the revolution of the planet around the star. Billions of square kilometers of mirror-surface CONSTANTLY reflect the star's light toward the planet.

No matter how big it is, that planet will start to boil away, and the Stellar Wind will carry the vapor to the outskirts of the system, where we condense and collect the raw materials for Planetary Construction. Then we adjust the orbit and focus of the mirror-ring, to do the same to any other inner planets in the system, until "enough" room has been made for the next stage....

Allow me now to introduce you to the "Klemperer Rosette", if you haven't heard about them before. This Idea incorporates a twist on that one. A Klemperer Rosette is a group of evenly spaced equal-mass satellite bodies, in circular orbit around the primary body. It is a gravitationally stable situation (and one of the relatively few known solutions to the "Multi-Body Problem" in gravitational mechanics).

OK, so far we have considered the tearing-apart of existing SuperJovian planets, to make room for Earth-like worlds. Almost every star has a region around it which can be called a "habitable zone". Even most red dwarfs. In the habitable zone, the radiance from the star provides sufficient warmth for, among other things, liquid water, the key ingrediate of Earthly Life. Into this habitable zone, therefore, we begin to construct a Klemperer Rosette of Earth-equivalents, using some of the mass gathered previously. We will be able to make quite a few, safely distant from each other, and probably still have mass left over (Jupiter is something like 100 times as massive as Earth...).

Now as it happens, there is a sticking-point with respect to putting an Earth-like world in the habitable zone around a red dwarf star. TIDES. Even if constructed with the standard 24-hour rotation, the planet will ALWAYS be close enough to the star to experience enormous tidal effects, which will quickly slow its rotation and make it tide-locked. Well, if one side of the world ends up constantly being rayed by the star, while the other side freezes, then that world really cannot be called Earth-like any longer....

This is where my twist on the Klemperer Rosette comes in. The key thing to remember is that when doing gravitational calculations, you very often can pretend the mass of a body is all located at a single point. So, while the Earth and the Moon individually wobble in their orbit around the Sun, their "center of mass" makes a nice smooth ellipse. I therefore am describing not a simple Klemperer Rosette of Earthlike worlds, but a Klemperer Rosette of PAIRS of Earthlike worlds!

Each pair of worlds will revolve around a common center of mass. The mathematics of the overall Rosette only needs to consider those centers of mass, provided that there are not so many of them in orbit around the star, that neigboring pairs affect each other.

Now, what does that have to do with the tide-lock problem? Easy! A pair of worlds orbiting each other will be tide-locked to each other, not to the star! AND their mutual orbital period can be a nice simple 24 hours! (We have ordinary communication satellites orbiting Earth once every 24 hours; just imagine a duplicate of the Earth in that orbit!)

The net effect that every paired planet in the Klemperer Rosette around a red dwarf star will be able to maintain a 24-hour day/night cycle for a much much longer time than if those planets were not paired. And so the colonists will be able to claim a secure place for their descendants, even as the construction equipment, including mirrors, is carried off to the next star-system that needs to be re-engineered.

Vernon, Jul 06 2005

About Klemperer Rosettes http://burtleburtle...hysics/kempler.html
As mentioned in the main text. [Vernon, Jul 06 2005]

A relatively tiny solar furnace http://eric.hurtebi...tiscali.fr/four.htm
(In comparison to the world-smelter that's part of this Idea) [Vernon, Jul 07 2005]

" Astronomers discover most Earth-like extrasolar planet yet" http://www.berkeley.../06/13_planet.shtml
Last month. "the ability to detect the tiny wobble that the planet induces in the star gives them confidence that they will be able to discover even smaller rocky planets in orbits more hospitable to life." [waugsqueke, Jul 07 2005]

Previous discussion at the halfbakery Portable_20solar_20...igh_20concentration
[ldischler, Jul 07 2005]

About those frequency-doubling crystals... http://en.wikipedia...ki/Nonlinear_optics
Part of a wide field known as "Nonlinear Optics" [Vernon, Jul 08 2005]

Solar fundamentals; maximum achievable temperature http://www.volker-q...ntals2/index_e.html
[david_scothern, Jul 08 2005]

About Gravity Probe B http://einstein.stanford.edu/
As mentioned in an annotation [Vernon, Jul 08 2005]

Klemperer rosette http://en.wikipedia...i/Klemperer_rosette
[spidermother, Feb 25 2006]

boiling off a planet http://www.universe...planets-atmosphere/
I loved the sentiment of this idea and I thought of it when I read this article [MercuryNotMars, Feb 20 2007]

[link]






       There's an awful lot of gibberish and hand waving here, but no detectable invention.
ldischler, Jul 06 2005
  

       Looks like a well defined process to me. (Just very long and involving technology that I don't really understand).
st3f, Jul 06 2005
  

       Well defined? Vaporize a planet in one location and then somehow condense it in another? That's well defined? The idea fails at the first step, since the maximum temperature of the planet would be the surface temperature of the star. For a high metal planet, that's not going to be nearly enough.
ldischler, Jul 06 2005
  

       [ldischler], I think you are wrong about the maximum temperature of a planet that is located at the focus of billions of square kilometers of mirror.   

       Next, the recondensation of the vaporized planets must take place in the outskirts of the star system, well away from where the Rosette will be constructed. This is because SuperJovians have so MUCH mass, lots more than is needed to build the Rosette, it HAS to be all moved well out of the way. After that, the planet-building phase can follow the relatively Natural process of colliding planetesimals (guess what we make those from?). It is important that all manufactured Earthlike planets be built with hot cores, volcanic activity, oceans and tectonic plates. Otherwise weather/erosion will wash the continents down into the seas, COMPLETELY, in a mere hundred million years.
Vernon, Jul 06 2005
  

       We discussed this on another thread. To get any hotter will violate the 2nd law of thermodynamics.
ldischler, Jul 06 2005
  

       //that planet will start to boil away//   

       I'm stopping there.   

       Billions of square kilometers? That's a big ring! So, the sun basically has the reverse of those tin reflecters ladies used on the beach in the 60s.   

       Why don't you just put the sun in the center of a giant flashlight?   

       moving on...   

       I think shooting the stuff tangentially into a stable orbit would be easier. Just stay far away enough not to feel the gravity too strong that this tide locking dosen't happen. If that distance is too far for the giant to provide ample radiation, just throw one of your rings around it.
daseva, Jul 06 2005
  

       P = e * ( * A *(Th^4-Tc^4)   

       Power of radiation (in W*s/sq.m) emitted is directly proportional to the temperature difference between the hot and cold body. There is no such thing as negative power.
daseva, Jul 06 2005
  

       //Many Pairs of Earths Re-engineering other star systems// Imagined this as a new grounding scheme for electricians.
AbsintheWithoutLeave, Jul 06 2005
  

       Who needs planets ? If you can engineer on the scale required to do this, just build honking great Ringworlds or Dyson spheres, and go tootling around as you please. Why think small and old school ?   

       First, I want to see you solve the engineering issues (see link).
normzone, Jul 06 2005
  

       Engineers don't drive 'dozers.
Worldgineer, Jul 06 2005
  

       Well, I liked it.

One question, though. You're saying (correctly) that tidal forces will cause a single planet to eventually keep one face to the star, and I agree.
But do paired planets not do the same (I mean, one member of the *pair* would always be closest to the star, and the orbital period of one planet around its twin would become the same as the orbital period of the pair around the star)? I can half-see that they mightn't, if only because tidal 'squishing' of a pair of unconnected planets shouldn't dissipate energy in the way that tidal squeezing of a solid body does. But I'm not sure.

And, following from this, is a 'binary planet' stable when orbiting a star? OK, it's trueish for the earth/moon system, but what if the two planets are the same mass, as here? I did some simulations ages ago, just playing with multi-body systems, and never got a permanently stable binary planet. BUT this may have been because of rounding errors in the software, or the phasing of my calculation-step-time against the orbital times.

Neat idea though.
Basepair, Jul 06 2005
  

       I disagree with the premise. The reason why we have been locating mostly close-in gas giant extrasolar planets is because that's all we have the ability to detect using current methods.   

       As the science advances, we'll develop better methods for locating smaller bodies and at greater distances from their suns. I'm sure we'll find there are just as many, if not more, of those sorts.
waugsqueke, Jul 06 2005
  

       Welcome back, Real-[Vernon].
Texticle, Jul 06 2005
  

       The invention seems to be the pair of planets as a unit in a Klemperer Rosette. That is new to me, and seems likely to work, so I'll back that part as well worthy of posting on the Halfbakery.   

       The rest--giant mirrors and recondensing space vapor--seems like so much space vapor. It could work, though, someday.   

       I am wondering about tides inside each planet of a pair. It seems that bobbing back and forth relative to the sun every 24 hours would cause some stretching of some sort. It may be trivial.   

       Good one, Vernon! +
baconbrain, Jul 07 2005
  

       For exposing those of us that never would have stumbled across Kemperer Rosettes on their own, let me bestow the (+) that [baconbrain] has yet to ante up.
  

       Oops. Heh, heh. +
baconbrain, Jul 07 2005
  

       [ldischler], it seems to me you are not grasping the image I am trying to portray, with respect to those mirrors. First, you have to think about solar-sail sized film-mirrors. Just one can be quite enormous. Next, think about an ordinary equatorial orbit around a star, and fill that orbit completely with sail-mirrors. Set each mirror in this ring to send its beam at some location above one of the poles of the star. That point now receives, in addition to normal radiance from the star, all the addtional radiance that was directed toward the equatorial plane, and is now intercepted and bounced to the specified point. It MUST become hotter than before! Well, in the main text I specified the mirror-ring to be in a twisting polar orbit, such that the ring of mirrors can be entirely aimed at any planet in the equatorial plane, and as that planet goes around the star, the ("precessing" may be the appropriate word) ring can continue sending extra radiance to the planet. We KNOW that we can achieve high temperatures with solar reflectors; one of the biggest is a research facility in southern France. So, a big enough ring WILL boil a planet.   

       [normzone], planets have the advantage over technological habitats in space. Because if your civilization crumbles and your technology fails, a planet is not affected. It still has gravity to hold onto the air, for example. Its water cycle is solar powered, and so is the biosphere. No technological maintenance required! Giving you the chance to rebuild, rather than die.   

       [Basepair], it is my understanding that the tidal effects on a mutually tide-locked double-planet is to slowly cause them to orbit closer to each other, at the same time that their distance from the star increases. (It's a transfer/conservation of angular-momentum thing.) With respect to the Earth/Moon system, because they are NOT mutually tide-locked, what happens is that the Earth's rotation slows and the transferred angular momentum causes the Moon's distance to increase. Only after the Earth becomes locked facing the Moon will they start to orbit closer to each other and retreat from the Sun (but that is so far in the future that the Sun will become a red giant first). Anyway, regarding the constructed double planets suggested here, this could be an issue, but it definitely is a rather-long-term issue.   

       [waugsqueke], yes, they have been finding big planets because they are easier to find. But the fact that their orbits are so close to their stars needed to be explained by the theorists (who expected Jovian-mass worlds to mostly be fairly distant from a star). It is that explanation which then predicts that the era of natural formation of Earth-like worlds is basically over.
Vernon, Jul 07 2005
  

       Sounds easy, Why has no-one done this??
Minimal, Jul 07 2005
  

       //The rest--giant mirrors and recondensing space vapor--seems like so much space vapor. It could work, though, someday.// Like today, maybe.   

       Vernon, your mirror system is nice, but it could be bigger. I have thought up a mirror system that contains the vapor from the target planet, and provides for moving and condensing it.   

       I propose what might be called a Dyson Ellipsoidal Mirror. This has the sun at one of the foci, and the target planet at the other. The total light output of the sun is therefore focussed on the planet.   

       This shape, or sections of it, could be accomplished with individual elements orbiting independently. For vaporizing and containing a planet, a reflective Mylar balloon should be used, large enough to contain both the planet and the sun in their orbits, keeping them at the foci of the ellipsoid. When the balloon is moving to keep the planet in the proper focus, most areas of the balloon's surface will be in some approximation of a correct orbit around the sun. The pressure of sunlight will help support the shape of the balloon.   

       Once the planet is vaporized, the balloon will contain the vapor and will pressurize to some extent. When the section of the balloon behind the sun is removed, the balloon will move, from light pressure, solar wind and gas pressure. The nozzle ring will allow the sun out of the balloon, and will then be cinched closed.   

       The re-sealed balloon will have some velocity away from the sun, some pressure, and much solar sail area to use in moving it to the desired orbit. It can be cinched further as the vapor cools, and divided as needed. The reflectivity of the Mylar surface may need to be altered to allow cooling of the vapor.   

       **** I am taking this idea over to a separate thread for comments and annotations. I'm calling it Many Puffs of Planets so it will appear near this idea in other:terraforming.
baconbrain, Jul 07 2005
  

       // It is that explanation which then predicts that the era of natural formation of Earth-like worlds is basically over. //   

       What? No it's not.   

       The explanation fits the circumstances. The circumstances will change. Before they started looking, they wouldn't have predicted finding so many close-in gas giants, and that turned out to be wrong.   

       I don't know where you're getting your information. More recent discoveries have included small rocky planets in earth-like orbits, and they expect to find more of those. See link and get caught up on the technology.
waugsqueke, Jul 07 2005
  

       [baconbrain], I get the impression you are forgetting that the vaporized planet has the same mass (which must be moved to new location) as the original planet. Not quite as easy as you imply. But I agree that using mirrors that are NOT in orbit, but keep their distance from the star by sail-power, allows us to gather and focus a much larger percentage of starlight. Thanks!   

       [waugsqueke], I can agree that more data is needed. But from the data I know about, all the stars where they have been finding big planets are younger and have higher metal content than the Sun. Stars of about the same age/composition as the Sun, like Alpha Centauri, are still hiding their planets. So the key question is, what is the age/composition of the star where that (rather more massive than the Earth) planet was found?   

       Remember that the theory allows for a decent number of Earthlike worlds for stars of the Sun's generation. And this Idea, while focussing on ONE reason why lots of stars don't have Earthlike planets, is not restricted to that category. ANY star system without an Earthlike planet, for whatever reason, is fair game here! (Well, the appropriate mass for building at least one Earthlike world has to be available -- and for building two if the star is a red dwarf -- of course.)
Vernon, Jul 07 2005
  

       Vernon, you are incorrect to assume that you can achieve temperatures hotter than the star surface. As ldischler points out, this would violate the laws of thermodynamics. When the temperature of the focus equals the temperature of the star, the focus will emit energy at the same rate as it arrives. No further increase in temperature is possible. No, I'm not waving my arms and making stuff up, I have specifically been taught this by my thermodynamics lecturer.   

       I'm not aware of a fundamental limit on the power you can pass through the focus, however.
david_scothern, Jul 07 2005
  

       [david scothern], The Second Law of Thermodynamics states that energy cannot be extracted from a zero energy-gradient. I'm not seeing how that applies to stars and vacuum. Remember that the SURFACE AREA of the star is a factor. It radiates in all directions. When you gather a lot of that and reflect it to a POINT (or near-point, having much smaller surface than the source-area), then how can all that arriving radiance NOT have a higher magnitude/area ratio? Even a red dwarf star is probably converting hydrogen to helium at a rate of a fifty thousand tons per second. THAT'S the energy (maximum) available to be reflected/focussed!   

       Also, consider a laser, which is "just a bright colored light". It is known we can focus red light to an intensity suitable for vaporizing steel. All that is needed is enough TOTAL brighntess....
Vernon, Jul 07 2005
  

       Vernon, read what I wrote. /I'm not aware of a fundamental limit on the power you can pass through the focus, however./ See? I don't think there's a limit to the power you can put through, just the temperature you can achieve. You can't get hotter than the star surface, though, of that I'm certain 'cos a thermodynamics prof took it upon himself to teach us so.   

       The limit on power is the power output of the star. As entropy must increase, you're not gonna achieve a net concentration of this energy. The best you can do is break even (no entropy change) which means that the temperature of the focus will equal that of the star surface. If it got any hotter than that, it would suggest that you could concentrate the cosmic background radiation in a similar way and get power from nothing.
david_scothern, Jul 07 2005
  

       [ldischler, I will not allow this Idea to be deleted without seeing the proof that I am requiring bad science. And the fact that laser light is parallel means nothing. A spherical radiator can have almost all its light collected by an ovoid such as [baconbrain] suggested, and that light WILL converge tightly at the second focal point. That is, whether intially parallel or non-parallel, all we need are appropriately shaped optics to concentrate light.   

       [david scothern], can you provide a link or other data to support your professor's claim? Are you sure he didn't make an error? What would he say about the temperature of the spot where a hundred billion red Light Emitting Diodes were aiming their light? Thanks! --and with respect to the Universe, General Relativity says that Energy is Conserved only locally, not globally, heh heh heh (and I was surpised to learn that, too)!   

       The Cosmic Background counts as an essentially zero-gradient energy situation. Of course you cannot extract energy from it! But a star is just the shell surrounding a fusion reaction that is radiating in all directions, through a pretty high gradient into Space. I can agree that you cannot gather a star's light and obtain a temperature higher than the fusion reactions at its core, but at the moment I strongly disagree that the temperature of the star's surface is the limiting factor.
Vernon, Jul 07 2005
  

       I don't have a link at the moment, but can you disprove my second paragraph, that to concentrate the radiation from a star to produce a higher temperature would result in a reduction in net entropy in the system?   

       Regarding the LEDs, there's a net increase in entropy where the electricity is generated. It's not the same problem.
david_scothern, Jul 07 2005
  

       [david scothern], because mirrors are not 100% reflective, that is why you cannot gather ALL the star's light and focus it to a point, where the temperature would equal the stellar-core temperature. But you CAN gather enough light to exceed the boiling point of any ordinary matter. Being intercepted, reflected, and concentrated does not change the FINAL flow of that energy back toward Space, where it was heading in the first place.
Vernon, Jul 07 2005
  

       Imagine, Vernon, the ultimate case, where you are inside a globe that is heated to 5,000 degrees. The hottest anything inside can get using a passive system (even using mirrors) is 5,000 degrees.
ldischler, Jul 07 2005
  

       It's the surface temperature you can achieve, not the core temperature. The radiation emitted by fusion has degraded to the solar surface temperature by the time it reaches the solar surface.   

       Entropy must increase between any 2 points in the system, whether that be between the star and wherever the ultimate heat sink is, or between the star and the concentrator, or between the concentrator and the sink. Entropy will always increase. Hence claiming that you can decrease system entropy temporarily, 'cos later on it's going to increase again, is false.   

       The less-than-perfect reflectivity is not, I put it to you, particularly significant. ldischler's link mentions that the sun is not a point source, hence the concentration factor you can achieve is limited.
david_scothern, Jul 07 2005
  

       [ldischler], the problem with what you are asking me to imagine is that you are INSIDE a zero-gradient region. Consider that "temperature" is just an average measure of the kinetic energy of molecules. And kinetic energy, being energy, can be measured in watts, just like starlight. So, if you gather enough watts of starlight and focus it onto a piece of matter, what is to keep it from acquiring a nice large kinetic energy (temperature)? There is no difference between this and the billions of LEDs I mentioned in a prior post. May I remind you of a gadget known as a "hydraulic ram", which taps a large entropic flow to boost a little water against entropy?   

       [david scothern], the total number of watts emitted by the star is the same as that generated in its core (assuming steady flow through the matter gradient), no matter what FORM those watts take. Perpetual motion is NOT implied if you take some fraction of those watts and concentrate them. I did look at the link, and I CAN see how one cannot simply focus all of a non-point-source star's light into a region smaller than the star, but focussing a significant fraction into a small volume IS possible.
Vernon, Jul 07 2005
  

       What stops you is the difficulty of keeping all that energy in. The piece you're heating is going to emit heat. The hotter it gets, the shorter the wavelength (glows red, then blue, etc). The minimum wavelength is that of the incident radiation. This minimum wavelength is the wavelength of the light emitted by the star. It thus follows that the surface of the star is this colour, corresponding to its surface temperature. Hence the surface temperature of the star is the maximum temperature you can reach through simple concentration.   

       If you want to get hotter, you're going to have to do something else, eg collect the radiation, use it to generate electricity, dump a large fraction of the energy to space as low-grade heat, and vaporize things with a lower-power, higher-grade beam.
david_scothern, Jul 07 2005
  

       [david scothern], then you are also saying you cannot take the radiant energy from billions of red LEDs and use it to boil stuff? Photons are photons, remember....   

       I note the key fact that matter being bombarded with photons is expected to radiate energy as fast as it arrives, existing in an equilibrium. However, the rate at which energy can arrive is NOT limited by the color of the arriving light! A "mole" of photons arriving per second IS going to be associated with a higher equilibrium temperature of the matter than a mere few quadrillions of photons arriving per second, even if all are the same color, infrared for example.
Vernon, Jul 07 2005
  

       //May I remind you of a gadget known as a "hydraulic ram", which taps a large entropic flow to boost a little water against entropy?//

You can remind me all you want, but it's pressure being boosted, not entropy.
ldischler, Jul 07 2005
  

       Good point. It does not reduce entropy any more than a lever does.   

       Let's take the extreme case of trying to concentrate the cosmic background radiation again. Surely you agree that, no matter how much we reflect and focus it, it would be a violation of thermodynamics to expect to heat anything above the background temperature with it? How is collecting radiation from another source, and concentrating that, any different?   

       If we want to get a higher temperature than the radiation source, we need to be locally reducing entropy while globally increasing it, eg photovoltaic panels and an energy beam. Mirrors and lenses don't do this; they carry out the same action on the whole energy stream.   

       We have to take the surface temperature, not the core temperature, because we can't get to the core. If I had a ball whose surface was at 50 Celcius, there would be no way to boil water with it, even if I told you its core was at 200 Celsius. The core is not interacting with the surroundings; the surface is.
david_scothern, Jul 07 2005
  

       I like the idea [+]. It's really 2 separate ideas: destroying planets & the ideal rebuilt configuration.   

       I think there are many ways to destroy planets, perhaps better than mirrors. The neatness is in the rebuilt configuration. It's just so space efficient.   

       Also, it has many good metaphysical impacts. Would the inhabitants lean more towards polytheism?   

       Assuming that the larger, source planet is gaseous and orbiting further out (like Jupiter), could you simply position a ship further out from Jupiter, shoot projectiles through the gas cloud, have those projectiles gather up some mass and leave behind a gas trail which funnels yet more mass? Then they trickle on over to their final destinations. Just keep shooting these "seeds" through the source planet until you get enough mass for your earth-like necklace.
sophocles, Jul 07 2005
  

       The second (really, the third) part of the idea is nearly as flawed as the first, as the rebuiding part (assuming the transporting with the solar wind part worked) would be with with materials with no angular velocity around the star. So, when you begin to clump it, it will just fall back into the star.
ldischler, Jul 07 2005
  

       I believe [ldischler] is right. Due to the nature of image-forming solar concentration methods (focusing with a large mirror) and black-body radiation, the temperature of an object at the focal point is limited to the surface temperature of the radiation source. When the body reaches the surface temperature of the source, blackbody radiation losses are equal to incoming solar energy, and the temperature stops rising.   

       The total local energy flux per unit area can be higher than the surface of the sun, if the energy is being drawn off very quickly. However, the temperature is limited. If the target body can withstand this temperature, then it will not melt.   

       That's not to say that it won't vaporize. Temperature is an average, and thus some molecules are hotter than average and some are cooler. Invariably, some percentage of the molecules will be above the temperature required to become gaseous. For this reason, all solid bodies slowly sublimate, going from solid directly to gas (much like dry ice) at a rate proportional to their temperature. At high temperatures, this occurs more quickly.
Freefall, Jul 07 2005
  

       [freefall] maybe that explains how my solid body is occasionally letting out some gas. I've never seen it change much with temperature though.   

       Seriously, though, (or semi-seriously, this being the HB), if you had such resources to make those grand-scale mirrors, it would probably be easier to just tweak the orbit of some other massive bodies to have them collide with your target. Or, just start assembling in the new planets from an existing asteroid belt to skip the destruction step.
sophocles, Jul 07 2005
  

       Well to be honest, Vernon, I never even read your idea. I never got past the premise, and I still think you're off base.
waugsqueke, Jul 07 2005
  

       The only thing I can say is that this is much like bringing stones to a place with stones already. Much that energy (or much less) could be well put to use dragging the mass around a solar system to make a planet there or a planet there better. You could create a mini star or overpowered light/heat source to orbit a planet or asteroid, or use the mirrors to reflect greater light on an already dark world to make its distance from a star more habitable to those who may need it for much less energy.   

       But, yes, one could do what you said.
sartep, Jul 08 2005
  

       [david scothern], The big difference between trying to focus Cosmic Background radiation and starlight is quite like the difference between trying to focus clouded daylight vs focussing sunlight. Clouded daylight and CB radiation both come at you from all directions pretty equally, but starlight/sunlight is a distinct source, surrounded by a vast region of lesser energy-content.   

       Next, mirrors and lenses DON'T operate on the whole energy stream, because none are 100% efficient. And as an analogy to the photovoltaic thing you mentioned, remember that there are crystals that can frequency-double impinging light. As you know, color is associated with temperature, and so if our red dwarf starlight gets converted to green....   

       Your final point, about a 50-degree ball, is not analogous to a star unless you have some process generating energy in its core as fast as it is radiated from the ball's surface. AND I get the impression you are talking about immersing the ball in water, where I am talking about gathering up some of that radiated energy and focussing it on a compartive droplet. So the better comparison is, how much energy coming off the surface of the ball is impinging the droplet?   

       Now there IS a possible resolution to some of the conundrums I've tried to raise. For example, perhaps those billions of red LEDs really CAN'T be used to vaporize rock, simply because the "color temperature" isn't enough, JUST as you claim red dwarf starlight isn't enough. Then, with respect to the red laser cutting steel, perhaps that color temperature IS hot enough to cut steel, but not really vaporize it. I can accept pieces that fit in such a fashion.   

       That does NOT destroy the mirror aspect of this Idea, though. Note in the original text how I talked about vaporizing SuperJovians? --They are ALREADY mostly gas! Heating one up just makes its atmosphere expand to escape its gravitational field, and whole Earth-masses of gas will get boiled off that way, as gravity-squeezed gas that had been pressured into the liquid and solid state gets relieved and enabled to boil away and escape, also. Finally, all that will be left is a rocky core, which will resist boiling (but not sublimation, as [Freefall] pointed out). There could be reason to disassemble those cores by other means.   

       [ldischler], note that the preceding is NOT bad science, and indeed MOST of those SuperJovian worlds CAN get boiled away via the mirrors! (You may delete your MFD, therefore.)   

       Also, your comment about the lack of angular momentum is unwarranted. That SuperJovian had plenty of orbital (and probably rotational) angular momentum, and this will not have disappeared just because most of it was vaporized and collected in the outskirts of the star system.
Vernon, Jul 08 2005
  

       [Vernon], I was not setting out to say that the general concept was flawed, merely that by mirrors and lenses, you cannot achieve a higher temperature than that of the star surface.   

       I think that pointing out that mirrors, lenses etc might be only 99.99% efficient, is obfuscatory. By such logic, a theoretical mirror (100% efficient) would not work, while a practical one would. This is clearly not the case as it implies some sort of discontinuity. The practical mirror will tend towards the theoretical as it is polished, not away from it. The theoretical mirror acts on the whole energy stream, therefore a mirror-based system is not "tapping a large entropic flow to boost a little light against entropy". You are suggesting that the primary flow, the vast majority of the energy, is going against entropy while just 0.1% of it is being degraded. That is a second law violation.
david_scothern, Jul 08 2005
  

       //SuperJovian//

So you're punting, eh? But why bother with these "super Jovians" (hydrogen) if you have enough solar wind (also hydrogen) to blow the Jovian hydrogen away? You could just collect the solar wind and dispense with the first bad science step, and then we could argue about the third step (also bad), collecting this hydrogen (which hydrogen has lost its angular momentum as it was blown out in your solar wind, which necessarily has none. The rotational angular momentum of the planet doesn’t enter into it, as you should know.) Where was I? Oh yeah...further out to build a...what? I thought you wanted to build an earth? How are you going to do that with hydrogen?

Virtually everything in this idea is bad science. Like the mirrors:

//They are placed in a special polar orbit. Then, starting with the nearest planet, all the mirrors are focused on that planet. The special orbit for the mirrors lets the PLANE of the mirror-ring stay aligned with the revolution of the planet around the star.//

Which is laughable. The plane of the polar orbit doesn’t rotate around the star, so this mirror ring can’t keep up with the planet to be vaporized.
ldischler, Jul 08 2005
  

       I had a look into frequency doubling crystals. Their efficiency is of the order of 20%. Hence they do produce a net increase in entropy, as they must reject 80% of the incoming energy. Consequently they are fundamentally different from a mirror/lens based system, which theoretically rejects nothing.   

       I'm not saying that they wouldn't be a good idea in this context. It's worth recognising, though, that you have rather cherry-picked the details you consider relevant. These crystals work only with laser light.   

       I think we're broadly agreed, believe it or not. A temperature higher than the solar surface cannot be achieved with a passive solar concentrator. However, this may not be relevant as such temperatures may not be required. When they are, some method other than passive concentration can be employed.
david_scothern, Jul 08 2005
  

       [david scothern], thank you. That was definitely an oversight on my part. About your other post on the crystals, "only work with laser light"??? Are they SURE that coherence and not high intensity is the key factor (lasers are normally quite intense, of course)?   

       [ldischler], SuperJovians were discussed simply because most planets discovered so far HAVE SuperJovian mass (and the theory suggests that most new star systems are going to be infested with them). And since some of them are orbiting quite close to their stars, this implies the stellar wind from a Red Dwarf is inadequate to quickly blow their atmospheres away.   

       Next, while the Idea talks about a Klemperer Rosette of double-planets, it doesn't say how many or how few. The cores of a couple of SuperJovians can probably provide for a dozen or so Earths (six pairs), which would be a quite reasonable Rosette. Also, it could be argued that the "ideal Earth" should be less massive that the original Earth, perhaps 50% or so, not just because obtaining sufficient mass for a Rosette will be easier, but also because their gravity wells would be less troublesome for space traffic. (Mars, of course, being about 10% the mass of the Earth, is known to be too small, since it's lost much of its air and water. --And yes, I know that if we want a long-term volcanic smaller Earth, the percentage of radioactives in its core must be higher...yet they should be available for the same reason that the SuperJovians were orbiting close in the first place: more metals in those star systems than in Sol's.)   

       Next, regarding precessing polar orbits, this may not normally happen at the speed I'm suggesting here, but precessing CAN happen. Also, due to the fact that solar-sail sized mirrors were specified, it should be possible to actively adjust that polar orbit....
Vernon, Jul 08 2005
  

       Erm, nope, I can't find anything to prove that such crystals can only be used with lasers. I should have said that they _are_ only used with lasers; whether they can be used with other light sources is beyond my knowledge. Also my figure for efficiency is wrong; efficiencies up to 56% have been recorded. Naturally I'm not in any way a specialist in the field of nonlinear optics... I'm just blundering about in Google.   

       I suggest that these crystals can only double light frequency at one particular wavelength at a time, depending on the exact makeup of the crystal, operating temperature etc. Coherence is thus not required, but for efficiency, a pure source would be needed. I think that using them with white light would only be effective over an extremely narrow range of wavelengths.
david_scothern, Jul 08 2005
  

       //but it CAN happen//

Just putting that in caps doesn't make it so.
ldischler, Jul 08 2005
  

       [ldischler], you misinterpreted my meaning. I edited it slightly. Planetary orbits DO precess in various ways, at least in a system of planets. And for a polar orbit around a rotating mass, consider the "frame dragging" thing that Gravity Probe B is investigating.
Vernon, Jul 08 2005
  

       //The plane of the polar orbit doesn’t rotate around the star, so this mirror ring can’t keep up with the planet to be vaporized.// That happens to not be the case. A 'nearly-polar' orbit is used for many earth-observation satellites. They go over the polar regions on every orbit, but the orbit is skewed just enough that the plane moves to match the sun during the year. This is done so the satellite will always pass over at, say, 10 AM for the areas being observed. If not done, the orbital plane could stay fixed relative to the universe, and the area under the satellite change from light to dark during a year.   

       Vernon's mirrors can be placed in a 'nearly-solar-polar' orbit that mirrors this effect, and will behave exactly as he originally described. The plane of the orbit will track a planet.
baconbrain, Jul 09 2005
  

       Yes, you're right, bacon. The plane of earth satellites in a specific orbit can be made to precess over a period of a year, taking advantage of the asymmetric gravitational field of the earth. So I'll take back my objection to the mirror part.
ldischler, Jul 09 2005
  

       Thank you. Um, is that how it works? After I wrote that I started to realize my understanding of the reason for it happening was wrong. GIS classes don't cover orbital physics. Since it is done by //taking advantage of the asymmetric gravitational field//, can I assume the sun has the required asymmetry?
baconbrain, Jul 09 2005
  

       Wait a second. How many red dwarfs have giant gas planets? (Seriously; I have no clue.)   

       Secondly, wouldn't it just be simpler to put those planets a respectable distance from the star so that they didn't get tide locked, and then just use the giant mirrors to set up a kind of lens system so that the star APPEARED to be closer?
Owen, Jan 09 2006
  

       I love these. Vernon always makes it sounds so easy....
Minimal, Jan 09 2006
  

       //A Klemperer Rosette is a group of evenly spaced equal-mass satellite bodies, in circular orbit around the primary body.// Not quite (link).
spidermother, Feb 25 2006
  

       Unless all the mirrors were connected somehow in that polar orbit, they couldn't follow the planet around, as the center of the resulting orbit would not be the center of the sun. And as for the temperature problem - of course you could get hot enough. Temperature is a measure of average energy in a volume (more or less), so refocusing the energy of the sun on a sufficiently small volume could easily get hotter than the sun itself. Think about it. Point a billion low-powered lasers, or even light bulbs, at something and tell me you don't get a temperature higher then the 3000K or so of a tungsten filament. Another way of thinking about it: use a Peltier device (look it up) to lower the temperature of a whole swimming pool of water just a few degrees and I'll guarantee you can fry an egg with the resultant heat... just not an egg the size of the swimming pool... THAT'S the conservation of energy that everyone is so fond of quoting.   

       PS it would only start re-radiating energy at the same rate it is coming in if it was the same temperature.
Agamemnon, Apr 03 2006
  

       [Agamemnon], no, the mirrors do not have to be connected together. Consider just one mirror in the polar orbit. Draw a right angle from the mirror to the star to the planet. The mirror merely needs to be angled so that light from the star is directed toward the planet. As the mirror goes around the star in its orbit, the mirror rotates a little, to keep the correct angle for reflection to the planet. And as the planet moves in its orbit and the mirror's orbit precesses in sync, the mirror's reflected light continues to impinge upon the planet. Now multiply that by as many mirrors as we can put into that orbit, all independently operating the same way.
Vernon, Apr 04 2006
  

       I just want to agree with the idea that to my figuring the idea that you cannot focus light enough to acheive a temperature higher than the the temperature of the surface of the sun is absolutely correct. All stars that I am aware of have diameter which gives it a diminsion of entropy to all the light that comes off of it. when you use a magnifying glass that little dot at your focus is an image of the sun. if you have clouds you see the clouds in the image if you have a solar eclypse you see that in that immage. That image gets bigger if the glass focuses from a larger distance. the angle measured at the glass from one side of that dot to the other is the same angle at the glass from one side of the sun to the other. you could focus other light into that dot with a mirror underneath it and you can go put mirrors on the other side of the sun (no imagination for scaling that part down.) so that all that dot can see is sun and mirrors that is the limit. if you scaled up the back mirror you would just get a bigger dot not more concentration. Lets scale everything up Star and superjove at the foci of a three diminsional elipse(probably not stable but imagine) most of the light would miss the relativly tiny superjove and would probably hit the star again. You might increace the surface temperature of the star that way but I sure can't think of a way to exceed that the entire panoramic view would be an image of the star in full brightness. and since you could only see half of it from any one spot on the imaginary surface of the planet it would be like being on the surface of that star. This would soon get hotter than the original star. They never said you couldn't raise the surface temp of the star. stars are used as examples of nearly perfect black bodies and would eventually spit that light back out and might hit the superjove with more light. This might spike solar wind too for all I know. But I think if we were going to all this trouble you guys might want to look into a concept called the "Roche limit" and move that superjove in towards the sun instead. I know you have imagination.
MercuryNotMars, Jan 17 2007
  

       OK here are my issues.   

       1) I don't care how big something is .. when something is in space orbitting something else, if no other forces act upon it, it will not 'wander towards their stars'. Not until there is friction in space, they won't. They'll just go round and round and round until something knocks it off it's orbit. 2) Your orbiting ring of mirrors? Well, if it is a ring, and not lots of unconnected mirrors, sorry - it can't orbit. Firstly, orbits are not exactly circular .. things fall towards the [planet] and miss, time and time again. They have to ROTATE the planet. Geo-stationery satellites are only possible because the earth rotates. If you just plonk a satellite above London STATIONERY and let it go -- it will fall down and hit the earth! Same context, A ring of mass around the planet would simply fall directly to the planet. And hit it unless some other force acted on it. (Maybe the structure could be self supporting, but you didnt' say this.). 3) You want a planet which currently isn't being 'boiled away' by it's star, but adding a few mirrors round it and hey presto -- it's hot enough to actually vapourise the compounds -- at which point they will completely disregards the laws of gravity and choose to kind of wander off away from the planet? Don't think so. If this magic was possible -- the gases or vapour would STILL be attracted to the massive planet .. they would NOT think 'Well I'm feeling hot, let's leave and wander round space now'!!   

       4) Got bored of reading the idea by this point.
britboy, Jan 17 2007
  

       [britboy], I didn't make up what astronomers have said about big planets in recently formed star systems orbiting closer and closer to their stars. I suspect the reason for it is exactly what you mentioned, dust, because new star systems have much more dust in them than older ones did when they formed.   

       Next, the ring of mirrors is in POLAR orbit around the star, and it is selected to be a "precessing" polar orbit. Perhaps you should look that word up. The idea is for the orbit to precess at a rate equal to some planet's orbital period, thus allowing all the mirrors to direct extra light from the star to the planet, continuously.   

       Next, the amount of additional starlight that is redirected to the planet obviously depends on how big the mirrors are. Also, the light from the star by itself is subject to the inverse-square law, while the redirected light isn't. That's a major reason why boiling was thought to be possible. A second reason is that if we really are talking about boiling a Jupiter-mass planet, then most of that planet is made of gas that will boil to the escape-velocity point fairly easily. Finally, gas molecules, interacting with the beam of reflected light from the mirrors, can be expected to be pushed outward from the star. This is not magic.
Vernon, Jan 17 2007
  

       Wow, almost 2 years now. Is it built yet?   

       My telescope can't see it, but that's prolly a problem with my telescope.
sophocles, Jan 17 2007
  

       reflected light is subject to the same //inverse square law// the only way to get around it is to have squared mirrors surface. One mirror's focus point grows with distance. You are about to make me cry. I wanted to put mirrors on the moon and be able to dirrect all that light to any given spot on earth. I figured I could fry any given square mile of earth or do all manner of constructive things too with more sunlight than hits Texas at my disposal. That was my dream in life for a while and it felt good. Later I realized that is not something you can do. It is simple geometery. Look at the Sun and look at the Moon. They are the same size from our perspective. Draw a circle around texas and that is the size of the moon. Also the moon is aproximatly the same distance from the sun as earth. the angles are all the same. if every mirror on the moon was perfectly focused with the center shining on the center of texas the best you could do is make texas as bright as day and make them think that the moon is the sun. Cool but only moderatly useful and very wasteful. That is the limit. You can make the sky look like the sun with enough mirrors but that will be subject to the inverse square law if you start moving away even if you continue to focus. when the mirrors take up as much space as the sun to your view that is all the power they can deliver to your location. The calculation is that simple the more mirrors that take up your perspective the closer it can become to being like you are next to the sun. if the mirrors take up as much of your perspective as the sun you have only that much more light. If you put a mirror as big as the sun(slightly wider since it would be 30% from facing you) in L5 then you can double the light of the planet. This concept is clear to you?
MercuryNotMars, Jan 18 2007
  

       [MercuryNotMars], I am aware that light reflected from a flat mirror is subject to the inverse-square law, but I don't think I implied anywhere that the mirrors specified here were flat. Indeed if the idea is to focus light, curved mirrors are to be expected!
Vernon, Jan 18 2007
  

       I am talking about curved mirrors. when you look at a mirror focused on you you see one spot the sun you do not see the whole sun. it is as bright as the sun in that one spot and it gets smaller with distance. hence it two like the sun shines light on a spot porportional to distance. A mirror that looks as big as the sun to you can only shine as much light as the sun unless you pick a an exceptionally bright spot on the sun to shine on you. This limit dashed my dream! You cannot get all that light to hit a small planet with a mirror the same distance from the planet as it is from the sun. It doesn't matter how you focus it. That is why I want to put lasers on Mercury -- sobs uncontrollably as he opens his box of broken dreams. You need to sit down and trace lines and figure angles They have been telling you solid science about focusing light. You have Got to process it and take out the entropy before you can really use it. No matter how you curve a lense on a micro scale it looks flat and the photons that arrive from one side of the sun bounce off at the same angle and the ones arriving from the other side of the sun do the same thing. if you put up a projection screen bigger than the sun on the planet you would see an image of the sun full sized hence you would miss the planet with most of it. if it was a flat mirror it would be inverse square of the distance from the sun to the mirror to the planet. All you did is change it to from the mirror.   

       Will you join me on my quest to turn mercury into a laser push station? I think it would do you good to understand why laser light is unique and how it is made. Laser cooling would make a good explanation about the nature of entropy in non-coherrant light. research those two things please after you have traced some lines.
MercuryNotMars, Jan 18 2007
  

       +1   

       I trust Vernon in all things. hic!
po, Jan 18 2007
  

       [MercuryNotMars], I'm aware that the light coming from a star at different angles to the mirror, cannot be reflected/focused like parallel light rays coming from a star. But I'm quite certain that there are a lot of parallel-ENOUGH light rays coming from a star, near the star, which can be reflected/focused reasonably well by the specified polar-orbiting mirrors. The rest of the light from the star would be not used, I agree.
Vernon, Jan 19 2007
  

       //Will you join me on my quest to turn mercury into a laser push station?// - wow ! MercuryNotMars and Vernon go off into orbit together, leaving a trail of text behind them like a comet......
xenzag, Feb 20 2007
  
      
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