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
Open other side.

idea: add, search, annotate, link, view, overview, recent, by name, random

meta: news, help, about, links, report a problem

account: browse anonymously, or get an account and write.



Please log in.
Before you can vote, you need to register. Please log in or create an account.

Venus 2.0

Its mostly done with mirrors, of course!
  (+6, -2)
(+6, -2)
  [vote for,

I just discovered that part of this idea has been independently dreamed up by others (see terraforming article at wikipedia.com), but the other part perhaps has not. So be it.

The Law of Gravitation lets us compute a location in space where the attractive forces between two objects cancel each other out. This is usually called the First Lagrange Point, or the L-1 Point, after the mathematician who first worked it out. Currently NASA has a special satellite at the Earth/Sun L-1 Point, called SOHO, which has been on-station for several years, and is constantly observing the Sun (the Earth can never block the view!).

Venus has an L-1 point with respect to the Sun also, of course. The first part of this idea is to put a huge disc there, perhaps 15,000km in diameter. The shadow cast by this disc needs to COMPLETELY shield Venus from the Sun.

Minor details regarding the disc are that it should be a mirror, to protect itself from all that sunlight, and it should have a balance between mass and area, like a solar-sail, so that it never needs fuel to hover on-station at the Venus/Sun L-1 Point. Indeed, the outer rim of this sail should be adjustable, so that its total area can be diminished a bit, to let it fall closer to the Sun, or expanded a bit, to let it be blown by sunlight (and the Solar Wind) farther from the Sun. This would be analgous to the ballast tanks on a submarine. And, of course, the mirror needs to rotate once per Venus-year, so that it constantly keeps its full area shielding Venus from the Sun. This mirror must be built to be as permanent and reliable as possible.

OK, with NO sunlight arriving, Venus will in short order experience an Ice Age, colder than Pluto, with frozen carbon dioxide blanketing the surface, and vacuum everywhere. Then would be a good time to land nuclear-powered mass-drivers (electromagnetic catapults) in several places, along with appropriate scooping machinery. Cannisters of frozen CO2 can be launched totally away from Venus, and in fact probably should be sent to Mars, to thicken its air. After enough has been sent, the equipment is shipped out for other uses elsewhere.

From the Oort Cloud we locate some sizeable ice bodies (there are closer ones, such as might be moons of Saturn, or even the worldlet known as Chiron). The afore-mentioned mass drivers can now be used like rocket motors, expelling some ice to push the rest of these bodies until they get onto a collision course with Venus. We will be wanting plenty of water, so we need to move a number of worldlets -- even a 100-km-wide ice body will only be a drop in the Venus-bucket.

A significant goal will also be that of seeking large amounts of ammonia-ice, which will provide essential nitrogen for the future atmosphere of Venus. I think some of the outer moons have decent supplies.... This part is a bit iffy, because I don't know how much nitrogen Venus currently has in its atmosphere. Perhaps, after the excess carbon dioxide is shipped out, the existing nitrogen may prove sufficient.

Now we are ready for the second big trick, which is to put another mirror in space near Venus. This one gets put into a 24-hour orbit! It reflects sunlight to the surface. The amount that arrives will depend on the mirror's diameter, and of course we will be wanting this to equal the amount that we are comfortable with here on Earth. And it yields a perfectly Earthly day/night cycle. And as soon as the place warms up again, we can start importing Life. (We can put a smaller mirror in a month-long orbit if we want to simulate the Earth's Moon -- without the tidal effects, of course.)

Note that this day/night mirror is also going to need to be like a solar sail, because its orbit will require constant adjustment throughout each Venus-year. See, it needs to be in a technically polar orbit (with respect to Venus' rotation), because it needs to be in sunlight all the time, and that means it must circle outside and around the conical shadow cast by the big mirror at the L-1 point. Only constant orbital adjustments will meet the need for reliable sunlight, as Venus revolves about the Sun.

The preceding is a workable set of ideas, but the result is actually still going to be rather alien to Earthlings. Some background information is now essential, in order to be able to explain this clearly. First, as you may know, the planets in the Solar System mostly go around the sun in a disc-like region known as the "ecliptic". If we left the Earth from its North Pole and looked down at the ecliptic from a distance, we'd see all the planets moving counterclockwise around the Sun. And we'd also see that the planetary rotations (and the Sun's rotation) are mostly counterclockwise, also. The exceptions are Uranus, which has a sideways axial tilt, and Venus, which is almost perfectly "upside down" -- it would be seen to rotate clockwise, slowly (once per 243 Earth-days). Technically, one should consider the North Pole on Venus to be on the same side of the ecliptic as the South Poles of all the other planets (standing on the North pole of a world, you rotate counterclockwise).

On Earth, the polar regions are cold because sunlight arrives there at a shallow angle. (A simple sunbeam through the clouds, when it illuminates the ground, covers more ground surface than a similar sunbeam at the equator. And less light per unit of ground area means less warmth.) The effect of reflected light from the day/night mirror will be much the same, but actually worse, because this mirror will be so much closer to Venus than the Sun. True sunlight arrives in parallel beams, because the Sun is bigger than the planets it shines upon, while reflected light is going to have a conical spread. Some careful planning is going to be needed, to ensure that ENOUGH light is reflected, to keep Venus warm, without frying the regions directly beneath the mirror!

Now note carefully that the regions of diminished reflected light will NOT be the axial-rotation poles of Venus, because the day/night mirror has to be located in a polar orbit. Venus' axial poles will ALWAYS be directly illuminated as the day/night mirror passes overhead! So this means that the regions of Venus that receive the least amount of reflected light will be located on the equatorial belt of the planet. We can count on both of them to be wintery.

However, because Venus DOES rotate (243 Earth days), and because it DOES revolve around the Sun (225 Earth days), those two wintery regions are going to "move" around the equator of Venus. If my calculations are right, one of those wintery regions will move completely around Venus' equator in 225-(243-225) or 225-18 or 207 Earth-days (the directions of Venus' rotation and revolution work together to reduce the time). Since there will be two wintery regions, any point on the equator will be experiencing cold weather every 103-104 days (a bit more than 3 Earth-months), and hot weather equally often. Regions between the equator and the poles will be more temperate, of course, but the weather is still going to be "interesting", becoming warmer and chillier in the same cycle. I'm pretty sure that Earthly life-forms will be able to adapt in short order, as soon as bacteria have prepared enough soil for plants to produce enough oxygen.

Vernon, Feb 04 2004

Terraforming article at Wikipedia http://en.wikipedia.org/wiki/Terraforming
Only a small amount of text is devoted to Venus. [Vernon, Oct 04 2004, last modified Oct 06 2004]

Atmosphere of Venus http://library.thin...CR0215468/venus.htm
[bungston, Oct 04 2004, last modified Oct 06 2004]

Meteor snowballs http://www.virtuall...7/may/m30-003.shtml
If only they would use their powers for good... [bungston, Oct 04 2004, last modified Oct 06 2004]

Lagrange Points http://www.physics....rnish/lagrange.html
The L-1 Point is indeed at all times between the major body and the minor body (Sun and Earth at link; Sun and Venus in this Idea). [Vernon, Oct 04 2004, last modified Oct 06 2004]

Past Global Warming (1) http://www.aas.org/...2n2/spd2000/245.htm
Here is a short description, with the observation that past trends may continue. [Vernon, Oct 04 2004, last modified Oct 06 2004]

Past Global Warming (2) http://earth.usc.ed...ariability/co2.html
Here is a much more thorough description. Not so long ago I encountered an essay to the effect that Gaia (EarthLife as a whole) is running out of ways to protect itself from the Sun, and humanity has been developed so that our supposed intelligence can recognize the long term problem, and do something about it. [Vernon, Oct 04 2004, last modified Oct 06 2004]

Venus presents same face to Earth at closest approach http://www.physics....81/planet/venus.htm
I was surprised, too, when I first learned that, some number of years ago. [Vernon, Oct 04 2004, last modified Oct 06 2004]

About Earth's Moon http://infoman16.tr...m/Articles/moon.htm
The part about the Moon being in Solar orbit is about four paragraphs from the start of the text. [Vernon, Oct 04 2004, last modified Oct 06 2004]


       Vernon, and you're going to do all this without a cellphone?   

       Kidding aside, by the time you can shadow Venus don't you think you may be able to cool it by other means?
theircompetitor, Feb 04 2004

       No, I think that shadowing Venus will be the fastest way. Note that we could start with comparatively cheap "conventional" solar sails as the shadow source, while the permanent disc was under construction.
Vernon, Feb 04 2004

       [grayure], others have wondered about how much water is in Venus' atmosphere, and from what I've read, the measurments that we have say that the situation there is pitiful. For 4.5 billion years solar UV has been breaking down water molecules in Venus' upper atmpsphere (no ozone layer to stem the losses), and the hydrogen has been escaping to Space. The water that survives today could cover the planet to an inch or two. --From what I recall reading.
Vernon, Feb 04 2004

       That's some pretty crazy scheme you got there, Vernon. It would definitely make for an easy target in imminent war. That aside, it's genious. +
yabba do yabba dabba, Feb 04 2004

       Cut out the middle man and partially shadow Venus to achieve the temperature you want. No need to build two separate satellites. Good idea, though. Gotta colonize the galaxy sometime, why not now?
Mungo, Feb 04 2004

       Please leave Venus alone.
waugsqueke, Feb 04 2004

       [yabba do yabba dabba] and [grayure], it would indeed be possible to fit the sunshade with lots of solar power collectors, although we would have to pay close attention to the overall mass, if we want to use solar-sail effects to keep it on-station at the Venus/Sun L-1 Point. A certain amount of power collection should be done, just to keep its automated systems running. ONE of those systems should be some sort of meteor defense, perhaps consisting of sliding adjustable-size panels that are moved out of the way before a meteor can impact. Smaller stuff might be zapped with lasers -- and also incoming missles, of course. I had a notion of an onboard repair factory that gathered space dust to get the raw material to make spare parts, whenever recycling couldn't work (say a meteor storm managed to punch some holes, because there were too many to shoot or dodge -- that material has to be replaced). "...as permanent and reliable as possible." I wrote, in the main text of the Idea.   

       [Mungo], the problem with what you suggest is that you cannot get a 24-hour day/night cycle that way. If we terraform Venus, we will want to make it more home-like than having a day/night cycle that lasts hundreds of Earth days. MUCH simpler to put a mirror into orbit, than to try to speed up the planet's rotation....   

       [waugsqueke], why? The human species cannot stay on Earth forever (the planet is due to be roasted by an aging Sun in a few billion years). And WHEREEVER we go, we have a tendency to modify environments to suit ourselves. Do you never use air conditioning? The only thing that should stop this Idea is the possibility that Venus is already inhabited by life-as-we-don't-know-it. Have you any evidence for that? Otherwise, Venus could be the best alternative to Earth in the Solar System, because its gravitation is close to Earth's value. Everywhere else our muscles would atrophy, if we lived there (Moon, Mars, etc.) long enough.
Vernon, Feb 05 2004

       // The human species cannot stay on Earth forever //   

       I doubt the premise of that statement. Even if it were true, we will have developed other options over the next few billion years.
waugsqueke, Feb 05 2004

       [Vernon], have you read blue mars?   

       It has some interesting ideas, including using mgnetic induction to adjust the speed of rotation of planets (I think venus, but I could be misremembering).   

       How would we go about calculating the time taken for venus to cool down? Umm, stefans law woud give the luminosity I supose. Then we could assume venus was made entirely of one kind of material, we could have a simplistic estimate. Maybe I'll look up some figures and have a quick go later.
RobertKidney, Feb 05 2004

       I can't believe you've typed so much about this proposal, do you not have a job or family to go to?   

       Lets sort out our own planets mess, before we mess up other planets.
grippit, Feb 05 2004

       [Vernon] types long ideas, others type many short ideas. Whats the difference?   

       It may turn out that the best way to sort out our plannet would be to send some of our excess population elsewhere. And Venus isn't really doing anything for anyone at the moment.
RobertKidney, Feb 05 2004

       can we make sure she keeps both arms in the second version?
theircompetitor, Feb 05 2004

       [grayure], space habitats have their good points (cheaper than terraforming) and their bad points (difficult to see the stars through all the required cosmic ray shielding). One thing I didn't mention was the view of the SunShield from Venus in this scenario -- think "total eclipse with solar corona visible all 'night' long" (if you happen to be located on side of Venus facing the Sun, of course). Terraforming Venus might be worth it just for that view!   

       [waugsqueke], you have dodged the question: WHY leave Venus alone?   

       [RobertKidney], yes, I'm sure that with a sufficiently advanced technology we could (re: [waugsqueke] mentioned "other options") extinguish the Sun, saving it as a fuel tank for our civilization's fusion reactors. Changing planetary rotation rates would be trivial by comparison. --Oh, and I think you will be surprised how fast the surface of a planet will freeze when no sunlight is arriving. A month or less, I suspect.   

       [theircompetitor], nice thought; wrong Venus :)
Vernon, Feb 05 2004

       [humanbean], I didn't suggest wasting Venus' CO2 supply. Exporting a lot of it to Mars would be useful there (It could benefit greatly from the greenhouse effect!). I do agree with the philosophy that we should only do that after we know that Mars has no life forms on it, and thereby can be claimed by Earthlife. And I did specify only shipping out the "excess" carbon dioxide. On both Venus and Earth roughly equal amounts of CO2 have been spewed by volcanoes over the gigayears, but on Earth much CO2 is locked up in limestone and marble, due to the actions of Life (shellfish and coral, mostly); on Venus the CO2 just accumulated in the atmosphere. Anyway, humans are more impatient than Life in general, so we will want to get rid of most of that CO2 as fast as possible. Perhaps we can build a nice hollow Moon for Venus, and fill it with frozen CO2. Then, if any needs to be shipped BACK, it will be close at hand.   

       As for taking the oxygen from the CO2 and combining it with atmospheric hydrogen, there is so little of the latter that it wouldn't be worth the trouble. Better to just import lots and lots of ice.
Vernon, Feb 05 2004

       I guess I don't understand why you don't just put the first big plate into orbit. It could completely shade Venus half the time. You could set the orbit so that it would shade the day side, which would cut heat more. One is simpler than 2.   

       I was thinking about photosynthetic organisms also. The problem is that they would starve for nitrogen, I think. You would have to crash an ammonia-ice planetoid into it first. Also it would be hard to suspend them at the right level of the atmosphere, although given time I am sure the organisms could sort that out themselves.   

       I wonder if you could have floating inorganic catalysts, buoyant at the correct atmospheric level, that reduced CO2 to O2 and graphite. Some metals can reduce CO2 under the right circumstances, I think.
bungston, Feb 06 2004

       [bungston], with Venus physically rotating once every 243 Earth-days, how is a single mirror in orbit going to provide a 24-hour day/night cycle, for every part of the planet?   

       Next, nitrogen is less of a problem than you are thinking, since that link you provided (thanks!) says that 3% of Venus' atmosphere is nitrogen. Why? Because of the definition of "partial pressure". If the total atmospheric pressure on Venus is 90 times that of Earth, then 3% of that is MORE nitrogen in Venus's atmosphere than is in Earth's atmosphere! (Likely Earth has roughly the same amount of nitrogen, but mostly it is "fixed" in various compounds, instead of being loose in the air.)
Vernon, Feb 06 2004

       // It may turn out that the best way to sort out our plannet would be to send some of our excess population elsewhere. // [RobertKidney]   

       LOL! How about colonise under the sea? Colonise inner Earth? Sterilisation? Education? - No lets go and terraform another planet and colonise that! Tell ya what, while were at it, lets terraform the Sun and live there - Hahaha LOL! DREAM ON!
grippit, Feb 06 2004

       //with Venus physically rotating once every 243 Earth-days, how is a single mirror in orbit going to provide a 24-hour day/night cycle, for every part of the planet?//   

       The mirror is reflective on both sides. On the bright side of Venus, it provides shade. On the night side, it reflects the sun in a manner akin to a full moon. It orbits with a 24 hour period. Day on the bright side will be brighter than day on the dark side, but thats how it goes.   

       I did not even think about the partial pressure issue. That would be plenty of nitrogen. It makes me like atmospheric carbon-fixing critters even more. Upper levels of the atmosphere should be cool enough for life. I wonder if there are lichens or some other xerophilic critter that could get by with the limited water available. Or maybe they could tap into that constant bombardment of ice meteors that happens to all planets (link).
bungston, Feb 06 2004

       [bungston], you seem to be forgetting that when your mirror is on the side of Venus away from the Sun, illuminating that side, the SUN is illuminating the other side! Perhaps you are thinking of the WHOLE planet being in daytime or night time, at the same time? Well, this is going to require a mirror that is as long as half its orbit around Venus...MUCH bigger than the stationary disc I suggested for the L-1 Point. Both my mirrors together will be smaller than yours!
Vernon, Feb 07 2004

       I do not think that the L1 point is the point in space directly between the planet and the sun, as required in the idea's first part.   

       You'll need to actively keep a 'sunshade' in orbit, somewhere near Venus, in order to cool it.   

       Impossible. Cool it.
neelandan, Feb 07 2004

       [neelandan], the L-1 Point is semi-stable, so that some minor effort is needed to keep a satellite (or sunshade) on-station there. I was careful to specify that the Venus sunshade use solar-sail properties to stay on-station (no fuel needed). Certainly the sunshade would be big enough to put most ordinary solar sails to shame, heh heh.
Vernon, Feb 08 2004

       I gotta go against waugs on this one in general. It's not like you're going to be disrupting an ecosystem or anything.   

       But in a billion years, I doubt if anyone will *want* to be closer to our sun. It's liable to be a little different by then.   

       See... here's the problem I've got in general with importing more sunlight onto the earth as was suggested by someone here. We've got our fair share of energy from it here, and if we get more, it's going to get warmer here. Perhaps a gigantic radiant heat sink...
RayfordSteele, Feb 08 2004

       [RayfordSteele], it could be that with a suitable SunShield shadowing Venus, the planet could become habitable for the rest of the Sun's lifespan (until it bloats to Red Giant stage and becomes bigger than Venus' orbit). That's four or five billion years away. And, such a SunShield could be good practice for EARTH! Because according to stuff I've read, the Sun has been slowly brightening for the last few billion years, and perhaps in less than another hundred million, the Earth is going to start to get too hot for comfort. If true, then all we need (at the appropriate time) is a SunShield at the Sun/Earth L-1 Point, and then Earth also will be OK until the Sun bloats. (It MAY be OK even after that, because nobody knows if the Sun will grow large enough to reach Earth's orbit. If it doesn't, well, Earth WILL have to have a rather bigger SunShield at that time, heh heh.) Anyway, what I'm thinking is that a Venus SunShield would be terrific practice for a possible vital future Earth SunShield....
Vernon, Feb 09 2004

       If you are going to smash things (blocks of ice, etc.) into venus couldn't they be used to alter venus' spin?   

       Solar powered ion drive, send them round the sun the oppositwe way to the orbit of venus, smash them into the correct side of venus to cause desired effect on spin.   

       Sorry about not working out how fast it would cool in the shade, but I haven't been able to find enough information to make a sensible estimate.   

       Maybe a big impact with a rock could get rid of a lot of atmoshpere. It would be a waste of valuable chemicals, but it could speed things up by quite a bit.
RobertKidney, Feb 09 2004

       [grippit], it seems like its often easier to carry out massively expensive projects than to change peoples habbits and opinions.   

       There could well be a limit to how many people our bioshphere can support, so finding new ways of packing people onto earth might not be a good idea.
RobertKidney, Feb 09 2004

       I also have considered such notions as using those vast numbers of impacting iceballs to change the spin of Venus, but I have concluded that it is wasted effort. Consider the Earth's oceans as a thin skin on the surface of the 12,756-km-wide planet: The total mass of those oceans are a trivial part of the globe. Likely you would need relativistic velocities to provide enough momentum to make a difference, when impacting an ocean's worth of water onto Venus.   

       AND, remember why Venus is rotating so slowly in the first place! The Sun and Earth, working together, have tide-locked it. (Venus presents the same face to Earth every closest-approach.) The gravitational influences which have led Venus to its present state will not go away, just because we put effort into spinning Venus (back?) up to a 24-hour day! So, if we did that, and moved there, and then needed to KEEP Venus spinning at the desired daily rate, we certainly couldn't use relativistic impacts to do that, could we?   

       That is why I choose to use mirrors, to get a 24-hour day on Venus.
Vernon, Feb 09 2004

       Hmm. You're right about relativistic velocities. (Unless we used an absolutely unimaginable amount of stuff.)   

       How about something a bit different. What would happen if venus had a moon? We could (well it is physically possible) drop a really big rock down the sun's gravity well and have venus catch it in orbit. Could having a moon help to un-tide-lock it?
RobertKidney, Feb 09 2004

       [Vernon] - I think you'd have better luck adapting humans to live on hostile planets rather than adapting Planets for humans to live on.   

       The first step would be to somehow increase our radiation tolerance, then our ships wouldn't have to carry so much heavy radiation sheilding.
SystemAdmin, Feb 10 2004

       But have you considered how Marvin might react? I think this would make him angry.... very angry indeed.
RayfordSteele, Feb 10 2004

       If we're considering inter-planetary migration (which I don't object to in principle; though I have issues with the timing), I would have thought that moving further from the sun would be the sensible option rather than moving closer to it. If it were down to me I would prefer to take a halfway approach between SystemAdmin's 'modify humans' idea (read Frederick Pohl's 'Man Plus') and Vernon's 'modify the environment' approach. I'm not keen on large scale 'terraforming' schemes simply because we have no way of knowing what we may be destroying in the process.
DrBob, Feb 11 2004

       [RobertKidney], I think the best possible moon for Venus would be to move Mercury away from the Sun. Then the Venus/Mercury system would quite nicely be similar to the Earth/Luna system. Note that Luna is not really in orbit around the Earth: Both Earth and Luna are actually in orbit around the Sun (the Sun gravitationally attracts Luna twice as strongly as the Earth does); the two bodies merely move out of each other's way in their slow orbital dance. It should be simple enough to do manage a similar dance when moving Mercury out to Venus' orbit -- simpler than moving that planet, anyway, heh heh!   

       Well, we could put solar-powered mass drivers on Mercury, mine its mantle down to its core, and throw that mantle material out to the desired place in Venus' orbit, so the constructed object would not only be roughly the same average density and composition as Luna, it could even be a close match in size! And, of course, that extremely valuable Core of Mercury would become easily accessible!   

       Next, I'm pretty sure that Luna does not help the Earth retain its 24-hour day. It DOES help the Earth retain its axial tilt. (Mars' tilt is believed to vary a LOT, due to lacking a significant-sized moon.) Venus' tilt doesn't change because it is tide-locked, but that lock may indeed be broken, because of new gravitational attraction of its brand-new moon (depends on how big and close the moon will be). The long-term consequences should be thoroughly computed before implementing this scheme.   

       [SystemAdmin], I actually tend to think that this is one of those polarized sets of ideas where the truth and/or best solution lies somewhere in the middle. Venus as it is now is TOO unfriendly for EarthLife. But modify Venus some, and modify EarthLife some, and there you go. The same could be reasonable for other worlds, of course.   

       On the other hand, with Venus in particular in mind, the impinging Sunlight has GOT to be reduced, for us to be able to do any living there. So, a SunShield of some sort is going to be needed, regardless -- and space construction is such that if you can do anything in a big way, then the quantity of "big" doesn't matter a lot. Thus the two mirrors I suggested are quite a reasonable and cost-effective way to make Venus more friendly to EarthLife. The most expensive part is likely to be the task of getting rid of all that excess carbon dioxide, since the Idea was to ship multi-teratons uphill against Venus' gravity (not that much feebler than Earth's!). THIS is where modifying EarthLife would be great! All we need is significantly greater tolerance for high concentrations of CO2 in the air. A thick atmosphere (but not 90 times Earth's!) on Venus would be excellent protection from cosmic radiation (since the planet doesn't rotate much, it also doesn't have much in the way of a magnetosphere). Also, thick air would compensate somewhat for the previously-mentioned (in main body of original Idea) temperature problems associated with the orbiting 24-hour day/night mirror. Finally, with both a thicker atmosphere and a little less gravity than Earth, it would be MUCH easier to operate human-powered flying machines there....   

       [DrBob], doing things close to the Sun will be a very valuable thing in the long run (Mercury mines, for example, but what about close-orbiting solar power stations, that beam microwaves to desired spots elsewhere in the solar system?). I submit that there will be enough valuable work to be done there, that the people who do that work will prefer to live and/or vacation nearby. Venus has potential for that, if nothing else.   

       Now I do agree that we should make sure that Venus isn't inhabited by life-as-we-don't-know-it before implementing this project. Fortunately, EarthLife can't survive there now, so we don't have to sterilize any probes we send to look. We should send a decent number of probes to a variety of places on Venus, seeking signs of the collection of traits that makes Life different from mere rock (usual problems of generically defining Life, of course; keep an open mind!). --Oh, and some people have speculated that there may be some microscopic Life-similar-to-what-we-know floating high in Venus' atmosphere, where it is cooler. We have to check that notion out, of course!
Vernon, Feb 11 2004

       //Note that Luna is not really in orbit around the Earth: Both Earth and Luna are actually in orbit around the Sun (the Sun gravitationally attracts Luna twice as strongly as the Earth does);//   

       I have a large issue with this statement. The orbital path of the moon as traced around Earth would be an ellipse. It's orbital path as traced around the sun would be a spiral. I want to know what kind of orbital mechanics would generate a spiral orbit. Also, the moon has been tidal locked to the earth because of the earth's gravitation forces on it. If the sun's gravitational force were so much greater, the moon would be tidally locked to the sun, not the earth.
GenYus, Feb 11 2004

       Heh, I knew somebody would not believe that, about Luna actually being in Solar orbit. See link. The reason Luna's orbit is not a spiral is because it moves too slowly "around" the Earth. The Earth/Luna pair is going around the Sun at over 100,000km/hr, while Luna's independent motion, taking (generous figures here!) 27 days to go "around the Earth", or 2pi-times-375,000km, is only about 5800km/hr. Therefore Luna's orbital motion is ALWAYS proceding along a path around the Sun. OK? Instead of a spiral, think zig-zag (of both Earth and Moon, but the Earth's zig-zag is only a few thousand km, more like a wobble). Another way to deduce Luna's zigzag is to compare the diameter of Luna's "orbit around Earth" (2 times a generous 385,000km) to the circumference of Earth's orbit around the Sun (over 930million km), and think about there are ONLY 13 lunar cycles in one year....   

       About tidal effects, these are very strictly dependent on the different amounts of gravitational force at two separate places in a gravity well. The Sun's tidal effect on the Earth is related to the diameter of the Earth (the "separate places" are the parts of the Earth nearest and farthest from the Sun), compared to its overall distance from the Sun, and of course the mass of the Sun, while Luna's tidal effect is related to the diameter of the Earth compared to its MUCH CLOSER distance (enhanced by the inverse-square law) to the much-less-massive Luna. So Luna has 3x greater tidal effect on the Earth than does the Sun -- and by the same reasoning (but involving Luna's diameter) the Earth has even greater tidal effect on Luna than does the Sun, so Luna is tide-locked to the Earth.
Vernon, Feb 11 2004

       WIBNI there were a catalyst which could reduce the CO2 and let it accumulate as long alkanes? By reduce I mean in both senses of the word! This does not happen on earth, but a very endothermic reaction might be self-sustaining under high temperatures and pressures.
bungston, Mar 21 2004

       bungston, even if there was such a catalyst (and NO, it cannot create alkanes from CO2, since alkanes have a significant hydrogen component), it would only work until some equilibrium condition occurred, in which the oxygen released via catalysis re-attacks the carbon. You will need a way to sequester the oxygen, for as long as there is sufficient energy for the catalyst to do its thing.
Vernon, Mar 22 2004

       Right, no alkanes. You would need to sequester the carbon into diamonds, and hope the oxygen took out is rage on the elements in the crust.
bungston, Mar 22 2004

       Diamonds burn, too, much like coal. How do you suppose they first learned that diamonds were made of carbon? So, you can sequester the oxygen, or you can sequester the carbon, but either way, they cannot be allowed to come into mutual contact at current Venus temperatures, no matter what form the sequestered material takes.
Vernon, Mar 22 2004

       Some big boxes, and a nuclear powered version of maxwell's demon?
RobertKidney, Mar 23 2004

       I'm suspicious that a 15Mm shield at the Sun-Venus L1 point would be large enough to block all light. I think it'll have to be a lot bigger -- did you actually run through the numbers on this?   

       Regarding stability, your general idea is fine, but such a large structure is likely to mass a hell of a lot even if kept very lightweight. And if it's basically a thin foil, as would be practical, it's bound to need a decent bit of repair work over time.   

       Anyway, it might not be a huge issue. Even if you only partially eclipsed the Sun, I think you could have substantial affects on Venus' climate.
cpt kangarooski, Mar 23 2004

       Yes, I was wild-guestimating the size of the Venus/Sun L1 SunShade, mostly because I don't know how far that Point is from Venus. Perhaps it will indeed be larger than 15,000 km in diameter.   

       So, here is a brand-new estimate, based on Earth-viewed solar eclipses. I'll use the following initial figures:
Diameter of Earth: 12,700km
Diameter of Luna: 3400km
Earth-Luna distance: 375,000km
Size of umbra on Earth: 160km
The umbra, of course, is the region of COMPLETE "totality"; if you are within that region, then you see a total Solar eclipse.

       OK, well, there are some simple ratios here; if we want the umbra to completely cover the Earth, then we want it to be increased by 12800/160=80 times -- which in turn means that Luna's diameter would have to be 80*3400=272,000km wide!!! WORSE, the Earth/Sun L1 Point is roughly 1,600,000km from the earth or 1600000/375000=4.27 times the Earth-Luna distance. That means if Luna was shadowing the entire Earth from that L1 Point, its size would have to be even larger, 272000*4.27=roughly 1,160,000km!!!   

       Well, I DO know that the Venus/Sun L1 point is rather closer to Venus than 1,600,000km (due to being closer to Sun and less massive than Earth), but I now seriously doubt that a SunShade at the Venus/Sun L1 Point will be smaller than 900,000km wide....   

       Sorry, folks. Such a size will make the Venus 2.0 makeover rather more expensive. HOWEVER! It remains true that once we acquire the ability to make large structures in Space, there are few limits to the maximum sizes of those structures (self-gravitation being the most likely problem.) A foil SunShade even that large is not beyond the realm of the possible.   

       Next, and regarding the notion of an object's stability at an L1 point, this is actually hardly any problem at all. Consider the basic fact of a Solar Sail: If it works at ALL, then its mass-to-surface-area ratio must be a certain value. This value is INDEPENDENT of the sail's distance from the Sun! (The inverse-square law increases or diminishes BOTH sunlight pressure AND gravitational pull at exactly the same rate with distance!)   

       OK, so at an L1 Point, gravitational effects are largely balanced out by the nearby planet, so ONLY the solar-sail effect need be considered. This will allow a SunShade to have a significantly higher mass-to-surface-area ratio, than for a normal solar sail. (The caveat here is that if the Shade is too large, then some significant fraction of it may extend beyond the region of gravitational balance. On the other hand, the geometry of that region is a large 2-dimensional area, much like the desired SunShade!)
Vernon, Mar 23 2004

       Maybe instead of a solid shade, a cloud of metallic dust could be used. Less prone to damage, easier to create (with explosives and asteroids), and you can add more dust if it starts to disperse.
bungston, Mar 24 2004

       They could be the rings of Venus.
FarmerJohn, Mar 24 2004

       [bungston], a cloud of dust would indeed eventually disperse thanks to the Solar Wind. I'm not sure it would be a good idea to pollute vast amounts of Space while trying to replenish a dust cloud at the Sun/Venus L1 Point. However, if the material of the dust was magnetic, then an appropriate superconducting magnet at the L1 Point might be sufficient to keep the dust from blowing away. (Powerful magnetic fields can indeed be as extensive as a million kilometers.) There would have to be a power plant and a "spray cannon" to keep throwing the dust away from the magnet, so as to keep Shading Venus....   

       Still, there remains the problem of the long long long "day" on Venus, whenever the Sun is directly visible (even if its light is attenuated by a dust cloud). I don't know of any good way except total blockage of direct sunlight, to allow us to THEN give Venus a 24-hour day/night cycle with an orbiting mirror.   

       Perhaps, instead of either a solid SunShade or a dust cloud, we could arrange a "fleet" of ordinary solar sails, dynamically organized to act as if there was a single solid SunShade for Venus. Such a fleet would include redundancies necessary to allow repair of any broken-down unit, while still ensuring complete shadowing of the planet -- and they could be mass-produced, which reduces cost.
Vernon, Mar 24 2004

       If it is too difficult with one large structure to block sun, one can use many smaller instead in orbit, this also has the added bonus of being more fault tolerant. And it would perhaps be easier to regulate the flow of solar radiation (for example, sometime you might want to let through X % of the sun beams to keep the temperature at venus at a certain level).   

       However, my "real" comment is about how we can handle Venus atmosphere. I think it seemes like a huge waste to try to dispence it into space. I recently read about another possible way to do it: the Bosch reaction:   


       This would enable us to reduce the atmosphere to a more manageable volume and as a added bonus give us great oceans. Big oceans are important for creating a stable eco-system (for example, heat regulation, weather, and the fact that all planets loose little water to space every year, which adds up to a lot in a few billions of years).   

       When we terraform Venus we should do it in a way that, after we are done (which maybe take several thousands of years), the system will be stable without human intervention, without sunblockers and such things.   

       Therefore the spinup of venus is important, preferably a faster spin than earth. This can be done in several ways by not using asteroidhits but they take thousands of years - however that is time we got. During this time the planet should be habitable and usefull. (Keep in mind that plants, humans and animals live fine near the poles on earth, where there is a form of short Venus years) - so we can use venus even if the venus-days are 285 earth-days long - as long as the atmosphere is between 0 and 50 degrees, the air pressure is not to high or low, etc. However, we should still focus on finishing the spin up so that future generations can benefit from two planets even if they have lost all our technology.
malu5531, Jul 09 2004

       Old thread -- but, here's something to consider. Man may develop the technology to accomplish some of the things proposed here. But let's be realistic for a moment; man will not seek to undertake such a task unless (1) there is a pressing urgency to do so, or (2) there is a great opportunity to be had by doing so. The pressing urgency might be an attempt by the governments of Earth to save the human race by allowing some portion of the population to escape a cataclysmic event that will affect Earth and not Venus (or somewhere else). A great opportunity might be a scarce resource that a future Earth population may have a serious need for to undertake some endeavor. Either way, given that we are possibly centuries away from the kind of economic and social human cooperation/interest to successfully undertake such a feat, the limiting factors are not just technology, but also cultural.   

       I seriously doubt that humankind would have the foresight to undertake a significant space exploration or terraforming endeavor in the hopes of creating a non-Earthly environment for humans to live. Governments will build bases for short term strategic, scientific-strategic, and bio-strategic reasons -- but probably will never attempt an outright civilian colonization effort on any world as far away from being hospitable as Venus & Mars -- (barring a breakthrough technology such as faster-than-light propulsion, dimensional shifting, etc.) In the latter case, I'm quite sure that a planet exists somewhere in the Milky Way that would be more friendly for colonization than any other planet in our system.   

       Finally, it would seem that introducing bacteria and/or even erecting a sun shield to accomplish atmospheric change would be far more feasible than attempting to increase Venus' speed of rotation, rotational period, etc. I'm not sure human beings will develop such a technology before Sol destroys the Earth. I'm not sure humans will still be around anytime near the point where Earth would become uninhabitable anyway. (Dinosaurs didn't)
senya1, Jul 17 2004

       senya1, Never Underestimate the Greed of Land Developers.
Vernon, Aug 04 2004

       Question - why would it have to be one gigantic screen? Perhaps you could accomplish this better with lots of little screens. Imagine a swarm of large (but not huge) screens between Venus and the Sun. The more screens you have, the greater the solar energy reduction. They could be round or square, or whatever the easiest shape would be to deploy. You could also have some control of the screens with ground (Venus) based lasers. You could push them individually to compensate for solar wind, even push their edges and get them spinning to let through more light. Which brings me to another question. If you could shield the solar energy of 1/2 of Venus, would the other half be enough to spin the planet? In other words, is the solar energy "push" received on half a planet greater than the energy needed to break the tidal lock? I would imagine that by imbalancing the incoming solar energy, you might get spin.
trekbody, Mar 07 2005

       [trekbody], the reason I chose one big screen was due to long-term concerns. If you have a thousand screens carefully avoiding colliding with each other at the vicinity of the Sun/Venus L-1 point, well, if one fails, then how many will it take with it? Meanwhile, one big screen can incorporate ALL the redundancy of those thousand screen...   

       The pressure of sunlight is too feeble to affect Venus' tide-lock.
Vernon, Mar 07 2005

       What, we don't have enough ways to waste our money? </sarcasm>   

shapu, Mar 07 2005

       Knew even before the end that it was a Vernon idea. +
DesertFox, Mar 08 2005

       Never a Vernon idea without an anno about a Vernon idea.
yabba do yabba dabba, Mar 08 2005

       Oh dashit -- the mirror has broken.   

       [entire planet dies].   


       (+) --
britboy, Mar 08 2005

       If cutting the solar energy to half a planet is not enough to break the tidal lock by itself, what if you could switch from side to side, in other words try to spin Venus by "rocking" the sunlight back and forth, sort of like pushing a car out of snow. Would the "rocking" amplify the effect enough to break the tidal lock, seems like you could get there somehow. Might require heavy calculations based on the amount of movement, but putting more and more energy into each "rocking" seems like it would eventually overcome the tidal energy. Could someone (much smarter than I) come up with the numbers? Assuming you could shut off half the planet's solar energy at will?
trekbody, Mar 11 2005

       Thinking about the clouds of Venus - they are shiny. They trap heat below but probably reflect heat from above. Thinking about dust - it is shiny too. Perhaps instead of a foil shield this could be a ginormous inflatable thing? One could inflate it with Venusian atmosphere, or with dust from blowing up handy stuff passing by.
bungston, Nov 09 2005

       Ambitious, but cool.
MikeOxbig, Nov 10 2005

       [trekbody], you may be assured that planets are generally far too massive to be "rocked" as you describe.
Vernon, Nov 10 2005

       Nope...I fish this ...Venus has too much beauty in the sky as it is to be messed with. I love stepping out on my front porch, looing up in the dusking sky and there she is...right above the yellow glowing horizon. She makes me think of Autum and science fiction dog men in space suits and eight legged tulips chasing scantily clad, big busted women. I love Venus as she is.
Blisterbob, Nov 11 2005

       Tulips chasing busty women... tulips chasing busty women. [BB], with you it seems like everything leads to musings about the tulips chasing busty women.
bungston, Nov 12 2005

       While the Bosch reaction is a good idea, that's actually the reason why there *isn't* much water (and lots of CO2) on Venus. Because of the way the atmosphere is heated, it tends to destroy water and vent it out of the atmosphere entirely as hydrogen. The planet needs to be cooled to stop this convection so the reaction would run the other way. All told, the sun shield is probably the best bet. Even if you couldn't completely shade the planet, it might be enough that, due to the high pressures, some of the gases would at least liquify... CO2 liquifies at room temperature (300K) at about 5-10 atmospheres I think. Once the CO2 started condensing at all, the run-away effect of less CO2 -> less greenhouse effect would continue to cool the planet. Then we could leave enough gases to maintain a decent temperature on the shade side, and not need an orbiting reflector.   

       The biggest problem with CO2 in general is that it is the most oxidized form of carbon, and hence has the least amount of energy. In order to convert it to anything else, you have to put in energy, i.e. catalytic conversion simply wouldn't happen. That's why it hasn't been done on Earth to control global warming.   

       Another comment: using meteor impacts to strip atmosphere would be pretty much futile, as you would need pretty much the whole asteroid belt, and each one would sweep away less each time as the atmosphere diffuses... not to mention that some of the meteorite would inevitably vaporize in that thick atmosphere, adding to the problem.
Agamemnon, Apr 04 2006


       Moon - Venus - Mars - Mercury - Interstellar Probe Propulsion   

       1 - Lunar Space Elevator built utilizing the L1 point/Earth Gravitational Balance. -Possibilities/Advantages -Using an NEO (Apophis for example) nudged into position at Lunar L1 or L2 -not necessary, but materials, radiation shielding for station, large industrial base, etc...would be helpful if possible -Perfect Testing Grounds for a Future Earth Space Elevator Technology/Proof Of Concepts -Lunar/L1/L2 Factories Setup Utilizing NEO/Lunar material -Lunar Base/Observatories Possible - Easy and Cheap Lunar Transport -L1 SpaceEl for Earth Related Transport Needs -L2 SpaceEl for Leaving Earth Space for Venus, Mars, Etc. -L2 SpaceEl for Hubble x 100 Observatory - pick out interstellar probe destinations -Time Frame Completion Possible - 15 Years From 2007 ( if we got our butts in gear )   

       2 - Earth Space Elevator - Dependent On Previous Technology/Successful Lunar Testing -Possibilities/Advantages -MUCH cheaper Industrial development of Lunar/High Earth Orbit -Beginnings of Serious Inner solar system development -Some things just cannot be fabricated on Moon/In Space & must be brought up -Time Frame Completion Possible - 25 Years From 2007   

       3a - Begin Production/Deployment of Venusian Solar Shield (Same time as Martian Elevator Construction in 3b) -Possibilities/Advantages -Fully Modular Components - Each ~ 1/2 kilometer in size, square -Semi Autonomous (Mars Rover for Space) -Interlocking Erector Set Style - Can easily remove ANY piece for repair/replace -Multi Tasking - Many Birds With One Stone -Power Generation for Venusian L1 Station (Center of Solar Shield?) -Shield/Cool Venus -Power For System Solar Sail Propulsion Equipped Vehicles in Future -Beginnings For Venusian Space Elevator As Anchor Point -Power For InterStellar Solar Sail Propulsion Equipped Vehicles ( Proxima Centauri in 20 Yrs Anyone?) -Use Diverter to Concentrate/Aim For Solar Sail Propulsion Out of System -Once Venus cooling Complete, Use Modular Design To Regulate Solar Influence -Time Frame Construction/Completion Possible - 45 Years From 2007   

       3b - Construct Martian Space Elevator Construction From Top Of Olympus Mons (in parallel with Venusian Solar Shield -Possibilities/Advantages -Minimize Dust Storm and Avoid Moons -Great Starting Point For Mars Colony -Away From Any Possible Martion Biology Concerns - (although I highly doubt any exist) -Time Frame Construction/Completion Possible - 35 Years From 2007   

       4 - Construct Dual Venusion Space Elevators Through Venusian L1 & L2 Once Venus is cooled off enough -Possibilities/Advantages -Atmospheric CO2 should solidify fairly soon (period of a few years?) given pressue and resulting temperature combinations via adequate solar shield -pressue and temperature will both drop significantly -Base Stations Must Be Movable (Possibly Anchored to a Large Train on Tracks that Circles Venus, Matching Venusian Year Rate -Tracks can double as massive transit system for Venus, bringing supplies/resources/personnel to/from the entire equatorial region -Possibility to Use Trains & Elevators' Tension As a Method to VERY slowly Speed Up Venusian Rotation Rate Over Centuries -May Sound Crazy, but a Small Pull over a long time on a Track That would Circle Venus Might do the trick...we have the power via the solar shield..... -probably far fetched, but a thought anyway- Having two "tugs", L1 and L2, -tension would be additionally used to manage the elevator's stability, recoil issues due to launching, etc. -Other Possibility is simply a large wheeled Transport as Anchors -Provide Additional Benefit of being able to adjust both longitude/lattidue -L2 Space Elevator (Gravitation Swing Point on far side of Venus Relative to the Sun) -Launching Point for Sending frozen C02 to Mars to warm it -clears away CO2 to cool Venus -CO2 Transports From Venus Brought Down Mt Olympus elevator and Released at Optimal elevation -L1 Space Elevator (Near Side of Venus Relative to Sun -Suns Gravity Maintains Stability for Solar Shield As well Once elevator constructed -Launching Pad For Mercury Missions -Great Location for Solar Studies and System Wide Solar Sail Command Structure -From Here, launching of Additional Solar Orbiting Sail Propulsion Systems for Interstellar Travel -Space Elevator Construction By Now Should be A Well Established Art/Science -Time Frame Construction/Completion Possible - 45 and Onward Years From 2007
nrwingate, Jul 12 2007

       Everyone: Just an observation here: It is mentioned early in the article that the the first sunshade would be 15,000 kilometers in diameter. That is only about 3,000 kilmeters wider than Venus' itself. Just how far from Venus is that planet's solar 'L1' point? Why is it necessary to block all of the sunlight? By having a shade that blocks , say, fifty percent, the total solar flux actually reaching Venus is then reduced to the same as Earth's value - without the need to build a seciond reflecting mirror for lighting the planet. One last point, although a sunsghade would be large, it would not neccessarily be massive on a planetary scale. A very thin shade thousands of kilometers in diameter mught only have a mass equal to a small asteroid, though this depends on what it is made of. Moonguy
Moonguy, Oct 24 2007

       [Moonguy], the 15,000km was an estimate, later shown to be erroneous. A Venus-covering shade was intended, from the get-go. It is necessary to block ALL the sunlight in order that the SECOND mirror be able to provide a 24-hour day/night cycle. Simple.
Vernon, Oct 24 2007


back: main index

business  computer  culture  fashion  food  halfbakery  home  other  product  public  science  sport  vehicle