# Moving Earth's orbit or other means of climate change? **URL:** \ **Category:** Factual Questions\ **Created:** [November 28, 2010, 6:02pm UTC](https://boards.straightdope.com/t/moving-earths-orbit-or-other-means-of-climate-change/562182 "2010-11-28T18:02:30Z")\ **Posts on this page:** 13\ **Page:** 3
**Author:** ![sylvernight](https://avatars.discourse-cdn.com/v4/letter/s/dec6dc/32.png) [@sylvernight](https://boards.straightdope.com/u/sylvernight)\ **Post date:** [November 29, 2010, 10:12pm UTC](https://boards.straightdope.com/t/moving-earths-orbit-or-other-means-of-climate-change/562182/41 "2010-11-29T22:12:07Z")
Okay, here’s my problem–I am not normally a science fiction writer, but I happened to write a story set in the not-too-distant future where somehow humanity has done something to mess up the global climate, and most of the planet is a desert. One of my beta readers said she needs more background for this vision of the future to be believable, so I’m trying to fill in the details. I’d like to imply that this climate shift is the (accidental) result of people messing with things they shouldn’t–too much pollution with no thought of the environment, too much industrial waste, etc. I (apparently naively) thought moving earth’s orbit would work, but I really want something that would have a more immediate effect, as opposed to requiring thousands of years. Stranger, I looked up the L1 libration point, but I’m still lost by what you mean. Or were you making a joke? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [November 29, 2010, 10:38pm UTC](https://boards.straightdope.com/t/moving-earths-orbit-or-other-means-of-climate-change/562182/42 "2010-11-29T22:38:15Z")
**Stranger** was serious, but it wouldn’t help you. Basically, the L1 point is a point between the Earth and the Sun, so if you put a big parasol there, it would decrease the amount of sunlight the Earth would get. This would be one way to counteract excessive heat of some sort. But it won’t _increase_ the amount of heat, which seems to be what you’re looking for. Be advised that if you do use the greenhouse effect as the cause, then your book will be regarded as a book about the greenhouse effect, instead of just being a generic book about a desert wasteland. ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [November 29, 2010, 10:55pm UTC](https://boards.straightdope.com/t/moving-earths-orbit-or-other-means-of-climate-change/562182/43 "2010-11-29T22:55:12Z")
> [@sylvernight](#): > > Stranger, I looked up the L1 libration point, but I’m still lost by what you mean. Or were you making a joke? As **Chronos** notes, the L1 point is the point of neutral gravitation between the Sun and the Earth. An object placed there, protected against perturbation, will remain in the same relative location, orbiting at the same rate as the Earth about the Sun. You would need a large keel to maintain orientation, and likely some kind of stationkeeping propulsion system as small gyrations in the position (owing to influences of other planets on the Earth) will otherwise eventually cause the object to be ejected. This is conceptually feasible. **Chronos** is correct that it can only shield, not increase solar incidence (although I suppose you could make a gigantic fresnel lens focused on the Earth), although I can’t think of why you’d do something like this on accident. It sounds like more of a fiendish plot by a would be villain. Stranger ---
**Author:** ![sylvernight](https://avatars.discourse-cdn.com/v4/letter/s/dec6dc/32.png) [@sylvernight](https://boards.straightdope.com/u/sylvernight)\ **Post date:** [November 29, 2010, 10:55pm UTC](https://boards.straightdope.com/t/moving-earths-orbit-or-other-means-of-climate-change/562182/44 "2010-11-29T22:55:25Z")
> [@Chronos](#): > > Be advised that if you do use the greenhouse effect as the cause, then your book will be regarded as a book about the greenhouse effect, instead of just being a generic book about a desert wasteland. Grr, and that’s what I’m trying to avoid. The story is about a high school student who wasn’t even alive when everything changed, so–like most young people–she doesn’t know/care much about how things were before. The focus is supposed to be on her, but I still need some kind of background for what caused the change, even if only to show how bored she is when she has to read about it in science class. ---
**Author:** ![XT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/xt/32/456_2.png) [@XT](https://boards.straightdope.com/u/XT)\ **Post date:** [November 29, 2010, 11:26pm UTC](https://boards.straightdope.com/t/moving-earths-orbit-or-other-means-of-climate-change/562182/45 "2010-11-29T23:26:36Z")
[QUOTE=Stranger On A Train] The propulsion system and propellant (tens of thousands of bomblets) would have to be delivered to the moving object via some conventional means, i.e. chemical rockets to lift it off the surface of the Earth and nuclear pulse propulsion to delivery it to rendezvous with the object. (Alternatively, you could establish a permanent manufacturing infrastructure and manned presence in space to mine, produce, assemble, and deliver the necessary components, at a cost of untold trillions of dollars.) All of this would have to be repeated on a periodic (presumably annual, or semi-annual) basis. [/QUOTE] Sort of a brute force approach isn’t it? If we assume long time frames, why couldn’t you simply park a space craft near the intended asteroid so that it would maintain just enough thrust to slowly drag the object into another orbit (ETA: Something like [this](http://www.space.com/businesstechnology/051109_asteroid_tractor.html))? Then you could use that object to effect the path of the Earth over time by periodically shifting it’s orbit such that it would effect the orbital mechanics of the Earth. Like Der Trihs, I’ve seen this sort of thing mentioned on the Science Channel as possible ways to change the orbits of asteroids that may be on collision courses with the Earth (I think that Michio Kaku mentioned using this on one of his Sci-Fi Science episodes). Given hundreds or thousands of years (or even 10’s of thousands), I don’t think that it would be impossible given our current technology. The only thing I can think of that may be a show stopper is how to provide continual thrust to the space craft, but you could possibly get around that by simply periodically changing them out or refueling (granted for thousands of years). I don’t see why we would WANT to expend those sorts of resources on changing the Earths orbit over those sorts of time frames, but I know of nothing that makes it impossible for us to do this today, given the desire to expend the resources for ridiculously long periods of time. -XT ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [November 29, 2010, 11:58pm UTC](https://boards.straightdope.com/t/moving-earths-orbit-or-other-means-of-climate-change/562182/46 "2010-11-29T23:58:14Z")
> [@sylvernight](#): > > Grr, and that’s what I’m trying to avoid. The story is about a high school student who wasn’t even alive when everything changed, so–like most young people–she doesn’t know/care much about how things were before. The focus is supposed to be on her, but I still need some kind of background for what caused the change, even if only to show how bored she is when she has to read about it in science class. That being the case, trying to explain what happened kind of violates the point (assuming that the story is being told from the perspective of your protagonist). If it is immaterial to the plot, you don’t need to explain the details, any more than we care why the destruction of the energy facility on Praxis threatens the Klingon homeworld. (Oh bog, I can’t believe I just make a _Star Trek_ reference.) > [@xtisme](#): > > I don’t see why we would WANT to expend those sorts of resources on changing the Earths orbit over those sorts of time frames, but I know of nothing that makes it impossible for us to do this today, given the desire to expend the resources for ridiculously long periods of time. Because this is all handwaving. It throws around ideas about gravity tractors and moon-sized swing-by momentum transfers without any quantitative assessment. When you start putting actual numbers to it you begin to see just how improbable it is. We’re not talking in terms of thousands or tens of thousands or even millions of years; we’re talking billions of years to make a significant change, by which time both the climate of the Earth and the solar output will have changed, and if the human species has survived it is unlikely to still be dependent of living upon the surface of a delicate planet anyway. No existing or conceptual technology based upon known physical science is going to move large orbiting bodies around like playing celestial billiards. For that, you need indistinguishable from magic technology. Stranger ---
**Author:** ![XT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/xt/32/456_2.png) [@XT](https://boards.straightdope.com/u/XT)\ **Post date:** [November 30, 2010, 12:41am UTC](https://boards.straightdope.com/t/moving-earths-orbit-or-other-means-of-climate-change/562182/47 "2010-11-30T00:41:47Z")
And yet, the two astronauts in the linked article think it’s at least plausible to move large objects in space and shift their orbits. You dismiss but you do so by simply saying it’s impossible without going into any details. Perhaps to you, a rocket scientist IIRC, it IS that simple and obvious, but to me (a not rocket scientist) it seems plausible though very difficult and resource/time intensive. -XT ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [November 30, 2010, 12:50am UTC](https://boards.straightdope.com/t/moving-earths-orbit-or-other-means-of-climate-change/562182/48 "2010-11-30T00:50:12Z")
> [@xtisme](#): > > And yet, the two astronauts in the linked article think it’s at least plausible to move large objects in space and shift their orbits. You dismiss but you do so by simply saying it’s impossible without going into any details. I’ve gone into [POST=13191433]extensive quantitative detail on the difficulties[/POST]. Stranger ---
**Author:** ![XT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/xt/32/456_2.png) [@XT](https://boards.straightdope.com/u/XT)\ **Post date:** [November 30, 2010, 12:52am UTC](https://boards.straightdope.com/t/moving-earths-orbit-or-other-means-of-climate-change/562182/49 "2010-11-30T00:52:47Z")
Thank you. I appreciate you fighting ignorance on a subject that you have a special level of knowledge about. I like to know WHY the stuff I see on places like the Science Channel are wrong, incorrect or exaggerations. Besides, the subject interests me. -XT ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [November 30, 2010, 1:15am UTC](https://boards.straightdope.com/t/moving-earths-orbit-or-other-means-of-climate-change/562182/50 "2010-11-30T01:15:25Z")
> [@xtisme](#): > > I like to know WHY the stuff I see on places like the Science Channel are wrong, incorrect or exaggerations. Because the Discovery/Science Channel produces entertainments that emphasize the cool over the practicable. Stranger ---
**Author:** ![Grey](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Grey](https://boards.straightdope.com/u/Grey)\ **Post date:** [November 30, 2010, 1:35am UTC](https://boards.straightdope.com/t/moving-earths-orbit-or-other-means-of-climate-change/562182/51 "2010-11-30T01:35:25Z")
Well there’s also the fact that they’re discussing moving 100m objects and not 100km “moons”. ---
**Author:** ![Omphaloskeptic](https://avatars.discourse-cdn.com/v4/letter/o/bcef8e/32.png) [@Omphaloskeptic](https://boards.straightdope.com/u/Omphaloskeptic)\ **Post date:** [January 2, 2011, 9:29pm UTC](https://boards.straightdope.com/t/moving-earths-orbit-or-other-means-of-climate-change/562182/52 "2011-01-02T21:29:55Z")
I know this is kind of a nitpick for a month-old thread, but it does change the answer by five orders of magnitude. (At least the long timescales mean that a month is negligible.) > [@Stranger\_On\_A\_Train](#): > > A 100 km diameter object has a volume of 7.85 x 10[sup]9[/sup] m[sup]3[/sup]. If it has a density similar to Earth’s Moon (3.3464 g/cm[sup]3[/sup]) then it will have a mass of 26.3 x 10[sup]12[/sup] kg. You calculated the volume by pi r[sup]2[/sup]; it should be (4pi/3) r[sup]3[/sup], for a mass of about 1.8 x 10[sup]18[/sup] kg. It appears that you used this mass in your calculations for momentum transfer to the Earth, meaning the planetary-engineering timescales are also off by about five orders of magnitude, being more in the range of millions to tens of millions of years instead of trillions. Of course, you also used it in the requirements for changing the object’s orbit, so that gets correspondingly harder. > [@](#): > > If we are to assume that it is moving somewhere in the vicinity of Earth’s orbital speed (as it will have to be in order to m ake maximum effect of momentum transfer via gravitational swing-by) it will be moving at ~29.8 km/s, giving it a kinetic energy of 1.17 x 10[sup]13[/sup] GJ. To make a 1% change in any orbital characteristic would take about the equivalent of 28,000 megatons TNT, comparable to the total yield of all nuclear weapons produced by the major powers during the height of the Cold War, and the use of nuclear devices is the only feasible way to deliver and apply such energies to a moving celestial body. Applying this amount of impulse in some fashion without fracturing the object into fragments would require some kind of damped or buffered system which would distribute the impulse evenly across the surface and over an interval of time sufficient to allow stresses in the body to equalize before reaching shear limits. Such a damping system, based on something akin to the Project ORION pusher plate concept, with a maximum efficiency in the 10% range. As **Chronos** pointed out it seems more reasonable to do the momentum transfers at aphelion (off in the Oort cloud, say), where the orbital velocities are on the order of 500 m/s. This brings the energy scales back down to about what you originally calculated (actually an order of magnitude more, 2 x 10[sup]14[/sup] GJ). Of course this means getting all of the equipment out there in the first place, a big project in itself. > [@](#): > > […] > > All of this would have the effect of transferring a fraction of the difference in momentum between the two bodies (at most twice the difference in relative momentum between the Earth and the object; in practice, significantly less). Since the difference in momentum is proportional to the masses, the gain factor for impulse transfer would be proportional to the ratio of masses, or Q=-113.6. This means to make a 1% change in Earth’s orbital characteristic and 100% transfer of relative momentum will take somewhere on the order of 2000 billion years, assuming you can perform a transfer maneuver twice per solar orbit. By this time, not only is the climatosphere of the Earth no doubt changed, the Sun itself has long turned into a greenish-white dwarf star. > > None of this of course accounts for the fact that the close approach by a large body will cause huge seismic stresses that are likely to cause or amplify tectonic and volcanic activity, which is likely to cause more ultimate destruction than transitory climate change. The tidal effects on Earth can be reduced by moving the object’s closest approach outward, at the cost of reduced momentum transfer. Lunar-level tides are achieved if the closest-approach distance is around 10000 km (though I don’t know how the tidal effects from such a fast-moving body would compare to those of the moon). Assuming the object is dropped from beyond Neptune, its speed at Earth is around 42 km/s, but the actual delta-vee for this approach distance will be only around 1.7 km/s for the object and 0.5 mm/s for the Earth. (But you might want to increase perigee anyway, since Earth’s Roche limit is around 10000 km — who wants the headaches of collecting all of the pieces after each pass?) So this gives a rough count of (30 km/s) / (0.5 mm/s) = 60 million passes to make major changes in the Earth’s orbit; at about one per year this is still very long on human timescales, but at least it’s short on Solar System timescales. > [@](#): > > In short, not feasible nor desirable with any extant or conceptual technology. > > Stranger Agreed on the feasibility; desirability depends on the alternatives, I guess. ---
**Author:** ![BlinkingDuck](https://avatars.discourse-cdn.com/v4/letter/b/eada6e/32.png) [@BlinkingDuck](https://boards.straightdope.com/u/BlinkingDuck)\ **Post date:** [January 3, 2011, 6:19pm UTC](https://boards.straightdope.com/t/moving-earths-orbit-or-other-means-of-climate-change/562182/53 "2011-01-03T18:19:40Z")
> [@sylvernight](#): > > Okay, here’s my problem–I am not normally a science fiction writer, but I happened to write a story set in the not-too-distant future where somehow humanity has done something to mess up the global climate, and most of the planet is a desert. One of my beta readers said she needs more background for this vision of the future to be believable, so I’m trying to fill in the details. > > I’d like to imply that this climate shift is the (accidental) result of people messing with things they shouldn’t–too much pollution with no thought of the environment, too much industrial waste, etc. I (apparently naively) thought moving earth’s orbit would work, but I really want something that would have a more immediate effect, as opposed to requiring thousands of years. > > Stranger, I looked up the L1 libration point, but I’m still lost by what you mean. Or were you making a joke? Just have the sun suddenly spike a little in luminosity…or is that outlandish? [Previous page](https://boards.straightdope.com/t/moving-earths-orbit-or-other-means-of-climate-change/562182.md?page=2)