# Gravity in space... **URL:** \ **Category:** Factual Questions\ **Created:** [April 24, 2011, 6:04pm UTC](https://boards.straightdope.com/t/gravity-in-space/579571 "2011-04-24T18:04:31Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![komolono](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/komolono/32/532_2.png) [@komolono](https://boards.straightdope.com/u/komolono)\ **Post date:** [April 24, 2011, 6:04pm UTC](https://boards.straightdope.com/t/gravity-in-space/579571/1 "2011-04-24T18:04:31Z")
There seems to be awful lot of energy in orbit. Can you use it to produce gravity? That is, can you spin something without emision of particles? ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [April 24, 2011, 7:22pm UTC](https://boards.straightdope.com/t/gravity-in-space/579571/2 "2011-04-24T19:22:37Z")
I honestly can’t make heads or tails of your question. Can you elaborate about the energy and how spinning will produce gravity? And what does something not emitting particles have to with gravity? ---
**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\ **Post date:** [April 24, 2011, 7:41pm UTC](https://boards.straightdope.com/t/gravity-in-space/579571/3 "2011-04-24T19:41:10Z")
I think the OP is asking whether or not you could use the gravity between astronomical bodies to spin or otherwise move something in space as an energy source. Using gravity alone with no reaction drive, thus “no particles”. Like drawing energy from the Earth/Moon system. I’m not sure what’s meant by “produce gravity” though. Centrifugal force? ---
**Author:** ![Arkcon](https://avatars.discourse-cdn.com/v4/letter/a/96bed5/32.png) [@Arkcon](https://boards.straightdope.com/u/Arkcon)\ **Post date:** [April 24, 2011, 8:41pm UTC](https://boards.straightdope.com/t/gravity-in-space/579571/4 "2011-04-24T20:41:26Z")
Obviously, a great deal of “work” is being done in space, moving large massive objects, like planets, a great distance. But there’s the problem, the motion is spread out over a large distance, so it’s so diffuse, we can’t in a practical way, catch it. Here’s a more down to earth (heh) method – using the forces of the tides. Earth’s moon moves the entire ocean, free of charge, but only some places, is the coastline so perfect that we can try to tap it – with considerable engineering difficulty. Notice, we use the ocean as a way of catching the energy of the moon. > **[Tidal power](https://en.wikipedia.org/wiki/Tidal_power)** > > Tidal power or tidal energy is harnessed by converting energy from tides into useful forms of power, mainly electricity using various methods. > Although not yet widely used, tidal energy has the potential for future electricity generation. Tides are more predictable than the wind and the sun. Among sources of renewable energy, tidal energy has traditionally suffered from relatively high cost and limited availability of sites with sufficiently high tidal ranges or flow velocities, thus constricti... ---
**Author:** ![Andy\_L](https://avatars.discourse-cdn.com/v4/letter/a/c67d28/32.png) [@Andy\_L](https://boards.straightdope.com/u/Andy_L)\ **Post date:** [April 24, 2011, 8:57pm UTC](https://boards.straightdope.com/t/gravity-in-space/579571/5 "2011-04-24T20:57:52Z")
> [@komolono](#): > > There seems to be awful lot of energy in orbit. Can you use it to produce gravity? That is, can you spin something without emision of particles? I also am having a hard time figuring out quite what you mean, but if you put a long thin object in orbit, it will tend to line up pointing to the object it’s in orbit around, rotating (relative to the stars) once per orbit - this is a method used to stabilize satellite orientations (for low-Earth orbit, mostly). The spin, in combination with the tides will produce a small amount of pseudogravity inside the object. See David Brin’s story “Tank Farm Dynamo” for a fictional account of how that works. You can use the gravity of the planets to propell small objects around the solar system with arbitrarily small amounts of rocket power, if you’re willing to wait a very long time - see this article [Interplanetary Transport Network - Wikipedia](http://en.wikipedia.org/wiki/Interplanetary_Transport_Network) ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [April 24, 2011, 10:02pm UTC](https://boards.straightdope.com/t/gravity-in-space/579571/6 "2011-04-24T22:02:27Z")
> [@komolono](#): > > There seems to be awful lot of energy in orbit. Can you use it to produce gravity? That is, can you spin something without emision of particles? Not sure I quite understand the whole question, but the graped part looks like you’re asking whether something can be set spinning in space without applying reaction motor-type thrust. The answer is yes; if you have a spacecraft with a big flywheel in it, when you spin up the flywheel, the rest of the craft will spin in the opposite direction. If you brake the flywheel to a stop, the craft will stop spinning. (or you could design it as two wheel-type space stations, joined on the same hub - and you can spin one in the opposite direction to the other entirely in isolation from external systems) ---
**Author:** ![komolono](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/komolono/32/532_2.png) [@komolono](https://boards.straightdope.com/u/komolono)\ **Post date:** [April 25, 2011, 2:52am UTC](https://boards.straightdope.com/t/gravity-in-space/579571/7 "2011-04-25T02:52:36Z")
Sorry, if I was unclear with my OP, but **Mangetout** nailed it. So, you can use ie. solarpower to make electricity and magnets to revolve space objects, but how about moving forward? I quess you could use centrifugal force to “slingshot” objects and the space stations would move, but you would be losing mass. Any ways not to lose mass while moving? ---
**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:** [April 25, 2011, 2:58am UTC](https://boards.straightdope.com/t/gravity-in-space/579571/8 "2011-04-25T02:58:02Z")
> [@](#): > > Any ways not to lose mass while moving? Nope, those pesky Newton’s Laws will get you every time. Or rather, you can _move_ without losing mass, but you can’t _accelerate_ without losing mass. ---
**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\ **Post date:** [April 25, 2011, 4:07am UTC](https://boards.straightdope.com/t/gravity-in-space/579571/9 "2011-04-25T04:07:02Z")
> [@Chronos](#): > > Nope, those pesky Newton’s Laws will get you every time. Or rather, you can _move_ without losing mass, but you can’t _accelerate_ without losing mass. Well, no, not as I understand it. There’s solar sails and spinning tethers as methods to accelerate without expending mass. Magnetic sails, arguably; it depends on whether or not slowing down the solar wind counts as “losing mass”, since none of it is from your ship. You can also use magnetism to lower or raise your orbit if the planet has a magnetic field; while that would impart a _tiny_ amount of momentum to the planet, in practical terms no mass would be lost. ---
**Author:** ![komolono](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/komolono/32/532_2.png) [@komolono](https://boards.straightdope.com/u/komolono)\ **Post date:** [April 25, 2011, 6:04am UTC](https://boards.straightdope.com/t/gravity-in-space/579571/10 "2011-04-25T06:04:12Z")
Although I started with a space theme, this is just another photon question. Sorry about it. A spinning electron - can it emit photons without losing its mass?