# Could graviton cushions, theoretically, be used for deceleration?

[This is an extension of this Worldbuilding.SE question.]

So, general relativity states that: For example, objects in a gravity-less environment, but in a container accelerating at 9.8m/s^2 (such as a space vessel), would behave like the same objects in an otherwise similar environment on Earth (with a gravitational constant acceleration of 9.8m/s^2).

Another point is the thought experiment of "What would happen if you had a hole that went through the entire earth, then jumped down it?" It's usually answered as "You (or whatever's left of your corpse) would slingshot close to the other end of the tunnel, before falling back to a bit further away from the one you jumped down, then repeat this until you're idly floating at the very center."

Also, theoretical physics describes gravity as being caused by the properties of fundamental particles called "gravitons".

So, with all these in mind, if you had a large group (or lack thereof) of gravitons, could they be used as a deceleration cushion, possibly creating a weightless environment that behaves as if it is filled with a highly viscous fluid?

(And, yes, I've read this question - I'm asking about a full-stop, while gravitational slingshots would pull objects back towards the center of the field given enough time and not enough speed in the right direction. Don't bother asking.)

• Graviton if exists would/might have a precise wavelength similar to light, just like how a tractor beam uses the force carrier of electromagnetic wave (laser) yours is a different kind of force carrier to do work. I never claim you can create a brake out of graviton which propagate at speed of light. Dec 4, 2016 at 6:14
• @user6760 Uh, what? Grammar, please, if you're capable. Dec 4, 2016 at 6:15

No. Gravitons are not a separate thing that can be handled separately from “gravity”. It is simply an expression of second quantization in quantum field theory: just as with a conventional force, the change in momentum caused by gravity must be perceived as all-or-nothing changes that come in a fixed size. See this Answer in the Physics.SE.

The quanta is so small (because gravity is so weak) that you’ll never be able to resolve this with any real experiment. And the force of gravity (and gravito-magnetic effects like frame dragging) invoke virtual gravitons, anyway.

To make an acceleration device (which can catch as well as throw) you need an enormously dense mass, like neutron-star dense, on a torus shape that is spinning like a vortex ring at relativistic speed around the tube radius (not like a wheel). The frame dragging effects will cause an object passing through the hole to be accelerated.

The frame dragging effect can be explained, ultimately, in terms of virtual gravitons. But you really have curved spacetime and a huge mass.

If you had some “real” (not virtual) gravitons, that corresponds to gravitational waves. This causes space to stretch and squish as it passes, and would not impart any kind of lasting acceleration to an object as explained in this topic from February.

That is, interpreting the question in a sensible way makes it identical to “can gravitational waves, if produced on demand, be used as a repulsor beam (opposite of a tractor beam)?”

Think of it as an anology with eletromagnetism: ordinary gravitational attraction corresponds with electrostatic attraction, velocity-dependent effects correspond with magnetism, and both invoke virtual exchange particles in quantum field theory. Real photons is light, and real gravitons is gravitational waves.

If you made some photons, you would have yourself a lamp, not a magnet. And the photons don't exist without them being the light. In the same way, gravitons don’t exist without them being waves of gravitational radiation.

Now light can do all kinds of interesting things, like light sails and optical tweesers, and photons are commonly said to slow down in a transparent medium. But this all happens because of interesting effects between light and electrons. Nothing like that is available with gravitational waves, because ① all stuff responds to gravity the same and ② it doesn’t act as a dipole (quadrupole is the lowest form).

• "never" is a pretty long time, I advise being very careful with using it in context of future experiments. Dec 4, 2016 at 10:04
• I'm not asking to throw things as well, more just, were we somehow able to isolate these particles and arrange them in a certain way, could we theoretically use them to decrease objects' acceleration in a localized area? Whether it's even remotely physically possible to isolate these in such a way is not the question. Whether, were someone to have done so, they would have the indicated affect, is. Dec 4, 2016 at 23:04
• No. Gravitons = gravitational waves. My first paragraph tries to explain that the question is a non sequitor. You cannot “isolate” them—they are gravitational waves. Dec 5, 2016 at 0:12
• I also set a bounty on this question in Physics to draw more attention so it gets answers. Dec 9, 2016 at 7:19