Newtons law of gravity states that the attractive force between two masses is represented by F =(G*m1*m2)/r*r, where m1 and m2 are the two masses, r*r (r squared) is the square of the distance between the centers of mass and G is the gravitational constant. G is very small (6.672E-10) which is why to get a gravitational force that we can feel, one of the objects must be very big, like the earth.
Or another way to get some gravitational force is to get m1 and m2 very, very close together. You can see that even if G*m1*m2 is a very small number, as r approaches 0, F gets huge. Big enough to suck some juice out!
Now, I suspect that the reason my fingers are not sticking to the keyboard as I type is that other forces come into play that prevent atoms from getting that close together. Neutrons are neutral, and thus will not be repelled by like charges as would protons, or atoms carrying spheres of negatively charged electrons that bump into and repel each other.
The engine would start with two neutrons held close together. Imagine them at the points of a very large scissors. An explosion as with a piston engine drives the handles of the scissors together, and levers the neutrons very close together. The explosion provides only enough energy to get the neutrons so close that the gravitational force between them is meaningful. As the neutrons draw closer to one another, they carry the handles of the scissors closer together as well. The handles are attached to a gear and it is this stage that captures the energy as the handles are irrevocably pulled by the enormous gravitational forces between the two neutrons. The closer they get, the more force is available!
I am not sure what happens to the neutrons when r=0. Something good, I hope. But they are still useful! They remain stuck to one point of the scissors and the blades are opened again, with a fresh neutron loaded into the empty one. With the next cycle, the force is even greater since the mass on one point is twice what it was.
Eventually enough neutrons would accumulate on the scissors tips that they would need to be cleaned off to start fresh. They might be used to make beautiful jewelry.-- bungston, Nov 21 2004 Pico-assembly http://www.orionsar.../Pi-Pk.html#picofabA quick analysis of working with matter on the neutron-scale. [Chrontius, Nov 23 2004] You don't just find free neutrons. (If you do, you probably have cancer already.) They're very hard to capture and confine, and manipulating single particles of anything to the point of getting them to the points of your machine require inordinate amounts of energy.
The neutrons obey the Pauli exclusion principle just like any other Fermion (electrons, for example). While it's true that they don't have mutual electrostatic repulsion, they do experience both the electromagnetic force and the strong nuclear force, by way of their quark constituents. Getting them close together would probably cause them to bind, or "slip" past each other, or recoil from each other.
For the neutrons to be close enough for the gravitational effect to be meaningful, they would be close enough for the other three forces to be several orders of magnitude more significant. Gravity is almost always neglected when looking at particle processes, as it is completely - well, negligible. There's also the fact that the uncertainty principle doesn't allow them to get that close; and in fact causes the word "close" to lose all meaning.
In short - energy required to set up machine: vast. Effect of using neutrons instead of electrons: little. Energy obtained: miniscule.-- Detly, Nov 22 2004 You work for Mobil, don't you [Detly]? Fessup! You just want to stoke our addiction to petropower!-- bungston, Nov 22 2004 as r approaches zero... Force might be huge, but distance will be negligible, and thus energy released would be tiny.-- david_scothern, Nov 22 2004 Mobil? Ha ha – I laugh at such a preposterous notion... um... [nervous glance, picks up phone, calls Mobil(r) Hired Goons(tm)]
([UB] - not quite, but getting ever closer.)-- Detly, Nov 23 2004 Just make the back wheels bigger than the front wheels: then the car is always going downhill!! Instant gravitational engine. ;)-- not_only_but_also, Nov 23 2004 [UB] - not for at least another year, and possibly as long as another three. But I've just – a few days ago – finished the essential requirements of a basic, rudimentary Piece of Paper. Everything I do now is just for more letters afterwards, or possibly before. :P-- Detly, Nov 23 2004 I'd like an Evil Genius title one day, but at the moment I'm only at the Moderately Unbalanced and Fairly Resourceful level.
Mwuahaha.-- Detly, Nov 23 2004 The problems with the resulting neutronium you'd be producing are many. Let's see...
1) Neutronium is theoretically unstable, and when it decompresses... well, you could fit a Hiroshima nuke in a bomb the size of a red blood cell.
2) Neutronium is damn dense, a teaspoon weigh like a ton or something.
Similar energies could be obtained from fusion, with a much lower investment in R&D.-- Chrontius, Nov 23 2004 When I was at university, one of my physics profs mentioned once that he had never been able to figure out why anti-gravity by induced reverse precession would fail, but he was sure it would.-- raytork, Nov 23 2004 I would like to hear more about this induced reverse procession. It sounds formidable.-- bungston, Nov 23 2004 totally impossible and based on misunderstanding of physics, but in a creative way. bun.-- sninctown, Apr 07 2006 random, halfbakery