Sciencemadness Discussion Board - Converting thermal energy into kinetic energy... DIRECTLY!

Converting thermal energy into kinetic energy... DIRECTLY!

Cyrus - 14-6-2004 at 15:15

We all know how at high temps, all the atoms in a substance bounce around a lot.

What if there was a way to make them all bounce in the same direction.

Maybe this has already been thought of, I would assume it has, but here's my vague idea.

If anyone has read popular mechanics recently, they will remember some article about getting near absolute zero by using lasers to affect the particles; the lasers are tuned to a certain frequency so that they affect only those atoms that are moving towards them, causing them to stop. When you surround your sample with a sphere of these lasers, any particle moving any direction will be stopped. Almost.

Anyways, what if I took a bunch of these lasers, and aimed them at one side of the mass only, and then suddenly turned them on. Any particles moving towards the lasers would stop, but the other particles would be unaffected. Thus, the average direction of the particles in the mass would be away from the lasers. Now either the mass goes flying through the lab (we will assume it is at a high temperature) or put another bank of lasers on the other side, and when the mass starts flying towards these, turn these lasers on, getting the mass to oscillate back and forth between the lasers. Which could be used somehow. Now that's mad science. Ok, if it was really mad science I would have to try it. But I don't have fine-tuned lasers or a beryllium crystal ( I think that is what they used.)

Problems I can foresee-

-this would be VERY inefficient probably
-maybe it only works at low temperatures
-atoms bouncing to the sides instead of back and forth might be a problem, but a ring of lasers around the crystal might help.

Any comments/suggestions/flames for my stupidity?

The_Davster - 14-6-2004 at 15:27

An intersting idea but the precision of the lasers would have to be very high to keep particle motion in exactly the right direction that you would want. Any gaps in the laser beams would cause loss of effeciency because the particles that are unaffected by the lasers would move in any direction thus lowering the effeciency. The number of specialized lasers needed to even try this even on a very small scale would be high.
Not exactly the type of experiment suited for the amateur mad scientist, more for the university labs with massive government funding.

I would be cool to see a piece of beryllium oscillating in mid air though

Cyrus - 14-6-2004 at 16:19

But wouldn't one large laser beam spread over the whole crystal work-for one side?

Admittedly, the laser would have to be pretty precise.

JustMe - 14-6-2004 at 18:17

Ah, a variant on Maxwell's Demon:

http://www.chem.uci.edu/education/undergrad_pgm/applets/boun...

also:

http://ajs.net/maxwell.htm

Also mentioned in the "Hitchhiker's Guide to the Galaxy" in the form of the finite improbability generator.

The_Davster - 14-6-2004 at 18:26

One large beam on an entire side would probally not work(I might be wrong...) because as you said the beam only stops particles motion when they are moving directly towards them, not if the particles are moving diagonally towards them. The beam would most likely let them continue on their diagonal path( or deflect them slightly, not stop them). Thus you need an array of lasers aiming at the crystall from almost all possible angles. It may very well work with 1 laser per side but it most likely would not work very well, there would be huge losses of effeciency due to particles whose motion is not controlled.

[Edited on 15-6-2004 by rogue chemist]

Cyrus - 14-6-2004 at 21:36

Hmm, I didn't think I was an exorcist.

Seriously, though, I was not trying to achieve perpetual motion, just wondering if the idea would work at all, let alone 100% efficiently.

I don't care how many kilowatts it takes, it would be cool!

I wonder what uses it would have- could you use this technology to get something oscillating back and forth and then release it as a bullet, or use it to power a very inefficient and dangerous spacecraft -
the kind that Tacho would build. Think of how much energy there is in a red-hot lump of iron...

Tacho - 15-6-2004 at 03:37

Quote:

Originally posted by JustMe
(snip)
Also mentioned in the "Hitchhiker's Guide to the Galaxy" in the form of the finite improbability generator.

Excuse me. Just for the sake of scientific precision, wouldn’t that be the “INfinite improbability generator”?

We must know the equipment we work with .

Blind Angel - 15-6-2004 at 06:13

No, i read it too and it's the finite impossibility generator, the kind that allow all the clothes of all girls in a party to get moved one meter away, i want that

JustMe - 15-6-2004 at 16:55

As explained in the a lesser version of the Encyclopedia Galactica:

http://en.wikipedia.org/wiki/Heart_of_Gold

Marvin - 15-6-2004 at 17:44

The most obvios obstruction to the idea working is that if all the atoms moving in one direction stop, and the other continue - giving the block a net velocity, the mass has violated conservation of momentum.

As a 'sanity check' all thermodynamic engines need a heat source and a cold sink to function. The ratio of energy made 'useful' to energy dumped into the cold sink depends on the temperature of the hot and cold sink and is limited by macroscopically unbreakable laws. Anything that claims to break these (for example by not having a cold sink) isnt going to work.

Cyrus - 15-6-2004 at 20:12

But essentially the researchers doing absolute zero got all of the atoms going one direction to stop, but they did it to all sides.

Marvin, what do you think will happen if the lasers are applied to one side only. You say the mass cannot move to one side. What will happen when you turn on the lasers then? Nothing?

I wish I could find the popular mechanics link, it would be very helpful- If someone has it could you post it?

JustMe, I like the links, especially the one with the bouncing particles.

Simple minds, simple pleasures, I know...

Blind Angel you wouldn't really want that.

That's just messed up.

Besides, the clothes would end up intersecting someone else's body sometimes- so when you turned your "happiness" generator on, most of the people would fall into pieces as bloody dribbling messes, because someone else's tee shirt ended up between and bisected their stomach and their ribs.

Edit- now that I think about it, the shirts, etc. might just get lodged in their body without cutting them in half. Not pretty either way.

[Edited on 16-6-2004 by Cyrus]

Geomancer - 15-6-2004 at 21:02

Forgive me for being a bit terse, I just wrote a lengthy and informative post, only to have my browser destroy it because I wasn't logged in. Laser cooling doe work more or less like Cyrus says: you shine a laser (redshifted with regard to the gas's absorbtion) on a gas, and the light is preferentially absorbed by atoms moving towards the laser (they see a blueshift). The atoms reemit in random directions, giving a net blueshift between the light absorbed and that emitted. For practical purposes it's fairly obvious that the energy you spend driving the lasers is enormous compared to that you can extract. Theoreticly, it's quite interesting; perhaps I'll write more when I'm less tired.

unionised - 17-6-2004 at 12:43

This is a somewhat similar idea that you might be interested in.
http://www.anl.gov/OPA/frontiers96arch/wakefield.html
Not exactly amateur science I think.

Cyrus - 17-6-2004 at 21:22

Quote:

Originally posted by rogue chemist
One large beam on an entire side would probally not work(I might be wrong...) because as you said the beam only stops particles motion when they are moving directly towards them, not if the particles are moving diagonally towards them. The beam would most likely let them continue on their diagonal path( or deflect them slightly, not stop them). Thus you need an array of lasers aiming at the crystall from almost all possible angles. It may very well work with 1 laser per side but it most likely would not work very well, there would be huge losses of effeciency due to particles whose motion is not controlled.

[Edited on 15-6-2004 by rogue chemist]

Somehow I can't visualize setting up, calibrating, powering, and controlling 5000 lasers being more efficient than one.

Even if you had one laser, and spread its beam out to cover the whole crystal, there would always be some particles moving directly towards the photons from the laser, so no matter where you aimed from, your laser beam will do its job, and the mass ought to move away.

My latest thought is that this might be useful on the micro or nanoscale, perhaps in some micro-electronic-Cyruslock, or something weird, where it would be used for the fact that the crystal oscillates, and not worry about the efficiency, not for the fact that we now have some extra kinetic energy for Joe's Power Supply, where efficiency is more important.

Any other potential applications?- it's cool stuff. Literally.

And unionized, that wave-generator thing looks like the perfect job for Lestat, maybe we can bribe him to build us one if he is "unbanned".

Sounds Kinda Like Ordinary Diffusion

Chemtastic - 2-7-2004 at 12:38

A concentration gradient has the same characteristics...a net average movement of particles in one direction. It's direct thermal energy into kinetic energy.

Of course, I'm not sure that 5000 lasers are necessary to build the gradient...the human body usually sticks with glucose metabolism

Re: thermal energy directly into kinetic energy

JohnWW - 14-8-2004 at 03:04

How about using a hot-air balloon? The heat expended in getting the balloon, and the cargo it can carry, aloft by buoyancy effectively is conversion to both motion and potential energy.

John W.