Gyroscope Puzzle

OK, say it's spun up with a motor and power is delivered to the motor, if necessary, to keep the gyro rotating at a constant rate. Deduct this power from the power delivered by the moving gyroscope housing.

The energy needed to keep the gyroscope spinning will always be equal to the energy extracted plus losses to entropy.... Where would the energy come from, since energy cannot be created nor destroyed, the energy must come from the rotation of the Earth...You would have to harvest the kinetic energy of the Earth and convert it to mechanical energy....It would be a challenge to try, but much like perpetual machines everywhere, a fool's errand....

I think you'd be better off praying for those miracles.

You could throw it in space and it will keep spinning.

I'm not sure how you extract rotational energy from the Earth since you and the gyroscope and the gearing are all travelling with the Earth.

To put it another way, an super-intelligent ant riding along on the rim of a bicycle wheel can't slow down the wheel to extract any energy from it. The wheel can only be slowed down by an outside force, i.e., a generator attached to the fork that's holding the wheel.

If you mounted your gyroscope and motor system at the North Pole, you could slow down the rotation of the Earth by spinning-up the gyrosope with its rotation in the same direction as the Earth's spin. But the net angular momentum must be conserved. I don't see that as extracting any useful energy.

Exactly!

Energy extracted from this gyroscope comes from the energy stored in the gyroscope. The motor would be replacing that energy. As soon as you impede it to extract energy you slow it down because you are changing its angular momentum.

For the earth to slow down, angular momentum has to go somewhere, and like you say, the gyroscope is part of the earth.

In the case of tides, angular momentum is transferred to the orbital motion of the moon.

GA

Maybe you could mount the device on the Moon....steal back that energy....

But if you steal angular momentum from the Moon, would that make it approach or recede from the Earth? (Serious question, I don't know the orbital mechanics formulas well enough to find the answer myself.)

Either way it's bad, as losing the moon means we lose the tidal energy we get from it, which would completely bork the Earth's ecosystem even worse than Human-Produced Global Warming, and the Moon falling in towards the Earth will be ... Well, they've already made movies about similar events, any one remember the old film When Worlds Collide?

But if you steal angular momentum from the Moon, would that make it approach or recede from the Earth? (Serious question, I don't know the orbital mechanics formulas well enough to find the answer myself.)

Angular momentum of moon is proportional to square root of distance (see below for derivation)

The tidal bulge on the earth leads the direction to the moon because the earth rotates in the same direction as the moon's orbit (only much faster) and friction drags the tidal bulge ahead. As a result, the direction of the gravitational force of the earth on the moon is very slightly ahead of the direction of moon to earth. This tiny difference over long periods causes angular momentum to be transferred from the rotating earth to the earth-moon system. Over time, the earth's rotation slows and the moon moves into a higher orbit with more angular momentum.

http://physics.stackexchange.com/questions/134625/conservation-of-angular-momentum-in-earth-moon-system

If the earth were rotating in the opposite direction, the tidal bulge would lag the moon's direction. If this were the case the earth's rotation would slow down as before, but the moon's orbit would descend. Angular momentum would be transferred from the moon to the earth's rotation. The difference in this case is that the angular momentum vector of the rotating earth is in the opposite direction, so if the angular momentum vector of the earth-moon were considered positive, the earth's rotation angular momentum would become less negative.

Angular momentum of moon is proportional to square root of distance

centrifugal acceleration = gravity acceleration:

v^2/r = k/r^2 or v^2 = k/r or v=sqrt(k/r)

Angular momentum = mass x velocity x radius =

mass * sqrt(k/r) * r = mass * sqrt(k*r)

Ah, so in laymen's terms, the Moon is currently GAINING angular momentum at the cost of the Earth losing angular momentum, which is slowing the Earths Rotation and moving the Moon's orbit further out.

Which would mean that the poster with the idea to take energy from the Moon would cause it to 'fall in' towards Earth, smashing up the place.

Thanks for the info, now I know what scenario to use when someone talks about 'harvesting' the energy from the Moon's orbit.

It's not just theory, it's been measured over the last 35 years using lasers, telescopes, and retroreflectors left on the moon. The result is that the moon is moving away at about 3.8 cm per year.

https://en.wikipedia.org/wiki/Lunar_Laser_Ranging_experiment

Harvesting that energy would only stabilize the orbital velocities...

Stabilize how? Would that make the Earth 'tide locked' to the Moon, as the Moon now is to the Earth? That would change the tides from a dynamic phenomena to a static one. No changing tides, planetary ecosystem gets thrown out of wack. Still not a good scenario.

Nothing would change....

Now I'm confused. let me state things as I understand them:

• The current system is one where the Earth is losing Angular Momentum to the Moon.
• This is causing the Earth to slow its revolution, and causing the Moon to recede.
• The 'wild idea' being discussed is somehow (through means yet to be determined) to 'harvest' energy from the Moon's Angular Momentum. This would cause the Moon to lose Angular Momentum to the (undescribed) energy harvester.
• If the energy harvested is less than the energy the Moon takes from the Earth, The Moon would continue to recede, but at a slower rate.
• If the energy harvested is equal to the energy the Moon takes, it would cease recedeing.
• In the energy harvested is greater than the energy the Moon takes, it would begin drifting in towards the Earth.

In all of those scenarios, something is changing. Extracting energy from a system without the system showing any change would be the definition of a Perpetual Motion Device/Free Energy Maker.

Nothing we can do will make much difference in the moon's orbit getting slightly higher and the earth's rotation slightly slowing down, and it is of scientific interest only. It is a non-problem. At the present rate, it would take 105 million years for the distance to the moon to increase by one percent.

However, associated with this angular momentum transfer, there is a lot of energy from the tide washing in and out from the shorelines. Whether it is lost to friction or used for tidal power stations might make a tiny bit of difference, but not much. What we can do is capture for our use some of this energy that is presently going to waste, much like damming a river for hydroelectric plants.

Whether we want to do this depends on the economics. Like other alternate energy sources, the energy is free but the infrastructure is not, and it has to be figured into the cost.

Where's Tommey Reed?? I'm sure he's tried this!!

I am visioning this at a pole as well, with the axis of the Gyro perpendicular to Earth axis, not coaxial. Start 'er up, let the Earth spin under it, harvest the one rev/day spin.

I see this as not a 'Free-Energy' device, but a 'Free-Energy-To-Me' device. Momentum is there, this is just a way to steal some of it.

I could see this working. It might work when installed in some parallel universe where there are no friction and no losses.

I've thought about this for some time. (BTW, I was considering the gyro axis perpendicular to the earth's axis and should stated that originally.)

To get energy from the rotating earth, slowing it down, you have to change its angular momentum. You can't do that from on the earth any more than making a car go faster by pressing on the dashboard. Angular momentum has to be conserved, so if the earth's angular momentum changes, it has to go somewhere.

Tides simply move angular momentum from the earth's rotation to the earth-moon orbital angular momentum, dissipating some energy in the process. As the spinning earth slows down, the moon gets slightly farther from the earth.

It is necessarily wrong:

"....Suppose you had a giant gyroscope..."

'giant' doesn't put much of a limit on its size and there is no mention of how fast it is turning....

"....and had it mounted so that as it moved (with respect to the earth)...."

or as the Earth turns with respect to it...

"....in response to the earth's rotation, a series of gears were used to extract energy....."

".... (You can neglect bearing friction.) Could you use this means to get energy from the earth's rotation?...."

.

Let's take it to an extreme and say the magnitude angular momentum of our giant gyroscope exceeds that of the Earth. The gyroscope is at a pole. The axis of rotation is shared but turn in opposite directions.

It seems very straight forward now to 'use a series of gears to extract energy from the rotation of the Earth', until the earth has stopped rotating with respect to the giant gyroscope.

Using a different location for the gyroscope and even having significantly less angular momentum doesn't mean energy would no longer be recoverable. A gimbaled gyroscope is actually freer from the Earth than the moon. The moon is tidally locked.

Hum, I was taught the moon was tidally locked to the earth. I guess we learn something new everyday, huh?

Oops, my bad, I was down under when I heard that

Yeah...to the Earth. What did I write that is confusing?

Nothing, it's Friday the Thirteenth and thought I'd toss in a little humor

Not sure if this has been raised above? But my thoughts are; a gyroscope spins around its axis, which I will refer to as its true axis, and any applied force acts in a direction of an implied axis? And you will note mathematically, that the true axis moves towards the implied axis of the applied force? So applying this fact to or question, will it provide a source of energy? No it will not, because the point of attachment will apply a reactive force, and that force is being created by its attachment to the earth, so the implied axis will be aligned to the earths axis, and as the actual axis moves towards the implied axis the new axis will align to the earth, and therefore become neutral.

Whatever you do to spin the gyro up to speed will cancel out in advance whatever you do later to slow it back down. (This is just another way to make a point that has already been made.)

Consider this scenario about conservation of momentum:

You place a "U" shaped tube in free space,with both ends of the tube closed.

At the very center of the tube,(centered from both ends and from each sidewall),you have 2 equal masses,and in the center of the masses,you have an electronically triggered device that can propel each mass in opposite directions,with equal force.

Consider further that the masses are magnetically restrained from touching the walls of the tube,and that the tube is completely evacuated of all air,in theory,free of friction as the masses move.

What happens to the tube, insofar as movement referenced to an outside reference is concerned?

Does it move when the masses strike the end plates,or remain stationary?

If I understand correctly, the masses are at the bottom of the U moving in opposite directions, round the corner and hit the ends at exactly the same time.

As they round the corner, force is imparted to the U through the magnetic repulsion so it moves blunt end first for a short distance. When the masses strike the end plates, the same amount of momentum in opposite direction is imparted to the U and it stops.

It's the same effect as if you and a friend were playing "catch" in the International Space Station. When you throw the ball the space station moves in the opposite direction for a short time until the ball is caught.

"When you throw the ball the space station moves in the opposite direction".

Only if you are somehow anchored to the space station. If you are free floating, what happens to the space station?

The astronauts were observed performing something that should not be possible.

They would rotate their bodies by jerking on their hammers,and slowly moving the hammer back into position,and repeating the motion to rotate further.

It takes more energy to move the hammer fast that it does to move it slowly.

You can do the same thing on a rotating bar stool. Rotate your feet in a circle in the same direction. Total change in angular momentum is zero, so the rest of your body will rotate in the opposite direction. When you stop rotating your feet, the rest of your body will stop rotating, facing in a new direction. (It may not work as well as in space, the bar stool does have friction.)

Cats land on their feet using this same principle. They rotate their tails so the rest of their body rotates in the opposite direction so that the feet are downward when they reach the ground.

http://www.richannel.org/the-physics-of-a-falling-cat

Nothing. You and the ball will hit opposite walls with offsetting force

In that case, you will recoil. Nothing happens to the space station until you hit the bulkhead behind you. When you throw the ball, nothing happens to the center of mass. When you throw the ball, something has to move in the opposite direction.

It seems to me that the forces from the turns cancel each other,and the net force would be to move the u tube towards the end plates when the masses strike the end plates.

Remember,the force is applied at the center of the bottom of the U between the 2 masses equally,and they travel the exact same distance to the end plates.

When the masses round the curved portion of the U, a force is exerted on the masses by the U (and vice versa). Momentum from the masses is transferred to the U, causing it to start moving (away from the end plates). When the masses hit the end plates (assuming they stop) the momentum is returned and the U and masses stop moving. In the end and all through the process, the center of mass does not move.

The way I am seeing it,the forces on the U are offsetting and cancelling each other as the masses turn the corner.When the masses hit the end plates,the U will start moving in the direction of the end plates.

Where is the flaw in my thinking?

Let the y axis be the axis of symmetry of the U and the x axis be perpendicular to y.

The masses start out in minus and plus x directions (symmetrical so far) and then both masses turn in the positive y direction, imparting force on the U in the negative y direction. The U moves momentarily in the minus y direction until the masses hit the end plates, whereupon it stops.

Consider this:

I am still fuzzy on this.Consider flow through an elbow;the elbow has a tendency to rotate,and there are Coriolis flow meters designed around this principle.

Two elbows in opposite directions, with equal flow and velocity,if coupled rigidly together will have no net Coriolis effect.

If you abruptly stop the flow on one of them,the whole assembly will attempt to rotate.

This is because the elbow is full of liquid,and the fluid in the bends is still in motion.

Now consider a ball traveling inside one of the pipes,(ignoring friction for now), it being set in motion by some method,and now traveling only by it's inertia.

As it turns the corner,the elbow will attempt to rotate,and when it strikes a stop plate at the end of the pipe,it's forward motion should be transferred to the plate,and the pipe should move in the same direction as the ball.

Now if we connect 2 of these elbows into the shape of a u tube,and freely suspend them,and propel two balls in opposite directions with a pulse from the center,the rotational forces should cancel,and the directional forces should combine.

So what do I have wrong in this line of thought?

Not enough sleep? Too much single malt? Too much wackybacky?

Too little physics.

The balls cannot change direction without a force, even inside an elbow.

At the 45 degree point of the elbow (for example), the balls are applying a force on the elbows, and the elbows are applying an offsetting force on the balls.

At this 45 degree point, the balls are applying a vector force directly away from each other (offsetting as you state), but they are also applying a vector force away from the capped ends of the U-pipe, causing movement in that direction.

This "away from the capped ends" force can be graphed as a half sine wave, with the force being 0 coming into the elbow, maximum at the 45 degree point, and 0 as they leave the elbows.

Does this help?

"Now I see!" said the blind carpenter,as he picked up his hammer and saw.

Thanks.

When the two masses meet in the middle of the tube, it makes my head hurt!

The gyroscope idea makes my head hurt also. Right now a rubber band connected to a paper airplane propeller axle makes my head hurt. It is Friday, I am working on beer-thirty.

How about a coil of wire around the world, held up all around the world by e.g.
hydrogen balloons supplying the earth (lings) with the generated power?

The balloons would not need to hold much weight, being counter balanced all around.
The coil(s) of wire being held equidistant from the earth all round the circumference,
or just at the poles? (ignore wind etc. due to very good designing.)

Just an idea. jt.

They said Beethoven was mad, Mozart was mad, Louis was mad... who's Louis?
(my uncle, he was mad. (J.Durant.)

At one point I did some thought experiments along this line and ran some numbers. I think it was after watching Feynman's Lectures and I was pumped about physics. I will pass on what I found, but it was a long time ago and I don't have the actual work any longer.

Actually, it is possible to extract energy in this way, it is just horribly inefficient and in the VERY long run it could be worse for the planet than many other forms of energy generation.

The Earth is storing huge amounts of energy in the form of momentum as it rotates on its axis every day. If you have a gyroscope that is spinning with its axis aligned with the rotation of the earth but allowed to rotate on an axis perpendicular with that same rotation you could extract energy from the force created as the gyroscope resists changing direction as the earth rotates under it. In fact, this is just a full gyroscopic version of Foucault's Pendulum (science experiment, not book).

None of this is magical or any form of perpetual motion. It is all basic physics that actually doesn't require much more than Newton's law's and some calculus to figure out.

The reality, on the other hand, gets pretty messy. To extract any useful level of energy from the system you would need a rather large gyroscope moving a huge amount of mass fairly quickly. This means that the force on the material of the gyroscope itself would be huge. It would probably require unobtanium level strength to just be able to hold together.

At smaller sizes you run into the scaling problem. The gains from the system would require such low friction on the bearing system as to probably be impractical, you would lose more energy from keeping the gyroscope going than you would gain from the system. NOTE - this is not extracting energy from the spin of the gyroscope as I have seen mentioned many times here, this is a pure friction effect.

The energy is actually being extracted from the stored kinetic energy of the Earth as it rotates. The rotating gyroscope is the "Lever" that allows you to do this, but the energy of the gyroscope is independent of the energy extracted. You would in fact be causing the Earth to rotate at a slightly slower rate as you used the system.

If this was a very common form of energy production over time it would actually cause days to get longer. On the back of an envelope, I calculated the effect of doing this. If I remember correctly, generating the world's power usage at roughly a 30% efficiency rate (SWAG estimate) using this method would lengthen each day by almost a second over 100 years. I could easily be a few orders of magnitude off on that but it gives you the idea.

As you try to extract energy from the system other problems would be created. The more energy that is extracted from the system will create greater precessional and nutational forces. These forces will be presented as on changing angular forces on your bearing system and can create massive stress and additional sources of energy loss.

Don't forget that you will need a mounting system that can hold everything together. To generate 1 MW of electricity you will need a mount that can withstand the equivalent kinetic force, plus all the difference caused by inefficiency.

It is a cool idea, but impractical.

How do you slow the rotation of the earth without violating conservation of angular momentum?

Firstly, one would have to have a way to couple the earth to another (large) mechanical object to spin up. So far, all we have is the earth, this huge freaking gyroscope (hanging on a sky hook???), and space. Where is the support rig? Where is the interference coupling?

Oh, BTW, we also have a head ache.

That other large mechanical object is the moon. The moon has angular momentum due to its orbit around the earth. The earth's spinning slows, losing angular momentum and the moon's orbit gets higher, gaining angular momentum.

So much for floating energy barges...

There is an electrical potential between the moon and the Earth.

If we could find a way to convert,perhaps via microwaves, and transfer that energy...

Also the ionosphere is highly charged,referenced to ground.

How could we use that?

It's with the same parallels with this free energy birdie I found in youtube