Toffo

Senior Members

62

1

1. Thermoelectric effects in metals

When two blocks of platinum are brought together electrons do not tend to move from block to another block, because the blocks are identical. Zero motion means zero Seebeck effect. When a block of platinum and a block of iron are brought together electrons do tend to move from one block to another block. Then some works must be done to separate the blocks. The blocks form a charged capacitor. If there was a way to connect wires to that capacitor so that there is no Seebeck effect between the blocks and the wires, then we would have a perpetual motion machine. Actually there is a way to adjust the contact voltage between the wires and the blocks: Temperature. Heat in the contact decreases the contact voltage, I guess. The effect is called contact voltage if I remember correctly. I mean the effect of contact becoming a charged capacitor. What happens when a cool platinum block and a hot platinum block are brought together? Interesting question there ... some electrons move from the hot block to the cool block. Electrons have less potential energy in the cool block, so electrons tend to fall from hot block to the cool block. This effect is probably same in all metals, so this effect's effect on the Seebeck effect is zero, probably.
2. gravity and kinetic energy

There are many kinds of mediums. Below there is a road and three cars that are driving to the right, always at constant speed, we are looking from above. The road is the medium to the cars. When the cars enter the curvy part, they lose some rightwards pointing velocity and momentum. The road absorbs the momentum. When the cars leave the curvy part, the rightwards pointing momentum goes back from he road to the cars. -----ooo--------------◠◡◠◡◠◡◠◡◠◡◠◡------------------- Now let's say the ''road' is an optical fibre, and the 'cars' are photons. The story is the same as above. That was trivial. But what if the picture is a road profile where the bumps are hills?
3. gravity and kinetic energy

If you were to jump off a very high cliff your momentum would be increasing steadily, and your velocity would be increasing steadily. Your kinetic energy would be those two things multiplied. Now let's try to replace 'you' with 'photon' in that sentence above: If a photon were to jump off a very high cliff its momentum would be increasing steadily, and its coordinate velocity would be decreasing. Its kinetic energy would be those two things multiplied. The above sentence may be incorrect, as the kinetic energy would be decreasing, which does not sound quite right. Let me try again: The momentum of the downwards falling photon is increasing at the same rate as its potential energy is decreasing, and the coordinate velocity of the photon is decreasing at the same rate as its potential energy is decreasing. The product of the momentum and the coordinate velocity is unchanging. That's much better.
4. proper acceleration

What is this proper velocity thing? If a driver measures his speed relative to road to be 0.5 c, then a cop standing on the road agrees that the car moves at speed 0.5 relative to the road.
5. proper acceleration

Let's consider forces affecting an object swung around using a rope. If the Newtonian centripetal force measured on the rope is F, then the relativistic centripetal force is gamma * F, because the transverse mass of the object is gamma*rest mass. This is the force at the other end of the rope. I mean at the end that is not moving relativistically. At the end that is moving relativistically forces are measured to be gamma times bigger. I like to think that's because of time dilation. The proper acceleration is measured by an accelerometer, which is a force meter. So a force meter attached to the object measures this force: Newtonian centripetal force times gamma squared. So when used as an accelerometer the force meter measures this acceleration: Newtonian centripetal acceleration times gamma squared. Longitudinal acceleration and transverse acceleration are quite different: Longitudinal acceleration changes the longitudinal mass and the transverse mass. While transverse acceleration does not change the longitudinal mass or the transverse mass. So it makes sense that longitudinal mass and transverse mass are quite different.
6. Supernovae & Gravity Waves

Let us consider million rocks arranged in a sphere formation. Every rock is simultaneuosly and abruptly pulled outwards by some force. We know that extra energy is used in this pulling procees, because a rock thinks the distance to the other rocks is shorter than the real distance. But we also know that no gravity waves are generated in this kind of situation, because experts have said so. So we conclude that the extra energy will absorbed by the rocks at some later time. Now let us remove one rock from the formation. Quite obviously the hole will emit some gravity waves, spherical gravity waves. If we remove more rocks every hole will be a source of spherical gravity waves. If we remove all rocks except two at opposite sides of the sphere, there will be 999998 holes that emit spherical gravity waves that interfere with each other. Distant gravity wave detectors will detect a maximum of gravity waves at some place and minimum of gavity waves at some other place.
7. Angular velocity & impossible situation of relativity

Interesting problem here. Let's see ... Bob revolves around Alice observing Alice. When Bob observes Alice, there is a constant Dobbler blue shift, but despite of that all the frequencies Bob sees are the real unchanged frequencies. They must be the real ones, otherwise there is a problem, as has been pointed out by the OP. Let's consider some optical fibres on a spinning carousell, fibres are installed radially. At the middle of the carousell there is some photon gas in some container, that gas is steered into the fibres. At the other end of the fibres there are containers into which the photon gas goes. We are interested about the energy of photon gas in a container in the container frame. The gas was given kinetic energy by the carousell, but in the container frame that energy does not exist. So we conclude that no increase of energy caused by the rotation of the carousell will be observed inside a container. Right?
8. Does a spinning disk gain relativistic mass

AC current, well there are some propagating electromagnetic fields carrying energy and momentum, not really different from a laser. DC current? Now we have some kind of ion thruster. Well how about a drive shaft then? Probably when you press a brake pad on a spinning drive shaft, the shaft will try to move to some direction, the direction opposite to the energy flow.
9. Does a spinning disk gain relativistic mass

No. I guess. As Strange said, amusing energy juggling gadgets are almost like ordinary matter bouncing apparatuses. Yes. Very very very likely the center of mass would stay at rest.
10. Does a spinning disk gain relativistic mass

Does previous post sound a little bit like a joke? Here's yet another way to transfer energy from a moving battery: Laser device attachet to the battery. With this energy transfer method it's clear that there exist a thrust effect and redshifft effect.
11. Does a spinning disk gain relativistic mass

Two spiral cords are connected to the terminals ot the moving battery. Now the moving battery can be easily drained to a static battery. So what will happen: When the batteries move away from each other: We try to remove energy from the battery but what happens is that some electro-chemical energy turns into kinetic energy. A reduced amount of energy arrives to the static battery. When the batteries move towards each other: We want to remove the electro-hemical energy from the battery but some kinetic energy turns into electro-chemical energy. an increased amount of energy arrives to the static battery. In both cases the cord tries to move away from the moving battery ... like a toy that consists of a whistle and a rolled paper tube ... what is that called? (You see, the battery is blowing energy into a curly hose, and the energy is redshifted or blueshifted)
12. Does a spinning disk gain relativistic mass

A battery is loaded -> it becomes more massive. Then battery is pushed so that it slides along a surface. On the surface there are metal strips that short circuit the battery. Then the drained battery, which is less massive than the battery that was pushed, is stopped.
13. Does a spinning disk gain relativistic mass

Here's an alternative version: A battery is loaded, then the loaded battery is thrown, then the flying battery is drained, then the empty battery is stopped.
14. Maintaining the appearance of fixed distance in spite of length contraction?

Let's do some math. First an accelerating rocket at non-relativistic velocity. We are interested about the shrinking velocity of the rocket according to an outside observer. At non-relativistic velocities: coordinate acceleration = proper acceleration. Let's say the acceleration is constant. shrinking velocity at some time from the beginning of the acceleration = time * (rear's proper acceleration - front's proper acceleration) The term (rear's proper acceleration - front's proper acceleration) can be written as: length*acceleration*some constant. "Some constant" might be the gravitational constant, definitely the gravitational constant must be there. Hey I think I can do the relativistic case too: shrinking velocity at time t from the beginning of the acceleration = integral from 0 to t ( (rear's proper acceleration - front's proper acceleration) / gamma^2) (gamma squared because the acceleration drops as gamma^2, a velocity change is smaller AND it takes a longer time in the outside observers frame) ADDITION: Gravitational time dilation can be thought as causing the differences between front and rear, and I think there's should be some very simple equation regarding that.
15. Maintaining the appearance of fixed distance in spite of length contraction?

Yeah. For example: Constant proper acceleration for a leading space ship, a little bit larger constant proper acceleration for the space ship following the first one. Actually there's no room for any unlesses here. Same frame = no relative motion = rigidity
×
×
• Create New...