Lowemack

Do you agree with the first paragraph in this post. If the whole roundabout was on a scale, would the reading decrease as the weights were going up and decrease when they are going down?

All the wheels are rotating and also rotating around the roundabout. They will all, constantly wobble upwards, because it is always the outside edge of each wheel that is heavier, because it has some extra relativistic mass than the inside, downward moving part.

Would a rotating unbalanced wheel not wobble? I had to modify it slightly as I got the direction of thrust wrong, it would be tangential not centrifugal. Try this similar thought experiment. I am in a space ship and I throw a cannon ball to the rear. I generate thrust until the canon ball hits the back of the space ship, then we will stop. Then if I walk to the cannon ball and bring it back, the ship will be back at it's start position. What if before I throw the cannon ball I spin it really fast so it gains relativistic mass, then I throw it and before it hits the back of the space ship i can stop it spinning so it will have less mass, we must then generate overall thrust. Rotating balls or stopping them spinning will not alter the spaceships linear momentum.

Imagine a children's roundabout, with vertical wheels around the circumference, pointing towards the centre. Each wheel has a weight on it's outside edge making each wheel unbalanced. If we spin all these wheels together in synchronisation, and the weights go up on the outside and the down nearer the centre, would there be a slight upward lift when the weights are moving up on the outside, and a slight downward pressure when they are going down towards the centre. If the answer is yes, then my thought is that if we could keep the unbalanced weight on the outside, always going up then we would have a slight lift. So, if remove the weights so the wheels are balanced, spin the wheels, then we spin the roundabout really fast, the outside edge of all the wheels would be heavier than than the inside edge of the wheels due to the fact that the linear velocity on the outside is greater than towards the centre and this would cause it to be heavier because relativity says faster things get heavier. This would give a constant lift. The lift would only be small, but any non propellant thrust in space is really useful. Also, apart from overcoming friction, it does not need any energy, once it is up to speed.

Conservation if momentum is very fundamental, but not usually associated with Relativistic masses. Can you pinpoint where my idea breaks down? Would an unbalanced disc cause linear thrust. Would rotating wheels be heavier than non-rotating ones?

Centrifugal Offset Relativistic Engine or CORE Drive. Imagine a children’s roundabout with a flat smooth base on some ice. Spin the roundabout and if it is balanced, even with no friction with the ice, it will stay in the same location. If it is not balanced, say, we put one child on it, then when we spin it, the rotational axis will describe a circle in the ice. The imbalance in weight in the system causes the whole roundabout to move along the line of the net centrifugal force. If we could keep the imbalance of weight in the same place then we could generate linear thrust. So now imagine the roundabout with a number of vertical wheels around the circumference, with the direction of rotation towards the centre. If we spin all these wheels then spin the roundabout, it should still remain stationary on the ice. But what if we arranged to adjust the speed of the wheel rotation as they revolve around the roundabout. So, looking from above, at East we start accelerating the wheel*, until at West it is at it’s maximum speed, then we start decelerating until back at East it is stationary. We do this for all wheels at the same position, so as the roundabout is revolving, wheels at West are maximum speed and wheels at East are Zero speed. We should now have a slight imbalance of mass now as the wheels that are rotating will have slightly more mass than the non rotating ones due to the increase in relativistic mass. This imbalance will give a thrust in the West direction. This is a non-propellant thrust ideal for interstellar travel. This is my gift to the world, just a Knighthood and a Nobel prize please. You are welcome. *The rotation forces could be generated by electrical induction forces like an electrical motor, and the wheels would be like the rotor of the motor PS This post was just deleted from Phisicsforum. Please inform me why if it is to be deleted.

I think my point is that the local observer sees the lamps flash in sync, because the light beams hit the mirrors at the same time. A moving observer would 'see' the light hit the mirrors along the axis of travel, at different times. Yet, as you just stated he would see the lamps flash together..... so for him does the light actually hit the mirrors at different times, or just 'look' that way because of how we see or measure things using light?

If the lamps were wired to the mirrors with the same length of cable, then there would be a delay after the photon strikes the mirror before the lamp flashes (same delay for each mirror). The lamp would then flash at regular intervals (albeit delayed after the event) for a local observer. Would then an observer with relative motion see the flashes with 2 different flash periods? I know i'm not explaining this very well, but this experiment could be set up so that we have 2 of these clocks at 90deg, with sensors at each end wired back to lamps at the center with cable of the same length. Then for an observer in the same reference frame as the clocks he would see both lamps flashing in sync and with regular periods. I cannot understand how an observer moving close to C along the axis of one of the clocks could see one of these lamps flash differently, because he should be seeing the same 'light cones' of the lamps that the local observer saw?

Great graphics. In your system, if there was a lamp on each clock, located at the intersection, that was wired to flash when the photons hit either mirror, then if an observer local to the clocks sees both lamps flashing together, how can those light beams from the lamp, travel to a moving observer and make him see them flashing out of sync?

If the 2 clocks were fixed in a cross with flashing lamps at the centre, wired to the sensors on the mirrors, the observer with the clocks would see both lamps flash in sync. I can't then see how a stationary obeserver would see them flash out of sync and with one lamp having asymmetrical pulses.

I've just watched a SR video on youtube It is a typical one showing a clock being 2 mirrors in a vertical tube of length C. The clock ticks when light bounces of each mirror, i.e every second. It goes on to explain that when the clock is moving horizontally, a stationary observer would see the light travel further, ie indicating time dilation for an observer moving with the clock. What seems wrong with that explanation is that if you had 2 identical clocks at right angles to each other, then would the stationary observer see the clock parallel to the motion have a longer period for when the light was travelling in the same direction, and shorter when at 180 deg. It seems obvious that an observer with the clock would see both clocks tick in sync, but according to SR would a stationary observer really see both clock ticking at different times and the horizontal clock having asymmetrical pulses?

So if on my lab, on my space ship, I have a closed long tube with a photo sensor at both ends, connected to an accurate clock. If I travel towards the sun @0.5C, open one end of the tube, the clock starts when the light from the sun hits the first sensor and stops on the second sensor, then I get a measurement of time. If I repeat the experiment moving away from the sun, will I read the same time on my clock. If yes, will the distance between the sensors, as measured on the ship divided by the time on the clock = C. Obviously time dialation/ length contraction can't explain why both experiments give the answer C, I think the answer must be "C is invariant" because it is(as stated above), not because time slows down, or length contracts. But if that is the case, does time really slow down for moving objects and do lengths contract, because surely they would have opposite effects for both experiments, yet the answer is C in both cases. If the photo sensors had lights on them that lit when they were activated, would a stationary observer (relative to the sun) measure the period between pulses as the same for both experiments? His measurement for distance that light travelled, would be different. So how can this be reconciled?

I think I get it:- Maxwell calculated that the speed of light is invariant. Michleson Morley proved it. This meant that if nothing can travel faster than light then we need to use Lorenze transformation formulae for relativistic speed additions. C is constant because of how we add up relative speeds.

But all this is happening on my rocketship (not distant), in one frame, travelling to the sun at some relativistic speed and measuring the speed of light from the sun and from the earth (in a lab on my rocketship). I can understand that different reference frames can have different clocks and different measuring rods, but I can't see how either or both of those effects can explain how both measurements are the same.

But would that cause opposite effects to the speed measurements we made to the light we are travelling towards (sun), and the light we are moving away from (earth)? If we are moving towards the sun and away from the earth how can "length contraction" be the reason both sources of light measure the same speed?

Arithmetic -- exponents, square roots, logarithms etc = Comfortable Simple algebra -- ie. [math] 2=\frac{1}{\sqrt{1 - x^2}}[/math] = Comfortable Vectors = Comfortable ish Basic Derivatives = Comfortable ish Chain rule/product rule = familiar but too long ago to remember Linear algebra -- transformations using a matrix = not really Thanks in advance.

Surely both won't be the same because length contracts and time dilates, because without relativistic effects, light from the sun should be faster and light from the earth slower. How can both measure the same due to the same reason. So basically the speed of light is a constant, and has nothing to do with our time or distant measurements changing with velocity. My problem is that if you ask "why does someone in a rocketship travelling to the sun measure the same for c as someone on earth" then the answer is usually "because moving clocks run slow". But I cannot get my head around the fact that a clock running slow cannot explain my first question. A slow running clock cannot make light seem to measure faster AND slower than it would without relativistic effects.

If we are in a rocket flying to the sun at 0.75C, why would we measure light from the sun AND light from earth to be C. It can't be because "moving clocks tick slower" for both cases, can it?

Not quite, his birthday is 31st December. On Jan 1st he is 19 and this year he'll be 20, next year 21, 2 days ago he was 18.

Thanks a lot, that works perfect.

(sorry posted this first in Quantum mechanics by mistake:confused: ) Does anybody know what the formula is for the graph you see in text books, of speed against time for a constant force applied to an object. The one where speed increases with time, and then levels of as it approaches C. For non reletavistic speeds I think the formula is f=ma, which when re-arranged would give t=mv/f. and for a force of 1N applied to a mass of 1kg t=v. So after 10 seconds the mass would be doing 10m/s,after 20s 20m/s. But at speeds close to C we know that this is not the case, so does anybody know the formula that matches the graph I mentioned?

sorry, I meant to post this in 'Relativity'. Can anyone move it please?

For non reletavistic speeds I think the formula is f=ma, which when re-arranged would give t=mv/f. and for a force of 1N applied to a mass of 1kg t=v. So after 10 seconds the mass would be doing 10m/s,after 20s 20m/s. But at speeds close to see we know that this is not the case, so does anybody know the formula that matches the graph I mentioned?

Does anybody know what the formula is for the graph you see in text books, of speed against time for a constant force applied to an object. The one where speed increases with time, and then levels of as it approaches C.

If temperature is - "The measure of the average kinetic energy of the particles in a substance", then how does an atom "absorb" infra red radiation and thus increase its speed. And more to the point, how, when radiating(cooling down), does an atom know which way to emit the radiation to slow it down? If the temperature of an atom is a meassure of its speed then is temerature relative? Please help!!