Quote: Original post by owl

Quote: Original post by mikeman
Something I can't quite get my head around is this: A spaceship does not accelerate due to an external force, but by a thrust provided from the engine, which of course moves along with the ship. So, if hypothetically the ship accelerates to relativistic speeds, does that mean that the engine, also moving at that speed, will work slower(in reference to Earth), burning less fuel per second, thus providing smaller thrust? Is this real? Or the mass of the fuel will increase the same as time dilates, so even if the engine works 'slower', it burns as much fuel as before? What's happening in reality?

It'd seem to work slower from Earth's point of view (if somehow someone on Earth could observe things inside the spaceship). In relation to the spaceship, everything is perfectly normal. Space and time works exactly as if the ship was at rest.

Yeah, I'm aware of that. What I'm asking is what would the predictions of an Earth observer be as about the behaviour of the engine. I'm pretty sure he would predict that the engine would in fact work 'slower', so there's something that would need to compensate in order for the thrust to remain the same. Is it the mass of the fuel, which increases as speed increases, or something else?

Quote: Original post by mikeman

Quote: Original post by owl

Quote: Original post by mikeman
Something I can't quite get my head around is this: A spaceship does not accelerate due to an external force, but by a thrust provided from the engine, which of course moves along with the ship. So, if hypothetically the ship accelerates to relativistic speeds, does that mean that the engine, also moving at that speed, will work slower(in reference to Earth), burning less fuel per second, thus providing smaller thrust? Is this real? Or the mass of the fuel will increase the same as time dilates, so even if the engine works 'slower', it burns as much fuel as before? What's happening in reality?

It'd seem to work slower from Earth's point of view (if somehow someone on Earth could observe things inside the spaceship). In relation to the spaceship, everything is perfectly normal. Space and time works exactly as if the ship was at rest.

Yeah, I'm aware of that. What I'm asking is what would the predictions of an Earth observer be as about the behaviour of the engine. I'm pretty sure he would predict that the engine would in fact work 'slower', so there's something that would need to compensate in order for the thrust to remain the same. Is it the mass of the fuel, which increases as speed increases, or something else?

It actually doesn't work slower. Time appears to transcur at a lower pace from Earth's point if view. From Earth's point of view the space-shipp would apear to get away at a certain speed. From space-ship point of view, Earth would appear to get away at the same speed. The measures on the speed from both points of view should match.

This means that there is nothing to compensate for. The engine, in it's point of reference is performing the right work in the right time to thrust the space-ship to the speeds an observer from earth will measure the space-ship be going.

I've never understood why quantum entanglement could not be used, from what I understand since you can't copy the quantum state to read from a particle you would also change it's state.

So why not just read the particle then set the particle back to it's original state?

I probably just completely don't understand the concept though...

Quote: Original post by owl

Quote: Original post by mikeman

Quote: Original post by owl

Quote: Original post by mikeman
Something I can't quite get my head around is this: A spaceship does not accelerate due to an external force, but by a thrust provided from the engine, which of course moves along with the ship. So, if hypothetically the ship accelerates to relativistic speeds, does that mean that the engine, also moving at that speed, will work slower(in reference to Earth), burning less fuel per second, thus providing smaller thrust? Is this real? Or the mass of the fuel will increase the same as time dilates, so even if the engine works 'slower', it burns as much fuel as before? What's happening in reality?

It'd seem to work slower from Earth's point of view (if somehow someone on Earth could observe things inside the spaceship). In relation to the spaceship, everything is perfectly normal. Space and time works exactly as if the ship was at rest.

Yeah, I'm aware of that. What I'm asking is what would the predictions of an Earth observer be as about the behaviour of the engine. I'm pretty sure he would predict that the engine would in fact work 'slower', so there's something that would need to compensate in order for the thrust to remain the same. Is it the mass of the fuel, which increases as speed increases, or something else?

It actually doesn't work slower. Time appears to transcur at a lower pace from Earth's point if view. From Earth's point of view the space-shipp would apear to get away at a certain speed. From space-ship point of view, Earth would appear to get away at the same speed. The measures on the speed from both points of view should match.

This means that there is nothing to compensate for. The engine, in it's point of reference is performing the right work in the right time to thrust the space-ship to the speeds an observer from earth will measure the space-ship be going.

Okay, to avoid confusion, I'm talking strictly about the Earth's reference frame. To an Earth observer, the spaceship is going at a relativistic speed, so he predicts time dilates inside the ship. Following that, he predicts that the engine works in slower rate compared to the rate it would work in Earth, exactly like the clocks in the spaceship tick slower than the clocks in Earth. Is this right?

Quote: Original post by mikeman

Quote: Original post by owl

Quote: Original post by mikeman

Quote: Original post by owl

Quote: Original post by mikeman
Something I can't quite get my head around is this: A spaceship does not accelerate due to an external force, but by a thrust provided from the engine, which of course moves along with the ship. So, if hypothetically the ship accelerates to relativistic speeds, does that mean that the engine, also moving at that speed, will work slower(in reference to Earth), burning less fuel per second, thus providing smaller thrust? Is this real? Or the mass of the fuel will increase the same as time dilates, so even if the engine works 'slower', it burns as much fuel as before? What's happening in reality?

It'd seem to work slower from Earth's point of view (if somehow someone on Earth could observe things inside the spaceship). In relation to the spaceship, everything is perfectly normal. Space and time works exactly as if the ship was at rest.

Yeah, I'm aware of that. What I'm asking is what would the predictions of an Earth observer be as about the behaviour of the engine. I'm pretty sure he would predict that the engine would in fact work 'slower', so there's something that would need to compensate in order for the thrust to remain the same. Is it the mass of the fuel, which increases as speed increases, or something else?

It actually doesn't work slower. Time appears to transcur at a lower pace from Earth's point if view. From Earth's point of view the space-shipp would apear to get away at a certain speed. From space-ship point of view, Earth would appear to get away at the same speed. The measures on the speed from both points of view should match.

This means that there is nothing to compensate for. The engine, in it's point of reference is performing the right work in the right time to thrust the space-ship to the speeds an observer from earth will measure the space-ship be going.

Okay, to avoid confusion, I'm talking strictly about the Earth's reference frame. To an Earth observer, the spaceship is going at a relativistic speed, so he predicts time dilates inside the ship. Following that, he predicts that the engine works in slower rate compared to the rate it would work in Earth, exactly like the clocks in the spaceship tick slower than the clocks in Earth. Is this right?

I believe it is. Taking the engine out of it's space-time frame to make calculations on how it works makes no sense at all :)

If I was a betting man, I would guess that in a 1000 years our present understanding of the the way the universe works will seem archiac and shallow at best; if not completely ignorant. Just because we don't see how it's possible now, doesn't mean it won't be.

Quote: Original post by owl
I believe it is. Taking the engine out of it's space-time frame to make calculations on how it works makes no sense at all :)

Ehm...but this is exactly what special relativity is, transformations of measurements between (inertial)reference frames that move relative to each other.

http://en.wikibooks.org/wiki/Special_Relativity/Mathematical_transformations

Quote: Original post by mikeman

Quote: Original post by owl

Quote: Original post by mikeman

Quote: Original post by owl

Quote: Original post by mikeman

Quote: Original post by owl

Quote: Original post by mikeman
Something I can't quite get my head around is this: A spaceship does not accelerate due to an external force, but by a thrust provided from the engine, which of course moves along with the ship. So, if hypothetically the ship accelerates to relativistic speeds, does that mean that the engine, also moving at that speed, will work slower(in reference to Earth), burning less fuel per second, thus providing smaller thrust? Is this real? Or the mass of the fuel will increase the same as time dilates, so even if the engine works 'slower', it burns as much fuel as before? What's happening in reality?

It'd seem to work slower from Earth's point of view (if somehow someone on Earth could observe things inside the spaceship). In relation to the spaceship, everything is perfectly normal. Space and time works exactly as if the ship was at rest.

Yeah, I'm aware of that. What I'm asking is what would the predictions of an Earth observer be as about the behaviour of the engine. I'm pretty sure he would predict that the engine would in fact work 'slower', so there's something that would need to compensate in order for the thrust to remain the same. Is it the mass of the fuel, which increases as speed increases, or something else?

It actually doesn't work slower. Time appears to transcur at a lower pace from Earth's point if view. From Earth's point of view the space-shipp would apear to get away at a certain speed. From space-ship point of view, Earth would appear to get away at the same speed. The measures on the speed from both points of view should match.

This means that there is nothing to compensate for. The engine, in it's point of reference is performing the right work in the right time to thrust the space-ship to the speeds an observer from earth will measure the space-ship be going.

Okay, to avoid confusion, I'm talking strictly about the Earth's reference frame. To an Earth observer, the spaceship is going at a relativistic speed, so he predicts time dilates inside the ship. Following that, he predicts that the engine works in slower rate compared to the rate it would work in Earth, exactly like the clocks in the spaceship tick slower than the clocks in Earth. Is this right?

I believe it is. Taking the engine out of it's space-time frame to make calculations on how it works makes no sense at all :)

Ehm...but this is exactly what special relativity is, transformations between (inertial)reference frames that move relative to each other.

The ilussion that the engine works at a slower rate, is just that, an ilussion. It is working exactly as if it was on earth. The guy analysing how the engine works should use the space-time frame the engine is working into, not his own.

Quote: Original post by owl
The ilussion that the engine works at a slower rate, is just that, an ilussion. It is working exactly as if it was on earth. The guy analysing how the engine works should use the space-time frame the engine is working into, not his own.

It's not an 'illusion'. It's very very real. For example, it has been observed that the half-life of a fast moving particle is increased for static observer. That's because time moves slower for the particle, so it decays slower. Look here under 'Time Dilation For Particles'. That's how muons reach the surface of the earth before decaying. It's a real phenomenon alright.

http://www2.slac.stanford.edu/vvc/theory/relativity.html

Quote: Original post by mikeman

Quote: Original post by owl
The ilussion that the engine works at a slower rate, is just that, an ilussion. It is working exactly as if it was on earth. The guy analysing how the engine works should use the space-time frame the engine is working into, not his own.

It's not an 'illusion'. It's very very real. For example, it has been observed that the half-life of a fast moving particle is increased for static observer. That's because time moves slower for the particle, so it decays slower. Look here under 'Time Dilation For Particles'. That's how muons reach the surface of the earth before decaying. It's a real phenomenon alright.

http://www2.slac.stanford.edu/vvc/theory/relativity.html

I believe you should re-read all that quite a few more times. You're very confused. Lets not forget your original question

Quote: Is this real? Or the mass of the fuel will increase the same as time dilates, so even if the engine works 'slower', it burns as much fuel as before?

Quote: The concept of "relativistic mass" is subject to misunderstanding. That's why we don't use it. First, it applies the name mass - belonging to the magnitude of a 4-vector - to a very different concept, the time component of a 4-vector. Second, it makes increase of energy of an object with velocity or momentum appear to be connected with some change in internal structure of the object. In reality, the increase of energy with velocity originates not in the object but in the geometric properties of spacetime itself.

Taylor and Wheeler

In short: No. Invariant mass doesn't increase.