The Rocket Ship

[Pantaz]

Nor along the lines of this either.

 

He already started another thread with that one...

http://www.scienceforums.net/forum/showthread.php?t=33633

[nstansbury]

Ok here's the maths:

 

But if the shaft changes rotational velocity it is no longer 300 revolutions per second. In other words, the shaft may only rotate 299 revolutions per second if it changes rotational velocity. That means the shaft is no longer accurate.

 

Lets take 3 of your rotating shafts (S), with radius of 1, 3, and 5 cm respectively

 

All of them rotate at exactly 1 RPM - 1 full revolution per minute.

 

The distance a shaft must rotate in order to complete "1 rotation" is its' circumference, therefore:

 

[math]d=c=2\pi r[/math]

 

Agreed?

 

so:

[math]S1=2\pi 1\approx 6cm[/math]

 

[math]S2=2\pi 3\approx 18cm[/math]

 

[math]S3=2\pi 5\approx 30cm[/math]

 

 

Remember all of them rotate at 1 RPM, irrespective of their size

 

 

So, velocity is distance x time: [math]v=dt[/math]

A point on S1 moves back to the start in 6 x 1 seconds

A point on S2 moves back to the start in 18 x 1 seconds

A point on S3 moves back to the start in 30 x 1 seconds

 

So S3 must have a velocity 5x faster than S1 because it has 5x further to go, so even though they both travel at 1 RPM - they both move at different velocities.

 

But how can they? 1 RPM is 1 RPM right?

 

S1, S2 & S3 all move at 1 RPM yet all 3 think that means they need to travel at a different velocity.

 

So you can see that 1 RPM is a function of the shafts radius? Agreed?

 

Well, this is what happens to the shafts radius as you approach the speed of light, an effect called the Lorenz transformation causes the distance to reduce - above show what happens when the distance of your shaft changes.

 

 

The color blue, like the color of the forum's symbol. Like the color of the sky, only a bit darker. Visibly blue and ONLY blue, hence not just 'containing' blue, just blue. I claim that when you look at the sun you see it blue. when you take a picture of the sun through a satellite in High Definition, it is blue, only blue, and nothing but blue. No other color in it.

 

Prove me wrong.

 

Unless the light is moving away from you in which case "Blue" is "Red"

[Motor Daddy]

I can see this is turning into a rules thing. I'm done.

[Phi for All]

I can see this is turning into a rules thing. I'm done.

Classic. I mean a completely priceless classic.

[mooeypoo]

Quite fitting for the quotes thread, I'd say.

[swansont]

Yeah, being asked to back up a claim with evidence. How fracking unreasonable can you get?

[mooeypoo]

Unless the light is moving away from you in which case "Blue" is "Red"

 

 

Smartass.

 

The sun doesn't move away from us enough to cause its visible light to change much for our naked eye to notice (actually, the sun doesn't move, we do, but you get my point).

 

And my point was to show that if someone insists on claiming an absurdly unrealistic claim as reality, there is no point in even getting into math. The sun is not blue, it's orangish-yellow. It's not square, it's spherical. Anyone claiming that an observed, proven fact is not a fact is missing something in terms of perception of reality, even before missing something in terms of scientific endeavoring.

 

[Motor Daddy]

Yeah, being asked to back up a claim with evidence. How fracking unreasonable can you get?

 

The evidence is in the first post of this thread. The data acquisition systems don't lie.

 

It seems a foot is no longer a foot, and a mile is no longer a mile. Whoops, there goes the speed of light.

[Phi for All]

Yeah, being asked to back up a claim with evidence. How fracking unreasonable can you get?

You physicists! It's like you've got a "rule" for everything! When are you going to get over yourself?

 

Wait, would angular momentum be conserved if you tried to get over yourself?

[Motor Daddy]

Smartass.

 

(actually, the sun doesn't move, we do, but you get my point).

 

 

The Sun doesn't move?

 

Light travels at 186,000 miles per second. Whoops, I can't say that, because there is no "second," and there is no "mile."

 

BTW, This is a family oriented site, could you please clean up the language? Isn't there some kind of "rule" for that?

Edited June 19, 2008 by Motor Daddy
multiple post merged

[Sayonara]

Motor Daddy:

 

Your maths is "wrong" only where you are trying to use it to describe a scenario in which you are disregarding the known physical effects of relativity.

 

IOW, your maths may well describe the part of the scenario you are paying attention to, but because of this gap where the disregarded physics should be, it falls short of describing the actual events which take place in the example.

 

People on here have repeatedly attempted to explain to you why these physical effects cannot be disregarded, and how they apply to the example you provide. You have consistently ignored those members and ploughed onwards with fallacious and repetitive soap-boxing about the particular figures you happen to have chosen.

 

This kind of behaviour is considered trolling by our staff, and it is only their opinion of what constitutes trolling which determines their reactions to it, and whether the admins will support or overrule them.

 

By all means continue with this discussion, but have the common decency to actually listen to the people who are trying to help you, instead of playing the same broken record over and over like an obstinate child.

 

 

The bottom line is that your measurement of the duration of a second in your frame of reference is not necessarily the same as it is from the perspective of a different frame of reference. If you can get your head around this somewhat counter-intuitive relativistic effect, the thread will make much more sense to you.

[Motor Daddy]

Motor Daddy:

 

Your maths is "wrong" only where you are trying to use it to describe a scenario in which you are disregarding the known physical effects of relativity.

 

IOW, your maths may well describe the part of the scenario you are paying attention to, but because of this gap where the disregarded physics should be, it falls short of describing the actual events which take place in the example.

 

People on here have repeatedly attempted to explain to you why these physical effects cannot be disregarded, and how they apply to the example you provide. You have consistently ignored those members and ploughed onwards with fallacious and repetitive soap-boxing about the particular figures you happen to have chosen.

 

This kind of behaviour is considered trolling by our staff, and it is only their opinion of what constitutes trolling which determines their reactions to it, and whether the admins will support or overrule them.

 

By all means continue with this discussion, but have the common decency to actually listen to the people who are trying to help you, instead of playing the same broken record over and over like an obstinate child.

 

 

The bottom line is that your measurement of the duration of a second in your frame of reference is not necessarily the same as it is from the perspective of a different frame of reference. If you can get your head around this somewhat counter-intuitive relativistic effect, the thread will make much more sense to you.

 

The ONLY reason why I repeatedly say the same things is because they repeatedly keep bringing up the same point(s). Am I supposed to have a different answer each time they ask the same question, or talk about the same point, in order to not repeat myself?

 

The math describes the travel, not the perception of travel from different observers. I am talking about the ACTUAL numbers, not the perception of every other point in the universe of that motion.

 

The bottom line is that your measurement of the duration of a second in your frame of reference is not necessarily the same as it is from the perspective of a different frame of reference. If you can get your head around this somewhat counter-intuitive relativistic effect, the thread will make much more sense to you.

 

So how much different is a second from my frame of reference to a different frame of reference?

[swansont]

You physicists! It's like you've got a "rule" for everything! When are you going to get over yourself?

 

Wait, would angular momentum be conserved if you tried to get over yourself?

 

It's more of a Newton's third law thing.

[Sayonara]

The ONLY reason why I repeatedly say the same things is because they repeatedly keep bringing up the same point(s). Am I supposed to have a different answer each time they ask the same question, or talk about the same point, in order to not repeat myself?

No. You are supposed to take on board what they say and adapt your thinking accordingly.

 

The math describes the travel, not the perception of travel from different observers. I am talking about the ACTUAL numbers, not the perception of every other point in the universe of that motion.

The problem you are having is that your scenario in post 1 inherently involves different reference frames, and not one universal frame.

 

So how much different is a second from my frame of reference to a different frame of reference?

Depends on the frames that are involved. You have to utilise relativistic methods to work out the differences.

[Cap'n Refsmmat]

So how much different is a second from my frame of reference to a different frame of reference?

 

That's dependent on the relative velocities of the two frames of reference. You can get the answer with the equations of special relativity.

[swansont]

The math describes the travel, not the perception of travel from different observers. I am talking about the ACTUAL numbers, not the perception of every other point in the universe of that motion.

 

No such thing as ACTUAL numbers, only the numbers as measured from a particular frame of reference. This is a consequence of c being constant in inertial frames. It has some weird ramifications, such as simultaneity, distance and time not being absolutes. IOW, there is no absolute reference frame.

[Motor Daddy]

No. You are supposed to take on board what they say and adapt your thinking accordingly.

 

So they can ask the same question repeatedly of me, and expect a different answer each time they ask? Is that what you are saying?

 

 

The problem you are having is that your scenario in post 1 inherently involves different reference frames, and not one universal frame.

 

And again, I'm talking about the actual distance traveled, and the actual time it took to travel. There is no different reference frame after the time has elapsed, and you can't measure the distance and time until AFTER the time has elapsed.

 

 

Depends on the frames that are involved. You have to utilise relativistic methods to work out the differences.

 

There is one definition of a second, not two. Since I am a distance away from you right now, do you measure a second differently that I do?

 

No such thing as ACTUAL numbers, only the numbers as measured from a particular frame of reference. This is a consequence of c being constant in inertial frames. It has some weird ramifications, such as simultaneity, distance and time not being absolutes. IOW, there is no absolute reference frame.

 

So c is a constant velocity of 186,000 miles per second, but a second can not be a constant?

[Sisyphus]

Motor Daddy:

 

Your frustration is understandable, since relativity is quite counterintuitive, and the people you're arguing with, although they are correct, are not really explaining themselves too well.

 

They in turn are getting frustrated since you seem to be willfully ignoring and denying things that have been thoroughly proven by science. That might not be what you think you're doing - you think everyone else is just misunderstanding you. You think they just don't understand the difference between the measurement of clocks and "real" time. But that is what you're doing. We even have technology, such as GPS, which would not work if this wasn't true. So stop being so defensive. You're not going to get anywhere if you first can't acknowledge that your notions are incorrect and open your mind a little bit. A "mile" and a "second" have no meaning outside of a specific frame of reference, and until you get used to that idea, you're not going to get anywhere. It is NOT "just clocks" and "just rulers."

 

Anyway, I don't pretend to be qualified to teach the subject, especially not in one post on some forum. There are definitely parts of I really don't understand, myself. But I think I can point in the right direction. Basically, all of relativity falls out the fact that for any possible observer, any beam of light is always observed to move at the same speed relative to that observer. Here are some thought experiments that might help you begin to appreciate the ramifications of that fact:

 

Special Relativity Thought Experiments

 

These are just involving special relativity, and don't involve acceleration, and are insufficient in themselves to address your OP. However, understanding what is going on in them is definitely a prerequisite to any kind of understanding of general relativity. So think about them carefully, and ask lots of questions. I certainly did when I was first taught SR.

[Cap'n Refsmmat]

There is one definition of a second, not two. Since I am a distance away from you right now, do you measure a second differently that I do?

Yup.

 

So c is a constant velocity of 186,000 miles per second, but a second can not be a constant?

Yup.

 

It's crazy, I know. Half of modern physics makes no sense, but somehow it's still correct.

 

Sisyphus' link looks to be rather good, by the way, so I suggest you take some time and read through it. It'll be counterintuitive, yes, but that's modern physics for you.

[Motor Daddy]

Yup.

 

 

Yup.

 

It's crazy, I know. Half of modern physics makes no sense, but somehow it's still correct.

 

Sisyphus' link looks to be rather good, by the way, so I suggest you take some time and read through it. It'll be counterintuitive, yes, but that's modern physics for you.

 

The duration of a second is the same for you or me, regardless of how far away from me you are.

 

In order for you to measure a second different than I do means that you measure the speed of light different than I do.

[Cap'n Refsmmat]

Or it means that time itself is passing differently for me. That's what relativity implies.

[Motor Daddy]

Or it means that time itself is passing differently for me. That's what relativity implies.

 

So when you measure the speed of light, since your second is different than mine, the light you measure actually travels a different distance in your second than when I measure the speed of light with my second?

[Sayonara]

So they can ask the same question repeatedly of me, and expect a different answer each time they ask? Is that what you are saying?

No, I am saying that when you repeat your proposals and the objections you receive are also repeated, that is your first clue that something is wrong. Your second clue is that all the people objecting to your proposals are in agreement. The most elegant solution to this problem is that your proposals need work, and the most reasonable place to look to decide what work they need is in the replies you have collected.

 

And again, I'm talking about the actual distance traveled, and the actual time it took to travel. There is no different reference frame after the time has elapsed, and you can't measure the distance and time until AFTER the time has elapsed.

You look like you might be inventing your own mischief here. Consider that your measurement has a duration of its own (for example, the period between a stopwatch being started and stopped). Such durations are themselves subject to frame differences.

 

There is one definition of a second, not two.

This is quite true. However, the definition of a second is a period based on arbitrarily selected events. If the measured view of those events changes, the period which defines a second changes with it within the same frame. The definition does not need to change.

 

The practical result of this is that 102 seconds measured in one frame might be measured as 906,508 seconds in another frame, despite the definition of "second" being unchanged. This is can be a very troublesome concept if you are new to relativity, but rest assured that it has been one of the most rigorously and extensively tested observations in physics.

 

Since I am a distance away from you right now, do you measure a second differently that I do?

It is not contingent on distance, but on relative velocities. Since we are in different places on the surface of the earth, we will have different velocities, and there will be a time dilation effect between your frame of reference and mine. However, due to the low velocity differences, it will be so infinitesimally small as to be - for all practical purposes - unrecordable.

 

So c is a constant velocity of 186,000 miles per second, but a second can not be a constant?

"Second" is an arbitrarily defined unit of time's passage. Rather than thinking of a second not being a second, think of time stretching or compressing in different viewpoints. If you superimpose start and end points for a "second" on that mental image, they will move as the time stretches or compresses, maintaining the internal consistency of that "second".

[Motor Daddy]

Or it means that time itself is passing differently for me. That's what relativity implies.

 

Is your second faster or slower than mine, where you are?

[DrP]

Is your second faster or slower than mine, where you are?

 

It depends how fast he is traveling relative to you.