Wouldn’t time dilation govern a speed limit?

[ynot]

If we were talking about Special Relativity then:
According to an outside observer (you) everything that happens in an accelerated frame of reference (the accelerated rocket) is time dilated.
According to the rocket there is nothing unusual happening in its own frame of reference (but if it had an observer they would see you as being time dilated).

Yes, a person in the rocket would observe a normal acceleration and I would observe a slowed acceleration (slower than the rocket persons). The greater the extent of dilation, the greater the difference between the person on the rockets observed acceleration and my observed acceleration of the rocket.

But you have an accelerating frame of reference here so that is General Relativity which is not my area of expertise. I suspect that you will actually measure the same acceleration, e.g. the rocket thrust is measured in mass/second. So you measure the mass that is output by the rocket in a certain period of time to get the rocket's acceleration. Time dilation means that the time you measure goes up by the gamma factor. But the mass you measure also goes up by the gamma factor. Dividing the 2 means that the acceleration does not change from your point of view.

Are you saying would I observe two different time dilations of the rocket depending what relativity hat I had on?

Regardless of how the time dilation was created, or what the extent of the dilation is, as long as dilation occurs, do you agree that the rocket would accelerate less for me than a person on the rocket?

 

[Reality Check]

Are you saying would I observe two different time dilations of the rocket depending what relativity hat I had on?

In SR you definitely see the same acceleration since gamma cancels out. I would expect roughly the same in GR (but this is only a guess).

Regardless of how the time dilation was created, or what the extent of the dilation is, as long as dilation occurs, do you agree that the rocket would accelerate less for me than a person on the rocket?

You would observe the rocket accelerating less compared to a person on the rocket.

 

[ynot]

In SR you definitely see the same acceleration since gamma cancels out. I would expect roughly the same in GR (but this is only a guess).

So in SR there would be no time dilation? Or there would be but I wouldn’t be able to see it until the rocket came home?

You would observe the rocket accelerating less compared to a person on the rocket.

That seems to contradict what you just said. However, lets assume that I would see a slower rate of increased Acceleration than the person on the rocket, regardless of GR or SR. Effectively from my perspective the dilation has “robbed” some of the increased acceleration. If the extent of dilation was sufficient, it would “rob” all of the increased acceleration, and from my perspective the rocket would travel at a constant speed. And this would be so regardless of any amount of additional acceleration applied to the rocket from the rocket persons perspective. In other words, time dilation would have governed a maximum speed limit for the rocket from my perspective.

 

[Reality Check]

So in SR there would be no time dilation? Or there would be but I wouldn’t be able to see it until the rocket came home?

In SR there is time diation.

That seems to contradict what you just said. However, lets assume that I would see a slower rate of increased Acceleration than the person on the rocket, regardless of GR or SR. Effectively from my perspective the dilation has “robbed” some of the increased acceleration. If the extent of dilation was sufficient, it would “rob” all of the increased acceleration, and from my perspective the rocket would travel at a constant speed. In other words, time dilation would have governed a maximum speed limit for the rocket from my perspective

The problem is that you are just thinking about time dilation. What about the mass increase?

 

[ynot]

In SR there is time diation.



The problem is that you are just thinking about time dilation. What about the mass increase?

Yes, I’m just considering time dilation. If mass increase effects the dilation so what? I’m considering time dilation as I observe it (mass increase, warts and all .

 

[Reality Check]

Yes, I’m just considering time dilation. If mass increase effects the dilation so what? I’m considering time dilation as I observe it (mass increase, warts and all .

Then as the rocket gets closer to the speed of light its time dilation will increase. You are not doing any measurement of the acceleration and so cannot say what the acceleration of the rocket is. If you assume that the rocket accelerates constantly then you will see the acceleration decrease.

 

[PixyMisa]

And exactly how does “Time would pass more slowly for them” not also mean that they would move more slowly relative to an observer not travelling so fast? Slower time = slower movement. I have the problem?

Yes, you have the problem.

You have it backwards.

Slower time = faster movement!

Let's ignore time dilation for the moment, and assume that your clock is running slow because you filled it with butter. Now it only advances 1 hour for every 24 as measured by normal clocks.

You're on a train travelling (as other people measure it) at 50 miles per hour. But when you measure the distance travelled in one hour by your clock, you find you have travelled 1200 miles.

In time dilation, relative to an outside observer, your local clock runs slow, and your speed is unchanged. Because your clock is the basis for all your measurements, as far as you are concerned, your clock is the same as always, and your speed has increased.

 

[ynot]

Then as the rocket gets closer to the speed of light its time dilation will increase.

Yes

You are not doing any measurement of the acceleration and so cannot say what the acceleration of the rocket is.

Yes - Measuring the acceleration is not important to what I‘m suggesting.

If you assume that the rocket accelerates constantly then you will see the acceleration decrease.

Yes -And if the time dilation reaches a point where it “robs” me of all the rockets acceleration, the rocket won’t increase its speed as I see it. It's not important to me where that point is, just that it exists.

 

[ynot]

Yes, you have the problem.

You have it backwards.

Slower time = faster movement!

Let's ignore time dilation for the moment, and assume that your clock is running slow because you filled it with butter. Now it only advances 1 hour for every 24 as measured by normal clocks.

You're on a train travelling (as other people measure it) at 50 miles per hour. But when you measure the distance travelled in one hour by your clock, you find you have travelled 1200 miles.

In time dilation, relative to an outside observer, your local clock runs slow, and your speed is unchanged. Because your clock is the basis for all your measurements, as far as you are concerned, your clock is the same as always, and your speed has increased.

Seems to me that it’s six of one and half a dozen of the other. Depends on how you want to view it. Either way, it’s not important to what I’m trying to say.

Always wondered why the Six Million Dollar Man went in to slow motion when he was running. It’s because he was going faster!

 

[PixyMisa]

Seems to me that it’s six of one and half a dozen of the other. Depends on how you want to view it. Either way, it’s not important to what I’m trying to say.

It's a direct answer to your question. You are dividing when you should multiply.

If you honestly think that there's no difference between travelling at 2 miles per hour and 1200, then you'll probably enjoy swimming from New York to London.

 

[PixyMisa]

Yes -And if the time dilation reaches a point where it “robs” me of all the rockets acceleration, the rocket won’t increase its speed as I see it. It's not important to me where that point is, just that it exists.

That point is the speed of light.

But in your second post, you suggested that beyond a certain speed B (the moving body) would slow down and stop relative to A. This is wrong in every way it is possible to be wrong, including self-contradiction.

 

[ynot]

That point is the speed of light.

I disagree. The speed of light would theoretically (given it’s impossible to reach) rob me of all the speed of the rocket. I’m only talking about losing the amount of speed that the rocket is increasing its speed by. That point would be less than the speed of light.

But in your second post, you suggested that beyond a certain speed B (the moving body) would slow down and stop relative to A. This is wrong in every way it is possible to be wrong, including self-contradiction.

Now you’re just being persinickety!

As I said in post #19 “I have never said that the speed of light or 100% time dilation COULD be achieved. I have simply speculated WHAT IF it could. (let’s pretend).”

 

[Reality Check]

I disagree. The speed of light would theoretically (given it’s impossible to reach) rob me of all the speed of the rocket. I’m only talking about losing the amount of speed that the rocket is increasing its speed by. That point would be less than the speed of light.

By "losing the amount of speed that the rocket is increasing its speed by" I assume you mean the acceleration of the rocket will decrease.

This is the classic example of a rocket under constant acceleration. An outside observer of the rocket never sees the rocket reach the speed of light and its acceleration decreases towards zero (but never reaches zero).

 

[PixyMisa]

I disagree. The speed of light would theoretically (given it’s impossible to reach) rob me of all the speed of the rocket.

No!

It would rob you of your acceleration. Speed, relative to a stationary observer, would be the speed of light, as stipulated. Speed, as observed by the traveller, would be infinite.

I’m only talking about losing the amount of speed that the rocket is increasing its speed by.

Acceleration. Okay then, use the word acceleration if that's what you mean.

That point would be less than the speed of light.

No, that point is precisely the speed of light.

Now you’re just being persinickety!

As I said in post #19 “I have never said that the speed of light or 100% time dilation COULD be achieved. I have simply speculated WHAT IF it could. (let’s pretend).”

No, that's not the problem. If you meant acceleration, rather than speed, then what you are saying makes a lot more sense.

But you did say:

B would therefore stop moving compared to A. Before this happened however, B would go through a process of slowing down compared to A, and at a particular point the slowing down would mean that B would be unable to sustain the increasing acceleration.

That really looks like you are talking about speed in the first part, and you only mention acceleration right at the end. If you meant all along that acceleration decreases relative to a stationary observer as you approach the speed of light, then you are absolutely correct. And yes, this can be expressed as a function of time dilation if you want.

But remember too that time dilation is relative. To you, on the ship, your clock is the correct one, everyone else has speeded up, and your acceleration is unaffected.

 

[ynot]

By "losing the amount of speed that the rocket is increasing its speed by" I assume you mean the acceleration of the rocket will decrease.

Yes, from my perspective - You agreed with this in post #26 - “If you assume that the rocket accelerates constantly then you will see the acceleration decrease.” (didn’t you?)

This is the classic example of a rocket under constant acceleration. An outside observer of the rocket never sees the rocket reach the speed of light and its acceleration decreases towards zero (but never reaches zero).

Yes - I know!

 

[Reality Check]

Yes, from my perspective - You agreed with this in post #26 - “If you assume that the rocket accelerates constantly then you will see the acceleration decrease.” (didn’t you?)


Yes - I know!

That example points out that you cannot consider time dilation alone. Distance also changes (and mass).

 

[ynot]

No!

It would rob you of your acceleration. Speed, relative to a stationary observer, would be the speed of light, as stipulated. Speed, as observed by the traveller, would be infinite.

When I say “Me” I am the stationary observer. I’m not the person in the rocket. Everything that I’ve been saying is from the position of the stationary observer only.

Acceleration. Okay then, use the word acceleration if that's what you mean.

Or you could read the “WARNING - written by a layman” at the top of my first post and stop being so persnickety.

No, that point is precisely the speed of light.

I still disagree.

No, that's not the problem. If you meant acceleration, rather than speed, then what you are saying makes a lot more sense.

“WARNING - written by a layman” (me that is)

But you did say:

That really looks like you are talking about speed in the first part, and you only mention acceleration right at the end. If you meant all along that acceleration decreases relative to a stationary observer as you approach the speed of light, then you are absolutely correct. And yes, this can be expressed as a function of time dilation if you want.

I find it hard to believe that your ability to understand what I’ve been trying to say has been confused by a single word.

But remember too that time dilation is relative. To you, on the ship, your clock is the correct one, everyone else has speeded up, and your acceleration is unaffected.

I’m not, and never was on the ship!

 

[PixyMisa]

When I say “Me” I am stationary observer. I’m not the person in the rocket. Everything that I’ve been saying is from the position of the stationary observer only.

Whatever. The point is that things look different for other observers.

Or you could read the “WARNING - written by a layman” at the top of my first post and stop being so persnickety.

Distinguishing between speed and accelertion is fundamental to the question. As I said, if you talk about speed when you mean acceleration, none of it makes any sense.

I still disagree.

With what?

“WARNING - written by a layman” (me that is)

Yeah.

I find it hard to believe that your ability to understand what I’ve been trying to say has been confused by a single word.

I find it hard to believe that you don't know the difference between speed and acceleration, and yet you're arguing about the predictions of relaivity.

I’m not, and never was on the ship!

I put you there. Deal with it.

 

[Reality Check]

That example points out that you cannot consider time dilation alone. Distance also changes (and mass).

To make this clearer: In the OP you ask about "wouldn’t it also slow the rate of the very speed that was causing the time dilation".
So you want the outside observer to calculate "the rate of the very speed that was causing the time dilation" so that they can see if it slows. But you only allow them to consider the time dilation and not also the length dilation. How can they then calculate a correct acceleration?

 

[sol invictus]

The accelerating rocket is better as it represents an actual example. I’m suggesting that if a spaceship that accelerates away from me becomes time dilated (relative to me), then the thing that gives it the energy to accelerate (the thrust of the rocket) becomes time dilated (relative to me). This means (to me) that the speed of the thrust is slowed (relative to me) and consequently the acceleration is slowed (relative to me). If anyone disagrees with this please explain why non-mathematically.

This is perfectly correct. What's the problem?

As you say here, the acceleration slows down, and it slows in a way that causes the velocity to approach a limit. Since you won't allow math we can't show you what that limit is, but it should be intuitively obvious that it's c (since that's the point where the acceleration goes to zero).