# 1G Relativistic Rocket Ride, Wheeee

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According to the light speed episode of "The Universe" program on the History channel, .99c woud give you a very distorted view directly in front of you and you lose the distance advantage to the side. That program and these forums in the last 30 days is my total experience with relativity. But I do like to give my opinion. And I did stay at a Holiday Inn Express the other night.

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Nice. Rock on.

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I think the younger twin is the one that accelerated but am confused by "The one who doesn't accelerate. Being at rest in a gravity field is an accelerated frame, which is one of the quirky concepts of GR."

The gravity of the home planet is ignored in the twins paradox — it's assumed to be an inertial frame. The clocks are synchronized in that frame, so any gravitational dilation is "built in" to the analysis.

I posted these four twin scenarios in another thread and there were no replies. I know that 1 and 2 are true so 4 should also be true. The calculators say 3 is not true unless Jane stops separating from the Earth and waits for Dick to make a similar trip speed and acceleration wise.

Since I am wrong much of the time would someone confirm that.

1. Dick takes a space trip at relativistic speeds and when he comes back to Earth he is younger the Jane.

2. Jane doesn't want to be old so she takes a similar space trip and comes back the same age as Dick.

3. Jane wants to be younger then Dick so she starts off an a space trip. Some time later Dick decides he doesn't want to be older so rather then wait for Jane to turn around and come back, he jumps in his space ship and goes to her. They are the same age?

4. They both want to be younger and take off an similar space trips but in the opposite direction. When they get back they will be the same age even though they were in different inertial frames the entire trip. Is that right? The separation and closure during the trip was equal.

As long as the trips are identical in terms of speeds, yes. In #3, you could end up with different ages if Dick catches up with Jane by going faster.

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Thief here...

I had a similar discussion elsewhere, and it appears that aging does not halt for the traveler.

Should I leave the Earth on a 400 year journey, I would be somewhat older in body upon my return. Perhaps not a great amount older, but some aging will occur.

As for travel resulting a return to a previous year, a time before my departure, I don't think that can happen. I cannot return and find you to be younger.

Travel into the past? I'm not so sure.

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you really hit something at that speed and make another big bang on our universe .

I think mathematically it's possible -I actually thought about that before - but physically it's far from possible . at 1G of acceleration and every point of it you need more and more energy to keep you go that acceleration .

1/ million million million ...etc mistake of direction make you go in curved way .

I don't know why most people still imagine they can travel in liner way. even in the earth you traveling in curved way .

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you really hit something at that speed and make another big bang on our universe .

...at 1G of acceleration and every point of it you need more and more energy to keep you go that acceleration.

I would think in the vacuum of space a constant thrust could provide a constant 1G. Could someone elaborate on that please?

I totally agree if you hit something at relativistic speeds there will be a lot of energy created.

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I would think in the vacuum of space a constant thrust could provide a constant 1G. Could someone elaborate on that please?

1G of velocity yes, but I'm not sure - as I'm not physician- it happens with acceleration .

I will take newton's theory of action and reaction . in simple way

( there is a lot example but I will chose this one )

A and B two different of mass on the space (two different guys try pushing back together) if:

1-mass A=B ( and they push as same force this mean they separate in a same acceleration )

2-mass A>B ( and they push as same force this mean acceleration of A will be less than B )

3-mass A<B (and they push as same force this mean acceleration of A will be more than B)

even all those state and movement object ,the acceleration will be zero again until they get more force greater than before . ( vectors things)

maybe the relativity has related of these things

that was all what I imagine of the movement in the space .so it just theories in my head .

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that was all what I imagine of the movement in the space .so it just theories in my head .

As long as there is thrust pushing the rocket it will accelerate in the vacuum of space. Inertia says a body in motion will stay in motion in a straight line unless acted on by an outside force. So if there is thrust (outside force), the rocket will continue accelerating towards the speed of light but never make it. There will be no forces acting on the rocket except for the thrust (discounting space dust and gravity). So newton's theory of action and reaction fits well.

Where are the experts??

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Where are the experts??

Not at your beck and call, obviously.

Forces get tricky in relativity

http://en.wikipedia.org/wiki/Special_relativity#Force

If you look at the fourth equation in that section, you'll see that Force and acceleration no longer have a linear dependence.

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As long as there is thrust pushing the rocket it will accelerate in the vacuum of space. Inertia says a body in motion will stay in motion in a straight line unless acted on by an outside force. So if there is thrust (outside force), the rocket will continue accelerating towards the speed of light but never make it. There will be no forces acting on the rocket except for the thrust (discounting space dust and gravity). So newton's theory of action and reaction fits well.

Where are the experts??

it's better to explain it in a low motion physics . try to imagine your are in space .and there is a road ( resistant of road=0) and your are in a bicycle . you started moving your legs and spinning the pad .your bicycle will started moving and you will slowly begin spin the pad faster and faster so I have a five things .

1- is there any limit of your spinning ?

2- did you reach your limit of spinning?

3- at point your are spinning the pad at that limit ? is your bicycle accelerating ?

4- now stop spinning the pad did your bicycle stop ( don't forget you are still in a space without resistant ) so there is only velocity

my point there is three states of your position .

less spinning

equal spinning

more spinning

so ( less or equal spinning will not accelerate your bicycle ) rather than ( more spinning will accelerate it for sure ).

spinning = force

((about the resistant things :if resistant exist it's only make you slower but if it's not exist it doesn't mean you will go faster you only will go in actual speed ))

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Not at your beck and call, obviously.

Forces get tricky in relativity

http://en.wikipedia.org/wiki/Special_relativity#Force

If you look at the fourth equation in that section, you'll see that Force and acceleration no longer have a linear dependence.

2 hours and 4 minutes, not too bad. (you know I appreciate your help)

Some of that math I could probably actually do but my first problem is I do not know what each character represents. It wasn't in my "Relativity for dummies" book. I have figured out a few but is there a complete list some where?

Sorta like

c = speed of light

v = velocity

V = volume ??

funny looking Y = ??

Should I be looking at this problem like E=MC^2? The faster you go, the more energy it takes and that is why it isn't linear? I keep thinking that at any time you shut the engines off you would be at rest and inertia would keep you going. Starting your engines again would quickly get you to 1G acceleration. Sort of like starting over again. Arn't you either at rest or accelerating? Even when the math is done it only gives you an answer and not a good visual of what is happening or why. Thanks

Merged post follows:

Consecutive posts merged
it's better to explain it in a low motion physics . try to imagine your are in space .and there is a road ( resistant of road=0) and your are in a bicycle . you started moving your legs and spinning the pad .your bicycle will started moving and you will slowly begin spin the pad faster and faster so I have a five things .

1- is there any limit of your spinning ?

2- did you reach your limit of spinning?

3- at point your are spinning the pad at that limit ? is your bicycle accelerating ?

4- now stop spinning the pad did your bicycle stop ( don't forget you are still in a space without resistant ) so there is only velocity

my point there is three states of your position .

less spinning

equal spinning

more spinning

so ( less or equal spinning will not accelerate your bicycle ) rather than ( more spinning will accelerate it for sure ).

spinning = force

((about the resistant things :if resistant exist it's only make you slower but if it's not exist it doesn't mean you will go faster you only will go in actual speed ))

You speak my kind of math.

Are you saying that less spinning and equal spinning would produce the same results (constant velocity)? And more spinning is needed for acceleration?

When you take all resistance away it would seem that more spinning would not require additional force, just a higher gear. I guess the part that confuses me is I see everything as at rest in space so force would be force. How else can you look at it in a metric without an ether? If you have any comments on the post above this one I would appreciate it. I relate to your words and appreciate it. I have my good areas but formal training in physics is not one of them, as you can tell.

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if you've got some time, and haven't noticed yet, you might search you tube for "math lectures" and physics lectures too. MIT is awesome for posting these lectures

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if you've got some time, and haven't noticed yet, you might search you tube for "math lectures" and physics lectures too. MIT is awesome for posting these lectures

That might work if I can find the right one. A glossary of the characters used in these equations would also be nice. I need to get up to speed on math if I am going to keep playing this game.

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it would be nice if it were easier to tell whats in the lectures but they sure beat tv so i just watch the whole series(click related when you find one you like).

between that (really basic)page and the links under "see also" you can probably find any symbols you're looking for

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You speak my kind of math.

Are you saying that less spinning and equal spinning would produce the same results (constant velocity)? And more spinning is needed for acceleration?

When you take all resistance away it would seem that more spinning would not require additional force, just a higher gear. I guess the part that confuses me is I see everything as at rest in space so force would be force. How else can you look at it in a metric without an ether? If you have any comments on the post above this one I would appreciate it. I relate to your words and appreciate it. I have my good areas but formal training in physics is not one of them, as you can tell.

yes that exactly what I meant before .

lets see it in other side ,you can't get a full energy from a constant force - as mass it not changing (again relativity things)- maybe it's more complicated.

I think force and energy are two sides of same coin .I mean if the force are constant how does you will get more and more energy ?

for now , this is the only things I can say .

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2 hours and 4 minutes, not too bad. (you know I appreciate your help)

Some of that math I could probably actually do but my first problem is I do not know what each character represents. It wasn't in my "Relativity for dummies" book. I have figured out a few but is there a complete list some where?

Sorta like

c = speed of light

v = velocity

V = volume ??

funny looking Y = ??

Gamma. It's the term that tells you the amount of time dilation or length contraction

$\gamma = \frac{1}{\sqrt{1-\frac{v^2}{c^2}}}$

I didn't see a V, just v for speed

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it would be nice if it were easier to tell whats in the lectures but they sure beat tv so i just watch the whole series(click related when you find one you like).

between that (really basic)page and the links under "see also" you can probably find any symbols you're looking for

The "Greek letters used in mathematics" link helped some. I will post a list I started in my next post hoping people will add to or make corrections. Thanks

Merged post follows:

Consecutive posts merged
Gamma. It's the term that tells you the amount of time dilation or length contraction

$\gamma = \frac{1}{\sqrt{1-\frac{v^2}{c^2}}}$

What I think I am seeing (here and your other Force link) is Force required to accelerate is somewhat proportional to time dilation. Time dilation becomes very nonlinear (like a bell curve) as relativistic speeds are increased.

1a. Is that right?

1b. The acceleration of a constant Force rocket would slow its acceleration as speed increased?

2. At any point the engines were shut down the rocket would become an inertial frame and maintain speed relative to its surroundings (not counting space dust and gravity influence)?

3. Why couldn't you restart the engines and accelerate out of your inertia frame?

I started a list. If anyone sees any errors or would like to add to it please feel welcome.

p = Density

P = Momentum

Y = Lorentz factor

t = Proper time

T = Time in another frame

c = Speed of light

u = velocity as observed in the reference frame where time t is measured

v = velocity

V = Volume

F = Force

G = Gravitational constant

m = Mass

d = Distance

a = Acceleration

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next thing ya know yer sayin stuff like Υ

this is a guess but i'd say when you stopped accelerating you are in an inertial frame but your mass has increased so now you need more power for the same acceleration.

Edited by moth
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next thing ya know yer sayin stuff like Υ

this is a guess but i'd say when you stopped accelerating you are in an inertial frame but your mass has increased so now you need more power for the same acceleration.

This math agrees with you I think:

p=y(rest mass)v ---- density=time dilation(rest mass)v

but

If you are at rest in your inertial frame, who is to say what your speed is. Why couldn't the length contraction you see come from the objects around you moving and not you. This keeps coming up to haunt me like the twin paradox. Whoever did the initial accelerating is moving but that makes no sense to me in a metric without an ether.

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If you are at rest in your inertial frame, who is to say what your speed is. Why couldn't the length contraction you see come from the objects around you moving and not you. This keeps coming up to haunt me like the twin paradox. Whoever did the initial accelerating is moving but that makes no sense to me in a metric without an ether.

maybe it has to do with the one-way nature of time. even though it should look the same whether you think of it as the ship accelerating away from earth, or earth accelerating away from the ship,you got in the ship and did something so everything changed for you.

if we could calculate our "true" length contraction we would know our velocity relative to a universal frame, but due to our limited perception we can only measure the change in our length contraction

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maybe it has to do with the one-way nature of time. even though it should look the same whether you think of it as the ship accelerating away from earth, or earth accelerating away from the ship,you got in the ship and did something so everything changed for you.

if we could calculate our "true" length contraction we would know our velocity relative to a universal frame, but due to our limited perception we can only measure the change in our length contraction

I think tomorrow we will see a reply that says "the acceleration broke the symmetry". I need to think about that I guess.

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symmetry would seem to be a fundamental property, proof of rotation or translation in other dimensions.

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"force would be force" it's true but there is a less and a more force

at 1st newtons law ". Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it."

as based of your theories and 1st newton's law you can move 1000,000 tons on space with one finger if and only if that is true then your theories will be true .

but I can't see that happening . our space most of it is empty and there is a moon and it's on an empty space without any resistant , that moon has no atmosphere so if it's hitting by Meteorite ( as it's a moving object it means it has a force or at least what Newton thinks) it should force the moon to accelerate !!! why would that not happening .

still all the three Newton's laws confusing us

I don't know what does Issac Newton mean by "external force is applied to it" ?

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What I think I am seeing (here and your other Force link) is Force required to accelerate is somewhat proportional to time dilation. Time dilation becomes very nonlinear (like a bell curve) as relativistic speeds are increased.

1a. Is that right?

1b. The acceleration of a constant Force rocket would slow its acceleration as speed increased?

2. At any point the engines were shut down the rocket would become an inertial frame and maintain speed relative to its surroundings (not counting space dust and gravity influence)?

3. Why couldn't you restart the engines and accelerate out of your inertia frame?

Gamma tends to infinity as you approach c. It's not Gaussian.

You would maintain your speed if you shut the engines down, and if you restarted them you would begin to accelerate again.

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"force would be force" it's true but there is a less and a more force

at 1st newtons law ". Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it."

as based of your theories and 1st newton's law you can move 1000,000 tons on space with one finger if and only if that is true then your theories will be true .

but I can't see that happening . our space most of it is empty and there is a moon and it's on an empty space without any resistant , that moon has no atmosphere so if it's hitting by Meteorite ( as it's a moving object it means it has a force or at least what Newton thinks) it should force the moon to accelerate !!! why would that not happening .

still all the three Newton's laws confusing us

I don't know what does Issac Newton mean by "external force is applied to it" ?

If anything it would be slowing the moon down since meteorites would strike more frequently on the side of the direction of motion rather than catching up to strike on the other side. Meteorites are mostly tiny and far outweighed by other effects, sort of like trying to knock the ball off of a large stone kugel by throwing stones at it (you probably couldn't even lift a stone large enough to noticably affect it).

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