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why you can't observe light speed as half c
if you travel at half c?


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because you are slowed down, due to time being streatched. therefore it appears to be the same speed to you as if you were at 0 c


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Would i be slowed down instantly?before time stretching(even though i duno what it is)slows me down,i can't observe any change in c?


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It goes deeper than this. The basic assumption of relativity is that all refence frames moving with constant velocities relative to each other will be experienced by an observer within any one of them as being stationary; i.e. the observer will not be able to perform ANY experiment within his/her reference frame from which he/she can conclude that he/she is moving. This requires that each observer within whichever reference frame must measure the same speed for light. If not the observer would be able to conclude that he/she is moving. Thus if you move with a speed of c/2 relative to a reference frame, you will experience the reference frame moving with you as being stationary and you will thus measure the speed of light as c; however, an observer within the reference frame relative to which you are moving with c/2 will see you catching up on light because he/she also measures light speed as c relative to his/her reference frame as well as your speed of c/2.

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Quote:
Originally posted by little cotton:
Would i be slowed down instantly?before time stretching(even though i duno what it is)slows me down,i can't observe any change in c?
the faster you go the more time dialation occurs. its relative.


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Quote:
Originally posted by dehammer:
Quote:
Originally posted by little cotton:
Would i be slowed down instantly?before time stretching(even though i duno what it is)slows me down,i can't observe any change in c?
the faster you go the more time dialation occurs. its relative.
Time dilation does not occur within the reference frame moving with you. You still measure the same time. It only seems that time dilation is occurring in your reference frame when observed by observers in reference frames moving relative to you. The faster an observer moves relative to you, the more he/she will conclude that the time in your reference frame ticks away slower. From your perspective you will conclude that the time in his/her reference frame is ticking slower.

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Quote:
Originally posted by Johnny Boy:
Quote:
Originally posted by dehammer:
Quote:
Originally posted by little cotton:
Would i be slowed down instantly?before time stretching(even though i duno what it is)slows me down,i can't observe any change in c?
the faster you go the more time dialation occurs. its relative.
Time dilation does not occur within the reference frame moving with you. You still measure the same time. It only seems that time dilation is occurring in your reference frame when observed by observers in reference frames moving relative to you. The faster an observer moves relative to you, the more he/she will conclude that the time in your reference frame ticks away slower. From your perspective you will conclude that the time in his/her reference frame is ticking slower.
please explain this to me. a pair of twins get separated, one going to alpha century in a space ship. the other staying on earth.

according to what you wrote the one in the space ship will see that the person that stayed on earth is slowing down. that means that after he makes the round trip from alpha century at 3/4 light speed (about 10 years). his brother who stayed on earth will only be 4 years older while he the brother that went on the trip will be 10 years older.

the person that sees his brother leave in the space ship will see his brother slow down, and will only age about 4 years in the 10 years it takes the ship to get back.

please explain, there are only two of them. how can they both see the other not age, while they do.


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I think you mean Alpha Centauri. And from what I understand, the brother who stays behind will age ten years to his traveling brother's four. I think this is what you said but the way you said it is confusing. It looks like you're saying the traveling brother ages ten years to the left behind brother's four years.

Clarity, in language, is everything.

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no, that is what im understanding the others to say. and yes, i could not find how to spell the name, even after googling it. the way you said is the way i understand it, but going by several things said here, that is what others claim would happen.


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Quote:
Originally posted by dehammer:
please explain this to me. a pair of twins get separated, one going to alpha century in a space ship. the other staying on earth.

according to what you wrote the one in the space ship will see that the person that stayed on earth is slowing down. that means that after he makes the round trip from alpha century at 3/4 light speed (about 10 years). his brother who stayed on earth will only be 4 years older while he the brother that went on the trip will be 10 years older.

the person that sees his brother leave in the space ship will see his brother slow down, and will only age about 4 years in the 10 years it takes the ship to get back.

please explain, there are only two of them. how can they both see the other not age, while they do.
Where you are going wrong here, and don't worry you are in good company (Both Sir Martin Rees the Astronomer Royal and Kip Thorne a highly respected theoretical physicist have made the same mistake in books they have written), is to think that the time dilation you observe in the framework moving with a speed v relative to you is also valid within that framework. It is not, it is only valid within your framework. Similarly owing to symmetry a person in the framework moving with a speed v relative to you will see YOU moving with a speed v relative to him. Thus he will see your time running slower relative to his time. In fact time runs at the same rate (the proper time) within both reference frames. This must be so because both reference frames are equivalent for any physical experiment; for example, the decay time of a radioactive isotope must be the same in both reference frames; although if you measure the decay time of isotopes moving relative to you, you will measure a longer time. This is why in special relativity you have a paradox. This problem can only be addressed by general relativity. The fact is that the actual times that elapsed can only be compared by coordinating the twin's clocks just before the one leaves, and then comparing them again when the twin returns. The twin that accelerated the most in the process of leaving and returning will be the youngest because gravity and acceleration are the only factors that can affect the actual clockrate.

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"why you can't observe light speed as half c
if you travel at half c?"

To put it as simply as possible:
Because the length of your 'measuring stick` is changed.

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Quote:
Originally posted by Pragmatist:
"why you can't observe light speed as half c
if you travel at half c?"

To put it as simply as possible:
Because the length of your 'measuring stick` is changed.
Relative to which reference frame? You only observe a change in length when the measuring stick travels with a speed v relative to you. When you travel with the measuring stick it is not shorter at all; because it is then at rest relative to you.

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temporily, the measureing stick is longer.


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dehammer wrote:
"temporily, the measureing stick is longer."

No. You can not segregate space and time.


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Quote:
Originally posted by DA Morgan:
dehammer wrote:
"temporily, the measureing stick is longer."

No. You can not segregate space and time.
so your saying that despite everything others have said that there is no time dialation??????


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No. I am saying that you don't understand the concept. Your description: "temporily, the measureing stick is longer." is incorrect.


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Quote:
Originally posted by dehammer:
Quote:
Originally posted by DA Morgan:
dehammer wrote:
"temporily, the measureing stick is longer."

No. You can not segregate space and time.
so your saying that despite everything others have said that there is no time dialation??????
Time dilation is observed BY YOU WITHIN YOUR REFERENCE FRAME when observing events within a reference frame moving RELATIVE TO YOU. Relative to the latter reference frame there is no time dilation. A muon created in cosmic rays does not decay slower within the reference frame moving with it. It is only observed to decay slower within earth's reference frame. The mass of a particle does not increase relative to the reference frame moving along with it, only relative to reference frames within which it is observed as moving.

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Quote:
Originally posted by Johnny Boy:
Quote:
Originally posted by dehammer:
Quote:
Originally posted by DA Morgan:
dehammer wrote:
"temporily, the measureing stick is longer."

No. You can not segregate space and time.
so your saying that despite everything others have said that there is no time dialation??????
Time dilation is observed BY YOU WITHIN YOUR REFERENCE FRAME when observing events within a reference frame moving RELATIVE TO YOU. Relative to the latter reference frame there is no time dilation. A muon created in cosmic rays does not decay slower within the reference frame moving with it. It is only observed to decay slower within earth's reference frame. The mass of a particle does not increase relative to the reference frame moving along with it, only relative to reference frames within which it is observed as moving.
i know that, but the question was why could you not see light moveing less than light speed since you were already moving at half light. so when your 'measureing stick' is temporely (not temporarily, but thought time) is dialated by the fact that you are feeling the effects of the dialation, the appearance of light still is the speed of light.

since you do not believe you have to read something for content, you missed what was being said.


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Which frame fo reference is the light in?

Depending on the direction of the light in relation to your movement, it will ether have a longer or shorter wavelength due to the doppler effect. This would imply that you could estimate your velocity based on the background radiation (Since the background radiations temperature is a bit lumpy you measurement could not be completely an accurate).

Actually your measuing stick is light. Normal time dilation is just an illusion based on the relative movement between you and the object being observed in the time it takes light to travel from the object to you.
I don't understand the time dilation caused by acceleration which is an actual difference in the rate at which time flows.


One other thing I don't understand is how light knows how fast it is going, since it always goes at the same speed (makes more sense to think of the universe "knowing" how fast light is travelling).

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Quote:
Originally posted by dehammer:
[QUOTE]i know that, but the question was why could you not see light moveing less than light speed since you were already moving at half light. so when your 'measureing stick' is temporely (not temporarily, but thought time) is dialated by the fact that you are feeling the effects of the dialation, the appearance of light still is the speed of light.

since you do not believe you have to read something for content, you missed what was being said.
Because relative to your reference frame you are not moving; but stationary. You can only move relative to another inertial reference frame which moves relative to your reference frame (within which you are stationary). An observer in the other reference frame will be able to observe you as moving with 1/2c. Your experience is that you are stationary and therefore you will keep on measuring light speed as c relative to your reference frame; just as the other observer will, in turn, measure light speed as c within his reference frame (within which he is stationary. Why it is so has always been to me amazing. I believe, however, that it relates to the amount of "bending" of the fourth dimension relative to space. If space-time is Euclidean, change can probably not manifest in such an Euclidean space because changes along the axes are linearly independent. So if the fourth dimension is not bent, one will not be able to differentiate with time; nothing can then change. Maybe, as the Universe expands, the time axis will unbend and the speed of light (far away from massive objects) might change in magnitude; probably going to zero at the end of time.

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