Science a GoGo's Home Page Forums General Discussion General Science Discussion Forum i just duno why you can't observe light speed as half c

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

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

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?

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.

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.

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.

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.

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.

"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.

temporily, the measureing stick is longer.

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??????

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

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.

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).

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.

no actually your moving in relationship to light. light moves at a constant, which means its something that can be measured at all speed.

Light moves at a constant relative to what? The point of relativity is that light has the same speed c relative to any inertial reference frame. Thus even if another inertial reference frame moves with 0.8c relative to you, a person in that reference frame will still measure light speed as c relative to his reference frame.

An excellent explanation that dehammer still won't understand.

Thanks, you nearly make me feel guilty about what I have just posted about you. I believe that we should still be able to have a true scientific discourse.

Best regards,
Johnny Boy

I do too.

I too try to be objective.

lets see. person a is moving away from person b at .8 speed of light, and light headed in the opposite direction is moving away from him at speed of light so the light is moving away from person a (who has not changed his speed at all) at 1.8 times the speed of light? no. its the perception that is the key. it would appear to person b that the light is moving away from him at light speed, but the light would still be moving away from person a at the same speed. he never altered his movement. light never sped up. the light is moving the same speed for both of them. just they perceive it differently.

The fact that person a is moving at 0.8c from person b and experiences light moving away from him at light speed c, does NOT mean that person b measures a light speed of 1.8c in his reference frame. This is the whole point of special relativity. When measuring light speed in your inertial reference frame (within which you are stationary) you will measure the speed of light as c notwithstanding the speed at which the light source is moving relative to you. Speeds cannot be added linearly when applying special relativity.

then explain how the same photon can be moving at two different speeds at the same time. it cant. person b will see the light speed move at a different speed because his perception of time outside of the ship has been slowed. that is what that means. not that there are two different photons moving at two different speed or that the photon moves at two different speeds.

the only other possibility is that every person is in his or her own universe and everything is duplicated.

please explain in the normal universe how the same thing can move at two different speeds at the same time. it does not matter how special you make it, it cant be two places at the same time. the perception is what you are missing. each person moves at a different rate though time, based on how the time is dilated for them.

ive had a number of armchair scientist try to explain it, but none of them can explain that one point and keep repeating the same thing "its special". a real scientist (and ive read what they say) has no problem with it. nor, if you read the theory without preconcieved ideas, would you. there is only one light speed (though a given medium), and it is not based on anyones perception. your perception of it is based on your speed in relation to it, not vice versa. man is not that important in this universe. we are not masters of it, nor the center of it. it does not base its actions on our desires.

Dear dehammer,

I am not going to quote your arguments but direct the attention of readers to your last posting. In order to measure anything, one must first have a reference frame. To say that anything is stationary one must specify in which reference frame. In pre-Galilean times it had been believed that the earth must be stationary because other objects fall down to it and then become stationary. Galileo pointed out that you can also be stationary when sitting on your deckchair on a moving ship. Thus being stationary is a relative concept; i.e. a will see b as moving while b will be convinced that he is stationary while a is moving. Galileo pointed out that if you are moving with a constant speed, you cannot do any mechanical experiment, within the reference frame within which you are, to determine wether you are moving or not.

After Galileo, up to the time of Einstein, it was, however, still believed that there exists a reference frame that is uniquely stationary. Maxwell's equations led the scientific community to believe that this framework is the ether that fills the whole universe and within which light waves manifest. Experiments were then devised to test what the speed of the earth is relative to the ether. They could not measure any speed and found that they caould (maybe) explain it by postulating an "ether drag" which, in turn, led them to the Lorentz transformations of coordinates and time. Experiments to measure the speed of the earth relative to the ether were, however, doomed from the start. Why? Because Maxwell's equations give the same speed c, notwithstanding which reference frame you use. Einstein was clever enough to bring this in relationship with Galileo's principle of relativity by stating that when you are moving with a constant speed there is no experiment whatsoever, even measuring light speed, that one can use to determine wether one is moving or not.
He then showed that this assumption can be used to derive the Lorentz transformation; which, in turn, can be used to prove that light speed measured relative to inertial reference frames moving with constant speeds relative to each other, will always be equal to c within any of these reference frames. So far this conclusion, no matter how strange to us, has not yet been experimentally found to be wrong. Therefore, until experimentally proved otherwise, this is the way nature is. That is the way science looks at the world; what we in our small human minds consider logical might not be, and therefore "our logic" has to be verified by experiment.

dehammer wrote:
"then explain how the same photon can be moving at two different speeds at the same time."

Tsk tsk tsk. Did you sleep through classes in high school? This question evidences a complete lack of even the most basic understanding of high school physics.

The photon is not moving at two different speeds. Neither is this is not a question of speed. It is a question of space-time: one entity.

in otherwords you are of the believe that each person is the center of his or her own universe and everything else is just there for him. must be very lonely being the only thing in your universe.

dehammer wrote:
"in otherwords you are of the believe that each person is the center of his or her own universe"

Since you refuse to acknowledge your ESL status ... the word is "belief" not "believe."

No. I believe that Einstein's formulation of relativity is the most accurate description of objective reality. I can't recall him ever stating what you did.

So, very simply put, you need to educate yourself because I am not going to try to teach a high-school physics class to you here at SAGG. And neither is anyone else.

ive read the theory, ive also had a teacher that believed like you that each person was in his own universe. he also believe that a vertical axis windmill did not need to move.

you see thats the problem. people who can do, those that cant teach, yet they still expect others to believe that they know everything. I dont have the link right now so i will not expect you to listen to this (after all you believed that the guy that you posted a link to said that the heavier weight of water added to the the ocean when ice melted on the ocean floor would push the lighter weight of land that had loss the ice down while everyone else read that it would push it up). I read where a researcher (one of those that actually worked with the theory) took the time out to answer a bunch of question for a high school science club. HE complained about teachers teaching it wrong.

the best way to understand it, is not to let others tell you what it means but to read it yourself. i have, you should try it. At no point does Einstein say that there would be more than one speed of light. HE said that the speed of light was set. Everything else was related to it. not vice versa.

dehammer wrote:
"ive read the theory, ive also had a teacher that believed like you that each person was in his own universe."

Thank you for demonstrating the value of testing. You continue to misunderstand me. I've no doubt you misunderstood your teacher. And your desire to flaunt your wilfull ignorance in public is disgusting.

then explain how the same thing can move at two different speeds in the same universe.

in relation to the observer it does appear that things are moving at different speeds, but light has only one speed, and that is not in realitive to anything. everything else is moving in relation to that speed. as long as you refuse to examine the theory yourself and go by what others tell you or what you have heard other say, it does not do any good to try to explain it.

in the time ive have dealt with teaching, i have discovered that there are two types of teachers. those that are political and those that know what they are talking about. the second are more than willing to learn new things, and are not the least bit afraid to admit they dont know something. they hate to say that they will not learn something. You have shown that you are a political type teacher and are not the least bit willing to admit you dont know or understand something.

when you are ready to really learn, why not do a search for the theory itself and read it yourself instead of accepting what others have said.

most of the time testing only proves that a student is good at taking test. its when he has to actually apply that knowledge that it shows if he knows it. many of the teachers that teach it, cant show that kind of knowledge, only the book knowledge that testing proves. oh, before you claim i must have failed a lot of test, no, i did ok. cant remember any that i actually failed, none at all in college. of course ive had a stroke since then and have slept quite a few times: i could have forgotten something. what your excuse.

Dear dehammer,

With all due respect, you are really talking utter nonsense. Your arguments remind of those of Mark McCutcheon ("The Final Theory" the so-called book which scientists do not want you to read!) who claims that all physicits have been misled for over four hundred years so that they misunderstand Newton's mechanics. I am not saying that it is imposible that an important point could have been missed even for four hundred years, but then the person who tries and point it out should at least argue from a sound scientific basis. In your case, as well as in Mark's case, you do not understand relativity theory (classical or special). It is clear that both of you have had incompetent physics teachers. It is a pity but it does happen, unfortunately.

i actually got the understanding from reading the theory, and from reading what researchers said, not what teachers said. as for my physics teacher, he was a good math teacher.

there is a big difference between me and the arthor your mentioning: i dont say that researchers have been mislead, only that some of the teachers are not teaching what the researchers are finding. I personally find it more likely when that if a researcher and a teacher have opposite views, the researcher would more likely have a better understanding of it. Ill follow what the researchers say, much more often than arm chair scientist. when i read that more than one researcher say its the perception of the viewer that shows the difference speed, while the reality is that the speed of light is not different at all, AND i have an armchair scientist who gives links to things that prove him wrong claiming they prove him right, saying that the of light is the 186000 miles per second in relation to someone that is moveing .8 light (or .5 or .75) AND at the same time is moving 186000 miles per second in relationship to someone not moving at all. then i'll listen to the researcher, and tell the armchair scientist that he has shown his ignorance once more.

Dear dehammer,

You just do not understand relativity, and you are not willing to try and understand it! Basically you are arguing that light speed in galaxies receding from us at about light speed should be nearly zero. REALLY!! If there is a civilization in such a galaxy, they will se US receding from them at about light speed. If the have a dehammer they will conclude that light speed here in our galaxy (and on earth) will be near zero.

dehammer asks:
"then explain how the same thing can move at two different speeds in the same universe."

I don't have to because no one has ever said that the same thing moves at two different speeds.

And I will not be goaded or cajoled into educating you on basic relativity theory. Get off your bottom and read a book on the subject.

Your repetition of a pathetically ignorant laZyman's perspective is disgusting.

dehammer wrote:
"i actually got the understanding from reading the theory"

No you didn't. You are mentally and technically incapable of reading the theory. But just to see if I owe you an apology explain this:

E^2 - (pc)^2 = m^2*C^4

dehammer wrote:
"and from reading what researchers said"

Nonsense. Absolute and total nonsense. What did you read? Provide title, author, and pubication. Any three will do.

You really do need to put down the shovel.

dehammer, you go wrong because you are making the (hidden) assumption of an absolute time. In nonrelativistic physics if two observers are moving relative to each other you have a transformation rule like:

x' = x - v t

t' = t


Here x is the position of an event that happens at time according to one observer. According to an observer that moves with velocity v in the x direction the x coordinate of the event is x' = x - v t if at time t = 0 he was at x = 0. t' and t are the same.

Accordng to special relativity, however:


x' = gamma (x - v t)

t' = gamma (t - v x/c^2)

where gamma = 1/(1-v^2/c^2)^?

In special relativity you assume constant c, which then necessarily implies the above Lorentz transformation rules implying that time isn't absolute. If you did have an absolute time then the speed of light would be observer dependent.

The two possibilites are not mutually consistent, they lead to different predictions for various experiments.

totally not what i said. i said the speed of light was the same no matter what the speed of the object that sent out the light.

nothing can go the speed of light, so there is no way a galazy can go that speed.

light is the yardstick that other speeds are measured against.

lets say that a galazy is moving at .99 light speed, in the opposite directions. we are moving at .01 light speed in our directions. that means that in relation to each other we see they other moving away at light speed. since we know that it cant be moving at light speed. we would then figure out that we are moving too. due to time dialation they would see us moving several times the speed of light, but knowing that is impossible (assuming they understand relativity) they would conclude that their time was being dialated.

lets us some real numbers here.

light speed is 186000 miles a second. a ship moving at .8 light speed is moving at 148800 miles per second. in relation to it, everything else appears (perception) to be moving at 148800 miles a second in the opposite direction. a beam of light would be moving at a real rate of 37200 miles per second in relation to the ship. due to time dialation someone in the ship would measure the speed of light as still being 186000 miles a second. this is because time dialated to 1/5 that of someone not moving in relation to light.

if this ship was approaching a planet, and they saw a ship comeing from the opposite directions, the light from that ship would still be reaching them at the speed of light. im afraid i dont remember the formula the researcher gave as to how to determine that appearant they would see the other ship approaching, but they would not see it being faster than light either.

that is called time dialation and that is what ive been saying, which ive been jumped on and dumped on for saying. the only thing is i did not have a formula for it.

i was told quote "time and space can not be seperated"

dehammer wrote:
"lets say that a galazy is moving at .99 light speed, in the opposite directions. we are moving at .01 light speed in our directions. that means that in relation to each other we see they other moving away at light speed."

No. No. No. Stop proudly parading your ignorance.

I notice you totally ignored my challenge to your claim that you'd read Einstein's paper so I'm going to shove it in your face a second time.

What is the derivation of this formula?

E^2 - (pc)^2 = m^2*C^4

And if you don't know try demonstrating integrity, ethics, and maturity by admitting that (A) you don't know and that (B) you've never read anything on relativity more serious than nursery school level.

Dan,
Please cool it with the insults or I'll have to edit your content.

Amaranth,
Moderator

i was not ignoring it, i just did not see it. I will admit that i am not that good with equations but that appears to have the dirivitive of e = mc^2. I have read up on it, but im an not that great on it. i can see where armchair scientist parate things they dont fully understand.

since your on the fact that you challanged me, what about my repeated challange to you about how the same photon can move at two different speeds simulataniously. you have done nothing about it, save insult me.


actually that is not quite true. you said in to two different people, light was still seen to be moving at light speed. the way you wrote it, that meant that the light was still moving away from each of them at 186000 miles a second, even when they were moving apart at 93000 miles a second. please explain that. i have stated repeatedly that light only has one speed. according to you, the light would have to be moving away from the one fartherst away at a speed of 279000 miles a second. which is possible only if he was the one that was moving. if he had never accelerated, then either the two of them had been moving at .5 light speed to begin with (which would mean the light beam had been traveling in the opposite direction at a speed of 279000 miles a second relative to them), or the second person was moving at .5 light speed and the light was only traveling .5 light speed faster than him.

the thing is, with time dialation, the light would still appear to be moving at light speed away from the second person.

dehammer wrote:

"i have stated repeatedly that light only has one speed. according to you, the light would have to be moving away from the one fartherst away at a speed of 279000 miles a second. which is possible only if he was the one that was moving."

I can now see what your problem is. The first sentence that I quoted from you above is incomplete. It should read that "lght has only one speed relative to any inertial reference frame". Inertial reference frames move relative to each other with different speeds. Nonetheless, RELATIVE TO ANY ONE OF THEM you will measure the same light speed c. You are making the mistake of adding the light speed relative to an observer moving relative to you as if this light speed can also be measured relative to your reference frame. This is not possible because both of you can only measure light speed to be equal to c within your respective inertial reference frames. I hope this helps.

no, that is what da has been telling me, and i keep repeating that light has only one speed. the thing is that it still appears to the faster traveler to be going away from him at light speed due to time dialation.

here is the thing though. if you can measure light going in any direction and it is close to the same speed, then your not moving much. if we measure the speed of light comeing from stars the difference in the speed is extreamly small (so small they cant be certain its not the measureing equipment). that is because our planet does not move at anywhere near a measureable fraction of light.

on the other hand if you in a space ship you should be able to detect some difference in the speed of light comeing from infront of you and that comeing from behind you, even with the time dialation. that would tell you what your speed is in relationship to light, and therefore to the universe.

dehammer, what you write is only the case if Lorentz invariance is broken. There are some physicists who have proposed similar experiments to test if Lorentz invariance is exactly valid or is broken at very high energy.

never knew its name. only knew what i read about it. If thats it, then i now have a name for what i read, IF i can remember it lol

Dehammer wrote:
"I will admit that i am not that good with equations but that appears to have the dirivitive of e = mc^2."

No: e^2 - (pc)^2 = m^2*C^4
is the formula that Einstein wrote. Had you read Einstein's publication you'd know that. e=mc^2 was not written by Einstein. It is a popularized simplification that is not valid in our universe.

Sorry Rose. I just hate it when people claim to have read things they clearly never read and haven't the integrity to admit it when clearly caught in their prevarication.

dehammer wrote:
"no, that is what da has been telling me, and i keep repeating that light has only one speed."

That is not what I've been telling you. It is what you have been MISUNDERSTANDING over and over and over and over again.

And your statement that "the thing is that it still appears to the faster traveler to be going away from him at light speed due to time dialation." is incorrect.

It was incorrect the first time you wrote it.
It is incorrect this time.
And it will remain incorrect in the future.

Read a book!

how would it not be correct. the time dialation that you are affected by is basically (simplistically) proportional to the percentage of light speed you are traveling.

You are NOT affected by time dilation because from your perspective you are NOT travelling at a percentage of light speed. It is only from another observer's perspective that you are travelling at a percentage of light speed. According to your perspective the other observer is travelling at a percentage of light speed.

from your point of view your not moving, but from the perspective of the speed of light, you are. period. that means that you are affected by time dilation. its not the perspective of speed that causes time to dilated, its your speed in relation to the entire universe, to space, to the photons moving past you. You will not see the time dilation, because its affecting you AND your senses. they dilation will not affect someone that has not accelerated.

I am starting to feel as if I am just wasting my time trying to point out the fallacies in your reasoning. You state: "its your speed in relation to the entire universe". How do you measure "your speed" relative to "the entire universe?". Which reference frame relates to the "entire universe?". You really do not understand the postulates on which Einstein based his special theory of relativity; do you?

simple. there are two ways.


1) stars do not acclerate unless there is some force that is working on them. unless that force is a majorly large one and/or close to it, any acceleration that affects them is going to occur over millions of years before its measureable. therefore any change in your speed relative to them is your speed.

2) light has only one speed. that is why we know that the distance stars are a certain distance from us. it is also why we can know that they are moving towards us, or away from us. if light has different speeds then we cant know the distance of anything, from a star to an aircraft. measureing the difference between the speed of light coming towards you from in front and from in back and you will easily have the speed you are traveling.

a third way for slower speeds is to check the redshift/blueshift of stars in front of you and behind. since relatively speaking, the stars are not moving very fast, nor are they accelerating very fast, then any change is due to you, not them.

any first year high school algerbra student should be able to figure that out.

i will not claim to have a perfect understanding of the equations, but the ones that are easiest to understand are not that hard.

do you really not understand math?

going over the sites i had used to learn about relativity, i can to a sudden realization.

when discussion speed and time dilation WE'RE ALL WRONG . its not speed that is involved, its acceleration that is the key. time dilation occurs during accleration so it does not matter what the other person speed is in relation ship to you.

a positive acceleration causes a negative time dilation (slowing of time, causing things away from you to appear to speed up) while a negative acceleration (commonly called deceleration) causes a positive dilation (the universe appears to slow down). it does not matter that from your point of reference (relative to you) the other person is moving away at .8 light speed), if he did not acclerate one way or the other he is not affected by time dilation. If you did, it will affect you.

Wow! you have come a long way. You are nearly there. Time dilation is an "illusion" when you look at the time within a reference moving at a constant speed relative to you. Similarly the person moving with a constant speed relative to you will "see" a time dilation within your reference frame. Finally you have grasped the fact that "real time dilation" only occurs within a reference frame when it accelerates (or decelerates). However, there is no "positive" and "negative" time dilation. A clock actually ticks slower when it is accelerated or decelerated; which is the same as the clock finding it in a larger gravitational field. Keep up the good work! We have not "all been wrong". You are finally approaching the truth. Congratulations!!!

And now we get back to your question.

Why does your 'moving` observer perceive
no change in C?

Because the length of his 'yardstick` changes.
Google 'Fitzgerald Lorentz contraction`.

My question to you:
How is your observer to perceive light moving away from him?

The "moving observer" perceives no change in light speed because according to him he is stationary relative to his inertial
reference frame. Therefore all observers will measure light speed as c relative to their own inertial reference frames; they are all in effect stationary. Corrections for "contractions" only need to be made when you are observing events occurring relative to an inertial reference frame moving relative to yourself; for example, the clock in a GPS sattellite clicks away at the same speed as it would if it were on earth; but as observed from earth it is not, and therefore a correction has to be made.

As I have said it is a type of an "illusion" but the illusiopn is "real"; for example, kinetic energy is a similar "illusion". When a mass m travels with you it has no kinetic energy within your reference frame; however, within a reference frame relative to which you are moving an observer will conclude that the mass has kinetic energy. Although this observation is an "illusion" as observed relative to the reference frame within which the mass m is stationary; it is a "real" factor within the reference frame relative to which the mass is moving.

Thus to state that: "the length of his 'yardstick` changes.", is not possible within his reference frame; it only seems to you as if it is the case from your reference frame. If you can teleport to his reference frame you will find that the 'yardstick' is not really any shorter, because now you also will be stationary relative to the 'yardstick'.

I hope this helps.

then explain why the person going on a high c fraction ship would return younger than his brother. its not an illusion. time does slow down for him, which means that from his perspective the universe speeds up. when he slows down at the end, the universe appears to slow down to normal, but it is really his time that is changing.

then explain why the person going on a high c fraction ship would return younger than his brother. its not an illusion. time does slow down for him, which means that from his perspective the universe speeds up. when he slows down at the end, the universe appears to slow down to normal, but it is really his time that is changing. [/QUOTE]

We have both posted. Mine is just before yours (see above).

Time only actually slows down within his reference frame when the spaceship accelerates and decelerates. In order to compare the ages of the two, the twin who left has to return to earth so that their ages can be compared relative to a single reference frame. The twin who has left had to accelerate to get away and to decelerate in order to return. Therefore, he will be the younger one.

If it were possible to leave with near light speed without acceleration, and the twins communicate by radio all the way, then both will conclude that they are ageing faster than the other twin. It is strange that this should be so; but, as mentioned above, both are experiencing an "illusion" within their respective reference frames of what is happening in their brother's reference frame. If, however, each twin corrects for the time he observes within the other twin's reference frame, as we are doing for the GPS satellites, they will find that they are actually ageing at exactly the same rate.

Hi JB:

I think I am still on topic to ask for your comparison of time passing. It seems to me we have time as an objective circumstance measured for dates and such by the rotation of the earth and then we time as an organic event. We get old independently of the earths rotation or the speed with which it orbits the earth. Possibly the drag of gravitation on our bodies provides some contribution as well.

When you quote an interpretation of Einstein and aging factors with acceleration by what means is our organic aging going to be restrained or accelerated as a result of moving through space? This has always been a curious suggestion to me.
This as an organic result needs something more than math to make it work. What can be shown to be going on in the body to age slower or faster?
jjw

Yes fascinating questions! According to special relativity (not considering gravitation), time is the fourth dimension. Thus it is an integral part of our four-dimensional universe and should thus manifest within every inertial reference frame at the same rate (the "proper rate"). In fact if this were not the case, estimations of the "age of the Universe" would have been futile. If time varied as a consquence of the speed you are moving at, the Universe would have different ages relative to different galaxies. Furthermore, the line widths of spectra will be different for materials moving relative to each other. The Universe would have been chaotic when being observed. Thus the contraction in time observed by an observer (considering himself to be stationary) within a reference frame moving relative to the observer is, as I have pointed out, a relativistic "illusion".

Thus a human being on another planet exactly like the earth but moving relative to earth with a high speed will still age at the same rate as he/she would have on earth.

From Einstein's general theory of relativity one finds that acceleration (which can be equated to gravity) causes actual time to slow down; for example at the event horizon of a black hole time supposedly stops completely. I sometimes speculate that the event horison is not a cloak of a singularity but rather the gateway to eternity. Thus if you can travel to end up near an event horison, you should actually age slower; i.e. all the time-related processes in you body should slow down. It might be a very boring and sad existence. Everything will be happenning in slow motion. On the other hand, if everything slows down , also you bodily functions and your thought rate, you might not notice the difference (except of course the massive gravitational force which you have to counteract not to fall "into" the black hole).

An interesting question: Can change occur (i.e. entropy change)within an Euclidean space-time. If it is truly Euclidean, the time axis will be perpendicular to the space axes so that any time-derivative will always be zero; nothing should then be able to change with time. I speculate that "our Universe" came into being when the fourth axis of an Euclidean (timeless; zero entropy) space-time became bent so that time and light started to manifest within three-dimensional space. Maybe our Universe is expanding because it is unbending to eventually again become a space-time with zero entropy.

Thank you JB.

It all sounds good but I get involved with details. Medical people tell us an adults person has a heart beat (pulse) of between 60 and 100 per minute. A trained athelete has a pulse between 40 and 60 per minute. Astronauts are in pretty good shape so let's assume an average of 60 perminute, the equivalent of 1 per second.

When things begin to slow down for our traveler at what point will the system be prone to fail. If we slow the ageing by 50 % does that mean a pulse of 30 per minute? A theory that touts the slowing of aging by acceleration or location must be quantified to provide the participants with some remaining life force to survive and continue. I am aware yhay I am baiting the question but it does seem to me that we are being in "very general relativity" with concepts like this one. Cheers.
jjw

The way I see it is that time is measured by change. There are now two possibilities: 1. that life functions do not slow down when time slows down and then your question is valid; 2. that everything slows down in concert so that we are not aware of the fact that we are living in slow motion relative to another reference frame.

It will be interesting to find out which is which. Point 2 might be correct. On the other hand when subjecting ourselves to a huge increase in gravity for a long time in order to slow time down, will probably kill us. This would indicate that point 1 could be correct. At least we know that when two persons are moving at a high speed relative to each other, the time rate each experiences IS THE SAME. Time dilation in this case is observed by each observer when he views the other observer. As I have said it is a kind of "illusion".

Have you considered the case where the twin who is leaving (on average) accelerates at a rate that is less than gravitaional acceleration on earth and comes back by decelerating at the same rate. The twin who has left will then have experienced an average effective gravitational field that is less than what the twin on earth has experienced. This will then imply that the twin that has left could be older than the twin who stayed behind. maybe this is not possible when taking into account that the twin travelling from earth first have to break free from earth's gravity. I have not yet made a full analysis; but raise this possibility because it is amusing.

Thanks again. I appreciate your response.

I think my point is that we are aware and will be aware of organic time. Taking Kepler literally we know that planets in orbit around the Sun following an elliptic path are sometimes traveling as much as 10 times the velocity as they are at other times. Extreme orbits such as that of Pluto should provide an example of this.
We do not generally feel any effects of this common acceleration that occurs at least once in every eliptical orbit. I suppose the speed is not significant in this example because it is not fast enough. That, I hope, will focus my issue. If the basic premise is correct then to me any acceleration should be meaning full. The highest speed is at the lesser axis so it is of short duration compared to the major axis. The Earths orbit is not extreme but the speed difference is still present.

So, "organically" I do get the feeling at times that the day is shorter or possibly longer, and that should qualify me for the DKV award.
jjw

Interesting viewpoint to ponder on. The effects that acceleration and deceleration has when the earth follows its elliptical orbit is probably negligible compared to the earth's own gravity. In fcat it must be so or else we should have picked it up on our bathroom scales.

Not quite:

The scale might tell you if you dropped a pound or two. It would not tell you if you lost an hour or two. Great fun.
jjw