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martianxx

A measure of the speed of time.

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This time dilation is an appearance, not an actual occurrence. Time appears to slow.

 

Oh, I beg to differ! Time dilation is very real. Someone mentioned earlier that particles generated by cosmic rays live longer than they should. The reason that happens is because the particles are accelerated to near light speed, producing time dilation for them. If they were travelling slower, they would not survive to reach the ground before they decayed into other particles, but, because they experience time dilation, they do survive the trip from the upper atmosphere.

 

When scientists flew atomic clocks around the world and then compared the time on the atomic clocks with the time on the reference clock, the clocks that flew showed the change in the passage of time between the two reference frames. This change in times remains even after the different clocks are brought back into the same reference frame. Time dilation is measurable and real.

 

Due to relativistic effects of acceleration, some of our astronauts are some nanoseconds younger than they would have been if they had remained on Earth.

 

If things that accelerated experience some time change, than it would have to be in some sort of time bubble, where the time of the object is different then time elsewhere or around it.

 

The light is slowly beginning to dawn...

 

Exactly so, young grasshoppa!

 

There would have to be some sort of barrier or place of different times on each side.

 

You also have to believe that time is a real physical thing that can be effected by other objects and influences, like motion.

 

Yes, you would have to believe that!

 

 

If time is a thing, than what is it made of? Or what makes it a thing that can be changed just by motion.

 

How does gravity act on time? What do you mean?

 

Gravity warps space-time. Objects travelling through space-time follow this warped space. That includes light. One of the first proofs of Einstein's relativity was that light from Planet Mercury was slightly displaced from where calculations showed that Mercury actually was. Sun's gravity bends space-time enough that we can actually see light changing paths around it.

 

As you descend lower into a gravitational field, time slows, compared to objects higher in the gravitational field. In theory, time stops at the event horizon of a black hole; it would take an object an infinite amount of time to cross the event horizon from the perspective of an outside observer. From the perspective of the object falling, time is passing normally for him, but increasingly fast higher in the gravitational field. Acceleration is the same way; if you were to accelerate to near light velocity, head to the Andromeda Galaxy, the trip would appear to you to take just a few dozen years, but millions of years would pass on Earth. If you were to return to Earth, you would find that all those millions of years had passed on Earth, but maybe only 60 years had passed for you.

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Where did you get this reference that velocity is a barrier? Here is a definition of velocity in The Essential Dictionary of Science: speed of an object in a given direction, or how fast an object changes its position in a given direction.

 

No mention in this dictionary or others at hand that state that velocity can act as a barrier.

 

What is the barrier between these different times?

 

Perhaps you should not be as literal in interpreting EVERYTHING. I did not mean that velocity is a WALL made up of tangible atomic particles, in that sense. I don't think that I said something ridiculous or exaggerated, and I'm sure anyone would understand what I was talking about. I meant that it acts as something that separates reference frames (acts as a barrier), which are indeed in effect separate from each other. If you read the example well, you would understand that it is simply a literary device to facilitate my conveying of the idea. You understand what the "sound barrier" means without having to consult your dictionary, right? That's also not a solid wall in the general sense. If you find something wrong with this argument, please correct me in a proper manner. Don't make ridiculous attacks that have nothing to do with the topic.

 

 

What is all this? Where did you get this information?

 

"All this" is relativity. I assumed that you actually knew something about the topic into which you were posting. That is the most basic information learned by beginning students just starting to study quantum mechanics. I suggest you read a textbook on the matter, because while I mean no disrespect, if you do not know what I meant you have too little background in relativity (again I am not saying I do, I also have very little, it's just that you need it to argue).

 

Gravity warps space-time. Objects travelling through space-time follow this warped space. That includes light. One of the first proofs of Einstein's relativity was that light from Planet Mercury was slightly displaced from where calculations showed that Mercury actually was. Sun's gravity bends space-time enough that we can actually see light changing paths around it.

 

As you descend lower into a gravitational field, time slows, compared to objects higher in the gravitational field. In theory, time stops at the event horizon of a black hole; it would take an object an infinite amount of time to cross the event horizon from the perspective of an outside observer. From the perspective of the object falling, time is passing normally for him, but increasingly fast higher in the gravitational field. Acceleration is the same way; if you were to accelerate to near light velocity, head to the Andromeda Galaxy, the trip would appear to you to take just a few dozen years, but millions of years would pass on Earth. If you were to return to Earth, you would find that all those millions of years had passed on Earth, but maybe only 60 years had passed for you.

 

If you mean the procession of Mercury experiment by LeVerrier, that had nothing to do with warping by gravity. That was a simple illustration of the constancy of the speed of light (whether it was done correctly or not, that is what it was seen as proving, if anything). Where exactly are you getting your gravitational warping information from? Not to say that it is inaccurate (do not know enough about the topic), but something tells me you are not particularly into science. Your arguments seem jumbled up and a bit confusing.

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There is a reason it is called space-time. As for the effect of gravity and the "composition" of space-time, sorry I don't yet have enough background to answer that.

 

 

 

 

Find your answers in books, do research on the subject. If space-time has a composition then it has mass and location like all other things that are a compostion. If space-time was composed of something you could find out what it is made of in scientific reference books. Space-time is part of a theory and does not exist as a physical thing. If it did exist reference books would say so.

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If you mean the procession of Mercury experiment by LeVerrier, that had nothing to do with warping by gravity.

 

Gravity actually has a lot to do with Mercury's precession. LeVerrier was just one of many who tried to explain why Mercury's precession was more than known effects could explain.

 

That was a simple illustration of the constancy of the speed of light (whether it was done correctly or not, that is what it was seen as proving, if anything).

 

Actually, it gave us the Planet Vulcan. Again, his work was an attempt to explain why theory did not exactly predict Mercury's orbit.

 

Where exactly are you getting your gravitational warping information from?

 

Many books, some written by Einstein, that I have read over the last several decades.

 

Not to say that it is inaccurate (do not know enough about the topic), but something tells me you are not particularly into science. Your arguments seem jumbled up and a bit confusing.

 

Please accept my regrets for that. I am posting from work and from memory, it is Christmas Eve, and I am running around taking photos of beautiful women.

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Gravity actually has a lot to do with Mercury's precession. LeVerrier was just one of many who tried to explain why Mercury's precession was more than known effects could explain.

 

 

 

Actually, it gave us the Planet Vulcan. Again, his work was an attempt to explain why theory did not exactly predict Mercury's orbit.

 

 

 

women.

 

You do not say how it has to do with Mercury's precession.

 

I do not get the Vulcan reference, sorry, maybe I am slow today.

 

I still don't get what you are exactly (in terms of your background). I gathered that you are at least 40 (considering how you were reading Einstein's books for several decades), and you mentioned that you were

writing "from work", though you said you were not a scientist in a previous post if I am not mistaken. A journalist perhaps (not a stalker I hope)? Anyway I can't seem to glimpse the actual proof behind your statements, nor the reason you have for making statements (rather than arguments). Do you simply refer us to Einstein's books for the explanation of this phenomenon?

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Can either of you offer a citation and/or some math to support your points? All of this dizzing back and forth could be avoided if you would simply support your assertions with evidence.

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Perhaps you should not be as literal in interpreting EVERYTHING.

 

I am not going to assume what you mean by barrier

 

 

 

I meant that it acts as something that separates reference frames (acts as a barrier), which are indeed in effect separate from each other.

 

You are saying that velocity acts as something that separates reference frames. Where are you getting that definition of how velocity can act?

 

You may think I am being too picky on this, but what am I supposed to do? Just take your word for it without any scientific back up.

 

 

 

You understand what the "sound barrier" means without having to consult your dictionary, right?

 

 

I understand what a sound barrier is because there is a definition for it. Unlike your statement that velocity acts as a barrier. If more people would consult a dicitionary or reference book, to check what is being stated on this and other forms then many science topics would not end up in a discussion of everybody's interptitation or belief in what the real established facts are.

 

Consulting dictionaries and reference books keeps discussions from going off the rails.

 

 

Don't make ridiculous attacks that have nothing to do with the topic.

 

I just asked for a reference, there was no attack. I did stay on topic

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You do not say how it has to do with Mercury's precession.

 

Mercury orbits our sun along a certain path that is pulled out of shape by all the different masses in our solar system. However, Newtonian theory can only account for 93% of the total perturbation of Mercury's orbit. It turns out that Einstein's relativity accounts for the remainder.

 

From Encyclopaedia Britannica:

 

"Mercury's orbital motion has played an important role in the development and testing of theories of the nature of gravity because it is perturbed by the gravitational pull of the Sun and the other planets. The effect appears as a gyration, or precession, of Mercury's orbit around the Sun. This small motion, about 9.5' (0.16°) of arc per century, has been known for two centuries, and, in fact, all but about 7 percent of it—corresponding to 43" (0.012°) of arc—could be explained by the theory of gravity proposed by Isaac Newton. The discrepancy was too large to ignore, however, and explanations were offered, usually invoking as-yet-undiscovered planets within Mercury's orbit. In 1915 Albert Einstein showed that the treatment of gravity in his general theory of relativity could explain the small discrepancy. Thus, the precession of Mercury's orbit became an important observational verification of Einstein's theory."

 

Mercury in tests of relativity

 

I do not get the Vulcan reference, sorry, maybe I am slow today.

LeVerrier believed he had discovered a planet orbiting inside Mercury's orbit. He named that planet, "Vulcan," after the pagan god of volcanoes. The gravity from Vulcan might have partially accounted for Mercury's precession. Unfortunately, Vulcan does not actually exist.

 

I still don't get what you are exactly (in terms of your background).

 

I usually tell people that I am just a simple shoe-shine boy. I prefer to have my statements judged on their own merits, rather than my personal history.

 

 

I gathered that you are at least 40 (considering how you were reading Einstein's books for several decades), and you mentioned that you were

writing "from work", though you said you were not a scientist in a previous post if I am not mistaken. A journalist perhaps (not a stalker I hope)?

 

I'm a logistics analyst, practically the same as a shoe-shine boy for this discussion.

 

Anyway I can't seem to glimpse the actual proof behind your statements, nor the reason you have for making statements (rather than arguments). Do you simply refer us to Einstein's books for the explanation of this phenomenon?

 

Einstein's books would be a great reference. I would quote from them, but I don't have them handy (I'm at work, after all).

 

Exactly what kind of arguments would you like? Where should I begin? Do you accept that mass produces a curvature of space? Do you believe in gravity? You talk as if I am speaking of things no one has ever heard of.

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I am not going to assume what you mean by barrier

 

You are saying that velocity acts as something that separates reference frames. Where are you getting that definition of how velocity can act?

 

You may think I am being too picky on this, but what am I supposed to do? Just take your word for it without any scientific back up.

 

I understand what a sound barrier is because there is a definition for it. Unlike your statement that velocity acts as a barrier. If more people would consult a dicitionary or reference book, to check what is being stated on this and other forms then many science topics would not end up in a discussion of everybody's interptitation or belief in what the real established facts are.

 

Consulting dictionaries and reference books keeps discussions from going off the rails.

 

I just asked for a reference, there was no attack. I did stay on topic

 

ONE question. DO YOU know ANYTHING about special relativity (eg: what the breakdown of simultaneity is). PLEASE answer this question next time.

 

My information comes from the equations and generalities from special relativity. I am going to follow the advice of a poster and offer what I hope you could consider proof.

 

Lorentz transformations: if we have an inertial frame S' moving with velocity v in the positive x-direction relative to a frame S, the Lorentz transformations can be used to find the time and position at any point in space and time for both frames.

 

x’ = γ (x – vt)

x = γ (x’ + vt’)

 

t’ = γ (t – vx/c^2)

t = γ (t + vx/c^2)

 

These equations give the following equations:

 

x2’ – x1’ = γ [(x2 – x1) – v(t2 – t1)]

t2’ – t1’ = γ [-v/c^2 (x2 – x1) + (t2 – t1)]

 

x2 – x1 = γ [(x2’ – x1’) + v(t2 – t1)]

t2 – t1 = γ [v/c^2 (x2’ – x1’) + (t2’ – t1’)]

 

Basically these are time and space intervals. As you see, a time interval in S' is defined by a time AND space interval in S, and vice versa. The same is true for a space interval in S' and S.

 

If an event occurs at x1' = 0 and x2' = 1 in S' at the same time, using the Lorentz transformations will yield that this event occurs at DIFFERENT times for an observer in S.

For example, imagine a moving cart where a person is standing holding two light bulbs in each hand (like a letter T). He flashes the light bulbs at the same time. For him, the photons from each bulb start at the same time and reach the very center of his head at the same time. HOWEVER, for a person standing next to the moving platform, he sees photons traveling towards the head of the other person but he sees the cart MOVE towards the photon on the right. This means that to for that photon to reach the head of the moving person at the same time as the one on the left, the one on the left must have started SOONER than the one on the right. This is the breakdown of simultaneity. Also it's common (mainstream) knowledge.

Velocity, in this way, seems to separate reference frames. THAT is what I meant by "barrier".

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I made a long reply to this post already, but the forum software logged me out and lost my reply. I would just let it go, but there is one thing I want to mention...

 

These “real” dimensions, what form do they take? What makes them a real physical thing? If they are real like the rest of the things in this universe, then they would have an atomic structure, and mass.

 

Many real, physical objects in our universe do not have an atomic structure, and some of them don't have mass, either. Light only has a relativistic mass, one associated with its energy content (seen as frequency or wavelength). So, spatial dimensions do not have to possess an atomic structure or mass to be real.

 

You are saying that velocity acts as something that separates reference frames. Where are you getting that definition of how velocity can act?

 

I believe that is built into the definition of what a reference frame is. It sounds odd for you to challenge his statement about velocity separating reference frames while at the same time acknowledging that reference frames exist. What do you think a reference frame is?

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Exactly what kind of arguments would you like? Where should I begin? Do you accept that mass produces a curvature of space? Do you believe in gravity? You talk as if I am speaking of things no one has ever heard of.

 

No not at all.

At first I disagreed with your "acceleration accounts for time dilation argument", because normally it accounts for an infinitesimal fraction of it only, and the rest is caused specifically by relative velocity (which is part of acceleration too).

I suppose I should stick to that (for now) because, as I mentioned, I have yet to read enough about the phenomenon you mentioned. What I meant was that your arguments seemed a bit jumbled to me, that is the only reason it caught my attention: I noticed that you could not be a physicist because of that first argument, so I was unclear where your information came from. Gravitational warping is something I have yet to study, so I will refrain from arguing about it, just as long as I know where you are coming from/why exactly are you quoting Einstein.

As I said, I did not intend to argue about the second topic, merely clarifying what you are saying.

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No not at all.

At first I disagreed with your "acceleration accounts for time dilation argument", because normally it accounts for an infinitesimal fraction of it only, and the rest is caused specifically by relative velocity (which is part of acceleration too).

 

Where do you get that idea?

 

If time dilation is caused mostly by relative velocity, then why does it only affect one moving object and not the other? Those atomic clocks that orbited the Earth experienced time dilation; the clock that remained on Earth did not. The orbiting clocks and the Earth clock each had exactly the same relative velocity to each other, so why was one set affected but the other was not?

 

Are you familiar with the Twin Paradox? That is the hypothetical account of one member of a pair of twins who travels away from Earth and back at near light speed. On his return, he finds the other member of the pair has aged much more than he has. How could this be, that one experiences time dilation but the other does not, considering that each has exactly the same relative velocity to the other?

 

Before I shut down this computer (and go home to my own computer), I would like to post one more citation:

 

"Though Einstein based his theory of gravitation on deep theoretical principles, he and others proposed a number of experimental tests of the theory soon after its publication.

 

"The first prediction put to test was the apparent bending of light as it passes near a massive body. This effect was conclusively observed during the solar eclipse of 1919, when the Sun was silhouetted against the Hyades star cluster, for which the positi ons were well known.

 

"Sir Arthur Eddington stationed himself on an island off the western coast of Africa and sent another group of British scientists to Brazil. Their measurements of several of the stars in the cluster showed that the light from these stars was indeed bent as it grazed the Sun, by the exact amount of Einstein's predictions. Einstein became a celebrity overnight when the results were announced."

 

Putting Relativity to the Test

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Where do you get that idea?

 

If time dilation is caused mostly by relative velocity, then why does it only affect one moving object and not the other? Those atomic clocks that orbited the Earth experienced time dilation; the clock that remained on Earth did not. The orbiting clocks and the Earth clock each had exactly the same relative velocity to each other, so why was one set affected but the other was not?

 

Are you familiar with the Twin Paradox? That is the hypothetical account of one member of a pair of twins who travels away from Earth and back at near light speed. On his return, he finds the other member of the pair has aged much more than he has. How could this be, that one experiences time dilation but the other does not, considering that each has exactly the same relative velocity to the other?

 

First of all, *sign*.

Ok

The situation with orbiting objects: they have VELOCITY. Just because it is general relativity and not special relativity does not make velocity inapplicable.

I am familiar with the twin "paradox". I am also familiar with multiple explanations for it and multiple ways to understand it. It is in no way a paradox. Because I don't want to get into a very lengthy explanation while you can find one anywhere, including on the web, I will give you an example that is essentially the same.

 

Imagine two children born, one on Earth and one on a spaceship traveling TOWARDS Earth. Let's assume he travels at velocity v that causes time dilates time by 2: delta t = 2 delta t' ONLY for the observer on Earth. It would appear that we have a paradox: when he passes Earth, the traveler "thinks" he is older, while the Earth person "thinks" HE is older, right? WRONG. This is explained since while they are born at the same time by Earth standards, an application of the Lorentz transformations (which I have already posted and which have been posted here before I believe) will show that the traveler was born LATER in his OWN inertial frame. He still sees the other as aging twice more slowly, but because he was born later, he still ends up younger.

The actual twin paradox is explained because accelerating makes the traveling twin JUMP into a frame where the other is older, and when he goes back, he notices the other aging slowly, but still not slow enough to be younger than himself.

I suggest you read the explanation for the twin paradox if I am unclear, for I assure you that velocity (being in a different inertial frame) has EVERYTHING to do with time dilation.

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The situation with orbiting objects: they have VELOCITY. Just because it is general relativity and not special relativity does not make velocity inapplicable.

 

That's true, but velocity is not going to matter in either case.

 

I am familiar with the twin "paradox". I am also familiar with multiple explanations for it and multiple ways to understand it.

 

Whereas I am familiar with only one reason for that parable. Einstein created it as an illustration of relativistic effects. There should not be multiple explanations for it, because it only exists to serve one meaning; it is meant to illustrate Einstein's relativity.

 

It is in no way a paradox.

 

Sure it is; a pair of twins, born in approximately the same inertial frame, travel separate paths and see each other's time running slower than their own, but both cannot be younger than the other. That's a paradox.

 

Because I don't want to get into a very lengthy explanation while you can find one anywhere, including on the web, I will give you an example that is essentially the same.

 

Imagine two children born, one on Earth and one on a spaceship traveling TOWARDS Earth.

 

Is it not true that an observer on the ship would see Earth approaching at the same rate as an observer on Earth would see the ship approaching? It would seem so, for that is what we mean when we say they are approaching each other. If so, then the reference frames of the Earth and the ship are of the same values, but mirror images of each other. There is, therefore, nothing in their velocities to distinguish the person on Earth from the person on the ship.

 

Let's assume he travels at velocity v that causes time dilates time

 

IOW, we must assume what you are attempting to demonstrate, which is a logical fallacy. Velocity does not cause time dilation; acceleration does.

 

by 2: delta t = 2 delta t' ONLY for the observer on Earth.

 

Why would this formula apply only to the observer on Earth? The velocity of the traveler on the ship is identical in magnitude to the velocity of the person on Earth, only opposite in direction to an outside observer. They are mirror images of each other. Therefore, whatever time change one experiences, the other must also, in the same amount.

 

It would appear that we have a paradox: when he passes Earth, the traveler "thinks" he is older, while the Earth person "thinks" HE is older, right?

 

Each sees the other's clock as counting time more slowly than his own clock.

 

WRONG. This is explained since while they are born at the same time by Earth standards,

 

How would they know they were born at the same time? This is exactly the point Einstein made in his discussion of the meaning of simultaneity. Because Earth is approaching the ship at the same rate the ship is approaching Earth, an event that appears simultaneous on Earth will also appear simultaneous on the ship.

 

an application of the Lorentz transformations (which I have already posted and which have been posted here before I believe) will show that the traveler was born LATER in his OWN inertial frame.

 

The traveler was born later than who? You just claimed they were both born at the same time by Earth standards. Now, you say he was born later, but later by whose standard? The ship's? So, how does the ship's time in any way differ from Earth's time? Both Earth and the ship are approaching each other at the same rate. That's the key here; there is no difference between the two, so there is no difference in the time between the two.

 

This is the reason that velocity does not cause time dilation, but acceleration does. Both the Earth and the ship see each other approaching with the same velocity, but if the ship changes velocity, the effects are felt on the ship, not on Earth. No one on Earth is thrown to the side when the ship changes velocity, but they are on the ship if the ship changes velocity.

 

He still sees the other as aging twice more slowly, but because he was born later, he still ends up younger.

 

How do you know who was born later? What clock are you using?

 

The actual twin paradox is explained because accelerating makes the traveling twin JUMP into a frame where the other is older, and when he goes back, he notices the other aging slowly, but still not slow enough to be younger than himself.

 

Do you mean acceleration or velocity?

 

I suggest you read the explanation for the twin paradox if I am unclear, for I assure you that velocity (being in a different inertial frame) has EVERYTHING to do with time dilation.

 

During a period of constant velocity, both see each other's clocks running more slowly than their own. But, if the ship were to land on Earth instead of bypassing it, the ship would have to undergo a negative acceleration. During this negative acceleration, the traveler would see the clocks on Earth increase speed. By the time they land, the Earth clocks would have made up all the slow time they had, and the two clocks would be synchronized. No time dilation would be measured.

 

If, instead of traveling towards Earth, the traveler traveled away from Earth, a similar situation would happen. But, to return to Earth, the traveler must not only decelerate to a stop relative to Earth, but must also accelerate back towards Earth past that point. All during this time of deceleration/acceleration, the traveler would see the clocks on Earth appear to increase speed.

 

Time dilation observed while under constant velocity is an illusion; only the time change seen during acceleration is real.

 

University of New South Wales: The twin paradox: Is the symmetry of time dilation paradoxical?

 

DOE: TIME IS OF THE ESSENCE IN SPECIAL RELATIVITY

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There is a major problem with your reasoning: you do not seem to understand what an inertial reference frame is exactly. Are you familiar with the breakdown of simultaneity? If S' has velocity v relative to S, then two events separated by SPACE that occur SIMULTANEOUSLY in S' DO NOT occur simultaneously in S!! If you do not understand this statement then you can't possibly understand my argument, though this is a fundamental concept of special relativity that you should know to argue about it. As I mentioned before, doing the Lorentz transformations proves what I said, you should try it before criticizing what I said without knowing exactly what I meant.

Objects existing in different inertial reference frames might as well exist in different worlds. There is a single point in which we consider them synchronized: S' (0,0) and S (0,0). From there on, time intervals and space intervals in one frame are separated by space AND time intervals (each) in the other. In every IF, the truth seen (I don't mean actual seeing, but an instantaneous knowledge of an event in any point in space) is the actual truth for that IF. As I said before, the twin paradox IS NOT a paradox. Acceleration by itself hardly causes time dilation, it allows TRAVEL between reference frames and back to the point of origin. It does appear as if the effect is paradoxical, but in reality it does matter who is traveling at what velocity relative to LIGHT.

In any case: if two twins are born at the same time in an IF separated by space x != 0 (not = 0), then they CANNOT be born on the same time in a different IF. I really can't argue with you if you don't understand where my arguments are coming from and what they mean, because you will never accept them. So if you do not believe what I just said, take any textbook/website pertaining to special relativity, maybe type in "breakdown of simultaneity", because in all honesty, you do not know enough about the topic as is. Basically you are asking me to "prove" that an integral is the area under the curve of a function without you knowing what a function/slope is.

 

Basically, if what you are saying is true and time dilation depends on acceleration, we could have the twins start out by traveling in frame S' at velocity v relative to Earth, then have one "decelerate" into the Earth's frame, wait for x years and then accelerate back into his twin's frame. If time dilation was caused by the acceleration, the twin who lived x years in Earth's frame should now be YOUNGER, whereas that is NOT the case.

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Whereas I am familiar with only one reason for that parable. Einstein created it as an illustration of relativistic effects. There should not be multiple explanations for it, because it only exists to serve one meaning; it is meant to illustrate Einstein's relativity.

 

No, there are plenty of physics examples that have multiple explanations, e.g. conservation of momentum vs. conservation of energy.

 

IOW, we must assume what you are attempting to demonstrate, which is a logical fallacy. Velocity does not cause time dilation; acceleration does.

 

No. The equation for gamma contains only v as a variable. The amount of dilation depends on v and the accumulated time difference depends on how long you are at that speed. Not the acceleration.

 

This is the reason that velocity does not cause time dilation, but acceleration does. Both the Earth and the ship see each other approaching with the same velocity, but if the ship changes velocity, the effects are felt on the ship, not on Earth. No one on Earth is thrown to the side when the ship changes velocity, but they are on the ship if the ship changes velocity.

 

That's because acceleration is not relative, so anyone accelerating knows they are changing reference frames.

 

 

Time dilation observed while under constant velocity is an illusion; only the time change seen during acceleration is real.

 

No. There is a problem that you can't compare clocks side-by-side unless there is an acceleration, but "illusion" is not a proper decription.

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There is a major problem with your reasoning
Who are you addressing? You were arguing with Eric5, but your last sentence appears to be directed at me. I hope you are not confusing us.

 

you do not seem to understand what an inertial reference frame is exactly. Are you familiar with the breakdown of simultaneity?
Assuming you are addressing me, I am familiar with these things. For example, Einstein described a thought experiment in which 2 bolts of lightning struck a railroad track, 1 bolt at either end. He suggested that the 2 bolts struck at the same time, then asked what that meant. He then modified the setup by adding a moving rail car to the track, so it would be moving in the direction of one bolt, but away from the other, and he asked if the twin strike would appear simultaneous to both an observer standing alongside the railway track, and an observer on the moving rail car. They don't, because light must travel a different set of distances for the moving observer than for the stationary observer. This is also a use of inertial reference frames.

 

Objects existing in different inertial reference frames might as well exist in different worlds.
See, all of your preceding paragraph, down to this sentence, appears to be in response to Eric5, not to me.

 

As I said before, the twin paradox IS NOT a paradox.
That is like claiming that a riddle is not a riddle because you understand the answer.

 

Acceleration by itself hardly causes time dilation, it allows TRAVEL between reference frames and back to the point of origin. It does appear as if the effect is paradoxical, but in reality it does matter who is traveling at what velocity relative to LIGHT.
Both the observer on Earth and the observer on the spaceship are traveling at a velocity relative to light, and we can only arbitrarily claim that one observer or the other is in a stationary reference frame.

 

But, suppose you did not have an observer on Earth, but, rather, on another spaceship. So, you have Alice on Spaceship A and Bob on Spaceship B. Spaceship A is in the volume of space that used to be occupied by Earth, before Earth was destroyed to make way for a hyperspace expressway. Spaceship B is arriving from Pluto. So, the 2 spaceships see the distance between them shrinking. Each sees the other spaceship approaching at the same velocity. The Lorentz transform applies to both spaceships, so both spaceships see time dilation taking place on the other spaceship, IOW, both sees the other as younger than himself, which is a paradox.

 

As best I understand this situation, whichever observer then accelerates away from the other, he or she will see the other observer appear to age.

 

In any case: if two twins are born at the same time in an IF separated by space x != 0 (not = 0), then they CANNOT be born on the same time in a different IF.
I was going to make that complaint when you proposed that we "Imagine two children born, one on Earth and one on a spaceship traveling TOWARDS Earth." After all, what is the point of that? It isn't the Twin Paradox, because you can't say the two are born at the same time.

 

I really can't argue with you if you don't understand where my arguments are coming from and what they mean, because you will never accept them. So if you do not believe what I just said, take any textbook/website pertaining to special relativity, maybe type in "breakdown of simultaneity", because in all honesty, you do not know enough about the topic as is.
This, again, looks like it should be directed at Eric5, because I actually linked to 2 websites on Relativity in my previous post. Both of them point out that acceleration is what makes time dilation work in the Twin Paradox.

 

Basically, if what you are saying is true and time dilation depends on acceleration, we could have the twins start out by traveling in frame S' at velocity v relative to Earth, then have one "decelerate" into the Earth's frame, wait for x years and then accelerate back into his twin's frame. If time dilation was caused by the acceleration, the twin who lived x years in Earth's frame should now be YOUNGER, whereas that is NOT the case.

 

OK, let's suppose that happens. As I see it, the twins are traveling together, so they consider their reference frame as stationary. Twin A rockets back to Earth, meaning he accelerates away from Twin B. On return to Earth, Twin A finds that he is younger than Earth. While on Earth, Twin A is now aging at Earth time, but Twin B is not. After some time, Twin A takes off, again, and follows along behind Twin B. While accelerating, Twin A will observe Twin B aging faster, but not as much as Twin A aged while on Earth. (I think I worked that out correctly, though I skipped the deceleration when Twin A arrived at Earth).

 

I found an interesting blurb on a Website:

 

"The equation for the time at Earth versus the time in the spaceship for a round trip is given by

 

t = 4 c sinh(gτ/4c)/g

 

"where c is the speed of light, g is the acceleration, and τ is the time for the passengers on the spacecraft, which is called the proper time of the spacecraft. These two times are given in the live figure to the left as functions of destination distance. For trips much longer than τ = 4c/g, the elapsed time on Earth increases exponentially with elapsed time on the spacecraft."

 

Astrophysics Spectator: Travel to the Stars

 

An observer in a closed room cannot distinguish between the force of gravity and force applied due to acceleration. So, time dilation for someone in an accelerating room would be the same as if he were in a gravitational field. It is my understanding that the equation for time dilation due to velocity and the equation for time dilation due to gravity only need differ by changing out velocity with gravity.

 

I admit that I may be mistaken at some point, as I have never been trained in Relativity apart from my own reading, but I believe I have the gist of it correct.

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This, again, looks like it should be directed at Eric5, because I actually linked to 2 websites on Relativity in my previous post. Both of them point out that acceleration is what makes time dilation work in the Twin Paradox.

 

Dilation appears because of relative motion, but it's acceleration that moves one individual into a different inertial frame. Dilation "works," i.e. it is present, in the absence of acceleration.

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Who are you addressing? You were arguing with Eric5, but your last sentence appears to be directed at me. I hope you are not confusing us.

 

Assuming you are addressing me

This, again, looks like it should be directed at Eric5, because I actually linked to 2 websites on Relativity in my previous post. Both of them point out that acceleration is what makes time dilation work in the Twin Paradox.

 

 

I admit that I may be mistaken at some point, as I have never been trained in Relativity apart from my own reading, but I believe I have the gist of it correct.

 

My comment was a direct response to yours.

 

The reason I talked about breakdown of simultaneity is because you asked how the twins could be born at different times if one IF if they were born at the same time in another. THAT is the intrinsic property of an IF, and from that I assumed you did not know much about special relativity.

 

The post before mine very nicely summarizes everything there is to say. Proving it to you is impossible, simply because you can always come back with a "the sky is blue because bananas are yellow" type of argument: as I mentioned before, all you need to do is read about a few hours' worth of text from a textbook or a good website to understand what we are talking about. Right now, that's exactly what it is: a case of you not being exactly familiar with the info, nor did you address my arguments (which were proofs) in any way.

 

Again: time dilation (NOT imaginary time dilation) IS a property of RELATIVE VELOCITY. At this point it is not really an argument since i see that you are mistaken, so please do read some information on it if you care to know more (I can't give the proof here, too much to write all the equations). If you don't believe me, do notice that the previous poster is in agreement with me, if that does my argument any good in your eyes.

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ONE question. DO YOU know ANYTHING about special relativity (eg: what the breakdown of simultaneity is). PLEASE answer this question next time.

 

My information comes from the equations and generalities from special relativity. I am going to follow the advice of a poster and offer what I hope you could consider proof.

 

Lorentz transformations: if we have an inertial frame S' moving with velocity v in the positive x-direction relative to a frame S, the Lorentz transformations can be used to find the time and position at any point in space and time for both frames.

 

x’ = γ (x – vt)

x = γ (x’ + vt’)

 

t’ = γ (t – vx/c^2)

t = γ (t + vx/c^2)

 

These equations give the following equations:

 

x2’ – x1’ = γ [(x2 – x1) – v(t2 – t1)]

t2’ – t1’ = γ [-v/c^2 (x2 – x1) + (t2 – t1)]

 

x2 – x1 = γ [(x2’ – x1’) + v(t2 – t1)]

t2 – t1 = γ [v/c^2 (x2’ – x1’) + (t2’ – t1’)]

 

Basically these are time and space intervals. As you see, a time interval in S' is defined by a time AND space interval in S, and vice versa. The same is true for a space interval in S' and S.

 

If an event occurs at x1' = 0 and x2' = 1 in S' at the same time, using the Lorentz transformations will yield that this event occurs at DIFFERENT times for an observer in S.

For example, imagine a moving cart where a person is standing holding two light bulbs in each hand (like a letter T). He flashes the light bulbs at the same time. For him, the photons from each bulb start at the same time and reach the very center of his head at the same time. HOWEVER, for a person standing next to the moving platform, he sees photons traveling towards the head of the other person but he sees the cart MOVE towards the photon on the right. This means that to for that photon to reach the head of the moving person at the same time as the one on the left, the one on the left must have started SOONER than the one on the right. This is the breakdown of simultaneity. Also it's common (mainstream) knowledge.

Velocity, in this way, seems to separate reference frames. THAT is what I meant by "barrier".

 

 

 

Thanks for the effort to explain this concept to me. i just want to be clear on something before i can respond. in your example with the moving cart, which way is the cart moving?

 

I made a long reply to this post already, but the forum software logged me out and lost my reply. I would just let it go, but there is one thing I want to mention...

 

 

 

Many real, physical objects in our universe do not have an atomic structure, and some of them don't have mass, either. Light only has a relativistic mass, one associated with its energy content (seen as frequency or wavelength). So, spatial dimensions do not have to possess an atomic structure or mass to be real.

 

Those who say spatial dimensions are real wil not say in what way they are real. Besides, if spatial dimensions were real there would be a definition that stated this. There are none to my knowledge. Dimensions are a concept not real physical things.

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Thanks for the effort to explain this concept to me. i just want to be clear on something before i can respond. in your example with the moving cart, which way is the cart moving?

 

To the right: positive x-direction.

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i am really interested in yours post of this.... but i think that there is sort of uncertainty in the measure of "speed" of time..u cannot calc the speed of time by already taking speed of some object (which is some m per SEC.....and that wrong speed of the obj itself!!!!)

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I have recently been reading a book called "The fabric of the cosmos" and it states that there is a relationship between speed in time and speed in space. It says that when stationary a body is moving only through time and not through space, seems obvious. Yet when the body begins to move time slows down slightly. It says that when travelling at the speed of light time stops. I was annoyed by the concept of "speed of time" how do we calculate a speed of time. I found out about a group of scientist that took a highly sensitive clock from London Heathrow to Sydney Australia in a Boeing 747. the time taken by the very accurate clock was less than the amount of time that other clocks said. I am not sure if there is already a way to calculate the speed of time, but just in case there isnt i have attempted to make one.

 

I started of by thinking that the speed of time when the body is stationary was 0. And the speed of time when travelling at 186000 miles per second was 1.

 

i then asked my self how fast you would have to travel to have a speed of time of 0.5 this is obvioulsy 186000/2 = 96000 miles per second.

 

I then said that if traveling at 186000 miles per second the speed of time is 1 then it would have to be 186000/186000 = 1 i then took the idea of the speed of light being constant. I worked out that logically the speed of time should be equal to the speed in space divided by the speed of light.

 

If you do this you get a very small number supposing you do it with a possible speed and you get a number that doesnt really mean much. So i developed the idea of the speed of time being how long a second when stationary is when moving at a given speed. The speed in space/speed of light gives the difference between the time of a second while stationary and the time of a second while traveling at the orignal speed. So i said that 1-speed in space/speed of light = time of 1 second while moving. As you can see, when traveling slowly the time changes so little that no one would pick it up, only this amazing clock that went to australia.

 

I will give an example the clock that went to australia if the time taken on a normal clock was 24hrs and the plane averaged 605 mph then:

 

First we must express 605 mph in miles per second. We have to do the calculation,

 

605/60/60 = 0.168 3sf

 

we put this speed into the equation speed of time = v/c to get,

 

0.168/186000 = 9.03x10^-7

= 0.000000903

 

This is the difference in the speed of time so we have to take this from 1.

 

1 - 0.000000903 = 0.999999097

 

this is the real time of one second while flying at 605 mph. Assuming it takes 24hrs to get from london to sydney the real time taken = 24x60x60 = 86400.

 

then it is 0.999999097 x 86400 = 86399.92seconds. This in hours is 86399.92/60/60 = 23.99998 so you end up losing 0.8seconds of time.

 

If any of this seems incorrect or has already to your knowlaged been discovered please tell me, i would really like to hear from you.

 

we probably live in a universe with at least two entities of time. 1. pre str and gtr where time was homogenous in the absence of matter and minkowki. and 2. since the presence of mass in the universe str and gtr and minkowski calling time a dimension. From my point of view time is homogenous. Temporal time - clock time is elastic and certainly not a dimension. i.e. One side of a box dimension called width cannot be elastic otherwise we would never know what its true shape is!! A dimension exists or it does not. I hate to live in a universe with elastic dimensions - omg. Thanks to Minkowski thats exactly where we are.

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Please confine your nonstandard view to your own threads. People asking questions in "physics" want the mainstream answer, not a thread hijack.

 

Actually farsight has a point. In 1905, Einstein was careful to define time operationaly, and not as a property of nature. Later he created the mathematical abstraction known as spacetime, which was then taken to have a physical meaning, but if you look at Einstein's first writings, he was concerned with the concept of time because we can only measure time indirectly: what we actually measure is the change of something in space - be it the position of a pendulum or the state of a subatomic particle. Hence, physically and operationally speaking, time is strictly the measurement of a change of matter/energy in space. If a clock reads less elapsed time, it must mean that it underwent less cycles when compared to the reading of another clock.

 

So of course the "speed of time" is just a mathematical abstraction and can only have a concrete physical meaning if considered to be "the speed of the rate of change of a cyclic change of state", since time is "the speed of cyclic change of state". Thinking about it... the speed of time sounds like an acceleration!

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Farsight is a well-know crackpot. Or was, in terms of this site, since he was eventually banned for continually hijacking threads to discuss his peculiar interpretation of phyics, making this necromantic objection moot in several ways.

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