Is Time Merely A Construct Of The Imagination ?

[A-wal]

That I'm not concerned about td and lc, since the transformations cover those.

But my point was that you could use time dilation alone or length contraction alone to keep the speed of light constant...

When you compare yourself to an object that's in motion relative to you you need to apply length contraction and time dilation to account for the consistency of the speed of light. You could in principle use only time dilation or only length contraction to maintain a constant velocity for light but velocity is a measure of distance over time. Both are equally subject to the change if the inertial frame of the observer changes.

...and the difference in proper time doesn't change because length contraction decreases the distance traveled and so decreases the proper time taken to make the journey by the same amount that time dilation decreases the journey time.

 

The example Einstein used was the simple twin paradox, with A static and B moving.

It's not symmetrical.

Examine the gamma factor and notice it's a function of speed v/c, not acceleration.

The clock hypothesis states that the tick rate of a clock when measured in an inertial frame depends only upon its velocity relative to that frame, and is independent of its acceleration or higher derivatives. The experiment of Bailey et al. referenced above stored muons in a magnetic storage ring and measured their lifetime. While being stored in the ring they were subject to a proper acceleration of approximately 10¹⁸ g (1 g = 9.8 m/s²). The observed agreement between the lifetime of the stored muons with that of muons with the same energy moving inertially confirms the clock hypothesis for accelerations of that magnitude.

      Sherwin, “Some Recent Experimental Tests of the 'Clock Paradox'”, Phys. Rev. 129 no. 1            (1960), pg 17.

 

Aging is permanent since there is no speed by which a clock gains time.

No, you've got this all wrong. Velocity is entirely relative, that's the basic principle that the whole of special and general relativity are based on. If objectA is moving away from objectB at .5c then objectB is moving away from objectA at .5c! The stationary object is an arbitrary choice.

 

From the perspective of their worldlines it makes this shape, V and if you view the - horizontal axis as motion through time and the I vertical axis as motion through space the you can put either worldline on the horizontal axis and see that from their inertial frame the other worldline is moving though space and moving slower than themselves through time. Both are moving through spacetime at the speed of light.

 

For the two observers to meet back up in the same inertial frame as each other = at least one has to accelerate, at least of has to follow a curved worldline.

 

The point of the light clock is to show "moving in time" is just a figure of speech, since  all elements, observer, clock, and light are moving in space. You do make a good point with the line. The path of an object as shown in any graphic is a history of its positions for a duration of time, and is not a physically observable thing. We can't see orbits, trajectories, etc.

It's a physically observable thing just as much as motion through space is. Motion is a change in relative position over time and every objects combined motion through time and space is always the speed of light.

 

How do they communicate?

Draw a square 1 unit per side, vertical axis t, horizontal axis x.

Coordinates (x,t): for A (0,0), for B (1,0). They are static, and after 1 time unit,

for A (0,1), for B (1,1). A sends a light signal to B at t=0. It arrives at B(1,0) at t=1.

B is not there!

What? If they're at rest relative to each other then of course B is there. If you're saying that because they're moving through space the receiving observer will have moved when the signal arrives, that's not how it works at all. For starters signal expand outwards in every direction and more importantly, if they're at rest relative to each other then the receiver wont have moved, regardless of their velocity relative to any other object.

Edited October 13, 2016 by A-wal

[sluggo]

A-wal #35

But my point was that you could use time dilation alone or length contraction alone to keep the speed of light constant...

 

1. I don't keep the propagation speed of light constant and independent, since that is the natural behavior of light, with or without observers.

2. The measured speed of light is constant due to the motion induced effects, td and lc, resulting from statement 1.

Time dilation alone does not resolve the MM experiment, and requires length contraction.

Motion is a change in relative position over time and every objects combined motion through time and space is always the speed of light.

 

You seem to have a problem reading, when describing examples different from the one I post.
The drawing should make it clear. Based on your statement above A and
B, 1 spatial unit apart, move 1 sec in time, from t=0 to t=1. A emits a light signal (arrow) at t=0, which arrives at x=1 at t=1..The arrow and B are not there simultaneously!

For starters signal expand outwards in every direction

 

EM radiation is directed to a target. If it spread, other targets in the vicinity would register a 'hit'.

 

If you haven't read the 1905 paper you should. You have ideas that are not in accord with SR.

 

 

 

[A-wal]

1. I don't keep the propagation speed of light constant and independent, since that is the natural behavior of light, with or without observers.

The propagation of anything is entirely dependent on other observers because motion can only exist relative to other objects.

 

2. The measured speed of light is constant due to the motion induced effects, td and lc, resulting from statement 1.

Time dilation alone does not resolve the MM experiment, and requires length contraction.

Again you're completely missing the point. You can maintain a constant velocity of light using only tome dilation or using only length contraction. The proper time required to make the journey is shortened by length contraction in exactly the same way that it's shortened by time dilation, which makes the statement: "Aging due to time dilation is permanent, length contraction is not." entirely false and shows a complete lack of even the most basic level of understanding.

 

You seem to have a problem reading, when describing examples different from the one I post.

The drawing should make it clear. Based on your statement above A and

B, 1 spatial unit apart, move 1 sec in time, from t=0 to t=1. A emits a light signal (arrow) at t=0, which arrives at x=1 at t=1..The arrow and B are not there simultaneously!

Forget the graph and explain why you think motion through time is any different than motion through space given that time dilation affects motion through time in the same way that length contraction affects motion through space, both causing the same reduction in the amount of proper time required to make a journey from the perspective of an observer in a different inertial frame and keeping the speed of light and each observer's motion through spacetime constant at c.

 

EM radiation is directed to a target. If it spread, other targets in the vicinity would register a 'hit'.

How do they communicate?

 

Draw a square 1 unit per side, vertical axis t, horizontal axis x.

Coordinates (x,t): for A (0,0), for B (1,0). They are static, and after 1 time unit,

for A (0,1), for B (1,1). A sends a light signal to B at t=0. It arrives at B(1,0) at t=1.

B is not there!

Explain exactly how think two observers that are at rest relative to each other could possibly 'not be there' to receive signals sent to each other.

 

If you haven't read the 1905 paper you should.

I already know what SR describes. I realise that you're trying to save face but if you think that the motion between two inertial observers is in any way not symmetric then you need to start from the very beginning and read Galilean relativity.

 

You have ideas that are not in accord with SR.

No I don't. I have ideas that aren't in accordance with GR. If you think I've contradicted SR then it's because you don't understand SR.

[A-wal]

Sorry if I was a little harsh in my last post Sluggo, it's just frustrating.

 

The point is that time is no different than space, we simply perceive time to be progressive because we have a three and a half dimensional perspective of the universe. We can see in both directions of three dimensions so we perceive everything alone those axes as existing simultaneously but at any point in time we can only see in one direction of it, the past, so it creates a sense of continuous progression.

 

It means that you can see the relationships between objects in relative motion by using the worldline concept from general relativity. Anyone with a half decent technical understanding of trigonometry should be able to come up equivalent equations to SR's, if not they'll be more accurate because they'll describe the underlying cause in its simplest form.

 

What this means is that SR can accurately model gravity. GR doesn't work because it views freefall as an inertial state but describes it as a curved path in spacetime, a curved path is acceleration. You feel g-force in freefall, it's called tidal force. Both are caused by a difference in force over different parts of the same object, or a different strength in the force affecting atoms that are electromagnetically bound to each other to be precise.

 

There's no physical difference between an object following a straight path through curved spacetime and the object following a curved path through flat spacetime in the same way that there's no difference between object A moving away from object B and object B moving away from object A, what's actually happening is that the object is following a curved path through spacetime.

 

General relativity leads to contradictory frames of reference and breaks down in many ways when you take gravity to the extreme (black holes). http://www.scienceforums.com/topic/27224-can-you-answer-these-black-hole-questions/ It allows the dimensions to overlap each other at the event horizon. No amount of acceleration (gravitational or otherwise) can curve a wordline past 90 degrees to cause that overlap because that would require infinite acceleration.

 

Approaching an event horizon works in exactly the same way as approaching a Rindler horizon, it can't be reached and the acceleration addition formula is identical to the velocity addition formula that prevent any object from reaching the speed of light relative to any other object, something that would have happened if an object were able to reach an event/Rindler horizon.

 

I'll start a new topic for this tomorrow.

[sluggo]

I'm not interested in a detailed study of GR. SR is more interesting and simpler.

FYI free fall is inertial for uniform fields. Earth only approximates that.

Maybe xyz will return, you can argue with him.

[A-wal]

I'm not interested in a detailed study of GR. SR is more interesting and simpler.

Then I suggest you start with Galilean relativity because it explains the most basic aspect of relativity, that all inertial motion is relative ans symmetric. There's no point in trying to learn special relativity until you've grasp the basic concept that it's built on first. Then move on to special relativity and start with how coordinate time is not proper time and how proper time relates to time dilation and length contraction.

 

FYI free fall is inertial for uniform fields. Earth only approximates that.

Of course Earth only approximates uniform gravitational acceleration. Any extended object will always be experience gravitational forces that are stronger closer to the source of the gravitation and weaker further from it. Freefall is not inertial! For a start there's no such think as a uniform gravitational field and even if there were it would be equivalent to uniform acceleration of of body, NOT inertial motion! Acceleration is equivalent to acceleration, it's not difficult. No test can be performed that can distinguish between gravitational acceleration and the equivalent non uniform acceleration free from gravitational forces.

 

Maybe xyz will return, you can argue with him.

Maybe you should keep your mouth shut rather than embarrassing yourself by pretending to understand things that you obviously have no grasp of. Start with basic relativity and try to work your way up.

[sluggo]

Maybe you should look in the mirror, and take your own advice.

You won't be successful criticizing people you don't know, especially about things you think you understand.

It makes you seem foolish. I am not embarrassed, but you seem to be, and respond in anger.

[A-wal]

Maybe you should look in the mirror, and take your own advice.

Takes one to know one, that a real mature response.

 

You won't be successful criticizing people you don't know, especially about things you think you understand.

You're in no position to judge anybodies level of understanding on this subject!

 

It makes you seem foolish. I am not embarrassed, but you seem to be, and respond in anger.

I'm not you are, this is like debating with a toddler. I responded in frustration to some dude pretending to know better when they don't even know the basic concepts like proper time and relative motion being symmetric (the whole underlying concept behind all of relativity!). It's very annoying.

[sluggo]

#40

Freefall is not inertial! For a start there's no such think as a uniform gravitational field and even if there were it would be equivalent to uniform acceleration of of body, NOT inertial motion!

 

Why do anauts experience weightlessness while accelerating in orbit, or flying a parabolic trajectory in a plane?

[A-wal]

Because free-fall is equivalent to uniform acceleration. At least if would be if it weren't tidal force which is negligible anyway except in extreme gravity. On the Earth we're accelerated downwards almost uniformly so we don't feel that but we're electromagnetically accelerated upwards by the Earth and that we do feel because it's not uniform, it's concentrated on our points of contact with the ground.