"Time dilation why does gravity slow down the flow of time" - by Akash Peshin - URL review

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1. Einstein’s Dilemma

Einstein was heavily influenced by the works of two great physicists. First, there were the laws of motion discovered by his idol, Newton, and second, were the laws of electromagnetism laid down by Maxwell. The two theories, however, were contradictory. Maxwell postulated that the speed of an electromagnetic wave, such as light, is fixed — an exorbitant 186,000 miles per second. He claimed that this was a fundamental fact about the Universe.
There is 'nothing' wrong with this. There is nothing wrong to claim that the speed of light is a physical constant. The problem is that to calculate the speed of light two clocks are required which should run synchrone.
Whereas, Newton’s law implied that velocities are always relative. The speed of a car traveling at 40 mph is 40 mph relative to a stationary observer, but only 20 mph relative to a car traveling adjacent to it at 20 mph. Or, 60 mph to the same car whizzing by in the opposite direction. This concept of relative velocity is incompatible with Maxwell’s apparently fundamental fact when applied to the speed of light. This presented Einstein with a grievous dilemma.
The speed of a car and traveling at x mph, and an observer traveling also at x mph, in the same direction, seems to be standing still. The speed of a light signal and of an observer 'traveling' with the speed of light, in the same direction, seems to be standing still. In case of calculating the speed of a car also two clocks are required. All the clocks should run synchrone.
The contradiction led Einstein to make a mind-boggling yet also one of the most groundbreaking claims in the history of physics — a collocation of statements that is, of course, not surprising at all. To understand the contradiction and consequently why time slows down, consider another ingenious thought experiment, one of Einstein’s absolute best. Einstein imagined a man on a station platform, on both sides of whom two lightning bolts strike. The man, standing right in the middle of these two points, observes the resulting beams of light from both sides at the same time.
This can only happen at the same time if the two lightning bolts strike the ground simultaneous and the observer stands in the middle between these two markers.
However, things get peculiar when a fellow on a train views this scene while he moves past it at the speed of light.
Moving with the speed of light is a tricky speed for a human.
According to the laws of motion, light from the bolt closer to the train will reach the man earlier than the light from the bolt further from the train. The measurement of the speed of light made by both men will differ in their magnitude. But how is this possible when we recall that the speed of light, according to Maxwell, must be constant, regardless of the motion of an observer – a so-called “fundamental” fact of the Universe?
The point is that if the observer at the platform observes the two bolts strike the platform simultaneous than the obsever on the moving train will not observe the two bolts strike the platform simultaneous.
To compensate for this discrepancy, Einstein suggested that time itself slowed down such that the speed of light remained constant! Time for the man on the train passed slower relative to the time for the man on the platform. Einstein called this time dilation.
All the above is not clear.
There is absolute no reason to assume that time slows down. Read

Reflection 1 - Time dilation part 2

       t3                         c
          | .        /|         ./|
          |   .     / |       . / |
          |     .  /  |     .  /  |
          |       .   |   .   /   |
          |      /  . | .    /    |
       t2 |     /     a     /     |     /
          |    /    . | .  /      |    /
       t1 |   /   .   |   b       |   /
          |  /  .     | ./  .     |  /
          | / .       | /     .   | /
       t0 |/.       . |/        . |/
 x-1    ./x0    .    /x1         /x2
      . / |   .     /           /
    .  /  | .      /           /
  .   /   .       /           /
.    /  . |      /           /
    / .   |     /           /
   /.     |    /           /
  d    -t1|   /           /
Picture 1. (x,t) plane
Consider picture 1.
  • First we have a horizontal line which shows the platform at t0. At t0 two bolts strike the platform simultaneous. These two events are the points (x0,t0) and (x2,t0) also identified with the letter B and F. The observer O1 is at the point (x1,t0) in the midle between the points (x0,t0) and (x2,t0).
  • Secondly three are three vertical lines through the points (x0,t0), (x1,t0) and (x2,t0). Those are the points B, O and F at rest.
  • At t0 there are two bolts at the points (x0,t0) and (x2,t0). In the x,t plane those two events are shown by the line through the points (x0,t0) and (x2,t2) and the line through the points (x2,t0) and (x2,t3). Both these lines meet each other at point a, which is a point at the vertical through the point (x1,t0). This means that the observer O1 at the point(x1,t0) observers both bolts simultaneous.
  • Picture 1 also shows three tilted lines through the points B, O and F
    • The two tilted lines through the points F and B represent the front and the back of the train. The train moves to the right.
    • The tilted line through the point O represents the position of the moving observer O2 in time. This line crosses first the lightsignal orinating from the point F at point b. Secondly the lightsignal originating from the point B at point c, later.
In summary, the observer at the platform observes the two light signals simultaneous, but the moving observer (in the train) not. But, now comes an important issue, the moving observer, with a modification in this experiment can claim the same.
The most important physical issue is that the observer does not see the two events b and c simultaneous. The event c comes to late and also event B, when lightning hits the back of moving train. This event B should come earlier. This should be the point (x-1,t-1), the point d. The back of the train is then at point Y.
In Picture 1 you can see that the two lines (B to a) and (d to b) run parallel.
  • The line (B to a) shows the path of the light signal originating from the bolt at B at time t0.
  • The line (d to b) shows the path of the light signal originating from the bolt at Y at time t-1.
  • At the platform: at t-1 one bolt strikes at point Y. The light signal reaches the red . at t0. At that moment the second bolt strikes the front of the train at point F. At t1 the light signal reaches the red -

Reflection 2 - Time dilation part 2

In summary, there are two lightfalshes at the points B and F with observer O1 in between those two points at rest. Observer observes O1 these two lightsignals simultaneous, the moving observer O2 not.
What is important that the two lightflashes are emitted simultaneous. The question is how are they created.
The easiest is to start with a lightsignal at point O. This signal is emitted towards the left mirror and towards the right mirror, at the points B and F. This signal will be reflected by the two mirrors and observer O1 will observe the reflections simultaneous.
The observer O2 will not see those two signals simultaneous. (There is one exception).

However, and this is important, the moving observer O2, can claim, performing exactly the same experiment, that the observations will be the same.
In this experiment there are also two mirrors, one at the front and one back end of the (moving) train. That means, observer O2, standing in the middle of the train at point O, starts with a lightsignal, which will be emitted in both directions, towards the left and right mirror. This signal will be reflected by the two mirrors and observer O2 will observe the reflections simultaneous. That means Observer O2 can also claim that he is at rest.

The issue is, that if the same experiment is performed in all different directions and with different speeds, at the utmost only one observer can claim to be at rest.

When we use the word time it is important that it can mean two different things.
The first meaning is related to the age of the universe. This time we call universal time. What we mean that the universal time at any moment, throughout the universe at any place is the same. We can also call this moment: now. This is also the present moment. We can also define a past moment, which happend before the present moment and a future moment which will happen will happen later.
It is also important to define events. As such we can define: present events, past events and future events. An event can be a collision between two stars, between two cars and a erruption of a vulcan. All events that happen at the present moment, now, are happening simultaneous. The second meaning is time measured by a clock. The importance is that every clock is physical process, or mechanical device and based on the concept of an oscillator.
The major problem is that all clocks in general are different and that the time measured (duration) in universal time, between a fixed number of oscillations, is specific. However even for identical clocks the duration can be different.

But what is more important. The time

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Created: 4 August 2022

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