Is my understanding of the concept on time dilation accurate?

Question

Warning, I have no background in Physics. I'm trying to understand time dilation in special relativity.

I have found quite similar questions here and here but I would like to elaborate more and frame it on how I understood the concept and rephrase my thoughts in multiple ways to be better understood.

When something travels at the speed of light in one direction it can no longer have velocity in any other direction, otherwise it would exceed the speed of light. Say if something travels north at the speed of light, it cannot have any velocity towards east or west without exceeding the speed of light.

Let's assume I'm traveling at the speed of light (and still human and alive) towards the direction I'm facing. That means I can no longer move left or right. The same goes for all the atoms that I am made of including subatomic particles. All of my atoms cannot move in any other direction rendering everything effectively "frozen". My metabolic processes would stop and so is my wrist watch. This would effectively stop my time as time is measure of change (locally) and there can't be any changes since all of my atoms have stopped moving in any other direction.

This is how I understood why time seemingly stops when you travel at the speed of light.

And if I am not travelling at the speed of light but close to it, I can move in other directions but would be very slow because there's only few "remaining" velocity left before exceeding speed of light. My biological processes and other changes would be slow therefore my time is also slow. Although my time has slowed down, I'll not be able to notice it because my perception has also slowed down along with my biological processes. But outside observers will be able to notice it.

Or to put it in another way, because subatomic particles already move close to speed of light, if I travel close to speed of light, that would leave almost no "remaining" velocity to subatomic particles that made my atoms that made me, again, rendering my biological processes to slow down. I presume this also affects any time measuring devices with me such as my wrist watch rendering it to slow down. If time is rate of change then we can safely say the local time has slowed down.

To rephrase it concisely, speed seems to cause "drag" against time because any speed reduces the rate of change in subatomic level locally including any time measuring devices.

That is how I understood time dilation in special relativity. Did I get the concept properly?

I refer to time as the rate of change locally and not universal.

UPDATE

To clarify further, is my understanding of the cause of time dilation correct? My question is not about measuring time dilation but how or why time runs slow relative to outsider as velocity increases.

Answer 1

You have not grasped the concept properly.

Here are some points you should try to build in to your thinking...

All speed is relative. That means you do not have a single absolute speed- you have any number of speeds. Relative to the chair you are sitting in, your speed is zero. Relative to a passing satellite your speed is a few kilometres per second. Relative to a certain high energy muon passing through the atmosphere, your speed is 0.9999c.

Since your speed is arbitrary, depending upon which frame of reference you decide to use to quantify it, the passage of time for you cannot be dependent on your speed. Your watch ticks and your heart beats at certain rates regardless of whether you consider yourself stationary in your chair or moving at 0.9999c creative to the muon.

You should not think of time dilation as meaning that time slows down.

Time dilation is an unfortunate term that is often misinterpreted. It refers to the fact that the temporal distance between two events is frame dependent. In your rest frame the gap between two successive beats of your heart might be one second. In the frame of the muon passing at 0.9999c, your heart beats about once per minute.

The effect has many analogies. Suppose you walk along your street at one pace per second, each of your paces being a metre long. In the frame of a person crossing your street at a metre per second (ie at right angles to the street) your speed is circa 1.41 metres per second, and each of your paces carries you 1.41 metres in that frame. By analogy we could call that 'pace dilation'- clearly it does not mean that your paces have changed, but just that their length depends upon the choice of reference frame in which they are measured.

If you want to understand time dilation properly, you should familiarise yourself with its cause, which is the relativity of simultaneity. That refers to the fact that a plane of constant time in one frame of reference is a sloping slice through time in any other frame moving relative to the first. The result is that clocks spread along a line in the first frame all show the same time at a given instant, but clocks in the other frame all show different times, the discrepancies increasing with distance from whatever point you pick as your origin. To see how this causes time dilation, imagine the following scenario...

You walk down a corridor at 1m/s. Every ten metres along the corridor is a person holding a clock. All the clocks tick at the same rate as your watch, but they are synchronised in such a way that every clock is set one second ahead of the previous one. If you start down the corridor at t=0 on the first clock, you will reach the next clock when your watch shows 10s, but the clock will show 11s as it has been set a second ahead. Likewise when you reach the next clock, your watch will show 20s while it will show 22s because it was set a second ahead of the previous clock. The next clock will show 33s while your watch will show 30s, and so on. It will seem, as you compare your watch with each passing clock, that your watch is running slowly when in fact your watch and the clocks are all running at exactly the same rate. The effect of time dilation arises not because your watch is running slow but because you are moving through a frame in which a plane of constant time is tilted relative to your frame of constant time.

The effect is entirely symmetrical. Suppose in your walk down the corridor you were followed at ten metre intervals by friends whose watches were each set one second ahead of the friend passing before them. From the point of view of the person holding the first clock in the corridor, you pass them at t=0. Ten seconds later your first friend passes them with a watch showing 11s. Ten seconds after that your next friend follows with a watch showing 22s. Your third friend passes when their watch shows 33s but the person holding the clock sees on 30s reading on it. So, the person holding the clock thinks their time is dilated compared with your friends watches, while you think your time is dilated compared with the clocks, even though all the clocks and watches are ticking at exactly the same rate.

Answer 2

Well your understanding is not accurate at all, but kind of good. So let me edit your story so that it is more accurate:

When something travels at high speed in one direction it can no longer have almost any velocity in any other direction, otherwise it would exceed the speed of light.

Let's assume Bob is traveling at high speed (and still human and alive) towards the direction Bob is facing. That means Bob can no longer move left or right, except very slowly. The same goes for all the atoms that Bob is made of including subatomic particles. All of Bob's atoms cannot move in any other direction, except slowly, rendering everything effectively "frozen". Bob's metabolic processes would slow down and so would Bob's wrist watch.

Same story from Bob's point of view:

Stars are traveling at high speed (and still not broken) towards the opposite direction that Bob is facing. That means stars can no longer move left or right, except very slowly. The same goes for all the atoms that stars are made of including subatomic particles. All of stars' atoms cannot move in any other direction, except slowly, rendering everything effectively "frozen". Stars' fusion processes would slow down and so would stars' atomic clocks.

To rephrase it concisely, moving clocks tick slowly. Fast moving things do everything slowly, except for the fast motion.

(Somewhat interesting problem: Bob, who sees stars moving very fast to the opposite direction to which Bob is facing, fires a side rocket which pushes Bob to the sideways direction. Will Bob see stars gaining lot of sideways speed? Correct answer: Yes. )

Answer 3

Congratulations. You have managed to understand something. Now maybe that something is not the "time-dilation". Maybe it's "Einstein Light Clock". Or maybe it's "how things move" or "kinematics".

Now maybe "time dilation" and "how things move" are somehow related. They could be related by mechanical clocks, like for example the "Einstein light clock".

So maybe this is the solution to the problems that you are having with the "time dilation"?