If you can’t explain it simply, you don’t understand it well enough.

Albert Einstein

I haven’t said anything on this topic for a while, and so I felt an uncontrollable urge to grumble a little more. As opposed to the previous monologues (weird to call those: “discussions” as I’m talking to myself and nobody disagrees or even listens), especially:  Part 1, Part 2 , Part 4 and Part 5, this part can be read separately. All you need to know is that in previous parts I was ranting about Einstein’s theory of relativity and the modern physics in general.

This time, I’m going to talk briefly (I hope) about early (pre-Michelson–Morley experiment ) roots of the relativity, but not as early as Galileo’s principal of relativity, in other words: about the time when the s@#t happened. The latest fad at that time in scientific circles was the idea that, in addition to the three dimensions (implying the rectangular, also called ‘Cartesian’ system of coordinate), which can be used to pinpoint any location in the observable universe, the fourth dimension of time should be considered too for registering the change, or for whatever other reason (one may only wander why wouldn’t they also add some other dimensions, like density, amount of radiation, etc. to screw things up even more).

So far so good: cool idea. Now, to convert this idea from purely philosophical to scientific, they needed to write it down as some mathematical equation, because that’s what scientists do to make things look scientific and publish their papers. So, if in the good old 3D world, any location could be described by 3 coordinates as a simple summation of coordinate vectors: X, Y and Z, in the new 4D world the time should be somehow crammed into this elegant equation. Unfortunately, trying to do so proved tricky, and all the elegance has been lost. The problem is that you can’t just add the time and the distance together, as those are measured in different units. After some head scratching, scientists arrived at the ‘aha’ moment. Basically, they figured that the easiest way to get distance out of time is to multiple the time by velocity (which also, conveniently, makes this a vector, meaning: adds a direction). Great! But… wait a minute… velocity of what? Well, the obvious thought would have been to use the velocity of the 3D location change, which you are trying to measure, relative to the center of coordinates (the point with X=0, Y=0, Z=0). That would have made a lot of sense, and maybe even somewhat preserve the elegance of the original equation, but the scientists don’t choose easy paths. “Let’s take a speed which we believe is constant” – they thought, and if that’s the case why not take the most famous one: the speed of light in vacuum (this is not the device you use to clean the carpet)? “Anyway, the fastest way we can observe the change is with speed of light” – they thought (which,eventually, proved to be untrue, but scientists are stubborn people and they don’t give up on their beliefs easily). Done. And thus, the s@#t happened. Now, the formerly pretty equation looks pretty much like this (coordinates are vectors): L = X + Y + Z + c*t. Here, the ‘L’ is the location in so-called: ‘space-time’, X,Y,Z are familiar coordinate vectors, c – is the speed (apologies: velocity) of light and t – is the time.

Now we are in the world, where whenever you want to actually measure relative change in location, you have to add another member: v*t, where v is the velocity of the change. As a result everything, including time and distance, depends on the v/c – the relative velocity of change with respect to the light velocity. Voila: time dilation!

From all of this comes a simple observation that all the predictions of the special theory of relativity are, in fact, not what actually happens to the time or distance, but rather what it seems to happen, if we observe the changes through the changes in light (or, more generally: changes in electromagnetic radiation we are able to register). Here: I’ll give you an example. Imagine a wall clock (let’s say it’s an electronic clock with a bright digital dashboard. The type of the clock doesn’t matter, of course, this is just to help your imagination and because I like it that way), which just turned to 3:00. For a person who sits right next to the clock the observation is almost immediate. She can look at her hand watch (I’m not being a feminist or sexists, it’s just: men don’t make a big fuss out of not using “gender neutral” nonsense, and it’s annoying to constantly use “he or she” and similar wording. So, all the observers here are females.) and observe that exactly one minute later, according to her watch, the wall clock will turn to 3:01. Now suppose that the wall clock is visible from outside (say, it’s on an electronic display on the building wall and our observer girl is enjoying her coffee in a nearby café). At the moment, when the clock displayed 3:00, the light from the digital display started to move with the speed of light into the universe. Now imagine some observer (girl 2), who is 5 light-minutes away from the clock and has really good optical equipment. She will observe the clock turning 3:00 at exactly 3:05 on her watch (assuming the watch and the clock are in sync, though this doesn’t matter). Also note, that the light from the watch displaying: 3:01, would have already reached 4 light-minutes from earth, 1 light-minute away from the girl 2.  Now also suppose that girl 2 moves away from the earth with a really high speed, say with the speed, which equals 50% of the speed of light. This means that she will be at 6 light-minutes from earth in two minutes (since she covers just 1/2 of a light-minute per minute), so her watch will display 3:07 when she gets there. However, in two minutes, the light from the clock, displaying 3:01 will reach that very point at that very moment (remember: it was 4 light-minutes from earth, and in two minutes, it has to be at the distance of 6 light-minutes from earth). And so, to the girl 2, it will seem that her time goes 2 times faster than the time she observes from  earth, while to the entire modern scientific community it will seem that a time dilation took place.

In similar fashion, you can easily explain other predictions of the special theory of relativity. E.g. the theory predicts that, if something moves with the speed of light from you, the time there stops completely. Well, suppose the girl 2 moves with the speed of light away from the clock, meaning the clock moves away with the speed of light from the girl 2. This means that if the girl observed 3:00 from the clock at some point, she will continue observing that time for as long as she moves with the same speed as the light from the clock showing 3:00. Similarly, relativity predicts that one can travel back in time if they move faster than light. Well suppose the girl 2 moves faster than the image from the clock. This means that she will start catching up with the previous images emitted from the clock, and that means, that, to her, it would seem that the time on earth goes backwards. The relativity of simultaneity and most other evidences of time dilation can be explained in similar fashion.

And so, it seems to me, that the whole thing is caused by some arbitrary choices made in the past. For a bit more detailed and technical monologue on the results of the Michelson–Morley experiment and other “evidences” of time dilation, please see my previous posts on this.

Thanks for listening.