Newton and Einstein were two milestones in evolution of mankind (and the science). They were the curious thinkers who took the human race forward.
Newton was the person who started with optics and told the world that when light passes through a prism, light is not modified, rather separated. He later went on to develop the theory of universal gravitation, fundamental laws of motion, calculus and a lot more.
He proved things through experiments and mathematics. In his own words, he did not believe in making hypotheses. He meant, ‘I lay down a law, and derive the phenomenon from it.’
And then, there was Einstein. Einstein developed the general and special theory of relativity, mass-energy equivalence and discovered photoelectric effect. He was the person who was more philosophical in his theories rather than mathematical. He did a lot of thought experiments, which became foundations for his theories.
The genius of men like Newton and Einstein lies in that they ask simple questions which turn out to have anything but simple answers.
An Einstein’s Thought Experiment
There’s one thought that Einstein had in his teens, which was, ‘What would the world look like if I rode on a beam of light?’
To understand this, let’s do this thought experiment together. We’ll imagine a setup like this:
We have a clock and I am sitting on a rocket, which moves at the speed of light.
We know that we see clock (and the time it is showing) because the light is coming from clock to our eyes. As soon as the clock ticks 3 o’clock, I start moving at the speed of light away from clock. I am moving right alongside the light that left the clock at 3 o’clock and whenever I look back to see the time, I always see the clock showing 3 o’clock.
The time stopped moving. If Einstein rode on a beam of light, the time suddenly would come to stop.
Or does it?
I understand this experiment and that how one perceives time is relative to him individually. But, I’ve got totally stumped when I made a few changes to this experiment.
Instead of me moving away from clock, what if I move towards the clock at the speed of light as soon as it ticks 3 o’clock. What would happen then? Will time move at double the speed for me? Probably.
When moving “away” from the clock, as I approached the speed of light, time slowed down and at hitting the speed of light, it stopped for me. Probably, when moving “towards” the clock, as I’ll approach the speed of light, time will move faster and at hitting the speed of light, it’ll move at double the speed of time.
What if, I ask the same question that Einstein asked in his teens?
“What would the world look like if I rode on a beam of light?”
Will the effect be same in any direction? Will time move slower or faster? Or…
Now, we’ll just do another version of the same thought experiment? This time with two clocks. Bring in two clocks!
The two clocks are placed opposite to each other, and I am sitting on a rocket such that while rocket will move away from one clock, it will move closer to another.
When both the clock ticks 3 o’clock, I start moving at speed of light, away from one clock and towards another, will time stop for me or will be move at double the speed?
I tried answering this question myself. I am not physicist, but here’s my take on the situation with two clocks.
A Little Flaw
I find that the situation “when both the clocks ticks 3 o’clock” is a bit flawed. I’ll tell you how.
Light does not move with an infinite speed. Thus, it will take some time for it to reach from the clocks to me. Because I am nearer to one clock, light from it will reach faster to me as compared to the clock which is far from me.
To make things simple, let’s just assume that the two clocks are separated by a distance of 10 light seconds. This means that, the light will take 10 seconds to reach from the distant clock to me. Thus, when I see the clock nearer to me showing 3 o’clock, the distant clock shows 2:59:50.
And fundamentally, I cannot take off “when both the clocks ticks 3 o’clock”, because they never will.
Fixing The Flaw
Okay, so, instead of taking off when both the clocks ticks 3 o’clock, we will take off when the clock near to us will tick 3 o’clock and the distant clock will show the time as 2:59:50.
I take off at the speed of light and starts moving away from the clock showing 3:00:00. For my whole journey to the distant clock, this clock will continue to show me 3 o’clock and time has stood still for me. But when I look at the distant clock, towards which I am approaching, I see it running at double the speed.
When I cover 50% of the distance (five light seconds), I see the distant clock showing 3:00:00 too. Now, I am in middle of two clocks and both of them shows the same time, which is 3:00:00. And I am still to cover the other half of the distance.
The other half will take me five more seconds to cover, and when I reach at my destination, I see the final clock showing 3:00:10, while the clock from where I started my journey is still showing me 3:00:00.
At the beginning of my journey, the difference between the two clocks was 10 seconds, and at the end of journey, the difference is still 10 second. So, what just happened?
- With respect to first clock, did I travel distance of 10 light seconds, without spending any time?
- With respect to the second clock, did I travel distance of 10 light seconds in 20 seconds, even when traveling at speed of light?
- Am I in past now? Or in future? Or just, still in present?
These are still the questions hovering in my mind, to which I suspect, the answer would be “relativity”. But whole of this time, I was noticing time from my own point of view. When experiencing time from same point of view, shouldn’t we experience the same thing?
“Experience” the same thing? But what exactly this “experience” mean?
Let’s Dump The Light
Until now, we had been studying time by “looking” at it. It definitely is a valid way to experience something, but is it the only way to experience?
Asking this question, made me conduct another thought experiment, this time without “looking” at the clocks.
In this version of the same experiment, I’ll be eye-less. No more “looking” at the clocks!
We’ll just assume that humans are not blessed with a light sensor (eyes). But, we’ve got ears. Thus, we have developed clocks, which tell us time using sounds, say “tick” “tock” “tick” “tock”.
So, this time, we will take off on our rocket when we hear “tick” from the clock. But at what speed? Yes, at the speed of sound. Humans do not have eyes and thus we are unable to understand any concept related to light. For us, maximum speed of something is maximum speed of sound.
I hear a “tick” from the clock and I take off at the speed of sound. The sound of that “tick” travels with me, and what do I feel? I feel exactly the same thing that I felt in case of light - time stopped moving.
Did the universe just change its laws because human beings lacked a sense organ? Just because we lacked light detectors, did speed of sound became the maximum limit of speed - the speed at which I could travel in time?
My question is, “what if we humans are simply lacking a sense organ to detect the energy that binds the relativity together?”
An energy other than light, which must be existing in universe, but going all through us, without getting detected? What could that be? I’m not sure. But the definition of this energy sounds so similar to definition of something that we are already familiar with.
Not Light, Instead Something Dark
This is something I am not too much familiar with - Dark Matter and Dark Energy. What I know is that about 95% of the known Universe is composed of dark energy and dark matter.
What this dark matter/or energy is? No body knows? Why? Because we cannot detect it. We know it’s out there in abundance, but what is it, we don’t know.
How do we know it exists? Because of discrepancies between the mass of large astronomical objects determined from their gravitational effects and the mass calculated from the observable matter (stars, gas, and dust) that they can be seen to contain.
Why cannot we detect it? They pass through everything. Right now, dark matter is passing through you without stopping. Yes, it is goes right through everything, even our detectors.
No Answers, Just More Questions
If you are feeling like asking, “why do you feel it is dark matter, that is the binding bridge between relativity,” let me tell you my friend, I am not trying to answer anything. I am too naive for that. All I am doing is trying to connect several things together which I know of. I am sure, there are thousand other things, which I do not know of (yet). Therefore, I can be plain WRONG. :)
Still, I feel dark matter as a viable candidate because of the following reasons:
Nothing could go faster than light, until, we found that the space itself was expanding at speed faster than light. We modified our understanding to “nothing can go faster than light in space; however, space itself can go as fast as it desires”. Shouldn’t a law just apply to everything?
Sound is affected by the medium it travels through. It’s speed changes in different media. Light overcomes that shortcoming. It is constant everywhere. Until some object blocks it. That’s the shortcoming of light. Next logical extension to this shortcoming could be “going right through everything”, which dark matter does.
The question, my curious mind asking is:
“Isn’t it possible that something else that we cannot detect (yet) be the bridge between relativity?”
I Don’t Know
I don’t know answers to any of the questions I asked. I am not a physicist. I am not a scientist. I am just a normal guy with a curious mind. (A mind which has given birth to a lot of such thought experiments, even about Aliens.)
I take interest in trying to understand physics, universe, time and space, but I am not familiar with mathematical side of it. It is possible that my questions are right out silly to you. If that is the case, I’ll be very thankful, if you can direct me to some links, resources or papers, where I can find answers to these.
All I know is that I’m curious and eager to find out answers to these questions.
Lastly, Gravitational Time Dilation happens because the warp in space-time is so much due to gravity that to keep the speed of light constant, time has to move slower. To keep the speed of light constant because light is an energy that we can observe?
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