Let me ask a thing about the Speed of Light

[Azar525]

TL;DR Summary

Why we cant go faster then the speed of light?

So let me ask a question about the speed of light. Why can't we go faster than the speed of light? I understand the idea with the photon clock — the clock slows down as you move faster because the photon has to travel a longer distance. But theoretically, if we throw a rock at a wall, it would never hit the wall because the distance keeps halving, getting smaller and smaller. But theoretically, it could keep halving infinitely, so the rock would never reach the wall. However, in real life, it does.

So if we try to travel at the speed of light, it looks like time slows down from our perspective because the photons we see move slower. But I don’t think that necessarily means time itself slows down. It just means we can’t rely on our eyes anymore because they’re no longer accurate.

So if we try to apply the same reasoning to the speed of sound, I think we can’t go faster than that... How is it that if we go faster than the speed of sound, we can't hear the sounds? We’ve left them behind. I think it’s similar... we can go faster, because both are waves, but the difference is that one is much faster, and we rely more on our eyes. Or maybe I don’t understand something important about the relationship between time and photons? I think it’s possible to go faster than the speed of light, but we just can’t do the math right yet because we don’t have enough knowledge to figure it out.

 

[phinds]

Why can't we go faster than the speed of light?

Because it is a fundamental speed limit. It would take infinite energy just to go AT the speed of light (for anything with rest mass)

I understand the idea with the photon clock — the clock slows down as you move faster because the photon has to travel a longer distance.

No, it does NOT slow down. It APPEARS to slow down to some observers, but locally it ticks at the same one second per second as your alarm clock.

But theoretically, if we throw a rock at a wall, it would never hit the wall because the distance keeps halving, getting smaller and smaller. But theoretically, it could keep halving infinitely, so the rock would never reach the wall. However, in real life, it does.

Yes, this is just a silly mis-application of math. Google "Zeno's Paradox"

So if we try to travel at the speed of light, it looks like time slows down from our perspective because the photons we see move slower.

No, first we cannot travel at the speed of light and second even if we were traveling at very close to the speed of light, nothing slows down for us.

But I don’t think that necessarily means time itself slows down.

Right. Time does NOT slow down.

It just means we can’t rely on our eyes anymore because they’re no longer accurate.

We can rely on our knowledge of physics PLUS our eyes.

So if we try to apply the same reasoning to the speed of sound, I think we can’t go faster than that... How is it that if we go faster than the speed of sound, we can't hear the sounds? We’ve left them behind. I think it’s similar... we can go faster, because both are waves, but the difference is that one is much faster, and we rely more on our eyes.

Sound and light do not act the same. That is a fundamental issue you are going to have to address. You CANNOT apply "sound logic" to light. It doesn't work.

Or maybe I don’t understand something important about the relationship between time and photons? I think it’s possible to go faster than the speed of light, but we just can’t do the math right yet because we don’t have enough knowledge to figure it out.

Yes, there is something you don't understand. I suggest you read some basic physics (NOT popular science nonsense but actual physics texts).

 

[Ibix]

So if we try to travel at the speed of light, it looks like time slows down from our perspective because the photons we see move slower.

This is completely backwards. Light always travels at the same speed, so we always see our own light clocks ticking at the same rate. It is always other people's light clocks that we determine are ticking slowly.

Or maybe I don’t understand something important about the relationship between time and photons?

First off, don't use photons, use light pulses. Photons are quantum mechanical objects and extremely complex and subtle and they do not work like you think they do.

There is, fundamentally, no relationship between light and time. It just turns out that there is an invariant speed (i.e. one that, if something travels at it, everyone measures the same speed relative to them), a fact which you can derive without once mentioning light. If there is an invariant speed you can never reach it, because you can always regard yourself as "at rest" and you always have to accelerate to try to reach the invariant speed - so you cannot succeed.

Light turns out to travel at the invariant speed because it is massless, and "massless" and "travels at the invariant speed" turn out to be two ways to say the same thing. But the important thing about $c$ is that it is the invariant speed,not that light happens to travel at that speed in vacuum.

 

[Dale]

So if we try to travel at the speed of light, it looks like time slows down from our perspective because the photons we see move slower. But I don’t think that necessarily means time itself slows down. It just means we can’t rely on our eyes anymore because they’re no longer accurate.

Relativity is not based on optical illusions or relying on vision. It would occur even if we were blind.

Relativity is based on the fact that the speed of light is invariant. This is the key. Relativistic effects come from the fact that two observers in relative motion will measure the same beam of light to be going at $c$ in each of their reference frames.

So if we try to apply the same reasoning to the speed of sound, I think we can’t go faster than that...

The speed of sound is not invariant, so the reasoning does not apply. Two observers in relative motion will each see a given sound wave moving at different speeds in their frames.

Or maybe I don’t understand something important about the relationship between time and photons?

I think that you are missing the invariance of $c$.

I think it’s possible to go faster than the speed of light, but we just can’t do the math right yet because we don’t have enough knowledge to figure it out.

We have been able to do the math for going faster than $c$ for more than 300 years. We have been able to do the math for not going faster than $c$ for more than 100 years.

The question isn’t whether we can do the math. The question is which of the two versions of the math actually describes the physical universe. That is a question that can only be answered by experiments. The resounding experimental answer is that the not going faster than $c$ math accurately describes the world.

 

[Mister T]

TL;DR Summary: Why we cant go faster then the speed of light?

So let me ask a question about the speed of light. Why can't we go faster than the speed of light?

I'm not sure anyone can answer that! We live in a universe where the speed of light is invariant, meaning everyone will observe light having speed $c$ regardless of their own speed relative to the source of the light. It's possible that that's not true, but every experiment and observation done so far is consistent with it being true.

So, if the speed of a beam of light is the same to you, no matter how fast you travel in an attempt to catch up to it, that means you can never reach light's speed.

This idea is by no means easy to accept, and many if not most of the physicists refused to accept it at the time that Einstein proposed it. It took lots of experimental verification for it to be accepted. But all that happened well over 100 years ago. Nowadays it is an accepted fact of life for thousands of scientists, engineers, and technicians working at numerous places scattered all over the globe.

But theoretically, if we throw a rock at a wall, it would never hit the wall because the distance keeps halving, getting smaller and smaller. But theoretically, it could keep halving infinitely, so the rock would never reach the wall. However, in real life, it does.

That's one of Zeno's paradoxes, dating back to the Ancient Greeks. It has nothing whatever to do with the speed of light, or the logic used to understand the invariance of the speed of light.

So if we try to travel at the speed of light, it looks like time slows down from our perspective because the photons we see move slower.

You are talking about the phenomenon of time dilation, and that's not the reasoning used to explain it. By the way, time dilation is also well confirmed by experiment and observation, and is an accepted fact of life for thousands of scientists, engineers, and technicians working at numerous places scattered all over the globe.

Saying that time slows down is a poor characterization of time dilation.

 

[Sagittarius A-Star]

So if we try to travel at the speed of light, it looks like time slows down from our perspective because the photons we see move slower.

The photons don't move slower.
Do you apply here the Galilean velocity composition $v_{\text {total}}= v_1 + v_2$ with $v_1 = -v_{\text{observer}}$ and $v_2 = c$ ?

The Galilean velocity composition is only an approximation for small velocities.

Instead, you need to apply the relativistic velocity composition
$v_{\text {total}}= (v_1 + v_2)/(1+v_1 v_2/c^2)$.

Source:
https://en.wikipedia.org/wiki/Velocity-addition_formula#Special_relativity

 

[Sagittarius A-Star]

I understand the idea with the photon clock — the clock slows down as you move faster because the photon has to travel a longer distance.

The longer distance is not the interesting part of the explanation.

The not-so-intuitive (relativistic) part of the explanation is, that the photon moves over this longer distance with the same speed $c$ that it has with reference to the rest-frame of the light clock, and not with $\sqrt{c^2+v^2}$.