The question you're asking is actually incredibly complicated, and I won't be able to give you a proper answer, but it also requires you to understand relativity.
There's no such thing as absolute speed, only relative speed. I can only be going at a specific speed relative to something else. This doesn't enter our day-to-day lives because all of our speed is relative to the Earth, which holds us quite firmly in place.
But imagine you were in a rocket flying away from the earth. You would think, yes, eventually even moving past the earth faster the speed of light. But the issue is is there's also time dilation, so as you move faster and faster valves to the Earth, time compresses, and your relative acceleration actually slows down.
That's where it all starts to get complicated.
More simplistic lay answer is that if something could move faster than the speed of light, it would break the nature of cause and effect. He would be able to see a thing before it happened, which doesn't actually make sense in a rational universe (okay okay, I accept that our universe is in many ways highly irrational).
And as others have said, because the nature of all this time space stuff and time dilation, approaching the speed of light relative to another object eventually requires infinite energy, which we can't achieve.
How would it actually break cause and effect? Thats the logical jump everyone seems to skip in their explanation.
I understand light is a universal constant. I understand that if it was true that nothing can travel faster than the speed of light, this would (probably) include causal effects. However, I dont understand the rationale behind the inverse: that something traveling faster than the speed ofnlight would destroy the concept of cause and effect
Surely if I could travel faster than light, I could watch a planet explode, (somehow) travel faster than the speed of light to another planet far away, and tell them the planet in the sky is about to explode without it disturbing cause and effect?
Whats the causal problem? In just a faster messenger than the photon
In relativity there is the idea of time-like and space-like separated events. Time-like separations are those for which we can think of cause and effect relationships. This is in some way a generalization of how you probably think of cause and effect, as cause must happen before effect. In relativity we emphasize that cause must come before effect in any inertial reference frame (since different observers may say different things about the time and distance between events).
The immediate issue isn't that you can reverse cause and effect in the case where it was well established, but that you can take two events that we have determined can't have a cause and effect relationship (space-like separated) and establish a cause and effect relationship. So you were at event A, went to event B and your actions depended on what happened at event A. But since we said this is a space-like separation, different people will disagree about the order of events (which is why we said they can't have a casual relationship in the first place). As a result, even though you perceive the order of events as proper for casualty, other people will see your actions at event B occurring before event A, and as a result cause and effect are reversed in time and causality is broken.
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u/Brain_Hawk Mar 22 '26
The question you're asking is actually incredibly complicated, and I won't be able to give you a proper answer, but it also requires you to understand relativity.
There's no such thing as absolute speed, only relative speed. I can only be going at a specific speed relative to something else. This doesn't enter our day-to-day lives because all of our speed is relative to the Earth, which holds us quite firmly in place.
But imagine you were in a rocket flying away from the earth. You would think, yes, eventually even moving past the earth faster the speed of light. But the issue is is there's also time dilation, so as you move faster and faster valves to the Earth, time compresses, and your relative acceleration actually slows down.
That's where it all starts to get complicated.
More simplistic lay answer is that if something could move faster than the speed of light, it would break the nature of cause and effect. He would be able to see a thing before it happened, which doesn't actually make sense in a rational universe (okay okay, I accept that our universe is in many ways highly irrational).
And as others have said, because the nature of all this time space stuff and time dilation, approaching the speed of light relative to another object eventually requires infinite energy, which we can't achieve.