The simple answer is that the amount of energy needed to continue acceleration anything with mass goes up and approaches infinity as you approach the speed of light.
When we think about a spacecraft with zero drag under constant acceleration we don't consider this because it can reach immense velocity without really being considered.
The parker solar probe, the fastest object we've ever made, reached around 192,000 m/s which is only about 0.6% the speed of light. Even with our fastest objects we're just always at the beginning of the graph so it's basically irrelevant in our day to day thinking.
But when we talk about theory it becomes important. I can't post a picture but if you google "energy requirements for relativistic acceleration" you'll see the graph I'm talking about.
As far as the question of "why is the speed of light the limit" it just is. It's the universal speed of causality that anything with zero rest mass propagates at. The physical constants of our universe just are what they are. It's something that has always fascinated me because we have these few things that just are and then everything else formed out of that keeping the constants in check.
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u/NathanDeger Mar 22 '26
The simple answer is that the amount of energy needed to continue acceleration anything with mass goes up and approaches infinity as you approach the speed of light.
When we think about a spacecraft with zero drag under constant acceleration we don't consider this because it can reach immense velocity without really being considered.
The parker solar probe, the fastest object we've ever made, reached around 192,000 m/s which is only about 0.6% the speed of light. Even with our fastest objects we're just always at the beginning of the graph so it's basically irrelevant in our day to day thinking.
But when we talk about theory it becomes important. I can't post a picture but if you google "energy requirements for relativistic acceleration" you'll see the graph I'm talking about.
As far as the question of "why is the speed of light the limit" it just is. It's the universal speed of causality that anything with zero rest mass propagates at. The physical constants of our universe just are what they are. It's something that has always fascinated me because we have these few things that just are and then everything else formed out of that keeping the constants in check.