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One of Important conclusions of Einstein's Theory of Relativity is that we cannot cross or break the speed limit set by the laws of physics that is the speed of causality
consider this scenario:
suppose I somehow built a spaceship and is able to reach 99.99.......% the speed of light. After achieving this much speed i somehow turned on the boosters on my shuttle.
will I be able to cross the limit by turning on the boosters if no what will actually happen to spaceship and where will the work-done by the boosters go. can expect to be in another universe having different laws and speed limits.