Can only go back to when you started operating the device. So, basically the Primer time machine, except the math says it has to be done at galactic black hole amounts of energy sort of scale.
Mallett’s vision for a time machine centers on what he calls “an intense and continuous rotating beam of light” to manipulate gravity. His device would use a ring of lasers to mimic the spacetime-distorting effects of a black hole.
Good for you commenting on the title alone! If you looked at the actual article you would know that one of the limitations is, that the furthest point you can reach going back in time is when the “time machine” was first activated.
@inkican Going back in time would require more energy than is available in the universe, for going faster than the speed of light, which is impossible. That's the basis in the theory (should be called 'law' by now) of relativity.
Backwards time travel would obviously interfere with causality in creating an alternative past, which would lead to a different present. So it's a good thing that it's physically impossible, despite what a desperate astrophysicist believes.
The idea is that you can go backwards in time by going faster than light. The speed of light is actually the speed of information itself - so if you could go faster than that, you’d be going backwards in time.
However, Einstein showed that nothing can accelerate to the speed of light. You’d need infinite energy to actually reach the speed of light, and infinite energy is assumed to not be possible.
I wonder if there is a meaningful difference between your example, and the technology with which the JWST uses to view light in the past. Rather, if the later is something we can use for time travel ;)
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