Given that there is no known physical theory that allows deliberate time travel (rather than being stuck in a loop forever to begin with), I am confused as to how you can estimate the cost of it.
The big reason to travel to the present is to colonize space before we do. A sufficient reason it can't be done would be if our exponentially many possible futures would need to coordinate on it.
The lack of time travellers visiting us may be seen as evidence that time travel is not possible. In this article, I argue an alternative explanation is that we are not economically important enough to our descendants to justify the costs of time travel. Using a cost-benefit analysis, I elaborate on this argument. I suggest that the major cost of time travel is likely to be the energy cost, while the largest benefit of time travel is knowledge which the present possesses, but the future has lost. Focusing on this benefit component, I argue it is extremely unlikely that we possess a piece of knowledge which is sufficiently important to a future civilisation (system critical), but also has been lost by this civilisation. This is to say, we may not have been visited by time travellers because we are not important enough.
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Seeds of Science is a journal (funded through Scott Alexander's ACX grants program) that publishes speculative or non-traditional articles on scientific topics. Peer review is conducted through community-based voting and commenting by a diverse network of reviewers (or "gardeners" as we call them). Comments that critique or extend the article (the "seed of science") in a useful manner are published in the final document following the main text.
We have just sent out a manuscript for review, "The Economics of Time Travel", that may be of interest to some in the LessWrong community so I wanted to see if anyone would be interested in joining us as a gardener and providing feedback on the article. As noted above, this is an opportunity to have your comment recorded in the scientific literature (comments can be made with real name or pseudonym).
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