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Astrobiologist: Why time travel can’t really work

File:Wooden hourglass 3.jpg
passage of time, imaged/S. Sepp

Recently, cosmologist Carlo Rovelli, author of The Order of Time, argued that time travel, especially into the future, can work.

However, astrobiologist Caleb A. Scarf sees an insurmountable barrier, which he calls the “spatial problem”:

Let’s take the Earth’s motion around the Sun. A month of orbit corresponds to moving in an arc of approximately 78 million kilometers. During that same period the entire solar system will have also moved approximately 600 million kilometers around our galaxy, and our entire Local Group of galaxies will have swept through about 1.7 billion kilometers of space relative to the cosmic microwave background. Not only do you need to traverse those kinds of distances, you need to get it correct to within a part in a trillion.

So you need to be in the right place, not just at the right time. Here’s the problem:

Earth’s spin varies, its orbit varies subtly over very long timescales, and even our intergalactic motion will evolve as other galaxies and mass concentrations get closer or further away over time. Caleb A. Scharf, “The Utter Failure of Fictional Time Travel” at Scientific American

The future called and said, with respect to visiting us, the problem is, we’re not sure where we are going to be that weekend…

See also: Carlo Rovelli: Future time travel only a technological problem, not a scientific one. Rovelli: A starship could wait [near a black hole ] for half an hour and then move away from the black hole, and find itself millennia in the future.


Rob Sheldon’s thoughts on physicists’ “warped” view of time An attempt to force complete symmetry on a universe that does ot want to be completely symmetrical

The very best time travel book, and probably Asimov's best story, is The End of Eternity. If you like to think about time travel, this book is excellent: https://www.amazon.com/End-Eternity-Novel-Isaac-Asimov-ebook/dp/B003CSOSRI jdk
Time travel has been blocked by God because He doesn't want us taking selfies at the Crucifixion. EvilSnack

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