|Welcome for time travellers|
On May 2 2017, Newsweek published an article with this title:
Time travel is mathematically possible with mind-boggling model
You may well imagine that, with that title, the article will rather fall into the category of sensationalist papers on seemingly scientific issues. Indeed, in a quick reading of this article I have detected the following inaccuracies:
- The title does not make clear the difference between a theoretical possibility of traveling in time and building a time machine. That is, the different between theory and practice. What Ben Tippett has developed is a purely theoretical mathematical model.
- It presents the idea as something new which puts an end to a string of failures and disappointing calculations. Space-time loops, however, are known to be compatible with the general theory of relativity since quite a long time ago. In 1992, for instance, Stephen Hawking came to the conclusion that it would not be possible to use them without negative energy, something that is not known to exist. In 2005, the Israeli Amos Ori proposed a procedure that would not require it, consisting of spinning around an empty toroid region surrounded by a sphere containing enormous amounts of matter (e.g. a black hole). This is not so different from what is being proposed now.