Black holes and revelations in the Mail

Edit: After a quick email conversation with the author, the article has now been rewritten (direct link). Although it still has a slightly cringeworthy headline, it no longer contains misunderstandings about the paper and is all in all pretty good! I’ve hidden the original post behind the cut.

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39.34 metres per second, Marty!

This cat is a time traveller. From Wildstray on Flickr. CC by-nc-nd 2.0

Finally, after nearly two months, I get to write a post on my actual subject of study: physics!

The Telegraph today gives us the startling headline “Quantum time machine ‘allows paradox-free time travel’“. There were precisely two pictures that could have illustrated this article: the TARDIS and the Delorean. This time, the article is headed with a still of Doc Brown and Marty McFly climbing into their car.

The “time machine” described effectively allows you mess with quantum probabilities, choosing or “postselecting” the history you want to have happened by making it as likely as possible.

Now I’m torn on this one. On the one hand, the article is about a complicated topic which is hard to explain in layman’s terms, and they have tried to find academics to help analyse it and the central point of the paper – that quantum postselection won’t let you kill your granddad (or indeed become him) – still stands clear. On the other hand, the article is so sensationalist that the actual science behind it is a little lost behind all the “Whoosh! Back to the Future!”. Let’s go through the article point by point.