660: Sympathy

Explain xkcd: It's 'cause you're dumb.
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Excellent recovery:... which we could try to use to somehow save your original brother!
Title text: Excellent recovery:... which we could try to use to somehow save your original brother!


This comic targets the lack of social skills physicists are generally believed to have. The example displayed is a case of condolence, in which the appropriate behaviour would of course be to express compassion with the bereaved.

In the third panel, the physicist does not display the endorsed demeanour. Instead, he takes a scientific approach towards the statement of his friend. He points out that the transmission of the pain the latter believes to have felt, is in fact limited by the speed of light and could therefore not have been 'instant'. By saying so, he betrays an absence of feeling towards his friend, as well as his inability to understand the figurative sense of the words.

In the last panel, the physicist reflects on the consequences that would follow if the statement of his friend were indeed literally true. According to special relativity, any object travelling faster than at the speed of light would in fact move backwards in time. The physicist therefore plans to utilise this effect in order to construct a tachyonic antitelephone, a device that allows sending information to the past. To confirm the initial condition, he makes the utterly inappropriate proposal to start a series of measurement with other family members of his friend.

A correction of the misdemeanour is suggested in the title text: The antitelephone might be used to change causality and save the original brother from dying in the first place. Of course, saying the latter would not improve anything in the given scenario.


Sympathy Tips for Physicists
[Cueball and friend are talking.]
Cueball: The moment my brother died, I felt a searing pain in my heart.
Friend: I'm so sorry.
Friend: Was it instant, or was there a speed-of-light delay?
Very Wrong:
Friend: If it was instant, with the right arrangement of moving reference frames, we could use this to send signals back in time and violate causality! How many remaining siblings do you have?

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Someone might want to fix this - I don't know how. When I click the "next" arrow at the top, instead of taking this page to 661, it opens up an entirely new window for 661. 21:10, 18 November 2015 (UTC)