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From the wikipedia article on tachyons:

Most physicists think that faster-than-light particles cannot exist because they are not consistent with the known laws of physics.[3][5] If such particles did exist, they could be used to build a tachyonic antitelephone and send signals faster than light, which (according to special relativity) would lead to violations of causality.[5]

Why would one consider hypothetical tachyonic particles impossible because of a causality, while leaving wormholes "sound"? Wouldn't messaging or travelling through a wormhole break causality just as communication using tachyons?

Update - CTC breaks down Really fast.. like Planck constant fast. So is it, that communication using tachyons as a carrier will inevitably violate causality.

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    $\begingroup$ Generally CTCs end up destroying themselves. A wormhole that violated causality is a CTC, and it will end up causing a feedback loop of vacuum fluctuations, and will destroy itself within the Planck time. $\endgroup$
    – Manishearth
    Jan 17, 2013 at 13:29
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    $\begingroup$ I feel the reverse question is more telling: Why do any physicists seriously think wormholes could exist, since they would cause all sorts of dilemmas? Then again, I don't know of many that do - perhaps wormholes are just better ingrained in pop culture. $\endgroup$
    – user10851
    Jan 18, 2013 at 3:29
  • $\begingroup$ 1)Wormhole-destroying feedback loops can be circumvented, if one assumes the Many Words Intepretation of quantum theory. 2)Physicist have put in a lot of work attempting to prove that wormholes cannot exist. So far, the existence wormholes remains consistent with the known laws of physics. $\endgroup$
    – Belizean
    Jan 23, 2013 at 1:08

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The difference is that in the case of wormholes, it is not certain that closed timelike curves (and thus violations of causality) actually occur, and if they occur, in which form. There are different approaches to the issue, for an interesting read (which also treats other kinds of spacetimes that potentially violate causality), see this. The general idea is that causality violations might be suppressed by quantum effects.

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  • $\begingroup$ Then to dismiss existance of tachyonic particles at all because of possibility to cause a causality violation, one must take as granted that whatever communication using tachyons as a carrier will inevitably screw up causality. $\endgroup$
    – elv
    Jan 17, 2013 at 14:00

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