Tachyons are a hypothetical particle that constantly move at speeds in excess of the speed of light. We haven't yet proven their existence, but neither have we disproved their existence (which is, as far as I know, impossible to do: one cannot prove a negative).

We have a clear ability to detect and identify creatures that are comprised of particles that move slower than the speed of light, so we know they exist. We are proof of that!

Let's suppose that tachyons do exist, but we simply lack the means at this point in time to detect them. Could it be possible that a creature made of particles that constantly move faster than the speed of light exist in our universe?

Were a high-energy creature to exist, how would it interact with the material universe we commonly perceive, if at all?

Lastly, if we were to finally detect high-energy particles and, following that, a creature made of them, how might we, as material creatures, experience communication with such a high-energy creature?

For your answer, you may refer to any creature made of faster-than-light particles as high-energy and any creature made of slower-than-light particles as material. I am interested in answers based in science, but I am not marking this as hard-science because I am aware that faster-than-light particles are purely theoretical according to our current understanding of physics.

I am not concerned with such a creature's development in this question, merely its possible existence and interactions with its environment.

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    $\begingroup$ Thank you for not putting the science-based tag on! $\endgroup$
    – HDE 226868
    Commented Jul 14, 2015 at 23:54
  • 2
    $\begingroup$ @HDE226868 It's seen enough abuse already. $\endgroup$
    – Frostfyre
    Commented Jul 15, 2015 at 0:00
  • $\begingroup$ If relativity is correct, it should be possible to have tachyon worldlines that loop back into their own past (as well as arbitrarily far into the past of slower-than-light objects), see the tachyonic antitelephone for details. $\endgroup$
    – Hypnosifl
    Commented Jul 15, 2015 at 0:15
  • $\begingroup$ @Hypnosifl That wikipedia article contained some really weak argument against the possibility of causal paradoxes being sustainable: "Einstein (and similarly Tolman) concluded that this result contains in their view no logical contradiction; he said, however, it contradicts the totality of our experience so that the impossibility of a > c seems to be sufficiently proven." Really? In everyday life we don't see gravity effects on time, either. Plus, we've defined the cause-effect relationship temporally, anyway; it could be happening all the time, only we mislabeled the cause as effect. $\endgroup$ Commented Jul 15, 2015 at 1:44
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    $\begingroup$ @Hypnosifl Damned quantum gravity. Ruining everyone's fun. Well, at least it's fun to say. $\endgroup$ Commented Jul 15, 2015 at 2:11

1 Answer 1


People who invoke tachyons need to "keep reading": http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/tachyons.html

The bottom line is that you can't use tachyons to send information faster than the speed of light from one place to another. Doing so would require creating a message encoded some way in a localized tachyon field, and sending it off at superluminal speed toward the intended receiver. But as we have seen you can't have it both ways: localized tachyon disturbances are subluminal and superluminal disturbances are nonlocal.

As for a creature made of such particles, how can you have solid objects or any kind of structure at all when the particles travel faster than light relative to each other? It's not like you can have them in formation traveling fast only from your point of view. Special Relativity still holds.

You can find lectures by Leonard Suskind on youtube, meaning anyone can effectively audit his classes at Stanford, for free. This includes full courses in quantum mechanics and introduction to string theory. In one class he covers what a negative mass-squared term really means (an inverted pendulum energy state) and how they end up propagating waves at normal light-speed anyway.

For your specific points,

  • structures could not exist. The particles move faster than light relative to each other.
  • they don't really travel faster than light, anyway.
  • how would it interact? How indeed. Come back to that below. Communication is in the same boat with detection in the first place.

My only thought would be an energy being trope⚠. A quantum field is the fundamental thing, and "particles" are quantized excitations in the field. There are also "virtual particles" and other non-particle excitations and disturbances. In a tachyonic field, the idea of particles gets weird, and being different from quantum fields we're used to you could handwave some effects that exist as patterns in the field with extended lifetimes that are not giving rise to conventional particles. Few hard SF readers would find it implausible, especially if you explained all that and used it to make an energy being more plausible than normal.

You still have to figure out how to get it to interact with normal matter and electromagnetism. That is a problem with any exotic matter that's not atoms and not electrically charged. You get "dark matter", and a dark matter monster could be here right now and not bother me in the slightest!

The tachyons analyzed in the linked treatment are Bosons. Let's suppose you have a fermion version and your creature is made from that. Fermions affect each other via bosons, which are associated with forces (or more generally, interactions). The exotic material needs to share a charge property with our kind of stuff. E.g. if it was electrically charged, it would interact with atoms via electromagnetic phenomena. It would also release Cherenkov radiation with exponentially increasing energy forever, so that's not good.

Real dark matter candidates and seriously considered un-discovered particles include WIMPs, which interact via the weak force. So plausibility leads you there as the path of least resistance.

There's always gravity. But detecting small objects via gravity would be difficult. Maybe anomalies in gravity measurements lead to the discovery, from other experiments involving measuring gravity over short distances. Maybe the WIMP clouds are attracted to our apparatus being used to probe for large extra dimensions or make a perfect reproducible kilogram standard, and these turn out to be not simple clouds but life.

  • $\begingroup$ At least I know my dark matter creatures are plausible. Thanks for the information! I suppose I'll have to continue holding my other high-energy creatures together with magic... $\endgroup$
    – Frostfyre
    Commented Jul 15, 2015 at 12:07
  • $\begingroup$ Question: Can you have a "localized tachyon field" the size of the creature? Then particles could be encoded and travel to their destination without ever leaving the field. $\endgroup$
    – Frostfyre
    Commented Jul 15, 2015 at 18:19
  • $\begingroup$ The field fills all space, everywhere. You have patterns of disturbances in some area. It's the same with the electron field (not the same thing as an electric field) makes electrons as excitations in the field. The field is singular, everywhere. You might look up "second quantization" for some concepts of quantum field theory. $\endgroup$
    – JDługosz
    Commented Jul 15, 2015 at 22:59
  • $\begingroup$ I don't see why you couldn't have tachyons that keep formation in someone else's reference frame. If a tachyon travels only slightly faster than speed of light, it would take a long time for the tachyon group to diverge due to the large negative time dilation. $\endgroup$
    – Fax
    Commented Oct 2, 2015 at 10:33
  • $\begingroup$ @fax you might be able to handwave something plausible to readers along that line; see Pohl's Macroscope for example. A tachyon only slightly faster than light (nieve particle interpretation, disregarding the "keep reading" part) would have very high energy. Good point that their very presence could have meaning to an observer, even though they are not interacting with each other. $\endgroup$
    – JDługosz
    Commented Oct 2, 2015 at 20:55

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