# What Types of Radiation Emanate in the Future and are Perceived in the Present?

Years ago I came upon a scientific text which mentioned different types of radiation and how they are perceived. One such form of radiation was described (from our perspective and understanding of space-time) to originate from the future and travel backwards through time.

I cannot for the life of me remember what this type of radiation was called and I would love to know it.

• A search on retrocausation will get you in deep very quickly: google.com/search?q=retrocausation&ie=utf-8&oe=utf-8 Quantum pilot waves are also troublesome:en.wikipedia.org/wiki/Pilot_wave Feb 15 '17 at 19:55
• Types of radiation is a bit unspecific. Radiation is generally high energy photons, and there were some tests about sending a photon back in time about 2 years ago. physicsworld.com/cws/article/news/2015/feb/05/… and related and written for the layman: scientificamerican.com/article/… That said, if there is a specific name for time traveling radiation (beyond tachyons which have always been kind of silly-theoretical, not real science), I'd be curious to hear it too. Feb 15 '17 at 23:13
• There's also Dr. Ron Mallett's circular light send messages through time theory, which is a fun read but I don't think he's likely to get it working. theepochtimes.com/n3/… Feb 15 '17 at 23:20
• Possibly talking about retarded and advanced potentials? en.wikipedia.org/wiki/Retarded_potential Feb 16 '17 at 0:17
• Now that you mention it Retarded Potential sounds darned close that as well. I'm going to try to dig up more information.
– tmp
Feb 16 '17 at 1:58

Nothing that is known to exist

Relativity does not allow for a massive particle to travel at the speed of light, but it doesn't prevent a particle from travelling faster than light. Such a particle has been called a Tachyon. No such particle has ever been observed. There are good reasons for believing that they don't exist.

Such a particle would be extremely strange. The mass of such a particle would not be positive, it would be imaginary! However you could not use such a particle to send a message to the past. The particles can't be localised, which means that you can't detect them as being "at" a particular place at a particular time.

In conclusion, such particles have never been detected, probably don't exist, and couldn't be used to send messages.

• Thank you! I thought it was a tachyon (I remember hearing the term in Star Trek) but I wasn't sure if that was correct or not.
– tmp
Feb 16 '17 at 1:35
• I'm not convinced a tachyon travels backwards in time. It gets "somewhere" a lot sooner than light does, but, e.g. a 10Xc tachyon still takes 1000 years to go 10 000 light years. (you may convert into Kessel Runs if you like) Feb 16 '17 at 14:09
• @CarlWitthoft That's what I think too, but I've read arguments to the contrary, which I don't understand. Perhaps that's a subject for another question though. theory.uwinnipeg.ca/mod_tech/node142.html Feb 16 '17 at 18:17
• @userLTK you are correct -- depending as always when one talks high speed, on frames of reference. There's no simultaneity and hence all sorts of wacky things can theoretically happen. So in fact I just invented a whole new particle :-) ; one which exceeds $c$ but is immune to special relativity inertial frame rules. Feb 16 '17 at 19:02

One concept of antiparticles (see Feynman) is that they're regular particles travelling backward in time. If you go with that, then by extending the meaning of "radiation" to include physical particles -- which is common usage, e.g. $\alpha$ and $\beta$ particles -- then antiparticles such as positrons came from the future.