<p>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.</p>

CC BY-SA 3.0
2017-02-16T14:05:40.470Z
2017-02-16T14:05:40.470Z
Carl Witthoft
<p>Nothing that is known to exist</p>

<p>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 <em>Tachyon</em>. No such particle has ever been observed. There are good reasons for believing that they don't exist.</p>

<p>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. </p>

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

<hr>

<p>read more at <a href="http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/tachyons.html" rel="noreferrer">http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/tachyons.html</a></p>

CC BY-SA 3.0
2017-02-16T01:35:38.943Z
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
CC BY-SA 3.0
2017-02-16T14:09:51.040Z
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)
Carl Witthoft
CC BY-SA 3.0
2017-02-16T18:17:42.457Z
@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.     http://theory.uwinnipeg.ca/mod_tech/node142.html
userLTK
CC BY-SA 3.0
2017-02-16T19:02:32.897Z
@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.
Carl Witthoft
CC BY-SA 3.0
2017-02-15T18:01:54.457Z
2017-02-15T18:01:54.457Z
James K
<p>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.</p>

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

CC BY-SA 3.0
2017-02-15T19:55:17.683Z
A search on retrocausation will get you in deep very quickly: https://www.google.com/search?q=retrocausation&ie=utf-8&oe=utf-8 Quantum pilot waves are also troublesome:https://en.wikipedia.org/wiki/Pilot_wave
Wayfaring Stranger
CC BY-SA 3.0
2017-02-15T23:13:15.933Z
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.   http://physicsworld.com/cws/article/news/2015/feb/05/photons-simulate-time-travel-in-the-lab and related and written for the layman:  https://www.scientificamerican.com/article/time-travel-simulation-resolves-grandfather-paradox/  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.
userLTK
CC BY-SA 3.0
2017-02-15T23:20:38.527Z
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.    http://www.theepochtimes.com/n3/1037968-time-travel-is-possible-how-to-send-a-message-to-the-past/
userLTK
CC BY-SA 3.0
2017-02-16T00:17:39.120Z
Possibly talking about retarded and advanced potentials? https://en.wikipedia.org/wiki/Retarded_potential
AtmosphericPrisonEscape
CC BY-SA 3.0
2017-02-16T01:58:29.133Z
Now that you mention it Retarded Potential sounds darned close that as well. I'm going to try to dig up more information.
tmp
<space-time><radiation>
What Types of Radiation Emanate in the Future and are Perceived in the Present?
tmp
# What Types of Radiation Emanate in the Future and are Perceived in the Present?

(Asked by: username_0 on 2017-02-15)

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.

**Tags:** space-time, radiation

> **Comments:**
> **username_1**: A search on retrocausation will get you in deep very quickly: https://www.google.com/search?q=retrocausation&ie=utf-8&oe=utf-8 Quantum pilot waves are also troublesome:https://en.wikipedia.org/wiki/Pilot_wave  
> **username_2**: 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.   http://physicsworld.com/cws/article/news/2015/feb/05/photons-simulate-time-travel-in-the-lab and related and written for the layman:  https://www.scientificamerican.com/article/time-travel-simulation-resolves-grandfather-paradox/  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.  
> **username_2**: 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.    http://www.theepochtimes.com/n3/1037968-time-travel-is-possible-how-to-send-a-message-to-the-past/  
> **username_3**: Possibly talking about retarded and advanced potentials? https://en.wikipedia.org/wiki/Retarded_potential  
> **username_0**: Now that you mention it Retarded Potential sounds darned close that as well. I'm going to try to dig up more information.  

---

## 2 answers

### Answer by username_4 on 2017-02-16. Score: 2 | Accepted answer

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.


---

### Answer by username_5 on 2017-02-15. Score: 5

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.

---

read more at <http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/tachyons.html>

> **Comments:**
> **username_0**: 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.  
> **username_4**: 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)  
> **username_2**: @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.     http://theory.uwinnipeg.ca/mod_tech/node142.html  
> **username_4**: @username_2 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.  

---

