# Tachyons and tachyon guns **URL:** \ **Category:** Factual Questions\ **Created:** [October 8, 2002, 1:30pm UTC](https://boards.straightdope.com/t/tachyons-and-tachyon-guns/131350 "2002-10-08T13:30:22Z")\ **Posts on this page:** 16\ **Page:** 2
**Author:** ![Malacandra](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@Malacandra](https://boards.straightdope.com/u/Malacandra)\ **Post date:** [March 6, 2011, 9:37am UTC](https://boards.straightdope.com/t/tachyons-and-tachyon-guns/131350/21 "2011-03-06T09:37:12Z")
A tachyon gun could kill you so dead you’d be instantly zombified. ---
**Author:** ![Tal\_Shipman](https://avatars.discourse-cdn.com/v4/letter/t/58f4c7/32.png) [@Tal\_Shipman](https://boards.straightdope.com/u/Tal_Shipman)\ **Post date:** [March 6, 2011, 10:26am UTC](https://boards.straightdope.com/t/tachyons-and-tachyon-guns/131350/22 "2011-03-06T10:26:59Z")
i understand that and thank you but i want to know why they can not interact with normal matter ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [March 6, 2011, 8:18pm UTC](https://boards.straightdope.com/t/tachyons-and-tachyon-guns/131350/23 "2011-03-06T20:18:05Z")
I’d have to double-check the math, but I think that any interaction between a tachyon and a normal particle would end up violating conservation of energy and/or momentum. ---
**Author:** ![Yumblie](https://avatars.discourse-cdn.com/v4/letter/y/76d3ee/32.png) [@Yumblie](https://boards.straightdope.com/u/Yumblie)\ **Post date:** [March 6, 2011, 9:09pm UTC](https://boards.straightdope.com/t/tachyons-and-tachyon-guns/131350/24 "2011-03-06T21:09:31Z")
If tachyons existed in nature, then something would have to emit them. The problem is that tachyons have negative energy, so the process of a particle emitting a tachyon would cause it to gain energy. Let’s say you had some particle T that could emit tachyons. T emits a tachyon, and now T has more energy than it started with. Since T will never run out of energy, T could keep on emitting tachyons indefinitely, and increase its energy without limit. Since we don’t see anything with infinite energy out there, it’s a good indication that if tachyons could possibly exist, there’s no natural process that could form them. And as far as we can tell, at the atomic level there’s nothing humans are capable of that isn’t already done in nature. So if you had a tachyon gun, it would have infinite ammo, but you could only fire it so many times before it overheated and exploded. ---
**Author:** ![Tal\_Shipman](https://avatars.discourse-cdn.com/v4/letter/t/58f4c7/32.png) [@Tal\_Shipman](https://boards.straightdope.com/u/Tal_Shipman)\ **Post date:** [March 6, 2011, 11:45pm UTC](https://boards.straightdope.com/t/tachyons-and-tachyon-guns/131350/25 "2011-03-06T23:45:30Z")
Thank you for explaining yumblie. ---
**Author:** ![Nobody](https://avatars.discourse-cdn.com/v4/letter/n/94ad74/32.png) [@Nobody](https://boards.straightdope.com/u/Nobody)\ **Post date:** [March 7, 2011, 1:51am UTC](https://boards.straightdope.com/t/tachyons-and-tachyon-guns/131350/26 "2011-03-07T01:51:26Z")
Years ago (maybe even back in the 90’s) I read about an event that points to the possibility of Tachyons existing. However, I have not heard anything else about it and I can’t find it on Google, so maybe it was nothing after all. I hope that someone else here has heard of this, even if it did turn out to be bunk. The best I can remember, at a supercollider some energy, maybe even particles, was briefly detected before the supercollider was ran, and one of the theories was that the collision of particles created tachyons which, traveling faster than the speed of light, went back in time and that is what was detected. Now, it’s been a long time, and I have a very bad memory so I’m sure I’m not remembering everything correctly and getting details wrong, but if anybody knows what I’m talking about, or has heard anything similar I would be interested in hearing about it. Thank you. ---
**Author:** ![Ring](https://avatars.discourse-cdn.com/v4/letter/r/6a8cbe/32.png) [@Ring](https://boards.straightdope.com/u/Ring)\ **Post date:** [March 7, 2011, 2:58am UTC](https://boards.straightdope.com/t/tachyons-and-tachyon-guns/131350/27 "2011-03-07T02:58:52Z")
Let me know when you’re going to load the gun with the tachyon bullets. I’d love to see that. I hope you have quick fingers. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [March 7, 2011, 3:07am UTC](https://boards.straightdope.com/t/tachyons-and-tachyon-guns/131350/28 "2011-03-07T03:07:20Z")
> [@](#): > > The best I can remember, at a supercollider some energy, maybe even particles, was briefly detected before the supercollider was ran, and one of the theories was that the collision of particles created tachyons which, traveling faster than the speed of light, went back in time and that is what was detected. It seems like a news story about some purported FTL effect or another crops up every year. They usually turn out to be misinterpretations by the reporter, and sometimes are bunk on the part of the researchers, but never amount to anything. I couldn’t tell you which one you’re vaguely remembering to say which case it was, but it definitely wasn’t FTL. ---
**Author:** ![Ring](https://avatars.discourse-cdn.com/v4/letter/r/6a8cbe/32.png) [@Ring](https://boards.straightdope.com/u/Ring)\ **Post date:** [March 7, 2011, 3:57am UTC](https://boards.straightdope.com/t/tachyons-and-tachyon-guns/131350/29 "2011-03-07T03:57:36Z")
Now that I think about it it seems that it would require two reference frames before you actually communicate into the past. Let’s say that 2 duelists, **A** and **B** , start walking away from each other at close to the speed of light. Now, let’s say **A** fires his tachyon gun when his clock reads 8 secs and hits **B** when **B** ’s clock reads 4 secs. **A** measures this to occur in his future and **B** measures it to occur in his present. But if **B** now shoots **A** with his tachyon gun he’ll hit **A** before **A** fired. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [March 7, 2011, 4:11am UTC](https://boards.straightdope.com/t/tachyons-and-tachyon-guns/131350/30 "2011-03-07T04:11:01Z")
And then, of course, you’re getting into the grandfather paradox, which shouldn’t be a surprise when talking about time-travel effects. ---
**Author:** ![Nathan\_E.Zephyr](https://avatars.discourse-cdn.com/v4/letter/n/dc4da7/32.png) [@Nathan\_E.Zephyr](https://boards.straightdope.com/u/Nathan_E.Zephyr)\ **Post date:** [March 7, 2011, 4:55am UTC](https://boards.straightdope.com/t/tachyons-and-tachyon-guns/131350/31 "2011-03-07T04:55:54Z")
> [@Der\_Trihs](#): > > Could a tachyon gun shoot this thread when it was first posted in 2002? No, you have it backwards…this thread first began in 2011. The 2002 posts appeared afterwards. ---
**Author:** ![Sunspace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sunspace/32/1250_2.png) [@Sunspace](https://boards.straightdope.com/u/Sunspace)\ **Post date:** [March 7, 2011, 5:07am UTC](https://boards.straightdope.com/t/tachyons-and-tachyon-guns/131350/32 "2011-03-07T05:07:48Z")
Waitaminnit! Where do you get that tachyons have negative energy? ---
**Author:** ![Mosier](https://avatars.discourse-cdn.com/v4/letter/m/7ea924/32.png) [@Mosier](https://boards.straightdope.com/u/Mosier)\ **Post date:** [March 7, 2011, 5:18am UTC](https://boards.straightdope.com/t/tachyons-and-tachyon-guns/131350/33 "2011-03-07T05:18:16Z")
> [@Chronos](#): > > Quoth **caveman** :Location isn’t relevant, only velocity. It’s not just a matter of “dead before you see the shooter’s trigger finger move”, it’d be “dead before the trigger finger moves at all”. Why? If i shoot a light gun at someone one light second away, they are dead 1 second after I pull the trigger. If I shoot a tachyon gun at someone one light second away, they are dead 1/2 a second after I pull the trigger. What am I missing? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [March 7, 2011, 6:24am UTC](https://boards.straightdope.com/t/tachyons-and-tachyon-guns/131350/34 "2011-03-07T06:24:10Z")
If you can arrange things such that something’s moving faster than the speed of light, then you can also arrange things such that it’s going back in time. ---
**Author:** ![Yumblie](https://avatars.discourse-cdn.com/v4/letter/y/76d3ee/32.png) [@Yumblie](https://boards.straightdope.com/u/Yumblie)\ **Post date:** [March 7, 2011, 6:38am UTC](https://boards.straightdope.com/t/tachyons-and-tachyon-guns/131350/35 "2011-03-07T06:38:31Z")
> [@Sunspace](#): > > Waitaminnit! Where do you get that tachyons have negative energy? The thing to keep in mind about tachyons is that they’re made up particles, so really they can have any properties we want them to have, until we actually find a real one. The energy of a particle is given by _mc_/Sqrt(1-_v_[sup]2[/sup]/_c_[sup]2[/sup]). When the ratio of _v_/_c_ is greater than one, the square root becomes negative, and you get an imaginary number. Energy can’t be imaginary, so the only way to resolve this is to make _m_ also imaginary. And so tachyons apparently have an imaginary rest mass. That might seem ridiculous, but in relativity, the only frames of reference in which physics works properly are frames that are moving at less than _c_. And so, there is no such thing as a valid rest frame for a tachyon, so we can hand wave away the imaginary mass problem. Another fun “fact” about tachyons is that they lose energy as they speed up, so the lowest energy state for a tachyon is when it’s going at infinite speed. ---
**Author:** ![Nobody](https://avatars.discourse-cdn.com/v4/letter/n/94ad74/32.png) [@Nobody](https://boards.straightdope.com/u/Nobody)\ **Post date:** [March 7, 2011, 7:21am UTC](https://boards.straightdope.com/t/tachyons-and-tachyon-guns/131350/36 "2011-03-07T07:21:27Z")
Thank you **Chronos**. Too bad I can’t remember more. Out of curiosity I Googled “time travel ftl” and the first link is [this](http://sheol.org/throopw/tachyon-pistols.html). This goes over the dueling tachyon pistols scenario and explains it in easy to follow terms. [Previous page](https://boards.straightdope.com/t/tachyons-and-tachyon-guns/131350.md?page=1)