# Sending particles back in time - what are this guy's chance? **URL:** \ **Category:** Factual Questions\ **Created:** [December 9, 2003, 6:56am UTC](https://boards.straightdope.com/t/sending-particles-back-in-time-what-are-this-guys-chance/217873 "2003-12-09T06:56:53Z")\ **Posts on this page:** 5\ **Page:** 3
**Author:** ![Agent\_Foxtrot](https://avatars.discourse-cdn.com/v4/letter/a/9fc29f/32.png) [@Agent\_Foxtrot](https://boards.straightdope.com/u/Agent_Foxtrot)\ **Post date:** [December 11, 2003, 8:07pm UTC](https://boards.straightdope.com/t/sending-particles-back-in-time-what-are-this-guys-chance/217873/41 "2003-12-11T20:07:06Z")
> [@](#): > > \*Originally posted by DarrenS \* > \*\*Hijacking my own thread a little - > > When speaking of time travel, people often make a big deal of the “grandfather paradox” - whereby I travel back in time and kill my own grandfather, thereby negating my existence. > > How about the even weirder (IMO) situation of being able to meet myself at a past or future time?! \*\* I’ve thought about this a bit. You can’t simply “negate” your existence if the Law of Conservation of Matter and Energy holds true. What I propose is this: If you go back to kill your grandfather, a number of things can happen: 1. Some sort of obsticle can get in your way preventing you from killing him (your gun jamming, a car hitting you right before you pull the trigger, etc.), 2. The man you killed turns out not to be your real blood grandfather (funny, grandma did speak very fondly of the milkman…), 3. An unforseen series of events occurs that enables you to still be born (it turns out you were adopted), 4. You kill him, but are transported to another timeline where he is still alive (the bastard just won’t die!). Far-fetched? Perhaps, but it satisfies any arguments of paradoxy you can come up with. -FoamFighter ---
**Author:** ![Agent\_Foxtrot](https://avatars.discourse-cdn.com/v4/letter/a/9fc29f/32.png) [@Agent\_Foxtrot](https://boards.straightdope.com/u/Agent_Foxtrot)\ **Post date:** [December 11, 2003, 8:07pm UTC](https://boards.straightdope.com/t/sending-particles-back-in-time-what-are-this-guys-chance/217873/42 "2003-12-11T20:07:19Z")
> [@](#): > > \*Originally posted by DarrenS \* > \*\*Hijacking my own thread a little - > > When speaking of time travel, people often make a big deal of the “grandfather paradox” - whereby I travel back in time and kill my own grandfather, thereby negating my existence. > > How about the even weirder (IMO) situation of being able to meet myself at a past or future time?! \*\* I’ve thought about this a bit. You can’t simply “negate” your existence if the Law of Conservation of Matter and Energy holds true. What I propose is this: If you go back to kill your grandfather, a number of things can happen: 1. Some sort of obsticle can get in your way preventing you from killing him (your gun jamming, a car hitting you right before you pull the trigger, etc.), 2. The man you killed turns out not to be your real blood grandfather (funny, grandma did speak very fondly of the milkman…), 3. An unforseen series of events occurs that enables you to still be born (it turns out you were adopted), 4. You kill him, but are transported to another timeline where he is still alive (the bastard just won’t die!). Far-fetched? Perhaps, but it refutes any arguments of paradoxy you can come up with. -FoamFighter ---
**Author:** ![Agent\_Foxtrot](https://avatars.discourse-cdn.com/v4/letter/a/9fc29f/32.png) [@Agent\_Foxtrot](https://boards.straightdope.com/u/Agent_Foxtrot)\ **Post date:** [December 11, 2003, 8:29pm UTC](https://boards.straightdope.com/t/sending-particles-back-in-time-what-are-this-guys-chance/217873/43 "2003-12-11T20:29:25Z")
Oh, by the way, it is my personal theory that you can’t possibly meet yourself, because more than one of you can’t exist per timeline. This is sort of gravy on the meat of my last argument: You can go back and kill your grandfather, but it doesn’t matter, because you will never be born in that timeline anyway! - FoamFighter ---
**Author:** ![toadspittle](https://avatars.discourse-cdn.com/v4/letter/t/c0e974/32.png) [@toadspittle](https://boards.straightdope.com/u/toadspittle)\ **Post date:** [December 11, 2003, 8:42pm UTC](https://boards.straightdope.com/t/sending-particles-back-in-time-what-are-this-guys-chance/217873/44 "2003-12-11T20:42:01Z")
> [@](#): > > \*Originally posted by cgrayce \* > \*\* > What most people seem to mean by “time travel” is: there exists some interface between me and the rest of the world – the window of my spaceship, the boundary around my time machine, et cetera – and, when I look at things inside this boundary, e.g. at myself, my body processes, heart beating and lungs breathing, thought sequences and so forth, I observe causality: in brief, effects follow causes. However, when I look at things outside this boundary, e.g. at the birds flying by, the aging of other people, trees, stars, et cetera, I observe inverse causality: effects precede causes, or at least, the order of “cause” and “effect” I observe inside the interface is reversed outside the interface. This is not time travel. This is running time backwards. There’s no reason the traveler must observe time running backwards–she could simply appear at a point in the past, without experiencing any intervening passage. > [@](#): > > But this is nuts. However the universe works, it cannot operate by one set of rules on one side of a “window” and by a set by definition contradictory on the other, and still allow me to “look” out the “window.” \*\* The universe hasn’t proved itself to make a lot of sense so far. Space that expands so fast that galacies are receding faster than the speed of light? Cosmic sinkholes from which nothing can escape? Time slowing down the faster you travel? A “vacuum”–which, by definition, means that it contains nothing–that is, in fact, a boiling sea of energy that is continually producing “virtual” particles from nothing? Uncertainty itself being an inherent property of all matter? Siz or seven dimensions we can’t even see? 95% of the matter and energy that makes up the universe being completely unobservable? Why should the universe stop being nuts now? ---
**Author:** ![Agent\_Foxtrot](https://avatars.discourse-cdn.com/v4/letter/a/9fc29f/32.png) [@Agent\_Foxtrot](https://boards.straightdope.com/u/Agent_Foxtrot)\ **Post date:** [December 11, 2003, 8:46pm UTC](https://boards.straightdope.com/t/sending-particles-back-in-time-what-are-this-guys-chance/217873/45 "2003-12-11T20:46:29Z")
Err, let me restate: More than one of you can’t exist at the same point in the timeline. There. Also, **bauble** mentioned time travel as a method of space travel. If you were at the vernal equinox and went back to the autumnal equinox, why wouldn’t you find yourself at the exact same point in space? (And literally, in space, above the earth’s atmosphere!) -FoamFighter P.S. - Sorry for the multiple posts. There’s so much I want to comment on with everyone’s great ideas, but I think it’s time to let someone else talk now. 🙂 [Previous page](https://boards.straightdope.com/t/sending-particles-back-in-time-what-are-this-guys-chance/217873.md?page=2)