If practical time travel is possible some people will get jiggy with the ancestors (dead cert) so there will be kids & not all will go home with daddy (or mommy).
This is gonna leave evidence in the genome, statistically visible markers in our genes too common for when they (should have) evolved or too common in some populations.
So go look for them, if you can't find any time travel isn't.-- Skewed, Mar 30 2018 Multiverse Fiction https://www.scienti...ed-fiction-contest/ [theircompetitor, Mar 30 2018] Primer http://www.imdb.com/title/tt0390384/Completely impractical, obviously. [Wrongfellow, Mar 30 2018] The Algebraist https://en.wikipedi...wiki/The_Algebraist"Time travel" (ish) in more-or-less the form that [8th] describes. [Wrongfellow, Mar 30 2018] Either that or they have more reliable condoms in the future.-- RayfordSteele, Mar 30 2018 ... which are then discovered in a used condition among neolithic grave goods.-- pertinax, Mar 30 2018 Have you ever been to Norfolk, [Skewed]?-- MaxwellBuchanan, Mar 30 2018 Once, but I didn't leave any genetic markers behind, just a couple of high scores on Golden Axe in the arcade.. so whatever you're implying it wasn't me.-- Skewed, Mar 30 2018 //If practical time travel is possible some people will get jiggy with the ancestors (dead cert) ... So go look for them, if you can't find any time travel isn't.//
Why do people assume that time travel can only possibly work in the way it's depicted in the movies? That is, you step into a time machine at the "sending" end, and reappear somewhere/somewhen else without any need of a machine at the "receiving" end.
Everyone knows that, say, telephones don't work like this. Why should we expect time travel to be different?
What if time travel works like telephones, ie you need a machine at the receiving end too? In this case we wouldn't expect to see any time travellers until the first time machine is invented - at which point they'll presumably come pouring out of it the moment it's switched on.-- Wrongfellow, Mar 30 2018 //Why do people assume//
We appear to have a communication problem here, I said "practical" not "impractical".
a) Being able to go somewhere without having to first build the arrival station is a pretty good definition of what I mean by //practical// in this.
b) While having to build something somewhere before you can go there to build the something you need to build before you can go there.. you do see where this goes right?.. well that's a pretty good definition of impractical for me.
So that being so, what was your point again?-- Skewed, Mar 30 2018 So, Neanderthals didn't die out; they just went home.-- FlyingToaster, Mar 30 2018 //So, Neanderthals didn't die out//
"In 2025 with the advent of the new time travel apparatus it was possible for Doctor Winkler to put forth his proposal for a final solution to the Chav problem, they were to be deported en masse to the prehistoric past"
//they just went home//
"Unfortunately they failed to take into account the fact that some Chavs were well educated & having built there own apparatus in the past they return in 2024, join forces with themselves, seize power in a surprise coup & deport everyone else to the really (really) distant past.."
"When the planet was still a ball of molten rock & there was nothing to breath"-- Skewed, Mar 30 2018 No, [Wrong] has a fair point.
Consider:
You send a ship to Alpha Centauri, at an average velocity of 0.1 C.
On arrival, the ship deploys equipment allowing the creation of one end of a stable wormhole.
25 years after departure, the Earth end of the system starts trying to connect to the Centauri end (Think "Stargate").
Once the far end is set up, the connection will succeed, making near-instantaneous travel possible.
Thus it is possible to travel 2.4 years into the "future" of either end of the link, because from an observer's point of view at the "receiving" end, the events that the traveller will have observed locally before departure will not be observable for another 2.4 years.
Any superluminary transport mechanism is therefore "time travel" as it exceeds the velocity of propagation of an event front in normal spacetime.
It is worthwhile considering the Fermi Paradox - "Where are they ?"
If time travel from the future to the past is possible, why haven't already been observed and recorded ?
If time travel from the present to the future is possible, then the question is "Which future ?"-- 8th of 7, Mar 30 2018 //Consider//
Already did & that & what he said is for the purposes of this idea impractical time travel, or at least not what I meant by practical time travel (because it really has no real useful or "practical" application in respect to having any direct meaningful interaction with the past at all does it).
I'm talking Cheese & he's throwing Yogurt in my face, it may have a few lumpy bits but it's not Cheese yet.-- Skewed, Mar 30 2018 I hate my phone. It's so impractical. I wish I could use it to speak to people who don't have one of their own.-- Wrongfellow, Mar 30 2018 Yup, accept of course you have the wrong analogy, I do an idea where I talk about loudhailers (or more specifically, how to prove they don't exist) & you go & complain that I don't know how a mobile phone works, do you begin to see where the mismatch is there ;p-- Skewed, Mar 30 2018 Maybe I've misunderstood your use of the word "practical".
I took it to mean "could potentially be made to work", where you seem to be using it to mean "as seen at the cinema".
//you go & complain that I don't know how a mobile phone works//
I don't remember saying this. Could you please quote the bit where I wrote that you don't understand phones?
In fact, I specifically claimed that everyone knows how phones work; when I wrote "everyone", I intended to include you amongst the set of people I referred to.
Dictionary definitions, you see?-- Wrongfellow, Mar 30 2018 //Dictionary definitions, you see?//
And you think a thing you can only do if you first go somewhere you can't until you've done it is in any way a practical proposition do you?
Yours must be a very strange definition of what practical means then.
//I took it to mean "could potentially be made to work"//
Then you really didn't pay any attention when you were reading the idea did you.
//as seen at the cinema//
If you prefer use that then, popular cultures UFO conspiracy theory style idea of time travel is indeed what I had in mind.
Was the use of the word //Debunking// not a (blindingly obvious) clue to that?-- Skewed, Mar 30 2018 Have you ever watched a film called "Primer"? It's a refreshingly original take on time travel, at least in my opinion.
It works like this:
1. Build a machine.
2. Set a timer which will switch the machine on in, say, 15 minutes. Leave the room.
3. 15 minutes later, the machine switches on and starts to power up. While it's starting up, the door opens and your future self steps out.
4. You and your future self both go about your businesses for a few hours.
5. Later in the day, you enter the room and switch the machine off. While it's shutting down, you climb into it and close the door.
6. While inside the machine, you travel backwards in time and eventually (from your local point of view) emerge from the door in step 3.
This seems somewhat practical to me. It certainly avoids any, dare I say it, "impracticalities" concerning, say, what happens to the air molecules in the volume of space in the past that you're trying to travel to.
(Oh, and could you please quote my claim that you don't understand phones?)-- Wrongfellow, Mar 30 2018 ^ don't be an ass. Rule number 234.
//If time travel from the future to the past is possible, why haven't they already been observed and recorded ?//
^ I added a "they"
What about the babushka lady huh? What about her?She must be totally connected in whatever time she comes from to be able to get a front-row seat to all of the recorded historical crap that the prototype device can reach.
My great great great granddaughter folks.
Let's have a little preemptive round of applause for her paying attention to the old mans' advice shall we.
You go girl!-- 2 fries shy of a happy meal, Mar 30 2018 //a thing you can only do if you first go somewhere you can't until you've done it//
I've travelled here from the past to say that [Wrongfellow] is right.
Suppose that "somewhere" is the future. In that case, you *can* go "somewhere" without first making a time machine. You just need patience and/or the capacity to delegate a task to future generations. Now suppose that "somewhere" is the past. In [Wrongfellow]'s model, you can't go to the past from here. However, if you steal [Wrongfellow]'s secret CAD drawings and build the first time-terminus tomorrow, then people, including your next-week self, will be able to go back in time from next week to tomorrow. They just won't be able to reach today.
It makes perfect sense to me. It just means you can't use this kind of time travel to explore new frontiers or have sex with neanderthals. Similarly, Lewis and Clark couldn't have gone exploring by railway, unless they had limited their explorations to a small area near Merthyr Tydfil where the world's first railway had just started working. That didn't mean railways were impractical. It just meant they weren't a vehicle for geographical pioneering.-- pertinax, Mar 30 2018 // limited their explorations to a small area near Merthyr Tydfil //
... an event with effectively zero probability, since the instant reaction of anyone discovering they are in Merthyr (after they've screamed for a bit, and consumed strong drink) is to immediately explore the options of being somewhere - almost anywhere* - else.
// when I wrote "everyone", I intended to include you amongst the set of people I referred to. //
Is there a "Russell's Paradox !" call, equivalent to "Godwin's Law !" that automatically earns us another USD $5 ?
*outside the Principality of wales, that is.-- 8th of 7, Mar 30 2018 Time-travel proponents seem to forget that traveling through time also necessitates traveling through space, in order to end up at anywhere approximately the same planetary position you were when you left. Otherwise you’d end up in some other position of the galaxy, which itself is in some other location of the universe as it expands, and spacetime itself expands. This is likely to throw off your arrival gate by a few ticks unless you were to establish some kind of stable wormhole between here and there.-- RayfordSteele, Mar 30 2018 //in order to end up at anywhere approximately the same planetary position you were when you left//
Or even on the planet & not floating in space / or inside some inconveniently solid portion of the planet, the possibilities are almost all lethal.-- Skewed, Mar 30 2018 Maybe time travel to the past is possible but the spacetime fabric repairs any and all incongruent patches.-- wjt, Mar 31 2018 Or maybe it's just boringly linear - you can't go back and kill Hitler because obviously you didn't. So if you were waiting outside the beer hall with a brickbat and an attitude, it will turn out your research missed the bit where he stayed on 'til 4am getting hammered with the rest of the putschiliers and a cop came along and you spent the night in jail for loitering with intent.
Not that that doesn't leave room for actual time-meddling. A grad student working on the device could bop back 24hrs, buy a winning lottery ticket for "tomorrow", then go home and watch TV for awhile, emerging after he'd gone back the first time. No problem. Maybe he waved to himself or had a short conversation in passing.
So, first evidence of time travel wouldn't be bodies inside of dinosaurs, nor cell-phone thumbnails, but an improbably high amount of underpaid physics research assistants and mad scientists winning lotteries and horserace bets.-- FlyingToaster, Mar 31 2018 Isn't it weird Lotto draws don't have atomic timestamps on live draws? Maybe it is for this very reason. Time travel effects could be seen on live television.-- wjt, Mar 31 2018 Time travel opponents seem to forget that there's no such thing as an absolute location in space. If your reference frame is Earth (and why not? It's the most mass anywhere nearby) then, whenever you land, you'll land at the same place on Earth.-- notexactly, Apr 01 2018 //location in space// Well, maybe it's not instantaneous transportation, but continuous travel. (This is the one where people are walking backwards)
Example: Say you're on the "front" of the orbiting Earth - sunrise - and you slow down your time rate from 1 to... dunno, say 0.5 (you're not moving backwards yet, just forwards more slowly - to an observer you'd be moving twice as fast), then....
Well, first you'd have to dial it back slooooowly. The Earth orbits the Sun at 29.8 km/s. In the 0.5 frame it's going 15.9 km/s, so you're going to muss up your hair a little as you're suddenly launched vertically at Mach 200 or so. It is, in fact going to take you a little over Ÿhr of just basically floating there in zero-G (unless you're tied to something), slowing the Earth down (subjectively) at 10m/s2, until you can walk around in the 0.5 frame.
(This is why, if you're transitioning to a slower rate you want to be on the leading side of the Earth : on the trailing side, messing up the rate a bit means being hit by a planet.)
Of course, that's assuming gravity is independent of time.
Either way, you might want to bundle up a bit, as any radiant heat source is going to be redshifted, and the ambient (conductive)temperature just went from 26C to -123C or so (not entirely sure that last bit makes sense).
Fun to think about.-- FlyingToaster, Apr 01 2018 random, halfbakery