Time travel. - General - Facepunch Forum

ITT - people who don't use the words theoretically or hypothetically nearly often enough. ITT also lots of blowhards who have listened to science wanting science fiction to be true and cherrypicked the bits that get them excited.

[QUOTE=mikfoz;29450767]ITT - people who don't use the words theoretically or hypothetically nearly often enough. ITT also lots of blowhards who have listened to science wanting science fiction to be true and cherrypicked the bits that get them excited.[/QUOTE] He lives!

It's pretty much safe to say that we'll never achieve some stable method of travelling backward or forward in time for the next 1,000+ years, so stop bringing it up because it always comes to the same conclusion: [b]it's impossible[/b]

[QUOTE=JohnnyMo1;29436599]There are a bunch of ways to define it. Resistance to acceleration due to some force, and the amount to which an object curves spacetime are the two that come to mind.[/QUOTE] Yeah, that would work, but the definition of 1kg mass in SI units is a comparison to the kilgoram-prototype in Paris. This might change soon when we get a new definition of Avogadro's constant based on the research of the guys at the PTB (Physikalisch Technische Bundesanstalt) in Brunswick. There, they have a pure Si-28 sphere of 1 kg (the purity is quite extraordinary and due to the Silicon-industry easy to achieve. Still it costs a lot. A few $1.000.000 if I'm remembering correctly). It's surface is polished and with the help of xray-interferometry on that crystal they can count the amount of atoms (and therefore redefine Avogadro's constant and therefore the kg).

[QUOTE=aVoN;29452365]Yeah, that would work, but the definition of 1kg mass in SI units is a comparison to the kilgoram-prototype in Paris. This might change soon when we get a new definition of Avogadro's constant based on the research of the guys at the PTB (Physikalisch Technische Bundesanstalt) in Brunswick. There, they have a pure Si-28 sphere of 1 kg (the purity is quite extraordinary and due to the Silicon-industry easy to achieve. Still it costs a lot. A few $1.000.000 if I'm remembering correctly). It's surface is polished and with the help of xray-interferometry on that crystal they can count the amount of atoms (and therefore redefine Avogadro's constant and therefore the kg).[/QUOTE] I think he meant mass in a more abstract sense.

[QUOTE=Sorin;29451534]It's pretty much safe to say that we'll never achieve some stable method of travelling backward or forward in time for the next 1,000+ years, so stop bringing it up because it always comes to the same conclusion: [b]it's impossible[/b][/QUOTE] Erm.... Accelerate near light speed, decelerate (breaks symmetry as the acceleration), go back to earth -> Twin paradox: You just went forward in time. Also we are "travelling" forward in time all the time. And who are you to say it's impossible. With the words of GlaDDoS: "You're not a scientist. You're not a doctor. You're not even a full-time employee" (Well, the last one might be wrong but anyway. Leave that discussion and it's outcome to real scientists or go study physics just to find out that there is nothing which forbids time-travel per se) [editline]26th April 2011[/editline] [QUOTE=DainBramageStudios;29452421]I think he meant mass in a more abstract sense.[/QUOTE] "Mass is the property of an object to counter-react to a force" if you take Newton's way. So he was already right. I'm too much involved to metrology (not meteorology!!!!), which is about measuring stuff quite accurate :)

aVoN, I love you.

[QUOTE=aVoN;29419931]Energy must be a real quantity. If you go to speeds above the speed of light, [img_thumb]http://math.daggeringcats.com/?E=\frac{m c^2}{\sqrt{1 - \frac{v^2}{c^2}}[/img_thumb] becomes an imaginary quantity. But if the mass also were imaginary then the energy becomes real again [img_thumb]http://math.daggeringcats.com/?i^2 = -1[/img_thumb]. But those particles (e.g. Tachyons) can't cross the speed-of-light border to get "slower". Still this is just a hypothetical consideration concerning the math and no evidences for Tachyons have been found yet. [editline]25th April 2011[/editline] Even with a warp-drive or wormhole, you are locally always below the speed of light. Still you can reach other regions of space within a short period of time you'd otherwise had needed FTL speeds for. That's why some people refer to those types of travel (incorrectly) as FTL. But it has been quite a convention so get along with that :)[/QUOTE] Something I've always wondered is: why must energy be a real quantity? Why can't mass be the one that has to be the real quantity, and energy imaginary? I mean, neither really makes much sense in the end. Neither one seems more logical over the other, because in the end you're still talking about an imaginary number.

Someone be cool and explain the wormhole thing better and I'll update the OP.

This topic greatly interests me. Please, continue your discussions.

Just so you all know, I've already perfected time travel. In fact, I traveled several seconds into the future just typing this post! [editline]27th April 2011[/editline] I do have a serious question however. Technically speaking, aren't we all in our own very specific time frames? Think about it for a second. You are all at different locations of varying heights and distances. With that said, time as we define it, isn't technically time at all. At least, not the time the universe is based on. Perhaps I should explain my sudden thought further (I'm sick at the moment). Isn't there, technically speaking, some what of an official, universal clock that all things exist by. That in all technicality defeats my previous paragraph as then that would mean that everything is in sync with one another. And so, we all travel through time the exact same way as everything else in the universe, and cannot ultimately escape times grasp? Maybe it's the cough medicine talking... [editline]27th April 2011[/editline] Personally I'd believe my first statement about everyone being in their own time frames. Each particle is in it's own specific location, no matter how precise and we are all made up of billions of particles as well as everything else in the universe. So maybe time isn't relative to the person, exactly, but instead relative to the thing it effects.

When you look at the sun aren't you looking back in time like 10 seconds or something?

[QUOTE=killover;29459877]When you look at the sun aren't you looking back in time like 10 seconds or something?[/QUOTE] 8 Minutes I believe actually. [editline]27th April 2011[/editline] Same thing for when you're looking at your girlfriend. She's already a fraction of a second in the past. Not to mention it also takes a fraction of a second for your brain to translate what your eyes see.

Traveling into the past is basically impossible. In every-which-way. What has happened has happened, and there's no returning to a previous time in one location once time has elapsed. The only way I could imagine that wormhole theory working is if the location you came out at was at a point in space that was arrived upon faster from your destination than it would take for light to travel there. Once again, this is (currently) scientifically impossible. Even if you did slip through a hole that made this possible, relativity would compensate by slowing your perception of time as you were traveling (or speed it up, idk this is a mind-fuck). One way to try and imagine backwards time travel would be a gun that fires a bullet faster then the speed of light. The bullet would hit you before you saw the gun go off; proving that it all depends on your perspective. However traveling into the future is definitely possible! It's only relative to you. For example, one traveling into the future, by whatever means, would be observed for say 100 years but the traveler would only experience, say, 10 years of aging. The laws of nature compensate for one's speed and location in the bending space-time fabric by speeding or slowing their apparent age to outside observers. It's all relative when it comes down to it.

[QUOTE=Sorin;29451534]It's pretty much safe to say that we'll never achieve some stable method of travelling backward or forward in time for the next 1,000+ years, so stop bringing it up because it always comes to the same conclusion: [b]it's impossible[/b][/QUOTE] Yeah but it's a great literary device and if you're the sort of person for whom science fiction is a major way of figuring out the universe from inside your bedroom you can't help thinking "what if" then convincing yourself it "should" be true then using lots of special pleading and half-understood headline science to bolster the wishful thinking. [editline]27th April 2011[/editline] [QUOTE=killover;29459877]When you look at the sun aren't you looking back in time like 10 seconds or something?[/QUOTE] No. No you're not. The light that hits your retina started its journey 8.3 minutes ago. That's not time travel, it's space travel. The light travelled in space which takes time.

The real question is what if you travel faster than light with car headlights turned on. Would you see the light fly back or would it all accumulate and show up after you've gone under the speed of light.

*Suddenly realises he is reasoning with people who have made their minds up* *Bangs head on wall* [editline]27th April 2011[/editline] [QUOTE=Enginn;29460316]The real question is what if you travel faster than light with car headlights turned on. Would you see the light fly back or would it all accumulate and show up after you've gone under the speed of light.[/QUOTE] No. [editline]27th April 2011[/editline] *repeats head banging process*

[QUOTE=mikfoz;29460318]*Suddenly realises he is reasoning with people who have made their minds up* *Bangs head on wall* [editline]27th April 2011[/editline] No. [editline]27th April 2011[/editline] *repeats head banging process*[/QUOTE] And my job is done here, thank you for participating in this Aperture Science computer-aided enrichment activity. Goodbye.

Nerds.

[QUOTE=sltungle;29457628]Something I've always wondered is: why must energy be a real quantity? Why can't mass be the one that has to be the real quantity, and energy imaginary? I mean, neither really makes much sense in the end. Neither one seems more logical over the other, because in the end you're still talking about an imaginary number.[/QUOTE] Well, I can't find a better explanation right now but if you take velocity also into account which is linked to energy, it would cause an imaginary velocity for an imaginary energy. And that can't be real. But there must be some more about it. [editline]27th April 2011[/editline] [QUOTE=Kydoes;29460273]Traveling into the past is basically impossible. In every-which-way. What has happened has happened, and there's no returning to a previous time in one location once time has elapsed.[/QUOTE] This is a philosophical point of you and just ONE philosophical point of you. The math of general relativity does not forbid time-travel at all. [QUOTE=Kydoes;29460273]The only way I could imagine that wormhole theory working is if the location you came out at was at a point in space that was arrived upon faster from your destination than it would take for light to travel there.[/QUOTE] If you have a wormhole and take one end of it through a trip in ship which accelerates to near light-speed, decelerates down, turns and accelerates to light speed again to come back to you (and then decelerates again) there will be a time-difference between both "ends". A travel through the wormhole will be equivalent to a time-travel then. [QUOTE=Kydoes;29460273]Once again, this is (currently) scientifically impossible. Even if you did slip through a hole that made this possible, relativity would compensate by slowing your perception of time as you were traveling (or speed it up, idk this is a mind-fuck).[/QUOTE] It's not scientifically impossible. Actually General Relativity is flooded with tons of different ways to time-travel. [QUOTE=Kydoes;29460273]One way to try and imagine backwards time travel would be a gun that fires a bullet faster th[b]e[/b]n the speed of light. The bullet would hit you before you saw the gun go off; proving that it all depends on your perspective. [/QUOTE] Nothing with a real mass can travel faster th[b]a[/b]n the speed of light. [editline]27th April 2011[/editline] [QUOTE=Enginn;29460316]The real question is what if you travel faster than light with car headlights turned on. Would you see the light fly back or would it all accumulate and show up after you've gone under the speed of light.[/QUOTE] You can't do that, starfox

[QUOTE=aVoN;29461365]Well, I can't find a better explanation right now but if you take velocity also into account which is linked to energy, it would cause an imaginary velocity for an imaginary energy. And that can't be real. But there must be some more about it.[/QUOTE] But then that'd lead me to ask: why is imaginary mass more sensible than imaginary velocity, or distance for that matter? In the end none of them really make any sense whatsoever.

ITT: Facepunchers pretend to know shit about physics. What's with all the time travel threads that show up in GD? It's almost always the exact same discussion.

[QUOTE=DONUT KING;29462994]ITT: Facepunchers pretend to know shit about physics. What's with all the time travel threads that show up in GD? It's almost always the exact same discussion.[/QUOTE] There is actually a secret cabal designed to troll stlungle and avon with a litany of silly physics questions.

[QUOTE=Contag;29463053]There is actually a secret cabal designed to troll stlungle and avon with a litany of silly physics questions.[/QUOTE] Wait, why do I have to be involved in this? I don't like being conspired against :frown:

[QUOTE=sltungle;29463064]Wait, why do I have to be involved in this? I don't like being conspired against :frown:[/QUOTE] That's what happens when you decided to physics. Look at Einstein - he decided to become a physicist, and [B]bam[/B] world war.

Time travel is really cool imo, but it would bring fatal consequences!

[QUOTE=sltungle;29461502]But then that'd lead me to ask: why is imaginary mass more sensible than imaginary velocity, or distance for that matter? In the end none of them really make any sense whatsoever.[/QUOTE] In terms of special relativity, you make one assumption: that causality is preserved. The fact that imaginary mass leads to a velocity greater than c violates this assumption. You can disregard it. It actually takes an understanding of quantum field theory in order to make tachyons causally preserving. Basically there is a way to show that tachyons cannot transmit information faster than light and this is enough to show that backwards time travel is not possible.

[QUOTE=deboutonner;29463771]In terms of special relativity, you make one assumption: that causality is preserved. The fact that imaginary mass leads to a velocity greater than c violates this assumption. You can disregard it. It actually takes an understanding of quantum field theory in order to make tachyons causally preserving. Basically there is a way to show that tachyons cannot transmit information faster than light and this is enough to show that backwards time travel is not possible.[/QUOTE] I don't think you read my question. The question was, when coming up with the idea of the tachyon why was energy chosen to be the physical quantity that was held real? Why was mass the chosen quantity to become imaginary? Why could you not hold mass as the real quantity and simply say 'imaginary energy would be needed for these particles to exist'?

[QUOTE=sltungle;29464423]I don't think you read my question. The question was, when coming up with the idea of the tachyon why was energy chosen to be the physical quantity that was held real? Why was mass the chosen quantity to become imaginary? Why could you not hold mass as the real quantity and simply say 'imaginary energy would be needed for these particles to exist'?[/QUOTE] It is how the maths works out. E^2 = p^2 + m^2. If the mass is real, then the energy must be real by this relationship. If the mass is imaginary, then the energy is real.

... well what if the mass was √i kg?