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Help me with SCIENCE!
Kamar
Registered User regular
Registered User regular
Okay, this thread is going to go all over the place. I'm working on some worldbuilding stuff for my novels but there are a few real-world concepts I need some help with and digging them out of Wiki is like pulling teeth. And I'll also toss in something that's unrelated to my worldbuilding but has been bugging me.
First up is time travel(to the past). Is there any kind of consensus on the most likely outcome? Multiple timelines, paradoxes make everything explode, paradoxes are impossible (all time travel has already occurred, i.e. closed loop)?
Related, FTL travel. Anyone up for a layman explanation of relativity? I've seen discussions about it many times, but I still can't quite comprehend how FTL equals time travel. Is it something I'm not understanding about the nature of light?
And the bonus, what exactly is meant by observation when related to physics? You always see metaphors and the like that are based on observation by something living, like a human, but that doesn't seem to make sense. Is it even possible for something to exist 'unobserved' outside of theory?
Oh, and try not to simplify to the point of heavy inaccuracy, that won't help much - with some jumping off points I can probably work things out with outside resources.
And thanks in advance, I know explaining some of this will be a pain!
First up is time travel(to the past). Is there any kind of consensus on the most likely outcome? Multiple timelines, paradoxes make everything explode, paradoxes are impossible (all time travel has already occurred, i.e. closed loop)?
Related, FTL travel. Anyone up for a layman explanation of relativity? I've seen discussions about it many times, but I still can't quite comprehend how FTL equals time travel. Is it something I'm not understanding about the nature of light?
And the bonus, what exactly is meant by observation when related to physics? You always see metaphors and the like that are based on observation by something living, like a human, but that doesn't seem to make sense. Is it even possible for something to exist 'unobserved' outside of theory?
Oh, and try not to simplify to the point of heavy inaccuracy, that won't help much - with some jumping off points I can probably work things out with outside resources.
And thanks in advance, I know explaining some of this will be a pain!
Kamar on
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(1) Accurate
(2) Understandable without a science background
For example, here's what is designed to be a relatively basic introduction to time machines, written to leave the physics out of it and just deal with the outcomes and so on. I should perhaps specify that it's also meant to be correct and logically consistent, which is not what you'll get with something that doesn't give you a headache immediately.
Same deal with the FTL and the observation stuff. To get it into words that will make sense to someone who doesn't have the requisite knowledge is to drop the concepts that make it anything other than science fiction.
Basically my advice is to not worry about it. Time travel is immensely complicated even without worrying if it could even exist. Neither Back to the Future (time travel about as simple as it gets) nor Primer (you can watch it 10 times and not get what's going on) require any of the understanding you're looking to get. Any time travel stuff or FTL stuff or "observation" stuff at the level of specificity and truth you're looking for is going to be way over your reader's head. Just think about it like this: if you can't understand it without reading a bunch of background stuff, they won't understand it either.
Make up what you want to make up. If you were writing hard sci-fi about space travel or whatever, there's at least enough we know and enough relation to our lives to make it worthwhile to investigate what actually works and to make sure thing sound plausible, but time travel is so ridiculously out there that the difference between well researched, well written time travel in fiction and well written time travel in fiction is going to be nil.
Finally, if you wish to persist, the article I linked and everything it cites are a good place to start for time travel. Your question about observation might be answered by this unless you're talking about the kind of observations that collapse the quantum waveform or whatever in which case you could start here. I'm linking philosophical arguments because they avoid the physics. As for FTL, it's impossible according to our theories, so it doesn't equal time travel in any real sense. At least, that's what I think. You could try reading through some of the articles cited in the above links to get your head around that one.
If the philosophy makes you antsy, those articles typically have links to the actual physics ones too, so you can go there. If you want something simpler, well, like I said, I'm guessing it's not really going to be right.
I found an interesting article that postulated someone could be their own father, grandfather, mother, grandmother, daughter, son, granddaughter, and grandson. It was long and comlpicated, and involved a sex change (I am so not making this up) and it was proposed sometime in the 60s, I think.
The other issue with traveling backward in time is that you would have to calculate for astronomical drift, traveling even only a second back in time might put you out in pluto's orbit, with the speed that the earth, solar system, and milky way travel through space.
Relativity, breaking it down - the speed at which you travel through time is relative to your speed. So, if you were to travel at light speed for only 1 year, your friends on earth would have aged 50 years or so. The faster you go, the slower you travel through time. There is really no way around this problem. Think of it this way. If you were sitting on a space ship, looking backwards from it as it accelerated - say there's a clock behind the ship. As your speed approached the speed of light, if you could still see the hands on the clock, they would seem to slow down. The faster your ship travels, the slower the light is able to bring the information to you, and the hands seem to move even slower. Even though back at the clock, the hands are in the right place for the time, to you, they are going very slow, until they stop when you reach light speed. Now, with that in mind, if you were to travel faster than light, you would go back in time. Both of which Einstein says are impossible.
Now, there's this nifty train of thought that says you could put one end of a wormhole generator on a space ship, and send it out in to the universe, and have it come back at near light speed. The ship would arrive back at earth hundreds of years in the future. But you kept the other end of this wormhole on earth the entire time, and can now step through the wormhole, end up in the future and do whatever you wanted. You could then step back through the wormhole, and be back in the past. (Isn't dimensional physics fun?)
As far as observation goes- What I think your talking about is the Heisenberg uncertainty principle, the rule that you can know what a particle is doing, or where it is, but not both. You cannot know location and direction. The reason for this is that the simple act of observing the particle has changed it fundamentally. For instance, if you want to measure the amount of energy an engine generates, you need to hook it up to something, whatever you hook it up to will impart resistance, and render the results invalid. In everyday life, this has almost no effect, and we can trust the results. But when you're dealing with sub-atomic particles, the effect is quite immense. The instruments will always impart an effect on the particle, and change it. Star Trek dealt with this by inserting a "Heisenberg Compensator" in their teleporters. No bullshit.
Yes, things can exist unobserved. They both exist, and do not exist at the same time. (ala Shrodinger's cat)
The best sci-fi stories ignore most of that - people are willing to accept any multitude of FTL and time travel BS explanations.
EDIT: this is the paradox I was talking about. Its worth a read.
-Current W.I.P.
Currently, theres no reason to believe that time travel to the past is possible. Basically, causality, the principle that events can only affect things that happen after them, is one of the fundamental tenets of physical law. If you break that, all sorts of things start breaking. It might be possible to wrangle together some convoluted theory that allows for closed time loops or whatever, but thats kind of like inventing reasons why Santa Clause exists. We can't prove them to be false, but its overwhelmingly likely that time travel (to the past) is impossible.
The faster you go, the slower time goes for you compared to everyone else. As you approach the speed of light, your time approaches a standstill. This is basically special relativity in a nutshell. As it turns out, if you could go *faster* than the speed of light, some people will observe you reaching your destination before you left from your starting point. This, again, violates causality, which is a big no-no.
Of course, the whole point is moot, because you can't even reach the speed of light in the first place. The closer you get towards light speed, the more energy required to go even a little bit faster. It turns out, that you need infinite energy for anything with mass to reach the speed of light.
I assume you are referring to observations in quantum mechanics. Probably a better word than "observation" would be 'measurement'. But words in physics often mean slightly different things than they do in everyday language. In quantum mechanics, a measurement is anything that forces a particle/wave to take on a definite value. Take, for example, an electron. Quantum mechanics states that until you measure the electron, all you can possibly know about it is basically the probability of where it will be at any given time. But, when you measure it, you "force" the electron to take a definite position. That is what is meant by observation.
Now, that doesn't mean that there is anyone necessarily around to watch it happen, or to record the position of the electron. There are lots of things, like light passing through a polarizing filter, that count as measurements or observations. There doesn't necessarily need to be someone living to observe it.
GT: Tanky the Tank
Black: 1377 6749 7425
Usually stories that involve FTL travel involve the bending of space. Warp drive, for instance, involves the warping of gravity around you to propel yourself forward. You can think of it similar to how wormholes could bend space. If you're writing a story, get creative.
Most good stories don't really base themselves into science non-fiction for a reason.
If you're into some fun "what if's" concerning FTL travel using conventional (ie non-space bendy) methods, Joe Haldeman's "The Forever War" deals with it.
Someones already said it, but the faster (and typically) farther you go, the more quickly time outside the vessel is passing.
Ender's Game also has an interesting 'twist' with it of sorts. Spoilered just in case...
It doesn't matter how you get there. If you suddenly appear at a place faster than light can travel it, you are breaking causality.
GT: Tanky the Tank
Black: 1377 6749 7425
Assuming for the moment that wormholes exist, and objects can pass through them without being destroyed, if you can travel through a wormhole, so can light, and quite a bit faster than you. Causality restored?
In response to wormholes, that makes things a bit more tricky, but no, it does not necessarily mean causality is broken. One thing that is nice about wormholes is that they are hopefully defined well enough to say that the entrance time and place somehow corresponds with the exit time and place, meaning that two-way FTL in one reference frame doesn't imply two-way FTL in all reference frames (which is what breaks causality). If your universe has any number of wormholes, as long as it is impossible to start at the entrance of any one wormhole and end up at that same entrance before you started, causality is not broken.
Also note that when I say FTL, you aren't actually going FTL because light is also traveling through the worm hole. Situations like wormholes don't necessarily violate causality, but they do imply a seriously warped space-time. (Space-time is flat in special relativity and gravity is the only thing we know of that warps it)