The laws of physics state that "matter can neither be created nor destroyed" but in this movie they go back and add matter (themselves and the ship) to the Universe in 1986. How does that work?
"Knowledge is cheap at any price"
They revised the laws of physics in the future to allow for that.
shareThey also removed matter from the universe.
"Oh no...they sent the wrong Spock!"
They removed matter from the Universe in the future. All the atoms the ship and the crew were composed of (in the future) existed in 1986 but hadn't been formed into the ship/crew yet. So when they went back they took the same atoms back to a Universe where they already existed.This added - "created" - matter to the Universe.
"Knowledge is cheap at any price"
If (contrary to the theory of general relativity) you're thinking of 1986 as its own universe, then that "universe" isn't a closed system and the law of conservation of mass-energy doesn't apply; the law doesn't say no mass can come in to a system from the outside.
If you're thinking of all of spacetime as a single universe, then it is closed (as far as we know), but no mass is being added to it or taken away by time travel. Removing matter from the "future" and taking it to the "past" is no more significant than removing it from one room and taking it to another.
The latter is bjlevine's point.
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Lazy + smart = efficient.
Time is simply a method of describing change as compared relative to a system of standard units which we call "hours, minutes and seconds".If you could freeze every subatomic particle in the Universe into its current position then if it started moving again there would be no way to measure how 'long' it had been static.If you think of every atom as having its own unique identifying marker, then by going back in time you are are moving atom 'X' from 2324 to 1986 where atom 'X' already exists. This is not only adding matter to the Universe at a given point in time but identical matter to that which already exists?
If you wished to go back in time to 1986 then the only way you could do that would be to rearrange every subatomic particle into the exact position, trajectory and speed it was on a given date and time in 1986.
"Knowledge is cheap at any price"
And of course if you set the controls of your time portal to materialise yourself 'where I am now 30 years ago' you would probably appear in outer space since the Earth orbits the Sun and 'where you are now' was thousands of miles away 30 years ago.
"Knowledge is cheap at any price"
It was thousands of miles away a mere thirty seconds ago, and over 31,000,000 times farther way 30 years ago.
share"The laws of physics state that "matter can neither be created nor destroyed" but in this movie they go back and add matter (themselves and the ship) to the Universe in 1986. How does that work?"
the concept of time travel implies that the dimension of time is considered to be analogous to the dimensions of space. A different time is considered to be similar to a different place. Therefor, if time travel is possible, moving mass or energy from one time to another dos not violate conservation laws any more than moving mass or energy from one place to another does. As seen from outside space/time,the mass of the universes remains constant.