If the Law of the Conservation of Mass is correct, than additional mass cannot simply be added to the universe at any random time without it having to lose an equivalent amount of mass (or energy) at the same time.
Speculations about time travel suggest we can take a 185 pound person and send him back hundreds of years. Wouldn't this cause the universe to lose 185 lbs of mass in our time while gaining it (seemingly from out of nowhere) at another time.
Time travel would make the mass of the universe variable, unstable and unpredictable at any given time.
Doesn't the Law of the Conservation of Mass eliminate the possibility of time travel?
There's no law of conservation of mass; there's the fact that global Lorentz invariance-that implies that mass is globally defined-implies that closed time-like curves can't exist. However there's a bit more to it-cf. https://www.its.caltech.edu/~kip/index.html/PubScans/II-121.pdf
Dear Stephen,
There is no law of conservation of mass and the conservation of energy is for a 4-dimensional universe, moving an object to the past would be the same as moving it upstairs. Energy is conserved
There is conservation of total energy. Alone this should not restrict going back in time. Things like entropy will spoil things.
Time travel if possible requires enough energy to make up any difference in mass that might occur. Even so there are exclusion rules that place limitations on what can be done in time travel. Richard Feynman argued that antimatter is like ordinary matter except going backward in time.
The question ignores a scenario in which mass is exchanged with some other time period.
Mass and energy are not conserved in GR transformations if different observers detect different order in sequences of events.
In other work years ago I found representations in which conventional equations of energy and momentum predict rest mass to decrease if light speed increases in acceleration all as measured by a traveler.
Albert Einstein in his equation 107 of speeches in Princeton 1921 requires light speed to decrease locally in a gravity field. People argue. Max Born agreed with Einstein. Peter Bergmann disagreed, arguing the decrease was only apparent from flat space, but not while Einstein was living. By equivalence the equation can be applied to any acceleration, applying Lagrangian to predict local light speed to increase in kinetic acceleration.
Even longer ago I found representations predicting that excess acceleration could cause high speed vehicles traveling close to light speed to undergo time reversal, resulting in engines burned out trying to decelerate. Travelers in a vehicle lost far from home, backward in time, with electrical fire in the engines resembles the wheelworks flying machine in the opening chapters in Ezekiel, rescued by a better flying machine and used as object lesson.
In more conventional science uncertainty allows a difference in energy for a brief time, combined with time dilation of a fast moving vehicle. Also there is the long time delay for information to cross the universe, giving doubt to conservation rules on that scale.
In answer, no. A mass balance on a large scale does not appear able to prevent time travel on small scale.
Dear Stephen Martin Fritz,
Greetings, Travel in time requires the conversion between mass and energy!
Regards, Saeed
Time travel to the past is theoretically possible in certain general relativity spacetime geometries that permit traveling faster than the speed of light, such as cosmic strings, traversable wormholes, and Alcubierre drives
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