Back to the Past, Back to the Future, Time Machine, Time Travel, all of those ideas and project dreams of mankind will never happen and extremely impossible for a millions of reasons.
Speed of Light is the vital key role?
No, there is no connection to light speed or a never accelerate at all if those Machines that can travel at a selected time and day, either past or future because we have no evidence to support such claims. People hope and wishing to invent that machine because they want to bring back their loved ones, or they want something that can make them more famous of all, other reasons are greed, or even revenge.
There are no traces in the past during the time of Dinosaurs that they encounter futuristic universal soldiers.
It is wrong to say that those smart people such as Einstein, Jose Rizal, etc…, they all came from the future because they are smarter than standard current humans.
Someone will alter or save the crucifixion of Jesus Christ
Someone will cheat death and early defensive prevention to the cause of death of someone and no deaths through accidents will ever happen.
This simple means that if Time Travel is true, then the world, life and universe, earth will end because everyone turns to be an instant God.
Time Machine to take a note that if this is true and might happened someday for example, then it is only concentrated to a single person against the whole interstellar will change. Now, how about if there are 5,000 available time machines sold in the market and people on earth use them all, what will happen to everything?
To take a note too that even God cannot change the fate of Eve and Adam mistakenly eats the bad apple fruit.
What happened is already done, and the thing that didn’t happen yet cannot be advanced.
If Time Machine is only true then it is favored to only a single person against the multi-verses to edit.
The only Time Traveling Machine that I know that will happen to the futuristic invention is the HIBERNATING MACHINE, and by that, it is intended to a single person and not the whole multi-verses to change.
It is only concentrated to only one person to stagnant his body cells, saved, and re-function to where it pause in the future date and time.