From a physics standpoint, time travel is entirely possible, according to an article in Cosmos Magazine. All you need is a really fast space ship and knowledge of Einstein’s Theory of Special Relativity. Financially, however, it’s still totally unviable.
Theoretically, if a person were to orbit the Earth at 161,556 miles per second for one full year, during the same time, two years would have passed on Earth. * That would mean the person would have traveled a year into the future. The problem is that to travel that fast for that long would require about 30 trillion gigajoules (GJ) of kinetic energy. At over $9 per GJ, the bill would total around $27 trillion. So for Back to the Future to become a reality, Marty McFly would have to be a very rich man.
* Correction: The speed was originally identified in miles per hour. It has been corrected to read miles per second.