I actually do know how to build a machine to travel through time and space. Oddly enough, the way it works is totally in accord with generally accepted physics theories even though people often say -- incorrectly -- that time travel is not possible in physics. The basic idea is simple in theory. Build a spacecraft with a particle accelerator for a propulsion system. This can accelerate the spacecraft to a significant percentage of the speed of light. According to relativity theory, this would cause occupants of the spacecraft to experience less passage of time than on Earth. They would, in effect, time travel to the future. This could involve traveling hundreds of years into the future. There are three issues with this. First, it would be very expensive to build because it has to be in space. Second, traveling to the future seems clearly possible, but my idea on how to travel to the past is somewhat more controversial so it might be a one-way trip. Third, I'm not sure relativity theory is actually correct. Nobody will listen to me, but there is an error in the definition of energy used by physicists and it is relevant to the theory of relativity.