Question: It is said that we could, theoretically speaking, travel into the future. However, if in say, 50 years time someone was to build a time machine, why would they not be able to travel back to the present time (their past) and teach us how to build one?

Helen Johnson answered on 19 Nov 2014:

We think that time can only ever run forwards 🙁 Your time can slow down compared to other people’s if you are moving really close to the speed of light, or if you’re really close to a black hole/in some very strong gravitational field, but don’t think it can ever go backwards. In theory, if you were on Earth and someone was up in Space near a black hole with a huge, huge clock that you could see with a telescope – their clock would appear to be ticking slowly. I love the idea of time travel though.. it’s definitely great for movies!