I have to admit that I haven't heard of this. Some antidepressants stimulate appetite and a lot of the food we eat can be sweet things. This packs an energy punch which may cause you to stay awake. Other than that, I have to say that I'm as mystified as your doctor on this one!

We think that conditions on the early Earth were very bad for life as there was no atmosphere. Mars might have been a better place to live at that time, and so life could have started there but we just don't know. To find out if life really did get going on Mars, we need to go there and have a look.

You need to travel at 11 metres per second to escape form Earth's gravity. It is much harder to blow things off the Earth than it is Mars, although it is potentially possible to go from Earth to Mars. Humans might even be doing it accidentally when we send satellites up into space: sometimes they get hit with things and things like paint might flake off. However, once above the atmosphere, everything we send up is sterilised by radiation. And space scientists do as much as they can to prevent space becoming contaminated.

Anything is possible. There are a number of theories about how we can travel through time but they usually involve going into the future using the theory of relativity. Essentially, this involves going so fast that your body clock slows down. When you stop moving so quickly, everything around you will have aged but you will be only a little bit older. In this way, you are able to travel into the future. Another method that has been suggested is to go to a black hole and go out the other end of it. Stephen Hawking doesn't believe time travel is possible because we would have seen people from the future if it were true. A lot of equations in physics don't work backwards, so going back in time seems unlikely. It would be very difficult.

I think it is very unlikely. The energy needed to cause something like a tsunami is huge, and to make the world fall apart it would need to be even bigger. It might be possible to cause a tsunami if a bomb was planted in a particular place and the Earth's plates moved. This would require considerable planning, so a tsunami shouldn't be caused by bomb testing, unless it was many times bigger than Hiroshima and Nagasaki.

It's an interesting question! I suggest you go along to Michio's talk at Naked Science on Tuesday and find out!