jon horvat:  What do you think of harnessing the power of the heat hidden beneath the surface of the Earth? Is this the future of power? Australia has some projects like this, similar to something I thought of when studying Stirling engines. 

Dr. Kaku: Geothermal power is a definite possibility for the future. However, not every area of the world is suitable for geothermal plants. I personally believe that we will need an energy mix for the future. Unfortunately, oil is quite convenient and is packed with energy and is extremely difficult to replace. Therefore, I think we should investigate all possible avenues to fuel our post-petroleum era. Some people claim that we will always discover new deposits of oil. However, we will have to discover a new Saudi Arabia every 10 years to meet the energy demand of China and India and the rest of the world. That is impossible. Therefore, we are forced to look for every possible avenue for energy, including geothermal power.

Rhaomi:  Do you think humanity will ever be able to expand beyond Earth, to other planets or other star systems?

Dr. Kaku: Yes. However, it will be more expensive than most people realize. To put a pound of anything into near orbit around the Earth costs $10,000 per pound. That is the cost of gold. Imagine John Glenn made out of solid gold, and you know the cost of putting John Glenn into orbit. Imagine all the astronauts made out of solid gold, including their spaceships, and then you understand why each shuttle mission costs half a billion dollars. To go to the moon would require several hundred thousand dollars per pound. To go to Mars would require several million dollars per pound. The space elevator, if it can be created, might reduce costs by a factor of 1000, making outer space accessible for the first time in history. But nobody knows for sure if we can create a space elevator. I personally believe that in the future we should become a 2-planet species. We should inhabit the Earth and another spare planet in case we botch up one of them. But this is centuries away. To terraform Mars would require hundreds of years of Martian exploration. So the colonization of outer space, I think, is inevitable but is centuries to millennia away.