In a world that is in chaos politically, socially and environmentally, how can the human race sustain another 100 years?

The human failing I would most like to correct is aggression. It may have had survival advantage in caveman days, to get more food, territory or a partner with whom to reproduce, but now it threatens to destroy us all.

If time travel is possible, where are the tourists from the future?

Scientists tend to risk theories they admire

Although quantum mechanics has been around for nearly 70 years, it is still not generally understood or appreciated, even by those that use it to do calculations.

It is impossible to imagine a four-dimensional space. I personally find it hard enough to visualize a three-dimensional space!

Maybe I'm being a bit harsh on philosophers, but they have not been very kind to me... I have been variously called nominalist, an instrumentalist, a positivist, a realist, and several other ists. The technique seems refutation by denigration: If you can attach a label to my approach, you don't have to say what is wrong with it... I am sure that Einstein, Heisenberg and Dirac didn't worry about whether they were realists or instrumentalists.