I would expunge the word "aptitude" from our vocabulary, because if you're interested in something, that's all that matters. You'll spend more time doing it, that than anything else, and possibly more time doing it than anybody else. And that's all that matters, because in the end, if you love what you do, you'll be your best at it compared to anything else you might have chosen as a career.

Some memories are best absorbed through your eyes in real time, even if you have no record of it later. Because then you can access that memory and how you felt in that moment. If you're looking at your cellphone screen, taking a video of something that is otherwise unforgettable, watching it later will not recover the emotion you would have had, had you witnessed it directly.

Essentially every scientist, when posed with the question, "If you want to get science knowledge from Mars, do you want to send a geologist or do you want to send a robot?" Well, the real answer is, you can send 100 robots for the price of sending one geologist, so let's send 100 robots to 100 different locations, and then we would all benefit. So that's the answer you would get. And I agree with that answer.

The universe is so amazing and so limitless, who wouldn't want to study the universe?

Private enterprise can never lead a space frontier. It's not possible because a space frontier is expensive, it has unknown risks and it has unquantified risks.

We already know the limits of Einstein's theories. From the centers of black holes at the very beginning of the universe - we call these singularities - Einstein's equations fail. In fact, people have joked that's where God is dividing by zero.

A supernova is one of the most powerful explosions in the universe. It's so luminous, it can be seen across billions of light years. It releases as much energy in an instant as our sun will produce over its 10-billion-year lifetime.