Every effort under compulsion demands a sacrifice of energy. I never paid such a price.

No rocket will reach the moon save by a miraculous discovery of an explosive far more energetic than any known. And even if the requisite fuel were produced, it would still have to be shown that the rocket machine would operate at 459 degrees below zero-the temperature of interplanetary space.

When I get an idea I start at once building it up in my imagination. I change the construction, make improvements and operate the device in my mind. It is absolutely immaterial to me whether I run my turbine in my thought or test it in my shop. I even note if it is out of balance.

My brain is only a receiver, in the Universe

The desire that guides me in all I do is the desire to harness the forces of nature to the service of mankind.

What one man calls God, another calls the laws of physics.

I do not think you can name many great inventions that have been made by married men.