Progress is the only path to improvement.
Sometimes to move ahead you have to leave things behind.
Live today like it's tomorrow and you'll always be ahead.
Onward and upward, never look back.
If you don't like where you've ended up, try doing something else.
If you never jump to your death you'll never learn how to fly.
What's the point of a light bulb if I already have candles that light my house just fine?
Every time you think, stop and ask yourself: could I have thought better?
Common sense is nothing but the inability to see all possibilities and the naïveté still to assume that one is correct.
Taking one path often means missing out on another.
A path may not be right or wrong. It may just be different.
Failing to succeed does not mean failing to progress.
The choice doesn't matter if the outcome is the same.
Remove failure from your options and you will always succeed.
The universe is probably littered with the one-planet graves of cultures which made the sensible economic decision that there's no good reason to go into space - each discovered, studied, and remembered by the ones who made the irrational decision.
Victory at all costs, victory in spite of all terror, victory however long and hard the road may be; for without victory, there is no survival.
History will be kind to me, for I intend to write it.
The future is a lovely place, for that's how I intend to make it.
It is no use saying, 'We are doing our best.' You have got to succeed in doing what is necessary. Do or do not; there is no try.
Never, never, never give up.
Courage is not the absence of fear; it is the ability to act in the presence of fear.
If aliens did visit us, I’d be embarrassed to tell them we still dig fossil fuels from the ground as a source of energy.
I never want you to quote me citing my authority as a scientist for your knowing something. If that's what you have to resort to I have failed as an educator.
Creativity is seeing what everyone else sees, but then thinking a new thought that has never been thought before and expressing it somehow.
Science is a cooperative enterprise, spanning the generations. It's the passing of a torch from teacher, to student, to teacher. A community of minds reaching back to antiquity and forward to the stars.
I know of no time in human history where ignorance was better than knowledge.
Part of what it is to be scientifically-literate, it's not simply, 'Do you know what DNA is? Or what the Big Bang is?' That's an aspect of science literacy. The biggest part of it is do you know how to think about information that's presented in front of you.