"There is one alternative to dark matter, and that is the assumption that Newton's laws don't hold over distances as great as galaxies. But we know that Newton's laws hold over a very large domain. And virtually one hundred percent of the physics and astronomy community believes that there is matter in the universe that does not radiate."

“It is well known that I am available twenty-four hours a day to women astronomers.”

“Science progresses best when observations force us to alter our preconceptions.”

“I'm not a theologian, and I must say honestly that Vatican astronomers' views are entirely in accord with ours. I'm not aware of any Church positions that contradict modern science. In my own life, my science and my religion are separate. I'm Jewish, and so religion to me is a kind of moral code and a kind of history. I try to do my science in a moral way, and, I believe that, ideally, science should be looked upon as something that helps us understand our role in the universe.”

“We have peered into a new world and have seen that it is more mysterious and more complex than we had imagined. Still more mysteries of the universe remain hidden. Their discovery awaits the adventurous scientists of the future. I like it this way.”

“Science is competitive, aggressive, demanding. It is also imaginative, inspiring, uplifting.”

“How stars move tell us that most matter in the universe is dark. When we see stars in the sky, we're only seeing five or 10 percent of the matter that there is in the universe.”