When President Barack Obama nominated the Christian geneticist Francis Collins to head the National Institutes of Health in 2009, some American scientists questioned whether someone who professed a strong belief in God was qualified to lead the largest biomedical research agency in the world.
This argument -- that scientific inquiry is essentially incompatible with religious belief -- has been gaining traction in some circles in recent years. In fact, according to a 2009 Pew Research Center survey, American scientists are about half as likely as the general public to believe in God or a higher, universal power. Still, the survey found that the percentage of scientists that believe in some form of a deity or power was higher than you may think -- 51 percent.
Scientists throughout history have relied on data and observations to make sense of the world. But there are still some really big questions about the universe that science can't easily explain: Where did matter come from? What is consciousness? And what makes us human?
“Where did matter come from? What is consciousness? And what makes us human?”
In the past, this quest for understanding has given scientists both past and present plenty of opportunities for experiencing wonder and awe. That's because at their core, both science and religion require some kind of leap of faith -- whether it's belief in multiverses or belief in a personal God.
In chronological order, here's a glimpse into what some of the world's greatest scientists thought about the possibility of a higher power.

Writing to the Grand Duchess Christina of Tuscany, Galileo criticized philosophers of his time who blindly valued Biblical authority over scientific evidence.
"I do not feel obliged to believe that the same God who has endowed us with senses, reason and intellect has intended us to forego their use and by some other means to give us knowledge which we can attain by them. He would not require us to deny sense and reason in physical matters which are set before our eyes and minds by direct experience or necessary demonstrations."

In an essay on atheism, Bacon wrote:
"God never wrought miracle to convince atheism, because his ordinary works convince it. It is true, that a little philosophy inclineth man’s mind to atheism; but depth in philosophy bringeth men’s minds about to religion. For while the mind of man looketh upon second causes scattered, it may sometimes rest in them, and go no further; but when it beholdeth the chain of them, confederate and linked together, it must needs fly to Providence and Deity."

In an 1873 letter to Dutch writer Nicolaas Dirk Doedes, Darwin wrote:
"I may say that the impossibility of conceiving that this grand and wondrous universe, with our conscious selves, arose through chance, seems to me the chief argument for the existence of God; but whether this is an argument of real value, I have never been able to decide. I am aware that if we admit a first cause, the mind still craves to know whence it came and how it arose. Nor can I overlook the difficulty from the immense amount of suffering through the world. I am, also, induced to defer to a certain extent to the judgment of the many able men who have fully believed in God; but here again I see how poor an argument this is. The safest conclusion seems to be that the whole subject is beyond the scope of man's intellect; but man can do his duty."

After hearing a minister preach about the dangers of science, Mitchell wrote:
"Scientific investigations, pushed on and on, will reveal new ways in which God works, and bring us deeper revelations of the wholly unknown."

She is quoted as saying:
"Nothing in life is to be feared, it is only to be understood. Now is the time to understand more, so that we may fear less."

In a 1954 essay for NPR, Einstein wrote:
"The most beautiful thing we can experience is the Mysterious — the knowledge of the existence of something unfathomable to us, the manifestation of the most profound reason coupled with the most brilliant beauty. I cannot imagine a God who rewards and punishes the objects of his creation, or who has a will of the kind we experience in ourselves. I am satisfied with the mystery of life's eternity and with the awareness of — and glimpse into — the marvelous construction of the existing world together with the steadfast determination to comprehend a portion, be it ever so tiny, of the reason that manifests itself in nature. This is the basics of cosmic religiosity, and it appears to me that the most important function of art and science is to awaken this feeling among the receptive and keep it alive."

When her father accused her of making science her religion, Franklin told him that she had a different definition of faith:
"In my view, all that is necessary for faith is the belief that by doing our best we shall come nearer to success and that success in our aims (the improvement of the lot of mankind, present and future) is worth attaining. Anyone able to believe in all that religion implies obviously must have such faith, but I maintain that faith in this world is perfectly possible without faith in another world...I see no reason to believe that a creator of protoplasm or primeval matter, if such there be, has any reason to be interested in our insignificant race in a tiny corner of the universe, and still less in us, as still more insignificant individuals."

In his book, The Demon-Haunted World: Science as a Candle in the Dark, Sagan writes:
"Science is not only compatible with spirituality; it is a profound source of spirituality. When we recognize our place in an immensity of light years and in the passage of ages, when we grasp the intricacy, beauty and subtlety of life, then that soaring feeling, that sense of elation and humility combined, is surely spiritual."

In an interview with the Spanish newspaper El Mundo, Hawking said:
"Before we understood science, it was natural to believe that God created the universe, but now science offers a more convincing explanation."

In an interview with the Hindustan Times, he said:
"There is no scientific basis for how movement of planets and stars can influence our fate. There is no reason for time of birth to influence events years later. The predictions made are either obvious or shown to be random ... A culture based on superstitions will do worse than one based on scientific knowledge and rational thoughts.”

In Death By Black Hole, a collection of science essays, Tyson writes:
"So you're made of detritus [from exploded stars]. Get over it. Or better yet, celebrate it. After all, what nobler thought can one cherish than that the universe lives within us all?"

In an essay for CNN, Collins writes:
"I have found there is a wonderful harmony in the complementary truths of science and faith. The God of the Bible is also the God of the genome. God can be found in the cathedral or in the laboratory. By investigating God's majestic and awesome creation, science can actually be a means of worship."
CORRECTION: A previous version of this story stated incorrectly that Francis Collins was born in 1960. He was born in 1950.
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