It would be hard to find a geek who doesn’t recognize the world-famous theoretical physicist Stephen Hawking, who turns 70 today, or his equally famous voice.

Despite being stricken with the neurogenerative disease ALS at age 21, Hawking has continued to do groundbreaking work in quantum gravity, cosmology, and black hole research as well as written iconic popular science books such as A Brief History of Time.

Being forced to use a speech synthesizer — as Hawking has since 1985 due to complications from his disease — would have left hindered most peoples’ ability to communicate. But somehow the computerized voice, and the length of time it takes him to type in his thoughts, lends even more weight to Hawking’s words. Below, we have collected audio of some of his best quotes on topics such as physics, space travel, and the meaning of life, all spoken in his iconic digital voice.

If you’d like to hear more about Hawking, tune in to the live webcast of the University of Cambridge’s special symposium beginning at in honor of his birthday featuring physicists such as Hawking’s close friend Kip Thorne and Nobel laureate Saul Perlmutter at 8 a.m. EST.

“The voice that I use is a very old hardware speech synthesizer, made in 1986. I keep it because I have not heard a voice I like better and because, by now, I have identified with it.” — From a 2006 interview on Israeli television

“A model is a good model if first it interprets a wide range of observations in terms of a simple and elegant model, and second if the model makes definite predictions that can be tested, and possibly falsified, by observation.” – On scientific models from a 2007 lecture in Berkeley

“I think the universe was spontaneously created out of nothing, according to the laws of science. It has no beginning and no end.” – On the origin on the universe, during a 2006 interview on Israeli television

“Observations indicate that the universe is expanding at an ever-increasing rate. It will expand forever, getting emptier and darker. Although the universe doesn’t have an end, it had a beginning in the Big Bang. One might ask what is before that but the answer is that there is nowhere before the Big Bang just as there is nowhere south of the South Pole.” — From at video Q&A with Time magazine in 2010

“The irregularities in the early universe will mean that some regions will have slightly higher density than others. The gravitational attraction of the extra density will slow the expansion of the region and can eventually cause the region to collapse to form galaxies and stars. So look well at this map of the microwave sky. It is the blueprint for all the structure in the universe. We are the product of quantum fluctuations in the very early universe.” — Speaking about the WMAP data, from a 2007 lecture in Berkeley

“If we ever do find a complete theory of the universe, it would be a great triumph of human reason but it wouldn’t leave much for us to do. We need an intellectual challenge.” — During an interview with Charlie Rose in 2008

 ”I am discounting reports of UFOs. Why would they appear only to cranks and weirdos?” — On whether or not we are alone in the universe during his 2008 TED talk

“Our only chance of long-term survival is not to remain lurking on planet Earth, but to spread out into space. The answers to these big questions show that we have made remarkable progress in the last hundred years. But if we want to continue beyond the next hundred years, our future is in space. That is why I am in favor of manned — or should I say, personed — space flight.” — Discussing space travel during his 2008 TED talk

“My daughter, Lucy, knew one of the scriptwriters for the Simpsons. He said he would like to write an episode involving me. I accepted immediately because it would be fun, and because the Simpsons is the best thing on American television.” — Discussing his famous appearance on ‘The Simpsons’

Image: NASA/Paul E. Alers