Until his death at age 76 earlier this week Stephen Hawking was among the world’s most famous living scientists. He was an astrophysicist and held Cambridge University’s Lucasian Professorship of Mathematics, a position previously held by Isaac Newton.

Dr. Hawking developed ALS when he was 21 which confined him to a wheelchair for nearly the past 55 years. ALS usually kills its victims within 2 – 10 years. How did he live for 55 years with this condition? Dr. Jeffrey Elliott, chief of the neuromuscular disorders at the University of Texas Southwestern Medical Center speculated: “I think part of his longevity may have been because he had a slowly progressive form. Probably it was also due to the exclusive nursing and medical care that he received.” He was tended around the clock by a team of nurses.  Other than Hawking’s disability, for what exactly was he famous?

To the non-scientist he likely is best known for his 1988 book “A Brief History of Time” which was an explanation for laypeople of many aspects of cosmology.  It is the best selling cosmology book in history, has sold more than 10 million copies and was on bestseller lists for more than four years.  It’s a great read and was updated with a co-author in 2003 to reflect interim discoveries.

Scientifically, his most prominent achievement is his discovery of “Hawking Radiation”.  Hawking Radiation concerns black holes.  As you may be aware, black holes are areas of immense gravity, likely created by an extremely dense body of mass, which, classically, were thought to have so much gravitational pull that nothing could escape – not even pure energy such as light, x-rays, radiation, etc.  But due to Hawking’s discovery we know that “Black holes are not actually black. Instead, these gravitational sinks are thought to emit radiation that causes them to shrink and eventually disappear.”*This was Hawking’s great discovery over 40 years ago and it changed our understanding of the universe.

What Stephen Hawking did was to apply quantum mechanics, which concerns subatomic physics, to black holes.  He theorized, mathematically, that at a black hole’s event horizon (the area in spacetime where the gravity becomes so great that light/information can’t escape and an observer can’t see what is happening beyond that point) quantum reactions would actually cause a black hole to emit some radiation.  As discussed in previous IFODs, quantum mechanics is pretty weird stuff and basically says that everything around us, even in the vacuum of space, is abuzz and all sorts of particles are jumping around.  Particles pop in and out of existence and their locations can’t necessarily be determined with accuracy.  But, there is symmetry. Positive particles have negative counterparts somewhere.  Regular particles have anti-particles.  Using quantum theory, Dr. Hawking theorized that at the event horizon some particles that fell into a black hole would emit anti-particles outside of the black hole and some anti-particles falling into the black hole would emit particles outside of the black hole.  Thus, to an observer, the black hole would appear to be emitting particles (radiation).  Part of his theory states that black holes smaller than a certain size would actually emit more radiation (particles) than they absorb.  So, very small or micro black holes should have very short lives.  There has been some success by scientists in the past few years in confirming Hawking Radiation through experiments.

*quote from Nature.com