On March 14, 2018, Stephen Hawking died at
the age of 76.
The world has lost an inspiring physicist.
This is a brief companion video as our channel’s
tribute to him.
I’ve seen some rather harsh comments about
his passing on various forums saying that
he wasn’t a particularly brilliant physicist.
By some metrics, that might be correct.
In a poll of who the top physicists of the
20th century were, run in 2009, Hawking did
not even make the top 10.
So, why was he so beloved and is it deserved?
In my mind, there is little doubt that Hawking
was a genius in that he brought together several
different but equally fundamental fields of
physical theory: gravitation, cosmology, quantum
theory, thermodynamics and information theory.
To be able to transcend the boundaries between
those fields is, in itself, inspiring.
Arguably, no one has captured the public’s
eye more than Hawking, even considering folks
like Carl Sagan and Richard Feynman, who also
didn’t make that top 10 list.
The sheer number of tributes peppering the
Internet and even our own Facebook page for
this channel is testament to that.
We hear a lot about his accomplishments and
how impressive they are considering his health
issues, but people tend not to really say
what those accomplishments actually were beyond
“something-something-black-holes”, and
I thought we’d actually delve into what
those were.
Probably most inspiring of all, of course,
is that he did all of his work while suffering
from amyotrophic lateral sclerosis, a form
of motor neuron’s disease, that ultimately
left him paralysed and unable to speak.
His computer-generated voice is probably one
of the most recognizable voices on the planet,
even though it is not truly his voice.
Hawking has been famously wrong on many occasions
in his career and perhaps one of the hallmarks
of the man was his ability to admit when he
was wrong, sometimes involving rather fun
bets with fellow physicists.
Some detractors leap onto these failures saying
that this proves he was not as great as others
make him out to be.
But being wrong is just part of science, particularly
when you work on the edge of known theory,
trying to push our knowledge into the unknown
and probe the secret mysteries of the Universe.
One example of this was when he set out to
prove Jacob Bekenstein wrong.
Bekenstein had a theory that the surface area
of a black hole's event horizon might be a
measure of the black hole's entropy.
Now Hawking objected to this whole notion,
nothing can escape a black hole so it should
effectively have no entropy.
Hawking eventually not only admitted that
Bekenstein was correct, but proved this by
unifying general relativity and quantum theory,
at least near the event horizon of a black
hole, a feat that had never been done before.
Hawking had to admit to being wrong, as every
great scientist must.
In the process however, he created a new understanding
of physics.
To do this, Hawking showed that black holes
emit a very strange kind of energy.
At the event horizon spontaneous particle
pairs are created, as they are everywhere
in the Universe.
These particles are predicted to exist by
quantum theory.
Normally, these particles recombine and wink
out of existence.
Something very different happens at the event
horizon of a black hole, though.
The event horizon is predicted by Einstein’s
theory of general relativity, where nothing
can escape the black hole if it passes through
the event horizon.
If one of these spontaneously created particles
passes through the event horizon and it’s
partner stays in normal space then recombination
is impossible and the short-lived particle
in normal space becomes a long lived one instead,
one that we see as radiation.
Thus the concept of Hawking radiation was
born by Hawking combining relativity and quantum
theory.
His error leads to one of his best known discoveries,
and this is very common in science.
Now some might wonder if Hawking Radiation
is terribly important, though if you’re
a regular to this channel I suspect you know
it is, if not I invite you to watch our episode
on Black Hole Farming sometime, as we discuss
there a way in which civilizations can survive
past the end of the era of stars.
A number of interesting co-developments flow
from his work.
The first is that black holes can and do evaporate
because the energy for the radiation comes
from somewhere and that is from the black
hole itself.
The other thing he showed is that the Hawking
radiation is proportional to the surface gravity
of the black hole, which, for a Schwarzschild
black hole, is inversely proportional to the
mass of the black hole.
So we know that the smaller the black hole,
the more energy it puts out and the faster
it evaporates.
Hawking’s work in this area has played a
large role in supporting future practical
applications.
We have discussed using Hawking radiation
extensively on this channel to extract energy
from black holes in fascinating ways, allowing
us to achieve everything from Kugelblitz black
holes that power interstellar vessels to providing
us with the ability to convert waste heat
back into usable power.
We have also used this radiation to farm black
holes at the end of time.
Without Hawking's’ work, we would not know
of these possibilities.
Another thing Hawking did was to condense
the very esoteric and complex physics of black
hole and Big Bang theory into a readable book
for non-scientists back in 1988, when he authored
A Brief History of Time.
This book became a best-seller and introduced
black holes and the Big Bang to people outside
of the physics community in a way that allowed
the average person to understand it.
For me personally, the ability to take a complex
topic and distill it down to something that
can be understood by people generally is a
hallmark of a great educator, and something
I constantly strive to do on this channel
and I, therefore, list this book as one of
Hawking’s hallmark achievements.
One of my professors once told me that it
was just as important that a scientist to
be able to convey information to others as
to uncover new information, and Hawking proved
to be a master at both.
As an educator, he clearly deserved his position
as the Lucasian Professor of Mathematics at
the University of Cambridge between 1979 and
2009, the same position held by Sir Isaac
Newton back in the 1600s.
Another topic that we often cover on this
channel is the idea of transhumanism, to be
able to transcend the biological bodies we
are currently constrained within as well as
uploading human minds into a computer or other
substrates.
Hawking is a great example of this concept
and his life proved that we are able to use
technology to improve our bodies, overcome
its limitations, and still play a vital role
in the progression of our species.
I find myself in awe of what someone with
his condition achieved in his life, despite
the barriers that would have led many others
to have justifiably decided to give up saying
that they were insurmountable.
I hope I have persuaded you that Hawking was
deserving of the praise that he has received
and of our gratitude and admiration.
He extended human knowledge about the universe
around us and inspired many others to seek
to do the same, and he did it all while struggling
against overwhelming adversity.
For my part, I think that is one heck of an
epitaph and his loss will be keenly felt.
