2017 is an auspicious year in physics because we are 100 years on from 1917, the year physics found its mojo. So here’s a question: How has our understanding of the universe changed in the last century, and what did that change signify?
Well, we know a lot more, right? We’ve burrowed right down into the atom and peered into the early universe and the very beginnings of time. Yes! But in some ways we know a lot less than we did 100 years ago. Let me explain…
In 1917:
Physics is unified. Physicists quite reasonably assert that we are wrapping-up our physical knowledge of the Universe. They’re feeling a little smug about it too, having done all the hard work. There are just a few 't's to cross and 'i's to dot for the next generations of physicists. Nothing more to see, move along.
The laws of thermodynamics are well understood, mapped out by Planck, Maxwell, Boltzmann, Gibbs, et al.
Electromagnetic theory has been established by Maxwell, Gauss, Faraday, etc.
Light has been properly described by wave theory.
Ernest Rutherford has established the notion of radioactive half-life and has created a useful model of an atom with a nucleus, and in our annus mirabilus, 1917, he splits that atom.
Einstein has presented his paper on Special Relativity (1905) which threw a cat among the pigeons by predicting matter-energy equivalence and unifying space and time, an audacious development on sacred Newton (perhaps it was the same cat that was mischievously grabbed by Erwin Schrödinger and stuffed in a box?). He has also published General Relativity in 1915 but it isn’t until 1917 that Einstein applies his theory to the universe as a whole, kickstarting the new field of relativistic cosmology.
In 1912 Vesto Slipher has measured the first Doppler redshift to create a few ripples but the conventional notion is that the universe is in an eternal static state. Later on, in a particularly delicious irony, the Big Bang Theory is first proposed by a Roman Catholic Priest, Georges Lemaître (1927), but we’re getting ahead of ourselves.
If you had to sum up the state of knowledge in physics leading up to 1917, it would be that (to quote Ed Hillary) “We knocked the bastard off!” Champagne was on the table, the corks were out.
In 2017:
Physics has long since bifurcated into Astrophysics and Quantum Mechanics. Attempts to reunite them invoke multidimensional acrobatics like M-theory (to unify the superstring models) and Loop Quantum Gravity. We still wait to see if astrophysics and QM can actually be reunified by a provable esoteric uber-theory.
The Universe is expanding from a Big Bang creation event 13.75 billion years ago. We are shuffling around the cooling detritus of this event.
Quantum Mechanics is a portal into a new physics that departs from classical physics at the subatomic level. It describes the interactions of energy and matter in counterintuitive ways. The two major interpretations of QM are equally absurd (yet strangely beautiful)—Copenhagen and Many Worlds Theory. Whichever, we are superimposed beings.
Light and other particles have a dual particle/wave nature.
Most of the Universe is now composed of unknown stuff: Dark Energy and Dark Matter, leaving just 4 percent over as stuff we have the vaguest clue about or tangible theories for.
And…
...the Universe is a pretty scary place again, filled with monsters and titans: Black Holes, Quasars, Gamma-Ray Bursters. Our maps again carry an inscription around the edges: There be dragons. We’ve gone from thinking that we know most of the answers, to knowing we don't know very many at all. If nothing else, that span of 100 years has taught science how to eat humble pie!
