I finished reading Three Roads to Quantum Gravity (2001), by Lee Smolin, a theoretical physicist whose general sensibility I’ve always appreciated. I don’t always agree with his ideas, but I like the thoughtful way he expresses them. Smolin brings some philosophical thinking to his physics.
While he added a lengthy Postscript to the 2017 edition, the book is outdated both by time and by Smolin. In 2006 he published The Trouble with Physics: The Rise of String Theory, the Fall of a Science, and What Comes Next, which explored issues in the practice of theoretical physics. But in 2001 he still thought string theory was (at least part of) The Answer.
Almost none of which is the subject of this post.
Last time I started talking about entropy and a puzzle it presents in cosmology. To understand the puzzle we have to understand entropy, which is a crucial part of our view of physics. In fact, we consider entropy to be a (statistical) law about the behavior of reality. That law says: Entropy always increases.
There are some nuances to this, though. For example we can decrease entropy in a system by expending energy. But expending that energy increases the entropy in some other system. Overall, entropy does always increase.
This time we’ll see how Roger Penrose, in his 2010 book Cycles of Time, addresses the puzzle entropy creates in cosmology.
We interrupt this regularly scheduled blog post for an Important Weather Update! Afterwards, please stay tuned for News From Space!
It took almost exactly 100 years. In 1905, über-geek hero Albert Einstein presented four papers of major significance to the world. One of those was about Special Relativity. It took Einstein ten more years to figure out the General theory of Relativity. He presented that work in November of 1915.
One of the predictions of General Relativity is that gravity warps space, creating gravity waves (which move at the speed of light). And while many other predictions of GR have been tested and confirmed (to very high precision), we’ve never quite managed to detect gravity waves.
Until September 14th of 2015!