> Lee Smolin (author of The Trouble With Physics[1]) lamented that your career in physics is essentially dead unless you went into string theory, and pursuing quantum gravity could lead to conflict with pro-string peers.

Famously, yes. But although that may have been true to a first approximation, it ignores the fact that alternatives have never been completely taboo.

The primary one in recent decades was Loop Quantum Gravity, and the related Spin Foams that my friend John Baez worked on for many years.

> https://en.wikipedia.org/wiki/Loop_quantum_gravity

LQG hasn't won the day, I'm just mentioning that it was an alternative to String Theory that didn't ruin careers.

The motls blog claims that Smolin made provable mathematical errors in his book. Do you disagree?

I cannot speak to the mathematical errors, but I recommend you take most of what Motl says with a grain of salt. He is well known in the physics and mathematics community for a variety of interesting statements, including my personal favorite: "Discrete math is just a disorganized mess of random statements." http://www.scottaaronson.com/blog/?p=1720 Which is interesting, because I have yet to see a construction of continuous mathematics that didn't start with something discrete.

Motl is an infamous pain, and makes enemies at the drop of the hat, and is extremely scornful and overly negative -- but he's also intelligent and knows mathematical physics.

I would disregard his unsupported opinions out of hand without thinking twice, but not his supported arguments, whether right or wrong.

I would pay to see Motl and Doron Zeilberger in a cage match about discrete math: http://www.math.rutgers.edu/~zeilberg/

I have the book in front of me right now (I originally read it around 2007). It's very sparse on actual math: I couldn't find anything that could be considered a mathematical treatment of String Theory. It's more about the academic culture surrounding the theory.

Disclaimer: I'm not a physicist.