Today, let’s kick off our shoes and relax our standards for what counts as a reasonable spacetime. Let’s talk about spacetimes allowing for a certain kind of time travel, called…
Ice water on closed timelike curves
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Where the material conditional gets its truth conditions
Oh, the material conditional. Some love it, some hate it. But can we all agree that explaining it to the uninitiated is a perennial headache? If you’ve taught baby-logic, you…
How to time-reverse a quantum system
Time-reversing a classical Newtonian trajectory is simple. If q(t) and p(t) are the positions and momenta of a particle on the trajectory, then time reversal flips that trajectory as follows:…
2009 Nobel Laureates in Physics
The 2009 Nobel Laureates in Physics have been announced! This year the award honors pioneers in information technology. Half the prize is going to Charles Kao (Standard Tel Labs), and…
Visualize a Wave Function
Can you visualize a normalized wave function on spacetime? Let’s try with a simple example. The role of a wave function is to assign a complex number to each point…