In my last post about spacetime, I explained how the geometry of spacetime is determined at each spacetime point by a set of 10 numbers. These 10 numbers are packaged together into a $$4 \times 4$$ matrix called the metric, … Continue reading
In Time as the Fourth Dimension?, I explained how to calculate the distance (or duration) squared between any two points of spacetime, using a spin-off of the Pythagorean theorem: $$!s^2= (\Delta x)^2 + (\Delta y)^2 + (\Delta z)^2 – (\Delta … Continue reading
There’s been a huge kerfuffle in the quantum gravity community since this summer, when some people here at UCSB published a paper arguing that (old enough) black holes may actually be surrounded by a wall of fire which burns people … Continue reading
What is the world made out of? In the most usual formulations of our current best theories of physics, the answer is fields. What are those? Well, if you know what a function is, you’re already most of the way … Continue reading
Previously, I described the main formula of Special Relativity: $$!s^2 = (\Delta x)^2 + (\Delta y)^2 + (\Delta z)^2 – (\Delta t)^2.$$This formula tells us the amount of distance squared between two points (if $$s^2 > 0$$) or the amount … Continue reading