3 ms·
A Brief History of Quantum Mechanics – With Sean Carroll
- hilbert42 5y agoBefore I had an insight into Relatively, I always thought there was something special about the geometry of free space. That earlier insight came from electromagnetic theory where the characteristic impedance, Z, of a coaxial cable is set by the geometry of its dimensions (the enclosed space between the outer casing and its inner conductor). For typical coaxes the impedance is usually between 50 and 75 ohms. Now consider the characteristic impedance of free space, Z0, which is approximately 377 ohms. I've always visualized that an ideal antenna as a device that 'matches' these spaces so that maximum electromagnetic energy can be transferred between them (between the space bound by the coax's dimensions and free space and vice versa). I'm not going to get into a heavy debate over this as it gets complicated very quickly but it seems to me there's a direct connection between the geometry of free space, the fine structure constant alpha and the permittivity and permeability of free space [through the relationships e^2 = 4πε0ħcα, c2 = 1/(ε0μ0), Z0 = E/H = μ0c = 1/ε0c, SI units], and that this has to include GR through energy and the geometry of free space. If Carroll and cohorts can tie GR into deep and meaningful ways with QFT, free space geometry, permittivity, etc. then they may be onto something big. Let's hope so. (It's always worried me that free space has constants like permittivity and permeability and that fudging them out using Gaussian units isn't a sensible way of dealing with the issue.)