September 09, 2016 at 12:57AM

Today I Learned: 1) A radio galaxy is a galaxy that emits a lot of light from synchrotron radiation. Synchrotron radiation is light emitted by electrons that are accellerated radially through a magnetic field. I'm not entirely clear on what causes synhrotron radiation in galaxies, but certain galaxies make a lot of it. Radio galaxies get their name because synchrotron radiation is primarily radio-frequency, although it does extend up through and past the visible range of the spectrum as well. 2) Back in 2006, NASA launched a radio telescope called ARCADE to the edge of space using a balloon. There are plenty of radio telescopes on the ground, but they work by comparing one pixel of the sky against another nearby pixel, and look for contrast. Among other things, ARCADE was sensitive enough, or otherwise had the right equipment, to measure absolute radio intensity. What ARCADE discovered is the Space Roar -- all of space appears to be lit up with about six times the radio noise that anybody had expected. We still do not know where the Space Roar comes from. 3) Tor, which stands for "The Onion Router", is a system of anonymous information routing via the internet. It is so named because it makes use of onion routing, which is a technique for preserving anonymity where a message has multiple layers of encryption, like an onion, that are sequentially decrypted by successive network nodes. Because of the method of encryption, each node can only decrypt its layer, which means it only knows where it received the packet from and where it should send the packet, but not anything further upstream or downstream, making it very difficult to trace where packets come from or go to. Surprisingly, at least to me, onion routing was developed *and patented* by the US Naval Research Laboratory. A couple of researchers at the NRL developed Tor and arranged for it to be released with a free license, and later split off to found The Tor Project, a non-profit organization that now manages and develops Tor.