How to take pictures of a black hole
Interesting article on the VLBI
Think of VLBI like this: You’re standing at the center of the galaxy, looking at Earth, which is way out at the Milky Way’s fringe. Now, imagine Earth as a mirror, but only the places where there are radio telescope arrays on its surface are polished--the rest of this planet-sized mirror is blacked out. These polished spots are the only places on the mirror that can collect data. This sparse mirror wouldn’t provide a very complete picture to someone peering through the other end.
But now imagine the Earth rotating. The polished portions of the lens--the parts collecting data--begin to slowly move across the blacked-out areas of the mirror, collecting data from different points on its surface as rotation and the seasonal tilt of the planet continue. Eventually, the telescopes--and there are many scattered all over the globe--have collected data from positions all over this lens, just not all at the same time. Over months and years, this data is sufficient to stitch together a rather thorough view roughly equivalent to that captured by an Earth-sized telescope mirror
"Don't seek these laws to understand. Only the mad can comprehend..." -- George Cosbuc