The long list of unanswered questions about black holes contains one particularly surprising item: How do they eat? Unlike many of the riddles that black holes pose, this one seems so simple: What do you mean we don’t know how things fall into a black hole?...
The technique that the astronomers of the Event Horizon Telescope (EHT) use to observe black holes is called Very Long Baseline Interferometry, or VLBI, but it might as well be called Extremely Delayed Gratification Astronomy: it can take weeks or months after an observing run to find out whether the telescope array actually saw anything...
Imagine a trio of aerobatic aircraft. Over the years they've gotten very good at their routine. But they want to add another five or six or seven members.
Each of the telescopes that the astronomers of the Event Horizon Telescope (EHT) are currently working to bring into their black-hole-observing, planet-size array is a special case.