The Event Horizon Telescope is in the news now because they are about to release the first ever picture of a black hole. They have been working on this since 2006. Why did it take 13 years to produce the first picture? What was the critical mass that was recently hit that made the picture now complete?
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asked Apr 10, 2019 at 4:11
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$\begingroup$ There were many new technologies needed. VLBI at shorter wavelengths, individual telescopes capable of precision observation at those wavelengths. Software and hardware for the data recording and correlation. Probably more... $\endgroup$– Steve LintonApr 12, 2019 at 12:33
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A single telescope does not have the right angle size to picture the black hole that far away. The scientists had to use 8 telescopes to take a picture of the same point in the sky and merge the data from all sites using super computer. The data retrieval must point to the same object at the same time. Given the diverse condition of the 8 locations, there are only 5 days in a year when all of them have clear enough skies to point to the same location in a year.
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$\begingroup$ Weather doesn't have much effect on radio telescopes. $\endgroup$– PM 2RingApr 12, 2019 at 12:42
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1$\begingroup$ @PM2Ring It does on mm-wave observations. But that isn't the reason for the delay and actually a maximum of 7 telescopes at a time were used in the published dataset and often fewer. $\endgroup$– ProfRobApr 12, 2019 at 14:09
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$\begingroup$ @RobJeffries Good point. Moisture absorbs microwaves. Which is why I said that weather doesn't have much effect. ;) Another undesirable effect is that high winds can vibrate the dish of a radio telescope. $\endgroup$– PM 2RingApr 12, 2019 at 16:14
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$\begingroup$ This still doesnt explain why it took 13 years $\endgroup$ Apr 13, 2019 at 0:45
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$\begingroup$ The collaboration was created in 2009. That's when the proposal to do the experiment was submitted to a 10 year planning process. First reference in linked wiki article. Before that there would have been some time doing the direct research for the proposal. So 13 years from initial serious idea to fruition. For space astronomy projects this is about average. The idea of a large space telescope goes back before 1966 when the first comprehensive studies were made (similar to a proposal to the 10 year plan), and in 1990 Hubble was launched : 24 years. history.nasa.gov/hubble $\endgroup$ Nov 6, 2019 at 5:13