Global Endeavor to Read the Black Hole—The Working Mechanisms of Event Horizon Telescope

For centuries, human beings cooperated to make endeavors to reach for the full image of the galaxy. This dream has finally come real in the past decades—by constructing the Event Horizon Telescope. On May 12 th , 2022, the image of Sa-gittarius A* is first observed and reveals the existence of a super massive black hole. This is the “masterpiece” of EHT. The most unique characteristic of this momentous engineering is the span of the project: over 8 countries engaged in data processing and image capturing jobs, just for obtaining valuable information about black holes from outer space. To uncover the secret of high-resolution pic-ture-capturing ability and telecommunicating technology, getting familiar with optical interferometry and information processing is indispensable. From the basic concept of resolving images—Rayleigh Criterion—to the Fourier transform of electromagnetic wave, immense knowledge is involved in taking a picture of the black hole. This is why low-pass filters can sift out the higher frequencies out of the band.