Black holes are a theoretical prediction we can never see
Not wrong, but our understanding became significantly more precise.
TaughtBlack holes are predicted by general relativity and the indirect evidence is suggestive, but by definition light cannot escape one, so we will never actually image one.
NowThe Event Horizon Telescope released the first image of a black hole's shadow, in galaxy M87, in April 2019, and one of Sagittarius A* at our own galaxy's center in 2022.
What actually happened
The caution in older textbooks was reasonable. You cannot photograph a black hole itself. What you can photograph is the silhouette it casts against the hot glowing material swirling around it, and doing that required an instrument the size of Earth.
The Event Horizon Telescope solved this by linking radio dishes from Hawaii to Spain to the South Pole into a single virtual telescope using very long baseline interferometry. The 2019 image of M87*, a black hole about 6.5 billion times the Sun's mass, is the first direct visual evidence that event horizons are real objects and not just a solution to Einstein's equations.
Separately, Andrea Ghez and Reinhard Genzel shared the 2020 Nobel Prize for decades of tracking stars whipping around an invisible four-million-solar-mass object at the center of the Milky Way. Nothing about the theory was wrong. The evidence went from inference to photograph.
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Sources
- Event Horizon Telescope: First image of a black holeeventhorizontelescope.org
- The Nobel Prize in Physics 2020nobelprize.org
Who was taught this
Still standard through 2019, so anyone who finished school between 1950 and 2019 learned the earlier version.