Einstein’s theory of general relativity includes black holes but so do other theories of gravity, and the predictions are not sufficiently different to decide whether the supermassive black holes imaged so far, by the Event Horizon Telescope, really match Einstein’s prediction. But advanced simulations demonstrate that next-generation telescopes will achieve the precision needed to distinguish black holes in different theories and probe fundamental physics near the event horizon.
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References
Will, C. M. The confrontation between general relativity and experiment. Living Rev. Relativ. 17, 4 (2014). This review article explores the testing of general relativity.
The Event Horizon Telescope Collaboration et al. First M87 Event Horizon Telescope results. I. The shadow of the supermassive black hole. Astrophys. J. Lett. 875, L1 (2019). This paper reports the first image of a black hole, taken using the Event Horizon Telescope.
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Narayan, R., Igumenshchev, I. V. & Abramowicz, M. A. Magnetically arrested disk: an energetically efficient accretion flow. Publ. Astron. Soc. Jpn 55, L69–L72 (2003). This paper introduces the magnetically-arrested-disk, or MAD, state for black holes.
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This is a summary of: Uniyal, A. et al. The future ability to test theories of gravity with black-hole shadows. Nat. Astron. https://doi.org/10.1038/s41550-025-02695-4 (2025).
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Next-generation telescopes will be able to tell black-hole spacetimes apart. Nat Astron 10, 22–23 (2026). https://doi.org/10.1038/s41550-025-02717-1
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DOI: https://doi.org/10.1038/s41550-025-02717-1
