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📘 How Black Holes Bend Light

Watch a beam of light skim past a black hole. Mass curves spacetime, and the beam follows the straightest path that geometry allows. Far away, deflection is small; closer in, the path can arc or head toward capture.

5
lessons
~25 min
to learn
Adults
level
Start the course →

What you’ll learn

  1. Gravity changes the routeExplain gravity changes the route in the black-hole light-bending story.A coherent part of the causal chain from curved spacetime to the first image.
  2. The horizon and photon sphereExplain the horizon and photon sphere in the black-hole light-bending story.A coherent part of the causal chain from curved spacetime to the first image.
  3. Light from the accretion flowExplain light from the accretion flow in the black-hole light-bending story.A coherent part of the causal chain from curved spacetime to the first image.
  4. What the first image showedExplain what the first image showed in the black-hole light-bending story.A coherent part of the causal chain from curved spacetime to the first image.
  5. Build the explanationExplain build the explanation in the black-hole light-bending story.A coherent part of the causal chain from curved spacetime to the first image.

Questions this course answers

Why does light bend near a black hole?

General relativity says light follows the geometry of curved spacetime.

Put these outcomes in order as a ray aims closer to a non-rotating black hole.

Closer approaches move from escape with small bending toward capture and horizon crossing.

What is the event horizon?

Inside it, no future light path can reach a distant observer.

Match each term to its role.

These are related but distinct parts of the black-hole picture.

Why is the shadow larger than the event horizon?

Critical escaping paths near the photon region are strongly lensed, making the apparent shadow larger.

Where does the bright ring's emission come from?

The accretion flow outside the horizon emits the photons that are then lensed.

Grounded in trusted sources

  • NASA Science, Black Hole Anatomy, https://science.nasa.gov/universe/black-holes/anatomy/
  • Event Horizon Telescope Collaboration, Astronomers Capture First Image of a Black Hole, https://eventhorizontelescope.org/press-release-april-10-2019-astronomers-capture-first-image-black-hole
  • Event Horizon Telescope Collaboration, Can we really photograph a black hole?, https://eventhorizontelescope.org/faq/can-we-really-photograph-black-hole
  • Event Horizon Telescope Collaboration, M87 One Year Later, https://eventhorizontelescope.org/M87-one-year-later-proof-of-a-persistent-black-hole-shadow
  • NASA Jet Propulsion Laboratory, How Scientists Captured the First Image of a Black Hole, https://www.jpl.nasa.gov/edu/resources/teachable-moment/how-scientists-captured-the-first-image-of-a-black-hole/
  • Wikimedia Commons MediaWiki API, https://commons.wikimedia.org/w/api.php

Every Wunder lesson is built from real, reputable sources — never invented.

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