Run · Mass Bends Light

Settle in title

Season 1 · Session 06

Mass Bends Light

Heavy things bend the path of light around them.

Prompt deck —

Use ↓ / ↑ to move between movements. → / ← steps the prompts. Space reveals on the wall.

Host notes, laptop only

Framing

We're not asking whether light can bend. Eddington measured it in 1919. We're asking what it means that gravity steers light without ever touching its mass.

Opening question (Settle in)

If light has no mass, how can gravity change where it goes?

The precise version (Watch)

General relativity predicts that light follows geodesics in curved spacetime, meaning it is deflected by gravitational fields. The deflection angle for light grazing the Sun's limb is 1.75 arcseconds, exactly twice the Newtonian prediction. Arthur Eddington's solar eclipse expeditions of May 29, 1919 (to Príncipe and Sobral) measured this deflection and confirmed Einstein's value. Gravitational lensing by galaxy clusters can produce Einstein rings and arcs. The first confirmed gravitational lens was discovered in 1979 (Walsh, Carswell & Weymann). Strong lensing, weak lensing, and microlensing are now standard tools in cosmology and exoplanet searches.

If it wobbles

Confidently wrong — Don't argue with 'light has no mass so gravity can't touch it.' Redirect. 'Right, no mass. So why did the starlight shift? What's bending, the light or the space it crosses?'
Dead silence — Anchor it. 'In 1919 we pointed cameras at an eclipse to test an equation. The stars had moved. Just sit with that for a moment.'
Runaway debate — Pull back. 'Hold the interpretation. Let's agree first on what Eddington's plates actually measured.'
Tipping into dogma — Name it. 'We're not crowning Einstein. We're noticing that a precise number was predicted, then found in the sky.'

Wrap — close on (LOCKED)

How do you feel about this science and its understanding of reality?

Mass Bends Light

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