Science

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Kuala Lumpur, Federal Territory of Kuala Lumpur, Malaysia

Mind-blowing science factoid of the day:

You already knew that it takes ~8 mins for photons to travel from the Sun to Earth (~150 million km). What you’re observing is a past Sun ~8 mins behind its actual position in the sky.

However, each photon emitted by the Sun’s core first has to traverse dense radiative and then convective layers before reaching the surface of the photosphere.

That journey involves a very slow and inefficient random walk (think Brownian motion and boiling fluid dynamics, respectively) through a dense soup of particles that constantly absorb and re-emit photons in new directions.

The process takes between 10,000 and 170,000 years, and no single photon makes the full trip; the new photons eventually leaving the surface are the result of countless energy handovers along the way.

This means that there’s a good chance that the energy of the sunlight you see today was generated before Homo sapiens even existed, even if the photons themselves were emitted ~8 mins ago.

Aviator, diver, Etherean, nexialist, PhD in aviation and climate science, host of /diving /ethfinance /forteantimes /geopolitics /science /singapore /thomas

The Sun is in hydrostatic equilibrium, so the inward gravity pull and the outward pressure from hot plasma and radiation balance each other out.

If the core’s nuclear fusion stopped, the Sun would cool down and contract rapidly, though not collapse instantly because it has enough thermal inertia to last 10–20M years (something called the Kelvin–Helmholtz timescale). The diffusion of photons inside the radiative layer (that slow random walk I was referring to) would stop almost right away because of rapid changes in the local temperature, density gradient, and pressure balance of the layer.

The photons “in transit” would be absorbed by the increasingly dense layer, turned into plasma, or reflected inward by the increasing opacity of the layer. The conveyor belt would essentially freeze or even reverse almost right away.

Only those photons that had already reached the surface of the photosphere would be able to escape (that’s ~8.3 minutes worth of sunlight for us).

Note: I am not an astrophysicist, this is only based on my reading in preparation for the cast. Caveat lector

This was immediately my question 🙏

Does this mean there would be a flood of photons released as the photosphere cooled? Or what happens to them during this very quick transition?

If I'm reading this correctly it means there should be a massive amount more photons still in the photosphere than are regularly emitted from it, right?

Bonus factoid:

If the Sun suddenly stopped producing photons at its core, the light would still abruptly go out on Earth after only ~8 minutes, despite the photons in slow transit beneath the photosphere.

That’s because the photosphere is relatively thin and has a very low thermal inertia, and thus would cool very rapidly once the core stopped producing energy ✈️

I recently watched a video about that one time that a bulb imploded in the Super Kamiokande experiment and how the cavitation pressure blew away all the neighboring bulbs in an expanding wave. Must have been an expensive repair. Such a fascinating experiment indeed though

That’s why I found the image of the sun taken with neutrinos observation much more interesting. Neutrinos goes staring from the from the core of the sun to us. No bouncing. They pass thru everything. Straight line.

> “When this random walk process is applied to the interior of the sun, and an accurate model of the solar interior is used, most answers for the age of sunlight come out to be between 10,000 and 170,000 years.”

https://web.archive.org/web/20090515085541/http://sunearthday.nasa.gov/2007/locations/ttt_sunlight.php

Had additional peer-reviewed sources at the bottom. I injected the term “brownian motion” as illustration but the papers only describe it as a random walk

Software Engineer @ Cadence Design Systems. B4: Stanford EE / Illinois ECE

I'm curious b/c modeling photons with brownian motion is novel to me. Where's the 10k-170k stat from?

I like talking about our awesome planet, doing engineering, and making music. And of course, DRAGONS!!!🐉🐉🐉
Nature is my tripod :)
she/they

This is literally insane🤯 can i make this into a video pleaseeeee XD

Organizing Casts, annotating thoughts, keeping you sane on farcaster.