Light takes up to 2.9 million years to travel from the Sun’s core to its surface.
It then travels the entire 93,000,000 miles (1 AU) to Earth in just 8 minutes and 19 seconds. This is pretty funky since the Sun’s core is “only” 430,000 miles from its surface.
For comparison, light from the Moon takes 1.278 seconds to travel the 240,000 mile distance to Earth. Granted, rocketing yourself Apollo style from the Earth to the Moon is equivalent to going halfway from the Sun’s surface to its core (the Sun is pretty big), but that’s still only 2.5 seconds compared to 2.9 million years, so… what gives?
The Sun is so incredibly dense that it acts like a pinball machine covered in those spastic auto-bumpers. Our poor photon is a pinball that keeps running into other molecules and getting randomly bumped left, right, backwards, sideways, and every which way. Astronomers call the phenomena the “drunkard’s walk” because the photon is randomly staggering until sheer probability gets it to the Sun’s surface.
Most of the photons exiting the Sun are “only” 1,000 – 10,000 years old, but there are so many hundreds of trillions of photons entering your eyes every second that some of them were created 2.9 million years ago, others 100,000 years ago, and still more just 500 years ago.
Every single second, of every single day of your life, photons enter your eye that were birthed during every significant moment in human history. A photon just entered your eye that was created the same moment that Augustus Caesar became the first emperor of Rome; that same second you saw a photon birthed the same moment that Christopher Columbus first spotted “India” (i.e. America); nearly simultaneously a photon entered your eye from the day that Abraham Lincoln was shot at the Ford’s Theatre.
Alongside those photons from human history was one from 2.9 million years ago – this photon was created before humans had evolved, we did not yet exist as a species. In fact, this photon was already 2.6 million years old when the first members of our species walked the African savanna. Another 300,000 years later this photon breached the Sun’s surface and soon hit your cornea.
This happened to you today. It is not a thought experiment, it is one of the quirky realities of our universe.
The universe is a strange place.