The Sun II
When you’re heading out on a road trip, it sometimes feels like the most time-consuming part of the journey is just getting out of town.
The same thing happens with sunlight — it takes far longer for energy to escape the Sun itself than it does for that energy to travel from the Sun to Earth.
The Sun generates its energy in its core, which is hundreds of thousands of miles below the surface. The nuclei of hydrogen atoms ram together to form helium atoms, releasing energy.
As the energy heads toward the surface, though, it rams into atoms in the core or in the surrounding layer, known as the radiative zone. The atoms absorb the energy, then re-radiate it back into their surroundings. The new energy then rams into other atoms, with the process repeating over and over again.
Gradually, though, energy works its way to the next layer outward, the convective zone. In this layer, energy isn’t passed from atom to atom. Instead, blobs of gas heated by the radiative zone rise toward the surface like bubbles in a pot of boiling water. By the time they’ve reached the surface, the blobs have cooled to about 10,000 degrees Fahrenheit, so they radiate their energy mainly as visible light.
The trip from the Sun’s surface to Earth takes about eight minutes. But getting from the center of the Sun to the surface — the trip out of the Sun’s own neighborhood — takes much longer: up to millions of years.
More about the Sun tomorrow.
Script by Damond Benningfield, Copyright 2012
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