The Physics of Sunsets – Starts With A Bang

The Physics of Sunsets – Starts With A Bang.

Image credit: Tamas Ladanyi (TWAN), over Lake Balaton, Hungary.

The first and most obvious is the change in coloration of the Sun, as well as a severe drop in the Sun’s brightness. On an airless world like the Moon, the Sun at sunset would look no different than at any other time. But it’s the Earth’s atmosphere that makes sunsets so special.

Image credit: Bob King of http://astrobob.areavoices.com/.

When the Sun appears progressively lower and lower on the horizon, its light needs to pass through more and more of the atmosphere to reach our eyes. You might not think of the atmosphere as being a very good prism, but when you pass through around 1000 miles of it just before the Sun dips below the horizon, it starts to add up.

Image credit: Pete Lawrence (Digital-Astronomy).

The bluer wavelengths of light get scattered away, leaving only the reddest wavelengths that reach your eye. As the sun drops towards the horizon, it progressively loses violets and blues, then greens and yellows, and finally even the oranges, leaving only the reds behind.

You may not even realize it, but by time you’d see a sunset like the picture above, the Sun has already technically set, it’s only due to the fact that the atmosphere bends light that we’re still seeing it like this.

Image credit: R Nave of Hyperphysics, from http://hyperphysics.phy-astr.gsu.edu/hbase/atmos/redsun.html.

This is why, if you time a sunset, it will take longer than the expected 120 seconds to go from the moment it touches the horizon to the moment it dips below, even during the equinox at the equator, where it rises and sets as close to completely vertical to the horizon as possible. The Sun appears to linger due to the refraction of our atmosphere.  READ MORE………

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One thought on “The Physics of Sunsets – Starts With A Bang

  1. Pingback: Haze turns Sun red » Well Blogger Me

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