why is the setting sun red?

Answer 1

Sunsets often have a red or orange color to them. Why is this? Sunlight (what we call "white light") is made up of all different colors of light, each having a different wavelength. During a sunset, more red light is scattered toward you because of aerosols in the lower atmosphere, compared to the amount of blue or green light. Since, at sunset, sunlight is passing through a much longer path of the lower atmosphere than when the sun is overhead, the effect of the aerosols becomes much stronger. So, you end up seeing more red light that any of the other colors of light, and the sky appears red.

Answer 2

The phenomena can be explained without using aerosols
or pollusion. At sunset, light reaching the eye has
travelled at a shallow angle, and traversed a greater
thickness of air than it does at noon. It has
encountered a lot of scattering, and much of its blue
light had been dispersed. What is left is the long-wave
content, the redness of sun set. The same thing
happens at sun rise.
http://www.zetatalk.com/poleshft/p141.htm
http://www.geography-site.co.uk/pages/physical/climate/sunset.html
http://www.uen.org/utahlink/weather/trivia4.html
http://www.gsfc.nasa.gov/scienceques2003/20030912.htm
http://www.sciencemadesimple.com/sky_blue.html
http://scifun.chem.wisc.edu/HOMEEXPTS/BlueSky.html
http://www.norbertines.co.uk/Ode%20to%20the%20Setting%20Sun.htm

Our Earth atmosphere predominately contains nitrogen
and oxygen molecules. These atoms behave as behave like
tiny optical tuning forks and selectively scatter light
waves of appropriate frequencies. The natural
frequencies that nitrogen and oxygen resonate with the
sunlight at are in the ultraviolet part of the white
light solar spectrum. Therefore, violet light scatters
in our atmosphere in large amounts. For every ten
violet photons scattered from a sunlight beam, only one
red photon in scattered. When we see the Sun setting,
through the thick Earth atmosphere, the higher
frequencies are scattered while the lower freqencies
are transmitted. At sunset, when the Sun is lowest in
the sky, and seen through the largest amount of "air
mass", we see it as an orangish-red color.
http://solar-center.stanford.edu/FAQ/Qsuncolor.html

Then, why is the setting sun more red than the rising sun?
http://www.madsci.org/posts/archives/nov2000/974906944.As.q.html

What most of us do not see normally is the unusual red
column of light which rises mysteriously from a setting
sun. The mysterious column is called Sun Pillar - a
phenomenon where sunlight reflects off of distant
falling ice crystals.
http://antwrp.gsfc.nasa.gov/apod/ap011107.html
http://www.astrophys-assist.com/wilobs/weathwin/sunpillr.htm
http://www.astrophys-assist.com/wilobs/weathwin/sunpillr.htm
http://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search?sun+pillar
http://www.cs.cmu.edu/~zhuxj/astro/html/sunpillar.html

A few people claim they've seen a brilliant and
instantaneous green flash as the top of the fiery blob
dipped out of sight. The key to the green flash mystery
again lies in refraction.
http://www.space.com/scienceastronomy/sun_mysteries_020716-1.html
http://hyperphysics.phy-astr.gsu.edu/hbase/atmos/redsun.html
http://www.redshift.com/~bcbelknap/GreenFlash.html
http://hyperphysics.phy-astr.gsu.edu/hbase/atmos/redsun.html
http://www.space.com/scienceastronomy/sun_mysteries_020716-1.html
http://mintaka.sdsu.edu/GF/bibliog/who.html
http://scubageek.com/articles/wwwgfl.html

Answer 3

When the sun is at the zenith, it has less atmosphere and pollution to shine through. As it sets, the light you are seeing LITERALLY has to travel through more atmosphere. Imagine an orange. Stick a pin in at 90 degrees and it has very little skin to go through before it hits pulp. NOW put the needle at 10 degrees and see how much more peel you have to go through before you hit pulp. same thing with sunshine.

That extra atmosphere and pollution diffuses the light toward the red end of the spectrum.

TFTP

Answer 4

It just is.....