2
$\begingroup$

If the sun is closest to the North American Hemisphere in the winter than it is in the summer, why doesn't our faces and hands tan and/or blister quicker? Please provide two hyperlink sources with your answer. Thank you.

$\endgroup$
  • $\begingroup$ possible duplicate of What's the reason for the seasons? $\endgroup$ – DumpsterDoofus Apr 4 '14 at 14:16
  • 1
    $\begingroup$ I initially marked this as a duplicate, but JiK pointed out that the light intensity incident normal to a plane (like a face pointing towards the sun) does not change across the seasons (ignoring atmospheric loss). So this isn't really a question about what causes the seasons, but rather a question of whether the light volumetric energy density is actually lower in winter. $\endgroup$ – DumpsterDoofus Apr 4 '14 at 14:27
  • $\begingroup$ The sun is, of course, closer to all the hemispheres of earth in the Northern hemisphere winter... $\endgroup$ – DJohnM Apr 4 '14 at 17:14
  • $\begingroup$ Related: physics.stackexchange.com/q/114243/2451 $\endgroup$ – Qmechanic Dec 27 '14 at 10:00
2
$\begingroup$

Earth is only about 3% closer to the Sun during the northern-hemisphere winter, which means its intensity would only increase by a maximum of about 6%. There is more atmosphere to block out the UV rays that cause tanning and burns due to the shallower angle of incidence. You tend to wear more clothing (gloves, scarf, etc) that blocks the rays. It's cold, so I doubt a lot of people spend a lot of time outside just sitting around with their faces and hands towards the Sun and it would still take some time to get a noticeable tan with only a 6% increase in intensity and a decrease in the UV band from the longer path through the atmosphere.

TLDR: Many possible reasons contribute.

$\endgroup$
0
$\begingroup$

That's because the sun is shooting the light at such a small angle that the light have to travel trough the atmosphere for a longer distance. And the atmosphere will decrease the luminosity of the sun. If we could move with the earth in the outer space without rotation, then we would find that the sun is flying upward and downward, drawing a sine wave in the sky. And in winter, the sun will shoot the surface of the earth at a small angel.

$\endgroup$
  • 2
    $\begingroup$ @JohnRennie then make your own answer $\endgroup$ – ratchet freak Apr 4 '14 at 14:08
  • $\begingroup$ @JohnRennie The question is about the tanning of our faces and hands, and I cannot see why the intensity (power per square metre) on our faces and hands would be any lower. $\endgroup$ – JiK Apr 4 '14 at 14:09
  • $\begingroup$ @JohnRennie Isn't the area where the sunlight spread all the same during a whole year? $\endgroup$ – user43796 Apr 4 '14 at 14:10
  • $\begingroup$ This answer is either wrong, or very badly worded. $\endgroup$ – DumpsterDoofus Apr 4 '14 at 14:14
  • $\begingroup$ @JiK: The intensity (power per square meter at Earth's surface) is much lower in winter than in summer. That's the whole point of seasons. That's why winter is cold. $\endgroup$ – DumpsterDoofus Apr 4 '14 at 14:15

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy