Hot answers tagged

8

UVA passes through the atmosphere without losing much intensity, so per quote one it's intensity doesn't change, nor does it's magnitude as a percentage of total insolation vary, much, during the year (and what variance there is happens at source). Total ground level insolation intensity in $\mathrm{Wm^{-2}}$ does change with latitude and seasonal angle of ...


7

Here my wife holds a globe with the moon in view. I carefully processed in a bit-mode to find the curve of light on the globe and drew perpendicular lines. Plainly we can see that the moon-lite side is facing the sun in the same direction of my globe. The illusion is due to the sun being so far that the difference in angles shown in the drawing would not ...


6

Reddit user and r/EarthScience mod Halcyon3k pointed me to the following visualization that nicely illustrates Ash's great answer on the fact that "total ground level insolation intensity in $\mathrm{Wm^{-2}}$ does change with latitude and seasonal angle of incidence": (image source) Halcyon3k's explanation: Solar energy is measured in watts per ...


4

According to Ultraviolet Radiation, Human Health, and the Urban Forest it would seem at least the general shape you obtained is correct: Here they tracked the irradiance at noon over different months of the year not hours of the day, but the basic change is the same: high to low to high Solar Zenith Angle when irradiating a vertical surface leads to an ...


4

You can see this effect on the powerline above the railroad tracks in the picture you posted too, it doesn't look straight, even though it likely was in reality! The straight line between the sun and the moon is just even more curved. Just like what you see at http://chrisjones.id.au/MoonIllusion/ , like the top answer already posted. If you accept that the ...


2

When looking at the sky, spherical coordinates are used as a convenience. We turn our head and body in azimuth and altitude to compare the position of objects. In this regards, the sky looks like a sphere. (At least I visualize it as a sphere.) A Cartesian XY (or XYZ) grid cannot be easily used. The question then becomes: what is the path of a light beam in ...


2

I found one study from 2001 {1}: It was also determined that for a fulltime outdoor worker, the additional UVA exposure could approach approximately that of one third of a full winter’s day. For indoor workers with an outside lunch break of noon to 1 pm, the additional UVA exposure was on average 6.9 kJ m$^{-2}$...


1

TL;DR: It certainly is possible from a geosynchronous orbit, an altitude of 35786 km. It is also possible from a very high altitude weather balloon. A key issue is that the terminator is not a line. Thanks to the Earth's atmosphere, the terminator is instead a band that is about 1000 km across that gradually transitions from sunlit to dark. At most ...


Only top voted, non community-wiki answers of a minimum length are eligible