# Why does the sun feel warmer from a reflection than it does straight on in this situation? **URL:** \ **Category:** Factual Questions\ **Created:** [January 2, 2026, 5:48pm UTC](https://boards.straightdope.com/t/why-does-the-sun-feel-warmer-from-a-reflection-than-it-does-straight-on-in-this-situation/1026278 "2026-01-02T17:48:55Z")\ **Posts on this page:** 5\ **Page:** 2
**Author:** ![Reply](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/reply/32/15952_2.png) [@Reply](https://boards.straightdope.com/u/Reply)\ **Post date:** [January 6, 2026, 11:54pm UTC](https://boards.straightdope.com/t/why-does-the-sun-feel-warmer-from-a-reflection-than-it-does-straight-on-in-this-situation/1026278/21 "2026-01-06T23:54:16Z")
> [@filmore](#): > > This is probably causing the reflected sunlight to be focused on a spot rather than scattered in all directions. Thanks for the update! Mystery (probably) solved. > [@eburacum45](#): > > Here is a picture of caustics caused by square windows in a street in Oxford Wow, I’m surprised that hasn’t caused a window-trail-shaped lightening of the paint following the sun’s path. You’d expect there to be more UV damage along the trail. ---
**Author:** ![filmore](https://avatars.discourse-cdn.com/v4/letter/f/7993a0/32.png) [@filmore](https://boards.straightdope.com/u/filmore)\ **Post date:** [January 7, 2026, 2:43am UTC](https://boards.straightdope.com/t/why-does-the-sun-feel-warmer-from-a-reflection-than-it-does-straight-on-in-this-situation/1026278/22 "2026-01-07T02:43:17Z")
> [@eburacum45](#): > > The pattern of light reflected off a window is sometimes called a ‘caustic’; it is one of a class of different light patterns caused by reflection and/or refraction. Thanks for that enlightening post. Really interesting picture of the effect on that wall. ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [January 7, 2026, 12:58pm UTC](https://boards.straightdope.com/t/why-does-the-sun-feel-warmer-from-a-reflection-than-it-does-straight-on-in-this-situation/1026278/23 "2026-01-07T12:58:48Z")
> [@Reply](#): > > Wow, I’m surprised that hasn’t caused a window-trail-shaped lightening of the paint following the sun’s path. You’d expect there to be more UV damage along the trail. I don’t think that would happen because a/ the Sun’s elevation changes slightly every day and b/ this is Britain. Sun is a relatively rare phenomenon. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [January 7, 2026, 1:17pm UTC](https://boards.straightdope.com/t/why-does-the-sun-feel-warmer-from-a-reflection-than-it-does-straight-on-in-this-situation/1026278/24 "2026-01-07T13:17:40Z")
> [@Reply](#): > > Wow, I’m surprised that hasn’t caused a window-trail-shaped lightening of the paint following the sun’s path. You’d expect there to be more UV damage along the trail. There’s an art installation consisting of a highly reflecting curved wall in which the sun’s concentrated light burns a path through the grass underneath. It wasn’t intentional, but it worked out that way. (I wrote a column on such light-concentrating art installations around the world. None of the designers appear to have taken into account that effects of light concentration on their surroundings. Nor architects. We can only be glad that the Chicago sculpture “Cloud Gate” – AKA “The Bean” – is all convex curves rather than concave ones.) ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [January 7, 2026, 1:22pm UTC](https://boards.straightdope.com/t/why-does-the-sun-feel-warmer-from-a-reflection-than-it-does-straight-on-in-this-situation/1026278/25 "2026-01-07T13:22:51Z")
There is a device called a Campbell-Stokes recorder that consist of a perfectly spherical solid glass ball, which focuses the Sun’s light onto a card at the back, showing how much sunlight there is each day. These recording cards have to be changed regularly, because the elevation of the Sun changes constantly over the year. > **[Campbell–Stokes recorder](https://en.wikipedia.org/wiki/Campbell%E2%80%93Stokes_recorder)** > > The Campbell–Stokes recorder (sometimes called a Stokes sphere) is a type of sunshine recorder. It was invented by John Francis Campbell in 1853 and modified in 1879 by Sir George Gabriel Stokes. The original design by Campbell consisted of large ball lens set into a wooden bowl with the Sun burning a trace on the bowl. Stokes's refinement was to make the housing out of metal and to have a card holder set behind the sphere. > The unit is designed to record how many hours of bright sunshine we... [Previous page](https://boards.straightdope.com/t/why-does-the-sun-feel-warmer-from-a-reflection-than-it-does-straight-on-in-this-situation/1026278.md?page=1)