# What is this strange effect called? \[Flying question: plane and bright spot\] **URL:** \ **Category:** Factual Questions\ **Created:** [April 3, 2012, 5:49am UTC](https://boards.straightdope.com/t/what-is-this-strange-effect-called-flying-question-plane-and-bright-spot/617670 "2012-04-03T05:49:36Z")\ **Posts on this page:** 17\ **Page:** 2
**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:** [April 4, 2012, 12:20pm UTC](https://boards.straightdope.com/t/what-is-this-strange-effect-called-flying-question-plane-and-bright-spot/617670/21 "2012-04-04T12:20:07Z")
> [@JWT\_Kottekoe](#): > > As Francis Vaughn mentioned in the very first response, it is indeed the glory (a.k.a. the heiligenschein or gegenschein in various contexts). Look at the Wikipedia article Francis linked and you’ll see more than one picture taken from an airplane. > > I love watching the Glory from my airplane window, especially watching from takeoff as the shadow of the plane gets smaller and smaller until it is surrounded by the glory and eventually disappears leaving only the glory behind. Many materials (not just spherical drops) exhibit a pronounced retroreflection, i.e. reflect light directly back to the source. Thus, if you are far enough away for the shadow of your head or the plane to be smaller than the angular range of the retroreflection peak, you will see the glory. > > My favorite example is the retroreflection of the Moon’s surface, evident in the clearly visible glory in the reflecting visors of the astronauts. In the reflection, you can often see the astronaut’s shadow, with a glory surrounding the shadow of his head. No, it’s not a glory (which is itself not the same as heilingenschein, for reasons given in my posts above. I love looking for glories myself when flying in an airplane, but the glory has clear rainbow-like colored bands surrounding the plane’s shadow. Although you definitely _could_ see a glory without the shadow, in fact I never have. There’s another effect that can cause a bright spot in the vicinity of one’s shadow on the ground, but one that’s only become possible relatively recently – the prevalence of retroreflectors on signs, road dividers, highway white lines, etcetera. Retroreflectors, working in a variety of ways (corner cubes, or partial focusing similar to heiligenschein, or some other mechanism) will send a beam back very nearly antiparallel to the incident beam, so if you areapproximately between the sun and the retroreflector you will see a bright flash of light. (It isn’t perfect, and the reflection spreads out a bit, so your own shadow doesn’t make the effect disappear). This is an intermittent effect, though, and one experiences it as a series of bright flashs as one passes over one retroreflector, then another. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [April 4, 2012, 4:45pm UTC](https://boards.straightdope.com/t/what-is-this-strange-effect-called-flying-question-plane-and-bright-spot/617670/22 "2012-04-04T16:45:06Z")
> [@](#): > > Although you definitely could see a glory without the shadow, in fact I never have. I’ve heard that early fighter pilots (WWI, maybe?) would try to keep the glory centered on their opponent while they were diving, since that would mean they’d be coming out of the Sun from the other guy’s point of view. Apparently it was easier to spot than the shadow. ---
**Author:** ![JWT\_Kottekoe](https://avatars.discourse-cdn.com/v4/letter/j/3ec8ea/32.png) [@JWT\_Kottekoe](https://boards.straightdope.com/u/JWT_Kottekoe)\ **Post date:** [April 5, 2012, 5:34am UTC](https://boards.straightdope.com/t/what-is-this-strange-effect-called-flying-question-plane-and-bright-spot/617670/23 "2012-04-05T05:34:22Z")
> [@CalMeacham](#): > > No, it’s not a glory (which is itself not the same as heilingenschein, for reasons given in my posts above. Ignorance fought. Thankyou. I’ve been carrying around an overly broad definition of the glory in my head. From your posts I now understand that there are distinctions made between these various manifestations of enhanced retroreflection. ---
**Author:** ![bungston](https://avatars.discourse-cdn.com/v4/letter/b/e495f1/32.png) [@bungston](https://boards.straightdope.com/u/bungston)\ **Post date:** [December 3, 2013, 7:37pm UTC](https://boards.straightdope.com/t/what-is-this-strange-effect-called-flying-question-plane-and-bright-spot/617670/24 "2013-12-03T19:37:34Z")
I found this thread trying to find an explanation for this phenomenon. I was on a commercial flight at cruising altitude. On flying across the desert I noticed different colored flashes of light from the ground - these were the above mentioned retroflectors. I realized they were in a large bright spot moving across the ground. This spot was big - easily encompassing several houses. At one point I could see a dark trail behind this bright spot which must have been the shadow of the contrail. On encountering clouds I did see the glory as described here - a miniature round rainbow halo. This was in the light clouds below us, circling what must have been the beam of light coming down from the plane to produce the spot on the ground. This must be the same phenomenon as around the astronauts shadow, but minus the shadow. Plus this bright spot was big relative to the plane. I am skeptical that the bright spot itself is caused by water droplets in the manner of a rainbow. Where are those on the moon? I am looking for an explanation in terms of optics. ---
**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:** [December 4, 2013, 3:49am UTC](https://boards.straightdope.com/t/what-is-this-strange-effect-called-flying-question-plane-and-bright-spot/617670/25 "2013-12-04T03:49:35Z")
The Opposition effect. > **[Opposition Effect](https://atoptics.co.uk/atoptics/oppos1.htm)** > > Atmospheric optics, meteorological optics, colour and light outdoors with downloadable freeware to simulate effects ---
**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:** [December 4, 2013, 3:55am UTC](https://boards.straightdope.com/t/what-is-this-strange-effect-called-flying-question-plane-and-bright-spot/617670/26 "2013-12-04T03:55:30Z")
Opposition effect mechanism. > **[Opposition effect mechanism](https://atoptics.co.uk/atoptics/oppos2.htm)** > > Atmospheric optics, meteorological optics, colour and light outdoors with downloadable freeware to simulate effects Heiligenschein mechanism [http://www.atoptics.co.uk/droplets/heilfrm.htm](http://www.atoptics.co.uk/droplets/heilfrm.htm) Glory Mechanism [http://www.atoptics.co.uk/droplets/glofeat.htm](http://www.atoptics.co.uk/droplets/glofeat.htm) (note that this effect is not fully understood, according to Les Crowley) ---
**Author:** ![chacoguy](https://avatars.discourse-cdn.com/v4/letter/c/50afbb/32.png) [@chacoguy](https://boards.straightdope.com/u/chacoguy)\ **Post date:** [December 4, 2013, 5:37am UTC](https://boards.straightdope.com/t/what-is-this-strange-effect-called-flying-question-plane-and-bright-spot/617670/27 "2013-12-04T05:37:38Z")
> [@eburacum45](#): > > The Opposition effect. > [http://www.atoptics.co.uk/atoptics/oppos1.htm](http://www.atoptics.co.uk/atoptics/oppos1.htm) > [@eburacum45](#): > > Opposition effect mechanism. > [http://www.atoptics.co.uk/atoptics/oppos2.htm](http://www.atoptics.co.uk/atoptics/oppos2.htm) > > Heiligenschein mechanism > [http://www.atoptics.co.uk/droplets/heilfrm.htm](http://www.atoptics.co.uk/droplets/heilfrm.htm) > > Glory Mechanism > [http://www.atoptics.co.uk/droplets/glofeat.htm](http://www.atoptics.co.uk/droplets/glofeat.htm) > (note that this effect is not fully understood, according to Les Crowley) That was seriously impressive. ---
**Author:** ![GusNSpot](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gusnspot/32/436_2.png) [@GusNSpot](https://boards.straightdope.com/u/GusNSpot)\ **Post date:** [December 4, 2013, 7:32am UTC](https://boards.straightdope.com/t/what-is-this-strange-effect-called-flying-question-plane-and-bright-spot/617670/28 "2013-12-04T07:32:26Z")
One of the perks of flying. The beauty is always better than the science. Grab the beauty. If you are trying to figure out the reason, you will miss the next three things that will amaze you. IMO. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [December 4, 2013, 6:23pm UTC](https://boards.straightdope.com/t/what-is-this-strange-effect-called-flying-question-plane-and-bright-spot/617670/29 "2013-12-04T18:23:44Z")
Quite the contrary: If you know the science, then you’ll know where to look to see the beauty. I can’t even tell you the number of times I’ve been in a large group, but been the only one to notice a rainbow. Plus, of course, the science itself has a beauty to it, and that beauty is always there, whether the manifestation is or not. You can only directly appreciate a glory, or a rainbow, or whatever, when the conditions are right, but you can always appreciate the phenomena that lead to them. ---
**Author:** ![Chessic\_Sense](https://avatars.discourse-cdn.com/v4/letter/c/7c8e57/32.png) [@Chessic\_Sense](https://boards.straightdope.com/u/Chessic_Sense)\ **Post date:** [December 4, 2013, 10:14pm UTC](https://boards.straightdope.com/t/what-is-this-strange-effect-called-flying-question-plane-and-bright-spot/617670/30 "2013-12-04T22:14:49Z")
> [@GusNSpot](#): > > The beauty is always better than the science. > … > If you are trying to figure out the reason, you will miss the next three things that will amaze you. If that were true, chess games wouldn’t ever be beautiful. ---
**Author:** ![GusNSpot](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gusnspot/32/436_2.png) [@GusNSpot](https://boards.straightdope.com/u/GusNSpot)\ **Post date:** [December 5, 2013, 1:10am UTC](https://boards.straightdope.com/t/what-is-this-strange-effect-called-flying-question-plane-and-bright-spot/617670/31 "2013-12-05T01:10:31Z")
I did note ‘IMO.’ 😛 ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [December 5, 2013, 1:23am UTC](https://boards.straightdope.com/t/what-is-this-strange-effect-called-flying-question-plane-and-bright-spot/617670/32 "2013-12-05T01:23:51Z")
> [@GusNSpot](#): > > The beauty is always better than the science. \*I have a friend who’s an artist and has sometimes taken a view which I don’t agree with very well. He’ll hold up a flower and say “look how beautiful it is,” and I’ll agree. Then he says “I as an artist can see how beautiful this is but you as a scientist take this all apart and it becomes a dull thing,” and I think that he’s kind of nutty. First of all, the beauty that he sees is available to other people and to me too, I believe. Although I may not be quite as refined aesthetically as he is … I can appreciate the beauty of a flower. At the same time, I see much more about the flower than he sees. I could imagine the cells in there, the complicated actions inside, which also have a beauty. I mean it’s not just beauty at this dimension, at one centimeter; there’s also beauty at smaller dimensions, the inner structure, also the processes. The fact that the colors in the flower evolved in order to attract insects to pollinate it is interesting; it means that insects can see the color. It adds a question: does this aesthetic sense also exist in the lower forms? Why is it aesthetic? All kinds of interesting questions which the science knowledge only adds to the excitement, the mystery and the awe of a flower. It only adds. I don’t understand how it subtracts. - Richard P. Feynman - ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [December 5, 2013, 2:27am UTC](https://boards.straightdope.com/t/what-is-this-strange-effect-called-flying-question-plane-and-bright-spot/617670/33 "2013-12-05T02:27:48Z")
And yet again Feynman says it better than I could. ---
**Author:** ![GusNSpot](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gusnspot/32/436_2.png) [@GusNSpot](https://boards.straightdope.com/u/GusNSpot)\ **Post date:** [December 5, 2013, 5:09pm UTC](https://boards.straightdope.com/t/what-is-this-strange-effect-called-flying-question-plane-and-bright-spot/617670/34 "2013-12-05T17:09:17Z")
So, while Pilot In Command, it is a not so pretty thing to be thinking about how the science makes things more beautiful instead of flying the plane with due diligence. Just a pleasant feeling because of the beauty does not cause a lapse in the proper kind of thinking that should be going on in the head of the Pilot In Command. A perfect breakout at minimums on an instrument approach is a thing of great beauty. It does not happen if the pilot is thinking about the science behind it while trying to accomplish the said approach. It is not a beautiful thing to see how so many here always jump to the most least likely interpretation of a statement, the worst case of the possible reasons for said post, so they can pontificate on their own superior being, thinking, understand of everything, & the importance of others know that. Not pretty at all. Does not fight ignorance much either. IMO ← Note. Not trying to be better than others. I leave that endeavor to others. One does not become an old pilot by being a know it all cocky young pilot. I am an old pilot, are you? 😃 ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [December 5, 2013, 5:48pm UTC](https://boards.straightdope.com/t/what-is-this-strange-effect-called-flying-question-plane-and-bright-spot/617670/35 "2013-12-05T17:48:21Z")
> [@](#): > > A perfect breakout at minimums on an instrument approach is a thing of great beauty. It does not happen if the pilot is thinking about the science behind it while trying to accomplish the said approach. I would think rather that it doesn’t happen unless the pilot is thinking a great deal about the science behind it. ---
**Author:** ![ElvisL1ves](https://avatars.discourse-cdn.com/v4/letter/e/5daacb/32.png) [@ElvisL1ves](https://boards.straightdope.com/u/ElvisL1ves)\ **Post date:** [December 5, 2013, 6:57pm UTC](https://boards.straightdope.com/t/what-is-this-strange-effect-called-flying-question-plane-and-bright-spot/617670/36 "2013-12-05T18:57:40Z")
Pretty sure **GusNSpot** is referring to the pilot being in [The Flow](http://en.wikipedia.org/wiki/Csikszentmihalyi#Flow) - that state when the science and all relevant knowledge are instinctive, and your total focus, both conscious and subsconscious, is on the process. ---
**Author:** ![GusNSpot](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gusnspot/32/436_2.png) [@GusNSpot](https://boards.straightdope.com/u/GusNSpot)\ **Post date:** [December 6, 2013, 1:10am UTC](https://boards.straightdope.com/t/what-is-this-strange-effect-called-flying-question-plane-and-bright-spot/617670/37 "2013-12-06T01:10:24Z")
> [@ElvisL1ves](#): > > Pretty sure **GusNSpot** is referring to the pilot being in [The Flow](http://en.wikipedia.org/wiki/Csikszentmihalyi#Flow) - that state when the science and all relevant knowledge are instinctive, and your total focus, both conscious and subsconscious, is on the process. Nice way to splain it, Thanks. [Previous page](https://boards.straightdope.com/t/what-is-this-strange-effect-called-flying-question-plane-and-bright-spot/617670.md?page=1)