Comments on: How Did the Stars Get Their Points? http://bit-player.org/2011/how-did-the-stars-get-their-points An amateur's outlook on computation and mathematics. Thu, 17 May 2012 10:21:59 +0000 http://wordpress.org/?v=2.6.3 By: S http://bit-player.org/2011/how-did-the-stars-get-their-points#comment-3935 S Wed, 04 Jan 2012 12:42:51 +0000 http://bit-player.org/?p=1054#comment-3935 I'm actually surprised that you see dimensionless points of light at all. Even since my earliest childhood, I remember seeing a few "spikes". Either my eyesight has always been bad, or when you say "I see some twinkling going on", you're talking of the same thing but just don't think of them as spikes, because they're not persistent and because of what you know from science. An illuminating experiment would be to get very young children (2 or 3 years old?), who have not been exposed to any cultural depictions of stars, show them the night sky, and ask them to draw what they saw. (Somehow I suspect we'll see spikes. But we should try and see.) I’m actually surprised that you see dimensionless points of light at all. Even since my earliest childhood, I remember seeing a few “spikes”. Either my eyesight has always been bad, or when you say “I see some twinkling going on”, you’re talking of the same thing but just don’t think of them as spikes, because they’re not persistent and because of what you know from science.

An illuminating experiment would be to get very young children (2 or 3 years old?), who have not been exposed to any cultural depictions of stars, show them the night sky, and ask them to draw what they saw. (Somehow I suspect we’ll see spikes. But we should try and see.)

]]> By: rms http://bit-player.org/2011/how-did-the-stars-get-their-points#comment-3925 rms Sat, 24 Dec 2011 19:08:35 +0000 http://bit-player.org/?p=1054#comment-3925 It seems that the point spread function (psf; essentially the diffraction pattern of a point source by an optical instrument) of the human eye, is star-shaped (it would be an Airy-like function of 'circular' only if our eyes had perfect rotational symmetry around the optical axis) http://iopscience.iop.org/0963-9659/7/1/002 It seems that the point spread function (psf; essentially the diffraction pattern of a point source by an optical instrument) of the human eye, is star-shaped (it would be an Airy-like function of ‘circular’ only if our eyes had perfect rotational symmetry around the optical axis)

http://iopscience.iop.org/0963-9659/7/1/002

]]> By: S http://bit-player.org/2011/how-did-the-stars-get-their-points#comment-3906 S Wed, 14 Dec 2011 01:49:45 +0000 http://bit-player.org/?p=1054#comment-3906 I looked at the sky last night. I didn't see any "dimensionless points of light". The less bright stars appeared as tiny dots, or tiny spheres -- but with a nonzero thickness. The brighter stars appeared to acquire spikes now and then, especially before your eyes focused on them. (Looking from the ground to the sky — before your eyes have figured out they're trying to focus on something far away — seems to accentuate the spikes.) What I saw were sometimes five-pointed stars, and sometimes five-pointed stars with one or two of the "points" missing. So yes, the effect may well be a mere accident due to a flaw in an optical instrument — only the most common and oldest optical instrument, of which there are more than 12 billion on earth. I looked at the sky last night. I didn’t see any “dimensionless points of light”. The less bright stars appeared as tiny dots, or tiny spheres — but with a nonzero thickness. The brighter stars appeared to acquire spikes now and then, especially before your eyes focused on them. (Looking from the ground to the sky — before your eyes have figured out they’re trying to focus on something far away — seems to accentuate the spikes.) What I saw were sometimes five-pointed stars, and sometimes five-pointed stars with one or two of the “points” missing.

So yes, the effect may well be a mere accident due to a flaw in an optical instrument — only the most common and oldest optical instrument, of which there are more than 12 billion on earth.

]]> By: Mark VandeWettering http://bit-player.org/2011/how-did-the-stars-get-their-points#comment-3905 Mark VandeWettering Tue, 13 Dec 2011 16:26:43 +0000 http://bit-player.org/?p=1054#comment-3905 Sadly, my days of seeing dimensionless points in the sky are over. Astigmatism has caused them to appear as spiky blobs. Oh well. For the sun, it's pretty easy to see how you might imagine rays coming out: anyone who has observed crepuscular rays or various kinds of atmospheric shadowing might naturally draw the sun with rays coming out. I don't see it as too puzzling that stars would also be drawn that way (since they too emit light) but do find it interesting that the moon is not drawn that way. Re: ancient Egyptians, they drew stars as either five pointed asterisks, or as simple dots or circles, so our indecision apparently goes back a long ways. :-) Sadly, my days of seeing dimensionless points in the sky are over. Astigmatism has caused them to appear as spiky blobs. Oh well.

For the sun, it’s pretty easy to see how you might imagine rays coming out: anyone who has observed crepuscular rays or various kinds of atmospheric shadowing might naturally draw the sun with rays coming out. I don’t see it as too puzzling that stars would also be drawn that way (since they too emit light) but do find it interesting that the moon is not drawn that way.

Re: ancient Egyptians, they drew stars as either five pointed asterisks, or as simple dots or circles, so our indecision apparently goes back a long ways. :-)

]]> By: Keith Flower http://bit-player.org/2011/how-did-the-stars-get-their-points#comment-3901 Keith Flower Mon, 12 Dec 2011 18:10:34 +0000 http://bit-player.org/?p=1054#comment-3901 The Chinese character for star - xing,? - also traditionally had a secondary meaning of dissemination, or spreading out. The Chinese character for star - xing,? - also traditionally had a secondary meaning of dissemination, or spreading out.

]]> By: lode http://bit-player.org/2011/how-did-the-stars-get-their-points#comment-3900 lode Mon, 12 Dec 2011 16:05:10 +0000 http://bit-player.org/?p=1054#comment-3900 the egyptians also used asterisks for stars: http://en.wikipedia.org/wiki/File:Goddess_nut.jpg the egyptians also used asterisks for stars:
http://en.wikipedia.org/wiki/File:Goddess_nut.jpg

]]> By: Matthias Gallé http://bit-player.org/2011/how-did-the-stars-get-their-points#comment-3899 Matthias Gallé Mon, 12 Dec 2011 09:15:07 +0000 http://bit-player.org/?p=1054#comment-3899 I always thought it was because of the image you get if you un-focus your eyes while looking at a source of light. I always thought it was because of the image you get if you un-focus your eyes while looking at a source of light.

]]> By: Jim Ward http://bit-player.org/2011/how-did-the-stars-get-their-points#comment-3898 Jim Ward Sun, 11 Dec 2011 13:50:23 +0000 http://bit-player.org/?p=1054#comment-3898 Twinkle, twinkle little dimensionless point of light? Twinkle, twinkle little dimensionless point of light?

]]> By: Doug L http://bit-player.org/2011/how-did-the-stars-get-their-points#comment-3893 Doug L Fri, 09 Dec 2011 19:37:39 +0000 http://bit-player.org/?p=1054#comment-3893 The moon is usually represented as a luminous disk without rays going out from it. But the sun is often represented as a disk WITH rays going out from it. Nobody actually sees rays (or flames) going out from the sun. The rays in a drawing of the sun seem to represent that it is dazzling to the eye. I think this is a clue to the rays going out from the center in the drawing of a star. The star itself is a dimensionless point of light. Nobody sees literal rays when gazing at a star in the sky. The rays in the drawing suggest that the star is dazzling (if bright) or twinkling (if not so bright). We don't think of the moon as needing the rays when it is drawn. It is not dazzling, in fact the light it gives varies a great deal with the lunar month. The moon is usually represented as a luminous disk without rays going out from it. But the sun is often represented as a disk WITH rays going out from it.

Nobody actually sees rays (or flames) going out from the sun. The rays in a drawing of the sun seem to represent that it is dazzling to the eye.

I think this is a clue to the rays going out from the center in the drawing of a star. The star itself is a dimensionless point of light. Nobody sees literal rays when gazing at a star in the sky. The rays in the drawing suggest that the star is dazzling (if bright) or twinkling (if not so bright).

We don’t think of the moon as needing the rays when it is drawn. It is not dazzling, in fact the light it gives varies a great deal with the lunar month.

]]> By: Mark M http://bit-player.org/2011/how-did-the-stars-get-their-points#comment-3883 Mark M Thu, 08 Dec 2011 22:10:31 +0000 http://bit-player.org/?p=1054#comment-3883 I agree with David, inthe past I also found stars to look like points of light, but sadly astigmatism developed over the years. I agree with David, inthe past I also found stars to look like points of light, but sadly astigmatism developed over the years.

]]> By: David Rysdam http://bit-player.org/2011/how-did-the-stars-get-their-points#comment-3882 David Rysdam Thu, 08 Dec 2011 17:42:40 +0000 http://bit-player.org/?p=1054#comment-3882 <i>And that’s what puzzles me, because the stars really do appear to be dimensionless points of light. When I stare at the sky, I see some twinkling going on, but nowhere do I see pentagrams and hexagrams pinned to black velvet, or even the slightest hint of angularity. </i> You must have very good eyesight. Consult an optometrist for reasons why a person might not perceive a dimensionless point as such. And that’s what puzzles me, because the stars really do appear to be dimensionless points of light. When I stare at the sky, I see some twinkling going on, but nowhere do I see pentagrams and hexagrams pinned to black velvet, or even the slightest hint of angularity.

You must have very good eyesight. Consult an optometrist for reasons why a person might not perceive a dimensionless point as such.

]]> By: Chris H http://bit-player.org/2011/how-did-the-stars-get-their-points#comment-3881 Chris H Thu, 08 Dec 2011 17:00:37 +0000 http://bit-player.org/?p=1054#comment-3881 I'm trying to think of how else to describe radiating light. Concentric circles? Once you have a light source with eminating rays, you'll want to simplify your drawing. Four rays looks like a plus sign or t (already taken, perhaps?), so five or six is about right. But why not 3? I’m trying to think of how else to describe radiating light. Concentric circles? Once you have a light source with eminating rays, you’ll want to simplify your drawing. Four rays looks like a plus sign or t (already taken, perhaps?), so five or six is about right. But why not 3?

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