Comments on: Comments on 5899

Post number 5899

aflakete — Mon, 19 Feb 2001 07:52:13 -0800

This picture of the Space Shuttle and the ray of "shadow" from the moon is pretty cool. I even think I buy the explanation.

By: Steven Den Beste

Steven Den Beste — Mon, 19 Feb 2001 08:09:42 -0800

Actually, this is the correct link.

By: ericost

ericost — Mon, 19 Feb 2001 08:50:21 -0800

Wish they could have made that image a jpg instead of a gif.

By: tomalak

tomalak — Mon, 19 Feb 2001 09:11:24 -0800

Well the first picture is a JPG and if you click on it then you get the GIF. Not sure if I'm missing something...

By: ericost

ericost — Mon, 19 Feb 2001 09:16:44 -0800

Yeah, you are right Lawrence. And if you look closely, both the jpg and the gif suffer from gif dithering and jpeg compression artifacts. The worst of both worlds!

By: Tubes

Tubes — Mon, 19 Feb 2001 09:17:02 -0800

I don't understand why the shadow appears to be of one isolated object, rather than of the whole twisty smoke trail... What am I missing?

By: amanda

amanda — Mon, 19 Feb 2001 09:25:35 -0800

I'm puzzled, too, Tubes... it's doesn't look like the plume's shadow -- it looks like something wholly different.

By: Markb

Markb — Mon, 19 Feb 2001 09:26:18 -0800

And isn't the shadow being cast into thin air? I thought a shadow had to fall onto something solid or reflective for the absence of light rays to be seen. Or is the amount of pollution/particulates in the atmosphere enough to produce this? I think I'm missing something too (a decent physics education for one thing, obviously....). Steven, you're usually good at explaining these things, would you mind helping out here?

By: amanda

amanda — Mon, 19 Feb 2001 09:42:10 -0800

I think particulates in the air can produce shadows... if you've ever been to a club or theatre that is using a fog machine then you would see shadows created and light distorted.

By: iblog

iblog — Mon, 19 Feb 2001 09:59:39 -0800

Markb, you asked: And isn't the shadow being cast into thin air? I thought a shadow had to fall onto something solid or reflective for the absence of light rays to be seen. This shadow is similar to the Sun rays you see through clouds, usually near sunrise or sunset. These rays appear to diverge, or spread out, as they get farther from the source. Actually, they are parallel rays, but they appear to diverge in the same way that train tracks appear to converge in the distance. On some days these rays make it all the way across the sky, and begin to converge again on the other side - kind of an eerie thing when you see it. But since the rays are actually parallel, it makes sense (the train tracks again). So, the shadow from the plume is similar to the rays you see from the sun (which are actually defined by the shadows of the clouds they are poking through). And Tubes asked: I don't understand why the shadow appears to be of one isolated object, rather than of the whole twisty smoke trail... What am I missing? Again this has to do with perspective. The plume passes out of the shadow of the earth right where it gets a yellow cast to it. The shadow can be seen faintly just under this part of the plume. If you look carefully, it is spread out. But then it converges rapidly toward the full moon (which is directly opposite the sun at this point). Spectacular concurrence of events!

By: Tubes

Tubes — Mon, 19 Feb 2001 10:26:39 -0800

Thanks iblog - I missed the fact that most of the plume was below the level of sunlight. Makes sense now! This must have been spectacular in person. I've taken photos of beautiful and eerie cloud formations and weather conditions, and the photos never do justice to the reality.

By: iblog

iblog — Mon, 19 Feb 2001 10:58:26 -0800

Tubes: No problem - I used to be a science teacher. I love stuff like this, and can't resist the urge to share... I'm just glad it was understandable. And yeah, it must have been spectacular in person!

By: Steven Den Beste

Steven Den Beste — Mon, 19 Feb 2001 12:15:43 -0800

I feel like Sergeant Dietrich. It's a good thing iblog had an answer because I don't.

By: gimli

gimli — Mon, 19 Feb 2001 12:35:29 -0800

Occasionally, the vapor trails of jets cast shadows similar to this, but not nearly as spectacular.

By: Princess Buttercup

Princess Buttercup — Mon, 19 Feb 2001 13:52:35 -0800

From my front yard where I view the majority of lauches, I was lined up with the plume directly in front of me with the sun off to the left and the moon to the right. It was PERFECT!!! I didn't see the shadow from my perspective, however what I did see was the plume with a rainbow effect. That was the thing the people around here spoke about was the rainbow. I didn't even know about the shadow until today!! This pic is now my wallpaper!

By: iblog

iblog — Mon, 19 Feb 2001 14:51:04 -0800

I feel like Sergeant Dietrich. It's a good thing iblog had an answer because I don't. That's funny, I kind of look like Sergeant Dietrich...