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28 minutes ago, Dillon Levenque said:

The effect in the SpaceX launch is a combination of things. The primary condition is that launch happens close enough after sundown from the observer's position, so the observer is in Earth's shadow but the rocket's in sunlight.

Yep. Here's a shuttle launch photo (Atlantis - Feb 7, 2001) that was the subject of much discussion during my waning days on the sci.astro.amateur usenet group...

Atlantis_launch_plume_edit.jpg

The launch was shortly after sundown, so the bottom of the plume is in the Earth's shadow. The top is still directly illuminated by sunlight and the plume's shadow (anticrepuscular ray or anti-sunbeam) can be seen pointing directly to the nearly full moon that's just as nearly opposite the sun. You can also see the Earth's shadow rising from the horizon, above which the sky is pink-orange from sunlight filtering through the atmosphere behind the camera. The sky at higher elevation is illuminated by sunlight taking a much shorter path through the atmosphere, so there's still plenty of blue light to scatter. I've no idea what to call the color that's between the pink-orange and the blue, but I think it's the prettiest color on above Earth.

If you've ever been on a prominent mountain peak during sunrise/sunset, you may have noticed the shadow of the mountain in the sky...

teideshadow_casado_2000.jpg

 

Edited by Madelaine McMasters
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3 hours ago, Rhonda Huntress said:

I have always wanted to watch a night launch.

This reminds me of my second skydive where tons of things went wrong and we ended up getting the thrill of a night dive.  It was totally super cool looking at the city at night while floating down.

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5 minutes ago, Clover Jinx said:

Good grief I can't even derail a derail thread. *mumbles to herself as she goes to look for catnip*

But Clover, that's kinda the point. Derails don't derail this thread, they ARE this thread. Besides, you derail a thread just by appearing in it, much as they used to say Bogart would dominate a scene just by entering it.

Edited by Dillon Levenque
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It was definitely a thrill and definitely scary as hell.  My husband took me skydiving for our second date.  On the first dive, I cussed so much right before leaving the airplane that the guy I was strapped to -- so wonderfully tight that you could not have slid a paper between his crotch and my a$$ -- anyway, he said that I "did a sailor proud".  I don't even remember cussing up a storm.

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I'm between White Sands Missile Range and Vandenberg AFB. If the launches go high enough over the horizon at sunrise or sunset (see previous post), it's an unbelievable sight to behold. As I am typing, Vandenberg is prepping a launch for a NROL-47. They're at a minus 4 minute hold for now, something to do with a swing arm not working properly. Some on Twitter are wishing a sunset launch to replicate the last lift off.

Download video

 

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18 hours ago, Dillon Levenque said:

The lighthouse has a very interesting history as sketched here: https://en.wikipedia.org/wiki/Eddystone_Lighthouse

Rather than let the Eddystone Light get merely one derail comment, although a stirring one, I feel obliged to expand on the meager bit of information that's in that Wikipedia article. From a chemist's perspective, the thing that's most interesting about the Eddystone Light is that it marked the rediscovery of pozzolanic cements ( a variety of which you may know as Portland cement). Pozzolanic cements were invented by the Romans, probably serendipidously, almost 2 millenia earlier.  They made use of volcanic ash as an additive to the calcined limestone that was the primary chemical component in their cement. The ash created a mix that set quite rapidly and could be used in underwater construction projects. Many of the best Roman structures still standing today were held together by those pozzolanic cements.  Sadly, though, the Roman formula was forgotten as the empire fell apart. It wasn't until the Eddystone Light project ( Smeaton's 1756 version) that British engineers finally stumbled on it.  It proved to be such a smashing success that it became the standard for modern cements.  (The fact that Smeaton's lighthouse collapsed a hundred years later was not the fault of the cement, BTW, but of wave erosion.)

I do not know why Burl Ives did not see fit to mention any of this instead of railing on about porpoises and porgies.  However, to convey the significance of this achievement of ancient/modern chemistry, I did once deliver my own a capella rendition of the Eddystone Light ballad to a spellbound class of freshmen.   They were -- in a word -- stupified.

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32 minutes ago, Rolig Loon said:

I do not know why Burl Ives did not see fit to mention any of this instead of railing on about porpoises and porgies.

When I finally stop laughing about that line, I may have to go back and edit in the word "some" into that sentence concerning the "Wave to Saturn" deal, about scientists having a sense of whimsy. :-)

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Damn, I went to the wrong university, Rolig.

It's so easy to take for granted something as ubiquitous as Portland cement, but it really is amazing stuff and the history of such things is usually pretty interesting. I was fascinated by plaster of Paris and mortar when I was young (okay, still am). Adding half a cup of water to a package of Martha White lemon poppy muffin mix, forgetting it's baking in the oven, and returning to something that's figuratively hard as a rock isn't as magical as adding half a cup of water to pre-baked gypsum or limestone and getting something literally as hard as a rock.

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33 minutes ago, Madelaine McMasters said:

adding half a cup of water to pre-baked gypsum or limestone and getting something literally as hard as a rock.

From a geologist's perspective (or in this case that of an avid student of geology) it literally IS a rock; adding the water just restores what was extracted from the rock in the baking process.

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