23 May 00:00

Tatooine Rainbow

by xkcd

Tatooine Rainbow

Since rainbows are caused by the refraction of the sunlight by tiny droplets of rainwater, what would rainbow look like on Earth if we had two suns like Tatooine?

—Raga

A planet with double suns would have double rainbows.

Or rather, quadruple rainbows. Our rainbows here on Earth are already double rainbows—there's a second, fainter bow above the main one. You can't always see this second rainbow, since the clouds need to be just right, so people get excited when they see one.

The area between the two rainbows is darker than the area outside because raindrops reflect light more strongly in certain directions. That region has a name, by the way—it's called Alexander's dark band.

The first and second rainbows are the only ones you can see easily, but there are actually many more bows beyond those two, each one fainter than the last. Rainbows are formed by light bouncing around in raindrops, and the different bows are formed by different paths the light can take. The main rainbow is formed by the most common paths through the droplet, and other paths—where some of the light bounces around in more unusual ways—make the fainter second, third, fourth, and even fifth rainbows.

Usually, only the first and second rainbows are bright enough to see; it was only in the last five years that anyone took pictures of the third, fourth, and fifth rainbows.

Rainbows appear on the other side of the sky from the Sun, so to figure out what a double rainbow would look like on a planet with two suns, we need to figure out where the suns usually appear in the sky on that kind of planet.

There are planets with two suns out there, although we didn't know that for sure until recently. Double-star planets come in two main varieties:

In the first kind of system, the two stars are close together and the planet goes around them far away. This kind of planet is called a circumbinary planet. In the second kind of system, the two stars are farther apart, and the planet orbits one of them[1]Not necessarily the bigger one. while the other stays far away. This kind of planet is called [the other kind of planet].[2]I'm sorry, I've just never learned a good word for these.

If you lived on [the other kind of planet],[3]Sorry. the two Suns would spend most of the year in different parts of the sky. Depending on how big they were, they may also be very different in brightness. If you were orbiting the larger star, the smaller one might be no brighter than the Moon,[4]Which would still be bright enough to cast a rainbow! or even look like an ordinary planet or star.

Tatooine, in Star Wars, looks like it's probably a circumbinary planet. The two stars appear pretty close together in the sky and similar in color and size, so it seems reasonable to guess they're actually near one another, with Tatooine orbiting both of them. Two suns would create two overlapping rainbows. The main bow of the rainbow is a circle about 84 degrees across, centered in the sky exactly opposite the Sun.[5]This is why you never see more than half of a rainbow above the horizon. If the center of the rainbow were above the horizon, it would mean the Sun was below it behind you, so there wouldn't be sunlight to make a rainbow in the first place. The farther apart the two suns were, the farther apart the rainbows would be. If the two suns were 84 degrees apart, the main bows of the two rainbows would barely touch.

A pair of suns 84 degrees apart would be possible around [the other kind of planet], but not around Tatooine-type[6]If Star Wars had just used the other kind of planet, we could use its name for them and solve this problem. circumbinary planets. The reason is simple: A planet orbiting two stars can't get too close to them or its orbit becomes unstable. If it gets too close, the irregular tugging from the gravity of the two stars as they orbit will eventually cause the planet to crash into one of them or get flung out of the system.

For a system with two similar-sized stars, this "critical radius" is around six times the distance between the two stars.[7]This is a very rough number; it can range from four to eight depending on the exact arrangement. We've found a lot of planets close to that critical radius, which suggests that maybe they slowly migrate inward until they reach it and are ejected or destroyed. Strangely, we haven't found many big Jupiter-sized planets around binary stars in general; we should be seeing them if they're there, so the lack of them is a mystery. This means that the two suns would never get more than about 20 degrees apart in the sky:

This tells us that the two rainbows in a Tatooine-like system would always overlap.[8]Assuming the raindrops are made of water, or something with similar refractive properties. The colors would blend together where the bows crossed, and the dark bands would too.

I suppose doubling all the rainbows would also double the number of pots of gold at the end of each rainbow.[9]Come to think of it, do our rainbows have one pot of gold or two? I've never really thought about it. And it's not just pots of gold; I guess we'd need to rethink all kinds of rainbow references.

Overlapping rainbows would be beautiful, but definitely a lot more complicated.

22 May 13:53

Offering

http://oglaf.com/offering/

23 May 05:00

Comic for 2016.05.23

New Cyanide and Happiness Comic
24 May 05:00

Comic for 2016.05.24

New Cyanide and Happiness Comic
23 May 04:00

Rainbow

Listen, in a few thousand years you'll invent a game called 'SimCity' which has a 'disaster' button, and then you'll understand.
23 May 15:56

almond rhubarb picnic bars

by deb

almond rhubarb picnic bars

One of the primary pieces of advice my grandmother imparted on me — besides the fact that she thought I should be a writer, an absurd idea I promptly ignored — was that one should always leave the house looking the best they can. I realize this might sound a little old-fashioned and possibly even oppressive — I Exist As More Than A Decorative Object, thankyouverymuch — but I took it to heart nonetheless because I know she didn’t mean high heels and rollers, but mostly that looking more with it than you might actually feel sometimes can trick you too.

quick buttery cookie base
pressed-in crust

I apply it in the kitchen as well. Thus, while if we’re being completely honest, life is currently a swarm of getting recipes ready for the next book (eee!), a to-do list for this month as long as the remainder of this year, kids waking up way too early, mama going to bed too late, an apartment that has yet to clean itself and let’s not even talk about what’s going on in the produce drawer — i.e. real life, and not even a bad one — rather than dwelling on the chaos, I think we should cook for the life we want, not for the life we have. Thus: I choose picnic bars.

ready to grind

... Read the rest of almond rhubarb picnic bars on smittenkitchen.com


© smitten kitchen 2006-2012. | permalink to almond rhubarb picnic bars | 4 comments to date | see more: Bars, Cookie, Photo, Picnics, Rhubarb, Spring

23 May 00:00

Rainbow

Listen, in a few thousand years you'll invent a game called 'SimCity' which has a 'disaster' button, and then you'll understand.
25 May 05:00

Comic for 2016.05.25

New Cyanide and Happiness Comic
23 May 05:07

Comic for May 23, 2016

Dilbert readers - Please visit Dilbert.com to read this feature. Due to changes with our feeds, we are now making this RSS feed a link to Dilbert.com.
23 May 18:51

VG Cats : Bat Beach Bod

24 May 05:01

Comic for May 24, 2016

Dilbert readers - Please visit Dilbert.com to read this feature. Due to changes with our feeds, we are now making this RSS feed a link to Dilbert.com.
23 May 07:12

Comic: Invasive Species

by Tycho@penny-arcade.com (Tycho)
New Comic: Invasive Species
23 May 04:56

Nickel-Catalyzed Alkylative Cross-Coupling of Anisoles with Grignard Reagents via C–O Bond Activation

by Mamoru Tobisu, Tsuyoshi Takahira, Toshifumi Morioka and Naoto Chatani

TOC Graphic

Journal of the American Chemical Society
DOI: 10.1021/jacs.6b03253
23 May 06:35

Trifluoromethylation of Arylsilanes with [(phen)CuCF3]

by Johannes Morstein, Haiyun Hou, Chen Cheng, John F. Hartwig

Abstract

A method for the trifluoromethylation of arylsilanes is reported. The reaction proceeds with [(phen)CuCF3] as the CF3 source under mild, oxidative conditions with high functional-group compatibility. This transformation complements prior trifluoromethylation of arenes in several ways. Most important, this method converts arylsilanes formed by the silylation of aryl C−H bonds to trifluoromethylarenes, thereby allowing the conversion of arenes to trifluoromethylarenes. The unique capabilities of the reported method are demonstrated by the conversion of a C−H bond into a C−CF3 bond in active pharmaceutical ingredients which do not undergo this overall transformation by alternative functionalization processes, including a combination of borylation and trifluoromethylation.

Thumbnail image of graphical abstract

All about the source: The first trifluoromethylation of arylsilanes occurs with [(phen)CuCF3] as the CF3 source and AgF as the activator under mild, oxidative conditions; the choice of both reagents was shown to be crucial for the reported transformation. The method shows high functional-group compatibility, and late-stage functionalization of active pharmaceutical ingredients is possible. DMF=N,N-dimethylformamide, phen=9,10-phenanthroline.

22 May 22:00

Do These Three Exercises in Four Minutes to Improve Your Hunched Posture

by Mihir Patkar

Sitting in front of a screen all day can wreak havoc on the spine. Our posture changes, and that can cause some serious long-term damage. Dr. Eric Goodman, creator of the Foundation Training program, offers these three no-equipment exercises to help.

Read more...

23 May 07:00

Chapter 58: Page 16

Get a job.
23 May 04:00

Girl Genius for Monday, May 23, 2016

The Girl Genius comic for Monday, May 23, 2016 has been posted.
23 May 07:12

Comic: Invasive Species

by Tycho@penny-arcade.com (Tycho)
New Comic: Invasive Species
25 May 04:00

Patch

My optimizer uses content-aware inpainting to fill in all the wasted whitespace in the code, repeating the process until it compiles.
22 May 16:21

It did get my attention, though.

by thebloggess
So I saw this truck driving down the road and I thought, “Wait.  Seriously?  Is it just me?” And apparently it was, because no one else seemed to care.  Victor said that he got it, but that it would really … Continue reading →
23 May 15:01

Saturday Morning Breakfast Cereal - Fandom

by admin@smbc-comics.com

Hovertext: That said, if anyone DOES want to give me a million dollars to fail to make this product...


New comic!
Today's News:

Vote Trillarsandjohnstein 2016!

24 May 18:00

Guy Messages Friends as He Sabotages Terrible Date Who Refuses to Put Her Phone Down

list,gifs,friends,texting,disaster date,dating

When one dude's date turns out to be a complete (texting) trainwreck, this guy was gifted with some solid advice from his bros on how to make the most out of the situation.

What happens next is a series of moves that, if followed correctly, should be able to help anyone get out of a disaster date.

Submitted by:

23 May 06:35

Large-Scale Synthesis of Highly Luminescent Perovskite-Related CsPb2Br5 Nanoplatelets and Their Fast Anion Exchange

by Kun-Hua Wang, Liang Wu, Lei Li, Hong-Bin Yao, Hai-Sheng Qian, Shu-Hong Yu

Abstract

All-inorganic cesium lead-halide perovskite nanocrystals have emerged as attractive optoelectronic nanomaterials owing to their stabilities and highly efficient photoluminescence. Herein we report a new type of highly luminescent perovskite-related CsPb2Br5 nanoplatelets synthesized by a facile precipitation reaction. The layered crystal structure of CsPb2Br5 promoted an anisotropic two-dimensional (2D) crystal growth during the precipitation process, thus enabling the large-scale synthesis of CsPb2Br5 nanoplatelets. Fast anion exchange has also been demonstrated in as-synthesized CsPb2Br5 nanoplatelets to extend their photoluminescence spectra to the entire visible spectral region. The large-scale synthesis and optical tunability of CsPb2Br5 nanoplatelets will be advantageous in future applications of optoelectronic devices.

Thumbnail image of graphical abstract

The fast and the luminous: A new type of highly luminescent cesium lead halide nanoplatelets show fast anion exchange. Fast anion exchange in the as-synthesized CsPb2Br5 nanoplatelets has also been demonstrated to extend their photoluminescence spectra to the entire visible spectral region of 410 nm–670 nm.

23 May 06:21

Synthesis of Five-Porphyrin Nanorings by Using Ferrocene and Corannulene Templates

by Pengpeng Liu, Yutaka Hisamune, Martin D. Peeks, Barbara Odell, Juliane Q. Gong, Laura M. Herz, Harry L. Anderson

Abstract

The smallest and most strained member of a family of π-conjugated cyclic porphyrin oligomers was synthesized by using pentapyridyl templates based on ferrocene and corannulene. Both templates are effective for directing the synthesis of the butadiyne-linked cyclic pentamer, despite the fact that the radii of their N5 donor sets are too small by 0.5 Å and 0.9 Å, respectively (from DFT calculations). The five-porphyrin nanoring exhibits a structured absorption spectrum and its fluorescence extends to 1200 nm, reflecting strong π conjugation and Herzberg–Teller vibronic coupling.

Thumbnail image of graphical abstract

Strained to making point: Two templates were tested for their ability to direct the formation of a π-conjugated cyclic porphyrin pentamer. 1,3,5,7,9-penta(4-pyridyl)corannulene was found to be more effective than a ferrocene-based template, despite the fact that the radius of its N5 ligand set is almost 1 Å too small to fit the cavity of the nanoring.

24 May 14:56

Saturday Morning Breakfast Cereal - Reverse Captcha

by admin@smbc-comics.com

Hovertext: Also, you can tell humans from replicants, because a human will literally walk 10 miles to use an elevator instead of stairs.


New comic!
Today's News:

 I'm doing a guest series over at Drive!