Why Is the Sky Blue?

March 2, 2018

Light is made up of waves of different sizes called wavelengths. The short waves look blue. Our atmosphere is like a blanket made up of gases and particles that wraps around the Earth. When sunlight hits our atmosphere, the light waves scatter in all directions … especially the short blue ones.

We see different wavelengths as different colors. Sunlight looks white, but it’s really every color of the rainbow. Bigger, longer waves look red to us. Smaller, shorter waves look blue, as you know. We can’t see these different colors until something bends light (like a prism), reflects it (like a mirror), absorbs it (like red sneakers) or scatters it (like the atmosphere). Since shorter waves are easier for the atmosphere to scatter, the sky looks blue.

Our eyes can only see a few of the colors in the entire universe, and sky blue is one of them! The colors we can see are called visible light. But most light in the universe is invisible to our eyes. It shines at wavelengths we can’t see without special instruments. These other wavelengths include gamma rays, X-rays, ultraviolet radiation, infrared radiation, microwaves, and radiowaves.

For fun further reading, check out NASA's answer to this classic question. It features helpful illustrations.

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Holiday Gift Guides

Take Advantage of Amazon's Early Black Friday Deals on Tech, Kitchen Appliances, and More

BY Smart Shopping Team

November 6, 2020

(Updated: November 23, 2020)

This article contains affiliate links to products selected by our editors. Mental Floss may receive a commission for purchases made through these links.

Even though Black Friday is still a few days away, Amazon is offering early deals on kitchen appliances, tech, video games, and plenty more. We will keep updating this page as sales come in, but for now, here are the best Amazon Black Friday sales to check out.

Kitchen

- Instant Pot Duo Plus 9-in-115 Quart Electric Pressure Cooker; $90 (save $40)

- Le Creuset Enameled Cast Iron Signature Sauteuse 3.5 Quarts; $180 (save $120)

- KitchenAid KSMSFTA Sifter with Scale Attachment; $95 (save $75)

- Keurig K-Mini Coffee Maker; $60 (save $20)

- Cuisinart Bread Maker; $88 (save $97)

- Anova Culinary Sous Vide Precision Cooker; $139 (save $60)

- Aicook Juicer Machine; $35 (save $15)

- JoyJolt Double Wall Insulated Espresso Mugs - Set of Two; $14 (save $10)

- Longzon Silicone Stretch Lids - Set of 14; $13 (save $14)

- HadinEEon Milk Frother; $37 (save $33)

Home Appliances

- iRobot Roomba 675 Robot Vacuum with Wi-Fi Connectivity; $179 (save $101)

- Fairywill Electric Toothbrush with Four Brush Heads; $19 (save $9)

- ASAKUKI 500ml Premium Essential Oil Diffuser; $22 (save $4)

- Facebook Portal Smart Video Calling 10 inch Touch Screen Display with Alexa; $129 (save $50)

- Bissell air320 Smart Air Purifier with HEPA and Carbon Filters; $280 (save $50)

- Oscillating Quiet Cooling Fan Tower; $59 (save $31)

- TaoTronics PTC 1500W Fast Quiet Heating Ceramic Tower; $55 (save $10)

- Vitamix 068051 FoodCycler 2 Liter Capacity; $300 (save $100)

- AmazonBasics 8-Sheet Home Office Shredder; $33 (save $7)

- Ring Video Doorbell; $70 (save $30)

Video games

- Legend of Zelda Link's Awakening for Nintendo Switch; $40 (save $20)

- Marvel's Spider-Man: Game of The Year Edition for PlayStation 4; $20 (save $20)

- Marvel's Avengers; $27 (save $33)

- Minecraft Dungeons Hero Edition for Nintendo Switch; $20 (save $10)

- The Last of Us Part II for PlayStation 4; $30 (save $30)

- LEGO Harry Potter: Collection; $15 (save $15)

- Ghost of Tsushima; $40 (save $20)

- BioShock: The Collection; $20 (save $30)

- The Sims 4; $20 (save $20)

- God of War for PlayStation 4; $10 (save $10)

- Days Gone for PlayStation 4; $20 (save $6)

- Luigi's Mansion 3 for Nintendo Switch; $40 (save $20)

Computers and tablets

- Apple MacBook Air 13 inches with 256 GB; $899 (save $100)

- New Apple MacBook Pro 16 inches with 512 GB; $2149 (save $250)

- Samsung Chromebook 4 Chrome OS 11.6 inches with 32 GB; $210 (save $20)

- Microsoft Surface Laptop 3 with 13.5 inch Touch-Screen; $1200 (save $400)

- Lenovo ThinkPad T490 Laptop; $889 (save $111)

- Amazon Fire HD 10 Tablet (64GB); $120 (save $70)

- Amazon Fire HD 10 Kids Edition Tablet (32 GB); $130 (save $70)

- Samsung Galaxy Tab A 8 inches with 32 GB; $100 (save $50)

- Apple iPad Mini (64 GB); $379 (save $20)

- Apple iMac 27 inches with 256 GB; $1649 (save $150)

- Vankyo MatrixPad S2 Tablet; $120 (save $10)

Tech, gadgets, and TVs

- Apple Watch Series 3 with GPS; $179 (save $20)

- SAMSUNG 75-inch Class Crystal 4K Smart TV; $998 (save $200)

- Apple AirPods Pro; $199 (save $50)

- Nixplay 2K Smart Digital Picture Frame 9.7 Inch Silver; $238 (save $92)

- All-New Amazon Echo Dot with Clock and Alexa (4th Gen); $39 (save $21)

- MACTREM LED Ring Light 6" with Tripod Stand; $16 (save $3)

- Anker Soundcore Upgraded Bluetooth Speaker; $22 (save $8)

- Amazon Fire TV Stick with Alexa Voice Remote; $28 (save $12)

- Canon EOS M50 Mirrorless Camera with EF-M 15-45mm Lens; $549 (save $100)

- DR. J Professional HI-04 Mini Projector; $93 (save $37)

Sign Up Today: Get exclusive deals, product news, reviews, and more with the Mental Floss Smart Shopping newsletter!

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MF Explains It All

The Great Tryptophan Lie: Eating Turkey Does Not Make You Tired

BY Ellen Gutoskey

November 12, 2019

(Updated: November 25, 2020)

H. Armstrong Roberts/iStock via Getty Images

While you’re battling your kids for the best napping spot after Thanksgiving dinner, feel free to use this as a diversion tactic: It’s a myth that eating turkey makes you tired.

It’s true that turkey contains L-Tryptophan, an amino acid involved in sleep. Your body uses it to produce a B vitamin called niacin, which generates the neurotransmitter serotonin, which yields the hormone melatonin, which helps regulate your sleeping patterns. However, plenty of other common foods contain comparable levels of tryptophan, including other poultry, meat, cheese, yogurt, fish, and eggs.

Furthermore, in order for tryptophan to produce serotonin in your brain, it first has to make it across the blood-brain barrier, which many other amino acids are also trying to do. To give tryptophan a leg up in the competition, it needs the help of carbohydrates. Registered dietitian Elizabeth Somer told WebMD that the best way to boost serotonin is to eat a small, all-carbohydrate snack a little while after you’ve eaten something that contains tryptophan, and the carbs will help ferry the tryptophan from your bloodstream to your brain.

But Thanksgiving isn’t exactly about eating small, well-timed snacks. It’s more about heaps of mashed potatoes, mountains of stuffing, and generous globs of gravy—and that, along with alcohol, is more likely the reason you collapse into a spectacular food coma after your meal. Overeating (especially of foods high in fat) means your body has to work extra hard to digest everything. To get the job done, it redirects blood to the digestive system, leaving little energy for anything else. And since alcohol is a central nervous system depressant, it also slows down your brain and other organs.

In short, you can still hold turkey responsible for your Thanksgiving exhaustion, but you should make sure it knows it can share the blame with the mac and cheese, spiked apple cider, and that second piece of pumpkin pie.

[h/t WebMD]

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