Why Do I Have to Go to Sleep?

Chloe Effron
Chloe Effron

Kids ask a lot of questions.

mental_floss has answers. Today we launch WHY?, our new series for kids and parents. We'll tackle all types of questions children have about how the world works by providing science-based, kid-friendly content. Our answers are written with early readers (ages 4–7) in mind, but we think they're interesting—and educational—for everyone.

Have a question? Send it to why@mentalfloss.com. 

Sleep is a must for all animals, including you. You must sleep to live. When we sleep it may seem like we’re not doing much. But this is when our bodies are busy growing, healing, and learning—especially our brains. They make sense of the lessons, games, words, feelings, and thoughts we had during the day. 


We have something inside our bodies called a circadian (sir-CAY-dee-an) clock that tells our bodies when it’s time to sleep. It’s not a real clock! The circadian clock is a system controlled by neurons, or brain cells, behind your eyes that react to light. This clock tells us to be awake during the day and to go to sleep at night.


Because the human brain evolved before we created electric lights. You’re not reading this on the computer or phone in bed, right? Because that’s a bad idea. The light from the computer tricks your circadian clock into acting like it’s daytime, so you’re not as sleepy. When you stay up late and lose sleep, your brain and body don’t work as well the next day. It’s harder to learn new things, remember old things, and not be cranky. 

For fun further reading, check out MadScieNet's answer to the question, "Do worms sleep?"


10 of the Most Popular Portable Bluetooth Speakers on Amazon

Altech/Bose/JBL/Amazon
Altech/Bose/JBL/Amazon

As convenient as smartphones and tablets are, they don’t necessarily offer the best sound quality. But a well-built portable speaker can fill that need. And whether you’re looking for a speaker to use in the shower or a device to take on a long camping trip, these bestselling models from Amazon have you covered.

1. OontZ Angle 3 Bluetooth Portable Speaker; $26-$30 (4.4 stars)

Oontz portable bluetooth speaker
Cambridge Soundworks/Amazon

Of the 57,000-plus reviews that users have left for this speaker on Amazon, 72 percent of them are five stars. So it should come as no surprise that this is currently the best-selling portable Bluetooth speaker on the site. It comes in eight different colors and can play for up to 14 hours straight after a full charge. Plus, it’s splash proof, making it a perfect speaker for the shower, beach, or pool.

Buy it: Amazon

2. JBL Charge 3 Waterproof Portable Bluetooth Speaker; $110 (4.6 stars)

JBL portable bluetooth speaker
JBL/Amazon

This nifty speaker can connect with up to three devices at one time, so you and your friends can take turns sharing your favorite music. Its built-in battery can play music for up to 20 hours, and it can even charge smartphones and tablets via USB.

Buy it: Amazon

3. Anker Soundcore Bluetooth Speaker; $25-$28 (4.6 stars)

Anker portable bluetooth speaker
Anker/Amazon

This speaker boasts 24-hour battery life and a strong Bluetooth connection within a 66-foot radius. It also comes with a built-in microphone so you can easily take calls over speakerphone.

Buy it: Amazon

4. Bose SoundLink Color Bluetooth Speaker; $129 (4.4 stars)

Bose portable bluetooth speaker
Bose/Amazon

Bose is well-known for building user-friendly products that offer excellent sound quality. This portable speaker lets you connect to the Bose app, which makes it easier to switch between devices and personalize your settings. It’s also water-resistant, making it durable enough to handle a day at the pool or beach.

Buy it: Amazon

5. DOSS Soundbox Touch Portable Wireless Bluetooth Speaker; $28-$33 (4.4 stars)

DOSS portable bluetooth speaker
DOSS/Amazon

This portable speaker features an elegant system of touch controls that lets you easily switch between three methods of playing audio—Bluetooth, Micro SD, or auxiliary input. It can play for up to 20 hours after a full charge.

Buy it: Amazon

6. Altec Lansing Mini Wireless Bluetooth Speaker; $15-$20 (4.3 stars)

Altec Lansing portable bluetooth speaker
Altec Lansing/Amazon

This lightweight speaker is built for the outdoors. With its certified IP67 rating—meaning that it’s fully waterproof, shockproof, and dust proof—it’s durable enough to withstand harsh environments. Plus, it comes with a carabiner that can attach to a backpack or belt loop.

Buy it: Amazon

7. Tribit XSound Go Bluetooth Speaker; $33-$38 (4.6 stars)

Tribit portable bluetooth speaker
Tribit/Amazon

Tribit’s portable Bluetooth speaker weighs less than a pound and is fully waterproof and resistant to scratches and drops. It also comes with a tear-resistant strap for easy transportation, and the rechargeable battery can handle up to 24 hours of continuous use after a full charge. In 2020, it was Wirecutter's pick as the best budget portable Bluetooth speaker on the market.

Buy it: Amazon

8. VicTsing SoundHot C6 Portable Bluetooth Speaker; $18 (4.3 stars)

VicTsing portable bluetooth speaker
VicTsing/Amazon

The SoundHot portable Bluetooth speaker is designed for convenience wherever you go. It comes with a detachable suction cup and a carabiner so you can keep it secure while you’re showering, kayaking, or hiking, to name just a few.

Buy it: Amazon

9. AOMAIS Sport II Portable Wireless Bluetooth Speaker; $30 (4.4 stars)

AOMAIS portable bluetooth speaker
AOMAIS/Amazon

This portable speaker is certified to handle deep waters and harsh weather, making it perfect for your next big adventure. It can play for up to 15 hours on a full charge and offers a stable Bluetooth connection within a 100-foot radius.

Buy it: Amazon

10. XLEADER SoundAngel Touch Bluetooth Speaker; $19-$23 (4.4 stars)

XLeader portable bluetooth speaker
XLEADER/Amazon

This stylish device is available in black, silver, gold, and rose gold. Plus, it’s equipped with Bluetooth 5.0, a more powerful technology that can pair with devices up to 800 feet away. The SoundAngel speaker itself isn’t water-resistant, but it comes with a waterproof case for protection in less-than-ideal conditions.

Buy it: Amazon

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The Meteoric Rise—and Tragic Fall—of NASA's Skylab

NASA // Public Domain
NASA // Public Domain

On May 14, 1973, NASA launched Skylab, the first American space station. It fell to earth six years later, burning up in the atmosphere on July 11, 1979.

Skylab itself was a heavily modified third stage of a Saturn V rocket—the same system we used to send Apollo missions to the moon. The station was huge, measuring more than 80 feet in length, with a 21-foot diameter. During launch, Skylab 1 suffered major damage to its solar array, which delayed the launch of the Skylab 2 crew (originally intended to launch the day after Skylab itself reached orbit). The Skylab 2 mission was modified to include repair work to the solar power system and installation of a solar heat shield, as the original one was lost during launch. The Skylab 2 crew launched on May 25, 1973.

The Skylab missions resulted in new information about long-term space habitation (including an awesome space shower). The first crew spent 28 days in space; the second crew more than doubled that at 59 days; and the final crew (Skylab 4) spent 84 days up there. That last record was not broken by an American for two decades. Skylab also focused on solar science, Earth science, and microgravity experiments.

Skylab was something of a bridge between the Apollo and Space Shuttle programs. Indeed, Skylab was supposed to be serviced (and its orbit boosted) by the first Shuttle, but it wasn't ready in time. Skylab's orbit decayed, eventually causing it to disintegrate and fall to Earth over the Indian Ocean on July 11, 1979. Chunks of the station made a bit of a fireworks display streaking through the atmosphere, and ultimately littered a swath of Australia. No injuries were reported from the falling debris, though media coverage of the reentry was intense.

Here's a short NASA documentary on Skylab, explaining the story of the station. Have a look:

If you'd like to relive the launch, here's live TV coverage from that day:

And if you'd like to learn more about its crash, and what it taught NASA moving forward, watch this:

This story has been updated for 2020.