Why Does It Rain?

Chloe Effron
Chloe Effron

WHY? is our attempt to answer all the questions every little kid asks. Do you have a question? Send it to why@mentalfloss.com.

All around you, in the air you breathe and in the sky above you, water hangs out in a form called vapor (VAY-purr). The amount of water vapor in the air is called humidity (hu-MID-it-ee). Every cloud in the sky is made from this vapor, from the big white fluffy ones to the dark gray heavy ones. These are the ones that rain.


Warm air can hold more water vapor than cold air. Warm air also rises, or goes up. And cold air can push warm air up. As these tiny drops of water fly high into the sky, they gather together in clumps and form clouds. 


When enough of this water vapor gathers together in a cloud and then cools down, it gets very heavy and forms droplets called condensation (CON-den-SAY-shun). This is when gravity takes over. Gravity is the force that holds you, your house, and all the animals onto the Earth so we don’t float off into space. With clouds, gravity pulls the water droplets out of the sky, and they fall as rain. If the air is cold enough, those raindrops can become ice crystals. Then they fall as snow, sleet, or hail instead of rain. 

To learn more about rain, visit Easy Science for Kids. 

Human Body Temperatures Are Dropping, and Science Might Know Why

dcdp/iStock via Getty Images
dcdp/iStock via Getty Images

In 1868, German physician Carl Reinhold August Wunderlich started to popularize what’s become the most recognizable number in all of medicine: 98.6°F or 37°C, which is thought to be the normal average human body temperature. Though his methods later came under scrutiny—Wunderlich stuck an enormous thermometer under the armpits of patients for 20 minutes, a less-than-accurate technique—this baseline has helped physicians identify fevers as well as abnormally low body temperatures, along with corresponding illnesses or diseases.

More than 150 years later, 98.6° may no longer be the standard. Humans seem to be getting cooler. Researchers at Stanford University School of Medicine, in a paper published in the journal eLife, compared three large datasets from different time periods: American Civil War records, a national health survey from the 1970s, and a Stanford database from 2007-2017. By comparing recorded body temperatures, the researchers founds that men are now averaging a temperature .58°C less than what's long been considered normal, while women are .32°C lower. On average, each has decreased roughly .03°C every decade since the 1860s.

What drove us to chill out? Scientists have a few theories. A number of advances in human comfort have been ushered in since the 1800s, including better hygiene and readily available food, which may have slowed our metabolic rate (temperature is an indication of that rate). Chronic inflammation, which also raises body temperature, has decreased with the advent of vaccines, antibiotics, and better healthcare. The researchers propose that, on average, our bodies are healthier and slightly less warm.

After all, the average life expectancy in Wunderlich’s era was just 38 years.

[h/t The Independent]

You Should Never Put Batteries In Your ‘Junk’ Drawer. Here’s Why

naumoid/iStock via Getty Images
naumoid/iStock via Getty Images

The junk drawer is the MVP of making your home seem meticulously tidy, and it’s also proof that “organized chaos” is a valid method of organization. But you should still be careful about what you toss in there; loose batteries, for example, are a fire hazard.

If metal comes into contact with both the positive and negative posts of a battery, it could cause a short circuit that generates enough heat to start a fire. And chances are pretty good that your junk drawer is currently housing a few metallic materials: paper clips, hardware, coins, keys, tacks, spare chargers, steel wool, pens, and aluminum foil can all pose a threat.

As Reader’s Digest explains, 9-volt batteries are especially unsafe because their positive and negative posts are right next to each other. But even if you’re only storing AA or AAA batteries—or any other batteries where the posts are on opposite ends—it’s probably not worth the risk.

The easiest way to prevent a fire is simply to keep your batteries out of your junk drawer and away from metal objects altogether. If you’re short on space, however, there are a couple other safety measures you can take. The National Fire Protection Association recommends storing batteries in their original packaging, or covering the posts with masking, duct, or electrical tape when you’re not using them [PDF]. You also shouldn’t throw 9-volt batteries in a container with other batteries, since those count as metal objects, too.

Once you’ve fire-proofed your junk drawer, find out how to avoid six other common household fire hazards here.

[h/t Reader’s Digest]

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