Why Do We Tan?

iStock / bymuratdeniz
iStock / bymuratdeniz

Sit out in the sun too long and ultraviolet radiation from sunlight penetrates your skin and cells, damaging their RNA and DNA. This is bad news, as DNA provides our bodies with all the genetic instructions they need to develop, survive and go about their business, and this kind of DNA damage can lead to skin cancer. To protect you from this, your body helpfully tans, darkening the the skin with a pigment called melanin that reduces UV penetration into cells.

UV radiation stimulates the darkening of existing melanin and spurs increased melanogenesis, the production of new melanin. Cells called melanocytes generate the pigment and push it out of the cell, where it darkens the skin and absorbs and transforms absorbed UV energy into heat.

Melanogenesis results in a delayed tan that only becomes visible several hours after UV exposure and lasts longer than the tanning caused by darkening of existing melanin. Over time, a tan fades as darkened skin layers are pushed upward by new cells with less melanin, and are eventually scaled off.

Why do we get sunburn?

While we might say someone with sunburn was out “baking” too long or got “fried,” sunburns are different from the burn one might get from, say, touching a hot stove. That’s a thermal burn caused by the heat of the stove. While the sun does give off heat, a sunburn is caused by ultraviolet-B radiation.

When someone’s exposure to UV radiation exceeds their body’s ability to protect the skin with tanning, the radiation  causes damage to DNA, like we talked about above. This prompts the body to try and fix things. Bloodflow to the capillary bed of the dermis (the second outermost layer of skin) increases so cells can repair the damage, which results in warmth and redness of the skin. Inflammatory immune cells also flock to the damaged tissue, causing us to perceive pain and, hopefully, consider staying out of the sun for a while. Eventually, the damaged skin cells die, and the burned skin starts to peel.

Amazon's Under-the-Radar Coupon Page Features Deals on Home Goods, Electronics, and Groceries

Stock Catalog, Flickr // CC BY 2.0
Stock Catalog, Flickr // CC BY 2.0

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

Now that Prime Day is over, and with Black Friday and Cyber Monday still a few weeks away, online deals may seem harder to come by. And while it can be a hassle to scour the internet for promo codes, buy-one-get-one deals, and flash sales, Amazon actually has an extensive coupon page you might not know about that features deals to look through every day.

As pointed out by People, the coupon page breaks deals down by categories, like electronics, home & kitchen, and groceries (the coupons even work with SNAP benefits). Since most of the deals revolve around the essentials, it's easy to stock up on items like Cottonelle toilet paper, Tide Pods, Cascade dishwasher detergent, and a 50 pack of surgical masks whenever you're running low.

But the low prices don't just stop at necessities. If you’re looking for the best deal on headphones, all you have to do is go to the electronics coupon page and it will bring up a deal on these COWIN E7 PRO noise-canceling headphones, which are now $80, thanks to a $10 coupon you could have missed.

Alternatively, if you are looking for deals on specific brands, you can search for their coupons from the page. So if you've had your eye on the Homall S-Racer gaming chair, you’ll find there's currently a coupon that saves you 5 percent, thanks to a simple search.

To discover all the deals you have been missing out on, head over to the Amazon Coupons page.

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Why Do We Have Daylight Saving Time?

Patrick Daxenbichler/iStock via Getty Images
Patrick Daxenbichler/iStock via Getty Images

As you drag your time-confused body out of bed at what seems like a shockingly late hour next week, you might find yourself wondering why on Earth we even have Daylight Saving Time.

Though Benjamin Franklin was mostly joking when he suggested it as a money-saving tactic in a satirical essay from 1784, others who later proposed the idea were totally serious. In 1895, entomologist George Vernon Hudson pitched it to the Royal Society in New Zealand as a way to prolong daylight for bug-hunting purposes, and William Willett spent the early 1900s lobbying British Parliament to adopt an 80-minute time jump in April; neither man was successful.

During World War I, however, the need to conserve energy—which, at the time, chiefly came from coal—increased, and Germany was the first to give Daylight Saving Time the green light in 1916. Britain and other European countries quickly followed suit, and the U.S. entered the game in 1918. The practice was dropped almost everywhere after the war, but it was widely resurrected just a few decades later during World War II.

After that war ended, the U.S. abandoned DST yet again—sort of. Without any official legislation, the country devolved into a jumble of conflicting practices. According to History.com, Iowa had 23 different pairs of start and end dates for DST in 1965, while other areas of the country didn’t observe DST at all.

In 1966, Congress put an end to the chaos by passing the Uniform Time Act, which specified that DST would begin at 2:00 a.m. on the last Sunday in April, and end at the same time on the last Sunday in October. (The Energy Policy Act of 2005 extended DST by shifting these dates to the second Sunday in March and the first Sunday in November.) It didn’t require that all states and territories actually observe DST, and some of them didn’t—Arizona and Hawaii still don’t.

Throughout its long, lurching history, the supposed merits of Daylight Saving Time have always been about cutting down on electricity usage and conserving energy in general. But, as Live Science reports, experts disagree on whether this actually works. Some studies suggest that while the extra daylight hour might decrease lighting-related electricity use, it also means people could be keeping their air conditioners running for long enough that it increases the overall usage of electricity.

If your extended night’s sleep seems to have left you with a little extra time on your hands, see how DST affects your part of the country here.

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