A Full Kindle Weighs More Than An Empty One

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A Full Kindle Weighs More Than An Empty One

In 2011, a few years into the brand-new e-reader craze, The New York Times weighed in on a common claim: unlike with a backpack, you can fill a digital device up with books and see no change in weight. To find out whether this was true, they turned to UC Berkeley computer science professor John D. Kubiatowicz. His answer? False.

04:11

from Vsauce

Key Facts to Know

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    One theory states that the weight of the entire Internet is about 50 grams. 0:02

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    It takes approximately 8 billion electrons to store just one 50-kilobyte email. 2:22

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    In 2005, Eric Schmidt estimated that the Internet holds about 5 million terabytes of information. 2:52

The Standard For The Kilogram May Be Losing Weight

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The Standard For The Kilogram May Be Losing Weight

The iridium alloy cylinder known as the International Prototype Kilogram, or Le Grand K, was forged in 1879 to set the standard for the weight of a kilogram. It sits beneath three vacuum-sealed bell jars in a vault outside Paris, coming out once every 40 years for a careful cleaning and a precise weigh-in to compare it with its 80 official replicas, which are used by countries throughout the world. These replicas are what scientists use to verify whether something is exactly one kilogram. But at its last weigh-in, something was off: its weight had drifted ever so slightly below that of its replicas by 50 micrograms, or roughly the weight of a grain of sand. Scientists don't know whether Le Grand K is losing weight, perhaps through cleaning or air gradually escaping the metal, or if it's the replicas that are gaining mass because of their less stringent handling requirements (even contamination from the open air might be enough to cause the difference). What we do know is that this difference means drastic consequences for the extreme precision of science. In truth, any tangible object is at risk of this kind of change, which explains why almost all of the seven standards of measurement established in 1791 -- all but Le Grand K -- have been abandoned, most in favor of universal constants. The meter, for instance, is now defined by how far light travels in a vacuum in a certain fraction of a second. In 2011, the General Conference on Weights and Measures decided to do the same with the kilogram. How they'll redefine it is anyone's guess, but the deadline for the decision is set for 2018. We've collected some awesome videos on this topic. Watch them now to learn more.

02:53

from SciShow

Key Facts to Know

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    In 1899, the International Bureau of Weights and Measures created an iridium cylinder as the worldwide standard for the kilogram. 0:32

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    30 years ago, scientists realized that the masses of the original kilogram and its copies are drifting apart. Nobody knows why. 1:03

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    The BIPM has already redefined other measures using universal constants. A meter, for example, is the distance light travels in 1/299,792,458 of a second. 1:39

Sit-Ups Are Risky. Try These Core Exercises Instead.

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Sit-Ups Are Risky. Try These Core Exercises Instead.

During the Army Physical Fitness Test (APFT), soldiers perform push-ups, sit-ups, and a two-mile run to demonstrate that they're physically qualified for duty. In a 2005 study, researchers found that although only 117 soldiers out of more than 1,500 sustained injuries during the test, a whopping 56% of those injuries were caused by sit-ups. This is no surprise to many: everyone from biomechanics experts to celebrity trainers have stopped recommending sit-ups because of their high potential for injury. According to Dr. Stuart McGill, professor of spine biomechanics at the University of Waterloo, sit-ups and crunches place up to 750 pounds (340 kilograms) of compressive force on the spine, which can lead the discs between the vertebrae to bulge and even herniate, pressing on nerves and causing serious back pain. What's more, they're not even that useful: the core muscles are primarily there to stabilize the torso, not flex the spine, so the strength gained from a flexing exercise like the sit-up has very few uses in the real world. That's why trainers and physicians are recommending the plank and other stabilizing exercises to help people build stronger cores.

02:55

Key Facts to Know

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    Sit-ups can lead to herniated discs in the spine and cause back pain. 0:13

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    Here are several alternate core-strengthening exercises. 0:42

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    If you did hundreds of sit-ups, your discs would break before your spine had a chance to catch up. 2:38

What Matters More For Weight Loss: Diet Or Exercise?

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What Matters More For Weight Loss: Diet Or Exercise?

If you're hoping to lose weight, focusing on your diet could prove way more helpful than hitting the gym. Exercise burns comparatively few calories when you take food into consideration. A 30-minute workout might burn somewhere between 300 and 400 calories, but you could cut the same amount from your diet by giving up a bag of chips and a soda. Multiple studies confirm that physical activity doesn't seem to be the deciding factor in whether people gain or lose weight, and that adjusting what you eat has a larger impact. This isn't to say that exercise isn't good for you -- it absolutely is and has significant effects on your overall health and fitness. Combining exercise with a healthy diet can indeed help with achieving sustainable weight loss.

05:51

Key Facts to Know

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    Exercise burns far fewer calories than many people think. 0:47

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    When you lose weight, your resting metabolic rate typically slows, which is why losing weight becomes harder over time. 2:56

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    Studies have shown that combining a healthy change in diet with exercise leads to sustainable weight loss, but that the inclusion of exercise makes a small or negligible difference after a certain period of time. 3:34

Walrus Skin Weighs A Lot

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Walrus Skin Weighs A Lot

As babies, walruses can gain about 1 kilogram (2 lbs) every day. Males grow to be larger than the females, and their tusks-which are their canine teeth-can reach lengths of 1 meter (3 ft 3 in). Males wield these tusks in fights for dominance, but females have them too, and both sexes use them to hoist themselves out of the water.

04:29

from Animalist

Key Facts to Know

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    When there isn't enough ice in the Arctic Circle, thousands of walruses swim to Alaska instead. 0:24

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    Walruses use their tusks to haul themselves out of the water and make breathing holes in ice. 1:41

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    Walrus mustaches aren't made of hair—they consist of specialized organs called mustacial vibrissae. 3:08