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.

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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

Just One Parsec Is Equal To 19 Trillion Miles (31 Trillion Km)

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Just One Parsec Is Equal To 19 Trillion Miles (31 Trillion Km)

Now, hang on just one parsec... Though a parsec may sound like a derivative of "second," it's not. And that's why the famed line about the Millennium Falcon in Star Wars—"It's the ship that made the Kessel Run in less than 12 parsecs"—doesn't make sense. A parsec is a unit of measurement, not a unit of time. Sorry, Han. More specifically, one parsec is equivalent to 3.26 light years, or 19 trillion miles (or 31 trillion kilometers). If this seems excessively large, that's because it is. But when it comes to measuring astronomically large distances between objects beyond our Solar System, excessively large is just right. The word itself comes from two words: parallax and arcsecond. Parallax describes when something's location seems to have changed because your location changed, while arcsecond is the measurement of an angle. Putting it altogether, a parsec is the parallax of one arcsecond, a statement which requires some trigonometry to fully understand. To give an example of this huge distance, the betelgeuse star, the ninth-brightest star in the night sky, is only 196 parsecs away. Learn more about this huge measure of distance in the video below.

Planck Time Is How Long It Takes Light To Travel One Planck Length

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Planck Time Is How Long It Takes Light To Travel One Planck Length

What's the tiniest length of time you can think of? Maybe milliseconds come to mind. Try again, but this time think like a physicist. Physics uses units of Planck measurements, which are extremely tiny. The Planck time is the smallest conceivable length of time. Its definition might make your head spin: One unit of Planck time equals the time it takes light to travel a distance of one Planck length in a vacuum. Keep in mind the Planck length is the smallest conceivable length. German physicist Max Planck, the founder of quantum theory, proposed Planck units in 1899. They were invented, as reported by Universe Today, as a "means of simplifying the particular algebraic expressions appearing in theoretical physics, especially in quantum mechanics." Getting back to Planck time specifically, here's an easier way to imagine just how small it really is: There are more units of Planck time in one second than all the seconds since the Big Bang. Learn more about Planck time in the video below.

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Key Facts to Know

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    The Planck length is the smallest length (it measures 1.61619926 × 10^-35 meters). 0:01

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    The shortest possible time may be the Planck length divided by the speed of light. 0:28

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    The attosecond may be the shortest amount of time that has ever been identified. 1:00

Every Map Is Lying To You

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Every Map Is Lying To You

Picture a map in your mind. Chances are good that the map you've imagined is the Mercator projection, since it's the most popular. How big is the United States compared to Russia? Greenland to Africa? Antarctica to Europe? If you cross-check the sizes of those countries with those on a globe, you're likely to be surprised. Though the Mercator projection makes Africa and Greenland appear roughly the same size, they're nothing close: Africa is actually a whopping 14 times larger than Greenland. So why do they look so similar on a map? It's because a sphere is not what mathematicians call a developable surface, or one that can be flattened onto a plane without being distorted. For a cartographer to put the globe on a flat surface, sacrifices must be made. In the case of the Mercator projection, we sacrifice relative size for compass accuracy; that is, the map exaggerates the size of countries as they get closer to the poles, but maintains true north-south and east-west direction between any two points to make navigation easier. Other maps might show more realistic sizes but make trade-offs in continuity or distance. Even using a globe has its drawbacks: you can't see every country at once, and it forces you to measure distance in arcs instead of straight lines. In the end, the most "accurate" map depends on what you'll use it for. Explore the challenges of depicting the Earth in the videos below.

Atomic Clocks Tell Time Down to the Nanosecond

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Atomic Clocks Tell Time Down to the Nanosecond

How accurate does a clock need to be? That all depends on what you need it for. A glance at the sun in the sky is enough to tell you when to head home from a hike, whereas you might need a wristwatch to know whether you'll be late to a morning meeting. Likewise, certain applications in science and technology require much more precise timekeeping than that. In those cases, scientists use atomic clocks. Atomic clocks rely on the fact that you can blast an atom with a certain frequency of radiation, such as radio waves, that will cause its electrons to "jump" back and forth, or oscillate, between energy states. All atoms of a given element will reliably oscillate when exposed to a given frequency. For cesium, the most common element used in atomic clocks, that frequency is 9,192,631,770 cycles per second. That is, if a radio wave is making a cesium atom oscillate, we know that its frequency is exactly 9,192,631,770 cycles per second and then know exactly how long a second is based on those cycles. In fact, since 1967, the official definition of the second has been based on the oscillation of a cesium atom. The first atomic clocks were made in the 1950s and have only gotten more accurate. Today, the NIST-F1 cesium atomic clock is so precise that its time error is about 0.03 nanoseconds per day, or roughly one second every 100 million years. We've collected some awesome videos on this topic. Watch them now to learn more.

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from NOVA PBS

Key Facts to Know

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    Atomic clocks measure the oscillations of atoms. All atoms of a given element vibrate, or tick, the same number of times per second. 1:16

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    Today, the international standard for a second is based on 9,192,631,770 vibrations of a cesium atom. 1:50

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    Atomic clocks are accurate to one second in 3 million years. 2:18