Farmers Never Wanted Daylight Saving Time
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Why do we have daylight saving time? It's a popular theory that the concept was devised to give American farmers more daylight during harvest, but that's actually not the case. To save energy during wartime, President Woodrow Wilson proposed setting clocks back an hour in the fall, thereby giving people an extra hour of daylight when they wouldn't need to use electric lights. This was a boon for commercial interests, since office workers would have more daylight for shopping at the end of the day. But for farmers, this extra hour changed everything. It meant they couldn't work as quickly in the morning because the fields were covered in dew, and cows weren't ready to produce when the milk truck arrived. They disliked daylight saving time so much, in fact, that they pushed, successfully, for its repeal in 1919. That federal repeal turned daylight saving time from a broad national rule to a patchwork of state and local regulations, creating so many time differences that, according to History, "passengers on a 35-mile bus ride from Steubenville, Ohio, to Moundsville, West Virginia, passed through seven time changes." Finally, in 1966, the Uniform Time Act standardized daylight saving time for the United States yet again. Learn more about the origins of daylight saving time in the videos below.
Time Crystals Break The Continuity Of Time
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In September 2016, a team of researchers from the University of Maryland announced that they had experimentally confirmed the existence of time crystals. That is, crystals that break the continuity of time. Confused? Let's break this down.
Planck Time Is How Long It Takes Light To Travel One Planck Length
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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.
from Sixty Symbols
Key Facts to Know
The Planck length is the smallest length (it measures 1.61619926 × 10^-35 meters). 0:01
The shortest possible time may be the Planck length divided by the speed of light. 0:28
The attosecond may be the shortest amount of time that has ever been identified. 1:00
Theoretically Passing Through Space And Time In A Wormhole
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Wormholes have nothing to do with earthworms, but are more like space tubes. A wormhole is a theoretical passage through space-time that could help people and things travel huge distances through space in short amounts of time. Albert Einstein and Nathan Rosen proposed this theory in 1935; wormholes are also known as Einstein-Rosen bridges. According to Einstein's theory of general relativity, they mathematically should exist. But we have never actually observed one.A wormhole, theoretically speaking, has two mouths connected by a throat that connects two different points in space-time. They may not only connect two points, but some theories about wormholes suggest they may also be able to connect two universes. So could we time travel in a wormhole like plenty of science-fiction movies suggest? Perhaps not, according to Einstein and Rosen's theory, which states that a wormhole collapses quickly. New theories have emerged that suggest wormholes may stay open longer, but we're far from having the technology required to find and use them. Learn more about wormholes in the videos below.
Atomic Clocks Tell Time Down to the Nanosecond
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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.
from NOVA PBS
Key Facts to Know
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
Today, the international standard for a second is based on 9,192,631,770 vibrations of a cesium atom. 1:50
Atomic clocks are accurate to one second in 3 million years. 2:18