Once a week.
Subscribe to our weekly newsletter.
The Most Accurate Clock Ever Made, and What It Can Do
It's more accurate than an atomic clock, and would take thousands of years to lose a second.
I once had a physics professor who commented on how much more precise timekeeping had become over his lifetime. He told us one day, out of the blue, “When I started this job you had to wind your watch, so you had to be at least five minutes early to the bus stop to be sure you were on time. Then they invented quartz watches and you could be a minute early. Now they have atomic clocks that are accurate to the fraction of a second when you wear them.”
It is curious to think about just how much a little extra precision in timekeeping can improve our everyday lives, and how we went, in a mere 50 years, from mechanical timekeeping to quantum timekeeping.
Well, now we have another improvement. A clock which is truly mind-boggling in its accuracy.
Modern atomic clocks typically measure time by observing the regular changing of energy levels in cesium atoms. This change is so well documented that the time this takes is literally the definition of a second. However, even clocks using this method have a flaw. The electron movement in a cesium atom has a speed limit that caps the maximum possible accuracy of the clocks.
This new and improved clock, built by the University of Colorado Boulder and JILA, uses strontium instead of cesium. This element changes energy levels faster than cesium can, meaning that measurements by a clock that uses it as a mechanism are more precise. To make it even more accurate the scientists placed the atoms in a 3D lattice, allowing more atoms to be packed together and for accuracy-destroying collisions between those atoms to be minimized. The whole structure is then frozen at -273 degrees Celsius, which further helps the atoms avoid one another. The clock is, therefore, a lattice of nearly frozen quantum gas, which is subtly changing with incredible speed.
The clock is so accurate that for every ten quintillion ticks only 3.5 would be inaccurate. For scale, the universe is not ten quintillion seconds old yet, making this clock reliable over more than the life of the entire cosmos.
However, despite the clock’s precision, Jun Ye, one of the researchers who built the machine, has stated that it hasn’t been running for long enough to determine if it will stay that precise. Others, such as physicist Christian Lisdat, have wondered aloud how the unique structure of the clock will affect its accuracy over the long run.
Some might ask, why would we build such a clock? At first glance, it can seem like a waste of money, but the applications include the ability to measure the effects of relativity to an even more precise scale, a favorite activity of physics departments everywhere. The clock can also be used to search for gravitational waves, as any fluctuation in its perfect timekeeping could be attributed to the waves' effects on the clock rather than its failures.
Scientists love to act on their curiosities. The curiosity of the day, in this case, was: how accurate can we make a clock? The answer is nearly perfectly so. The possible applications of this clock will be far-reaching in physics and engineering. While such a clock might never be made wearable, the benefits from more precise measurement will be numerous; even if it can’t help assure that you won’t miss the bus.
The idea of 'absolute time' is an illusion. Physics and subjective experience reveal why.
- Since Einstein posited his theory of general relativity, we've understood that gravity has the power to warp space and time.
- This "time dilation" effect occurs even at small levels.
- Outside of physics, we experience distortions in how we perceive time — sometimes to a startling extent.
Physics without time<p>In his book "The Order of Time," Italian theoretical physicist Carlo Rovelli suggests that our perception of time — our sense that time is forever flowing forward — could be a highly subjective projection. After all, when you look at reality on the smallest scale (using equations of quantum gravity, at least), time vanishes.</p><p style="margin-left: 20px;">"If I observe the microscopic state of things," writes Rovelli, "then the difference between past and future vanishes … in the elementary grammar of things, there is no distinction between 'cause' and 'effect.'"</p><p>So, why do we perceive time as flowing <em>forward</em>? Rovelli notes that, although time disappears on extremely small scales, we still obviously perceive events occur sequentially in reality. In other words, we observe entropy: Order changing into disorder; an egg cracking and getting scrambled.</p><p>Rovelli says key aspects of time are described by the second law of thermodynamics, which states that heat always passes from hot to cold. This is a one-way street. For example, an ice cube melts into a hot cup of tea, never the reverse. Rovelli suggests a similar phenomenon might explain why we're only able to perceive the past and not the future.</p><p style="margin-left: 20px;">"Any time the future is definitely distinguishable from the past, there is something like heat involved," Rovelli wrote for the <a href="https://www.ft.com/content/ce6ef7b8-429a-11e8-93cf-67ac3a6482fd" target="_blank"><em>Financial Times</em></a>. "Thermodynamics traces the direction of time to something called the 'low entropy of the past', a still mysterious phenomenon on which discussions rage."</p>
The strange subjectivity of time<p>Time moves differently atop a mountain than it does on a beach. But you don't need to travel any distance at all to experience strange distortions in your perception of time. In moments of life-or-death fear, for example, your brain would release large amounts of adrenaline, which would speed up your internal clock, causing you to perceive the outside world as moving slowly.<br></p><p>Another common distortion occurs when we focus our attention in particular ways.</p><p style="margin-left: 20px;">"If you're thinking about how time is <em>currently</em> passing by, the biggest factor influencing your time perception is attention," Aaron Sackett, associate professor of marketing at the University of St. Thomas, told <em><a href="https://gizmodo.com/why-does-time-slow-down-and-speed-up-1840133782" target="_blank">Gizmodo</a></em>.<em> "</em>The more attention you give to the passage of time, the slower it tends to go. As you become distracted from time's passing—perhaps by something interesting happening nearby, or a good daydreaming session—you're more likely to lose track of time, giving you the feeling that it's slipping by more quickly than before. "Time flies when you're having fun," they say, but really, it's more like "time flies when you're thinking about other things." That's why time will also often fly by when you're definitely <em>not</em> having fun—like when you're having a heated argument or are terrified about an upcoming presentation."</p><p>One of the most mysterious ways people experience time-perception distortions is through psychedelic drugs. In an interview with <a href="https://www.theguardian.com/books/2018/apr/14/carlo-rovelli-exploding-commonsense-notions-order-of-time-interview" target="_blank"><em>The Guardian</em></a>, Rovelli described a time he experimented with LSD.</p><p style="margin-left: 20px;">"It was an extraordinarily strong experience that touched me also intellectually," he said. "Among the strange phenomena was the sense of time stopping. Things were happening in my mind but the clock was not going ahead; the flow of time was not passing any more. It was a total subversion of the structure of reality."<br></p><p>It seems few scientists or philosophers believe time is completely an illusion.</p><p style="margin-left: 20px;">"What we call <em>time</em> is a rich, stratified concept; it has many layers," Rovelli told <em><a href="https://physicstoday.scitation.org/do/10.1063/PT.6.4.20190219a/full/" target="_blank">Physics Today</a>.</em> "Some of time's layers apply only at limited scales within limited domains. This does not make them illusions."</p>What <em>is</em> an illusion is the idea that time flows at an absolute rate. The river of time might be flowing forever forward, but it moves at different speeds, between people, and even within your own mind.
The world's 10 most affected countries are spending up to 59% of their GDP on the effects of violence.
- Conflict and violence cost the world more than $14 trillion a year.
- That's the equivalent of $5 a day for every person on the planet.
- Research shows that peace brings prosperity, lower inflation and more jobs.
- Just a 2% reduction in conflict would free up as much money as the global aid budget.
- Report urges governments to improve peacefulness, especially amid COVID-19.
The lush biodiversity of South America's rainforests is rooted in one of the most cataclysmic events that ever struck Earth.
- One especially mysterious thing about the asteroid impact, which killed the dinosaurs, is how it transformed Earth's tropical rainforests.
- A recent study analyzed ancient fossils collected in modern-day Colombia to determine how tropical rainforests changed after the bolide impact.
- The results highlight how nature is able to recover from cataclysmic events, though it may take millions of years.