The theory of general relativity holds that a massive body like Earth curves space-time, causing time to slow as you approach the object — so a person on top of a mountain ages a tiny bit faster than someone at sea level.
US scientists have now confirmed the theory at the smallest scale ever, demonstrating that clocks tick at different rates when separated by fractions of a millimeter.
Jun Ye, of the National Institute of Standards and Technology (NIST) and the University of Colorado Boulder, said their new clock was “by far” the most precise ever built — and could pave the way for new discoveries in quantum mechanics, the rulebook for the subatomic world.
Photo: AFP
Ye and colleagues published their findings Wednesday in the prestigious journal Nature, describing the engineering advances that enabled them to build a device 50 times more precise than today’s best atomic clocks.
It wasn’t until the invention of atomic clocks — which keep time by detecting the transition between two energy states inside an atom exposed to a particular frequency — that scientists could prove Albert Einstein’s 1915 theory.
Early experiments included the Gravity Probe A of 1976, which involved a spacecraft 10,000 kilometers above Earth’s surface and showed that an onboard clock was faster than an equivalent on Earth by one second every 73 years.
Since then, clocks have become more and more precise, and thus better able to detect the effects of relativity.
In 2010, NIST scientists observed time moving at different rates when their clock was moved 33 centimeters higher.
THEORY OF EVERYTHING
Ye’s key breakthrough was working with webs of light, known as optical lattices, to trap atoms in orderly arrangements. This is to stop the atoms from falling due to gravity or otherwise moving, resulting in a loss of accuracy.
Inside Ye’s new clock are 100,000 strontium atoms, layered on top of each other like a stack of pancakes, in total about a millimeter high.
The clock is so precise that when the scientists divided the stack into two, they could detect differences in time in the top and bottom halves.
At this level of accuracy, clocks essentially act as sensors.
“Space and time are connected,” said Ye. “And with time measurement so precise, you can actually see how space is changing in real time — Earth is a lively, living body.”
Such clocks spread out over a volcanically-active region could tell geologists the difference between solid rock and lava, helping predict eruptions. Or, for example, study how global warming is causing glaciers to melt and oceans to rise.
What excites Ye most, however, is how future clocks could usher in a completely new realm of physics. The current clock can detect time differences across 200 microns — but if that was brought down to 20 microns, it could start to probe the quantum world, helping bridge disparities in theory.
While relativity beautifully explains how large objects like planets and galaxies behave, it is famously incompatible with quantum mechanics, which deals with the very small.
According to quantum theory, every particle is also a wave — and can occupy multiple places at the same time, something known as superposition. But it’s not clear how an object in two places at once would distort space-time, per Einstein’s theory.
The intersection of the two fields therefore would bring physics a step closer to a unifying “theory of everything” that explains all physical phenomena of the cosmos.
Taiwan’s overtaking of South Korea in GDP per capita is not a temporary anomaly, but the result of deeper structural problems in the South Korean economy says Chang Young-chul, the former CEO of Korea Asset Management Corp. Chang says that while it reflects Taiwan’s own gains, it also highlights weakening growth momentum in South Korea. As design and foundry capabilities become more important in the AI era, Seoul risks losing competitiveness if it relies too heavily on memory chips. IMF forecasts showing Taiwan widening its lead over South Korea have fueled debate in Seoul over memory chip dependence, industrial policy and
“China wants to unify with Taiwan at the lowest possible cost, and it currently believes that unification will become easier and less costly as time passes,” wrote Amanda Hsiao (蕭嫣然) and Bonnie Glaser in Foreign Affairs (“Why China Waits”) this month, describing how the People’s Republic of China (PRC) is playing the long game in its quest to seize Taiwan. This has been a favorite claim of many writers over the years, easy to argue because it is so trite. Very obviously, if the PRC isn’t attacking Taiwan, it is waiting. But for what? Hsiao and Glaser’s main point is trivial,
May 18 to May 24 Gathered on Yangtou Mountain (羊頭山) on Dec. 5, 1972, Taiwan’s hiking enthusiasts formally declared the formation of the “100 Peaks Club” (百岳俱樂部) and unveiled the final list of mountains. Famed mountaineer Lin Wen-an (林文安) led this effort for the Chinese Alpine Association (中華山岳協會). Working with other experienced climbers, he chose 100 peaks above 10,000 feet (3,048m) that featured triangulation points and varied in difficulty and character. The list sparked an alpine hiking craze, inspiring many to take up mountaineering and competing to “conquer” the summits. A common misconception is that the 100 Peaks represent Taiwan’s 100 tallest
The Chinese Nationalist Party (KMT), alongside their smaller allies the Taiwan People’s Party (TPP), are often accused of acting on behalf of the Chinese Communist Party (CCP). Some go so far as to call them “traitors.” It is not hard to see why. They regularly pass legislation to stymie the normal functioning of the ruling Democratic Progressive Party’s (DPP) administration, and they have yet to pass this year’s annual budget. They slashed key elements of the government’s proposed NT$1.25 trillion (US$40 billion) special military budget, and in the smaller NT$780 billion package they did pass, it is riddled with provisions that
RSS