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16 Apr 2025 - 09:11 am

Space, time: The continual question
If time moves differently on the peaks of mountains than the shores of the ocean, you can imagine that things get even more bizarre the farther away from Earth you travel.
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To add more complication: Time also passes slower the faster a person or spacecraft is moving, according to Einstein’s theory of special relativity.

Astronauts on the International Space Station, for example, are lucky, said Dr. Bijunath Patla, a theoretical physicist with the US National Institute of Standards and Technology, in a phone interview. Though the space station orbits about 200 miles (322 kilometers) above Earth’s surface, it also travels at high speeds — looping the planet 16 times per day — so the effects of relativity somewhat cancel each other out, Patla said. For that reason, astronauts on the orbiting laboratory can easily use Earth time to stay on schedule.
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For other missions — it’s not so simple.

Fortunately, scientists already have decades of experience contending with the complexities.

Spacecraft, for example, are equipped with their own clocks called oscillators, Gramling said.

“They maintain their own time,” Gramling said. “And most of our operations for spacecraft — even spacecraft that are all the way out at Pluto, or the Kuiper Belt, like New Horizons — (rely on) ground stations that are back on Earth. So everything they’re doing has to correlate with UTC.”
But those spacecraft also rely on their own kept time, Gramling said. Vehicles exploring deep into the solar system, for example, have to know — based on their own time scale — when they are approaching a planet in case the spacecraft needs to use that planetary body for navigational purposes, she added.

For 50 years, scientists have also been able to observe atomic clocks that are tucked aboard GPS satellites, which orbit Earth about 12,550 miles (20,200 kilometers) away — or about one-nineteenth the distance between our planet and the moon.

Studying those clocks has given scientists a great starting point to begin extrapolating further as they set out to establish a new time scale for the moon, Patla said.

“We can easily compare (GPS) clocks to clocks on the ground,” Patla said, adding that scientists have found a way to gently slow GPS clocks down, making them tick more in-line with Earth-bound clocks. “Obviously, it’s not as easy as it sounds, but it’s easier than making a mess.”

Jeffreyhom

16 Apr 2025 - 09:11 am

Lunar clockwork
What scientists know for certain is that they need to get precision timekeeping instruments to the moon.
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Exactly who pays for lunar clocks, which type of clocks will go, and where they’ll be positioned are all questions that remain up in the air, Gramling said.

“We have to work all of this out,” she said. “I don’t think we know yet. I think it will be an amalgamation of several different things.”
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Atomic clocks, Gramling noted, are great for long-term stability, and crystal oscillators have an advantage for short-term stability.
“You never trust one clock,” Gramling added. “And you never trust two clocks.”

Clocks of various types could be placed inside satellites that orbit the moon or perhaps at the precise locations on the lunar surface that astronauts will one day visit.

As for price, an atomic clock worthy of space travel could cost around a few million dollars, according Gramling, with crystal oscillators coming in substantially cheaper.

But, Patla said, you get what you pay for.

“The very cheap oscillators may be off by milliseconds or even 10s of milliseconds,” he added. “And that is important because for navigation purposes — we need to have the clocks synchronized to 10s of nanoseconds.”

A network of clocks on the moon could work in concert to inform the new lunar time scale, just as atomic clocks do for UTC on Earth.

(There will not, Gramling added, be different time zones on the moon. “There have been conversations about creating different zones, with the answer: ‘No,’” she said. “But that could change in the future.”)

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The world’s largest architectural model captures New York City in the ’90s
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The Empire State building stands approximately 15 inches tall, whereas the Statue of Liberty measures at just under two inches without its base. At this scale, even ants would be too big to represent people in the streets below.

These lifelike miniatures of iconic landmarks can be found on the Panorama — which, at 9,335 square feet, is the largest model of New York City, meticulously hand-built at a scale of 1:1,200. The sprawling model sits in its own room at the Queens Museum, where it was first installed in the 1960s, softly rotating between day and night lighting as visitors on glass walkways are given a bird’s eye view of all five boroughs of the city.

To mark the model’s 60th anniversary, which was celebrated last year, the museum has published a new book offering a behind-the-scenes look at how the Panorama was made. Original footage of the last major update to the model, completed in 1992, has also gone on show at the museum as part of a 12-minute video that features interviews with some of the renovators.

The Queens Museum’s assistant director of archives and collections, Lynn Maliszewski, who took CNN on a visit of the Panorama in early March, said she hopes the book and video will help to draw more visitors and attention to the copious amount of labor — over 100 full-time workers, from July 1961 to April 1964 — that went into building the model.

“Sometimes when I walk in here, I get goosebumps, because this is so representative of dreams and hopes and family and struggle and despair and excitement… every piece of the spectrum of human emotion is here (in New York) happening at the same time,” said Maliszewski. “It shows us things that you can’t get when you’re on the ground.”
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The Panorama was originally built for the 1964 New York World’s Fair, then the largest international exhibition in the US, aimed at spotlighting the city’s innovation. The fair was overseen by Robert Moses, the influential and notorious urban planner whose highway projects displaced hundreds of thousands New Yorkers. When Moses commissioned the Panorama, which had parts that could be removed and redesigned to determine new traffic patterns and neighborhood designs, he saw an opportunity to use it as a city planning tool.

Originally built and revised with a margin of error under 1%, the model was updated multiple times before the 1990s, though it is now frozen in time. According to Maliszewski, it cost over $672,000 to make in 1964 ($6.8 million in today’s money) and nearly $2 million (about $4.5 million today) was spent when it was last revised in 1992.

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The fish collectors hoping to save rare species from extinction
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In the rural town of Petersham, Massachusetts, 78-year-old Peter George keeps 1,000 fish in his basement.

“Baseball, sex, fish,” he says, listing his life’s great loves. “My single greatest attribute is that I am passionate about things. That sort of defines me.”

All of George’s fish are endangered Rift Lake cichlids: colorful, freshwater fish native to the Great Lakes of East Africa. Inside his 42 tanks, expertly squeezed into a single subterranean room, the fish shimmer under artificial lights, knowing nothing of the expansive waters in which their ancestors once swam, thousands of miles away.

Due to pollution, climate change and overfishing, freshwater fish are thought to be the second most endangered vertebrates in the world. In Lake Victoria, a giant lake shared between Kenya, Uganda and Tanzania, over a quarter of endemic species, including countless cichlids, are either critically endangered or extinct.

But for some species, there is still hope. A community of rare fish enthusiasts collect endangered species of freshwater fish from the lakes and springs of East Africa, Mexico and elsewhere, and preserve them in their personal fish tanks in the hope that they might one day be reintroduced in the wild.

“I’m a hard ass,” George says. “There is hope.”
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George has been collecting fish since 1948 when, as a four-year-old in the Bronx, he would look after his grandmother’s rainbow fish. He soon developed “multiple tank syndrome” – a colloquial term used by fish collectors to denote the spiral commonly experienced after acquiring one’s first tank, which involves the sufferer buying many more tanks within a short space of time. He has not stopped collecting since.

Now, George sees himself as a conservationist; his tanks contain what is known as “insurance populations” – populations of endangered fish that are likely to go extinct in their natural habitats. He believes that when the time is right, they can be taken from his collection and returned to their homes. “I would never accept the fact that they couldn’t be reintroduced,” he says.

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