Was Christiaan Huygens nearsighted?
In 1655, using a telescope he designed, Christiaan Huygens became the first person to identify Saturn’s rings and one of its moons. In that era, the still-nascent understanding of optics was driven by trial and error: Researchers would find and optimize the focal lengths and other properties by eye and create tables of those values. The relationship between, say, the lens diameter and focal length could then be approximated from the tables. That process is what Huygens followed when he constructed his telescopes.
In some cases, Huygens managed to derive accurate relationships—for example, he correctly identified the magnification as the ratio of the focal lengths of the objective lens and the eyepiece, fo/fe. But many of the equations and tables are notably off from what one would expect on the basis of modern geometric and diffractive optics. In a recent study, Alexander Pietrow of Stockholm University in Sweden proposed that the discrepancy may have arisen not from limitations in Huygens’s skill or understanding but rather from his poor eyesight.
Pietrow found that Huygens’s combination of objective and eyepiece lenses overmagnifies by a factor of 3.5. On the basis of modern optics and typical human eyesight, the magnification from a telescope is related to the diameter of the objective lens by the equation M = 4.33Do. Although Huygens correctly identified a linear relationship, he empirically derived the equations M = 13.89Do and M = 15.29Do in two of his works.
Huygens’s equations could be reconciled with modern optics if his visual acuity had been 20/70. That level of nearsightedness wouldn’t require glasses, and Huygens’s father was known to have severe myopia, which has genetic risk factors. Pietrow suggests that Huygens may have unknowingly corrected for his eyesight in the design of his telescopes.
There are other potential explanations for the suboptimal design of Huygens’s telescopes. For example, if the lens surfaces are too rough or misshapen, then the limits on the performance aren’t based on the diffraction limit. The lenses had a reputation for high quality at the time, but future work could test whether they do indeed produce a diffraction-limited spot, as was shown for those made by the 17th-century optician Giuseppe Campani. (A. G. M. Pietrow, Notes Rec., 2023, doi:10.1098/rsnr.2022.0054.)
Boeing's first-ever crewed mission in Starliner ISS spacecraft delayed to late July – The Register
Boeing’s debut Starliner spacecraft launch carrying its first-ever crew of astronauts to the International Space Station is being postponed again, and is not expected to fly until 21 July at the earliest.
A Boeing Starliner landing system is tested for reliability in White Sands Space Harbor in New Mexico. Photo credit: NASA/Boeing
Steve Stich, manager of Commercial Crew Program at NASA, confirmed the delay in a media teleconference on Wednesday. Officials from the space agency and Boeing need more time to assess the capsule, and to avoid conflicts with upcoming flights scheduled to the ISS.
Boeing’s Crew Flight Test (CFT) mission has suffered repeated setbacks, and was originally slated to fly in April. “We’ve deliberated and decided that the best launch attempt is no earlier than July 21st,” Stitch said.
“Where we’re at right now is really getting through the certification work… it is a large amount of work which has been going on for well over a year. There’s 600 components that have to be qualified on the Starliner for NASA and Boeing to review jointly [and] over 70 hazard reports. And then a total of what we call 370 verifications,” he added.
They are both paying close attention to the parachute system on the Starliner deployed to land the spacecraft safely back on Earth. Ground tests will examine the parachute’s ability to launch properly and slow the Starliner to splash down safely for the return of astronauts Butch Wilmore and Suni Williams, who will fly and spend eight days docked to the ISS in the CFT.
Joel Montalbano, manager of NASA’s International Space Station Program, said that activities onboard the ISS are jam packed over the next few months. The Soyuz MS-23 currently docked to the space station will be relocated to another module. Russian cosmonauts and American astronauts will also be performing separate spacewalks to adjust for incoming solar arrays and retrieve hardware.
There are also upcoming cargo deliveries as well as the Axiom-2 mission, the second private crewed mission to the ISS, which will send the first Saudi Arabian woman, Rayyanah Barnawi, to space. Barnawi’s crewmates include Ali Alqarni, a second Saudi representative, Peggy Whitson, a NASA veteran, and John Shoffner, an investor and pilot.
All that means is Boeing will have to find a flight slot after these events.
“We’re very close,” said Mark Nappi, vice president and program manager of the CST Starliner at Boeing. He said the company was working hard to inspect the spacecraft’s hardware, build the service module, refurbish the crew module, and verify its flight software.
“Most of the areas that needed to be completed are going to be completed by the end of April. In the one area that Steve talked about, which is the parachute, the verification closure notice and the hazard report will poke out into May,” he said.
The next major milestone will be loading the propellant into the spacecraft about 40 days prior to its launch. ®
When is the next planetary alignment in Vancouver in 2023?
An uncommon celestial cluster dotted the sky over Vancouver last night.
A planetary alignment including Jupiter, Mercury, Venus, Uranus, and Mars, was seen over the city Tuesday (March 28) night.
Though planetary alignments aren’t rare, alignments involving so many planets aren’t common either.
Vancouver locals snapped photos of the astronomical spectacle.
When is the next planetary alignment visible in Vancouver?
According to the educational astronomy app Star Walk, Earth-dwellers will have plenty more opportunities to see clusters of planets in the sky this year. The next chance to spot Mercury, Uranus, Venus, and Mars lined up will be on April 11.
However, the next most noteworthy planetary alignment won’t take place until Sept. 8, 2040. On this night, stargazers will be able to see five planets– Venus, Mercury, Mars, Jupiter, and Saturn– with the naked eye, along with the crescent Moon between Venus and Saturn.
The next major alignment will occur 40 years later on March 15, 2080, with six planets– Venus, Mercury, Jupiter, Saturn, Mars, and Uranus– all visible in the morning sky. It will also feature the “great conjunction” of Saturn and Jupiter.
There is one exciting celestial event that will take place over a century later. On May 19, 2161, all the planets in the solar system, including Earth, will end up on one side of the Sun which means earthlings can observe every planet in the sky.
As for 2023, here is when you can spot the next planetary alignment in Vancouver:
- April 11 – Mercury, Uranus, Venus, Mars; small evening alignment with 35-degree sky sector
- April 24 – Mercury, Uranus, Venus, Mars; small evening alignment with 40-degree sky sector
- May 29 – Mercury, Uranus, Jupiter, Saturn; small morning alignment with 70-degree sky sector
- June 17 – Mercury, Uranus, Jupiter, Neptune; large morning alignment with 95-degree sky sector
- July 26 – Mercury, Venus, Mars; mini evening alignment with 15-degree sky sector
- August 24
- at sunset: setting Mercury and Mars, rising Saturn; mini alignment with 175-degree sky sector
- at night: Uranus, Jupiter, Neptune, Saturn; small alignment with 80-degree sky sector
Don’t Read Too Much into River Otters’ Return
Standing at the foot of a rocky sandstone cliff, biologist Michelle Wainstein inspected her essentials: latex gloves, two long cotton swabs, glass vials, and tubes filled with buffer solution. She placed them in a blue dry bag, rolled it up, and clipped it to a rope wrapped around her waist. It was late afternoon, and she was slick with dirt and sweat from navigating the dense terrain. Her destination lay across the frigid river: two small logs of otter fecal matter resting on a mossy boulder. In she plunged.
The river, the Green-Duwamish in Washington State, trickles out of the Cascade Range and empties 150 kilometers downstream into Puget Sound. The last eight kilometers of the run—known as the lower Duwamish—is so polluted the US Environmental Protection Agency designated it a Superfund site in 2001. For a century, Seattle’s aviation and manufacturing industries routinely dumped waste chemicals like polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) into the water.
“A lot of the river is still really polluted,” says Jamie Hearn, the Superfund program manager at Duwamish River Community Coalition. “The mud is thick and black, and you can smell it.”
Despite the pollution, river otters are everywhere along the waterway, even in the most contaminated areas near the river’s mouth. “I would be walking the docks looking for scat,” remembers Wainstein, “and a couple of times we were lucky enough to see moms with their pups.”
For several weeks in the summer of 2016 and 2017, Wainstein surveyed otter poop she collected from a dozen sites along the river. Comparing contaminant concentrations in the otters’ poop between the river’s industrial and rural zones, Wainstein uncovered the lingering legacy of the region’s toxic past. The poop from otters in the lower Duwamish contained nearly 26 times more PCBs and 10 times more PAHs than poop from their cousins in cleaner water upstream. PCBs disrupt hormonal and neurological processes and affect reproduction in mammals. Both PCBs and PAHs are human carcinogens.
The discovery that otters along the lower Duwamish are living with such high levels of contamination upends a common narrative: that river otters’ return to a once-degraded landscape is a sign that nature is healing.
In Singapore, where smooth-coated otters have reappeared in canals and reservoirs, they have been embraced as new national mascots. “It plays into that rhetoric that government agencies want to project,” says environmental historian Ruizhi Choo, “that we’ve done such a good job that nature is coming back. That image of a city in nature is the new marketing branding.”
In Europe, the once-common Eurasian otter similarly began reappearing in the late 20th century following successful river cleanup campaigns. Conservationist Joe Gaydos at the SeaDoc Society thinks that this phenomenon has helped form the mental link between otters and ecosystem health.
“The number of animals is our first indicator,” Gaydos says. But few seem to ask the next question: are those animals healthy?
As Wainstein’s study suggests, perhaps not. The otters she analyzed in the lower Duwamish have some of the highest concentrations of PCBs and PAHs ever recorded in wild river otters. Previous research has found a correlation between PCB exposure and health risks in wild river otters, including increased bone pathologies, reproductive and immunological disorders, organ abnormalities, and hormonal changes.
Even so, the contamination is not manifesting in physically obvious ways. “They’re not washing up on shore with tumors all over their bodies,” Wainstein says, and neither is their population dwindling. “They’re not setting off this direct alarm with a big change in their ability to survive.”
The otters’ ability to bear such a heavy contaminant burden suggests that a population resurgence alone may not reflect the quality of an environment. They just become as toxic as the environments they inhabit.
However, their localized bathroom habits, mixed diet of fish, crustaceans, and mammals, and persistence in the face of pollution make them useful indicators of environmental contamination.
River otters have played this role before. Following the 1989 Exxon Valdez oil spill, river otters lingered in oil-drenched waterways, allowing scientists like Larry Duffy at the University of Alaska Fairbanks to track the effectiveness of the oil cleanup. In 2014, scientists in Illinois discovered dieldrin in otter organ tissue even though the insecticide had already largely been banned for 30 years. In these cases, the collection of long-term pollution data was made possible by the creatures’ resilience in contaminated waterways. Wainstein wants to similarly use the Green-Duwamish River otters as biomonitors of the Superfund cleanup over the next decade.
Watching workers dismantle a portion of the river’s levied banks to make channels for salmon, Wainstein thinks about the seabirds, shorebirds, and small mammals, like beaver and mink, that were driven out by industrial contamination. She wonders if one day the rumbling machinery dredging up clawfuls of sediment from the riverbed will be taken over by the piercing cries of marbled murrelets, the croaks of tufted puffins, and the bubbling twittering of western snowy plovers.
“How long will it take? And will it actually work?” she says of the cleanup effort. The otters might hold the answer.
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