Posts Tagged ‘telescope’
“Oh dark, dark, dark, amid the blaze of noon, irrevocably dark, total eclipse without all hope of day”*…
Today is the occasion of an annular eclipse, which will pass through eight U.S. states before crossing the Gulf of Mexico and to transit Mexico, Guatemala, Belize, Honduras, Nicaragua, Costa Rica, Panama, Colombia, and Brazil. While some people in the Western Hemisphere will witness a “ring of fire” during the eclipse, many more will experience the phenomenon of crescent sunlight. Rebecca Boyle has advice on how we might approach it…
… This Saturday, for some people in the Western Hemisphere, the Sun will disappear for a few minutes and appear to leave a flaming hole in the sky. Instead of a ball of fire, the Sun will transform into a ring of fire, a strange and wondrous sight. This is an annular solar eclipse, and it happens because the Moon is right smack in front of the Sun.
A solar eclipse only happens during new Moon phases, when we otherwise wouldn’t be able to see our nearest celestial companion. Though we get a new Moon every month, we do not get solar eclipses as often because of our satellite’s oddball path around the planet. Sometimes the Moon casts a shadow just above Earth, and sometimes just below. This weekend, the Moon’s shadow will fall onto Earth, just right for people in parts of the Western Hemisphere to see it.
The annular eclipse is a preview of a more incredible, rarer event next April, when a total solar eclipse will cross the continental United States. There is no experience on Earth like a total eclipse; make plans to see it, if you can. But this weekend’s “ring of fire” eclipse is an event you should try to see first (safely, with eclipse glasses), if you can get yourself into the western U.S. or parts of Central and South America. Here’s a map showing the eclipse path; if you can’t travel to see it in person, you can watch the eclipse online.
Eclipses happen because the Sun and Moon appear to be roughly the same diameter. The Sun is actually about 400 times larger than the Moon, but it is also about 400 times more distant, so they seem like the same size in our sky.
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The Moon’s shadow forms two concentric cones, composed of an inner shadow called the umbra, where the sun is completely obscured, and an outer, broader cone called a penumbra, where sunlight still shines but it is partially blocked. The umbra can be seen in a narrow geographic ribbon across the Americas, and it’s where you will see a full eclipse; under the penumbra, which covers much of the western U.S., Central and South America, you will see a partial eclipse.
Like the gears of a clock, a combination of precise positions and movements initiate an eclipse of the Sun. As Earth spins, day breaks. The Sun and Moon appear to trace a path across the sky. The Sun is not moving (at least not perceptibly); Earth’s rotation makes the star’s position change. The Moon is moving around us while the Earth rotates, so it seems to move too, but it appears to go slower than our star. The partial solar eclipse begins as the Sun catches up to the Moon’s position in our sky. On Saturday morning around 8:06 a.m. Pacific time, people in Eugene, Oregon, will be the first to see the Moon appear to take a bite out of the Sun. The bite will get progressively bigger until the full annular eclipse begins at 9:16 a.m. Pacific time.
The annular eclipse only lasts about four minutes (depending on your precise location under the Moon’s shadow) but the partial eclipse, which will be visible over a much wider geographic area, lasts about an hour and 15 minutes before and afterward. During this phase, shadows cast by objects on Earth will change in unusual ways. One lovely place to be during a partial solar eclipse is underneath a tree, if you can find an evergreen or a deciduous tree that has not dropped its leaves yet. Look at the ground. In the dappled light, you will see crescents everywhere: the crescent Sun.
Sunlight is the heavens reaching down to touch us right where we stand; I think about this when I step into the light. But crescent sunlight is the Moon joining this experience. Its darkness, rather than its light, reaches out to touch us, too…
An informative and lyrical guide to today’s eclipse: “During an Annular Eclipse, Look to the Shadows,” from @rboyle31 in @atlasobscura.
* John Milton, Samson Agonistes
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As we don’t look directly, we might recall that on this date in 1609, Galileo (who has claim to the titles Father of observational astronomy, modern-era classical physics, the scientific method, and modern science) put the telescope to use in his astronomical work. Upon hearing (at age 40) that a Dutch optician had invented a glass that made distant objects appear larger, Galileo crafted his telescope. He continued to improve his device, ultimately achieving 30X magnification, and recorded his observations of the Moon, the moons of Jupiter, the Phases of Venus, Sunspots, The Milky Way, and more. He published his initial telescopic astronomical observations in March 1610 in a brief treatise entitled Sidereus Nuncius (Starry Messenger).
Telescopes were also a profitable sideline for Galileo, who sold them to merchants who found them useful both at sea and as items of trade.
“Time and tide wait for no man”*…
The week both arranges and imposes on our time…
Among many collective discoveries during the pandemic confinement of 2020, Americans learned just how attached we are to our seven weekdays. As complaints about temporal disorientation mounted that April, we focused not on the clock – the classic metonym for the power and experience of time – but rather on the calendar, and specifically the weekly one. A Cleveland news station affiliated with the Fox Media network entertained viewers with a daily feature, much circulated on the internet, entitled ‘What Day Is It? With Todd Meany’ – the answer to which was always a weekday, not a Gregorian calendar date…
Weeks serve as powerful mnemonic anchors because they are fundamentally artificial. Unlike days, months and years, all of which track, approximate, mimic or at least allude to some natural process (with hours, minutes and seconds representing neat fractions of those larger units), the week finds its foundation entirely in history. To say ‘today is Tuesday’ is to make a claim about the past rather than about the stars or the tides or the weather. We are asserting that a certain number of days, reckoned by uninterrupted counts of seven, separate today from some earlier moment. And because those counts have no prospect of astronomical confirmation or alignment, weeks depend in some sense on meticulous historical recordkeeping. But practically speaking, weekly counts are reinforced by the habits and rituals of other people. When those habits and rituals were radically obscured or altered in 2020, the week itself seemed to unravel…
The history of weekly timekeeping, which is only about 2,000 years old. Although taboos and cosmologies in several different cultures attached significance to seven-day cycles much earlier, there is no clear evidence of any society using such cycles to track time in the form of a common calendar before the end of the 1st century CE. As the scholars Ilaria Bultrighini and Sacha Stern have recently documented, it was in the context of the Roman Empire that a standardised weekly calendar emerged out of a combination and conflation of Jewish Sabbath counts and Roman planetary cycles. The weekly calendar, from the moment of its effective invention, reflected a union of very different ways of counting days…
The crucial formation of our modern experience of weekly time took place around the first half of the 1800s, with the rising prominence of… the differentiated weekly schedule…
The week is the most artificial and most recent of the ways we account for time, but it’s effectively impossible to imagine our shared lives without it: “How we became weekly,” by David Henkin in @aeonmag.
See also Jill Lepore‘s characteristically informative review of Henkin’s book on the week: “How the Week Organizes and Tyrannizes Our Lives” (source of the image above)
* Geoffrey Chaucer
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As we mark time, we might recall that it was on this date in 1839 that John William Draper took a daguerreotype of the moon (the “governor” of months, while the sun determines days, seasons, and years); it was the first celestial photograph (or astrophotograph) made in the U.S. (He exposed the plate for 20 minutes using a 5-inch telescope and produced an image one inch in diameter.) Draper’s picture of his sister, taken the following year, is the oldest surviving photographic portrait.
“The history of astronomy is a history of receding horizons”*…
The closest astronomers have come to directly “seeing” a black hole happened last year, when the LIGO observatory detected the spacetime-warping gravitational waves radiating from a pair of black holes that collided some 1.3 billion years ago.
That’s cool. But for astronomers, it’s not enough. What’s eluded them is a view of the event horizon, the boundary of the black hole from which, when crossed, there is no return. After the event horizon, gravity is so intense that not even light can escape.
We’ve never seen a direct image of a black hole. But if an audacious experiment called the Event Horizon Telescope is successful, we’ll see one for the first time…
Find out how at “Astronomers just turned on a planet-size telescope to take a picture of a black hole.”
* Edwin Hubble
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As we look into it, we might recall that it was on this date in 1006 CE that observers across China, Japan, Iraq, Egypt, and Europe recorded their observation of a supernova (now known as SN 1006). Likely the brightest observed stellar event in recorded history, it reached an estimated −7.5 visual magnitude (more than sixteen times the brightness of Venus). Many experts believe that it was also recorded in the Native American petroglyphs in White Tank Mountain Regional Park, Arizona, making them the first North American record of a supernova sighting.
SN 1006 supernova remnant
“If I have seen further than others, it is by standing upon the shoulders of giants”*…
Newton’s reflecting telescope of 1671
On 11 January 1672, the Fellows of the British Royal Society were treated to a demonstration of Isaac Newton’s reflecting telescope, which formed images with mirrors rather than with the lenses that had been used since the time of Galileo. Afterward, the fellows hailed Newton as the inventor of this marvellous new instrument, an attribution that sticks to the present. However, this linear historical account obscures a far more interesting, convoluted story. Newton’s claim was immediately challenged on behalf of two other contenders, James Gregory and Laurent Cassegrain. More confounding, the earliest known concept of using a curved mirror to focus light predated Newton by more than 1,500 years; the final realisation of a practical reflecting telescope post-dated him by more than a half century…
For almost any device, claiming one individual as the inventor is problematic to say the least. Conception, demonstration and implementation can be very different things, and the path connecting them is typically not a line but a long, challenging and tortuous route…
A cautionary tale illustrating the danger of crediting technologies to single inventors: “How many great minds does it take to invent a telescope?”
Pair with this explanation of why men so often get credit for women’s inventions– a phenomenon so common that it has a name, “the Matilda effect.”
* Issac Newton
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As we share the credit, we might send scientific birthday greetings to Vincenzo Viviani; he was born on this date in 1622. A mathematician and engineer, Viviani is probably best remembered as a discipline of Galileo: he served as the (then-blind) scientist’s secretary until Galileo’s death; he edited the first edition of Galileo’s collected works; and he worked tirelessly to have his master’s memory rehabilitated. But Viviani was an accomplished scientist in his own right: he published a number of books on mathematical and scientific subjects, and was a founding member of the Accademia del Cimento, one of the first important scientific societies, predating England’s Royal Society.
It’s always Chile in Norway?…
When it comes to a country’s prospects, is morphology destiny? Or is it simply the phrenology of geography? Strange Maps explores…
Do Norwegians feel curiously at home in Chile, and vice versa? Do South Africans have a strange affinity with Italians? And Filipinos with Maldivians? They should, at least if they’re map nerds: each lives in a country with a territorial morphology that closely resembles the other’s.
Although they’re on opposite sides of the globe, Chile and Norway are each other’s type, morphologically speaking: elongated to the extreme…
The Five Types of Territorial Morphology [c.f., here] sounds like a fun parlour game, at least in cartophile circles (is Portugal compact or elongated? Is or isn’t Somalia prorupt? Does New Zealand qualify as fragmented?) But there is a serious, geopolitical concern behind this attempt at classification. For a country’s shape has a profound impact on its economic success, and even its political viability.
Case in point: Lesotho. Being completely surrounded by another country does your economy no good. Four out of 10 Lesothans live on less than $1 a day, and the country ranks 160th (out of 187) on the UNDP’s Human Development Index. Even compared with the wildly unequal society that is South Africa, Lesotho stands out as a pocket of deprivation…
Another morphology, another set of problems. Fragmented states often experience great centrifugal pressures, with separatism affecting their outlying fragments. This is true of the Philippines, the central government of which only last October concluded a peace deal with the Moro Islamic Liberation Front, which had waged a separatist guerilla on the southern island of Mindanao. Something similar has been endemic in Aceh, at the western tip of Sumatra, where both the Dutch colonisers and the Indonesian central government have battled insurrections and rebellions.
Indonesia has had to contend with a few other centrifugal forces, one of which actually succeeded (and seceded): East Timor, which in 2002 became the 21st century’s first independent state. In the process, East Timor changed from being a fragment of a fragmented state to being the solid core of a compact state.
The implicit message of the Five Types is that compact is best, avoiding the logistical problems posed by the elongated, fragmented, perforated and protruded types. But is that really so? Cambodia, vaguely resembling a sea shell, is a fairly compact nation. That didn’t stop it descending into murderous anarchy when the Khmer Rouge took power in the mid-1970s, installing a regime that took its cue from the crazier aspects of Maoist Communism. China itself, morphologically compact, is torn between its high-performing coastal zone, an underdeveloped hinterland, and a far west forever rumbling with the distant thunder of separatism.
Perhaps these morphologies are the star signs of geopolitics: a fairly random way to categorise states and territories, which may or may not behave like the categories they’re placed in predict they will. Maybe the Five Types are a parlour game after all…
Read the whole story at Strange Maps.
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As we agree with Virgil that we should “trust not too much in appearances,” we might send clearly-magnified birthday greetings to Alexis-Marie de Rochon; he was born on this date in 1741. An astronomer, physicist, and inveterate traveller, de Rochon worked extensively in optics and lens design– and is probably best remembered as the inventor of the retractable telescope, the spyglass.
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