Live Blogging: Solar Eclipse 2017

7:44am The sun is rising here in Toronto. He’ll take a nap in the early afternoon between 1:10-3:40pm. The peak is expected around 2:30pm. Stay tuned for more updates!

8:55 We have to consider ourselves lucky we can see a solar eclipse at all. In fact, this phenomenon is not a direct consequence of any profound physics law: the radius of the Moon and of the Sun, and their distance from Earth, just happen to be in the right ballpark so that their apparent size match almost exactly. In a few million years, the orbit of the Moon will increase up to a point when eclipses won’t be as exciting anymore. This is usually referred to as a cosmic coincidence. Other “mysteries” in physics, such as the value of the mass of the Higgs boson, are often compared to solar eclipse. People tend to look for explanations even when in fact it’s just a matter of chance if two things appear to be correlated to each other.

10:00am In the past, eclipses were usually associated with very bad omens. But the outcome was not always as bad as predicted. For example, the Greek historian Herodotus reported an account of what happened during a battle fought between the Central-Asia Medes and the Lydians in 585 BC, known as the Battle of Halys. Aylattes, king of Lydia, and Cyaxares, king of Medes, had been at war for 15 years. Just before the eclipse occurred, they were battling near the Halys River (now Kizilirmak) in what is now central Turkey. During the fighting, the skies darkened and the sun was obliterated for a while, leading to both parties halting the combat and negotiating a peace agreement. Herodotus also mentions that the eclipse had been predicted by Thales of Miletus. Similar statements were later made by Cicero and Pliny the Elder. You can listen to Dan Carlin’s recount of this epic battle in his podcast King of Kings ep.3.

10:30am Solar eclipse occur only at certain locations at a given time. Lunar and Solar eclipses tend to happen at intervals of one, five and six months from a particular start date. And the pattern repeats each 223 months (known as the Saros cycle).

astrokatie

Take note of the differences between lunar and solar eclipses. Credits: Katie Mack, Melbourne University @AstroKatie

The cycle works because three things need to happen to have an eclipse: first, the Moon has to be at “New Moon“. So you can get another identical one after a whole number of synodic months (i.e. the period of the Moon’s phases).  Second, the Moon’s path has to be crossing the plane of the Earth’s orbit around the Sun, so the three bodies are aligned. The orbit of the Moon is tilted compared to this plane by about 5 degrees, so you get an eclipse only if the New Moon happens just as the Moon crosses the line of the Sun. The period between these crosses is known as Draconitic months. After a period of time in which both a whole number of synodic months and a whole number of Draconitic months has passed, eclipses will start repeating themselves. That happens about 223 synodic months and 242  Draconitic months.

This nice video on YouTube gives a nice visual explanation of such complicated celestial mechanics!

11:30am If you’re in Canada, check this infographic and set an alarm!

Screen Shot 2017-08-21 at 10.34.58

Noon How do I watch it safely? Certainly, not with your naked eyes – you can seriously damage your retina. The best way is to get a pair of glasses such as the Celestron EclipSmart 2x Power Viewers. If you’re on a budget, you can build a pinhole projector (such as the one shown in the video, using the emptied box of your favourite breakfast cereals), or just try this out (credits: NYTimes):

  1. Put one piece of cardboard (or paper plate) on the ground.
  2. Poke a tiny, round hole into the other piece of cardboard.
  3. With your back facing the sun, raise the cardboard with the hole in above your head and aim the hole at the cardboard on the ground.
  4. The hole will project an image of the crescent shape of the eclipse.

1:00pm After Thale’s feat at predicting an eclipse (maybe just by chance?), the Ancient Greeks were able to make such predictions with a high level of accuracy despite the flaws in their understandings of the Solar System – most notably, they believed the Earth was fixed in the centre, and all the other bodies orbited around it in circles and “epicycles”.

NAMA_Machine_d'Anticythère_1

The Antikythera Mechanism. A trip to the  National Archaeological Museum in Athens is probably worth the long flight.

The most dramatic demonstration of their abilities is the famous Antikythera Mechanism, a sort of clockwork computer and orrery used to predict astronomical positions and to keep track the four-year cycle of athletic games. We don’t know exactly who, where and when built this contraption. Its origin are likely to trace back to the island of Rhodes in the First Century BC. Some argue that the astronomer Hipparchus of Nicaea or even Archimedes might be behind this incredible artifact, which pre-dates modern clocks by about a millennium. If you want to find out more about the discovery and the inner workings of the mechanism, I suggest the reading of Decoding the Heavens: A 2,000-Year-old Computer and the Century Long Search to Discover Its Secrets by Jo Marchant.

2.12pm here we go..

2:32pm That’s the best we can see in Toronto (about 75%)..

How did I take these photographs?

IMG_4504

Never throw anything away: you’ll never know what an old 5¼-inch floppy disk can be used for

The first photograph was taken by pointing my cellphone camera to the Sun through an old 5¼-inch floppy disk. The material they are made of (PVC) was manufactured thin enough to let some light shine through it. The hard part is actually…to find one! (credits: Elena Ferranti @ef_lookoutkid)

 

As for the second one, I simply aimed my iPhone camera to the sky, so the Sun appeared in the upper third of the screen. For some reason, a dim reflection appears in the lower third, which is the part I cropped to show the eclipse. A colleague of mine discovered this trick by chance.

3:30pm Now that the solar eclipse in North America is over, it’s already time to think ahead. Book your flight to Toronto for the 8th of April 2024. In case your plans do not include a trip to Canada, but still want to find your way as a faithful follower of the Path of Totality, you can find out other locations using this amazing tool on the Washington Post website.

If you enjoyed this live blogging, you may want to read  a similar account written by Maria Mitchell, who entertained her readers…in 1869.

Finally, it may be time to chill out by listening to some music by one of the best band of the history of rock.

Until next time!

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