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Solar Eclipse, Part 5: Temperature Drop

Solar Eclipse, Part 5: Temperature Drop

Bring a sweatshirt with you on August 21! During the eclipse, the temperature may change 1/2 or 3/4 as much as it regularly does at night, based on your location and climate. This will likely be 10-15 degrees, but it could be more.

When the Moon blocks sunlight from reaching Earth, Earth’s temperature drops. Since we want to understand this phenomenon better, NASA has invited eclipse observers around the country to take part in an experiment. In order to become a citizen scientist and participate, all you need is the free GLOBE Observer app and a thermometer.

Image of the GLOBE observer app you can download for free and contribute to science during the eclipse.

You don’t have to be in the path of totality. You don’t even need good weather. As long as you are in North America, NASA can use the cloud and air temperature data you collect. If you are committed to observing the eclipse from beginning to end, this is a productive task you can perform during the stages of partial eclipse, and I would encourage you to do so.

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Solar Eclipse, Part 4: To Scale and Not To Scale

Solar Eclipse, Part 4: To Scale and Not To Scale

To scale or not to scale, that is the question;

Whether ’tis nobler in the mind to suffer

The slings and arrows of disproportions

Or to take a ruler to that sea of troubles

And, by measuring, correctly depict them.

…                      Aye, there’s the rub.

Shakespeare aside, when you see a diagram depicting an eclipse, a caption oft accompanies it, clarifying that it’s not to scale. Why? Here’s why. Look at this diagram. This one is to scale.

This diagram of the Sun, Earth, and Moon is to scale. The night-time side of the Earth is not darkened in this diagram.

Look how much space there is between the Sun and the Earth! Can you even see the Moon? I programmed it into the plot; it’s just so small. A diagram that is to scale helps us understand the relation between the sizes of the celestial bodies and the relative distances between them. Nevertheless, it does not help us understand what is going on during an eclipse. This is one reason why we have diagrams that are not to scale.

This diagram of the Sun, Earth, and Moon is not to scale. This diagram shows the configuration of these celestial bodies during a solar eclipse.

Here we can see that the Moon is in between the Earth and the Sun, and the Moon’s shadow falls upon the Earth. This doesn’t happen every time the Moon passes between the Earth and Sun because the shadow usually flies over the North Pole or under the South Pole. During two different intervals of about 33 days each year, the Moon’s shadow could fall upon the Earth. Only during these intervals can we get eclipses (both lunar and solar).  Whether an eclipse happens depends on the Moon’s phase. Which type of solar eclipse occurs (total, annular, or partial) depends on the relative distances between the Earth, Moon, and Sun. These are constantly changing because orbits are not perfect circles but ellipses. I hope to go into further detail about this in a future post. This should at least help us understand why to scale diagrams and not to scale diagrams are both helpful, but for different reasons.

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Solar Eclipse, Part 3: Eclipse Glasses

Solar Eclipse, Part 3: Eclipse Glasses

Looking at the Sun is usually a bad idea. Over the weekend I chatted with an optometrist, and he made it clear that permanent damage can be done to your eyes even if you don’t feel any pain. Safe ways to observe the solar eclipse include making a pinhole projector or simply wearing eclipse glasses. While I haven’t found any eclipse glasses that seemed unsuitable, the American Astronomical Society recommends five manufacturers: American Paper Optics, Baader Planetarium (AstroSolar Silver/Gold film only), Rainbow Symphony, Thousand Oaks Optical, and TSE 17.

Here I am wearing sunglasses and eclipse glasses. I was testing a solar filter I had constructed for a DSLR camera using a solar filter sheet.

Eclipse glasses serve as neutral density filters that block 99.99% of light coming from anywhere. The only thing bright enough to be seen through them is the Sun. Although they are called “eclipse glasses,” you can look at the Sun through them on any day of the year. Eclipses are just the time it’s most tempting to direct your eyes toward that fiery ball. Sunglasses do not block enough light for safe direct solar viewing. We use sunglasses on a day-to-day basis because we want to see what’s around us while reducing the amount of sunlight reaching our eyes indirectly. If you experience the total eclipse, only during totality is it safe to look at the Sun without protection. Use eclipse glasses at all other times.

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Solar Eclipse, Part 2

Solar Eclipse, Part 2

Will the sky get dark enough during the eclipse for us to see other stars in the sky? During totality, yes! When the eclipse is total, the light that reaches us from the Sun is thousands of times dimmer than a partially eclipsed Sun. (This is why you should wear eclipse glasses at all moments except the brief two minutes of totality.)

Using Stellarium, I took a snapshot of what the sky will look like near the eclipsed Sun.

A snapshot with Stellarium software of what will be in the sky near the eclipsed Sun on 21 August 2017. Although the coordinates used for this snapshot are those for Weiser, Idaho, to the naked eye there will be little difference between this view and that for any other location in the path of totality.

Notice that the bright star Regulus will be very close to the eclipsed Sun. Regulus is the same star near which a conjunction between Jupiter and Venus that Stellarium gives as June 17 in the year -1 (which I assume corresponds to 2 BC because Stellarium uses a year zero) may have been the “star” the Magi followed (I plan to write more extensively about this in the future).

Both Mars and Mercury will be close to the Sun in the sky. I am especially excited at the prospect of seeing Mercury for the first time. I have tried on several occasions and have not yet succeeded. For those who observe not too close to sunset, Venus will also be in the sky, leading the Sun, about four times further from the Sun than Mars. Jupiter will be a little further away from the Sun than Venus, and in the opposite direction. From where I’ll be observing, Jupiter will still be below the horizon, but it will have risen for most observers in the US.

A more zoomed out snapshot with Stellarium software. The coordinates chosen for this one are those for Carbondale, Illinois. The brightest object in the sky during the total eclipse will be Venus. Jupiter will also be bright. Bright stars that are not pictured but will probably be in the sky, depending on your viewing location, are Sirius (southwest of Procyon), Capella (northwest of Venus), and Arcturus (north of Jupiter). Make sure you don’t confuse these with Jupiter and Venus.

During the partial phases of the eclipse, although the light from the Sun will be reduced, it will still be brighter than a Full Moon (and you should not look at it without eclipse glasses). If any other celestial object will be visible, it’ll be Venus. Venus will be west of the Sun, in the constellation Gemini. Jupiter and Sirius are the next brightest objects. Don’t spend too much time looking at the planets and stars rather than the eclipse. Knowing ahead of time what will be up there, however, will undoubtedly enhance the experience.

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Solar Eclipse, Part 1

Solar Eclipse, Part 1

Oh wow! This August 21, the Moon’s shadow, a mere 60 to 70 miles wide, will flee across the United States in a reverse-Oregon-trail and continue through Charleston, South Carolina. If you are in the path of totality for this solar eclipse, you’ll see the Moon blot out the Sun for a mere 2-3 minutes.

In preparation for such a salient astronomical event, I’ve decided to do a blog series to cover at least some of what I’d like to share. I plan to show some configuration diagrams (to-scale and not-to-scale, that’s not a question), a view of stars and planets visible near the eclipse, tales of past eclipses, the science behind them, and a detailed script of what I’ll be doing during my two long-awaited minutes of amazement.

To start, I recommend checking out this interactive Google Maps tool to find out the specifics for your location.

This snapshot of the interactive Google Maps page when zoomed out shows the path of totality cross the US. Observers within the green or yellow lines can witness a partial eclipse.

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