Category Archives: eclipse

Science Fair Ideas: Measuring the Moon’s Diameter

1941FebPSIf Junior is looking for a science project that can be completed in one evening, the teacher will be suitably impressed when Junior announces that he will measure the diameter of the Moon. All that’s required is a window through which the moon is visible and a couple of pieces of tape. Masking tape would probably work the best, but you could also use a couple of Post-It notes. You’ll also need a card through which you cut a hole.

Place the strips of tape on the window 1-1/4 inches apart. Then, you move the card away from the window, and keep looking through it until the moon appears to fill the space between the two pieces of tape. Measure the distance between the card and the window. At this point, the proportion of the two distances is the same as the proportion between the moon’s diameter and the distance between the moon and the earth.

Let’s say, for example, that Junior measures the distance between the card and the window as 137-1/2 inches. (Ahem, and if he does the experiment correctly, that’s the number he should get, assuming that the moon hasn’t changed size.)

According to NASA, who has been there, the moon is 238,855 miles from the earth. So we have a ratio:

1.25 / 137.5  =  X / 238,855

If Junior’s algebra is a little bit rusty, he can use this online calculator to get the answer of 2171.4 miles. According to space.com, the actual diameter is 2159.2 miles, so we would say that Junior’s method is pretty close.

1941FebPS2The experiment appeared 80 years ago this month in the February 1941 issue of Popular Science, which also carried some other astronomy experiments and demonstrations. For example, shown here is a demonstration of a solar eclipse, using a lamp for the sun and a tennis ball for the moon. One of these would be an excellent project in preparation for the June 10, 2021 annular eclipse or the April 8, 2024, total solar eclipse, both of which will be visible in North America. The magazine even shows how to demonstrate the orbit of a comet using an electromagnet to simulate the sun’s gravitational pull on a steel ball simulating the comet.

 

 

Eclipse of June 10, 2021

The photo above was taken in Bavaria at sunrise during the eclipse of May 31, 2003.  That was an annular eclipse, meaning that the sun is never entirely obscured by the sun.  Because the moon is slightly too far away, there remains a ring of sunlight.  It’s essentially the same as a partial eclipse, in that the world does not get appreciably darker.  It’s an interesting phenomenon, but not particularly amazing.  In most places, if nobody told you it was in progress, you might not even notice.  For example, I drove to Springfield, IL, to see the annular eclipse of May 10, 1994.  It was somewhat interesting, but there really wasn’t much to see.

There are two exceptions however, one of which is shown in the photo.  At sunrise and sunset, the disc of the sun is visible.  So if the annular eclipse (or a partial eclipse) is happening at sunrise or sunset, it will be quite apparent.

Path of June 10, 2021, eclipse. NASA image.

Path of June 10, 2021, eclipse. NASA image.

There will be an annular eclipse in North America on June 10, 2021.  It’s drawn little attention, since most of the path of annularity will be over unpopulated areas in Northern Canada, Greenland, and Siberia.  Much of the Canadian path is over Hudson Bay and James Bay.  So unless you’re one of the few thousand Canadians living in the path, the event will be of little interest.

However, the one exception where the eclipse is visible over inhabited areas is also the one place where the phenomenon will be most interesting:  The partial or annular eclipse will be visible at sunrise in Northwestern Ontario, near the city of Thunder Bay.  In Thunder Bay, the sun will be about 70% covered by the moon at sunrise, and the sunrise should clearly show the partially eclipsed sun.  Just a few miles northeast of Thunder Bay, there will be an annular eclipse at or near sunrise, which should result in a view similar to the one shown above.

I have two viewing locations in mind.  I’ve already made a hotel reservation in Longlac, Greenstone, Ontario, which is 305 km from Thunder Bay along the Trans-Canada highway.  The lawn in front of the hotel seems to have a good view of the sunrise.  From my home in Minnesota, it’s about a 9 hour drive.  That’s actually my backup plan, since I was already able to make a refundable hotel reservation.  My primary viewing location is Macleod Provincial Park, where the campground is next to a lake, which seems to have a good view of the sunrise.  Camping reservations, however, are only available five months in advance.  So in January, I plan to make reservations, and after they are secured, I’ll cancel the hotel in Longlac (and I’m sure it will get snatched up quickly, since it’s one of the few hotels in the path of annulaity.)

It should be a spectacular view, but there are two possible problems.  The first is the possibility of cloud cover, since there appears to be cloud cover about 60% of the time in this part of Ontario.  As we did in 2017, we’ll just have to hope for the best, and perhaps plan to drive a few miles to a break in the clouds.

The other potential problem, of course, is COVID-19.  Since March, the U.S.-Canadian border has been closed to non-essential travel, and this trip is clearly non-essential.  Again, I’ll have to hope for the best.  If the border remains closed, there will be about 16% coverage of the sun at sunrise at home in the Twin Cities.  So it won’t be particularly spectacular, but it will be worth getting up to view.

But as one heads northeast, the coverage gets greater. For example, in Duluth, MN, there will be about 40% coverage of the sun as the sun rises over Lake Superior. Just south of the border at Grand Portage, the coverage will be about 70%.  Anywhere along the North Shore of Lake Superior between these two points, the view should be spectacular as the sun rises over the lake.  So if the border is still closed, that’s probably where I will be.

Other cities in North America will experience a spectacular sunrise that morning. In Toronto, for example, the coverage will be about 72%. Philadelphia, New York, and Boston will all have coverage of more than 70%. Winnipeg will have about 40% coverage at sunrise, and much of Saskatchewan will have at least some coverage at sunrise. Further west, Fairbanks, Alaska, is the only other North American city with anything to see, with about 24% coverage at sunrise.

 

 



October 1, 1940 Eclipse

1940Oct1WashEveStarToday marks the 80th anniversary of the total solar eclipse of October 1, 1940, which was visible in Colombia, Brazil, Venezuela, and South Africa.

One focus of research for this eclipse was its effect upon the ionosphere and radio propagation. As shown from the clipping above (Washington Evening Star, Oct. 1, 1940), scientific teams from the National Geographic Society and Brown University had travelled to Patos, Brazil, and had photographic equipment at the ready. Unfortunately, however, a thick layer of clouds prevented visual study. Other experiments, however, focused on radio propagation and were presumably unaffected by the clouds.

In preparation for the radio studies, the National Bureau of Standards had previously published data regarding normal ionospheric conditions on the date of the eclipse.



March 7 1970 Eclipse

Crowds descending on Virginia to view 1970 eclipse. NASA photo.

Crowds descending on Virginia to view 1970 eclipse. NASA photo.

Today marks the 50th anniversary of the total solar eclipse of Saturday, March 7, 1970.  As I previously recounted, this was the first eclipse I witnessed.  That eclipse began in the Pacific and had a path of totality that crossed southern Mexico before entering the Gulf of Mexico.

Then, the shadow hit the United States , first in Florida, then Georgia, then the Carolinas and Virginia, then grazing Maryland before heading back out to sea, saying goodbye to the United States at Nantucket.

For those with Learjets, it then crossed Nova Scotia, Newfoundland, and the French island of Miquelon, before heading out to sea again into the North Atlantic.

Where I was in Minnesota, it only covered 47% of the sun at high noon. If nobody had told me about it, I probably wouldn’t have noticed. It didn’t get dark outside, and no animals were confused by sudden darkness. But that day, it was the biggest deal in the world. The moon contained fresh footprints of Americans who had walked on its surface less than a year earlier. Now that same moon was casting its shadow over me.

To me and my fellow third graders, it was presented as a big deal. And it was a big deal. If there had ever been any doubt about it, yes, the moon went around the earth, the earth went around the sun, and sometimes they got in the way of each other. Any third grader could see tangible proof.

In school, we had learned all about umbras and penumbras, and by the time the big day came, I was an expert on all things eclipse. With a shoebox, some foil, and a note card, I constructed myself a pinhole viewer. I figured that if a pinhole was good, then a giant hole would be even better. Fortunately, my mom corrected my error and got the viewer in good working order.

I pointed the box at the sun coming in the window, and sure enough, there was a little crescent shape of sunlight coming in through the round hole, plainly visible on the note card.

Perhaps I was a little disappointed at the tiny size of the image, but it didn’t matter. Right there in my shoebox was proof positive that the moon orbits the earth.  I didn’t have to take anyone else’s word for it.  The proof was right before my eyes.

The home movie here shows some of my contemporaries in North Carolina who had the fortune of being in the path of totality:

From our location, we had to turn on the TV to see the full effect, and we witnessed the darkened skies and the amazed reactions of those who went outside to see it. I don’t remember too many details about the TV coverage. Mostly, I remember some poor confused rooster in Georgia crowing in the middle of the day.

I believe it was the CBS coverage that I watched on TV fifty years ago today, and that broadcast is available on YouTube.  (You can hear the rooster at 22:23.)

Examining the confused rooster. CBS-TV via YouTube.

Examining the confused rooster. CBS-TV via YouTube.

 

Here is another reminiscence of another kid who was older than I was  and who lived closer to the path of totality.  As he recounts, he was able to talk his dad into driving him the 200 miles to totality where he was able to set up his telescope and take some photos.

When my friends and I got back to school the next Monday, the eclipse was the topic of conversation. We knew how the universe worked, because we had seen it with our own eyes. It was a big deal, and the kids remembered it.

In 1970, we were over a thousand miles away from the path of totality, and going to see it wasn’t really an option. But I envied those people and roosters on TV who got to see it in person.

The next total solar eclipse in North America will take place on Monday, April 8, 2024, just over four years from now. The path of totality will be a narrow strip passing through Mexico and Canada, and the states of Texas, Oklahoma, Arkansas, Missouri, Illinois, Kentucky, Indiana, Michigan, Ohio, Pennsylvania, New York, Vermont, New Hampshire, and Maine.  The path of totality includes a number of large cities, including, San Antonio, Austin, Fort Worth, Dallas, Little Rock, Indianapolis, Cleveland, Buffalo, and Rochester.  That path through Canada will include Windsor, ON, and Montreal.

My family went to see the 2017 eclipse, and the 2024 eclipse will be within a days’ drive of most of the population of the United States.  It’s an unforgettable experience, and you should plan on seeing it, just over four years from now.  It will be a school day, and if 2017 is any guide, most schools will fail to do anything meaningful.  I rarely encourage truancy, but kids should skip school that day, and instead travel to the zone of totality.  When I’m substitute teaching, I tell kids to ask their science teacher on the first day of the 2023-24 school year if there will be a field trip to see the eclipse.  If the teacher balks, then I tell them they should plan on skipping school.  From where I live in Minnesota, it’s a day’s drive to Illinois or Indiana to view it.  Kids who are currently sixth grade and older will probably have their driver’s licenses by then.  And all of the kids probably have parents who can take them.

You should also pencil in the 2024 eclipse on your calendar.  Keep following OneTubeRadio.com, and we’ll certainly remind you.  My experience from 2016 is that if you make your travel plans about one year in advance, there will be plenty of inexpensive accommodations available.  If you are a student or parent, then you should plan on bugging the science teacher in September 2023 about organizing a trip.  Just as I tell the kids here, if he or she doesn’t seem enthused, then you should take matters into your own hands.

When I’m teaching a class, there are often one or two kids in the class whose parents took them to see the 2017 eclipse.  I ask them if it was the coolest thing they had ever seen, and they invariably say that it was.  If you had asked me fifty years ago, I would have said that it was pretty cool, even though I was stuck mostly watching it on TV.  It took 47 years to actually go see a total eclipse in person, and I can vouch for the fact that it was indeed the coolest thing ever.



Transit of Mercury, November 11, 2019

Monday morning in North America, there will be visible a transit of Mercury. The innermost planet will pass directly between the sun and Earth, and will be visible as a small black dot.

The event will begin at 7:35 AM Eastern Time, 6:35 Central Time.  Mercury will be at the centermost part of the sun at 10:20 Eastern, 9:20 Central.  The event ends at 1:04 PM Eastern, 12:04 PM Central.  Local sunrise in Minneapolis is at 7:05 AM, and I”m hopeful that it will be visible in the rising sun.  I’m told that Mercury is too small to be visible with the naked eye, but I’m hoping that the sun’s low position on the horizon will make the small speck visible.

Even though the sun will be low on the horizon, you will need eye protection.  So dig out those eclipse glasses that you acquired for the 2017 eclipse.  If you are unable to view it, it will be live streamed from the University of Minnesota:



Solar Eclipse of August 7, 1869

1869EclipseSpectrumToday marks the 150th anniversary of the total solar eclipse of August 7, 1869.  The path of totality started in Asiatic Russia, and covered a tiny swath of China and much of Siberia before crossing the Bering Strait into Alaska and Yukon, and then through parts of the present day provinces and states of British Columbia, Alberta, Saskatchewan, Montana, the Dakotas, Minnesota, Iowa, Nebraska, Missouri, Illinois, Kentucky, Tennessee, Virginia, West Virginia, and the Carolinas.

The eclipse wasn’t the first to be photographed.  Those honors go to the eclipse of July 28, 1851, which, according to Wikipedia, produced the first scientifically usable photograph.  It does have the distinction of being the first to provide detailed spectroscopic images of the corona, which revealed an element believe for many years to be “coronium“.  It took 70 years to realize that the spectrographic line was not a new element, but instead iron at over a million degrees Kelvin.  The image shown above left was prepared by Prof. Charles Augustus Young of Dartmouth College, who was part of a team at Burlington, Iowa.  The same team produced the photo shown below:

1869EclipseBurlingtonPhoto

1869EclipseOttumwaPhotoAnother team left Burlington for Ottumwa, Iowa, but was beset by problems.  They had forgotten their chronometer in Burlington, and the telescope clockwork was damaged in transit.  Notwithstanding these difficulties, they managed 34 photographs, including four of totality, one of which is shown at left.

Another team was headed by Prof. William Harkness of the U.S. Naval Observatory. This team constructed a temporary observatory at the northwest corner of Second and Short Streets in Des Moines. Harkness reported that this vacant property on the west bank of the Des Moines River had a horizon almost devoid of obstructions.  “Short Street”  no longer exists, but according to the 1869 Des Moines city directory, it ran from the Des Moines River to Third Street (only a little more than a block, hence the name).  From the description of the observatory being on the west bank, it would appear that the building was near the current site of Wells Fargo Arena.1869EclipseDSMobservatory

A local contractor, one F.T. Nelson was retained to build the structure, shown at right.  This team also obtained multiple photographs and spectrograms.   The sketch below is the eclipse as seen through their four inch telescope.

Carptenter F.T. Nelson's listing in the 1869 city directory.

Carptenter F.T. Nelson’s listing in the 1869 city directory.

1869EclipseDSMsketch

The August 13, 1869, issue of the Cedar Falls (IA) Gazette carried this account of the eclipse. Those of us who witnessed the 2017 eclipse concur in the accuracy of this report. Indeed, from our viewing point in Hastings, Nebraska, we also had the added tension that “the forenoon was slightly hazy, but it cleared away and left no obstruction while the eclipse was passing.”

THE TOTAL ECLIPSE

Its Appearance in Cedar Falls

Government Observations.

Report of the Party, &c., &c.

It is not often that an opportunity is offered to witness so wonderful an exhibition of nature as the eclipse of Saturday last. Those who witnessed this extraordinary spectacle intelligently, will never forget its impression. It excites the most lively feelings of awe and wonder, and a breathless intensity takes possession of one as he gazes upon this grand movement in the heavens. The sight certainly gives one, a clearer view of the infinite majesty and power of the Great Being, and seems to speak directly to us of His greatness. The day was favorable, the forenoon was slightly hazy, but it cleared away and left no obstruction while the eclipse was passing.

The parties of observations were quite successful. Cedar Falls was made one of the points of observation by the Government, and will hereafter be one of the points from wliich calculations will be made. The party sent out by the Government to take observations iu this city were Ed. W. Horr, son of Dr. Horr of the Smithsonian Institute, and Wm. I. Anderson and W. W. Wormood, of Dubuque.

1869CedarFallsGazette

References



South American Eclipse of 2 July 2019

NASA eclipse imageIn preparation for the total solar eclipse of 2 July 2019, which will be visible in Chile and Argentina, I have updated and translated into Spanish my “Take Your Kids To See The Eclipse” page.  You can view the 2017 English version at this link.

En preparación para el eclipse solar total del 2 de julio de 2019, que será visible en Chile y Argentina, actualicé y traduje al español mi página “Lleve a sus niños a ver el eclipse”. Puedes ver la versión de 2017 en inglés en este enlace.

 

Einstein and the Eclipse of 1919

1919 eclipse positive.jpg

Eclipse as seen on Principe. Wikipedia photo.

Today marks the 100th anniversary of the eclipse of May 29, 1919.  The total solar eclipse, which darkened the skies over a band from South America to Africa, had the distinction of having the longest totality (6 minutes 51 seconds) of any since 1416.

Einstein 1921 by F Schmutzer - restoration.jpg

Einstein in 1921. Wikipedia image.

But the eclipse was most notable as making possible an experiment that demonstrated one of the predictions of Albert Einstein‘s General Theory of Relativity published in 1915. The gravitational pull of a large object (such as the sun) would bend light waves passing close by, and Einstein predicted how large the effect would be. He noted that a solar eclipse would be the perfect opportunity to prove or disprove the theory, since stars close to the sun would be visible. Their “correct” location in the sky was known. If they could be observed in the “wrong” location, then the measured location would confirm his theoretical findings.

The first attempt was done in conjunction with the eclipse of August 21, 1914. An expedition made up of German and U.S. astronomers traveled to Crimea to observe the eclipse. Unfortunately, Germany declared war on Russia on August 1. The German scientists were either sent home or taken prisoner. The U.S. astronomers were not detained, but clouds prevented the necessary observations.

Dyson (left) and Eddington (right). (Photo credit.)

Dyson (left) and Eddington (right). (Photo credit.)

The 1919 eclipse was the next opportunity, and an experiment was organized by British astronomers Frank Watson Dyson and Arthur Stanley Eddington. This came to be known as the Eddington experiment.  Rather than place all eggs in the same basket, as happened in Crimea, the 1919 experiment would have observations taken at two sites: Sobral, Brazil, and the island of Principe off the west coast of Africa.

In Principe, even though clouds obscured the sun until shortly before the eclipse, the team was able to make several photographic plates, one of which showed the background stars clearly enough. The positions did confirm Einstein’s predictions.

While the scientific community was slow to fully accept the findings, the popular press jumped on board, and Einstein’s name became a household word as a result of the experiment.  The news clipping below, for example, calling the experiment “the greatest discovery in history” appeared in the Washington Times on November 9, 1919.

1919Nov9WashTimes



Eclipse of April 8, 2024

2024 Eclipse Path.  NOAA image.

2024 Eclipse Path. NOAA image.

As we did in 2017, OneTubeRadio.com will provide full coverage of the April 8, 2024, total solar eclipse.

This is exactly five years from today.  Little preparation is needed at this point, but you should make a mental note to travel to the path of totality, which is less than a days’ drive from most of the United States.  The total eclipse will be visible in parts of Texas, Oklahoma, Arkansas, Missouri, Illinois, Indiana, Ohio, a tiny piece of Michigan, Pennsylvania, New York, Vermont, New Hampshire, and Maine.  The path of totality also passes through Mexico and Canada.  Major cities in the path of totality include Dallas, Little Rock, Indianapolis, Buffalo, Cleveland, and Montreal.

The eclipse will take place on a Monday.  For the 2017 eclipse, we made our hotel reservations about a year in advance, and paid the normal rate with plenty of availability.  So if you plan on booking in April 2023, you should have many options.  Also, in late 2023 or early 2024, you should order your eclipse glasses.

If you have kids who will be in school, plan on taking them out of school that day.  Unfortunately, the 2017 eclipse showed that American schools had an irrational fear of the eclipse and actively prevented children from witnessing it.  If you believe that your child’s school is more enlightened, then on the first day of the 2023-24 school year, you should have your children ask the science teacher if the school is planning a field trip to see it.  If the teacher balks, then your children should let him or her know that they will be absent the day of the eclipse.

This is an entirely reasonable request for most schools.  For example, students in Chicago could be placed on a school bus and taken to see the eclipse only a couple of hours’ drive away in Indiana.  The expense will be less than other field trips taken to amusement parks, movies, etc.  This is true for schools in many cities.  They have the opportunity to let the kids witness an amazing scientific event, but only if they do some basic planning.

But I predict that this won’t happen, since most schools won’t think of the possibility until after it’s too late to make the necessary plans, or they’ll have the same irrational fears that showed up in 2017.  It’s the duty of the students to pester the administration so that the necessary plans are made sufficiently in advance.  And as I explained in 2017, if the school fails to act, then it’s reasonable for children to skip school on April 8, 2024.

 

 



Solar Eclipse of February 26, 1979

1979 eclipse 3.tif

1979 eclipse as seen in Bozeman, Montana. Wikipedia photo.

Today marks the 40th anniversary of the solar eclipse of February 26, 1979.  The path of totality passed through Washington, Oregon, Idaho, Montana, and North Dakota before entering Saskatchewan, Manitoba, Ontario, Quebec, and the Northwest Territories. From Canada, the path of totality entered the north Atlantic before ending in Greenland.

The path through Winnipeg, Manitoba, was tantalizingly close to my home in Minnesota, but I was unable to travel to see the spectacle. I had to settle for 90% coverage (in other words, millions of times more sunlight) where I was. I did vow that I would see the next one, in 2017, and I did.

This video shows coverage of the eclipse as totality passed through Winnipeg: