The Summer Solstice and Calculating the Earth's Circumference

Eratosthenes used the Summer Solstice Sun, an obelisk, and a well to calculate the Earth's circumference in 2300 B.C.


Today is the Summer Solstice, the longest day of the year (for us North of the Equator) and the official start of the summer season. For many people, this serves as a chance to celebrate what is, for many people, their favorite season.  For astronomers, and especially those intersted in the history of the science, the Summer Solstice also marks a major anniversary in the quest to undestand the universe and our place in it.

An obelisk like this one was the first piece of the puzzle.
Eratosthenes was the first man to measure the circumference of the Earth. The whole drive to do such an audacious thing came from curious stories coming out of Egypt. In Syene, Southern Egypt, it was said that at noon on the longest day of the year, and only on this day and at this time, the Sun would illuminate the water at the bottom of a deep well that was in shadow at every other time in the year. However, in Alexandria, where Eratosthenes served as chief librarian of the great Alexandria library, the Sun cast definite shadows at noon on the Summer Solstice. So how could this be?

This is supposedly the well Eratosthenes used for inspiration.


Well, Eratosthenes was quick to realize that, for this to happen, the Earth had to be spherical. However, while lesser minds may have been content in this knowledge, Eratosthenes was not, he thirsted for more. Calculating the angle of the shadows, Eratosthenes determined that the shadow in Alexandria was at an angle of about 7.2 degrees, or about 1/50th of a circle. Thinking in terms of the big picture, he reasoned that the distance from Alexandria to Syene was about 1/50th the distance around the Earth. So, finding the distance between these two cities and then multiplying by 50 would give the circumference of the Earth, easy in principle but not in practice. As hard as it may be to believe, Eratosthenes hired a man to pace out the distance between the two cities! Despite no one having paced out such a great distance before, the distance was determined with remarkable accuracy, which resulted in Eratosthenes coming to a circumference within a few percent of Earth's actual circumference of just under 25,000 miles.

Not bad for the 3rd century B.C.

More Ancient Astronomy

The Planet of Bethlehem?
A History of Cosmology: Prehistory to Present
Galileo's Fingers Go on Display.
Renaissance Astronomy: Part 1
Renaissance Astronomy: Part 2
Renaissance Astronomy: Part 3
The Equinox and a Magic Show from the Maya
Ancient America: the Moundbuilders
Ancient America: the Southwest
Ancient Egypt
Classical Greece
The Summer Solstice Sun and the Size of the Earth
The 1833 Leonids: History's Greatest Meteor Storm
The 10 Brightest Comets of All Time
Ben Franklin and the Truth About Daylight Savings Time

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June 5, 2012 Transit of Venus: Huge Photo Gallery, High-Res Images

The weather didn't look good initially, with the sky dominated by spotty clouds with only small breaks. Fortunately, come transit time, the clouds started to break up, allowing for some amazing photos of this last such event for 105 years. Unfortunately, living in the Eastern Time Zone, I wasn't privy to the whole event, withthe Sun setting about 3 hours into the transit. Still, the event was spellbinding and not worth missing for the world. Hopefully, you got a chance to observe the transit for yourself but, if not, enjoy the gallery.

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100,000 Hits!

Just noticed my hit counter rolled over 100,000 today. Woo hoo! Thanks to everyone for reading (and hopefully helping me by clicking my Examiner links!). I'll try to get posting more soon.

Today is Astronomy Day!

Today is a holiday that many people don't even know exists: International Astronomy Day.

With humble origins in as an attempt at public outreach by the Astronomical Association of Southern California, the effort to bring astronomy to the masses, often city dwellers, quickly grew in popularity to the point where the holiday eventually went national, and then international. Now, nearly 40 years after the first Astronomy Day (1973) the holiday continues to grow and become more relevant?

Why the part about being relevant? Simple: dark skies are going away fast.

When the first Astronomy Day was launched in 1973, the whole idea was to set up telescopes in public places where astronomers could show members of the general public the wonders of the universe. Naturally, to guarantee that the public would show up, the telescopes had to be set up in urban/suburban locations, areas that are not all that good for astronomy. Obviously, by looking at the success of the holiday, people are seeing things in the telescopes.

Lesson of the day: you can do astronomy from just about anywhere.

For starters, the Moon is always visible as it is the second brightest thing in the sky after the Sun. Believe it or not, there are astronomers who spend the majority of their telescope time studying the Moon. Second, planets. All of the planets are generally of 0 magnitude or brighter, thus visible from all but the most light polluted areas. Being bright targets, the planets are also good targets for examination by city-dwellers. For suburbanites, binary (double, triple, etc.) stars are also a lot of fun to lok at because they, too, can be observed in all but the worst of lighting conditions.

So yes, the dark skies are going away more every year but, if you know what to look for and are content with the fact that you can't see deep sky nebulae, galaxies, and clusters from your backyard, there is plenty of fun to be had with a telescope in a city.

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Nikon D400 Speculation: 16Mp, Full Frame, $1999 Retail Price

Nikon has been very busy since the start of the new year. First, there was the flagship D4, then the more economically-priced, 36Mp D800 dSLR, which is being hailed by some as the greatest camera ever made. Now, in going high Mp with the D800, Nikon seemed kind of stupid in that they abandoned the low-Mp, high ISO $3,000 market, which they had exclusive domain in with the D700. So, why would Nikon cede its monopoly in this market niche?

Answer, it won't, the D400 will be coming out later this year and it will be poised to take the place of the D700, but for $1,000 less than the D700's introductory price.

So, why such reason for hope?First of all, Nikon has been very generous in letting features trickle down from its top-tier cameras into lower-priced models, albeit after the new kings of the hill have been out awhile. Example: the D700 was 95% of the D3 but at half the cost. Another example: in 2010, Nikon essentially obsoleted its $1,800 D300s with the$1,200 D7000, with the D7000 equaling or beating its older, more expensive brother in every respect except affordability. With the D400, this could very well happen again.Another reason for hope: pricing. Ever since Nikon split its pro D# camera lineup into low and high resolution models, the high-res camera always cost about 35% more than the low-res one. Example: Nikon's D3 sold for just under $5,000 at release. Upon announcement, the D3x identical to the D3 except for its double resolution sensor) was priced at $8,000. Now, looking at the high-res D800 that sits at the $3,000 mark, it would fit the trend for Nikon to cram the 16Mp, FF sensor of the D4 into a D300 body, call it the D400, and sell it for $2,000.

Third reason for hope: the market void lack of a D700 creates. In phasing out the D700, Nikon leaves a market which it monopolized: an 'affordable' FF camera with its main selling point being speed and high ISO performance. Simply put, there was no direct competitor as the $3,000 cameras from Canon and Sony were high-Mp clunkers in comparison to the D700. For going on 4 years, Nikon had this market all to itself and it makes no financial sense to abandon it now.

In making the D400 16Mp FF, Nikon would be both filling the market gap it created and, at the same time, making its customers happy, a win-win for everyone involved.

In the end, though, only time will tell if The D400 will be a FF camera using the D4's sensor. Still, though, it's still fun to speculate on what the D400 could look like, so here goes . . .

16Mp FF sensor
6 fps (8 with battery grip)
95% viewfinder coverage
Single CF slot
Only a 3:2 aspect ratio
LCD: 3.2” non-brightness adjust
Less movie clip time as compared to D4


In all, the D400 will be a D4 lite, with some specific changes in order to make the D4 more appealing to people to shell out the extra money. After all, Nikon can't make the D400 too like the D4, lest no one would buy the latter. Still, though, by looking at how feature-dense the D7000 is and for the price it sells for, a sub-$2,000 FF camera from Nikon no longer seems out of the question.

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Life Isn't Fair (Just Accept It) and the Value of Hard Work

Life is not fair and you just need to accept it, that old bit of advice can go long way in keeping you from going stark raving mad in some situations, which brings us to the topic of this somewhat off-topic piece of advice. In case you haven't heard, Fox News host Greta VanSusteren just got a Nikon D800 from B&H Photo-Video, and many people aren't happy about it. .

The issue many people have: VanSusteren used her celebrity status to jump the line and got the camera virtually overnight while others have been waiting for over 2 months (and counting) for their D800 to arrive.

So?

Like it or not, life simply isn't fair, sorry. VanSusteren is a world-famous journalist and, frankly, it should come as no surprise that, when she goes in to buy a camera (she probably went to B&H since it is based in New York City, just like Fox News) and said that she was looking for a camera to take to the recently-divided Sudan, top brass decided to just let her buy one on the next shipment that came into the store rather than wait her turn in line like all the Average Joes and Janes had to do..

Is it fair? No. Should you be upset? No t that, too.

Obviously, in order to get a show on Fox News, you have to have talent, a lot of it. Think about it: how many reporters never get past the local newspaper? The vast majority. When it comes to getting on TV in the first place, only a lucky, talented few get to do so in their local markets, few of whom then move on to something even bigger, the national news scene. Obviously, to get as far as she did, VanSusteren had to be in the top percentile of journalists in regards to both reporting and television skills. Obviously, to excel at both sides of reporting the news to such an extent as to get one's own national TV show is a big accomplishment. My take: Greta worked hard to get where she is today and, if she can use her hard-won status to jump the line and get a D800 right away, good for her!

The United States is an interesting study in human nature. In one vein, we value hard work but in the other, we often resent those who achieve success in whatever they choose to do (and the rewards success brings) through the hard work we so value. See the problem? Don't want to work? Well, you're a lazy oaf. Work too hard? Then you're a self-centered workaholic. Either way, you're screwed.

Whatever happened to going for the gold and being all you an be?

Another paradox in U.S. psychology: we want to be rich but are often resentful of the people who are rich. Think about it: who doesn't want to have a lot of money? Me? I'll take all the money I can get, thank you very much. On the other hand, whenever we see someone who lives in a huge house, drives an exotic car, or snaps pictures with a fancy camera, we often think the following: well, he/she has that, so why shouldn't I be able to, too?


Answer: hard work.


Generally speaking, people who put the most effort into their work often get the raises and promotions, which means more money to be made and spent on things like houses, cars, and cameras. Want to have nice stuff, the same stuff that makes you green with envy (or red hot with jealousy)? Well, work a little harder! Bosses recognize hard workers and, sooner or later, that hard work pays off. Yes, being the better worker can mean more work for you now but, in time, it will be you, not that slacker who you have to bail out all the time, who gets the promotion, the raise, and all the perks that go along with moving up on the chain of command.


The American Dream is, contrary to popular belief, not dead in the least. The dream is alive and well, but only for those people who are wanting to work for it. The problem in America: a lot of people are increasingly willing to just “get by” in their lives because they don't want to go that extra mile and work a little harder than the next guy, or girl. After all, most jobs pay by the hour, so why work any harder than you have to, right?


Wrong.


Yes, doing enough to just “get by” is fine for some people but, if you're one of these people who's content with mediocrity, don't go whining about not being able to have nice stuff or any of the perks that those who have made it enjoy. Bottom line: Greta VanSusteren worked hard, made it to the top of her field and is, thanks to her hard work, able to do things the ordinary person can't, so stop whining about 'fair,' get to work, and make something of yourself instead.

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Nikon Announces 24Mp, Wi-Fi Capable D3200

In case you haven't heard, Nikon just announced its D3200, which turned out to be pretty much exactly as the rumors said it would be, namely packing a 24Mp sensor and wi-fi connectivity. In these two areas, the D3200 mops the floor with every other APS-C Nikon dSLR to date. However, when it comes to the features that matter, the D3200 is just a toy for amateurs who need an in-camera photography help guide for tips on how to take better pictures.

My advice: if you're looking to buy your first dSLR, preorder your D3200 right now as it's sure to be a hot seller. If you're an advanced shooter who wants real functionality and user-friendliness, skip the D3200 as the other Nikons are better where it counts.

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