Your Public Science

…and it has been for a LONG time. At least, since the late 1000BCE. There’s been a weird misconception that in the time around 5th to 15th century, we all thought our Earth was flat. Then Columbus struck out on his boat and upon returning changed it all.

Truth is, many different scholarly Greeks had discovered, proved, calculated, however you want to call it, that our Earth was indeed a big blue ball. In fact, once this development sprouted out of Ancient Greece in the centuries before the Roman Empire even got off the ground, the ideals of a spherical Earth pervaded through Europe clear into modern day. The idea of a flat Earth between educated peoples in the days of Columbus was next to none.

But how on Earth did we figure out the Earth was round way back before satellites and computers? Well, one man named Ἐρατοσθένης (Eratosthenes) was able to get the answer using simple math that another Greek, Πυθαγόρας (Pythagoras), developed. If you remember your right-angle triangles you might already know where this is headed.

Sunlight for Eratosthenes

In his publication of “Περὶ τῆς ἀναμετρήσεως τῆς γῆς” (On the Measurement of the Earth) he explained the details of his method. Eratosthenes read that on the summer solstice at noon in the city of Syene, rays from the Sun would reach the bottom of the deepest well. In other words, the Sun would be directly overhead. He knew that on the same day in Alexandria, the sun was not directly overhead. Since he assumed that Alexandria was basically due north of Syene, he figured that the arc distance between the two locations was roughly 1/50 of a full circle (7°12′) north of the zenith at the same time.

How Eratosthenes figured out the distance from Alexandria to Syene is a somewhat unsettled. Some say he hired someone to measure the distance, others says that he estimated the distance from the average time required for a caravan of camels to travel the distance, and another that he walked the distance himself. However it was measured, the distance was determined to be about 5,000 stadia.

With all this, he foudn his final value of 700 stadia per degree, which would multiply out to a circumference of 252,000 stadia. There were at least two different units in common use at the time, equivalent to 157.5 m and about 185 m. That put Eratosthenes’s value between 39,690 km and 46,620 km. The circumference of the Earth around the poles is now measured to be around 40,008 km. If you average ou, this puts Eratosthene’s answer within roughly 7.8%! All with shadows and simple math.

This method, while hindered by low precision data, was very accurate and was accepted for hundreds of years afterwards. Even other astronomers/geographers used his method and other methods in its likeness to further maintain the accuracy of the Earth’s circumference.

So there was an old mystery novel that set up the chilling night time scene with:

The big full moon rose over the horizon just at midnight.

Did anything strike you funny about this particular scene? Have you ever wondered why sometimes you see the moon during the day? Well, depending on what phase the moon is in you can figure out roughly when the moon rose and when it will set during any part of the day.

The Phases of Our Moon

It takes the Moon roughly 29 days to make a complete rotation around our planet and the above chart show the placement of the eight major phases the Moon takes and where it lies in orbit at that time. The detailed Moon phases show what we get to see from Earth at the time the Moon is in the location designated by the simple white and gray circle.

As the Earth sits in the picture remember that the spot closest to the sun would be Noon and the spot further away, in the dark, would be Midnight. From anywhere along the Earth you can put yourself and draw a straight line from that point to the Moon phase you want to see and that’s where it would show up at that time. (Provided the Earth doesn’t get in the way.) Say we’re at the top of the Earth, where the light and dark side meet, this is “sunrise” so if we drew a line straight up (looking straight up into the sky) we would see a half-moon. However, what if it was sunrise but we wanted to see the full moon? Well, if we drew a line to it, the Earth’s horizon would just touch that line. If we rotation anymore into the morning, the Earth would block our site. Therefore, if we looked for a Full Moon at sunrise it would have to be just setting over the horizon. If we stood on the other side at “sunset”, the opposite Full Moon would be right over head, and the Full Moon would be just coming into view over the horizon.

What about the New Moon? Well, since we’re looking at the dark side of the moon during that phase, no real light is bouncing off to show itself to us. However, the best time to see a New Moon is, of course, during a Solar Eclipse, when the Moon steps right out in front of the Sun and blocks its light temporarily.

So next time someone’s alibi includes the Full Moon rising at midnight, you’ll know something’s up.

I will be attending the:
AAM Annual Meeting and MuseumExpo™
May 22–25, 2011 • George R. Brown Convention Center • Houston, TX

It’s going to be fun!

Going to be attending too? Have some last second questions? Here’s a last second FAQ.

Also, they are providing a really cool online schedule to fit all your sessions together.

Google celebrating the manned space flight anniversary

Yuri Gagarin

On 12 April 1961, Yuri Gagarin became the first man to travel into space, launching to orbit aboard the Vostok.

Moving past all the political hate, the Soviet Union hiding all sorts of numerous facts and news from the public and the American’s fear and nerves as they scrambled to catch up to Russian tech and intelligence, there was a man who was ready to face the dragons of what traveling into space would be.

As the earlier European and Asiatic sailors began navigating their boats straight into the seemingly infinite ocean horizon, they had a wealth of things to cause them fear, make them wary of the trek. Hurricanes, serpents, unexpected banks without lighthouses, loss of food and clean water, and gods against them, yet there were countless sailors striking out. While many did not return, many did.

But then many years later we turned our boats to the cosmic ocean. Regardless of nationality, we humans, our brothers and sisters, struck out into space. Leading the way was Yuri.

So while we come around on the 50th golden anniversary of humans entering space, what have we achieved? Well, we’ve stepped foot on the moon. That’s nothing to sneeze at, but when did we achieve that? July 21, 1969, eight years later. Eight years was all it took from worrying about Gagarin loosing his mind to the unknowns of weightlessness and outer space, to taking a human all the way to the moon, jumping out, and hopping around on it.

It takes 29 years more before we launch our International Space Station in 1998. A semi-permanent residency in low Earth orbit. We’re now in 2011 and 13 years later, with the words from a certain president saying no more manned space missions, and a shuttle program that is being retired with no real ready replacement.

“Before this first flight there were reasonable suspicions that human beings weren’t made for this environment,” James Oberg, a NASA veteran, said. “And once Gagarin answered that question, I think every other discovery on every other manned spaceflight was just details. He answered the most challenging, the most awesome question by his performance.”

Gagarin had the courage to face the unknowns of space and defeated those dragons so that we would be able to sail further than we ever had before, into space.

We have crossed rivers; we have crossed oceans. We have crossed the cosmic river separating us from our moon, but we can go further. We must keep pushing the limit. We cannot shy away from the achievements waiting for us just past the moon.

To read more about Yuri Gagrin from AP and Wikipedia.

With this site my goal is to make some of the harder-to-grasp ideas in science easier to handle, so with this episode I wanted to appreciate some distances we have in our lives.

First, we all have heard of feet, meters, inches, kilometers, and most of us have at least heard about light-years, even if we haven’t used them ourselves; however, with light-years, we tend to loose our sense of estimation. It is hard for us humans to fully grasp a light-year, and what about an AU (astronomical unit) or a parsec (parallax arcsecond)? These measurements are employed with our neighbors in space. They describe great lengths across our universe, but what are these measurements?

Well, we’ll save how they were derived for a another time. Right now we’ll just focus on sheer distance.

Sorry, for you non-metric users. For a comparative table why I shy away from the Imperial/US system of measures here’s a sample of a mile divided down next to a kilometre.

So, now we know how far these new units, Parsec, AU, and Light-year, are in kilometers. But again, how long are these distances? One Parsec is equal to 30,857,000,000,000 kilometers? Think about what 30 quadrillion feels like in your mind. Roughly 6 million people in the Houston, TX city and surrounding metro areas, about 6.7 billion people living on the whole planet, a certain national debt is around 14.6 trillion dollars… but 30 quadrillion?

If we put some of these units to use we can get a better grasp of their magnitude. Let’s take a simple relationship our Earth and our star, the Sun. The easiest unit to place is an AU, which is one (1) astronomical unit. Well, that may not help too much, so let’s take the Sun, the Earth, and that 1 AU between us and shrink them down. If we shrunk our Earth down to a single grain of sand, the Sun would be almost the size of a DVD disc, and that 1 AU would only be 12.84 yds (about 6.5 people from head to toe.

And how about a Parsec? Well, 1 Parsec is 3.26156 light-year is 3.0857×10^13 km. The nearest star to ours is Proxima Centauri, 4.3 light-years away. Given our micro-scale universe it would be 1983.798 miles away. So you can place your DVD at city hall in Phoenix, AZ and you can put Proxima Centauri on capital hill in Washington, D.C.

State-of-the-art supercomputer models show that merging neutron stars can power a short gamma-ray burst.

Dr. Neil deGrasse Tyson

If you are going to be in Houston this coming week, the University of Houston is having their Rockwell Lecture 2011, and Dr. Neil deGrasse Tyson will be there speaking about our past, present, and future in regards to space.

For more information: http://uh.edu/news-events/calendars/special-events/rockwell-lecture/index

But the Tuesday before that the Houston Museum of Natural Science well be having a TweepUp celebrating Dr. Tyson’s lecture the following day.

For info on that event: http://www.facebook.com/event.php?eid=192768090761913