As we celebrate IYA and Galileo's use of the astronomical telescope, it's time for some clarification. Galileo was not the first person to use a telescope. He wasn't even the first person to use a telescope for astronomical purposes. That honor goes to Thomas Harriot, an English astronomer who drew maps of the moon several months before Galileo. In fact, his very detailed diagrams were some of the best of the period. Unfortunately, he never published those maps or anything else related to his astronomical observations. He was well off and didn't need the income; it seems he pursued astronomy as a hobby and was content to keep his drawings to himself.
So as we honor Galileo for his discoveries and contributions, let's give a shout out to Thomas Harriot, who proved that if you don't publish, you just may perish (historically speaking). To hear more, you can check out this podcast from 365 Days of Astronomy, although it's a bit dry.
Thanks for joining me for this three part series. Check back next week for information on how and where you can see Venus!
Showing posts with label telescopes. Show all posts
Showing posts with label telescopes. Show all posts
Friday, January 23, 2009
Thursday, January 22, 2009
What Good Is a Telescope? Part 2
Yesterday we left off with the geocentric view of our universe (with Earth at the center and everything else orbiting it), as propounded by The Church. Since this model could help predict the future positions of the planets, this meant power.
But of course, this couldn't last forever; absolute power and all that. The guy who changed everything forever was Galileo, and he did it with a telescope.
Galileo was an Italian scientist who became a student of Copernicanism upon reading works of Nicolaus Copernicus, an astronomer who died 21 years before Galileo was born. Copernicus maintained that the sun, not the earth, was the center of the universe (I'm using the term 'universe' as it would have been described at that time, not in our time). This model explained retrograde motion more clearly and simply that the geocentric model did, and thus provided more accurate predictions.
In the early 17th century, Galileo heard of a device called a spyglass and adapted a similar device to study the heavens. It was a simple device, a tube with a concave lens at one end and a convex lens at the other. It wasn't like a telescope you would use today; in fact, its power and quality were probably a bit less than a decent pair of binoculars today. To his credit, Galileo made vast improvements in the design of telescopes, eventually grinding his own mirrors and thereby drastically bettering his view of the universe.
Once he applied this new technology to the study of the stars, Galileo stumbled upon a cosmic quandry that would resolve the geocentric/heliocentric debate: the phases of Venus. If the geocentric view were to be correct, Galileo would never see Venus as more than a crescent in his telescope; if the heliocentric view were correct, Venus would grow from crescent to nearly full as viewed from the earth. Below are two animations demonstrating what each of these models would look like respectively.
Ptolemy's Model
Copernicus' Model
You guessed it; as Galileo studied Venus' phases through his telescope, he saw not just a crescent Venus but as time passed, all the way to a gibbous Venus in his field of view. And as quick as that, thousands of years worth of cosmological thinking were made obsolete.
You probably know the rest of the story. I won't go into details, but The Church wasn't particularly gracious about this new information (remember, astronomical knowledge = power); nor was Galileo gracious in his response. Nonetheless, the Scientific Revolution had begun and our understanding of the universe changed forever.
One last note: if you would like to listen to a fascinating account of all this, I highly recommend you give my fellow former planetarian Davin Flateau a listen. His podcast (part 365 Days of Astronomy podcast series) is available here. It's definitely worth nine minutes of your time. And the theme song is awesome!
Check back tomorrow for the exciting conclusion of our telescope tale.
But of course, this couldn't last forever; absolute power and all that. The guy who changed everything forever was Galileo, and he did it with a telescope.
Galileo was an Italian scientist who became a student of Copernicanism upon reading works of Nicolaus Copernicus, an astronomer who died 21 years before Galileo was born. Copernicus maintained that the sun, not the earth, was the center of the universe (I'm using the term 'universe' as it would have been described at that time, not in our time). This model explained retrograde motion more clearly and simply that the geocentric model did, and thus provided more accurate predictions.
In the early 17th century, Galileo heard of a device called a spyglass and adapted a similar device to study the heavens. It was a simple device, a tube with a concave lens at one end and a convex lens at the other. It wasn't like a telescope you would use today; in fact, its power and quality were probably a bit less than a decent pair of binoculars today. To his credit, Galileo made vast improvements in the design of telescopes, eventually grinding his own mirrors and thereby drastically bettering his view of the universe.
Once he applied this new technology to the study of the stars, Galileo stumbled upon a cosmic quandry that would resolve the geocentric/heliocentric debate: the phases of Venus. If the geocentric view were to be correct, Galileo would never see Venus as more than a crescent in his telescope; if the heliocentric view were correct, Venus would grow from crescent to nearly full as viewed from the earth. Below are two animations demonstrating what each of these models would look like respectively.
Ptolemy's Model
Copernicus' Model
You guessed it; as Galileo studied Venus' phases through his telescope, he saw not just a crescent Venus but as time passed, all the way to a gibbous Venus in his field of view. And as quick as that, thousands of years worth of cosmological thinking were made obsolete.
You probably know the rest of the story. I won't go into details, but The Church wasn't particularly gracious about this new information (remember, astronomical knowledge = power); nor was Galileo gracious in his response. Nonetheless, the Scientific Revolution had begun and our understanding of the universe changed forever.
One last note: if you would like to listen to a fascinating account of all this, I highly recommend you give my fellow former planetarian Davin Flateau a listen. His podcast (part 365 Days of Astronomy podcast series) is available here. It's definitely worth nine minutes of your time. And the theme song is awesome!
Check back tomorrow for the exciting conclusion of our telescope tale.
Wednesday, January 21, 2009
What Good Is a Telescope?
This month's IYA theme is telescopes. In fact, the reason this year is IYA is that 2009 marks the 400th anniversary of Galileo's first use of the astronomical telescope. So what? Why should you care?
I'm going to answer that question in three parts, each of which will go live in three consecutive days. So consider this the first part, but by no means the entire story. Check back for more tomorrow and the day after.
The first part of this story centers around the power of astronomy. The power of astronomy is the power to predict the future. That is to say, we all have enough astronomical knowledge to know that the sun will rise and set each day. We can plan around this and it gives us power. If we didn't have that knowledge, we wouldn't have the power to set our own schedules or even know when the best times to sleep or work would be. In earlier times, the power to predict the future was just as important. And that future was laid out in the stars. If you could know where the planet Venus would be 5 months in the future, that meant power. And if you predicted it incorrectly, that was even worse.
To understand the importance of telescopes, let's take a journey back in time to the early 17th century. At that time, the ruling view of the universe was the geocentric model articulated by Ptolemy and Aristotle before him. From this point of view, the sun, the moon, the planets, and the stars all orbited Earth in perfect spheres. This was the "onion" universe: the earth was at the center; the moon orbited in the sphere closest to the earth (like the layer of onion closest the center); Mercury and Venus orbited the earth just past the moon, each in their own layer; the sun was in the next layer out; followed by Mars; Jupiter; Saturn; and then the stars were the outside layer, all being part of one sphere that encircled all other spheres of orbit. In this model, the movement of celestial bodies was perfect and circular.
There was a bit of problem with this model; as all keen sky observers know, the planets don't follow a straight path in a single direction across the sky; occasionally, they seem to go backward in their path and then forward again, making a loop. How could this be explained in a model of spheres? The idea of epicycles sprung forth. Epicycles were orbits within orbits; that is to say, a planet like Mars would be moving in its own circular path while circling Earth.
This model of the universe was mostly accurate and allowed early astronomers to predict the positions of the planets más o menos (more or less, as we say in Spanish). Since the Catholic Church was one of the great powers of the day, The Church made sure that this perfect model was the one that people understood. God put Earth at the center of the universe (and by extension, man), and all other celestial bodies orbited in their perfect spheres. The Church could predict the future through this model of the universe and that gave The Church power.
Stay tuned for Part 2 of our telescope talk!
I'm going to answer that question in three parts, each of which will go live in three consecutive days. So consider this the first part, but by no means the entire story. Check back for more tomorrow and the day after.
The first part of this story centers around the power of astronomy. The power of astronomy is the power to predict the future. That is to say, we all have enough astronomical knowledge to know that the sun will rise and set each day. We can plan around this and it gives us power. If we didn't have that knowledge, we wouldn't have the power to set our own schedules or even know when the best times to sleep or work would be. In earlier times, the power to predict the future was just as important. And that future was laid out in the stars. If you could know where the planet Venus would be 5 months in the future, that meant power. And if you predicted it incorrectly, that was even worse.
To understand the importance of telescopes, let's take a journey back in time to the early 17th century. At that time, the ruling view of the universe was the geocentric model articulated by Ptolemy and Aristotle before him. From this point of view, the sun, the moon, the planets, and the stars all orbited Earth in perfect spheres. This was the "onion" universe: the earth was at the center; the moon orbited in the sphere closest to the earth (like the layer of onion closest the center); Mercury and Venus orbited the earth just past the moon, each in their own layer; the sun was in the next layer out; followed by Mars; Jupiter; Saturn; and then the stars were the outside layer, all being part of one sphere that encircled all other spheres of orbit. In this model, the movement of celestial bodies was perfect and circular.
There was a bit of problem with this model; as all keen sky observers know, the planets don't follow a straight path in a single direction across the sky; occasionally, they seem to go backward in their path and then forward again, making a loop. How could this be explained in a model of spheres? The idea of epicycles sprung forth. Epicycles were orbits within orbits; that is to say, a planet like Mars would be moving in its own circular path while circling Earth.
This model of the universe was mostly accurate and allowed early astronomers to predict the positions of the planets más o menos (more or less, as we say in Spanish). Since the Catholic Church was one of the great powers of the day, The Church made sure that this perfect model was the one that people understood. God put Earth at the center of the universe (and by extension, man), and all other celestial bodies orbited in their perfect spheres. The Church could predict the future through this model of the universe and that gave The Church power.Stay tuned for Part 2 of our telescope talk!
Subscribe to:
Posts (Atom)
Posts
