Top Five Ways of Observing the Heavens Throughout History
Today’s post is a blog post/philosophy essay, which explains the psuedo-citations after each of my regular in-line links. We’ll see what my professor thinks of getting a top five list on Monday.
Throughout history, mankind has been fascinated with the stars and planets. I’ve come up with a list of five of the most important tools that have been used to observe the sky, showing the improvement of our methods over time.
5. The Eye
Time of common use: Whenever we noticed the sky - Present
Approx. cost: Free
Ever since people noticed that the sky is full of sparkly dots at night, we’ve used our eyes to observe the skies. The earliest models of the heavens reflected the simplest interpretation of the sky — a huge sphere covered in tiny lights that rotates around Earth once per day.
The observation that all of the stars seemed to circle around Polaris, the north star, was very useful in navigation. The height of Polaris in the sky could be used to accurately determine altitude. If a sailor knew how high Polaris should be at their home port, they could find there way back by sailing north or south until the star was at the right inclination, then sail east or west to get home. The desire for more accurate inclination readings led to the development of the next device on our list.
4. The Sextant
Time of common use: 1450 - 1950
Approx. cost: $150
The sextant is actually the most modern of a long line of improvements of a simple idea. It is basically a device designed to measure the altitude of a star, which when used on Polaris will give an accurate measurement of latitude. The first iteration of the idea to gain popular use in the west was the quadrant. Although the quadrant was in use before 1450, it was not until then that it became commonly used. The quadrant has two holes through which the target star is sighted. A weighted line falls along a scale to allow readings of altitude.
Mariner’s Quadrant
By lining the two sights on the quadrant up with the target, the weight falls to an angle equal to the angle between the star and the horizon.
The sextant is much more complicated, but there is a nice summary on Wikipedia. [1] The sextant allowed not only for the measurement of a star’s altitude, but also the angle between stars.
For a more detailed history of the sextant, check out the page cited below. [2]
3. Galilean Telescope
Time of common use: 1600 - Present
Approx. cost: $13
The invention of the refracting telescope is often attributed to Galileo, although it was independently developed by others at around the same time. His telescope worked by using a pair of lenses to refract the light entering the telescope into a smaller, and still focused viewing point.
The Refracting Telescope
An image entering the left is focused to a smaller area on the right.
Although this design has several problems scaling to larger telescopes, it is still commonly used in things such as binoculars today. Galileo’s telescope had a magnification of about 20-30x [2], which can now be achieved by a $13 toy spyglass [3].
2. Brahe’s Observatories
Time of use: 1570s - 1601
Approx. cost: Impressing the king of Denmark
Tycho Brahe was a very important astronomer in the lath 16th century. He had a prosthetic nose, a pet moose (which unfortunately died after getting drunk and falling down the stairs at a nobleman’s house), and a few impressive observatories. Although none of his instruments used new ideas, he did build them on enormous scales, allowing him to take incredibly accurate measurements of the sky.
One of Brahe’s observatories is shown on the left, and a very large variation of a quadrant is on the right.
Image credits: [5][6]
1. The Hubble Space Telescope
Time of use: 1990 - Present
Approx. cost: $5,000,000,000
Because the Hubble Space Telescope is in orbit, it doesn’t suffer from interference caused by looking through the atmosphere. The design is a very advanced reflecting telescope, so it uses curved mirrors instead of lenses to focus the image. The telescope has been used to make countless observations to help our understanding of the cosmos. It magnifies light well enough that it has taken images of galaxies 12 billion light years away. [7] That means that the light the telescope gathered to take the image left the source galaxy 12 billion years ago. The universe is about 13.7 billion years old, and Earth is only 4.3 billion years old. This ability to look at galaxies so far away and so far back in time has allowed us to gain a much better understanding of the formation of the universe as we see it today. Some of the telescope’s most famous images can be found at the site below. [8]
1. Sextant http://en.wikipedia.org/wiki/Sextant
2. Evolution of the Sextant http://home.earthlink.net/~nbrass1/cardart.htm
3. The Galileo Project - The Telescope http://galileo.rice.edu/sci/instruments/telescope.html
4. Handheld Explorer Telescope, 30x http://www.hometrainingtools.com/catalog/physical-science-physics/light-optics/p_as-telexpl.html
5. Tycho Brahe’s Uraniborg http://en.wikipedia.org/wiki/Image:Uraniborgskiss_90.jpg
6. Tycho Brahe’s Mauerquadrant http://en.wikipedia.org/wiki/Image:Mauerquadrant.jpg
7. Main Hubble Page http://hubble.nasa.gov/index.php
8. Hubble’s Highlights http://hubble.nasa.gov/overview/science-highlights.php
