Week 2: Astrophysics in a Nutshell Chapter 1

Chapter 1 of Astrophysics in a Nutshell essentially focused on how telescopes worked, but the most interesting part for me was the parallels drawn between telescopes and the human eye (again, I'm much more a biologist than a physicist). Like telescopes, the human eye has a both a "camera" and a "detector"--the lens in the front of the eye focuses the light onto the retina in the back of the eye in the same way telescopes may use mirrors to focus light onto a CCD or other type of detector.

Many vision problems arise from misalignments of the focused light in the eye, and for centuries, concave and convex lenses have been used as vision correctors. On top of that, people have been staring at the sky for pretty much as long as people have been around to look at anything. It's not surprising, then, that in some ways the human eye served as inspiration for telescopes, and that the first telescopes used lenses to magnify the light.

The lens focuses light onto the retina, although the image is flipped--a problem which is corrected by the brain. 

However, telescopes soon surpassed eyes in almost every regard (which would be sad if it weren't kind of the point of telescopes in the first place). First of all, modern telescopes can increase their integration time. This allows for the detection of a larger number of photons, which strengthens the signal of faint sources. Our eye has a very short, fixed integration time of only a fraction of a second, which isn't conducive to astronomy, but also prevents us from being blinded by the Sun, so it's probably a net positive. Our eyes are also pretty small, which again isn't conducive to gathering tons of photons. If you've ever had your eyes dilated, that increases the pupil size, allowing more photons to enter. This is why the ophthalmologist's office always gives you those super cheap sunglasses after every appointment. 

Swag.

You never see telescopes wearing those cool glasses though, because it's to an astronomer's advantage to gather as many photons as possible, and this is facilitated by having a larger area over which to gather photons. Finally, the eye is limited in that it can only detect electromagnetic radiation in the visible spectrum (hence the name "visible spectrum"). Telescopes, on the other hand, can be set to detect wavelengths in different parts of the spectrum. This is helpful since a lot of astronomy occurs outside of the visible light range, so we'd never be able to be able to detect all that information without them, even if our eyes were otherwise comparable to telescopes. 

One interesting thing to think about is whether there are alternative forms that telescopes could take that are less based on the human eye, and what the advantages and disadvantages of something like that would be. 

Sources
https://en.wikipedia.org/wiki/History_of_the_telescope
http://www.antiquetelescopes.org/history.html
https://cnx.org/resources/465ef69789306dc609b2650a92697be3e852a6e7/Figure_27_01_02.jpg
http://www.easyeyes.com/images/pedsc.jpg