### Estimating the radius of the Moon - The medieval way

Having estimated the radius of Earth, the next step, celestially speaking, would be to estimate the radius of the Moon, our satellite and closest neighbor. And before we proceed any further, let me just point out the fact that the distances or sizes in astronomy are measured in angles and not in meters. From Earth, it looks to us as though the astronomical objects are moving on a celestial sphere and therefore, their motion can be quantified in terms of angular motion and sizes in angles. How to measure these angles you say? Well using a telescope of course! A telescope can be calibrated such that one can move it along or perpendicular to the horizon with milli-degree accuracy, helping us therefore to estimate the angular size of objects in the sky.

Now that we've cleared that, let's look at quantities in the Earth-Moon-Sun system that can actually be measured. We already know the radius of Earth. We can estimate the angular diameter of the Moon, and therefore of the Sun, using telescopes. It is measured to be 31 arcminutes or approximately half a degree. Why is the angular size of the Moon equal to the angular size of the Sun you ask? Hint : Eclipses!

Coming to point, using the small angle approximation, we can say that the ratio of angular size of the Moon and the angular size of the Earth's shadow at a distance equal to the distance between the Earth and the Moon is equal to the ratio of the actual diameter of the moon to the actual diameter of the Earth's shadow at that distance!

And to put a cherry on top of everything, now that we know the radius of the Moon and it's angular size, we can measure the distance to the Moon! Voila, now we know the radius of the Earth, the radius of the Moon and the distance between the Earth and the Moon!

You can also refer to this page, which gives a halfhearted explanation as to how to measure the same.

### Animation using GNUPlot

Animation using GNUPlotI've been trying to create an animation depicting a quasar spectrum moving across the 5 SDSS pass bands with respect to redshift. It is important to visualise what emission lines are moving in and out of bands to be able to understand the color-redshift plots and the changes in it.
I've tried doing this using the animate function in matplotlib, python but i wasn't able to make it work - meaning i worked on it for a couple of days and then i gave up, not having found solutions for my problems on the internet.
And then i came across this site, where the gunn-peterson trough and the lyman alpha forest have been depicted - in a beautiful manner. And this got me interested in using js and d3 to do the animations and make it dynamic - using sliders etc.
In the meanwhile, i thought i'd look up and see if there was a way to create animations in gnuplot and whoopdedoo, what do i find but nirvana!

In the image, you see 5 static curves and one dynam…

### on MOOCs.

For those of you who don't know, MOOC stands for Massively Open Online Course.

The internet is an awesome thing. It's making education free for all. Well, mostly free. But it's surprising at the width and depth of courses being offered online. And it looks like they are also having an impact on students, especially those from universities that are not top ranked. Students in all parts of the world can now get a first class education experience, thanks to courses offered by Stanford, MIT, Caltech, etc.

I'm talking about MOOCs because one of my new year resolutions is to take online courses, atleast 2 per semester (6 months). And I've chosen the following two courses on edX - Analyzing Big Data with Microsoft R Server and Data Science Essentials for now. I looked at courses on Coursera but I couldn't find any which was worthy and free. There are a lot more MOOC providers out there but let's start here. And I feel like the two courses are relevant to where I …

### On programmers.

I just watched this brilliant keynote today. It's a commentary on Programmers and the software development industry/ecosystem as a whole.

I am not going to give you a tl;dr version of the talk because it is a talk that I believe everyone should watch, that everyone should learn from. Instead, I am going to give my own parallel-ish views on programmers and programming.
As pointed out in the talk, there are mythical creatures in the software development industry who are revered as gods. Guido Van Rossum, the creator of Python, was given the title Benevolent Dictator For Life (BDFL). People flock around the creators of popular languages or libraries. They are god-like to most programmers and are treated like gods. By which, I mean to say, we assume they don't have flaws. That they are infallible. That they are perfect.
And alongside this belief in the infallibility of these Gods, we believe that they were born programmers. That programming is something that people are born wit…