I needed a diagram for an article on noctilucent clouds. They range from pretty (and copyrighted) to pretty ugly online so I had a go at making my own. As usual this was done with LaTeX (via LyX) and PSTRICKS.
Here's the finished picture:
The diagram is simple: part of a circle, some tangent lines, cloud symbols and labels. Then shade between the various curves and lines. Finally, a multi-do loop to draw the Sun.
Details below the fold.
If the Earth suddenly stopped moving around the Sun - how long would it take to fall into the Sun?
First of all, this is a situation that will never, ever happen! It would take a phenomenal amount of energy to stop planet Earth in its tracks. A passing malevolent alien attack fleet imparting that much energy to the Earth would likely destroy it! (Another problem for another day :-p ) Nevertheless it's an interesting maths problem to think about (maybe only to me) on a lazy afternoon.
We can use conservation of energy to solve this. The Earth has kinetic energy (from its motion) and gravitational potential energy because of its position in the gravitational field of the Sun. Ignoring the effects of other planets, the sum of those energies is constant and we can use that fact to figure out the fall time. Click below if you want to avoid the maths and just to skip to the answer!
Just bought a new Microsoft Surface 3. The (happy happy) days when I had to install the operating system myself are gone but I still have to put the software on.
Given that the resources are limited to 128GB (for the moment) on the tablet itself I can only really install stuff I absolutely need. So, this is a list of stuff that I can't get by without. Geek alert!
Absolutely must install SkyTools 3 too to record my observations at the telescope. I have installation disks but no CD drive so it'll have to wait for now.
I could happily survive without Microsoft Office but everyone else seems to use it. So therefore I have to. An unhappy situation. Space is tight on the tablet so I won't be installing Open Office alongside it.
Dr Adrian Jannetta
Guitar strummin' explorer of the universe. Mild mannered maths teacher by day and astronomer by night.