As an extragalactic astronomer, I’ve lost track of the number of times I’ve needed a cosmological calculator. Usually I use the routines built into (or that I’ve written for) the analysis packages I use. Obviously those are best for large calculations; for a more casual query with just a few redshifts, online web-based calculators are faster.
My hack day proposal was to create the Super Soaker of cosmology calculators. Specifically, I suggested that we adapt Ned’s calculator to take a list of redshifts and package it as a Dashboard widget for OS X.
You can enter multiple redshifts and (one or) multiple cosmologies. Just enter/paste the values into the boxes, and press “Go”. The result comes up as a table in the widget:
(If you’ve entered multiple cosmologies, they will appear as columns in the table too.)
You can then click to copy the table to your clipboard in tab-delimited form, for easy pasting into the document/application of your choice. The units are as shown (and are the same as Ned’s original calculator, though we’ve dropped the explicit conversion to light-years for each column). If you input a big enough list, the table becomes scrollable. Even though it is not optimized for large datasets, I tried it with a list of 1,000 redshifts and it only took a second or so to compute. So I’m not suggesting it become your main cosmology-calculator workhorse, but it will do in a pinch.
The widget is available for download at http://tinyurl.com/cosmocalc-widget as a .zip file. In OS X, just double-click to install after you’ve uncompressed it. Users of other platforms may not be able to install this as a widget, but you can still download it, open the folder and load the webpage therein.
A final note: I had spoken to Ned about this months before .Astro and was re-granted his blessing via e-mail once the hack was finished, so all is well concerning copyright/use issues. If you do use the widget in preparation of a paper, please cite him.