what is the fifth planet from the sun?
author: Swaraj Dash, Daan van de Weem and Will Earley
Note: the original puzzle used http://tinyurl.com/ph2k16-, but was necessarily hardcoded for the live puzzlehunt. The archived puzzle then used http://tinyurl.com/phar2k16- for a time (being otherwise identical in function), until the (concealed) secondary link service went down completely (damn linkrot!). As a result, the entire url redirection part has been locally internalised to avoid any further collapse of external entities.
The title of this puzzle is a URL,
tinyurl.com/ph2k16-, and refers to a link-shortening service, TinyURL. However the URL appears incomplete and (should) 404 if we attempt to navigate to it.
Looking to the puzzle body suggests how to complete it. Answering the simple question, we are prompted to navigate to tinyurl.com/ph2k16-jupiter, whereupon we find a new question. In order, we must answer the following questions:
what is the fifth planet from the sun? jupiter what is the major constituent of the atmosphere? nitrogen what city is the eiffel tower in? paris what colour is grass? green what is the best university in the world? cambridge (duh) what is the answer to the ultimate question of life, the universe and everything? 42
When we answer the final question, we are taken to a page that simply says 'congratulations!', but we are not done! Taking a clue from the title, redirection must play an active role in this puzzle, as tinyurl by definition involves redirects. If we pay slightly more attention, we may notice that the last links take a little longer to load. If we inspect the redirects, e.g. with wget or a redirection analysis tool, we find that there are in fact chains of redirects, amusingly via the site www.www.reallyhugeurl.com (this was necessary as tinyurl forbids nested redirects to itself or other commonly known link shortening services - this service is now down, see the notice at the top of this solution, and has been replaced by an internal service...).
If we count the total number of redirects (including the initial tinyurl), we get [2,1,3,4,7,11]. Searching Google, or perhaps recognising the series, we find that these are the first six terms of the Lucas numbers (a variant of the Fibonacci numbers), and so the answer is