I said that it is theoretically possible to work out the optimal neck length for coffee at a given temperature, so the warmth of the coffee is acceptable to the Giraffe. To take it further, for a specific Giraffe, whose neck length is known, you can work out the acceptable coffee temperature at the point of entry ( its mouth). And mentioned to my friend that she can ask this question to the site xkcd.com. The person who runs the site actually has a section that answers hypothetical question in a serious scientific manner.
When Randall Munroe, who runs xkcd.com and answers hypothetical questions at http://what-if.xkcd.com/, comes out with a book of such questions, with more than 50% totally new, it does need a special mention.
So, just to re-iterate, 'What if ' is a book that provides serious scientific answers to absurd hypothetical questions. the questions, to quote a few examples like 'what will happen if the sun suddenly goes off ? ' or 'how high can you throw a ball'.
If you are the curious type who wondered during college whether it makes more sense to get coffee cold because you get more coffee, work it out :) , then this is your kind of book.
If you have kids who are really curious about what is happening around and ask all kind of questions, i would suggest you get a copy of this book and gift it to them. The kid should know a little bit of physics, mathematics and some basic geography to appreciate this book. And it helps if there are adults around to answer more queries.
But be warned, this is not one of those books that you can finish in one sitting. You read a question and it's response. Take some time to understand and appreciate it and then come back for later. Trying to finish it in one sitting would be akin to gulping down gourmet food.
I would strongly recommend buying a few copies of the book and gifting it to schools or interested curious kids. I did :)