Dork Scratchings

 Photo taken in the Outer Hebrides by my brother-in-law (The doctor one, not the Flat Earth one) This photo was taken a few days ago by my brother-in-law Alex from the Outer Hebrides where he's off galavanting at the moment. You can clearly see that half the ship is missing indicating either a) it's sinking b) the Earth is round Going with (b) for the time being we can actually come up with a pretty good guesstimate for the size of the Earth just from this picture. Let's guess that the ship is 10km away. (That's not likely to be accurate but it's certainly more than 1km - the width of Lake Windermere - and less than 100km - the distance from Portsmouth to Le Havre). So $l=10000$. Now let's assume that the bottom 10m of the ship is missing from view (again, not likely to be accurate but good enough for an order of magnitude calculation). So $h=10$. Now chuck it into this equation which is easily worked out with a bit of trig $$ r=\frac{l^2}{2h} $$ and, hey presto

I got into a debate with a flat-earther the other day.  After a while I grew to respect the position.  After all, not taking anything on trust is a cornerstone of science.  I pointed out that I've verified the Round Earth theory personally, by creating a sundial that tells both the time and the date .  My sundial was created using a mathematical model that assumes Earth is spherical, spinning about it's axis, and orbiting the sun.  And I've tested it works.  (I also had a job writing code for transceivers that talk to satellites, so you could say I'm a fully signed up round-earther!) Unfortunately my argument did not convince because it required either That the flat-earther trusted me, or That he was willing and able to follow the maths behind the model This led to to wonder what's the simplest way to demonstrate the Earth is round?  It has to involve no maths, and be easy to reproduce by skeptics anywhere.  The video is my answer to that question. PS

A few years ago I got involved in a conversation with my brother in law who has, shall we say, conspiracy theorist leanings.  He was terribly upset whenever he looked up and saw what he described as "chemtrails" in the sky.  Apparently, the illuminati - or whoever - are controlling our thoughts by spraying mind altering chemicals from jumbo jets. The main argument he made was that they didn't look like what you would expect to come out of an engine. A few days later I was mulling over this while cycling to work.  What, I thought, should it look like?  I realized that it should be really easy to work out and by the time I arrived at work, I'd figured it all out, bar some missing constants that I then looked up.  I quickly knocked up an email which I then sent ... to myself.  Because responding to conspiracy theorists with arithmetic is like poking bears with sticks. I took special care when researching online not to use any search terms that refer to either c