This story has been going round the Internet https://www.bbc.co.uk/news/uk-england-cornwall-56286719 It is an amazing image. A superior mirage diagram is here https://upload.wikimedia.org/wikipedia/commons/5/54/Superior_and_inferior_mirage.svg It looks like it happens in temperature inversion conditions and that light travels faster in warmer air than in colder air. This will be because warmer air is less dense. I shall now be more aware on days of temperature inversion in the hills. Having seen the Brocken Spectre last year, it would be great to see a floating object!
