A mirage? It’s the Isle of Man
QUESTION
Is it possible to see the Isle of Man from Blackpool? The Isle of Man sits in the Irish Sea, 60 miles from Blackpool. The tallest hill on the island is Snaefell, which is 2,037ft above sea level, but 65 miles from Blackpool.
The distance to the horizon from an observer close to the earth’s surface, in miles, is about 1.22 times the square root of the observer’s height.
Standing on Blackpool beach, assuming an eye level of 5ft 7in, the curvature of the earth would restrict an observer’s vision to a distance of just 2.9 miles.
Conversely, a person on top of Snaefell Peak might see 1.22 x√ 2,037 miles = 55.062 miles. Add the two together and you get 58 miles — so you wouldn’t be able to see Snaefell from the beach.
From the top of Blackpool Tower, however, things are very different.
The Blackpool eye near the top of the tower is 486ft high, so an observer might see 1.22x√486 miles = 26.9 miles. Add this to the Snaefell figure and you get 82 miles, so although you can’t see the whole island, you can see any part of it above about 1,500ft.
There is also an optical phenomenon which means that the entire island can occasionally be seen.
A ‘superior mirage’ occurs when the air below the line of sight is colder than the air above it. Passi ng through the temperature inversion, light rays are bent down, so the image of an object appears above the true object. Superior mirages are less common than the type we normally see on hot days, but when they do occur, they tend to be more stable, as cold air has no tendency to move up and warm air no tendency to move down.
So under the right conditions, usually at sunset, you can see a clear image of the Isle of Man from Blackpool beach.
Colin John, Preston, Lancs.
QUESTION
Did former U.S. President Herbert Hoover really give everything he earned to charity? Further to the earlier answer, hoover wasn’t the only u.S. President to give his salary to charity.
John F. Kennedy was born into wealth and married into it: his father was one of the richest men in America and his wife was an oil heiress.
JFK had a substantial income from the trust (estimated at $1 billion) he shared with other family members, and so donated his salary to charity.
his $100,000 wage was divided, after taxes, among 24 charities, including the Boy Scouts and Girl Scouts of America, the united Negro College Fund and the Federation of Jewish Philanthropies.
Don Croft, Leicester.