What must be the angle of incidence for total internal reflection to occur? Let medium 1 be the medium with the higher index of refraction. As θ1 increases, θ2 also increases, albeit at a faster rate. When θ2 reaches 90 degrees, there is total internal reflection, and there is no transmission of light. The corresponding angle of incidence, θ1, is the critical angle where total internal reflection occurs. Let the critical angle be θc. Substituting into Snell’s law:
The Astronomer Royal, of England, George B. Airy, in his celebrated work on Astronomy, the "Ipswich Lectures," says - "Jupiter is a large planet that turns on his axis, and why do not we turn?" Of course, the common sense reply is: Because the Earth is not a planet! When, therefore, an astronomer royal puts words into our mouth wherewith we may overthrow the supposed planetary nature of the Earth, we have not far to go to pick up a proof that Earth is not a globe.
24) If Earth and its atmosphere were constantly spinning eastwards over 1000mph then North/South facing cannons should establish a control while East-firing cannonballs should fall significantly farther than all others while West-firing cannonballs should fall significantly closer. In actual fact, however, regardless of which direction cannons are fired, the distance covered is always the same.
50.) We read in the inspired book, or collection of books, called THE BIBLE, nothing at all about the Earth being a globe or a planet, from beginning to end, but hundreds of allusions there are in its pages which could not be made if the Earth were a globe, and which are, therefore, said by the astronomer to be absurd and contrary to what he knows to be true! This is the groundwork of modern infidelity. But, since every one of many, many allusions to the Earth and the heavenly bodies in the Scriptures can be demonstrated to be absolutely true to nature, and we read of the Earth being "stretched out" "above the waters," as "standing in the water and out of the water," of its being "established that it cannot be moved," we have a store from which to take all the proofs we need, but we will just put down one proof – the Scriptural proof – that Earth is not a globe.

25.) The surveyor's plans in relation to the laying of the first Atlantic Telegraph cable, show that in 1665 miles – from Valentia, Ireland, to St . John's, Newfoundland – the surface of the Atlantic Ocean is a LEVEL surface – not the astronomers' "level," either! The authoritative drawings, published at the time, are a standing evidence of the fact, and form a practical proof that Earth is not a globe.