In reply to:
[color:"blue"]Because of the speed involved, no will see the rapture happen, I assume. Perhaps, that is what the authors means by secret. (?)

No matter HOW FAST it happens people are going to see it and hear it. Do not faster sounds make sonic booms?

1 Thes 4:16-18 For the Lord Himself will descend from heaven with a shout, with the voice of the archangel and with the trumpet of God, and the dead in Christ will rise first. Then we who are alive and remain will be caught up together with them in the clouds to meet the Lord in the air, and so we shall always be with the Lord.
The scriptures do teach, of course, that Christ will return “as a thief in the night.” This means that the TIME of his coming is unknown.

Jesus likened his Second Coming to the destruction of the flood in the days of Noah. “But as the days of Noe were, so shall also the coming of the Son of man be. For as in the days that were before the flood they were eating and drinking, marrying and giving in marriage . . . and knew not until the flood came, and took them all away [or, as Luke’s account says, “destroyed them all” — Lk. 17:27]. SO shall also the coming of the Son of man be. Then shall two be in the field; the one shall be taken and the other left. Two women shall be grinding at the mill; the one shall be taken, and the other left. Watch therefore, for ye know not what hour your Lord doth come” (Mt. 24:37-42).

When the flood came, Noah was spared and the unbelievers were destroyed. That destruction produced a great separation. So shall it be at the Second Coming of Christ. Christians will be caught up to meet Christ; unbelievers will be destroyed.

Though the “world” was formerly destroyed by water, Peter points out that the destruction the world now faces will be by fire. “The world that then was, being overflowed with water, perished: but the heavens and the earth, which are now, by the same word are kept in store, reserved unto fire” (2 Peter 3:6, 7).

The article Pilgrim has all this and much more that puts Dispensational philosophy to rest--eternally The Rapture

Reformed and Always Reforming,