What is the "strong delusion"?

In many of the world's major cities, there are cathedrals, some with spectacular domes. Historians say domes originally had a celestial significance, and were symbols of heaven or the firmament. The "strong delusion" that caused the Church to support the geocentric cosmology with a rigid heaven revolving around the earth was a result of the corruption of the Bible's cosmology in the 2nd century BC. These corruptions were intended to support the idea that heaven is a 'firmament', that revolves around an earth fixed and immobile at the center. Because the Bible's so-called 'primitive' cosmology was discredited by the scientific revolution, many people assume the gospel has been discredited also, and that is a "strong delusion", which may be the one foretold by Paul:

2 Thessalonians 2:11-12 (NIV)
For this reason God sends them a powerful delusion so that they will believe the lie and so that all will be condemned who have not believed the truth but have delighted in wickedness.

The pagan geocentric cosmology of the hellenistic age was introduced into the Bible in the 2nd century BC, and the fraud has led to the construction of domes, and their decoration as celestial symbols, with stars on a blue field symbolic of the sky, figures of saints clothed in blue, and symbols representing the celestial sphere. Even the cross had an astronomical significance in ancient Egypt. The domes and other related symbols are evidence of the influence of the pagan geocentric cosmology in the Church, that seemed to be supported by scripture, because of the corruptions that were incorporated in the Old Testament by Antiochus IV in the 2nd century BC.

Paul refers to the Church as the "house of God" and the "pillar and ground of truth".

1 Timothy 3:15
But if I tarry long, that thou mayest know how thou oughtest to behave thyself in the house of God, which is the church of the living God, the pillar and ground of the truth.

Because of the deception caused by the revision of the cosmology of the Bible by Antiochus IV, the "light" of the true gospel has been hidden from the world. The Church is supposed to be "clothed with the sun" (Revelation 12:1), but that sun has become dark! This is what prophecy of Revelation 12:6 says; the sun turns black as sackcloth made of hair! The sun here represents the light of the gospel, which adorns the Church, and does not refer to a literal darkening of the sun, which would result in an ice age. Jesus said his disciples are the "light of the world":

Matthew 5:14
Ye are the light of the world. A city that is set on an hill cannot be hid.

Those who built the great cathedrals and churches that feature elaborate domes were no doubt devout, sincere, and pious believers, but they erected impressive, enduring monuments to the cosmological and scientific ignorance of the age in which they lived. The Church has been deluded about cosmology for much of its history, because of the fraud of Antiochus IV. The geocentric cosmology of the ancient Greeks was esteemed for centuries, and because it seemed to be supported by the scriptures, it appeared to have divine authority. The Church, and the Bible were discredited when the old cosmology was overthrown. The fraud initiated by Antiochus IV is now exposed, by the prophecies of Daniel.