The causes of the Change are subject to much speculation among the characters of the Emberverse universe, with a large range of theories relating to it. Popular amongst the Christian, Wiccan and other religious communities is the idea that the Change was a divine act by God, the Æsir, or the Lord and Lady, whether for punishment or to protect humanity from themselves. Another theory is that the effect was caused by an alien intelligence in an effort to minimize the ability of a competing civilization to wage war in their universe, or some other unknown purpose. These aliens apparently have the ability to affect matter and energy at the quantum level. This theory was referred by Ken Larsson, who referred to the alien intelligence as “Alien Space Bats”. A smaller, less popular theory holds that the Change was a completely natural occurrence. There is no evidence that the Change is reversible.
It’s theorized by characters that ASBs did it: