The third heaven is the dome or firmament, which is a sea of glass. It's a rigid crystalline sphere on the edge of space which formed in response to the creation of gravity on the second day.
The Third Heaven
The Second Heaven
Most of the space between the firmament and Earth is the cosmos or observable universe. There's something very odd about the cosmos: there's a disconnect between what we can see vs. what we believe about it.
The First Heaven
Part of the space between the firmament and Earth is the area in contact with the Earth that we call the atmosphere, or sky. This is where the birds fly. It's referred to as the open firmament.
Absolute Frame of Reference
The universe has an absolute frame of reference and Earth is at the center. This is an empirical observation (verifiable by direct observation). In the Geocentrospheric model a spherical Earth is at the center of a spherical cosmos.
February 16th
The Apostle Paul refers to the third heaven in which case, logically, there must also be a first and second heaven. If you believe that Earth orbits a sun which is adrift in an infinite universe, you don't have a third heaven.
Relative Motion
There's no observable difference between heliocentric and Geocentrospheric models because they're two frames of reference in the same system. They coexist.