Atmospheric pressure decreases as altitude increases. A pressure difference can occur without a barrier. Other factors, like gravity, can cause a pressure difference.
Flat-Earthers claim a pressure difference cannot possibly occur without a barrier, like Earth’s atmosphere next to the vacuum of space. In reality, it is not difficult to demonstrate that a pressure difference can exist without a barrier.
Many smartphones and smartwatches are equipped with a pressure sensor that we can use to measure the pressure difference. These devices can easily measure the pressure difference between upstairs and downstairs in a two-story house. Some can even tell the pressure difference when we put it on a table and the floor. There is no barrier involved, yet there is a pressure difference, proving that a pressure difference can exist without a barrier.
The pressure gradient of Earth’s atmosphere is well known. We use it to measure altitude. Our smartphones & smartwatches use it to measure our vertical movements for health monitoring purposes.
References
- Atmospheric pressure – Wikipedia