Your stacked magnets aren’t just a fine demonstration of magnetic levitation, they also serve as a model for Earth’s atmosphere—especially in the spacing between the magnets.
The gaps between the magnets are visible evidence of the forces at work here. The magnetic force of the bottom magnet has to hold up the weight of four magnets overhead, so the gap between the bottom two magnets is small. Near the top of the stack, the fourth magnet only needs to hold up one overlying magnet, so the gap between them is wide.
In the atmosphere, the pushback against gravity comes from air pressure, not magnetism, but the result is much the same: The spacing between air molecules increases with altitude, so the density and pressure of the air are higher below, lower above.
Air is compressible, which means it behaves a lot like a spring. Near the surface of the earth, air is squashed by the weight of the air above. The result is relatively high density and pressure. As you rise higher and higher in the atmosphere, there’s less overlying air to support, so pressure and density decrease.
You’ve probably experienced this change in air pressure and density personally—while traveling, for example, when your ears “pop” in an airplane, or when an unopened bag of potato chips explodes as you drive over a mountain pass.
At the summit of Mt. Kilimanjaro (18,000 feet, or 5.6 km above sea level) you’re above half the earth’s atmosphere. In other words, the atmospheric pressure and density there is half that at sea level.