We don’t say ‘The Air is Curved’ when we see a mirage!
Light Bends — Air Doesn’t. So Why Say Space Curves?
When you spot a mirage shimmering on a hot road, it’s easy to think that the air itself is bending or curving to produce that illusion. But that’s not what’s really happening — and the distinction matters, especially when we draw parallels to how we talk about gravity.
Mirages Aren’t Caused by Curved Air
On a hot day, the surface of a road heats the air just above it, creating layers of air at different temperatures. Hotter air is less dense than cooler air, and this change in density causes light to bend as it travels through the layers — a process known as refraction.
But here’s the key point: the air isn’t bending. The air is just doing what air does — varying in temperature and density. It’s the light that changes direction, because it’s passing through regions with different properties. We don’t say “the air is curved” — because it’s not.
Now Think About Gravity the Same Way
Just as we don’t say the air curves to explain a mirage, maybe we shouldn’t be so quick to say “space is curved” to explain gravity. What we observe are the paths objects take through space — paths that change depending on the structure of that space. But space itself, like air, might not be “bending.” It might just be behaving differently in different regions.
Just as we don’t say the air curves to explain a mirage, maybe we shouldn’t be so quick to say “space is curved” to explain gravity. What we observe are the paths objects take through space — paths that change depending on the structure of that space. But space itself, like air, might not be “bending.” It might just be behaving differently in different regions.
In fact, we can understand gravity not as the curvature of space, but as the differential expansion of space — that is, space expanding at different rates in different areas. Matter doesn’t curve space — it alters the rate at which space expands. And just like light bends when it encounters a gradient in air density, matter follows paths shaped by the gradient in the expansion of space.
The Importance of Clear Models
How we talk about phenomena shapes how we understand them. With mirages, it’s clearer and more accurate to describe how light behaves in response to changing air conditions — not how air somehow “curves.” The same clarity can be applied to gravity: focus on how matter behaves in response to changes in space, rather than imagining that space is literally warping like a rubber sheet.
In both cases, it’s not the medium that’s bending — it’s the path through the medium that’s changing.
Let’s describe what’s actually happening — not just what it looks like.