Arthur Eddington, Albert Einstein, the curved universe, just a mirage?

Question

In 1919 during a solar eclipse, Arthur Eddington observed the light from stars passing close to the sun was slightly bent, so that stars appeared slightly out of position, apparently confirming Einsteins theory and leading to the curved universe theory. Was Arthur not simply observing the bending of light rays due to the heat of the sun, the same effect that causes mirage's?

Answer 1

In a desert, the layer of air closer to the sand is hotter and less dense compared to the layers above. Thus the layers have different refractive indices and the light coming from a distant object (say, a real oasis) is bent towards the ground. This causes a mirage.
Firstly, there is no medium like air near the sun that can cause the bending of starlight by refraction.
Imagine, however, that a ray of starlight coming from the vacuum of space enters the photosphere, the sun's outermost envelope. Even though the photosphere consists of extremely rarefied gas, we may expect the ray to bend microscopically towards us on Earth.
However, the moment the ray re-emerges from the photosphere to continue its way towards Earth, it bends the opposite way. Thus, net bending of the ray is zero.
On the other hand, the actual bending of starlight observed during an eclipse matches the prediction of general relativity to a very high degree of approximation.
Isn't it logical to conclude then, that it's gravity and not heat that does the bending mischief ?

Answer 2

These measurements were made with sensitive (for its time) equipment that was not subject to mirages.