Humans once thought the Sun was cold.
Leonardo da Vinci was one of the world’s most renowned figures for his discoveries not only in science but also in art . He would often say: ’Men and animals are in reality vehicles and conduits of food, tombs of animals, hostiles of death, coverings that consume, deriving life by the death of others’ — strange right. He also proved that the sun must indeed be hot; to put it simply, in the past — many great minds including Aristotle reasoned that this giant object hanging in the sky couldn’t possibly be hot because “why isn’t it the color of fire?”, “what is its fuel source and why does it not run out?”- from these questions they concluded that the sun must be cold.
Aristotle theorized that the terrestrial world is made of four basic elements: fire, air, water, and earth. All arranged in order of increasing density whereby the densest ones are down at the bottom, in perspective: we’ve got a layer of earth, water, then comes air, and above all that air there must be a sphere of unignited elemental fire. This then created a perfect problem: “what’s outer space made out of?”, “what is the moon, the sun and the stars made out of?” ; and his rather genius answer to that was that they were made of something that must probably be less dense than fire, since they’re so high up, and he called it quintessence or aether.
Get Kaizzi Elijah’s stories in your inbox
Join Medium for free to get updates from this writer.
Aether was neither hot nor cold, meaning there was no way the sun was generating heat in itself because it was made of aether. He then reasoned that the sun therefore rubbed against the fire sphere and the air sphere to produce frictional heat that we then felt coming from its direction — this reasoning was so sound that many great minds believed this to be true for a time.
Leonardo however drew a conclusion on something people already knew about the sun, he experimented and found that if you took a concave mirror and you focused the sun’s light to a point, light would concentrate on that point and also heat would form. This realigned his reasoning that : ‘Heat must be an intrinsic property of the rays that come from the sun and the sun itself, not the result of the sun rubbing on the atmosphere’. He also stated that : ‘They say that the sun is not hot because it’s not the colour of fire , but the answer to this is that when molten bronze is hottest, it resembles the colour of the sun, and when it is less hot, it has the colour of fire’. This simple observation completely reversed the common notion on the state of the sun, from being a cold body made of aether to a hot terrestrial body, not made of aether.
Leonardo was indeed right about the sun being hot but the question of where the heat comes from would remain unanswered for more than four centuries. Great minds like Kelvin and Helmholtz proposed that the sun was slowly shrinking and heating itself through gravity but this idea did not account for its billions of years of age . It was only later in the 20th Century that Arhtur Eddington suggested that the sun might be powered by fusion and Hans Bethe worked out the details in the late 1930s showing that hydrogen nuclie are fusing into helium deep in its core.
What I find most striking is how reasonable the “cold Sun” idea was. It rested on careful logic and the best understanding of its day. What overturned it wasn’t a telescope or a laboratory but a curved mirror and an observer who noticed that molten bronze changes colour as it cools. “Being wrong isn’t the same as being foolish”, sometimes it takes one simple observation, looked at honestly, to change what everyone thought they knew.
