Figuring out the answer involved a prism, a pail of water, and a 50 year effort by the most famous father-son astronomer duo ever.
When it comes to planet Earth, the most important source of light, heat, and energy actually comes from beyond our world. It’s the Sun that is the driver of the Earth’s energy balance, rather than the internal heat given off by the planet itself from sources like gravitational contraction and radioactive decays. The energy from the Sun keeps temperatures from freezing all across the planet, providing us with temperatures that allow liquid water on Earth’s surface, and that are essential to the life processes of nearly every organism extant on our world today.
And yet, it’s only within the last 200 years that humanity has even understood how much energy, overall, the Sun actually produces. Considering all of the scientific advances that came afterwards, including the development of stellar, quantum, and nuclear physics, as well as the understanding of the subatomic fusion reactions that power the Sun, it might seem like a trivial matter to simply answer the question of “how much energy does the Sun produce?” But looks can be deceiving. If you didn’t already know (or hadn’t already googled) the answer to that question, how would you figure it out? Here’s how humanity did it.
The Solar System is not enough
You might think to yourself that simply knowing a few physical properties about the Sun, such as:
- how big it is,
- how massive it is,
- and how far away from Earth it is,
would go a long way towards delivering the answer to such a question. After all, you can see, with even extremely primitive tools (like your naked eye and a sextant), you can determine how large, in terms of angular size, the Sun is. Since ancient times, it’s been known that the Sun is approximately half-a-degree across from end-to-end, with more modern measurements confirming that its angular size varies from 31.46 to 32.53 arcminutes over the course of a year. (Where 60 arcminutes equates to one degree.)
