Famous British scientist James Joule had a profound passion for physics from a young age, often conducting his own experiments on electricity and heat. During one summer vacation, Joule went on a trip to the countryside with his brother. Even while playing, the curious and studious Joule never forgot to perform his physics experiments.
He found a lame horse and, with his brother leading it, hid behind to use a Voltaic pile to apply a current to the horse, hoping to observe how an animal would react to electrical stimulation. As expected, the horse jumped violently upon being shocked, nearly injuring his brother. Despite the danger, this did not dampen the enthusiasm of young Joule. Later, he and his brother rowed a boat onto a lake surrounded by mountains, where Joule wanted to test the echo. They loaded a musket with gunpowder and pulled the trigger. With a loud 'bang,' a long flame erupted from the muzzle, singeing Joule's eyebrows and nearly scaring his brother into the lake.
Suddenly, the sky grew dark with heavy clouds, and lightning and thunder began. As Joule was about to go ashore to avoid the rain, he noticed that a significant delay always occurred between the flash of lightning and the rumble of thunder. He wondered why.
Ignoring the impending rain, Joule led his brother up a hill and used a pocket watch to meticulously record the time interval between each flash of lightning and the subsequent thunder. Once school resumed, Joule couldn't wait to share his experimental findings with his teacher and seek guidance.
Looking at the inquisitive student, the teacher smiled and explained patiently, 'Light and sound travel at different speeds. Light is much faster than sound, which is why we see the lightning before we hear the thunder, even though they actually occur simultaneously.'
Joule was enlightened by this explanation. From then on, he became even more fascinated by science. Through continuous study, careful observation, and precise calculation, he eventually discovered the mechanical equivalent of heat and the law of conservation of energy, becoming a distinguished scientist.
