Live a single day on planet Earth, or anywhere else in the universe for that matter, and you will experience the natural phenomenon of heat conduction, which is the term used to describe the natural flow of heat from warmer objects to cooler ones.
Your favorite scoop of ice cream melting on a hot summer day is a perfect example of heat conduction where heat from the air is naturally drawn to the much colder ice cream scoop.
Because it is so commonly experienced in our daily lives, humankind has certainly had some understanding of heat conduction for a very long time.
But not until the 19th century was this understanding sharpened by a French politician and scientist named Joseph Fourier who made a single equation, now known as "Fourier's law" or the "Law of Heat Conduction," that models heat conduction so well it has been little altered since its creation.
To get a handle on the value of this model equation let's go back to the ice cream scoop.
The end result is obvious to our intuition, that the ice cream will eventually melt completely, because we know heat naturally flows from warm to cold. But what is not so obvious is the exact amount of time it will take that ice cream to melt all the way.
Taking some additional information into account like the size of the scoop, as well as the kind of bowl or ice cream cone it's held in, Fourier's law gives us a good estimation for the time it takes the ice cream to melt.
This makes it very useful not just for ice cream lovers, but for anyone interested in keeping something cool in a hot environment or vice versa. Such as computer chip manufacturers or airplane insulation designers.