Intuition and Empirical Evidence

Kepler's Orbits

While recently doing research on astrology, I've come to the conclusion that there's no evidence that astrology can predict future events, or accurately describe someone's personality based on celestial bodies, beyond the vague generalities that can apply to anyone. But this leads me to a bigger question about why astrology is so compelling to so many people. Simply put, it has a common sense appeal, or an intuitive appeal primarily because it seems on its surface to be rather scientific. Moreover, celestial bodies can be observed and mapped and predicted mathematically.

But unfortunately, we can't always trust our intuitions in such matters. This is where empirical testing is necessary to pry apart what works from what doesn't. Consider these examples in scientific history of what seemed intuitively obvious (to some) but turned out to be mistaken.

In the late 1600s, King Charles helped establish the scientific organization, The Royal Society of London. He set the members of the organization with a tough question, asking “Why is it that when a glass is full to the brim, and you put a frog in the glass, the water does not overflow?” Well, the scientific minded members contemplated this question for some days until one experimental fellow filled a glass with water, placed a frog in it, and the water actually did overflow!

Aristotle made a common sense mistake that took until Galileo to remedy. Aristotle thought that a heavier object will fall faster than a lighter object. And of course a rock will fall faster than a feather, but once the objects being dropped are heavy enough that air resistance plays relatively no role, then the two objects will fall at about the same speed.

Aristotle believed that objects tend to seek their "proper place," and thus it is that lighter objects fall slowly because they have more lighter elements (air and fire) which tend to rise. On the other hand, heavier objects fall faster because they contain more heavier elements (earth and water) pulling the object down faster.

But Galileo showed that a heavier object and a lighter object will fall at the same rate by experimenting with rolling balls of different weights down inclined planes, in effect slowing down the effect of gravity and measuring the speed traveled with his primitive but useful water clock.

Johannes Kepler did some mathematical experimentation based on observation, and came to the conclusion that the orbits of the planets are eliptical, not perfect circles, which had seemed intuitively obvious.

This conclusion seemed so strange to Kepler that he was initially reluctant to accept it, since the idea of planetary orbits as perfect spheres goes back at least to the ancient Greeks. But he realized that, as counter-intuitive as it seemed, nothing could predict the movement of planets so simply as elliptical orbits.

In fact, even Galileo refused to accept Kepler's claim about elliptical orbits since it seemed to disagree with what he thought was common sense.

There may be times when it makes sense to trust common sense, and we would be fools to dismiss it completely. But in some cases it is best to test our beliefs against nature by seeking out empirical evidence through experimentation when we can. When intuition has failed some of the greatest thinkers in history, we would be wise not to fall into the same trap.