revolved around the Sun.
Yet, acceptance of the Copernican cosmology took quite a long time despite the fact that it fit careful observation of the facts much better than the model Ptolemy had offered. Copernicus first wrote about his heliocentric ideas in the early 1500s, and it was a full century later that Kepler supported those ideas with discussions on the elliptical orbit of Mars. About the same time, Galileo affirmed Copernicus through the use of a telescope. Even then, Copernicus’ heliocentric theory was banned in 1616, and it took most of the 17th century for the idea that the Earth revolved around the Sun to take root in people’s minds. Isaac Newton helped cement the idea with his work on gravitation, but it took until 1758 for the Roman Catholic Church to finally end its prohibition on books that taught heliocentrism.
Poor Ptolemy of Alexandria. He has gone down in history as the scientist who got it wrong on two fundamental truths in science. He was incorrect about the Earth as the center of the solar system, and he argued against the possibility of four dimensions.
Wrong Ideas – Aether
For many moons, astronomers and cosmologists believed the universe was filled with a material called the aether. Light was understood to be a wave, which meant it needed a medium through which it could travel, like waves on a cosmological pond. Aether was considered the pond through which light traveled across the universe. The aether was seen as an absolute reference frame in respect to the rest of the universe; everything had its speed in reference to the aether.
In 1887, the Michelson-Morley experiment attempted to measure the speed of aether itself. Michelson and Morley expected that as light traveled with the aether, it would race along faster, and as it traveled against the aether, it would move slower. They set up a detection device with a light source, mirrors and a telescope, and they found that no matter where the Earth was in its rotation around the Sun, the light always traveled at the same speed. This was an early experiment that demonstrated that light travels at the same speed in all inertial reference frames — and it all but disproved the existence of “aether.”
Wrong Ideas – Infinite Speed of Light
The speed of light itself has been a matter of confusion and controversy. Philosophers and scientists including Kepler, Descartes and Galileo used reasoned arguments that the speed of light was instantaneous. In 1676, Danish astronomer Ole Rømer made observations about the orbit of Jupiter’s moon Io, however, that led him to conclude the speed of light had a finite measurement. Io’s whirling spin around Jupiter takes just 42 ½ hours per revolution, and the precise time Io disappears behind Jupiter can be measured. Rømer found that it took longer for the reflective light from Io to reach the Earth when Jupiter was far away from Earth than it took when Jupiter was near. This meant the light couldn’t be arriving to the Earth instantaneously; it took a few minutes. Rømer sent his data to his friend Dutch astronomer and mathematician Christiaan Huygens, who calculated that light sped along at 16 2⁄3 Earth-diameters per second — about 132,000 miles per second. This value was off by about 1/3 of the correct value of 186,000 mps, because the exact distance of the planets wasn’t known at that time, but Huygens got into the right ballpark.
In 1728 James Bradley noticed that the positions of stars seemed to change over the course of a year. He carefully watched a star in the constellation Draco, then other stars as well, and he used his knowledge of the Earth’s speed around the Sun to calculate the speed of light as 301,000 km/s. In 1849, Armand Fizeau used mirrors and a spinning wheel setup to measure the speed of light at 315,000 km/s and Leon Foucault tried a similar experiment with rotating mirrors, narrowing the speed of light to 298,000 km/s.
Light is known as one of the fundamental constants of nature. Yet, we’ve learned in recent years that the constants of nature aren’t so constant. The speed of light in a vacuum appea