Science in the Bluegrass — Clocks, Jupiter and Genesis

Chris Graney

Here is a tale about clocks, Jupiter, Genesis and how science can raise big questions without even trying.

Early clocks were like “grandfather” clocks — pendulum clocks, powered by hanging weights.  They could not be moved and keep accurate time. No clock could keep time onboard a ship.

This made ship travel unsafe. Navigators used the stars to determine location at sea. They had to know what the time was, because the stars continually rise in the east and set in the west, changing with the time of night as well as with location on Earth. Knowing accurate time was a life and death matter. Miscalculated locations led to terrible shipwrecks.

When Jupiter’s moons were discovered by telescope in 1609, they were quickly recognized as a time-keeping breakthrough. Because they circled Jupiter very regularly, they could be used to mark time. Anyone with a telescope, anywhere on Earth, could see them and know the correct time. This “universal clock” would save lives, ships and fortunes.

Bernard de Fontenelle wrote in 1740 that the effort and expense of astronomy would be worthwhile “were there no other use of astronomy than that drawn from Jupiter’s satellites.”

Precise time-keeping and navigation required precise study of Jupiter’s moons. In the 1670s, a young astronomer named Ole Römer discovered something weird about them: Their speeds around Jupiter varied slightly depending on Jupiter’s distance from Earth. Römer realized this was because the moons’ light took time to reach Earth; more distance meant more time, which influenced their perceived speeds.

Kids in school today learn about the speed of light, and that it takes years for light from even the nearest stars to reach Earth. But before Römer, scientists had thought light was instantaneous.

Ole Römer was not out to raise big questions involving Genesis. But…

When God made human beings as recorded in Genesis 1, were the stars visible in the night sky? 

If light is instantaneous, then of course they were. God creates the stars on the fourth day (Genesis 1:14-19). Their light reaches Earth instantly. They are visible in the sky that evening.

But if light has a speed, that suggests when God creates the stars on the fourth day, none are visible from Earth. The light from the nearest one takes years to arrive. Then stars appear, one at a time, over a period of more than a thousand years — the bright star Deneb in the constellation of The Swan is so distant that its light takes well over 1,000 years to reach us. The Andromeda Galaxy, visible at night to the naked eye, is so distant that its light requires 2,000,000 years to get here.

But Genesis says God on the fourth day set the stars in the dome of the sky, to give light upon the Earth, and saw they were good. That seems to say the stars were indeed visible that evening.

Would that mean that by the evening of the fourth day the universe appeared to be old — over 1,000 years old based on Deneb; over 2,000,000 years old based on the Andromeda Galaxy? Is Genesis saying that God created the universe in mature form, just as God created Adam and Eve in mature form?

Transport an unwitting astronomer with all the tools of modern science to the Garden of Eden on the seventh day. Would that astronomer determine the universe to be quite old, based on looking at the sky, just as that astronomer would determine Adam and Eve to be many years old, based on looking at them?

Such big questions — and Römer was just trying to keep time and save lives!

Chris Graney is an astronomer on the staff of the Vatican’s astronomical observatory. The observatory recently launched a new website at

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