Basic Navigation – Kepler

When writing science fiction, not every bit of research needs to be included.  This isn’t a textbook, and most readers don’t care about the intricacies of quantum mechanics anyway.  But the scientific facts that do get into the story have to be correct.

Over the next few weeks, I’ll be taking a closer look at some of the most basic rules in astrophysics.  These are things discovered centuries ago and are not cutting edge science, but they should be common knowledge in any space faring society.

Johannes Kepler spent part of his life as an assistant to the Dutch astronomer Tycho Brahe.  During that time, he had access to detailed measurements of planets and stars, which helped him develop three laws of planetary motion.

  1. The planets move in elliptical orbits with the sun at one focal point.  Isaac Newton later developed calculations to prove this, and those calculations are important for planets orbiting binary stars.
  2. An imaginary line connecting a planet to the sun will always cover the same area in the same amount of time.  In other words, planets move faster when they are closer to their star than when they are further away.
  3. A planet’s distance from the sun cubed divided by the time it takes to complete one orbit squared equals a constant for all planets.  This means that with simple algebra, you can find the length of a planet’s year by knowing its distance from the sun.

Although Kepler only worked with planets, we now know these laws apply to any object orbiting any other object.  In order for a space ship navigator to safely pilot his vessel into orbit, he must know these things.  As a sci-fi writer writes about this navigator, the writer should know about them too.

Sources

“Kepler’s Laws of Planetary Motion.” Van Nostrand’s Scientific Encyclopedia Eighth Edition.  Ed. Douglas M. Considine.  NY: Van Nostrand Reinhold, 1995.  Pages 1812-1813.

Tiner, John Hudson.  100 Scientists Who Shaped World History.  San Mateo: Bluewood Books, 2000.  Page 19.

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