Size of Space Understated in Movies

Most people recognize that space (as in the outer space kind) is big.  The distance between objects is tremendously large.  Many movies and TV shows try to emphasize the size of space, but usually fail.  They fail, not by overstating the size of space, but by vastly underestimating how large the Universe is.

Here's a perfect example.  My daughters and I recently watched the animated movie Planet 51.  In the movie a human astronaut lands on an alien planet occupied by an equally advance population of aliens.  At one point the human says that he traveled across the Universe to reach this planet.  Okay, across the Universe is a huge distance.  But later the human contradicts himself by saying Earth was 20 billion miles away.  20 billion is a large distance...compared to the size of the Earth.  You'd have to drive around the equator of the Earth 800,000 times to reach 20 billion miles.  Wow!  However, compared to the size of the Universe, 20 billion miles is tiny.  Let's put this in perspective.  The Earth is 93 million miles away from the Sun.  20 billion miles is 215 times farther away.  Pluto is 40 times farther away from the Sun than the Earth.  20 billion miles is about 5 times farther than Pluto's distance to the Sun.  It's true that this is a large distance, but again, compared to the size of the Universe, this is still a tiny distance.  In fact, 20 billion miles is still within the boundary of our very own Solar System!!!

So how large is the Universe?  The physical size of the Universe is about 150 billion light years (see How Big is the Universe? for more details).  150 billion light years is 44 TRILLION times farther than the 20 billion miles given in the movie.  As a percent, the movie astronaut traveled 0.0000000000023% the distance across the Universe.  Talk about an underestimate of the distance traveled!!!

The moral here is to be careful discussing distances with your kids.  Space is huge.  Much larger than you think.  A billion is a big number.  A trillion is a big number.  Both are tiny compared to the overall size of the Universe.