Hubble Space Telescope Misconception #1

There are many misconceptions concerning the Hubble Space Telescope (HST).  The HST, launched in 1990 and still operational today, is probably the most famous telescope in the world.  If you ask the average person to name one telescope, the likely answer is the HST.  The HST has a 2.4 meter mirror that collects light and is located in space, approximately 350 miles above Earth's surface.

NASA/IMAX [Public domain]

The HST is famous for being an excellent telescope that has taken some amazing pictures.  The misconception comes in when people are asked why the HST takes such amazing pictures.  The most common answer is that Hubble is closer to the stars.  Well, technically this is right.  The HST is approximately 350 miles closer to the stars than a telescope on Earth, but let's put this distance in perspective.  The nearest star, other than the Sun, is Proxima Centauri, approximately 4.24 light years away.  Converting from light years to miles gives us a distance of about 25 TRILLION MILES!!!!!  Looking at this in terms of percentages, the HST is about 0.0000000014% closer to this star than a telescope on Earth.  In other words, distance plays no role in the HST's ability to take amazing pictures.

A way to make this clear to younger children is to ask them to look at a distance building, tree, building, billboard, etc. from inside their house.  Then ask them to take one step out the front or back door.  Does the object look any closer?  Nope.  Is it closer.  Sure, by one step, but not nearly close enough to make a difference in your ability to see details on the object.  (Thanks to my high school students for this analogy.)

Another common misconception is that the HST is better because it's bigger.  Again, this is wrong.  The HST has a 2.4 meter mirror.  The largest optical telescope on Earth is the 10.4 meter Gran Telescopio Canarias on the Canary Islands.  In terms of how much light these telescopes collect, the Gran Telescopio Canarias collects about 19 times more light than the HST.  

So if it's not distance and it's not size, what makes the HST so amazing?  The answer is Earth's atmosphere, or lack thereof.  Light from stars traveling through Earth's atmosphere is exposed to turbulence (moving pockets of air).  This turbulence causes images to not be as clear as they would be in the absence of Earth's atmosphere.  The HST has the advantage that it sits above Earth's atmosphere and light is not subject to turbulence.  Thus the images are much clearer.  

There you go.  One less misconception to worry about.