Tuesday, 6 December 2011

Travelling to Pluto?

A few months ago I came across Audible.com.  Audible is a company owned by Amazon which specializes in selling audio books (and pretty great quality I must add).  So I subscribed to get one audio book every month and after research I settled on getting Bill Bryson's A Short History of Nearly Everything.  An absolutely wonderful book which I heartily recommend, but there is one section that I keep returning to again and again as it fascinated me to no end.  I decided I should share that brief section with everyone and so played the audio book and typed down what was being said as accurate as need be.  The book starts by talking about the universe and how it started (where you're writing about the history of 'everything', how the universe began would be the best place to start I guess) and Bill begins showing how immense our universe is by just showing us our own solar system.  A small picture in the grand scale of things, but effective in it being a small picture.

Our solar system is so vast that even the maps we look at in books are not even remotely to scale.  This is a necessary deceit to get all the planets on the same piece of paper.  For example, Neptune is five times away from Jupiter than Jupiter is from us.  Such is the distances that it isn't possible or practical to draw out the solar system to scale.  On a diagram of the Earth drawn to scale with the Earth at the size of a pea, Jupiter will be over 300m away, and Pluto 2.5km distant and about the size of a bacterium.  On the same scale, Proxima Centauri, our nearest star will be 16,000 km away!  Even if you shrank down everything so that Jupiter will be the size of a full stop at the end of a sentence and Pluto was no bigger than a molecule, pluto will  still be more than 10m away!

Our solar system surrounded by the Oort Cloud.

If we rode a spaceship that can travel at the speed of light (which is not possible) (300,000 km/s) it will take us 7 hours to get to Pluto from Earth.  Currently at the speed of a normal space ship (56,000 km/h) it will take 9 years to reach Uranus and a dozen years to cross the orbit of Pluto.  By the time we get to Pluto the Sun is as small as a pin head.  At this point, the Oort Cloud, at the edge of our solar system, is 10,000 years away from us.  Where Pluto is about 40 AU from the Earth, the heart of the ort cloud is about 50,000 AU.  In other words, it is remote.  Based on what we know now and can reasonably imagine, there is absolutely no prospect that any human being will visit the edge of the solar system.  Ever.  It is just too far.  And remember, we're talking only about our own solar system, our Milky Way galaxy contains billions of solar systems and there are hundreds of billions of galaxies in the universe.