Astronomy

How Big is the Solar System how far away is the Sun how far away is the Moon how far away is Mars



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The Real Size of our Solar System

Do you really have any idea just how unimaginably huge, no, in fact, how totally incomprehensibly vast our solar system and universe are?

Forget the cute and colourful pictures you see in kid’s science books.  If they were shown in true scale, believe me, they’d need much, much, much bigger books.

To truly understand the astonishingly immense scale of our solar system, I firstly must offer you the opportunity to appreciate the distance from our own Earth to our sun, Sol.  This distance averages at approximately 93 million miles or 149 million kilometres or 1 Astronomical Unit (AU).  Now just how far is that?

Well, in comparison, our moon, Luna, averages approximately 240 thousand miles from the Earth.  Multiply that by around 387 times, and you’ll be on the right track to how far away our sun is.  Put in more understandable terms maybe; it took Apollo 11, the first mission to land men on the moon, a little over 3 days to reach their destination.   At the same average speed that those astronauts travelled to the moon, it would take you 3.18 years to reach the sun.

So, now that you know the distance from the Earth to the sun, you can probably start to appreciate that drawings that show the earth as pea sized, with Mars just a little further out from the sun, and Mercury and Venus just a little closer to the sun, are a tad misleading.

Mercury is closest to the sun at 0.38 AU’s.  That’s very roughly 35 million miles, or again in our possibly slightly more understandable terms, that’s 1.2 years of manned space travel.  Next is Venus at 2.3 years away, then us of course at 3.18 years distance.  Then we’re out to the next planet, Mars, and you’re increasing that distance to the sun to 4.83 years.

How about we return to our science book now, which might just show an ever so slightly bigger gap between Mars and Jupiter.  Well that gap is a bit more than ever so slightly bigger.  In our new found measure of distance we jump from Mars at 4.83 years travel to the sun, to Jupiter at 16.5 years out.  That gap on the page between Mars and Jupiter now looks a lot different, wouldn’t you say?

Ok, so again on our page we move a little further out to Saturn, a little further out being a trivial twice the distance away from the sun as Jupiter, at 30 years space travel time, and we’ll double that again out to Uranus where you’ll be greying nicely at 61 years away from the sun.   

Now we’ll nip out to Neptune, which we might just make in a lifetime, if we’re really, really lucky and don’t eat too much fat or smoke or drink or do anything silly, but I’d actually suggest taking your wife and having a baby along the way, a baby who can grow up and take over the controls if you pass on, as it’ll actually take around 95 years to get that far out.

As for our science books, they all tend to show a bigger gap going out to the furthest of our nine major planets.  Tiny Pluto, only about one tenth the size of the Earth.  But in reality, to get to the outer reaches where Pluto reigns, you’ll probably need a girl friend along for that son of yours, because it’ll probably actually be their son, your grandson in control when he finishes the roughly 125 year journey.

So, when you next look at your child’s science book, or happen upon a diagram of our solar system somewhere, you’ll now have a little more of an idea of the real distances involved.

And if you happen to be wondering about venturing a little farther out still, perhaps to our nearest neighbour star, Proxima Centauri, then I’ll give you an idea of when to set out.  Let’s say, if you wanted to arrive tomorrow, travelling at the same speed that Neil Armstrong, Buzz Aldrin and Mike Collins travelled to get to the moon, then in order to reach Proxima Centauri, you would have had to have left Earth approximately 200 thousand years ago, or in other words, when modern man, Homo sapiens, the first human beings, are believed to have evolved in East Africa...according to the fossil record of course.

We’ve certainly come a long way since then, but if we want to reach the stars, boy are we going to have to go a long way still.

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