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Distances in Space
Well,
that's a long way!
Everything
is such a long way apart out there that measuring distances becomes
meaningless if we use Earth units such as kilometres. Just have
a look at the table below for comparisons between different measures.
More useful in space are the Astronomical
Unit, the Light year
and the Parsec. Strange names?
They are all explained below.
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Distance
|
Astronomical
Unit
|
Kilometres
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Light-Speed
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Sun to Earth
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1
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149,978,700
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8.34 minutes
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| Light year |
63,240
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1 year
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| Parsec |
206,265
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3.2616 years
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Astronomical
Unit
The mean distance from the Earth
to the Sun, and often abbreviated to A.U. I think using this
measure gives the best idea of how far the closest objects are.
Light
Year
You're not going to believe this,
but one light year is the distance that light travels in one
year! That's through the vacuum of space. You can see how for
this is from the table above: a distance equal to over 9 trillion
kilometres.
Parsec
The distance that light travels
in 3.2616 years. Why!? I hear you cry. The word Parsec comes
from a mixture of Parallax and Second.
Does that clear it up? This is all to do with measuring the
distances to stars using their shifted position as the Earth
orbits the Sun. (Full explanation link follows soon).
Big Numbers
The number 1000 can be written
in mathematics speak as 10³, or 10^3 which we shall use due
to internet limitations. This means 10 to the power of 3 or 10
multiplied by 10 multiplied by 10 (10x10x10). We can use larger
powers for millions, billions etc. Here's my guide:
| 10^2 |
100 |
Hundred |
| 10^3 |
1,000 |
Thousand |
| 10^6 |
1,000,000 |
Million |
| 10^9 |
1,000,000,000 |
Billion |
| 10^12 |
1,000,000,000,000 |
Trillion |
| 10^15 |
1,000,000,000,000,000 |
Quadrillion |
| 10^18 |
1,000,000,000,000,000,000 |
Quintillion |
A
Little More about Light
Light travels at almost 300,000
kilometres per second (186,282 miles per second). Even at this
tremendous speed light can take a long time to get from one place
to another. Starting close to us, light takes 1˝ seconds to get
from the Moon to your eye. A little further away is the Sun, and
light starting its journey from there takes 8˝ minutes to reach
the Earth. So, we’re not actually seeing the Sun as it is right
now, but how it WAS 8˝ minutes ago: we’re looking into the past!
Much further away is the closest star, Proxima Centauri. Light
from this small red star takes over 4 years to get to Earth, and
the further we go the longer it takes light to reach us. Some
of the furthest objects are over 10,000 million light years away!
We’re looking back in time close to when the Universe itself was
formed.
Light travels
at a constant speed in whatever it is zooming through. If that
is water then light-speed is two-thirds that of space.
The speed of light
is EXACTLY 299,792.458 kilometres per second.
© Anton
Vamplew 2008
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