# The speed of Light

and other statistics
 The speed of light Statistical figures Travelling at the speed of light Travelling at the speed of a rocket

Speed of light

On Earth common measurements for distances are metres, kilometres, inches and miles to name a few. Due to the colossal size of space, these measurements are no longer adequate enough to describe distances. Instead, cosmic distances are measured in light years. Say a celestial object was ten light years way from you; this would mean that it would take light ten years to reach that object, from where you are now. Light travels at approximately 300 000km/s (299 782 km/s) and a light year is approximately equal to 9 461 000 000 000km (9.461 x1012 or 9.461 trillion kilometres). Light from the stars that you see at night can only been seen on Earth after they have travelled the distance that they are from Earth, so if star is perhaps 5 light years away, its light must journey for 5 years to reach Earth, to be seen. Using powerful telescopes such as the Hubble space telescope scientists have been able to see stars, galaxies and constellations that are millions of light years away, whereby the images and events that they are seeing now, took place millions of years ago. Also used in measuring stellar distances is the Parsec unit of measurement which spans about 3.26 light years.

Statistics:

• The sun is 0.000015 light years from Earth. It takes the light from the sun about 8 minutes to reach Earth so the light from the sun that you are seeing was in fact created 8 minutes ago.

• The nearest star to earth is Proxima Centauri in the Centaurus constellation which is about 4.2 light years away. This star cannot be seen by the naked eye. Apparent magnitude = 11, absolute magnitude =15.5.

• The Milky Way galaxy (our galaxy) is a spiral galaxy with a diameter of 100 000 light years.

• The nearest galaxy to the Milky Way is the irregular spiral shaped Large Magellanic Cloud which is 170 000 light years away with a diameter of 30 000 light years.

• The nearest galaxy that is larger than our own is the spiral shaped Andromeda (M31) galaxy which is 2 200 000 light years away with a diameter of 150 000 light years.

• The brightest star in the night sky to Earth is the Sirus A star which is 8.6 light years away and is a white main sequence star. Apparent magnitude=-1.4, absolute magnitude=1.4.

• Venus has a maximum apparent magnitude of -4.4, Mars is -2.8, Jupiter is -2.8 and Mercury is -1.4 making these planets stand out in the night sky.

• If the sun was a basketball ?

• Pluto would be over one kilometre away.

• the nearest star, Proxima Century would be 8600 kilometres away. If the basketball sized sun was in London, then Proxima Centuri would be in San Francisco and only six other stars would be fitted on the sphere of the Earth.

Speed of light:

Travelling at the speed of light it would take us...
 Place Time taken Pluto 6 hours Proxima Centauri (nearest star) 4.3 years The most distance stars in our galaxy 75 000 years Nearest small galaxy; the Larger Magellanic cloud 160 000 years Nearest large galaxy; Andromeda Galaxy 2 200 000 years Most distant parts of our universe 15 000 000 000 years

Apollo speed:

The Apollo spacecrafts took three days to reach the moon. At this speed it would take:

 Place Time taken Venus 11 months Mars 1 year 8 months Mercury 2 years Jupiter 13 years Saturn 30 years Uranus 61 years Neptune 96 years Pluto 126 years Nearest star 790 000 years

Statistics source:

Funfax Space, 1994 Henderson Publishing

Refer to Bibliography for more information.