Tripping the light fantastic

Our nearest galactic neighbour, The Andromeda Galaxy, 2.5 million light years away
Our nearest galactic neighbour, The Andromeda Galaxy, 2.5 million light years away

Last week scientist announced that the amount of galaxies in the universe had been underestimated by as much as a factor of 20. Major news, but not something that really affects our daily lives. The discovery does however, illustrate the vast scale of our universe. Thankfully, we as humans have developed the brain capacity, the intelligence and the curiosity to help us understand our place within it. Take for example the speed of light. It travels at 300,000 km per second. Pretty much instantaneous for us on earth, but really noticeable in the realm of the galaxies, stars and planets. Light from the moon takes little over a second to reach us, whilst light from the sun takes over 8 minutes. That means that the light from the sun that is hitting your eyeball is over 8 minutes old.

And once we get out as far as the planet Saturn. Light and communications signals take approximately 80 minutes to get here. Not ideal for a quick 2 way telephone conversation. The north star, Polaris, which has been used for navigation for millennia is over 430 light years away. If you look at that star tonight, the light you see started on its journey in 1583.

What about the furthest star you can see with your naked eye. That particular honour falls to a star in the constellation of Cassiopeia with the name v762; and light from that star is over 16,000 years old when it reaches us. It left when our ancestors were daubing pictures of bison and horses onto the walls of caves in northern France, before there was writing and before any modern history.

But the honour for the furthest object visible to the naked eye falls to the Andromeda galaxy. Visible to us as a large faint smudge in the night sky, the light from Andromeda left on its way to earth over 2.5 million years ago, well before modern man had evolved.

Grab a simple set of binoculars and get under a dark sky and you can spot light from galaxies over 75 million light years away. That light set off on its journey 75 million years ago, long before there was anything remotely human like and our ancestors the primates were just beginning to gain a foothold on the evolutionary tree. All of the evolution and development of humans from our predecessors as apes took place in the time it took that light to travel across space to reach your eyeball.

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