WHAT WE AREN'T SEEING WHEN WE LOOK AT THE SKY

When we look at the sky, the vista that we see isn't really there.

Let me explain. I remember one January night, I was looking at the galaxy M82 through the telescope when I spotted a blazing white dot caused by a supernova explosion. The next day, its presence was suddenly reported by the worldwide media; I'd seen this supernova shortly after the explosion happened!

Ahem! Well, that's far from true, actually, far from true!

A light year (LY) is the distance that light travels in one earth year. The galaxy in which the explosion occurred is estimated to be about 11 million LY distant from us. So, the explosion actually took place about 11 million years ago. What I saw was just an image of it – the light radiating from it.

Doesn't this just make your mind boggle with the distance involved? Light travels an equivalent straight-line distance to about seven times around the earth in one second; that's how fast it is travelling. One hundred and eighty six thousand miles every second, and yet it took about 11 million years for that light to reach my gazing right eye.

Hence, when you look at the sky, the view is not true. You are looking into the past, seeing what was. You may even be seeing some objects that are no longer there! Certainly the more distant ones would have moved in the time that the light has taken to arrive at your eyes. You aren't seeing these celestial objects at all; you are seeing a collective image of them. This image spans a great expanse of time as well as distance.

For example, you may see the yellow blaze of Jupiter shining down. You are seeing it as it was about half an hour ago. Dropping your gaze down to not far above the horizon, you then notice another bright object, the Dog Star (Sirius). You are seeing it as it was about 8 years ago. You then look at the famous star Betelgeuse, in Orion, your eyes attracted to it because you swear that discern a hint of red in it. You are seeing Betelgeuse as it was about 640 years ago, not as it is now, if it's there at all! Looking up above Orion, your gaze wanders into the constellation Taurus and is quickly pulled upwards towards a fuzz in the sky. This is the Pleiades, famously known as the `Seven Sisters'. You are seeing this group of stars as it was about 425 years ago.

Grabbing a handy pair of binoculars for a closer look, you pan further upwards into the constellation Auriga. "Ooh!" you exclaim, as you spot the small, tight star cluster M36, seeing it as it was about 4000 years ago! You continue upwards and to the right, and you notice another fuzz, this time the aforementioned Andromeda Galaxy. You are seeing it as it was about two and a half million years ago. You then meander towards the Great Bear. Just north of it you see a fairly empty patch of sky. If you had bigger binoculars, with bigger objective lenses, you'd see two faint fuzzies. These would be M81 and M82 galaxies. You'd be seeing them as they were about 11 million years ago!

Doesn't this put a different perspective on the sky? If you gulp in the entire expanse of the night sky with a casual glance, you are seeing across a vast distance of time, as well as seeing across a vast distance! What you see is temporally incoherent....it isn't true....you can't say it's there....it's not! It's analogous to looking at a scene here on earth and seeing medieval men battling it out with swords just over there, and then to their left seeing a woman in a 1960s miniskirt and knee height leather boots snuggling up to a flared trouser adorned man, and then next to them seeing two dinosaurs in repose, and then, to the right of them seeing a two year old car being advertised as new! This is a reality that only has its reality across time.

When I saw this supernova explosion, I was looking at an event that took place long before humanity existed, assuming, that is, that we can trust our paleontology! Isn't that amazing?