Long ago and far, far away
Did you know that when you gaze up at a clear evening sky, you’re actually looking into the past?
If you know where to look, you can see galaxies so far away that their light has been travelling since before humans walked the Earth.
Add the magnifying power of a telescope, and you’ll journey to the time when dinosaurs lived. So, when you use a telescope you are in fact using a time machine. Let’s review a few facts that might surprise you.
Space is so vast we can’t use everyday terms. To write out the distance in kilometres to a nearby galaxy you’d need 19 zeros so astronomers use the term “light year” — the distance light travels in one year.
It travels 300,000 kilometres a second, or almost 10 trillion kilometres a year. See what I mean?
Planets are closer than stars so we talk about them in light minutes or light hours. Moonlight is the exception, it takes 1.3 seconds to reach us on the ground. The light from the sun takes eight minutes 20 seconds to travel to Earth, so we can say that it’s 8.2 light-minutes away.
Stars, though, are a different matter. If one of the stars in the familiar “Saucepan” constellation (Orion) exploded tonight I wouldn’t know about it for 900 years. I would have to wait here until the 30th century to see it. The light would take that long to reach me. True!
Right now, Venus and Mars are about 10 light minutes away from Earth. The resulting 20-odd minute round trip for radio signals presents serious challenges for future Mars explorers.
Got a smartphone? Here’s a cool tip. Download an amazing app from Google called “Star Chart”. It’s one of the most incredible things I’ve ever used in astronomy. Simply point to anything in the night sky and it will tell you what it is.
Ask, and it will find planets, stars and constellations for you in a matter of moments, plus it’s got tons of interesting facts and figures on astronomy.
For meteor watchers, the Orionids are visible from October 15 to 29, with the peak of the shower occurring on October 21. This is a good shower for beginners with about 30 meteors per hour. The best time for viewing will be from around midnight until early dawn.
The shower is centred on Orion’s club near the red supergiant star Betelgeuse.
Ever wondered how many people have ever lived on Earth? The Population Reference Bureau took a stab at an answer and came up with 108 billion.
Which means with a current world population of about 7 billion, about 6.5 per cent of the people who have ever lived are alive today.
Earth is getting heavier. Meteorites and spacey junk. We accumulate on average 20-40 tonnes of it per day. In a year, it’s enough cosmic junk to fill a six-storey office building.
Look back into the distant past.