Long ago and far, far away

Geraldton Guardian - - News - David Reneke

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.

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