Miles or Km

Got a beginners' question? No matter how elementary, our friendly forum community and magazine writers will answer it.

Miles or Km

Postby starchaser7 » Sun Mar 11, 2012 6:05 pm

Warning...Rant !!!
Why do so many tv programs swap between Miles and Km when talking about the universe?
Anyone else noticed how inconsistent the scales are when presenters talk about the size of the universe, my theory is that Km sounds more impressive as the numbers are bigger and Miles when the figure needs to be localized.
Any thoughts on this? Because when I speak about the sky I always use Miles because all of our road signs and speed limit are in miles so it's a unit of measure people (UK) can relate to.
Perhaps we need a fixed universal standard of measurement without swapping between figures because the numbers seem more impressive...aaaargh!!
Actually I really am not that bothered but it does make me wonder.
Posts: 56
Joined: Mon Feb 13, 2012 7:07 pm

Re: Miles or Km

Postby Astro Chav » Mon Mar 12, 2012 12:50 pm

They use miles for general use in the USA and still use Farenheit instead of Centigrade for temperature. Remember that our audiences are often outside the UK and we need to use both traditional and metric units to cater for our global audience.
How can I be at one with the universe when we don't know what 96% of it actually is?
Astro Chav
Posts: 388
Joined: Sun Feb 19, 2012 1:26 pm
Location: Based in south west England but can be anywhere

Re: Miles or Km

Postby david48 » Tue Mar 13, 2012 4:53 pm

Don't most British people with any knowledge of astronomy, still think of the Earth as the memorable 93,000,000 miles from the Sun? Not the equivalent in kilometres.

And the same for other measurements - like the Earth 7,926 miles in diameter, the Moon 2,160 miles, the Moon about 240,000 miles from the Earth, Jupiter 89,000 miles in diameter and 483,000,000 miles from the Sun, Mercury 36,000,000 miles from the Sun, which is 886,000 miles in diameter, and so on..

These mile distances are familiar to everyone in the UK who has an interest in astronomy, and grew up using them. Such enlightened persons can never really think of them in kilometres. Whereas persons with no knowledge of astronomy, don't know the difference.

Perhaps that's why the TV programmes vacillate between miles and kilometres - the programme producers don't know who's watching their stuff - amateur astronomers, or ignorant chavs.
Posts: 173
Joined: Mon Feb 13, 2012 7:13 pm

Re: Miles or Km

Postby starchaser7 » Tue Mar 13, 2012 6:57 pm

Point taken with both replies, just I saw the BBC trailer for orbit and all the distances and speeds were given in Km which is what prompted the post. But I can now see the advantage of giving each version of distance depending on who is listening.
Posts: 56
Joined: Mon Feb 13, 2012 7:07 pm

Re: Miles or Km

Postby arthur dent » Wed Mar 14, 2012 12:55 am

To be honest, the move is probably towards km simply because today's children and young adults were brought up on metres/kilometres/grams/kilograms/Celsius at school. Sure they were told about miles/pounds/Fahrenheit but I'm sure that they think in metric. I can estimate in both metric and Imperial, but I think in Imperial (more of this in a mo).

Likewise, some of us can use both. I'm happy to say that light travels at 186,282 miles per second or 300,000,000 metres per second, that the Sun is 93,000,000 miles away from the Earth or 150,000,000 kilometres. I'm not bothered, I can use both. Mars is 142.5 million miles or 228 million km from the Sun on average. I don't mind using miles or km (although I have been teaching science long enough to have the km distances engraved in my brain!)

I'm also sure that programme makers have to cater for a wide audience - those that use/think in Imperial measure and those that use/think in metric - and use both sets. This is also true of the weather forecasts where both Fahrenheit and Celsius temperatures are quoted. Bizarrely, I think that zero Celsius means that it is going to be chilly today but in summer I know that it will be uncomfy when it gets to the high 70's / low 80's (Fahrenheit of course).

In typical fashion, the UK fumbled the issue in the 70's and early 80's when we were going metric but did so half-heartedly - which is why we have such a mess as far as our units go, an example being that we talk of petrol consumption in miles per gallon (mpg) but have petrol priced in litres (and although on the car forecourt/brochure or website the fuel consumption may be quoted in litres per 100km, how many folks honestly can say that their car averages 8 litres per 100km instead of 35mpg. Not many I'll bet!)

If you want a further example - try buying timber - you can get 1.8m, 2.1m, 2.4m and 3m lengths of timber at Wickes and B&Q - why? Well these are multiples of 30cm (= 1 'metric foot') so 1.8m is a 6-foot length, 2.1m = 7-foot, etc, etc). Or go and buy some cloth off a roll at a department store or habidashers. The cloth comes in 36-inch or 48-inch widths but you buy it priced 'per metre length' - aaaarrrrggghhh!

Personally (although it seems to be capitulating to Europe & Napoleon here) the metric system is much more self-consistent and logical. Who in their right mind (whatever the historical reasons my be) would come up with a system where we have 12 inches to the foot, 3 feet to the yard, 1,760 yards to the mile (or if you prefer 63,360 inches to the mile) - what a crazy system - or 16 ounces in a pound, 14 pounds in a stone and 160 stones in a ton (or 2,240 pounds) Whereas 10mm to the cm, 100cm to the m, 1000m to the km makes much more sense (all based on powers of 10), as does 1000g to a kilogram and 1000kg to a tonne.

The only beef that I have with the metric system is in the units. Capitals signify larger multiples (eg M = mega = million, G = giga = billion, T = tera = trillion) and lower case signify smaller multipliers (eg m = milli = thousandth, c = centi = hundredth), but the multiplier k = kilo means thousand (!) - again, aaaarrrrggghhh!

Anyhoo, rant over

Meade ETX-105EC
Celestron NexStar 6SE, 9x50 RACI finder, MRF, powertank & wing thing
Hyperion 8-24mm Zoom + various other EPs
Canon 550D + T-ring, Philips NC880C and 900C webcams for AP (all un-modded)
arthur dent
Posts: 277
Joined: Mon Feb 13, 2012 6:52 pm

Re: Miles or Km

Postby physicist » Mon Mar 26, 2012 8:54 am

should endevour to use the SI system at all times! :)

Posts: 92
Joined: Mon Feb 13, 2012 6:43 pm

Return to Ask a silly (astronomy) question

Who is online

Users browsing this forum: No registered users and 2 guests