Unappropriate velocity unit - km/h

Introductions, Rules, Announcements, and Feedback
jiri
Asternaut
Posts: 3
Joined: Tue Sep 25, 2012 2:43 am
Location: Neckargemuend (near Heidelberg), Germany and Praha, Czech Republic

Unappropriate velocity unit - km/h

Post by jiri » Tue Sep 25, 2012 3:19 am

Velocity unit of km/h is suitable for passengers, cars and planes. In astronomy, instead, the SI unit (k)m/s should be standard. In the picture text, values of >500000 km/h are used - crazy numbers, too many zeroes. Should the many zeroes impress the innocent laymen? I guess, they are confusing instead of informing. Cheers, Jiri

User avatar
Chris Peterson
Abominable Snowman
Posts: 15933
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: Unappropriate velocity unit - km/h

Post by Chris Peterson » Tue Sep 25, 2012 6:09 am

jiri wrote:Velocity unit of km/h is suitable for passengers, cars and planes. In astronomy, instead, the SI unit (k)m/s should be standard. In the picture text, values of >500000 km/h are used - crazy numbers, too many zeroes. Should the many zeroes impress the innocent laymen? I guess, they are confusing instead of informing. Cheers, Jiri
The captions aren't written for astronomers or scientists, though. So using familiar units makes a lot of sense. I think the average person has a better feel for 500,000 km/h than they do for 140 km/s.

In general, I like to see units given in both the conventional scientific form as well as a parenthetical conversion to more widely used units when appropriate. That serves both clarity and education.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

User avatar
JohnD
Tea Time, Guv! Cheerio!
Posts: 1377
Joined: Wed Feb 16, 2005 2:11 pm
Location: Lancaster, England

Re: Unappropriate velocity unit - km/h

Post by JohnD » Tue Sep 25, 2012 10:26 am

Don't agree, Chris! I don't think that "the average person has a better feel for 500,000 km/h than they do for 140 km/s".

No one has a mental handle for 500,000kms, unless like you they are an astronomer.
But everyone who can think in kms or can convert them to miles will realise, gosh, my brother John lives in Atlantic City, Marseilles, York or Foggy Bottom(say) and that's only 140kms (90mls) away.
There in one second! That's fast!

John

jiri
Asternaut
Posts: 3
Joined: Tue Sep 25, 2012 2:43 am
Location: Neckargemuend (near Heidelberg), Germany and Praha, Czech Republic

Re: Unappropriate velocity unit - km/h

Post by jiri » Tue Sep 25, 2012 11:48 am

You are right, JohnD. I wrote the suggestion because I have been teaching >7000 US students in Europe over 40 years and know that what you call "a mental handle". Yes, objects outside Earth may be fast and more people should better understand them. I am new in SA (Star Asterisk): how to let the picture text author know about this subject?
Jiri

User avatar
geckzilla
Ocular Digitator
Posts: 9158
Joined: Wed Sep 12, 2007 12:42 pm
Location: Modesto, CA

Re: Unappropriate velocity unit - km/h

Post by geckzilla » Tue Sep 25, 2012 12:02 pm

You can find their email addresses at the bottom of this page:
http://apod.nasa.gov/apod/lib/about_apod.html

And, personally, meters and kilometers make no sense to me. Better put it all in yards and miles. Or, better yet, football fields!

-Typical American
Just kidding.
Just call me "geck" because "zilla" is like a last name.

User avatar
neufer
Vacationer at Tralfamadore
Posts: 18066
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: Unappropriate velocity unit - km/h

Post by neufer » Tue Sep 25, 2012 1:08 pm

JohnD wrote:
Don't agree, Chris! I don't think that "the average person has a better feel for 500,000 km/h than they do for 140 km/s".

No one has a mental handle for 500,000 [km/h], unless like you they are an astronomer.
I agree wholeheartedly!

Multiple zeros should be avoided whenever possible regardless of the method used.

Everyone should be able understand that 140 km/s is rather fast as compared to most motions in the solar system
but very slow as compared to the speed of light.

500,000 km/h is just a funny sounding number that nobody can relate to
(and the "km/h" often gets lost in the relative small print).
APOD Robot wrote:Image NGC 2736: The Pencil Nebula

Explanation: This shock wave plows through space at over 500,000 kilometers per hour.
140 km/s is, in fact, not an untypical sort of particle/sound velocity for a million degree hydrogen plasma.

Our own supersonic solar wind has a velocity of ~ 400 km/s.

500,000 km/h does not help in any way in getting a physical grasp of what is actually taking place.
Last edited by neufer on Tue Sep 25, 2012 1:53 pm, edited 1 time in total.
Art Neuendorffer

Wombat
Asternaut
Posts: 7
Joined: Tue Sep 18, 2012 5:35 am

Re: Unappropriate velocity unit - km/h

Post by Wombat » Tue Sep 25, 2012 1:19 pm

"In general, I like to see units given in both the conventional scientific form as well as a parenthetical conversion to more widely used units when appropriate. That serves both clarity and education."

I agree 10.2E9 times.

User avatar
owlice
Guardian of the Codes
Posts: 8386
Joined: Wed Aug 04, 2004 4:18 pm
Location: Washington, DC

Re: Unappropriate velocity unit - km/h

Post by owlice » Tue Sep 25, 2012 2:04 pm

neufer wrote:
JohnD wrote:
Don't agree, Chris! I don't think that "the average person has a better feel for 500,000 km/h than they do for 140 km/s".

No one has a mental handle for 500,000 [km/h], unless like you they are an astronomer.
I agree wholeheartedly!
I don't, but then, I'm more like the average person than you are.
neufer wrote:Multiple zeros should be avoided whenever possible regardless of the method used.
Disagree. Multiple zeroes are okay in many contexts, including this one.
A closed mouth gathers no foot.

User avatar
Chris Peterson
Abominable Snowman
Posts: 15933
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: Unappropriate velocity unit - km/h

Post by Chris Peterson » Tue Sep 25, 2012 2:12 pm

JohnD wrote:Don't agree, Chris! I don't think that "the average person has a better feel for 500,000 km/h than they do for 140 km/s".

No one has a mental handle for 500,000kms, unless like you they are an astronomer.
But everyone who can think in kms or can convert them to miles will realise, gosh, my brother John lives in Atlantic City, Marseilles, York or Foggy Bottom(say) and that's only 140kms (90mls) away.
There in one second! That's fast!
I face this situation frequently in discussing meteoritics. A typical meteor is traveling about 50 km/s. In speaking before American audiences, and in the classroom, I find that very few people have a good concept of what this means. Converting to miles is some help, but even 30 miles/s just doesn't make an impression with most people, unless I actually frame it as you do: give a pair of cities and point out that the meteor would travel between them in a second. Most people don't make that connection themselves. But they do seem to get 115,000 mph, even though the number is large. And in giving interviews to newspapers or on TV, I'm always asked what km/s is in miles per hour.

The reality is, most people are generally more comfortable with familiar units, even when the value itself is an unusual one. And that's why I think the best approach is to use both.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

User avatar
bystander
Apathetic Retiree
Posts: 20664
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

Inappropriate topc headings

Post by bystander » Tue Sep 25, 2012 2:29 pm

I think people making complaints should use appropriate verbiage. I'm not even sure unappropriate is even a word, although unappropriated is.
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
— Garrison Keillor

jiri
Asternaut
Posts: 3
Joined: Tue Sep 25, 2012 2:43 am
Location: Neckargemuend (near Heidelberg), Germany and Praha, Czech Republic

Re: Inappropriate topc headings

Post by jiri » Tue Sep 25, 2012 2:50 pm

bystander wrote:I think people making complaints should use appropriate verbiage. I'm not even sure unappropriate is even a word, although unappropriated is.
Thank you for improving my English, perhaps better would be "unsuitable". I am sorry that my suggestion could be understood as a complaint - that was not my intention.
Jiri

User avatar
JohnD
Tea Time, Guv! Cheerio!
Posts: 1377
Joined: Wed Feb 16, 2005 2:11 pm
Location: Lancaster, England

Re: Unappropriate velocity unit - km/h

Post by JohnD » Tue Sep 25, 2012 5:22 pm

Chris has lectured to more people that I have!
If he finds that people are easier with the kms or miles per hour, than km/m per sec, then he's right!

So lets have both?

geckzilla may be interested to know that in the UK, the metric system has been taught in schools for a generation and we use it for weight, of foods for instance, and our weather forecasts give temperatures in Celcius, but not for distance. It's still miles between towns, for speed limits, and for wind speed!
Bizarre, I know, but that's British compromise for you!

John

User avatar
neufer
Vacationer at Tralfamadore
Posts: 18066
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: Unappropriate velocity unit - km/h

Post by neufer » Tue Sep 25, 2012 9:06 pm

owlice wrote:
neufer wrote:
Multiple zeros should be avoided whenever possible regardless of the method used.
Disagree. Multiple zeroes are okay in many contexts, including this one.
:really?: I have an odd urge to throw oodles of ooids or oolites oozing oily oleo over at an old owl.
Last edited by neufer on Wed Sep 26, 2012 2:07 am, edited 1 time in total.
Art Neuendorffer

User avatar
Beyond
500 Gigaderps
Posts: 6889
Joined: Tue Aug 04, 2009 11:09 am
Location: BEYONDER LAND

Re: Unappropriate velocity unit - km/h

Post by Beyond » Wed Sep 26, 2012 1:28 am

Uh-Oh, i hear the sharpening of pointy-grabby things.
To find the Truth, you must go Beyond.