PDA

View Full Version : Astronomy Shadow Stick Coursework



pastaman
2009-Apr-11, 02:10 PM
Hi, I am completing a section of my astronomy GCSE coursework where i have to make a shadow stick observation which i have done and then work out the "LOCAL NOON" and the "OBSERVER'S LONGITUDE". Does anyone have any idea how to do this? I think the local noon is the shortest shadow time (on my observation it was 13:20).
Thanks!!:confused:

grant hutchison
2009-Apr-11, 04:30 PM
Welcome to BAUT. :)
We've had this one before.
See here (http://www.bautforum.com/astronomy/72647-shadow-stick-investigation.html).

Grant Hutchison

Jeff Root
2009-Apr-11, 06:53 PM
I gather that in this exercise, in addition to observing the length of a
shadow, the local standard (or daylight savings) time is also observed.
Is that correct? Are there other 'givens' or 'knowns'? What level of
accuracy is expected?

-- Jeff, in Minneapolis

grant hutchison
2009-Apr-11, 08:32 PM
I gather that in this exercise, in addition to observing the length of a
shadow, the local standard (or daylight savings) time is also observed.
Is that correct? Are there other 'givens' or 'knowns'? What level of
accuracy is expected?If the student is in region that observes daylight saving time (why the plural in your post?) then we'd need to acknowledge that fact, since the observer's longitude is part of the problem. Pastaman hasn't told us where he comes from, but there aren't many parts of the globe that set GCSE exams (an English school qualification) but don't observe daylight saving time.
I'd also assume that the Equation of Time might feature in the required calculation (as raised in the OP of the thread to which I linked).

Grant Hutchison

a1call
2009-Apr-12, 03:07 AM
(why the plural in your post?)

It is used more commonly in plural form even though it is probably not proper:

Compared searches (http://www.google.com/insights/search/#q=daylight%20saving%20time%2Cdaylight%20savings%2 0time&cmpt=q)

Much more common in the States.

Jeff Root
2009-Apr-12, 04:09 AM
I think I may have learned the plural from hearing it, rather than reading it.

On the other hand, I learned the word "physician" from reading it. So the
first time I tried to use it, at age ten, I pronounced it "fizz-IK-ee-en".
The adults thought it was funny.

I have a friend who grew up elsewhere in the USA (I think he was born in
Georgia, but I don't know where he spent his childhood). He has only one
regional idiom that stands out: Instead of saying, "All you have to do is...",
he says, "All's you have to do is..."

-- Jeff, in Minneapolis

grant hutchison
2009-Apr-12, 02:16 PM
It is used more commonly in plural form even though it is probably not proper:

Compared searches (http://www.google.com/insights/search/#q=daylight%20saving%20time%2Cdaylight%20savings%2 0time&cmpt=q)

Much more common in the States.Yes, my question really arises from that observation: I'm curious why US English speakers say "daylight savings", while acknowledging that it is "probably not proper".
For instance, David Prerau's book Seize the Daylight: The Curious and Contentious Story of Daylight Saving Time, says only that:
"Daylight saving time" is considered to be the correct term for this clock-altering process, since it refers to a time for saving daylight, but "daylight savings time" is also commonly used.
I was wondering if there was some acknowledged reason for the mutation of the phrase in American English, or if it's just one of those mysterious linguistic events, like the substitution of "I could care less" for "I couldn't care less".

Grant Hutchison

a1call
2009-Apr-12, 04:43 PM
I can't speak for everyone, but here in Canada most people are 1st introduced to the term through the media which keep reminding them to set their clocks forward every year. They (the media) generally use the plural form and often emphasize the "zzz" sound in savings.
See this top story reference (http://www.ctv.ca/servlet/ArticleNews/story/CTVNews/20081101/EDM_clocks_back_081101/20081101/) in CTV, Canada's largest private broadcaster.

You can also see many references of both forms (http://www.cbc.ca/search/cbc?q=daylight+savings+time) in the CBC, Canada's national public broadcaster site.

It is probably the case of one announcer mispronouncing it years ago at the point of 1st exposure in a national level.

1st impressions are hard to alter.

Another factor for the prevalence of the plural form might be that if someone hears both forms at different occasions he/she is likely to attribute the singular form to a mispronunciation/mishearing of the plural form as the "s" in savings is sometimes hard to pronounce/hear.

Jeff Root
2009-Apr-12, 05:41 PM
Although there is no apparent need for the plural, it isn't obviously wrong,
so when I hear it used I have no reason not to use it that way myself.

Curious that the plural might be dominant in Canada. The Twin Cities really
is not at all closely-linked to anything Canadian. We certainly can't pick
up any Canadian TV signals here.

-- Jeff, in Minneapolis

a1call
2009-Apr-12, 06:15 PM
It's likely that Canadian broadcasters are following the States' lead.

Regarding the silence/tongue-twister-ness of the 2nd "s" in savings hover your pointer over the word here (http://www.howjsay.com/index.php?word=savings&submit=Submit). If you have no problem hearing the last "s" try lowering the volume of your computer.

Regarding the properness if the plural, IMHO it's not that it does not make any sense as the the time saved is over many days/months. It is more a matter of the person coining the term using the singular form:

...the savings by analogy to savings account.[99] Willett's 1907 proposal used the term daylight saving...

Source (http://en.wikipedia.org/wiki/Daylight_saving_time#Terminology)

grant hutchison
2009-Apr-12, 06:32 PM
Regarding the properness if the plural, IMHO it's not that it does not make any sense as the the time saved is over many days/months. It is more a matter of the person coining the term used the singular form:The UK has blithely ignored Willett's original for many years, using the term "summer time" instead.
But the USA still officially retains the (singular) term "Daylight Saving Time". It seems even the US Congress is getting itself into a tangle with this one: the Energy Policy Act Of 2005 (http://www.epa.gov/oust/fedlaws/publ_109-058.pdf) (3151 KB pdf) revised the law with regard to "Daylight Saving Time" in Section 110, which is entitled "Daylight Savings".

Perhaps the root cause is that "daylight-saving" and "daylight savings" are both rather nonsensical expressions in this context, so there's no real barrier to usage drift.

Grant Hutchison

mugaliens
2009-Apr-13, 12:44 AM
...or if it's just one of those mysterious linguistic events, like the substitution of "I could care less" for "I couldn't care less".

Grant Hutchison

Well, "I could care less" means that there is additional capacity in one's ability to care less. "I couldn't care less" means there is no such additional capacity. Thus, a comment like "You care about global warming, but I could care less about the plight of the snowy egret" means the speaker cares less about egrets than global warming. Meanwhile, "I couldn't care less about global warming" means that global warming is on the bottom of the speakers care list.

I'll be posting my response to the previous shadow stick thread, here (http://www.bautforum.com/astronomy/72647-shadow-stick-investigation.html).

loglo
2009-Apr-13, 10:41 AM
I think savings is more common because saving sounds like a verb and "savings" sounds more like a noun. The latter is more commonly used in Australia too.

grant hutchison
2009-Apr-13, 11:13 AM
I think savings is more common because saving sounds like a verb and "savings" sounds more like a noun. The latter is more commonly used in Australia too.Yes, it's a shift in the grammar of the phrase. In "daylight saving time", "saving" is a verb participle modifying the noun "daylight"; in "daylight savings time", "savings" is the noun modified by the noun "daylight".
It's like the difference between a "life saving" intervention and one's "life savings". The phrase "life saving" needs another noun to come after it; "life savings" doesn't, though it can accommodate one.

Grant Hutchison

Jeff Root
2009-Apr-13, 05:45 PM
in "daylight savings time", "savings" is the noun modified by the
noun "daylight".
That is how I have unconciously thought of it.

pastaman,

I hope we haven't discouraged you from further posting by taking
your thread so far off topic. If you have additional questions, please
let us know. If we helped or if you succeeded without our help, that
would be nice to know, too.

-- Jeff, in Minneapolis

grant hutchison
2009-Apr-13, 05:53 PM
I hope we haven't discouraged you from further posting by taking
your thread so far off topic. If you have additional questions, please
let us know. If we helped or if you succeeded without our help, that
would be nice to know, too.Indeed. What Jeff said. :)

Grant Hutchison

a1call
2009-Apr-13, 06:03 PM
It's my fault more than anyone's.

pastaman
2009-Apr-14, 10:18 AM
:)Thanks for your posts, the link at the top was the most helpful. I live near London in England. We do use DST and at the moment we are in Summer time so we put the clocks forward one hour at the start of spring. I have used the equation of time to calculate the mean solar time but now need to find the latitude. The equation of time for now (when i did the experiment) is -3 minutes so i presume that makes the mean solar time 12:27 or do i have to factor in DST too?:confused:
Thanks

grant hutchison
2009-Apr-14, 03:16 PM
:)Thanks for your posts, the link at the top was the most helpful. I live near London in England. We do use DST and at the moment we are in Summer time so we put the clocks forward one hour at the start of spring.So GMT, the standard time for your longitude, is an hour earlier than your clock is currently reading.


I have used the equation of time to calculate the mean solar time but now need to find the latitude.You were trying to find the longitude at the start of this thread. Which do you need, latitude or longitude?


The equation of time for now (when i did the experiment) is -3 minutes so i presume that makes the mean solar time 12:27 or do i have to factor in DST too?:confused:The Equation of Time is telling you the difference between Mean Solar Time and Apparent Solar Time. You need to be a little careful with it, because some versions subtract MST from AST, and some do the opposite. So check this carefully, be sure you understand which direction you want to go in, and whether you should be subtracting or adding to get there. It's certainly not clear to me how you could get from 13:20 in your original post to 12:27 now. Do you mean 12:17?

Grant Hutchison

pastaman
2009-Apr-15, 04:50 PM
Sorry Grant,:shifty:
So, to clear things up:

I am trying to find the LONGITUDE
I did have the shortest shadow time as 13:20. So, this would make the GMT for where i am at that point 12:20
The equation of time i was using is "CLOCK TIME = SUNDIAL TIME - EQUATION OF TIME" and so as i mentioned previously, the equation of time is -3 minutes. Now which is the MST and which is AST?

That should clear the time business up now, so all i need to do after this is find the longitude from that time.
Thanks so much for your help!:)

grant hutchison
2009-Apr-15, 05:18 PM
The equation of time i was using is "CLOCK TIME = SUNDIAL TIME - EQUATION OF TIME" and so as i mentioned previously, the equation of time is -3 minutes. Now which is the MST and which is AST?Clocks keep mean solar time (for the central longitude of your time zone). Sundials show apparent solar time (for your location).

Grant Hutchison