Page 1 of 1 [ 8 posts ] 

KevinLA
Veteran
Veteran

User avatar

Joined: Nov 06, 2007
Posts: 650
Location: United States

27 Aug 2010, 11:42 am

When does time start when turning over a sand dial? Is it when the first grain of sand hits the bottom or is when the first grain leaves the top cylinder?



Last edited by KevinLA on 27 Aug 2010, 5:45 pm, edited 1 time in total.

TallyMan
Forum Moderator
Forum Moderator

User avatar

Joined: Mar 30, 2008
Posts: 41833

27 Aug 2010, 12:38 pm

I would image that the error inherent in such timing devices is substantially larger than the time it takes for the first grain of sand to fall, thus the question becomes irrelevant in practice.

I wonder what the variation in say a "5 minute" timer is on successive turns? I'd guess in the region of a few seconds. They are also likely temperature dependent as the hole is likely to expand slightly with warmer temperatures.

Would there be any deviation in the time taken for the sand to fall one way through the hole than the other due to any imperfections in the shape of the hole, or would this cancel out?


_________________
I've left WP indefinitely.


ruveyn
Veteran
Veteran

User avatar

Joined: Sep 21, 2008
Posts: 31578
Location: New Jersey

27 Aug 2010, 3:05 pm

KevinLA wrote:
When does time start when turning over a san dial? Is it when the first grain of sand hits the bottom or is when the first grain leaves the top cylinder?


It is a matter of convention. There is no Right Answer.

ruveyn



Mdyar
Veteran
Veteran

User avatar

Joined: May 28, 2009
Posts: 2514

27 Aug 2010, 7:33 pm

KevinLA wrote:
When does time start when turning over a sand dial? Is it when the first grain of sand hits the bottom or is when the first grain leaves the top cylinder?


Not being posed in the philosophy forum, I'd say:

I suppose that the synchronizing of it with a standard timepiece would begin immediately as it was turned , and stopped as the last grain fell to a stop.
This is how it would be used in actual practice.

Technically as it was turned the first grain would be in a free fall , so I vote- leaves the top cylinder.



Surya
Velociraptor
Velociraptor

User avatar

Joined: Jul 18, 2010
Posts: 437

27 Aug 2010, 8:11 pm

Mdyar wrote:

Technically as it was turned the first grain would be in a free fall , so I vote- leaves the top cylinder.


Makes sense to me. When the first one leaves, there is as you said a 'free fall' as others fall, the distance gets less, which would take less time.

This is an amazing hourglass.


Image


Quote:
Unveiled on May 1st 2004 to commemorate Hungary’s entrance in the European Union, The Time Wheel is made out of red granite, steel and bullet-proof glass and it combines one of humanity’s most primitive time measuring devices with a very precise computer. It lies in Budapest near the entrance to City Park. The sand in the hourglass flows from one side of the device to the other for an entire year and the last grains are programmed to flow exactly at midnight on New Year’s Eve. The flow is then turned manually so that it can start measuring time for another year. It takes 45 minutes for 4 people to turn it 180 degrees using metal cables.

The Time Wheel hourglass was designed by Istvan Janaki.

http://www.odditycentral.com/pics/the-time-wheel.html



Titangeek
Veteran
Veteran

User avatar

Joined: Aug 22, 2010
Posts: 7702
Location: somewhere in the vicinity of betelgeuse

31 Aug 2010, 9:43 pm

TallyMan wrote:
I would image that the error inherent in such timing devices is substantially larger than the time it takes for the first grain of sand to fall, thus the question becomes irrelevant in practice.

I wonder what the variation in say a "5 minute" timer is on successive turns? I'd guess in the region of a few seconds. They are also likely temperature dependent as the hole is likely to expand slightly with warmer temperatures.

Would there be any deviation in the time taken for the sand to fall one way through the hole than the other due to any imperfections in the shape of the hole, or would this cancel out?


Would it not also depend on the size of the sand in question?


_________________
Always be yourself, express yourself, have faith in yourself, do not go out and look for a successful personality and duplicate it.
- Bruce Lee


danandlouie
Veteran
Veteran

User avatar

Joined: Jul 27, 2010
Posts: 796
Location: rainbow bridge

31 Aug 2010, 10:59 pm

would not the state of the device with regards to vacuum have an effect.

say ACE.......i wish i had your life if you are obsessing over this!



StuartN
Veteran
Veteran

User avatar

Joined: Jan 20, 2010
Posts: 1567

01 Sep 2010, 5:08 am

KevinLA wrote:
When does time start when turning over a sand dial? Is it when the first grain of sand hits the bottom or is when the first grain leaves the top cylinder?


In movies, time begins when the base of the time-piece touches the table and ends when the last grain hits the bottom, which means the start and end point are defined by entirely different mechanisms.



Display posts from previous:  Sort by  


Page 1 of 1 [ 8 posts ] 



 Similar Topics 
Fun In the Sun and Sand

in Random Discussion

27 Oct 2007, 9:35 am

0_equals_true View the latest post

Is Sand still around?

[ Go to page: 1, 2 ]

in Politics, Philosophy, and Religion

15 Dec 2014, 2:33 am

AspieOtaku View the latest post

Sand

[ Go to page: 1, 2 ]

in Politics, Philosophy, and Religion

25 Jan 2011, 10:54 am

skafather84 View the latest post

BURNING SAND!!!!!!

in Random Discussion

19 Sep 2008, 6:34 pm

Relicanth7 View the latest post



You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum
Jump to: