The Equation of Time
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- Опубликовано: 13 сен 2012
- Sundial time and clock time often do not agree - the equation of time allows us to correct sundial time to clock time. This video explains how to use the equation of time and a basic explanation of the issues involved.
The equation of time represents the relationship between our planet's orbital geometry and time as displayed on a sundial.
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Hilo in the US: "so create your own sun dial.."
Me in the UK: "No sun here, Can you teach how to make a rain dial?"
I came here after downloading a sunset/ sunrise app and came upon this unfamiliar term. Your video is well designed, clearly explained and illustrated. Thank you for taking the time to create it! Our universe is fascinating!
That was the most intelligible explanation of the equation of time I have heard. And it was a treat to watch.
Thank you for providing this valuable education, we are lucky to have you!
Excellent Sir!
Recently I have been instructing my youngest's daughter's Father-in -Law, about the 'Equation of Time'. He was given a sundial from them, for his 70th birthday. He is a just about retired, a former H.R. man. Not very well versed in the Sciences. So I tried to explain the 'Equation of Time' in a printed 3 page note to him last week. I have today 25/Jun/2018. sent him a link to your excellent video site explanation.
Many Thanks!
Sir no one can explain this so easy like you 😢
a nice and simple explanation.thanks for posting
awesome, always nice seeing an upload from you.
love learning random science stuff :D
Of all my subscriptions, I look forward to these videos the most!
if you learn something new everyday that mean you're alive ...thanks for the great video
AMAZINGLY explained!
The angles of the hour lines on a horizontal sundial are determined by your latitude. 15 degrees works only at the poles.
These videos are so good!!
does the equation of time apply to universal equinoctial ring dials? apparently they have something to be able to set the months, and I was wondering if this was the reason they had that or if they run fast or slow like all sun dials too.
thank you you helped me understand my solar radiation homework ;) there should be more people like you
another great video. Thank you.
great vids mate!
Great explanation, thanks!
Thanks for this wonderfully clear explanation! I have a follow-up question: how did the ancient Babylonians discover the equation of time? How did they realize that the sun’s apparent motion was irregular without having a more reliable time-keeping device to compare it to?
Excellent video! Bravo.
...wow...neatly explained! thanks!
Nicely compiled information. One thing they could of added to this sundial is a site glass to find the North Star. I never had a sundial but I did make a site glass. It was 2 inch steel pipe about 24 inches long with 1/2 inch washers on the ends. I welded it together and onto a steel post at eye level. I had it pointed at the North Star. For 10 years while I lived there the North Star was always in the site glass. I moved in 1988, that thing might still be there. Before you say it will not work, you should try it.
If people are in the same area, and need some crude method to stay on schedule with each other, it's better than nothing. It can be made quickly without a protractor. I understand what you mean though, and you are right. My method is a cheap alternative to constructing a sand hour-glass or water clock of sorts...those would keep track of time without the sunlight. My method is for those who don't want to bother with the angles, especially if they have no clue or cant remember the formulas.
Fantastic post, thank you..
So cool. Thank you.
Well done. I'll check it out next time I'm in the area.
It amazes me how ancient people, knowing nothing of tilting, rotating, revolving, etc. figured out how to set the angle of the gnome, unless they just made one for each angle. Even doing that, it would take forever to find out which one was accurate.
Once nobility acquired agriculture and the power that came with it , all they had was time.
Thanks. I finally understand equation of time.
Interesting video which was new information for me. However I think it would have been even better if you had at least mentioned the difference between the real time of a longitude verses the time zone times that we use to make life easier. This also makes a (possibly large) difference between the sun dial time (which is based on the real time at that longitude) and the time zone time we use on our watches. Something for another video? Keep up the good work :-)
A really good point and one I still haven’t got my head round. Solar Noon where I live is about 20 minutes behind Solar Noon where our time zone starts. So for navigation purposes I guess we would need an adjustment for both to determine our longitude unless I am missing something.
Thanks, did not know this.
Regarding 3:24, Wayne Campbell's watch shows 9:56:02 AM Standard Time on Thursday September 13, 2012 in Pembroke, Ontario, Canada where The Portage Sundial is located. Eight years later on November 30, 2020, the Legislative Assembly of Ontario passed Bill 214 proposed by Jeremy Roberts which would establish permanent year-round observation of Daylight Saving Time. That would mean observers of apparent solar time on sundials would have to add one hour to Daylight Saving Time to convert to Standard Time.
If the earth turns faster when its closest to the sun, ie at the winter solstice, how long does it take to complete a orbit compared to june 21
Excellent video
seems clear enough from the video; but I have to ask this - If I set up a sundial, based on high noon, my time could be up to 30 minutes off clock time right? Because unless I am dead center of time zone, clock time varies from time calculated from the sun? But I know that's not equation of time - that's only due to local time being tied to a timezone, not the local position of the sun
I agree. I'm no expert but I think when setting up the sundial you would need to adjust the aim to compensate for where you are in the time zone. The aim in the eastern part of a time zone would be a little different than the aim in the western part. Pick one of those days where the equation of time is at zero, or close enough to it. Then at noon rotate the sundial until it aims right at the sun and shows the time is noon. Fix the dial in place and you have compensated for the effect you are talking about. Hopefully people who put those nice sculptural sundials in parks know to take this into account.
Dear Sir, Ton of thanks to you....I was searching for this over internet & I was not getting such illustration. I still have a doubt, what time has to do with gravity, because the speed changes w.r.t gravity ??
Yes, Earth's rotational speed varies.
Is there a vid where analemma is explained?
super kool!
I understand the processes that underly the equation of time, but I still cannot wrap my mind around why (here in Rhode Island on Dec 14, 2020) the change in the timing of the sunrise (day-to-day) is faster than the change in the timing of the sunset during the period leading up to the solstice. How/why does this happens at all, and how the trend is reversed on the other side of the winter solstice? I would appreciate any helpful feedback.
This has to do with "analemma", which is affected by shape of orbit, axial tilt & the apse line. See here analemma DOTcom
Great video. Never knew this facts.
What about southern hemisphere? Are the corrections true there?
DancePangaea equation of time is the same the world over for a given date.
It's very useful to know, but I guess those who just want to make a quick sundial can make 15 degree lines around a circle or half circle, and point the 12 oclock facing directly south, and make the indicator pointed right to the north star.
spectacular
'I did not know that.' ..is my fourth favorite thing to say.
yay!
Wow...I just learned that the equation of time can help solve any discrepancy in sundial time. If I didnt know it, I would be mistakenly complain that whoever built the sundial didnt place it right!!
Greetings from Portugal. 🇵🇹
Good explanation, however in trying to construct one in India with an Indian friend I have learnt that Equation of Time not alone can correct the time between Clock and sundial times. I 've learnt that another correction called "Longitude Correction, must be applied for places not on Standard time zones.
Please say more about this.
Can you please point me to more information.
Fair, Longitude correction accounts for standard time. Pretend you live in Boston (longitude = 71 deg). This is -5 time zone, which is centered on 75 degrees. 75-71=4 degrees. So that your local time matches up with -5 time zone, you must rotate only the dial (keeping the direction of shadow stick the same) by 4 degrees to make your solar time 16 minutes late. 15 deg = 1 hour, so 1 deg = 4 min.
There’s a free book on sundials here teaching you how they work, how to calculate them, and how to make them on any surface:
archive.org/details/in.ernet.dli.2015.151078/page/n7/mode/2up
Thanks
You must have set your watch on mean solar time of your location, rather than either eastern standard time or eastern daylight saving time.
Ah, great explanation. It lead me to question if those crossover points on the curve fell on the solstice an equinox dates, and of course they do! Looking deeper it is fascinating to see how the obliquity of the ecliptic factors in. I'll definitely have to find a way to use that phrase sometime soon. ;-)
So interesting
nice
Sience is the only fun subject of school. :)
you can’t even spell “science”
@@achoo3001 thank you for pointing out a typo i made seven years ago. i appreciate it
okay
Surely the "equation of sun time on Earth" rather than just "equation of time"? :D
The Equation of Time as shown is NOT the same across the world. It is only the same when the sundial concerned is on the standard time meridian. At other locations, you have to make an adjustment for the longitude. Where I live, at 3º west of Greenwich, 12 minutes difference, my sundial shows the same time as clocks on only two days a year.
Mike Shaw The equation of time IS the same across the world. The actual difference between mean solar time and clock time is what varies.
Time is a measurement of change, just as a mile is a measurement of distance.
WHAT!!!????
Not one mention of the relationship between Sun time and MEAN TIME????
I am shocked!
Show the mathematical
Means ñnm
Wow ive noticed that when sundial is faster than clock I am alot more alert, productive and in the flow. The change in acceleration of the sun has a major effect in our civilization.. because it changes our perception of time, essentially making us more or less efficient.
^^ Quick thought.
Time only exists
to those that run out of it / die
why is that when i check the shadows on the globe they don't match with the real world. After six months around the sun, would the shadows at 4 o clock in the afternoon be on the same side of the globe? Solar noon would only be true in the heliocentric model on the solstices. the rest of the year it would be up to 10 degrees to 23 degrees out east or west. And we have vertical gnomon sundials which are not aligned to earth's axis and they show perfect time. Could you please explain?
Earth is a flat plane
There’s a free book on sundials here teaching you how they work, how to calculate them, and how to make them in different styles:
archive.org/details/in.ernet.dli.2015.151078/page/n7/mode/2up
SCIENCE
All the comments in this video are bots saying that it’s great,
A graph is not an equation! Show me an EQUATION: a mathematical formula for position as a function of time!
The Earth is flat.