Understanding Changes in Earth's Rotation and Revolution Speeds

[sanidhay]

what does this mean that every year the time of daylight in increasing on a specific date? is the speed of Earth's rotation increasing or the speed of its revolution is increasing..please help me out...

 

[nasu]

Are you talking about the "daylight saving" programs?

 

[mathman]

what does this mean that every year the time of daylight in increasing on a specific date? is the speed of Earth's rotation increasing or the speed of its revolution is increasing..please help me out...

The main reason for seasonal variation of the time of daylight is the direction of the Earth's axis relative to the sun. On Dec. 21 the north pole is tilted as far as possible away from the sun and on June 21 the north pole is pointed as close as possible toward the sun. Net result from Dec 21 to June 21 daylight increases in the northern hemisphere and decreases in the rest of the year. In the southern hemisphere the daylight variation is reversed.

 

[sanidhay]

The main reason for seasonal variation of the time of daylight is the direction of the Earth's axis relative to the sun. On Dec. 21 the north pole is tilted as far as possible away from the sun and on June 21 the north pole is pointed as close as possible toward the sun. Net result from Dec 21 to June 21 daylight increases in the northern hemisphere and decreases in the rest of the year. In the southern hemisphere the daylight variation is reversed.

But can it be possible that the daylight will be of 23 hours and 9 minutes?
if yes then what does it means?
suppose on a given day after every year the time of daylight increase by 1 minute...then what does this mean?

 

[sanidhay]

Are you talking about the "daylight saving" programs?

no i m not talking about them

 

[russ_watters]

But can it be possible that the daylight will be of 23 hours and 9 minutes?
if yes then what does it means?
suppose on a given day after every year the time of daylight increase by 1 minute...then what does this mean?

It doesn't - so what do you mean?

 

[sophiecentaur]

Look at this animation and also google "day length and Earth tilt".
Day length is a matter of what proportion of daily rotation gets sunlight on a particular place on the globe. If you're on the Pole, during the summer, there is sunlight all day and in winter it's dark all day. Nearer the equator, the light / dark is a pretty even split at all times.
The Earth tilts the same way (in absolute terms) wherever it is around its yearly orbit - see the animation then figure it out.

 

[nasu]

no i m not talking about them

Then it is not true that the "the time of daylight in increasing on a specific date".
The time of daylight increases and decreases continuously and periodically during the year.
There is no specific date when is increasing. There are specific dates corresponding to the minima and maxima of the cycle (the solstices).
Still not clear what are you talking about.

 

[sophiecentaur]

It increases / decreases by a specific amount on every 'specific day'.
I think we are just having a language / understanding problem.

 

[sanidhay]

Look at this animation and also google "day length and Earth tilt".
Day length is a matter of what proportion of daily rotation gets sunlight on a particular place on the globe. If you're on the Pole, during the summer, there is sunlight all day and in winter it's dark all day. Nearer the equator, the light / dark is a pretty even split at all times.
The Earth tilts the same way (in absolute terms) wherever it is around its yearly orbit - see the animation then figure it out.

let me give the example of what m talking about..
like on 21 December 92 AD the time of sunlight was 10 hours 18 minutes (used an online calculator)
on 21 December 1800 AD the time of sunlight was 10 hours and 19 minutes...
on 21 December 2800 AD the time of sunlight will be 10 hours and 20 minutes...
through all these years the time is increasing by seconds and minutes and after some 1000 years it will increase by hours...
i want to know that why is it happening?
got it now?

 

[sanidhay]

Then it is not true that the "the time of daylight in increasing on a specific date".
The time of daylight increases and decreases continuously and periodically during the year.
There is no specific date when is increasing. There are specific dates corresponding to the minima and maxima of the cycle (the solstices).
Still not clear what are you talking about.

let me give the example of what m talking about..
like on 21 December 92 AD the time of sunlight was 10 hours 18 minutes (used an online calculator)
on 21 December 1800 AD the time of sunlight was 10 hours and 19 minutes...
on 21 December 2800 AD the time of sunlight will be 10 hours and 20 minutes...
through all these years the time is increasing by seconds and minutes and after some 1000 years it will increase by hours...
i want to know that why is it happening?
got it now?

 

[sanidhay]

It doesn't - so what do you mean?

now got it?

 

[sophiecentaur]

Did you not notice that it is DECREASING in the Autumn?

 

[sanidhay]

Did you not notice that it is DECREASING in the Autumn?

whatever it does but on December 21 56994 the sunlight will be of 23 hours and 6 mins...
what say about this?

 

[sanidhay]

and not on the poles..it will be on equator

 

[sophiecentaur]

whatever it does but on December 21 56994 the sunlight will be of 23 hours and 6 mins...
what say about this?

Did you READ this or CALCULATE it? What info did you use?

 

[sanidhay]

Did you READ this or CALCULATE it? What info did you use?

i calculated this...
i used a tool..
wolfram mathematica 8

http://wolframalpha.com

 

[nasu]

whatever it does but on December 21 56994 the sunlight will be of 23 hours and 6 mins...
what say about this?

And what will be the length of the night on the same day?

The explanation for your observation will depend on what that software is doing. I mean, first has to be established if this is a real fact or just something wrong in the software.
Predicting the length of the day for long periods and taking into account all the perturbative factors is not an easy task. It may be just first order approximation, which works well for 100 years but breaks down for many thousands.

Second, picking up a specific day (September 21) is not the best choice. The length of the day depends on how far from the solstice you are. The solstice does not "happen" always on September 21.

 

[sanidhay]

And what will be the length of the night on the same day?

The explanation for your observation will depend on what that software is doing. I mean, first has to be established if this is a real fact or just something wrong in the software.
Predicting the length of the day for long periods and taking into account all the perturbative factors is not an easy task. It may be just first order approximation, which works well for 100 years but breaks down for many thousands.

Second, picking up a specific day (September 21) is not the best choice. The length of the day depends on how far from the solstice you are. The solstice does not "happen" always on September 21.

i used 21 december because it has the shortest period of daylight...and wolframalpha is a software from creators of google...
and yeah i believe that the first explanation might be right..
but if it is correct then does it mean that the orbit of Earth is increasing...or the sun is expanding or contracting?

 

[nasu]

You mean Wolfram alpha has a built in function to calculate the length of the day?

When I ask about the software I mean a specific application, based on some model. Not the computer program or computation environment used to run the application.

 

[sanidhay]

You mean Wolfram alpha has a built in function to calculate the length of the day?

When I ask about the software I mean a specific application, based on some model. Not the computer program or computation environment used to run the application.

i don't know ne thing about that...
but just assume that it is happening...
i just want to know that if it is happening thn what is the factor responsible for that?

 

[nasu]

i used 21 december because it has the shortest period of daylight...

Not necessarily. The solstice may occur in the period 20-22 December.

 

[sanidhay]

Not necessarily. The solstice may occur in the period 20-22 December.

and tht includes 21 too

 

[sophiecentaur]

You are not answering our question. Where does your DATA come from? (Not Wolfram, I suggest)

 

[sanidhay]

You are not answering our question. Where does your DATA come from? (Not Wolfram, I suggest)

the data is taken from wolframalpha only...go and check it out
December 21 56994

 

[DaveC426913]

the data is taken from wolframalpha only...go and check it out
December 21 56994

There's nothing on that page about length of day.

 

[sophiecentaur]

whatever it does but on December 21 56994 the sunlight will be of 23 hours and 6 mins...
what say about this?

This last statement of yours reduces the whole thread to a joke. What sort of algorithm do you think they are using and are you surprised that it has gone adrift by 56994?

On a serious note, are you aware that the leap year thing and the non circularity of the Earth's orbit make the days, year on year, far from equal. If you can be bothered, look at the variation over 4 year cycles for a specific day, also, look at the asymmetry of Solar Noon and GMT Noon over the annual cycle.

 

[nasu]

i don't know ne thing about that...
but just assume that it is happening...
i just want to know that if it is happening thn what is the factor responsible for that?

Well, this is hardly a serious approach. If you don't know how you got your data, what do you expect?
You sample three points from a periodic function and extrapolate to an interval more than 10 times larger. Expecting meaningful results is just wishful thinking.
The variations of one minute you describe (if they are real) can be due to simply looking at the wrong day.
If the solstice was on Dec 20 and you looked at Dec 21, the daytime is already a little longer.

I am not saying that there is no real effect of the length of the day (and daylight) increasing over large time periods. But I don't think your "data" have anything to do with it. At least from the way you present it so far.

 

[sophiecentaur]

sanidhay
I think you should realize that Maths is the slave of the real world - not the other way round. Every maths result needs a reality check.

 

[russ_watters]

Perhaps you are talking about the slowing of Earth's rotation? This happens due to tidal friction, but it is a very small effect. Your posts implied something bigger.