# Correct me on something about the sun's movement in the sky

1. Jul 4, 2007

### Mk

Would this statement be correct?

Last edited: Jul 4, 2007
2. Jul 4, 2007

### Jimmy Snyder

Exactly correct from a frame of reference that by December 22nd stops moving north and rests for three days, until December 25th when it moves approximately one degree downwards with respect to the sun.

3. Jul 4, 2007

### Bystander

d(phizenith)/dt ~ 23 ( 2pi/365.25 ) sin ( t 2pi/365.25 ) , where t = days since solstice, or t0 = solstice dates. Highest daily rate of change of zenith angle (elevation) is 1/3 degree per day, and occurs at the vernal and autumnal equinoxes.

4. Jul 4, 2007

### Integral

Staff Emeritus
As Bystander is trying to say. The Suns motion is sinusoidal, at the solstice it reaches its extreme position for the season. The rate of change is very small at these times (Summer and Winter) So the sun appears to hover briefly as it changes direction. It is not really stationary it is just moving very slowly. It then begins to accelerate, slowly initially, then as it speeds up, reaches the maximum rate of change at the Equinox. At this time the sun races past the equator but even then the rate of change begins to drop as the sun moves toward the other extreme.

5. Jul 4, 2007

### Mk

Thanks for all three of the replies, I figured it would be sinusoidal motion, and it just slowerly and slowerly moved, until it reversed it's path of acceleration. Thanks for the math, Bystander.

6. Jul 4, 2007

### DaveC426913

Look up "analemma". That is the name of the sun's figure 8 path against the sky.

7. Jul 5, 2007

### Danger

Maybe it's just because I was born a non-Terracentric, but I prefer to think that the sun just pretty much stays the same and the motion of the Earth makes it appear to move.

8. Jul 5, 2007

### neutrino

Heretic!

:tongue2:

9. Oct 22, 2009

### mplak

Hello to all!
I don't know if anyone will check this but....here is my question:

what is the sun time equation that describes sun's movement ?
I have found plots of sun's height (in degrees) (vertical axes height-horizontal sun azimuth in degrees) but I can't find it's mathematical expression...

10. Oct 22, 2009

### D H

Staff Emeritus

11. Oct 22, 2009

### BobG

12. Oct 22, 2009

### Equate

I was just about to say the same thing.

Thank you.

13. Oct 22, 2009

### DaveC426913

He's kidding.

This thread is not about what we think; it is about what we observe. We observe the movement of the sun from our rest frame.

14. Oct 22, 2009

### Equate

Thought so.

It's a big conspiracy. I could have sworn I saw the far side of the moon the other day, but no one believed me.

Oh well...