solstice question

[gforcepdx]

Hello to all, this is my first post

 

Yesterday (3/20/10) was the solstice, which gives us equal parts light and dark, thus marking the beginning of spring in the northern hemisphere. When however I went to view an annual chart for my location (Portland, Oregon), the sunrise was listed at 7:14AM and sunset at 7:23PM. This chart lists march 17th as having a sunrise and sunset at 7:19 AM and PM... So why the discrepancy?

 

Also,

 

While looking for an answer to the question above, I found many references to the earth having a tilted axis. And while there is an abundance of information about the effects of this tilt on our environment, there is no information about its causation. Our planet spins because of the forces exerted upon it as as we travel around the sun, but why is our axis not at a right angle to this plane of this rotation ?

[StringJunky]

Hello to all, this is my first post

 

Yesterday (3/20/10) was the solstice, which gives us equal parts light and dark, thus marking the beginning of spring in the northern hemisphere. When however I went to view an annual chart for my location (Portland, Oregon), the sunrise was listed at 7:14AM and sunset at 7:23PM. This chart lists march 17th as having a sunrise and sunset at 7:19 AM and PM... So why the discrepancy?

 

Also,

 

While looking for an answer to the question above, I found many references to the earth having a tilted axis. And while there is an abundance of information about the effects of this tilt on our environment, there is no information about its causation. Our planet spins because of the forces exerted upon it as as we travel around the sun, but why is our axis not at a right angle to this plane of this rotation ?

 

The correct term for this event is the Spring Equinox, which is when there is equal day and night...the Solstice is when the day is at its longest (mid summer) or when the night is at its longest mid winter)

 

I think I read somewhere it was hypothesised that the odd angle of the Earth's rotation was caused by a very large Mars-sized object glancing off the surface of the very young Earth causing it to spin at that angle of axis.

 

Don't know the answer for the apparent discrepancy in times.

[gforcepdx]

your right about that... great first post:doh: I was pretty tired I guess

[OSHMUNNIES]

The equinox would be on the 17th (7:19 am & 7:19 pm) if the Earth's axial rotation period were exactly 24 hours. Because the day is actually something like 23.93 hours (86,148 seconds instead of 86,400 seconds), when doing the math, you have to acknowledge that the end of the day is at 23:56:48.

[tomgwyther]

Just pulled this from timeanddate.com

I only live a little way from the Greenwich meridian (The zero line)

It seems the nearest I got to Equal Night (Equinox) was on The 18th. hmmmm.

 

13 Mar 2010 06:19 18:01 11h 41m 49s + 3m 58s 12:10 35.7° 148.693

14 Mar 2010 06:17 18:03 11h 45m 48s + 3m 58s 12:09 36.1° 148.734

15 Mar 2010 06:15 18:04 11h 49m 46s + 3m 58s 12:09 36.5° 148.774

16 Mar 2010 06:12 18:06 11h 53m 44s + 3m 58s 12:09 36.9° 148.815

17 Mar 2010 06:10 18:08 11h 57m 42s + 3m 58s 12:08 37.3° 148.856

18 Mar 2010 06:08 18:09 12h 01m 41s + 3m 58s 12:08 37.7° 148.897

19 Mar 2010 06:06 18:11 12h 05m 39s + 3m 58s 12:08 38.1° 148.937

20 Mar 2010 06:03 18:13 12h 09m 37s + 3m 58s 12:08 38.5° 148.978

21 Mar 2010 06:01 18:15 12h 13m 36s + 3m 58s 12:07 38.8° 149.019

22 Mar 2010 05:59 18:16 12h 17m 34s + 3m 58s 12:07 39.2° 149.060

23 Mar 2010 05:56 18:18 12h 21m 32s + 3m 57s 12:07 39.6° 149.101

24 Mar 2010 05:54 18:20 12h 25m 30s + 3m 58s 12:06 40.0° 149.143

 

If you were in Moscow on the 18th, you'd have been treated to nearly exactly 12 hours of sunlight and 12 of darkness (With the difference of a few seconds)