The position of the earth during summer solstice?

[kingwinner]

1) How can you describe the POSITION of the earth during summer solstice (June21-22)? (Is it possible to say that the earth's position at summer solstice is such that the North Pole is tilted toward the Sun?)

 

2) Why are the sun rays more concentrated when it is striking the earth surface at a 90-degree angle than at a 30-degree angle? (I can understand that the earth surface at a 90-degree angle is CLOSER to the sun, but how come the sun rays are more concentrated?)

[Tormod]

I am not sure about #1, but #2 is because at 90 degrees the sun passes through a lot less atmosphere than at any other degrees of inclination, IIRC.

[Turtle]

1) How can you describe the POSITION of the earth during summer solstice (June21-22)? (Is it possible to say that the earth's position at summer solstice is such that the North Pole is tilted toward the Sun?)

 

Yes, this is the case.

[sergey500]

I can not answer your question, because i do not know. But i can tell you something you probabky do know, Earth is furthest from the sun in the summer and closest in the winter.

[Turtle]

... Earth is furthest from the sun in the summer and closest in the winter.

___True; these extremes in orbit occur about ten or so days after the solstices. Here is a link from the US Naval Observatory listing Earth's Seasons, Equinoxes, Solstices, Perihelion, and Aphelion 1992-2020

http://aa.usno.navy.mil/data/docs/EarthSeasons.html

;)

[Tormod]

I can not answer your question, because i do not know. But i can tell you something you probabky do know, Earth is furthest from the sun in the summer and closest in the winter.

 

On the northern hemisphere, yes. On the southern hemisphere it is the exact opposite.

[Turtle]

On the northern hemisphere, yes. On the southern hemisphere it is the exact opposite.

___Just to clarify, Tormod is refering to the poles tipping further away or closer giving us our seasons, not the perihelion/aphelion of Earth's elliptical orbit which is the same worldwide. ;)

[Qfwfq]

Is it possible to say that the earth's position at summer solstice is such that the North Pole is tilted toward the Sun?

Certainly. And this is exactly why Tormod gets the midnight sun in summer, and Eternal Darkness in winter. ;)

 

2) Why are the sun rays more concentrated when it is striking the earth surface at a 90-degree angle than at a 30-degree angle?

The main reason is that, for a horizontal surface, the radiation isn't spread over a greater area.

 

However, the main difference between the seasons due to insolation is that the duration of day and night varies. At summer solstice in the northern hemisphere you get the longest days of the year, and shortest nights. The actual weather will typically be hottest later, it takes a while for the whole place to warm up and cool down.

 

I can understand that the earth surface at a 90-degree angle is CLOSER to the sun

A drop in the ocean!

 

Earth's radius is little more than 6 thousand km, its distaance from Sun is more than 150 million. Even perihelion and aphelion make little difference, although a bit more than latitude. Earth will also be slightly closer to the sun around full moon (why?).

[kingwinner]

"Certainly. And this is exactly why Tormod gets the midnight sun in summer, and Eternal Darkness in winter."

 

How about if I am asked to describe the earth's position in autumnal equinox? I can't say that the position is such that north pole is tilted neither toward nor away from the sun because it's the same thing in vernal equinox...is there any easy way to describe its position?

 

"The main reason is that, for a horizontal surface, the radiation isn't spread over a greater area."

 

I don't quite get how the raidation isn't spreading over a greater area for a horizontal surface...the sun's rays strike the earth the same way, whether it's striking at a 90-degree angle or a 30-degree angle...why is it more concentrated when striking at 90-degree angle to earth's surface?

Thank you for explaining :rolleyes:

[Turtle]

___The Fall Equinox in the Northern Hemisphere is the Spring Equinox in the Southern Hemisphere. At this time, the axis is tilting neither toward or away from the Sun. The same is true of the other equinox.

___Take a flashlight in a darkened room (use a globe if you have one); shine the light directly down on a surface & observe the outline. Now slowly tilt the flashlight relative to the surface & note the changing outline of the beam. It is an enlightening experiment.:rolleyes:

[Turtle]

Here is an article on the front page of Spaceweather.com on the equinox:

http://www.spaceweather.com/

:rolleyes:

[Qfwfq]

Turtle's enlightening experiment is exactly what I meant.

 

How about if I am asked to describe the earth's position in autumnal equinox? I can't say that the position is such that north pole is tilted neither toward nor away from the sun because it's the same thing in vernal equinox...is there any easy way to describe its position?

Equinox is when the sun "goes through" the equatorial plane.

[coldhead]

Always liked the vernal equinox best myself.

[kingwinner]

"The main reason is that, for a horizontal surface, the radiation isn't spread over a greater area."

 

I don't quite get how the raidation isn't spreading over a greater area for a horizontal surface...the sun's rays strike the earth the same way, whether it's striking at a 90-degree angle or a 30-degree angle...why is it more concentrated when striking at 90-degree angle to earth's surface?

Thank you for explaining :rolleyes:

 

This is what I mean, the ray is still striking at one spot, whether at 90-degree or 66.5-degree angle...How can the 90-degree angle make the sun rays more concentrated?

[kingwinner]

To describe the earth's position at summer solstice, I would say that The earth's position at summer solstice is such that the North Pole is tilted toward the Sun, but at July 20, for example, the north pole is stilling tilting toward the sun...that is not an unique feature at summer solstice...this gives spaces for the teacher to deduct marks for the answer...

[Turtle]

To describe the earth's position at summer solstice, I would say that The earth's position at summer solstice is such that the North Pole is tilted toward the Sun, but at July 20, for example, the north pole is stilling tilting toward the sun...that is not an unique feature at summer solstice...this gives spaces for the teacher to deduct marks for the answer...

___Hopefully your teacher is really trying to impart knowledge to you, not find ways to screw you up. The pole IS still pointing toward the Sun in GENERAL on the 20th, but only on the Solstice is it pointing EXACTLY at the Sun.

___Did you try the flashlight experiment? See that the light at 90 degrees lights a circle, while the light at an angle lights an ellipse. The ellipse has a greater area than the circle, therefore the light is spread out more, i.e. less intense per square unit of surface lighted. :rolleyes:

[kingwinner]

Thank you Turtle, I got it, finally! :rolleyes: