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Why does Earth's tilt produce summers and winters?

Why does Earth's tilt produce summers and winters? - Physics Forum

Why does Earth's tilt produce summers and winters? - Physics Forum. Discuss and ask physics questions, kinematics and other physics problems.


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  #21  
Old 11-02-2006, 07:38 PM
dlzc
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Default Why are poles colder than the Equator?

Dear Ajanta:

Ajanta wrote:
....

Basic heat transfer.
Insolation from the Sun is one factor. (Heat in.)

Convection, evaporation, reflection, and radiation to the environment
are the ways a body can lose heat. These all require a temperature
difference between the body and the "environment".

The poles are cooler than the equator... at least on Earth.


Without an atmosphere, yes.


You have already been told that incident radiation on the "environment"
is a function of the angle of incidence. Whether or not you "get
it"...

You have a longer path length through air to go along with the angle of
incidence, which tends to decrease solar radiation intensity still
further. Then you have a 24 hour rotation, that commonly removes all
direct solar heating once a day. Then you have varying amounts of air
currents, relative humidity, and local terrain to provide enhanced or
retarded cooling capacity.

David A. Smith

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  #22  
Old 11-02-2006, 11:11 PM
bonkers
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Default Why are poles colder than the Equator?


Ajanta wrote:


It is as much due to the distance as it is the sunlight reflecting
off the atmosphere. Think of the atmosphere like a peice of glass. When
you shine a light through it at a perpendicular angle the little of the
light is reflected. The more you tilt the glass the more reflective it
becomes. Therefore the more light (so more heat) is reflected off the
atmosphere.

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  #23  
Old 11-03-2006, 02:54 AM
Nathan Smith
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Default Why does Earth's tilt produce summers and winters?

Sam Wormley wrote:



What scientific evidence?

NPS
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  #24  
Old 11-03-2006, 03:11 AM
N:dlzc D:aol T:com \(dlzc\)
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Default Why does Earth's tilt produce summers and winters?

Dear Nathan Smith:

"Nathan Smith" <[Only registered users see links. ]> wrote in message
news:%by2h.678$[Only registered users see links. ].com...

[Only registered users see links. ]
[Only registered users see links. ]
[Only registered users see links. ]
.... about halfway down the page. With links to:
[Only registered users see links. ]
[Only registered users see links. ]
[Only registered users see links. ]

And you are probably aware of a little over 2.2 billion years of
"tidal rhythmites" data that shows the Moon slowly and (more or
less) montonically receding from the Earth.

David A. Smith


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  #25  
Old 11-03-2006, 04:42 AM
Sam Wormley
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Default Why does Earth's tilt produce summers and winters?

Nathan Smith wrote:

See: [Only registered users see links. ]
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  #26  
Old 11-03-2006, 07:58 AM
jmorriss@idirect.com
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Default Why are poles colder than the Equator?


dlzc wrote:

Uh... What happens to the solat energy that disappears in the longer
atmospheric path? Doesn't it just contribute to atmospheric heating
within at most 200 km or so?

The ice-cube point is a valid one. Ignoring atmospheric absorbtion, a
spherical absorber (a black ball) on the earth will receive the same
solar energy each second from the sun , no matter how high the sun is
above the horizon. What must be included is the blocking effect of
<that> black ball on all the <other> surrounding black balls. (And the
length of daylight)

As a previous poster neatly observed, the sunlight on your back stays
the same, what changes is the length and thus the size of your shadow,
the area you are depriving of <its> solar energy...

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  #27  
Old 11-03-2006, 08:10 AM
jmorriss@idirect.com
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Default Why are poles colder than the Equator?


[Only registered users see links. ] wrote:
..
Oops... Make that at most 1200 km or so...

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  #28  
Old 11-03-2006, 09:47 AM
Randy Poe
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Default Why are poles colder than the Equator?


[Only registered users see links. ] wrote:

I think this is a valid point. But I don't think heat deposited in
the atmosphere is the main contributor to solar heating of the
earth. I believe the surface, particularly the oceans, is where
most heat is deposited.


Yes, but the energy per unit area of SURFACE decreases
as the sun gets lower in the sky, and that will affect the local
heating of the ground and the local air temperature.

Even on a daily basis, mornings and evenings are colder than
midday. That's an indicator of the importance of the sun's
position on temperature. The fact that there's a time lag
(the hottest time is not at noon) is due to the fact that the
ground takes some time to warm up and reradiate.

Now here's another question: what's the difference between
earth and moon in temperature extremes? Why does the moon
get so cold when the sun is not shining on it? Shouldn't the
earth's poles get as cold as the moon's dark regions, after
six months without solar radiation?

The best explanation I can think of is that the atmosphere
of earth provides enough transport of heat to make the
difference.

- Randy

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  #29  
Old 11-03-2006, 10:44 AM
Sue...
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Default Why are poles colder than the Equator?

The Chief Instigator wrote:

Indeed... Maximum radiation of the ground occurs when the path
through the atmosphere is shortest. (The sun is directly overhead
or 90 degrees to the surface). Above and below the tropics the sun
is never directly overhead and the departure from the optimal 90
degree angle increases with proximity to the poles.

Sue...


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  #30  
Old 11-03-2006, 01:08 PM
N:dlzc D:aol T:com \(dlzc\)
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Default Why are poles colder than the Equator?

Dear jmorriss:

<[Only registered users see links. ]> wrote in message
news:1162540705.118308.237980@i42g2000cwa.googlegr oups.com...

It does heat the air... just not all near you. Also, some is
scattered, to find another destination.


This does not really help the OP, just as his "ice cubes" don't
help him. Does every point on your "black ball" have the same
insolation? If it did not conduct heat well, would every point
be the same temperature?


One can freeze ice near the equator by isolating the water from
the environment, and radiating its heat to the "sink" provided by
the CMBR (if it is a low humidity night).

One can cook food with a solar oven near the Arctic circle in
summer.

But this does not address the OP's question. Look at the title.
The poles are not colder because some other place on Earth is
warmer.

David A. Smith


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