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mustangchef

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More stupid questions
« on: November 10, 2017, 02:34:32 PM »
again,  what time of the year is our planet recieving the most energy?
and    is there near zero gravity at the center of the Earth?
is the amount of water on Earth increasing ?
Thanks
« Last Edit: November 10, 2017, 03:42:04 PM by Neven »
sometimes

pikaia

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Re: curious questions
« Reply #1 on: November 10, 2017, 03:16:49 PM »
Earth is closet to the Sun at about January 3rd, so sunlight is greatest then.

Gravity is zero at the centre of the Earth. Newton proved that the gravity inside a hollow sphere is exactly zero, and you can think of the Earth as a series of concentric hollow spheres.

Water on Earth:
http://sciencenordic.com/earth-has-lost-quarter-its-water

Avalonian

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Re: curious questions
« Reply #2 on: November 10, 2017, 03:29:12 PM »
1. Northern Hemisphere winter is when the Earth is closest to the Sun. I'm not sure whether there are albedo effects that might mitigate that, but I'd thought that 3.3 % difference in proximity would mostly outweigh it. Perhaps there's a bit of a shift of the precise maximum towards late autumn, though, before the northern ice has built up?

2. Yes.

3. On Earth, or in Earth? The balance is between water added from space, water lost by photodissociation in the atmosphere, and water cycling into and out of the mantle via tectonics and volcanism. How that balance actually works out... well, I'm really not sure, but I'd guess the photodissociation and loss of hydrogen wins out. I once did some calculations on the expected initial water content of the Earth, based on a carbonaceous chrondite standard, and found that we've lost about 90% of what was originally there. Probably most of that went very early on, of course, but still.
    As for the balance between the hydrosphere/atmosphere and the mantle, that's left as an exercise for the student.  8)

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mustangchef

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Re: More stupid questions
« Reply #3 on: November 11, 2017, 08:44:05 PM »
nice . like the word photoehateever
sometimes

Martin Gisser

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Re: More stupid questions
« Reply #4 on: January 12, 2019, 09:16:26 PM »
The internets dictionaries aren't yet advanced enough to translate the wörd "bullshit" into Latin :( Any suggestion?

I arrived at bovistercus via google-translate and remembrances of heavy drinking sessions with a roman catholic theologian. (Amazing how the classical dictionaries avoid fecal vocabulary :).. But I almost failed school due to Latin.

Why would me (Mars J.P. Florifulgurator, a Latin hating DaDaist and natural philosopher) arrive at such a question?

The Late Homo S Sapiens currently stands at a crossroads of cultural-cum-biogeophysical evolution and will split into Homo Sapiens Erectus (who tries to walk his brains upright) and what some name "Homo Sapiens Trumpensis". But this is doing the paradigmatic Donald too much honour, who is not standing (pun!) on the shoulders of giants, but an astronomical pile of bullshit. So I propose Homo Sapiens Bovistercus or maybe Bovisterculinii for the whole heap. I'm not yet sure about bovis...

(And then I might plug this to Yuval Harari...)


« Last Edit: January 12, 2019, 09:42:03 PM by Martin Gisser »

Pmt111500

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Re: More stupid questions
« Reply #5 on: January 13, 2019, 04:46:48 AM »
1. Northern Hemisphere winter is when the Earth is closest to the Sun. I'm not sure whether there are albedo effects that might mitigate that, but I'd thought that 3.3 % difference in proximity would mostly outweigh it. Perhaps there's a bit of a shift of the precise maximum towards late autumn, though, before the northern ice has built up?
Southern hemisphere has more oceans which do suck up energy quite a lot more than the NH highlands that in spring are often also snowcovered, like the Arctic Ocean. So wintertime of Northern Hemisphere is still the correct answer. January-February, once most of the Antarctic sea ice has melted, would be my answer... Once Arctic goes ice free in spring the situation could change for the north points a bit longer towards the sun during the year so this could indeed be flipped around.
Quote
2. Yes.
Yes.
Quote
3. On Earth, or in Earth? The balance is between water added from space, water lost by photodissociation in the atmosphere, and water cycling into and out of the mantle via tectonics and volcanism. How that balance actually works out... well, I'm really not sure, but I'd guess the photodissociation and loss of hydrogen wins out. I once did some calculations on the expected initial water content of the Earth, based on a carbonaceous chrondite standard, and found that we've lost about 90% of what was originally there. Probably most of that went very early on, of course, but still.
    As for the balance between the hydrosphere/atmosphere and the mantle, that's left as an exercise for the student.  8)
This is a hard question and irrelevant wrt ice ages. Nevertheless the presence of ozone in the atmosphere makes a nice trap for energetic hydrogen ions in the stellar winds so I'd guess the amount of water on earth might be correlated with the amount of oxygen in the atmosphere. The amounts of this exchange are not large anyway, so melting an ice sheet will still raise the sea levels by quite a lot... Mainly guessing here though, and suggesting an astronomy-forum might be a better place to ask this.
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crandles

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Re: More stupid questions
« Reply #6 on: January 13, 2019, 05:21:50 PM »
1. Northern Hemisphere winter is when the Earth is closest to the Sun. I'm not sure whether there are albedo effects that might mitigate that, but I'd thought that 3.3 % difference in proximity would mostly outweigh it. Perhaps there's a bit of a shift of the precise maximum towards late autumn, though, before the northern ice has built up?
Southern hemisphere has more oceans which do suck up energy quite a lot more than the NH highlands that in spring are often also snowcovered, like the Arctic Ocean. So wintertime of Northern Hemisphere is still the correct answer. January-February, once most of the Antarctic sea ice has melted, would be my answer... Once Arctic goes ice free in spring the situation could change for the north points a bit longer towards the sun during the year so this could indeed be flipped around.

Partly depends on what is meant by
Quote
our planet recieving the most energy?

Is the energy received if it is reflected by clouds and/or ground? Or only if the heat energy is absorbed?

If reflected energy is "received" (even though reflected back out unaffected) then 3rd Jan date is close enough (oblate shape might mean larger cross-section area at solstices than at equinoxes? but expect this effect to be pretty small.)

If reflected energy by clouds and ground don't count, then it seems possible that a NH snow maximum in January might be time of least energy received.

Not claiming any knowledge on cloud trends so that could skew answer away from what I am suggesting for reflected energy by clouds and ground don't count, and I am not going to even attempt to venture an answer for situation if reflected energy by clouds don't count but reflected energy by ground does count other than saying it is possible cloud minimum might outweigh distance from sun effect.