Earth's rotation and tilt
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Seasons Aren't Dictated by Closeness to Sun
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How Earth's Tilt Causes Seasons
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Are Southern Hemisphere Seasons More Severe?
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Milankovitch Cycles Precession and Obliquity
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Precession Causing Perihelion to Happen Later
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What Causes Precession and Other Orbital Changes
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Apsidal Precession (Perihelion Precession) and Milankovitch Cycles
Are Southern Hemisphere Seasons More Severe? Are Southern Hemisphere seasons more severe because of the eccentricity in Earth's orbit?
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- in the previous video
- we have already talked about the idea that there are times of earth orbit
- when it is closer to the sun
- and when it is further from the sun
- when it is closer to the sun
- let's say this is the times of the earth when it is closer to the sun
- this is the perihelion.. perihelion.. perihelion..
- and when it furtherest from the sun
- and I'm exaggerating the difference
- this is aphelion.. this is the aphelion in our orbit.
- when we are furthest from the sun.. maybe our orbit looks something like this
- so maybe our orbit looks something...
- so maybe our orbit looks something like this over here
- and what i point our in the first video we discussed is that
- this is not the cause of the season
- even-though we are 3% closer.. right now
- when are orbited... will see in the future video..
- that the difference or the eccentricity or how ellecptical
- the orbit is
- does change over time
- how much it deviates from being circular
- that's how.. that one way to think about eccentricity
- that does change over time
- right now
- when we we are closest to the sun
- we are 3% closer than we are furthest from the sun
- 3% closer than at aphelion
- and we point out in the first video that we discussed
- that this is not the cause of the seasons
- and in particular
- perliion where we are closest to the sun
- where we actually have the most radiation from the sun
- that's actually when we have the northern hemisphere
- when we have the northern hemisphere winter
- so this occurs right over here.. this occurs in January
- this occurs in January.. aphelion occurs in July.. occurs in July
- now based on this, this might lead to an interesting question
- because.. so let's think about January.. let's think about January
- when we are perhelion
- and let's think about July.. let's think about July.. we are in aphelion
- let me draw a quick globe right over here
- and let's make that the equator
- and I'll write that in both the situations.. in both the situations
- so in January is obviously when we have the northern hemisphere's winters are cold
- painted in blue right over here..
- it is winter
- and July it's when we have northern hemisphere's summer
- or the southern hemisphere's winter.. so then we have winter.. winter during July.
- in the southern hemisphere
- let's me put summer in a more summery color. i guess that orange is a pretty good color.. that's not orange..
- hers' orange.. alright..
- that's orange and that's orange.. so these are summer..
- summer
- so that's the summer in southern hemisphere
- which occurs during the winter in northern hemisphere
- and vice versa
- summer in the northern hemisphere occurs during winter in the southern hemisphere
- and so the question might be rising in your head
- and i did see a few comments in that first video asking this question
- and it's a good one
- and if we are closer.. if we are closer to the sun in January
- or we are really closest to the sun in January
- this is the perihelion right over here
- and so we are getting more solar radiation in January
- does that moderate the winter
- so does that moderate the winter..
- in the northern hemisphere
- or i guess another way to think about it..
- does it make summer in the southern hemisphere when we are closer to the sun
- does it make it more extreme
- does it make it more extreme or hotter and vice versa
- in July, when we are
- when we are furthest from the sun
- does that moderate the northern hemisphere winter
- because it is hot out there
- but hey it's little bit further from the sun
- and does that make the southern hemisphere winter colder
- so once again does it make this more extreme
- because it's already winter and we are further from the sun
- so maybe we are also getting less radiation
- and there's a couple of way to think about this
- 1 -- it is true that when we are further, we are getting a little bit less radiation
- from the sun or we are getting heated up a little bit less
- but the one reality is that the southern hemisphere climate as a whole
- is not more extreme despite getting heated up
- getting more solar energy in the summer
- and getting less solar energy in the winter
- and the reason why this is not an extreme
- we draw the equator here.. just that we can separate our hemispheres
- the main reason it is believed
- that it is not more extreme.. it is that the southern hemisphere has a lot more water in it
- so just if you look at the surface of the southern hemisphere you are looking at a lot more water
- than the surface of the northern hemisphere
- this is of course the locator projection
- this distorts things so that the things near the pole
- gets really kind of built up to look really huge even though they really aren't that big..
- Greenland really isn't larger than south america
- it just spreads the mouth so that you can kind of
- so that you can... flat the map to speak...
- so the southern hemisphere has more water
- as you may have learned in chemistry class
- water has the highest specific heat
- highest specific energy.. it takes more energy, more heat to raise water a degree
- than it does takes to raise land a degree
- and so water can absorb more energy
- or when there is less energy, water will release more energy
- without droping as much of a temperature
- so water has a moderating influence
- water has a moderating influence on the climate
- so eventhough summers in the southern hemisphere
- actually are getting more radiations than the summers in the northern hemisphere
- that's moderating on the actual temperature.. because the water is believed to absorb
- more of that heat without changing the temperature as dramatically
- now with that said, it is true
- that in general Antarctica is colder.. Antarctica is colder.. it is than the north pole
- but the main reason why antartica is colder besides the fact
- that it is in land.. as suppose to antartica being...
- ...as suppose to the north pole being the centre of the artic ocean
- is that it is actually a huge.. very high altitude of ice sheet
- and so for the altitude for most of the Antarctica is around 8000 feet
- so it's like an alphine altitude
- so the main reason why it's colder is
- you know it's possibly being further away from the sun
- and winter might play some role there
- but the main reason why it's colder is that it's at a much higher altitude
- and it's some degree insulated from the water
- or I guess you could say it's on the land
- so especially during the long winter it's going to get that much colder
- but i'll leave you there and
- and to some degree this is the other aspect of it
- during the summers... you know.. all of this stuff is super complicated
- so you can.. you can just drop one rule of thumb and say this it the reason..
- these are all are influencers
- is that if you have a large super-large ice shield sheet
- it's also more likely to reflect more of the energy
- because it's white as suppose to a darker color like the ocean or the land
- so you can think about all of those factors but the general answer is -- it's a good question
- but overall the climate in the southern hemisphere (actually it has to be northern hemisphere) is
- not more extreme than the climate in the southern hemisphere
Be specific, and indicate a time in the video:
At 5:31, how is the moon large enough to block the sun? Isn't the sun way larger?
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