The Naked Scientists

The Naked Scientists Forum

Author Topic: Earth Axis Tilted?  (Read 5216 times)

Offline vdurbha

  • First timers
  • *
  • Posts: 4
    • View Profile
Earth Axis Tilted?
« on: 20/02/2007 04:36:27 »
Hi,

I have a few questions regarding the axis of rotation of the earth and the planets.

Why does earth has an axial tilt of 23.5 C?
Is that axial tilt constant or is it changing?
Do other planets in our solar system have an axial tilt? If so why does it happen?
What influence does the axial tilt of the earth have on our environment?

Thanks,
Viswanath


 

lyner

  • Guest
Earth Axis Tilted?
« Reply #1 on: 20/02/2007 10:57:28 »
If you look 'down' on the Solar system (from over our North Pole) you will see that nearly everything is rotating or orbiting in an anticlockwise direction  and lies, roughly on a disc.    This is true of our Galaxy, too.  There is a general spin to the whole collection of objects.
It is the natural consequence of matter coming together, mutually attracted by gravity. If two objects move together, they will either hit each other (very unlikely, because they are tiny compared with the spare around them) or they will orbit around each other.  The original huge cloud of matter which now makes up our galaxy had a general swirliness in one  direction. We call this 'Angular Momentum' and the total amount of Angular Momentum stays the same over all time. 
The closer objects get, the faster they swirl round.
BUT this has been going on for a long time. Objects have hit each other and nearly missed each other. This has caused some to tilt and some to go the reverse way. The planet Uranus is tilted so much that it is virtually on its side.
The Earth's tilt is about 23.5 degrees and is responsible for our Seasons. Like a gyroscope, it leans the same way in space all year round, so its North pole is tilted towards the Sun in midsummer (for the Northern Hemisphere) and away six months later. It is warmer in Summer because - 1. The days are longer as more than half of the Northern hemisphere surface is lit. 2. The sunlight arrives from more directly overhead and is less 'spread out'.  If it weren't for the tilt, the polar icecaps would stay the same size and our days would all be 12 hours, everywhere. Boring!
The weather would probably be much more stable too.
The effect of the seasons and of the tides is thought to have accelerated evolution a lot. If living things had never been stranded ashore during the very high 'Spring' tides they would have probably have taken much longer to evolve to cope with life on dry land.
The seasons on Uranus will be VERY extreme.  It is perpetual day all of its summer  and perpetual night all of its winter.
 

lyner

  • Guest
Earth Axis Tilted?
« Reply #2 on: 27/02/2007 16:15:12 »
It's not the POLES that get hottest - the tilt isn't enough for that. It's the Tropics (Cancer in the North and Capricorn in the South) They are shown as dotted lines, 23 above and below the Equator. The Sun is overhead at (the corresponding) mid-summer 'solstice' at each.  The place where the Sun is directly overhead at midday at any point in the year will get the most heat. It's never directly overhead the Poles - but in Summer, the North Pole is never in the shade; the Sun being very low on the horizon even at midday so, although comparatively 'warmer' than in winter - it's never like Death Valley up there.

The overwhelming factor for temperature is Latitude; the tilt causes a variation from this basic factor.
The actual difference in distance is, of course, only a few thousand kilometers in 150 million km - the effect of this difference is negligible.  It's down to the spreading out  of the energy over the bits which don't face the Sun directly.

Another effect of latitude and Sun's elevation is that, at high latitudes, the sunlight has had to pass through some of the Earth's atmosphere which is over the more southerly bits - losing some of its energy to the air down there before it gets to the polar regions. Despite this being the reason that all school kids are given, I think this is a minor effect; the thickness of the thick part of the atmosphere is only about 100km so the light would have to arrive at a more or less 'grazing angle' for this to be significant.  (It's just easier for non-specialist teachers to explain, I think).
 

Offline rosy

  • Neilep Level Member
  • ******
  • Posts: 1018
  • Chemistry
    • View Profile
Earth Axis Tilted?
« Reply #3 on: 27/02/2007 17:54:38 »
It's a matter of intensity.
The amount of radiation per square meter perpendicular to the direction of travel of the sun's rays is constant (it's an r2 thing... the radiation at the equator is more intense per unit area of the earth's surface since it is more nearly perpendicular to the direction the photons are going in.
At the poles the earth's surface angles away from the sun so the same amount of energy is spread out further.

Maybe someone with more time will draw a diagram.
 

Offline daveshorts

  • Moderator
  • Neilep Level Member
  • *****
  • Posts: 2583
  • Physics, Experiments
    • View Profile
    • http://www.chaosscience.org.uk
Earth Axis Tilted?
« Reply #4 on: 27/02/2007 20:00:02 »
Not sure if I have more time but here is a diagram anyway

The same amount of sunlight is spread out over a larger area at higher lattitudes further from the equator.

The summer basically means that the sun is closer to being above you, so you get more intense sunlight.
 

lyner

  • Guest
Earth Axis Tilted?
« Reply #5 on: 28/02/2007 10:38:05 »
You get about 1kW, falling on every square meter at the equator, about 610W in the UK and, at a latitude of 80,170W (this would be at midday at the spring and autumn equinoxes, when the Sun is overhead at the Equator).
In midsummer, the UK would get about 860W and, in winter, 260W. No wonder we feel a difference.
Based on the Cosine of the angle of arrival.
 

lyner

  • Guest
Earth Axis Tilted?
« Reply #6 on: 01/03/2007 18:26:42 »
What actual mechanism were you proposing that would 'push heat' from poles to equator? Would it, in some way, deflect radiant energy from the Sun?
I am confused. The only way that e.m. radiation could be refracted would be due to some gradient of density / charges in the magnetosphere. I don't see how it could account for a lot of deflection.
Personally, I would look for some  explanation that relied  more upon tried and tested  Science. That is, until I knew an awful lot about the subject and felt in a position to question, with some justification, the accepted views.
 

Online Bored chemist

  • Neilep Level Member
  • ******
  • Posts: 8664
  • Thanked: 42 times
    • View Profile
Earth Axis Tilted?
« Reply #7 on: 04/03/2007 15:54:09 »
As far as I know there are no metals (or non metals come to that) that are still ferromagnetic at the temperatures that exist at the earth's core.
While it is true that, as isolated atoms, roughly half the atoms in the periodic table are paramagnetic, it is not true for anything like half of the compounds- the overwhelming majority of which are diamagnetic.
 

Offline Soul Surfer

  • Neilep Level Member
  • ******
  • Posts: 3345
  • keep banging the rocks together
    • View Profile
    • ian kimber's web workspace
Earth Axis Tilted?
« Reply #8 on: 04/03/2007 18:33:18 »
Jolly you are talking rubbish I don't know whether it is just because you want to start arguments, are just seriously lacking any real understanding of science or are doing it in some misguided impression that you are being humorous. 

You have been given a clear and scientifically accurate explanation of the question and still persist in trying to create pseudo scientific alternative explanations to confuse others.  Humour is OK as long as less well educated people don't accidentally take it as the truth or some alternative explanation.  At this point I will put it down to stupidity rather than malevolence but please make sure that if you put in silly humorous explanations that there is no possible doubt that this is what you are doing
 

The Naked Scientists Forum

Earth Axis Tilted?
« Reply #8 on: 04/03/2007 18:33:18 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums