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question about inclination of earth's axis.
I'm curious. Suppose I were to be deprived of technology and had to
rely only upon my observation, and intuition, how would I know that Earth's axis is inclined at an angle instead of being perpendicular? How did the ancients know that the axis of Earth is not perpendicular, but inclined ? regards, Abhishek. |
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question about inclination of earth's axis.
Abhishek wrote:
I'm curious. Suppose I were to be deprived of technology and had to rely only upon my observation, and intuition, how would I know that Earth's axis is inclined at an angle instead of being perpendicular? How did the ancients know that the axis of Earth is not perpendicular, but inclined ? The axis of the Earth is clearly not perpendicular to the ecliptic (the apparent orbital plane of the sun), because if it were, we wouldn't have any seasons. The Sun would always cross the sky at the same height, day after day. The amazing thing to me is that the Greeks even uncovered the precession of the equinoxes, and even gave a decent estimate as to how long the period is--about 36,000 years. (The actual value is about 25,800.) -- Brian Tung The Astronomy Corner at http://astro.isi.edu/ Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/ The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/ My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.html |
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question about inclination of earth's axis.
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question about inclination of earth's axis.
"Brian Tung" wrote in message
... [snip] The Sun would always cross the sky at the same height, day after day. Hmmm ok. Let's leave seasons out of it for a moment. Correct me if I am wrong here, but isn't this the same conclusion which would be drawn if earth's axis was inclined but of constant inclination /with respect to the sun/? In other words, let me rephrase the question. Suppose earth's inclination with respect to the sun was always constant, so that, say, the northern hemisphere always has summer and the southern always winter. Except for travelling to the opposite hemispehere, how can we deduce that the axis is inclined? [snip] -- Brian Tung -- Ioannis |
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question about inclination of earth's axis.
Allison Kirkpatrick wrote:
You would probably first have to figure out that the Earth is spherical, rather than flat, and in orbit around the sun, rather than vice-versa. I think the question presumes knowledge that the Earth is spherical (otherwise, it doesn't have an axis). I don't agree that it requires knowing that the Earth revolves around the Sun, except that the question must be rephrased as how one figures out that the Earth's axis is not perpendicular to the Sun's orbital plane. The above applies to points on earth north and south of the two Tropics; between them things are a little different, but I will save that topic for a later installment. Are you sure? How so? -- Brian Tung The Astronomy Corner at http://astro.isi.edu/ Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/ The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/ My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.html |
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question about inclination of earth's axis.
Ioannis wrote:
Hmmm ok. Let's leave seasons out of it for a moment. Correct me if I am wrong here, but isn't this the same conclusion which would be drawn if earth's axis was inclined but of constant inclination /with respect to the sun/? In other words, let me rephrase the question. Suppose earth's inclination with respect to the sun was always constant, so that, say, the northern hemisphere always has summer and the southern always winter. Except for travelling to the opposite hemispehere, how can we deduce that the axis is inclined? The Sun would not be travelling in a great circle. That'd be the first clue. Whether that clue would be interpreted correctly is another matter, of course. -- Brian Tung The Astronomy Corner at http://astro.isi.edu/ Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/ The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/ My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.html |
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question about inclination of earth's axis.
Brian Tung wrote: Ioannis wrote: Hmmm ok. Let's leave seasons out of it for a moment. Correct me if I am wrong here, but isn't this the same conclusion which would be drawn if earth's axis was inclined but of constant inclination /with respect to the sun/? In other words, let me rephrase the question. Suppose earth's inclination with respect to the sun was always constant, so that, say, the northern hemisphere always has summer and the southern always winter. Except for travelling to the opposite hemispehere, how can we deduce that the axis is inclined? The Sun would not be travelling in a great circle. That'd be the first clue. Whether that clue would be interpreted correctly is another matter, of course. -- Brian Tung The Astronomy Corner at http://astro.isi.edu/ Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/ The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/ My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.html No need to reference the axial/Equatorial orientation of the Earth against an object 93 million miles away. Take a look at the Earth from space - http://geophysics.ou.edu/solid_earth...from_space.jpg The axial orientation is constant but as the Earth travels in its orbit around the Sun,the orbital orientation (assigned by the terminator) changes longitudinally as well as latitudinaly .We hardly notice it from one day to the next because of the way axial rotation passes through that changing feature but it is there nad generates global climate norms and hemispherical weather pattern (seasons). Lots and lots of productive avenues to be explored by looking at things this way,of course you can always remain with your variable tilting Earth to the Sun/orbital plane - http://www.scienceu.com/observatory/...s/earthyrb.gif Astronomers would not resort to the northern hemisphere tilting towards and away from the sun and pretend that the southern hemisphere does not share the same axis.The 21st century view for global climate norms which can be reduced to hemispherical weather patterns for meteorological purposes is the local change of orbital orientation against fixed axial orientation. Important material ,too important to play around with .Here are the temperature signatures of the change in orbital orientation which assist in the transitionto a more productive astronomical mechanism based on change in orbital orientation - http://www.climateprediction.net/ima...ges/annual.gif In short - KEEP THINGS LOCAL |
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question about inclination of earth's axis.
lal_truckee wrote:
Sun, Moon, and stars wobble. Lots of ancient constructions are built to mark the extremes of the wobble. Or at least imaginative archaeologists seem to think so. Whenever I've seen the actual evidence in these cases it always reminds me a bit of the "evidence" for the pyramids on mars... There is so much room for over interpretation that my bad science alarm bells go off wildly. One thing I know for certain: if you go looking hard enough for anything you are going to find it. And just because you find "it" everywhere you look, provided you look really hard, doesn't mean it's real. Yet that's just the sort of "science" applied in these circumstances. What I'm saying is that without objective evidence most of these claims are less than compelling. They are little more the speculation. Yet they are often cited as fact. -- Greg Crinklaw Astronomical Software Developer Cloudcroft, New Mexico, USA (33N, 106W, 2700m) SkyTools: http://www.skyhound.com/cs.html Observing: http://www.skyhound.com/sh/skyhound.html Comets: http://www.skyhound.com/sh/comets.html To reply take out your eye |
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question about inclination of earth's axis.
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#10
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question about inclination of earth's axis.
On Wed, 24 May 2006 20:39:54 +0300, "Ioannis"
wrote: In other words, let me rephrase the question. Suppose earth's inclination with respect to the sun was always constant, so that, say, the northern hemisphere always has summer and the southern always winter. Except for travelling to the opposite hemispehere, how can we deduce that the axis is inclined? If that were true the apparent position of the Earth's pole in the sky would circle around once a year. |
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