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$CO_2$: Without greenhouse gases, Earth would be about 30 degrees colder. Everyone sensible agrees that $CO_2$ contributes to this, but also that it only directly causes part of the warming. Water vapor is the other important greenhouse gas. There are feedback relationships between temperature, $CO_2$ levels, and water vapor levels, e.g. if the world gets ...


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Short answer: like often, it's a balance between opposite trends: self-gravity causing collapsing thus densification build huge pressure that permit nuclear fusion high-temperature and pression caused by these reactions inflate the star which decrease the amount of reaction (or might even stop them if inflating too much). As long as everything is slow ...


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If you compare the Earth-Sun distance in the summer and in the winter, you will notice that it differs by only about 4%. Given that the radiation strength of the Sun is proportional to 1/distance^2, the radiation intensity is roughly 8% STRONGER in the WINTER (on the northern hemisphere) than in the summer. But the distance to the Sun is not the only ...


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It is a very general doubt and really important. Slanting sun rays coming to earth from sun are refracted and rarely reach earth. They deviate by refraction. At equator and tropics refraction is less. As you know for $\theta = 0$ no refraction take place and as angle increase refraction increase. As poles do not get much sun rays throughout year and ...


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Why are Lunar Eclipse more common than Solar Eclipse? They aren't. Lunar eclipses and solar eclipses occur with almost equal frequency. From http://eclipse.gsfc.nasa.gov/eclipse.html and pages within, there were / will be 11898 solar eclipses of all types and 12064 lunar eclipses of all types in the five millennia between 2000 BCE to 3000 CE. Lunar ...


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The apparent size of the moon (from Earth) is about the same as the sun's. Therefore the moon has to pass over the sun's path at the time of the new moon for there to be a solar eclipse. The apparent size of Earth (from the moon) is much greater than that of the sun - because the Earth's diameter is about 4 times that of the moon, and hence the alignment ...


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You could try measuring the effects of the Lense-Thirring effect. It is an example of frame dragging. Essentially, an object that is orbiting near a massive object that is also rotating will have its axis undergo a change in its orientation. There are two problems here: The rotating object must be large. The rotating object must not be rotating slowly. ...


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One can use the Doppler effect, which will shift spectral lines to the red at the side the rotates away from us and towards the blue on the side that rotates towards us. This is being used by astronomers who measure "rotational broadening" on stars which can not be resolved in telescopes. In that case it's all about measuring the rate of rotation, of course, ...


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I don't think this question is worth a bounty, so I feel a bit bad in answering it, but... Summary: Compute the number of days since 31 December 1999 (or even December 31st of the previous year if you need less precision), call this d. Compute the sun's declination: $ 0.171144 \cos (2.6491\, -0.0516083 d)+0.381008 \cos (3.03481\, -0.0344047 ...



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