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宇宙学之

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宇宙学之宇宙的诞生,演化和结局(f1)易中天,马瑞芳,于丹杞人忧天《列子》的《天瑞》篇记载:杞国有人、忧天地崩坠,身亡所寄,废寝忘食在科学中-无事忧No诗人李白疑是银河落九天富有浪漫的惊人想象-对文学家来说Yes or No古希腊的哲人也思考天坠问题
亚力士多德: 两界说
月亮: 世俗和神界No《物理》- 第一推动
牛顿:思考苹果落地-发现引力定律Yes月亮不落地的初始速度- 第一推动Why is the night darkDay is brightNight is dark
A: Because no Sun shines at night.
B: This answer is wrong.Because the sky dosenot have just one sun.Stars are still shining atnight.
A: No the stars are very far from us, their light must not be enough to light up the sky.
B: The light from one star is, to be sure, too weak to light up the sky, but the universe is huge and there are infinitely many stars.
With infinitely many stars, every angular element of the sky should haveastar, and the entire heavens should be as bright as the sun.
Gregory and Thompson Geller and Huchra 1986SDSS Collaboration 2002Heinrich Wilhelm Olbers (1823)Wilhelm OlbersOlbers Paradox夜黑佯谬or 奥勃斯佯谬If the Universe is infinite, any line of sight will eventually end on the surface ofadistance star. Therefore, the sky should be everywhere be as bright as the surface ofastar (like the sun)【1826年】.
Theres too much dust to see the distant starsThe Universe has onlyafinite number of stars.
The distribution of stars is not uniform._ So, for example, there could be an infinity of stars, but they hide behind one another so that onlyafinite angular area is subtended by them.
The Universe is expanding, so distant stars are red-shifted into obscurity【黯淡,模糊】.
The Universe is young._ Distant light hasnt even reached us yet.
Okay, so whats the way outSomething must be wrong with one (or more) of the following assumptions, or some physics has not been considered.
Conservation of energyNo absorption of photons in spaceNumber of stars is infinitThe universe is infinit,(space and time)Stars are staticPossible Solutions to Olbers ParadoxThere is too much dust to see distant stars.
The Universe only hasafinite amount of stars.
The distribution of stars is highly-non uniform (ie. there could be an infinite number of them, but all lined up one behind another, so onlyafinite angular area is covered).
The Universe is expanding, so distant stars are red-shifted into
The Universe is young. Distant light hasnt even reached us yet (a cosmological horizon exists).
Wont ! But notdominantYes! current Universe is onlybillion years old and so has an observable size of onlybillion light years. This is much less than needed to produce Olberss Paradox. The fact that the Universe hasafinite age is the principal explanation of Olberss Paradox.
When would the sky fallThere wasaman of ChI country who was so worried that heaven might fall.he could neither eat nor Page | All Current Headlines | ArchivesThe Sky Might Fall In 2880
Source: Wired
URL:
12:00 p.m. AprilPST WASHINGTON -Anew look at an asteroid[小行星] orbiting the sun shows it could possibly smash into the Earth with the explosive force of millions of tons of TNT. But experts say the potential impact is still 878 years away, time enough for the speeding space rock to alter its course. Named 1950 DA and six-tenths ofamile wide, the asteroid is the most threatening to the Earth of all of the known large asteroids, but the odds are only about one in 300 that it would impact the planet.
click here to read this Wired article.
Aug Industrial Production Rises 0.7 Pct- MEXICO CITY, Oct 14 (Reuters) - Mexicos industrial production in August rosealower than expected 0.7 percent compared to the same monthayear ago, although it wasasecond month of consecutive growth, the Finance Ministry said on.
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TEXT-Moodys Affirms National Oilwell RatingNEW YORK, Oct 14 - Moodys Investors Service confirmed National Oilwell, Inc.s (nyse: NOI - news - people ) (NOI) Baa2 senior unsecured rating withastable outlook. The rating action was prompted by the companys announcement that it had agreed to.
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Format: CDExpert RatingNo RatingUser RatingNot Yet RatedCompare 天地Celestial matterEarthly would thesky, following theapple, fallNewtonAll falling bodies experience the same gravitational of Falling Bodies (Galileo)Law of Universal Gravitation (Newton)
Gravity is an attractive force between all pairs of massive the fall of an apple on the Earth.
Governs the fall of the Moon around the Earth.
Governs the fall of the EarthMoon system around the Sun.
The Apple and the MoonWhen would the moon,following the apple, fallHe (Newton) proves that no suchthings asacetestial metterSolar systemPluto【冥王星】WalkNewtonian gravity is !Comet Jupiter JulyDeep Impact Mission on comet 1.8-meter Telescope in Tucson
2001 OctoberFirst two with the Spacewatch
1.8-meter telescope spacewatch
12:00 p.m. AprilPST WASHINGTON -Anew look at an asteroid orbiting the sun shows it could possibly smash into the Earth with the explosive force of millions of tons of TNT. But experts say the potential impact is still 878 years away, time enough for the speeding space rock to alter its course. Named 1950 DA and six-tenths ofamile wide, the asteroid is the most threatening to the Earth of all of the known large asteroids, but the odds are only about one in 300 that it would impact the planet.
space watch in ancient astronomers would look for any changesin the night sky anything that was outsidethe normal regular predictable pattern.
The local group bound group of ~20 galaxies, including our own, with overall diameter of ~1 Mpc.
Large Scale Structure: Galaxy Clusterswe are falling to Virgo cluster !
supernova watch in present timesky0the universeIf gravitation is universalThe age of the universe isFinite !orgravitation is NOT universalThere are repulive force !The Universe is expandingThe Hubble LawExpansion of the Universe
.winding backwards, the universe must have hadabeginning Hubbles LawEdwin trained asalawyer, before boredom made him turn to astronomy insteadFirst to realise that galaxies lieoutside the Milky Way .
.by measuring their distances using Cepheid variables asstandard candlesCepheid variables oscillate in brightness witharegular period that depends on their luminosity. By measuring this period, they can be used as standard candles.
Extending the Distance ScaleWith their high luminosities (~10,000 Lsun), Cepheid variables extend the distance scale to nearby galaxies, out ~15 Mpc.
Doppler effectCosmic Speedometer[里程记]Hubble measured the spectrumof these galaxies and found thespectral lines to be red-shiftedThe faster the recession, thegreater the is receding, light waves travelling to us are red-shifted
Note: Before turning to astronomy, Hubble wasalawyer.
Hubble constant graph

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