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Why are upper-main-sequence stars unlikely sites for intelligent civilizations?
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The "upper main sequence" is the name for massive stars, which have high luminosity and relatively short lifetimes (often less than a billion years). While we can only speculate about where and when intelligence and civilizations arise, it seems reasonable to expect this to happen for older planetar... Click here for more.
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Why is the Oort Cloud postulated to be a shell-like structure while most other objects in the Solar System are more or less in the plane of the ecliptic? |
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The Oort Comet Cloud has been measured to extend away from the Sun in all directions, rather than being confined near the ecliptic as are the planets and the Kuiper Belt of comets. When we observe Oort-cloud (long period) comets, we see that they come from all directions about equally. This is an ob... Click here for more.
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Is there any planet without a night? How many moons it has? |
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"Night" simply refers to the side of a planet that faces away from the Sun. Any planet will have one side that is illuminated by the Sun and one side that is in night, and as the planet rotates day and night alternate as they do on Earth.
David Morrison
NAI Senior Scientist... Click here for more.
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I have two questions for you. As far as I know anything that enters earth's atmosphere from space would be engulfed in flames. Is there anyway something would not burn up in our atmosphere? Is it possible (even if it's very very remote) that some object could line up with our orbit and kind of coast to the surface of earth. |
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I would not quite say incoming objects are engulfed in flames. Atmospheric resistance heats the outer surfaces, with ablation of very hot gas. Small incoming objects (meteors or shooting stars) are destroyed in this process, but larger rocks can land on the surface as meteorites. Since the atmospher... Click here for more.
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I understand that both Saturn and Jupiter have extreamly active atmospheres and give out lethal doses of radiation, so are they hot or cold? |
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Jupiter and Saturn are both hot and cold; cold in their upper atmospheres and very hot in their interiors (just as is true for Earth). The lethal doses of radiation originate outside the planet, in the charged atomic particles moving in the magnetospheres of Jupiter and Saturn. You are running into ... Click here for more.
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Ok creationists believe nothing is older than some date of BC. Then there is carbon dating. Does carbon dating show that the Earth is old? Is it reliable? |
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Carbon dating, also called radiocarbon dating, uses the decay of radioactive carbon (the naturally occurring isotope carbon-14) to determine the age of carbonaceous materials up to about 60,000 years. The technique of radiocarbon dating was discovered by Willard Frank Libby and his colleagues in 194... Click here for more.
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In the same way that Mars has two small moons which appear to be captured asteroids, does or could the Earth have any other, small natural satellites, or would the gravitational pull of the Earth and Moon quickly bring them out of orbit? |
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Many astronomers have looked for such small natural satellites, as well as captured asteroids in the "Trojan points" of the Earth's orbit around the Sun, but none have been found. Both small satellites and Trojans are common in the outer solar system. These regions are gravitationally unstable for E... Click here for more.
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My fourth grade class is studying about Jupiter and we are finding conflicting reports about how many moons Jupiter has. Can you please give us an up-to-date accurate count of how many moons Jupiter has? |
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The reports are conflicting because more moons of the outer planets are being discovered so often. Of course, we don't know how many moons Jupiter, Saturn, Uranus and Neptune each have; we can only report how many have been discovered to date. The last number I have read for Jupiter is 62 moons disc... Click here for more.
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I live in Iran,heard of radio seen 2 objects unknown in the sky of Qazvin city for 2 hours,one of them was higher than other and sometimes was unvisible,what about this news? |
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I am glad that "Ask and Astrobiologist" is read in Iran, but I can't help you on your question. "Two objects in the sky" could be almost anything (you don't say if this was day or night). I can't help noting the amusing coincidence of a company called Ufo Electronics in Qazvin, Iran, which is listed... Click here for more.
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Since you deny the existence of pyramids on Mars, perhaps you could train your photo surveillance of that planet on the area where the pyramids are supposedly located. Why is that area off limits to photo surveillance which could be beamed back to earth before being doctored? |
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First, I don't deny the presence of pyramids on Mars; just like the Earth, Mars has a number of pyramid-shaped hills or mountains. This is a shape that can be formed by either water or ice or wind erosion (think about the Matterhorn, one of the most famous four-sided pyramid-peaks on Earth). Essenti... Click here for more.
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