Rotating Question Curious About Astronomy? Ask an Astronomer

All previously answered questions (in order of times viewed)

  1. What's going to happen on December 21st 2012? (viewed 2149742 times)
  2. What color is each planet? (viewed 949539 times)
  3. At what speed does the earth move around the sun? (viewed 616066 times)
  4. Is the Moon moving away from the Earth? When was this discovered? (viewed 591106 times)
  5. How far is each planet from Earth? (viewed 488486 times)
  6. When will Halley's Comet return? (viewed 440793 times)
  7. How long does it take for the Sun's light to reach us? (viewed 404050 times)
  8. Why do the planets orbit the sun? (viewed 399509 times)
  9. How many stars are there in our Galaxy (Milky Way)? (viewed 395205 times)
  10. What is the universe expanding into? (viewed 381597 times)
  11. How do you measure the distance between Earth and the Sun? (viewed 359996 times)
  12. Why do stars twinkle? (viewed 328522 times)
  13. Which planets have rings? (viewed 327627 times)
  14. Does the Moon rotate? Are there other moons that always keep one face toward their planet? (viewed 309415 times)
  15. Can you hear sounds in space? (viewed 302408 times)
  16. How do I build a model rocket? (viewed 294707 times)
  17. What are the different kinds of astronomers? (viewed 280006 times)
  18. What color is Venus? (viewed 278914 times)
  19. What is a white hole? (viewed 273818 times)
  20. What is that ring (or rainbow) around the moon? (viewed 249566 times)
  21. What is the life cycle of a star? (viewed 249044 times)
  22. What are the names of the earth, moon, sun, and solar system? (viewed 246474 times)
  23. What makes the Earth rotate? (viewed 244166 times)
  24. What are shooting stars? (viewed 237291 times)
  25. Can artificial gravity be created in space? (viewed 224696 times)
  26. How do we know the age of the Universe and the Earth? (viewed 224485 times)
  27. What is the largest star? (viewed 223436 times)
  28. Is the universe expanding faster than the speed of light? (viewed 217935 times)
  29. Why do planets rotate? (viewed 217662 times)
  30. What do astronauts eat in space? Can they grow food? (viewed 217273 times)
  31. How does the location of sunrise and sunset change throughout the year? (viewed 212593 times)
  32. How can we see the Milky Way if we are inside it? (viewed 195069 times)
  33. Where did the name 'Earth' come from? (viewed 184472 times)
  34. How does the position of Moonrise and Moonset change? (viewed 183433 times)
  35. Why is a day divided into 24 hours? (viewed 183350 times)
  36. What would happen if we did not have a Moon? (viewed 181300 times)
  37. Why isn't the sky bright at night if the universe has so many stars? (viewed 177249 times)
  38. How many Earths fit into the Sun? (viewed 175397 times)
  39. Why do airplanes take longer to fly West than East? (viewed 173514 times)
  40. When was the last time all 9 planets were aligned? (viewed 170223 times)
  41. Who named the planets and who decides what to name them? (viewed 170035 times)
  42. Why are the Moon and Sun sometimes orange or red? (viewed 163484 times)
  43. How can I find the star I have "bought"? (viewed 157983 times)
  44. Is the distance from the Earth to the Sun changing? (viewed 155972 times)
  45. What is at the end of the Universe? (viewed 154888 times)
  46. Is Pluto a planet? (viewed 153135 times)
  47. How much money is spent on space exploration? (viewed 150345 times)
  48. What is a nova? (viewed 148853 times)
  49. Does your weight change between the poles and the equator? (viewed 144523 times)
  50. How do astronauts take baths and use restrooms in space? (viewed 140250 times)
  51. Can we feel the Earth spin? (viewed 137885 times)
  52. What direction do planets rotate? (viewed 134693 times)
  53. Why are there both high and low tides? (viewed 133023 times)
  54. Do stars move in the sky? (viewed 132455 times)
  55. Is the Sun expanding? Will it ever explode? (viewed 132142 times)
  56. What is the largest galaxy? (viewed 128305 times)
  57. Why do all the planets orbit in the same plane? (viewed 127893 times)
  58. How many known galaxies are there? (viewed 127244 times)
  59. What are the advantages and disadvantages of using a telescope in space? (viewed 127206 times)
  60. What is the physical difference between a star and a planet? (viewed 125351 times)
  61. How are light and heavy elements formed? (viewed 122233 times)
  62. Can I buy a star? (viewed 121253 times)
  63. Why do planets have elliptical orbits? (viewed 119232 times)
  64. Are there telescopes that can see the flag and lunar rover on the Moon? (viewed 118188 times)
  65. Why hasn't NASA gone back to the moon? (viewed 117978 times)
  66. Will the sun go supernova in six years and destroy Earth (as seen on Yahoo)? (viewed 117569 times)
  67. What is the significance of the Tropic of Cancer, Tropic of Capricorn, Arctic Circle and Antarctic Circle? (viewed 116735 times)
  68. Who first measured the speed of light? (viewed 116514 times)
  69. How do stars move in the Galaxy? (viewed 116007 times)
  70. Does the Sun have a scientific name? (viewed 115940 times)
  71. What happens when galaxies collide? (viewed 114543 times)
  72. How do rockets work? (viewed 114076 times)
  73. What is the hottest time of day? (viewed 112837 times)
  74. Does evolution contradict the second law of thermodynamics? (viewed 111779 times)
  75. What is the size of the Solar System? (viewed 111631 times)
  76. What would happen if an impact caused Earth to stop rotating? (viewed 110721 times)
  77. What do astronauts do all day in the International Space Station? (viewed 110652 times)
  78. How much money do astronomers make? (viewed 110614 times)
  79. How do you calculate the lifetime of the Sun? (viewed 110184 times)
  80. What will happen to life on Earth when the Sun becomes a red giant? (viewed 109945 times)
  81. What was there before the Big Bang and what is there outside of our universe? (viewed 108788 times)
  82. Will the magnetic field of the Earth reverse its direction in the future? Will this cause problems? (viewed 108578 times)
  83. What elements make up the Sun? (viewed 108495 times)
  84. What is the observational difference between a star and a planet? (viewed 108209 times)
  85. What are constellations used for? (viewed 108115 times)
  86. What would happen if the gravity on Earth was suddenly turned off? (viewed 108075 times)
  87. When is the next comet due to arrive? (viewed 108062 times)
  88. Does gravity vary across the surface of the Earth? (viewed 107035 times)
  89. How long does a solar eclipse last? (viewed 106802 times)
  90. Do black holes die? If so how? (viewed 106620 times)
  91. How many constellations are there? (viewed 105762 times)
  92. What's the difference between astronomy and astrology? (viewed 104687 times)
  93. Does the Sun rotate? (viewed 103512 times)
  94. Why do different stars appear with seasons? (viewed 102300 times)
  95. How many meteorites hit Earth each year? (viewed 101773 times)
  96. Does the Sun move around the Milky Way? (viewed 100948 times)
  97. What kind of schooling is necessary to become an astronomer? (viewed 100427 times)
  98. Which planet is most similar to Earth? (viewed 99499 times)
  99. What is apparent magnitude? (viewed 99043 times)
  100. Is there a proof that Earth moves? (viewed 95060 times)
  101. What is the difference between a "star" and a "sun"? (viewed 95020 times)
  102. If Mars is only about 35-60 million miles away at close approach, why does it take 6-8 months to get there? (viewed 94775 times)
  103. How do astronomers use math in their jobs? (viewed 94710 times)
  104. How can a star burn with no oxygen? (viewed 93208 times)
  105. Where did the Universe come from? (viewed 93019 times)
  106. Why is the Universe flat and not spherical? (viewed 92876 times)
  107. Does the Sun orbit the Earth as well as the Earth orbiting the Sun? (viewed 92848 times)
  108. Why are stars and planets round? (viewed 92820 times)
  109. How critical is the Earth-Sun distance in maintaining our average temperatures on Earth? (viewed 92527 times)
  110. What are the requirements for being a planet? (viewed 92365 times)
  111. Why is the Moon so bright? (viewed 91827 times)
  112. What is a singularity? (viewed 91803 times)
  113. What makes the wind? (viewed 91313 times)
  114. What would happen if an asteroid 10 kilometers across hit the Earth? (viewed 90366 times)
  115. Have astronomers discovered Earth's second moon? (viewed 88993 times)
  116. Since Earth is spinning, why do we land in the same place when we jump or fall? (viewed 86330 times)
  117. Why does the Earth tilt back and forward once a year? (viewed 86213 times)
  118. What are RA and DEC? (viewed 86099 times)
  119. Where does the name "Milky Way" come from? (viewed 85196 times)
  120. Considering the motion of the Earth, the solar system, and the galaxy, how fast am I moving while lying in bed asleep? (viewed 84118 times)
  121. How many stars are born and die each day? (viewed 83774 times)
  122. What would happen if Earth had more than one moon? (viewed 82728 times)
  123. Why is the moon in a different place every night? (viewed 82554 times)
  124. Why aren't there any green stars? (viewed 81071 times)
  125. How do we weigh objects in space? (viewed 79715 times)
  126. How are galaxies formed? (viewed 79358 times)
  127. What kind of rock is the moon made of? (viewed 79263 times)
  128. Did astronauts really go to the Moon, or is it a hoax? (viewed 79107 times)
  129. Will the Sun become a black hole one day? (viewed 77610 times)
  130. What is the density of a black hole? (viewed 77322 times)
  131. What would happen if a supermassive black hole came close to the Earth? (viewed 76625 times)
  132. How are black holes made? Could one be made close to us? (viewed 76487 times)
  133. How do rockets move in space? (viewed 75929 times)
  134. What happens to a substance if its speed is more than the speed of light? (viewed 75751 times)
  135. Can moons have moons? (viewed 75750 times)
  136. What would happen if you took off your helmet in space? (viewed 75735 times)
  137. What is the evidence supporting the nebula theory of Solar System formation? (viewed 75571 times)
  138. Why can't you see stars during the day? (viewed 75080 times)
  139. Do most astronomers believe in God based on the available scientific evidence? (viewed 75026 times)
  140. Does the Mediterranean sea have tides? (viewed 74935 times)
  141. When the Sun converts mass to energy, do the orbits of the planets change? (viewed 74890 times)
  142. How do astronomers measure the brightness of stars? (viewed 74794 times)
  143. Who has landed on the moon? (viewed 74420 times)
  144. What would you see from inside a black hole? (viewed 74267 times)
  145. Why do we not have eclipses every month? (viewed 74040 times)
  146. How often does the Sun pass through a spiral arm in the Milky Way? (viewed 74023 times)
  147. What are some of the effects of solar flares on Earth? (viewed 73329 times)
  148. How do we know the mass of the Earth and the Moon? (viewed 73169 times)
  149. How can the Universe expand faster than the speed of light during inflation? (viewed 73060 times)
  150. Can you fire a gun on the Moon? (viewed 72635 times)
  151. How is astronomy impacted by trigonometry? (viewed 72207 times)
  152. How do you measure a planet's mass? (viewed 71970 times)
  153. How does the Moon stay "suspended" in the air? (viewed 71707 times)
  154. Is it possible to measure the temperature of the Sun? (viewed 71635 times)
  155. How are elements heavier than iron formed? (viewed 71525 times)
  156. Why do stars change colour when they twinkle? (viewed 71225 times)
  157. How does the Sun compare to other stars? (viewed 70588 times)
  158. What are the "dog days of summer"? (viewed 68155 times)
  159. Does quantum entanglement imply faster than light communication? (viewed 67882 times)
  160. How long would it take the Earth to fall into the Sun? (viewed 67323 times)
  161. How does light pollution affect astronomers? (viewed 67244 times)
  162. What kinds of jobs do astronomers do? (viewed 66935 times)
  163. If the universe is infinite does that mean there is an infinite number of "me"s? (viewed 66667 times)
  164. Where does the name "Moon" come from? (viewed 66642 times)
  165. How did the stars get named? (viewed 66233 times)
  166. Where did the matter in the universe come from? (viewed 66134 times)
  167. How do you measure the mass of a star? (viewed 65975 times)
  168. Why doesn't the earliest sunset occur on the shortest day of the year? (viewed 65877 times)
  169. Are there stars outside of galaxies? (viewed 65847 times)
  170. Traveling at light speed, how long would it take to get to the nearest galaxy? (viewed 65801 times)
  171. What are Altitude and Azimuth? (viewed 65425 times)
  172. What are black holes made of? (viewed 65204 times)
  173. How did asteroids form and what is the difference between an asteroid and a comet? (viewed 64961 times)
  174. Why is looking out into space the same as looking back in time? (viewed 64694 times)
  175. What causes seasons? (viewed 64639 times)
  176. How fast is the Universe expanding? (viewed 64018 times)
  177. What's the difference between dark matter and dark energy? (viewed 64011 times)
  178. Where, in relation to the entire universe, is the Milky Way located? (viewed 63735 times)
  179. When can I see the Moon through the hole in the Pantheon? (viewed 63670 times)
  180. Why do planets not twinkle? (viewed 63517 times)
  181. What's the best college for astronomy? (viewed 63015 times)
  182. What would happen to us if the sun went out for an hour? (viewed 62805 times)
  183. Why doesn't the length of each day change much around the solstices? (viewed 62773 times)
  184. Why does the Sun's apparent path through the sky change throughout the year? (viewed 62765 times)
  185. What can we learn from the color of a star? (viewed 62547 times)
  186. How does astronomy benefit humankind? (viewed 62370 times)
  187. What is the mass of the Universe? (viewed 61530 times)
  188. How can I calculate the position or path of the Sun for a given time and location? (viewed 61116 times)
  189. How does the parachute in a model rocket work? (viewed 60898 times)
  190. What is the origin of spiral structure in galaxies? (viewed 60794 times)
  191. Why does the Earth have only one moon? (viewed 60521 times)
  192. How close was the Moon to the Earth when it formed? (viewed 60504 times)
  193. How do the astronauts communicate in space if sound cannot travel in a vacuum? (viewed 60457 times)
  194. Can any galaxies be seen with the naked eye? (viewed 60372 times)
  195. Could there be life in the galaxies nearest to the Milky Way? (viewed 60117 times)
  196. Does the Moon rotate? (viewed 60117 times)
  197. How long does the supernova stage of a star last? (viewed 59530 times)
  198. What makes up most of the Universe? (viewed 59411 times)
  199. If gravity is a "curvature of space" rather than a force, why do a ball and bullet follow different paths? (viewed 58656 times)
  200. What is a star's "spectrum"? (viewed 57484 times)
  201. What is the shape of the universe? (viewed 57300 times)
  202. Why isn't the summer solstice the hottest day of the year? (viewed 57287 times)
  203. How do astronauts use math in their jobs? (viewed 57220 times)
  204. Is the Moon seen as a crescent (and not a "boat") all over the world? Is the same phase of the moon visible from the Northern and Southern hemispheres? (viewed 57136 times)
  205. What happens to a bullet fired on the moon? (viewed 56984 times)
  206. How do we measure the size of the Moon and of the Sun? (viewed 56701 times)
  207. How do you calculate the azimuth and altitude of an object? (viewed 56505 times)
  208. What is the size of a black hole? (viewed 56286 times)
  209. Where did all the water in the universe come from? (viewed 56270 times)
  210. What is the largest structure in the universe? (viewed 56227 times)
  211. Which constellation does our Sun belong to? (viewed 55858 times)
  212. Where are stars born? (viewed 55827 times)
  213. How can I find the distance to the Sun on any given day? (viewed 55580 times)
  214. Are names given to black holes? (viewed 55299 times)
  215. Why is twilight short near the equator? (viewed 55082 times)
  216. Which hemisphere has the best view of the Milky Way? (viewed 55072 times)
  217. Can you see satellites? (viewed 54996 times)
  218. What other careers involve Astronomy besides Astronomer? (viewed 54638 times)
  219. Why do we see stars? (viewed 54320 times)
  220. What do a galaxy's colors mean? Are they its true colors? (viewed 54230 times)
  221. Are meteorites hot or cold when they hit Earth? (viewed 53865 times)
  222. Why is the sky blue and not blue & purple? (viewed 53841 times)
  223. Are aliens or UFOs real? (viewed 53768 times)
  224. Is the speed of light constant? (viewed 53748 times)
  225. How can I measure the distance of a star? (viewed 53689 times)
  226. Are there any asteroids on a collision course with Earth? (viewed 53480 times)
  227. Would your weight change as you go underground? (viewed 53250 times)
  228. How long has there been water on Earth? (viewed 53223 times)
  229. How do we know what other planets (and stars, galaxies, etc.) are made of? (viewed 52876 times)
  230. What would happen if the Moon fell out of its orbit around Earth? (viewed 52864 times)
  231. How is the time of sunrise calculated? (viewed 52683 times)
  232. What are some astronomy science fair projects? (viewed 52335 times)
  233. Can we look back far enough in time to see the Big Bang? (viewed 52233 times)
  234. What skills do astronomers need? (viewed 51989 times)
  235. Are the planes of solar systems aligned with the plane of the Galaxy? (viewed 51923 times)
  236. Why does the Moon look big on the horizon? (viewed 51681 times)
  237. If the Earth's rotation period is less than 24 hours, why don't our clocks fall out of sync with the Sun? (viewed 51511 times)
  238. Who discovered each planet? (viewed 51391 times)
  239. Is time travel possible? (viewed 51367 times)
  240. What is the difference between nutation and precession of the Earth? (viewed 51143 times)
  241. Can the acceleration of the Universe be analogous to apparent acceleration in a airplane? (viewed 51000 times)
  242. What's the difference between astronomy and astrophysics? (viewed 50636 times)
  243. Why is it difficult to understand the expansion of the universe? (viewed 50470 times)
  244. Why are most months 30 or 31 days long? (viewed 50270 times)
  245. What is a graviton? (viewed 50245 times)
  246. If light has no mass, then what draws it into a black hole? (viewed 50064 times)
  247. Why do the size and brightness of the full moon change? (viewed 49139 times)
  248. Can we find the place where the Big Bang happened? (viewed 48839 times)
  249. Do supermassive black holes cause galaxy rotation? (viewed 48831 times)
  250. Why does the Sun appear larger on the horizon than overhead? (viewed 48478 times)
  251. What do I need to do to become an astronomer? (viewed 48094 times)
  252. Why don't people walk upside-down on the bottom of the Earth? (viewed 48050 times)
  253. How are black holes discovered? (viewed 48014 times)
  254. How do gravitons escape black holes to tell the universe about their gravity? (viewed 48011 times)
  255. What is a wormhole? (viewed 47809 times)
  256. The Moon slows the Earth's rotation, but how fast was it spinning billions of years ago? (viewed 47807 times)
  257. Do dead stars still shine? (viewed 47565 times)
  258. Why are there stars? (viewed 47240 times)
  259. Is the Earth slowly getting larger? (viewed 46903 times)
  260. Did life originate on Earth, or did it come from somewhere else? (viewed 46679 times)
  261. Will we get sucked into the black hole at the center of the Milky Way? (viewed 46542 times)
  262. Why can't we see Venus at night when it is an inner planet? (viewed 46500 times)
  263. Are Kuiper Belt Objects asteroids? Are large Kuiper Belt Objects planets? (viewed 46218 times)
  264. How do galaxies collide in an expanding universe? (viewed 46176 times)
  265. Why does Barnard 68 appear dark? (viewed 46144 times)
  266. Where is the nearest black hole? (viewed 46056 times)
  267. Can I calculate the size of the Universe by converting light years to kilometres? (viewed 45573 times)
  268. Are there eclipses on other planets? (viewed 45062 times)
  269. How much can the location of sunset differ from due West? (viewed 44749 times)
  270. How long could life on Earth survive if the Sun stopped shining? (viewed 44740 times)
  271. How does Astronomy involve Chemistry? (viewed 44689 times)
  272. Could the Universe have expanded faster than the speed of light at the Big Bang? (viewed 44609 times)
  273. Is there a "South Star"? (viewed 44588 times)
  274. Why does the location of sunrise change? (viewed 44587 times)
  275. What is the difference between the "Doppler" redshift and the "gravitational" or "cosmological" redshift? (viewed 44455 times)
  276. What is the best way to see the Milky Way? (viewed 44372 times)
  277. Has there been an experiment that measured speed faster than the speed of light in vacuum? (viewed 44175 times)
  278. What happens to spacetime inside a black hole? (viewed 43959 times)
  279. How would the weather on Earth be different if it were a cube? (viewed 43946 times)
  280. What are the names of the three stars in Orion's belt? (viewed 43498 times)
  281. Was the Sun made in a supernova? (viewed 43328 times)
  282. Why doesn't dark matter fall into a black hole? (viewed 43168 times)
  283. How much longer will the Earth last? (viewed 42965 times)
  284. What is the biggest crater recorded on Earth? (viewed 42947 times)
  285. Why can we see the sun's image before sunrise and after sunset? (viewed 42893 times)
  286. What if the Earth rotated twice as fast? (viewed 42487 times)
  287. Why does the Earth only see one side of the Moon? (viewed 42351 times)
  288. Why do people draw stars with five points? (viewed 42140 times)
  289. Can I buy land on the Moon? (viewed 42101 times)
  290. How do we feel heat? (viewed 42057 times)
  291. Is the Sun always up for exactly 12 hours at the equator? (viewed 42055 times)
  292. Is the Moon hollow? (viewed 41867 times)
  293. What happens when two black holes get too close? (viewed 41865 times)
  294. Could someone travel the universe in his or her own lifetime? (viewed 41675 times)
  295. Is it possible to see the full Moon and the Sun simultaneously in high northern latitudes when the Sun doesn't set? (viewed 41583 times)
  296. What color would Mars be if you were standing on it? (viewed 41542 times)
  297. Why do clocks turn in the opposite direction from the Earth and Moon? (viewed 41505 times)
  298. What is time dilation? (viewed 41483 times)
  299. How do we know that nuclear fusion is still going on in the Sun? (viewed 41306 times)
  300. How can two moons of Saturn share the same orbit? (viewed 41282 times)
  301. How fast does the Earth go at perihelion and aphelion? (viewed 41235 times)
  302. What's the biggest meteorite? (viewed 41200 times)
  303. Do you think it's possible to maintain life on other planets? (viewed 41096 times)
  304. What is the most distant known galaxy? (viewed 41033 times)
  305. Why can't a plane fly slowly and let the Earth pass underneath? (viewed 40998 times)
  306. Can terrestrial planets have rings? (viewed 40957 times)
  307. How do we define distance in an expanding universe? (viewed 40648 times)
  308. Why are Saturn's rings flat? (viewed 40600 times)
  309. Does the Sun have an iron surface? (viewed 40530 times)
  310. What are "blue stragglers" in globular clusters? (viewed 40491 times)
  311. How long would it take for a mini-black hole to eat the Earth? (viewed 40249 times)
  312. How many Astronauts have been in space? (viewed 40118 times)
  313. Who (and when) discovered that the earth's axis is on a 23 degree tilt? (viewed 40066 times)
  314. If a white dwarf is a "dead" star, why is it so hot? (viewed 40008 times)
  315. On which days can I see the Moon in the evening / morning and why is this so? (viewed 39879 times)
  316. Why do pictures of distant galaxies have higher resolution than those of nearby planets? (viewed 39858 times)
  317. Can you see the future as you fall into a black hole? (viewed 39819 times)
  318. Can a person go into a black hole and come out alive? (viewed 39744 times)
  319. What is the typical size of a visible shooting star? (viewed 39615 times)
  320. Are all stars the same? (viewed 39476 times)
  321. Is the Great Wall the largest galaxy cluster? (viewed 39428 times)
  322. What is a dimension? (viewed 39401 times)
  323. Does Mt. Everest cast a shadow on the moon? (viewed 39229 times)
  324. Where do planetary rings come from, and what are they made of? (viewed 39146 times)
  325. How can the universe be "flat"? We're 3D! (viewed 39105 times)
  326. How does night and day work? (viewed 38959 times)
  327. How do we determine the age of the universe? (viewed 38941 times)
  328. Can I communicate faster than light? (viewed 38899 times)
  329. What companies or businesses can astronomers work for? (viewed 38666 times)
  330. What is the speed of gravity? (viewed 38464 times)
  331. What is Earthrise over the Moon? (viewed 38389 times)
  332. What is the approximate GPA needed in High School in Math and Science to be an astronomer? (viewed 38325 times)
  333. How are photons created and destroyed? (viewed 38288 times)
  334. How do we know the Milky Way is a spiral galaxy? (viewed 38147 times)
  335. Where is the supernova remnant that led to our solar system? (viewed 38053 times)
  336. What kind of eyepieces do I need to look at planets? (viewed 38041 times)
  337. If the universe is 15 billion years old, how can it be larger than 15 billion light years across? (viewed 38010 times)
  338. Is there a beginning and an end to a galaxy's life? (viewed 37988 times)
  339. Why are there blue shifted galaxies? (viewed 37924 times)
  340. Why is sea water salty, and not lake water? (viewed 37794 times)
  341. What can I use for fuel in my homemade rocket? (viewed 37743 times)
  342. How big is the universe? (viewed 37725 times)
  343. Is there really a 10th planet? (viewed 37653 times)
  344. Does the Coriolis force determine which way my toilet drains? Does it affect black holes? (viewed 37569 times)
  345. What would happen to the Earth if an asteroid hit the Moon? (viewed 37093 times)
  346. How does the brightness of a star depend on its distance from us? (viewed 37083 times)
  347. Can you describe a day on the job as an astronomer? (viewed 37071 times)
  348. How are planets detected around other stars? (viewed 37007 times)
  349. How many stars can I see? (viewed 36948 times)
  350. How do I tell which planet is which? (viewed 36871 times)
  351. What is the pattern to the distances between each planet and the sun? (viewed 36800 times)
  352. How can I find my age on another planet? (viewed 36673 times)
  353. Why do humans want to go in space? (viewed 36589 times)
  354. Can a lunar and a solar eclipse happen in the same month? When will this happen next? (viewed 36525 times)
  355. What is the significance of the second focus of elliptical orbits of planets in our Solar System? (viewed 36454 times)
  356. Do the Sun's or Earth's magnetic field reverse? (viewed 36361 times)
  357. Will we ever stop having solar eclipses because of the moon's motion away from the Earth? (viewed 36352 times)
  358. How hot is each one of the layers of the sun? (viewed 36276 times)
  359. Why have star signs shifted by one constellation? (viewed 36052 times)
  360. Is Andromeda part of the Milky Way? Where can I find them in the sky? (viewed 35944 times)
  361. Is the Local Group expanding along with the entire Universe? (viewed 35769 times)
  362. How do astronauts communicate with their families from space? (viewed 35669 times)
  363. Who came up with the name "black hole"? (viewed 35567 times)
  364. How can we estimate the number of Earth-like planets in the Galaxy? (viewed 35388 times)
  365. What would happen if two stars collided? (viewed 35206 times)
  366. What was that really big falling star that I saw? (viewed 35058 times)
  367. How do I become both an astronaut and an astronomer? (viewed 35052 times)
  368. Why don't astronomers use everyday units to measure distances (what is an AU or a pc)? (viewed 35001 times)
  369. Is the Earth at the centre of the Universe? (viewed 34935 times)
  370. Is there a simple formula to calculate solar eclipse timings from any position on Earth? (viewed 34913 times)
  371. How is it that we see farther out in space (farther back in time) than in the past? (viewed 34818 times)
  372. When we look back to the Big Bang, why don't we see the universe as a tiny speck of matter? (viewed 34777 times)
  373. How do sunrise and sunset times change with altitude? (viewed 34645 times)
  374. Will the Moon be invisible in 500 million years? (viewed 34520 times)
  375. Why is Uranus tipped on its side? (viewed 34240 times)
  376. Why is our solar system so different from all the others we've found? (viewed 34048 times)
  377. Are Earth and the Moon "twin planets"? (viewed 33978 times)
  378. Is it true that the Sun burns off a billion tons of gas every 5 seconds? (viewed 33943 times)
  379. How dangerous are the asteroids? (viewed 33922 times)
  380. Which American colleges teach astronomy? (viewed 33872 times)
  381. Is the universe really like an expanding balloon? (viewed 33855 times)
  382. Why do constellations look the same after several years even though all the stars are moving? (viewed 33817 times)
  383. Why are there no craters on Earth? Did all the meteorites miss us? (viewed 33478 times)
  384. Can we colonize other planets? (viewed 33441 times)
  385. Is the gravitational force exerted by the Earth on the Moon equal to the centripetal force acting on the Moon? (viewed 33436 times)
  386. Do we see the same stars from above and below the equator? (viewed 33417 times)
  387. Does the Moon look different in the northern and southern hemispheres? (viewed 33381 times)
  388. Why do astronauts in space need to exercise? (viewed 33090 times)
  389. What are quasars made of? (viewed 32901 times)
  390. Can superheavy elements (such as Z=116 or 118) be formed in a supernova? Can we observe them? (viewed 32842 times)
  391. Does the Milky Way spin counter-clockwise? If so, do all spiral galaxies spin in this direction and why? (viewed 32836 times)
  392. How can I calculate distances between stars? (viewed 32809 times)
  393. What is dark matter? (viewed 32625 times)
  394. Why is the time between two successive full moons different from the lunar synodic month? (viewed 32608 times)
  395. What would happen if a human were exposed to space without wearing a spacesuit? (viewed 32580 times)
  396. Why doesn't gravity change the speed of light? (viewed 32567 times)
  397. How big a change in the Earth's orbit would be required to destroy all life? (viewed 32331 times)
  398. Can we see dead stars with the naked eye? (viewed 32126 times)
  399. Is it possible to count the stars? (viewed 32116 times)
  400. How do we measure distances to other stars? (viewed 31994 times)
  401. Is time travel possible using merging black holes? (viewed 31973 times)
  402. Did the speed of light change over the history of the universe? (viewed 31963 times)
  403. How can we tell what the interiors of planets are like? (viewed 31958 times)
  404. What is happening just around the black hole in the center of the Milky Way? (viewed 31933 times)
  405. How do I make a scale model of the Solar System? (viewed 31904 times)
  406. How can we distinguish a star's "real" color from the change in color that we observe due to the star's motion? (viewed 31758 times)
  407. What do "homogeneity" and "isotropy" mean? (viewed 31752 times)
  408. What happens when an antimatter black hole collides with a matter blackhole? (viewed 31639 times)
  409. What happens when you change the mass of a White Dwarf or Neutron Star? (viewed 31425 times)
  410. Are time machines possible? (viewed 31296 times)
  411. How many moles of stars are in the known universe? (viewed 31257 times)
  412. What is the farthest in space that we have gone? (viewed 31177 times)
  413. How are galaxy distances inferred from their recessional velocities? (viewed 31145 times)
  414. Can astronauts produce water in space? (viewed 31040 times)
  415. Will the seasons change due to precession? (viewed 31039 times)
  416. How was the starting point for the Julian Date system chosen? (viewed 31037 times)
  417. How can we know that there are other galaxies if we cannot leave ours? (viewed 30842 times)
  418. How do we know if the universe will keep expanding forever? (viewed 30801 times)
  419. Aren't jobs in astronomy scarce? (viewed 30575 times)
  420. Why does the SETI project search for radio signals? (viewed 30480 times)
  421. Why do we study black holes? (viewed 30420 times)
  422. When are there 5 Sundays in February? (viewed 30411 times)
  423. Is there any limitation to what a black hole can "suck" in? (viewed 30408 times)
  424. How long does it take the Big Dipper to move in the sky? (viewed 30337 times)
  425. What are the closest and/or brightest stars? (viewed 30286 times)
  426. How can I tell if the rock I found is a meteorite? (viewed 30256 times)
  427. Do astronomers believe in astrology? (viewed 30177 times)
  428. Do you believe in UFOs? (viewed 30125 times)
  429. What's that dark spot on the Sun? (viewed 30091 times)
  430. Why are telescopes located in remote places? (viewed 30073 times)
  431. Can you use an infinite line of reflectors to send light to the edge of the Universe? (viewed 29960 times)
  432. Did I see the Aurora Borealis as a child? (viewed 29947 times)
  433. Why do most moons orbit their planets at the equator? (viewed 29847 times)
  434. What are the facts about the Star of Bethlehem? (viewed 29841 times)
  435. Wouldn't the Big Bang theory be considered a hypothesis and not a theory? (viewed 29834 times)
  436. What are the atmospheres of Mars and Pluto like? (viewed 29631 times)
  437. Don't tachyons travel faster than light? (viewed 29610 times)
  438. What does the term "visible universe" mean? (viewed 29525 times)
  439. Could you tell me about the life cycle of galaxies? (viewed 29503 times)
  440. Why do so many of the world's UFO sightings happen in America? (viewed 29499 times)
  441. What colors are visible through an amateur telescope? (viewed 29443 times)
  442. Could an astronaut or satellite fall into a black hole that we didn't know about? (viewed 29403 times)
  443. What is the origin of the stellar classification system "OBAFGKM"? (viewed 29372 times)
  444. How can geometry be different in space? (viewed 29091 times)
  445. Why are the compositions of comets and asteroids different? (viewed 29087 times)
  446. Was I hit by a meteorite? (viewed 28963 times)
  447. How are galaxies named? (viewed 28960 times)
  448. What's the best thing about being an astronomer? (viewed 28935 times)
  449. Has anyone made a map of the Milky Way? (viewed 28924 times)
  450. How do astronomers measure the radius of a star? (viewed 28906 times)
  451. Can two lunar eclipses occur in the same month? (viewed 28822 times)
  452. How do asteroids, meteors and comets disappear? (viewed 28603 times)
  453. How do I explain to my children why the Moon has phases? (viewed 28352 times)
  454. How much time do astronomers spend looking through telescopes? (viewed 28247 times)
  455. Will winter and summer constellations change due to abnormal warmth or cold on Earth? (viewed 28226 times)
  456. How can we see galaxies if their stars are so faint? (viewed 28207 times)
  457. Do asteroids hit the sun? (viewed 28166 times)
  458. Can a human give birth in space? (viewed 28165 times)
  459. How are galaxies and solar systems similar? (viewed 28030 times)
  460. Have there been other Big Bangs before? (viewed 28002 times)
  461. Do the magnitudes and colors of stars ever change? (viewed 27916 times)
  462. How will the two black holes that are going to collide affect Earth? (viewed 27840 times)
  463. Is there a project I can do on black holes? (viewed 27748 times)
  464. How close do you have to come to the Earth to be influenced by its gravity? (viewed 27704 times)
  465. How can we measure distances to more stars? (viewed 27603 times)
  466. Is there oxygen in the atmospheres of other planets? (viewed 27536 times)
  467. Can life exist on the recently discovered extrasolar planets? (viewed 27502 times)
  468. Could you escape from a black hole if you were able to go faster than the speed of light? (viewed 27498 times)
  469. Is the Milky Way a collision of two galaxies? (viewed 27458 times)
  470. Which part of the sky did the famous 'wow' signal originate from? (viewed 27458 times)
  471. What causes gamma ray bursts? (viewed 27405 times)
  472. How do scientists slow light down? (viewed 27396 times)
  473. What supernova created the Crab nebula? (viewed 27287 times)
  474. How close does a supernova need to be to damage the Earth's environment? (viewed 27280 times)
  475. Is it worthwhile to continue the search for extraterrestrial life? (viewed 27250 times)
  476. Can "tired light theory" explain the observed redshifts of galaxies? (viewed 27181 times)
  477. Can double stars have planets? (viewed 27180 times)
  478. Is infinite temperature possible? (viewed 27131 times)
  479. Why did the Pioneer and Voyager take only 2 years to reach Jupiter, while Galileo and Cassini took more than 5 years? (viewed 27129 times)
  480. Do we know everything about the Sun? (viewed 27039 times)
  481. Can one star orbit another? (viewed 26938 times)
  482. Can astronauts play musical instruments in space? (viewed 26797 times)
  483. When did people discover that the Sun is a star? (viewed 26763 times)
  484. What will happen to the Milky Way in the future? (viewed 26760 times)
  485. How far does a galaxy extend? (viewed 26736 times)
  486. What is sidereal time? (viewed 26724 times)
  487. Are planetary nebulae the result of supernovae? (viewed 26658 times)
  488. Which way does the sun travel in the southern hemisphere? (viewed 26645 times)
  489. How do I polar align my telescope? (viewed 26616 times)
  490. Is there sound coming from the Sun? (viewed 26579 times)
  491. What type of energy does a black hole have? (viewed 26530 times)
  492. What's the object I saw that moved across the sky and then got very bright? (viewed 26527 times)
  493. What is the farthest Northern Latitude in which the Magellanic Clouds can be seen? (viewed 26519 times)
  494. What is "nothing", from a scientific point of view? (viewed 26504 times)
  495. Why is the shadow on the Moon the shape it is? (viewed 26500 times)
  496. What is a Cepheid variable? (viewed 26489 times)
  497. How different would the night sky have looked in 40,000 B.C.? (viewed 26489 times)
  498. Is there such a thing as hyperspace? (viewed 26398 times)
  499. What happens to the material that has been sucked into a black hole? (viewed 26345 times)
  500. Why do the explosions of Type Ia supernovae have a more predictable spectrum than those of regular Type II supernovae? (viewed 26280 times)
  501. What is our galaxy's halo made of, and how was it formed? (viewed 26280 times)
  502. How will a change in the speed of light affect the evolution of the Universe? (viewed 26173 times)
  503. How big is the Hubble Ultra Deep Field image? (viewed 26151 times)
  504. When unmanned spacecraft accelerate in space, what causes them to slow down? (viewed 26130 times)
  505. Why do we assume that the universe is homogeneous? (viewed 26080 times)
  506. If we invented special suits could we ever go to the sun? (viewed 26075 times)
  507. What is the difference between homogeneity and isotropy? (viewed 26066 times)
  508. How do we know that sunspots are associated with the Sun's magnetic field? (viewed 25969 times)
  509. How do we know what parameters to use when simulating the collision of the Milky Way and Andromeda? (viewed 25896 times)
  510. What happened to the girl who named Pluto? (viewed 25879 times)
  511. What calculations go into predicting eclipses? (viewed 25860 times)
  512. How are asteroid compositions and classifications determined? (viewed 25828 times)
  513. Are there any dark stars or dark galaxies made of dark matter? (viewed 25802 times)
  514. Can I see a quasar? (viewed 25742 times)
  515. Is there a list of the sizes of different kinds of stars? (viewed 25662 times)
  516. How many sunspots can the Sun have at once? (viewed 25620 times)
  517. Would the biggest airplanes cause tsunamis if they crashed? (viewed 25619 times)
  518. Can I see details on Venus? (viewed 25616 times)
  519. Why are there more maria on the near side of the Moon? (viewed 25614 times)
  520. Was Stonehenge built to mark solar phenomena? (viewed 25528 times)
  521. What happened to all the black holes that were around in the early universe? (viewed 25528 times)
  522. Can any comparison be made between spiral galaxies and hurricanes? (viewed 25527 times)
  523. What process would bring about a quark star? (viewed 25494 times)
  524. If clocks run slow in a gravitational field, how can we know the true age of the Solar System and Universe? (viewed 25409 times)
  525. Why are telescopes kept in cold conditions? (viewed 25364 times)
  526. What's so exciting about the new planet around 55 Cancri? (viewed 25350 times)
  527. Did a giant impact cause the Dark Ages? (viewed 25346 times)
  528. What equipment do I need for astrophotography? (viewed 25286 times)
  529. How is it proved that the Universe is expanding? (viewed 25269 times)
  530. Have gravitational waves been proven to exist? (viewed 25263 times)
  531. What is a Dyson Sphere? (viewed 25205 times)
  532. How do unmanned space probes avoid running into things? (viewed 25182 times)
  533. If the Universe was infinitely dense at the Big Bang, why didn't time stand still? (viewed 25105 times)
  534. Does Cerenkov radiation travel faster than light? (viewed 25098 times)
  535. Why are there active volcanos on Io? (viewed 25034 times)
  536. Is there any possibility that the Solar System or the Universe is in a black hole? (viewed 24909 times)
  537. Can you give me advice on buying a telescope? (viewed 24829 times)
  538. How can I contribute to science as an amateur astronomer? (viewed 24826 times)
  539. How long do supernova remnants last? (viewed 24824 times)
  540. How can we compare dark matter and dark energy? (viewed 24719 times)
  541. Why is it important to study meteorites? (viewed 24676 times)
  542. How big was the Sun when it first "fired up"? (viewed 24659 times)
  543. How do solar flares affect airline pilots? (viewed 24609 times)
  544. Why do photos of space taken from space never show any stars? (viewed 24592 times)
  545. What caused Shoemaker-Levy 9 to split up? (viewed 24580 times)
  546. Could we send a space mission to a comet? (viewed 24577 times)
  547. Why doesn't NASA build rotating spacecraft to simulate gravity? (viewed 24557 times)
  548. Why doesn't light from distant galaxies reach us instantaneously? (viewed 24542 times)
  549. Are the asteroids the remains of a planet which broke apart? (viewed 24519 times)
  550. How are sunspots formed? (viewed 24454 times)
  551. Can I build an instrument to measure the size of the Sun and of the Moon? (viewed 24424 times)
  552. How does the Earth compare in size to the entire universe at the present epoch? (viewed 24390 times)
  553. Could a different theory of gravity explain the dark matter mystery? (viewed 24347 times)
  554. Where does the kinetic energy of infalling bodies come from? (viewed 24315 times)
  555. Did I really hear a meteor? (viewed 24231 times)
  556. Could we be seeing dead stars? (viewed 24228 times)
  557. As the universe expands, why don't galaxies get stretched out? (viewed 24217 times)
  558. How many comets are currently orbiting our sun? (viewed 24098 times)
  559. Why can't relative velocities add up to more than the speed of light? (viewed 24097 times)
  560. Can you tell time by the Big Dipper? (viewed 24036 times)
  561. Do the Earth's magnetic poles ever change places? (viewed 24001 times)
  562. Do unmanned spacecraft like Voyager travel in straight lines? (viewed 23915 times)
  563. Why is the Hubble Space Telescope in space? (viewed 23908 times)
  564. How could galaxies have gotten so far away in only 15 billion years? (viewed 23882 times)
  565. Would extraterrestrial civilizations know that there is life on Earth? (viewed 23840 times)
  566. How is the Cepheid yardstick validated? (viewed 23833 times)
  567. How do we know that superclusters are the largest structures in the universe? (viewed 23821 times)
  568. Do galaxies orbit around anything? (viewed 23779 times)
  569. How powerful are quasars? (viewed 23769 times)
  570. Did time go slower just after the Big Bang? (viewed 23739 times)
  571. Why are stars of different masses? (viewed 23711 times)
  572. What kind of instruments are used to detect extrasolar planets? (viewed 23707 times)
  573. Are there any new craters on the moon? (viewed 23643 times)
  574. How do I become an astronomical artist? (viewed 23608 times)
  575. Can supernovae hinder the formation of life in galaxies? (viewed 23568 times)
  576. How do astronomers observe the Sun's interior? (viewed 23564 times)
  577. What would happen if there was a collision between two white dwarfs? (viewed 23521 times)
  578. Do similar laws of physics throughout the Universe imply that all life must be like life on Earth? (viewed 23494 times)
  579. How are astronomy and poetry linked? (viewed 23492 times)
  580. Could there have been multiple Big Bangs at different places in the universe? (viewed 23483 times)
  581. How do planets capture satellites? (viewed 23473 times)
  582. What kind of telescope should I use for astrophotography? (viewed 23435 times)
  583. Could dark energy come from matter anti-matter pairs forming spontaneously and then annihilating? (viewed 23315 times)
  584. Why is NASA shutting down the Hubble Space Telescope? (viewed 23215 times)
  585. How can you tell if a crescent moon is preceding or following a new-moon phase? (viewed 23179 times)
  586. Can I listen to the SETI@home radio signal? (viewed 23177 times)
  587. Does the Sun have any heavy elements? (viewed 23079 times)
  588. A line drawn perpendicular to a line through the tips of the horns of the crescent moon doesn't point to the Sun! Why not? (viewed 23056 times)
  589. Can the theory of formation of the solar system explain all the observables? (viewed 23023 times)
  590. What class of spiral galaxy is the Milky Way? (viewed 23007 times)
  591. Why do spacecraft need heat shields coming back to Earth but not leaving? (viewed 22979 times)
  592. Where was the water in the big bang? (viewed 22935 times)
  593. Could we send a manned mission to the outer planets? (viewed 22922 times)
  594. Will we discover an 11th planet? What would it be called? (viewed 22906 times)
  595. Are the properties of extrasolar planets known? (viewed 22869 times)
  596. How can water be chemically trapped in rocks? (viewed 22816 times)
  597. What month was it when Odysseus saw Orion in 1000BC? (viewed 22680 times)
  598. Is it possible for amateurs to do optical interferometry? (viewed 22673 times)
  599. What makes a satellite geosyncronise itself with Earth's orbit? (viewed 22565 times)
  600. Why does the apparent density of galaxies drop off at larger distances? (viewed 22460 times)
  601. Would a planet near the galactic center have a brighter night sky? (viewed 22391 times)
  602. Why does one side of Mars look more catastrophic than the other? (viewed 22367 times)
  603. Do stars' orbits in galaxies obey Kepler's Laws? (viewed 22332 times)
  604. Why are accretion disks flat? (viewed 22286 times)
  605. How can the Sun have such a strong gravitational field if it's made of gasses? (viewed 22270 times)
  606. Why was the Platonic year named after Plato? (viewed 22059 times)
  607. Can other terrestrial moons be (or have been) stable? (viewed 22029 times)
  608. What would the Big Crunch look like to an observer on Earth? (viewed 21936 times)
  609. What is the solar cycle? (viewed 21924 times)
  610. How are supernovae discovered? (viewed 21867 times)
  611. What is meant by "stopping down a telescope"? (viewed 21847 times)
  612. Why doesn't the hydrogen on Jupiter explode? (viewed 21787 times)
  613. Does inflation allow for an infinite number of universes? (viewed 21751 times)
  614. Can a black hole come back to the visual universe through a "little bang"? (viewed 21739 times)
  615. Could our position in the universe affect our perceptions of the expansion? (viewed 21646 times)
  616. Can planets collide with one another? (viewed 21628 times)
  617. If photons have zero mass, why do they feel the effects of gravity? (viewed 21592 times)
  618. Did I find a rock that came from the Moon? (viewed 21528 times)
  619. Will I be able to see the shadow of the Moon streaking towards me in a total solar eclipse? (viewed 21495 times)
  620. Have astronomers observed any phenomena that could be produced by extraterrestrial civilizations? (viewed 21492 times)
  621. What is the SU(3) quark model? (viewed 21450 times)
  622. Do constellations looks the same from space? (viewed 21381 times)
  623. Can gravitational lensing from intervening galaxies cause the observed ripples in the Cosmic Microwave Background? (viewed 21363 times)
  624. Does a photon observe other photons moving past it at the speed of light? (viewed 21281 times)
  625. How can we find galaxies behind the Milky Way? (viewed 21214 times)
  626. Why is the WMAP picture of the CMB an ellipse? (viewed 21163 times)
  627. Could photons be dark matter? (viewed 21156 times)
  628. How fast do particles travel in space? (viewed 21138 times)
  629. What's new with the Big Bang? (viewed 21105 times)
  630. Is it possible to build a cheap device to measure declination? (viewed 21004 times)
  631. Why search for only Earth-like life on other planets? (viewed 20997 times)
  632. Why can we have solar eclipses? (viewed 20986 times)
  633. What are collections of galaxies called? (viewed 20974 times)
  634. Where can I find information on the moons of other planets? (viewed 20936 times)
  635. If comets are boiling away, why are there any left? (viewed 20927 times)
  636. How much power is contained in a beam of light? (viewed 20924 times)
  637. Why do some eclipses take longer than others? (viewed 20810 times)
  638. Why is pressure broadening greater in low mass stars than in high mass stars? (viewed 20713 times)
  639. Did the Sumerians measure precession? (viewed 20680 times)
  640. How did Mars get so dusty? (viewed 20652 times)
  641. What are the boundaries of the constellations? (viewed 20588 times)
  642. What kinds of star clusters are there? (viewed 20576 times)
  643. What would an "open geometry" for the universe look like? (viewed 20550 times)
  644. How do photons from distant objects maintain enough energy to reach us? (viewed 20408 times)
  645. How do bars form in spiral galaxies? (viewed 20335 times)
  646. Why don't astronauts sublimate in space? (viewed 20335 times)
  647. Why aren't discoveries of extrasolar planets reported on the news? (viewed 20291 times)
  648. Why is the Cosmic Microwave Background not absorbed by interstellar hydrogen? (viewed 20284 times)
  649. How do astronomers come up with their facts? (viewed 20281 times)
  650. Do electrons age? (viewed 20171 times)
  651. Can HST see the Oort cloud? (viewed 20099 times)
  652. Can we make a movie of the Milky Way galaxy's rotation? (viewed 20096 times)
  653. Will astronauts ever be able to go ice-skating on Europa? (viewed 20039 times)
  654. How does melting a material reset its radioactive clock? (viewed 20029 times)
  655. Why don't all neutron stars become pulsars? (viewed 20023 times)
  656. How long is twilight on the Moon? (viewed 19975 times)
  657. Can the Space Shuttle abort and return to Earth before reaching orbit? (viewed 19968 times)
  658. What happens to the helium formed in the sun? (viewed 19946 times)
  659. How does the color index of a star relate to its actual color? (viewed 19923 times)
  660. Why is it called astronomy when all the other sciences end in -ology? (viewed 19919 times)
  661. Does the shuttle worry about space junk? (viewed 19884 times)
  662. Where can I see Newton's original reflecting telescope? (viewed 19877 times)
  663. How do you classify galaxies? (viewed 19807 times)
  664. How can we understand the meaning of large numbers like "a million million?" (viewed 19782 times)
  665. Are black holes spherical? (viewed 19779 times)
  666. Why do supernova remnants look like rings rather than spheres? (viewed 19756 times)
  667. If nothing can escape a black hole, why do some black holes have jets? (viewed 19726 times)
  668. What causes a particle to decay? (viewed 19651 times)
  669. What is the best time of the year to see eclipses? (viewed 19607 times)
  670. Why doesn't SETI concentrate its observations to the nearby stars and the solar systems that we are discovering? (viewed 19559 times)
  671. Will the next generation telescope OWL be able to detect an Earth like extrasolar planet? (viewed 19515 times)
  672. How can I nominate myself for a Nobel Prize in Physics? (viewed 19466 times)
  673. How long has humanity known that we live in a galaxy similar to others in the Universe? (viewed 19430 times)
  674. Will the Leonid meteor shower go away? (viewed 19351 times)
  675. What are "curled" dimensions? (viewed 19277 times)
  676. Do asteroids ever do anything good in the Solar System? (viewed 19243 times)
  677. What would happen if you went back in time and killed your grandmother? (viewed 19237 times)
  678. How does interferometry work? (viewed 19152 times)
  679. Is light of different colors affected differently by gravity? (viewed 19142 times)
  680. How do distant galaxies differ from those nearby? (viewed 19090 times)
  681. What kind of interference must astronomers contend with when observing? (viewed 19086 times)
  682. Does the temperature of matter increase as it is accelerated to relativistic speeds? (viewed 19008 times)
  683. What was that eclipse I saw in the sky? (viewed 18990 times)
  684. Why will fusion wait until hydrogen is gone before starting to fuse heavier atoms? (viewed 18965 times)
  685. Wouldn't the vast distances of space distort SETI signals into unintelligeble forms? (viewed 18954 times)
  686. How do we find out about the star formation histories of galaxies? (viewed 18903 times)
  687. How can I watch the Perseid meteor shower? (viewed 18865 times)
  688. What do stellar classifications mean? (viewed 18822 times)
  689. Why aren't accretion disks around giant stars as hot as accretion disks around black holes? (viewed 18815 times)
  690. Can astronomers observe anything when the moon is full? (viewed 18759 times)
  691. Do we really observe the edges of galaxies at different epochs? (viewed 18731 times)
  692. How are astronauts trained for weightlessness? (viewed 18716 times)
  693. How do supernovae show us that the Universe's expansion is accelerating? (viewed 18711 times)
  694. When measuring the expansion of the universe, do astronomers consider that they're seeing how galaxies moved long ago, not today? (viewed 18710 times)
  695. Can you tell me the characteristics of W, R, N and S type stars? (viewed 18663 times)
  696. What is the three-body problem? (viewed 18630 times)
  697. What time is sunrise/sunset or moonrise/moonset at my location? (viewed 18552 times)
  698. If the universe is "bounded" today, could it one day become "unbounded"? (viewed 18381 times)
  699. Will the diameter of a cluster of galaxies change with redshift? (viewed 18329 times)
  700. Does lunar gardening really work? (viewed 18258 times)
  701. Is cosmic expansion happening on microscopic scales? (viewed 18208 times)
  702. Could neutrinos be dark matter? (viewed 17930 times)
  703. How can I find out if the new moon has been sighted? (viewed 17918 times)
  704. Do we have to worry about relativity when studying galactic objects? (viewed 17790 times)
  705. What kinds of cancer research have been done in space? (viewed 17662 times)
  706. Could the Universe's dark matter be made up of black holes? (viewed 17571 times)
  707. How does a star take mass from another star? (viewed 17536 times)
  708. The Moon and Sun are the same apparent size in the sky. The Moon is moving away from us at 3.8 centimeters/year. Isn't it improbable that we live in an epoch in which they appear the same size in the sky? (viewed 17383 times)
  709. How can you tell the difference between single and multiple extrasolar planets? (viewed 17287 times)
  710. What is Hot Dark Matter theory? (viewed 17274 times)
  711. How do we know the density of some extrasolar planets? (viewed 17229 times)
  712. Is it a coincidence that we can have total solar eclipses? Are there other planets which also have them? (viewed 17181 times)
  713. What is the photoelectric effect? Why can't multiple low-frequency photons free an electron? (viewed 17164 times)
  714. Is the green flash real? (viewed 17064 times)
  715. How does libration allow us to see more than 50% of the Moon? (viewed 16762 times)
  716. How has light from 13 billion years ago not passed us by? (viewed 16741 times)
  717. How can observations of the distant universe prove that the expansion is accelerating *now*? (viewed 16699 times)
  718. Do binary or triple star systems form together? (viewed 16626 times)
  719. Is light blueshifted when it is gravitationally lensed? (viewed 16575 times)
  720. Can we prove that the Moon isn't hollow? (viewed 16572 times)
  721. What do meteorites tell us about life on other planets? (viewed 16556 times)
  722. No matter how fast the universe is expanding, shouldn't gravity eventually make it recollapse? (viewed 16507 times)
  723. If the sun went out and our atmosphere froze solid, what color would it be? (viewed 16490 times)
  724. Why is it easier to see a star if you look slightly to the side? (viewed 16455 times)
  725. What percent of the time can astronomers observe without interference from the Moon? (viewed 16228 times)
  726. What was different on Mars in the past to allow liquid water to be present? (viewed 16044 times)
  727. Why don't skydivers burn up like meteors? (viewed 16030 times)
  728. Could matter-anti-matter repulsion power the expansion of the universe? (viewed 15987 times)
  729. Why doesn't the ammonia and methane in Jupiter's atmosphere sink into the core? (viewed 15983 times)
  730. When will Hale-Bopp return? (viewed 15867 times)
  731. How do we detect incoming meteorites? (viewed 15844 times)
  732. Has anyone ever seen a star "turn on"? (viewed 15791 times)
  733. Are there any 'lonely galaxies'? (viewed 15636 times)
  734. Why are craters round? (viewed 15559 times)
  735. Can the sun rise from the west on Mars? (viewed 14816 times)
  736. During close approaches, can Mars appear in our sky as large as the Moon? (viewed 14812 times)
  737. How are planets affected by the Hot Ionised Medium? (viewed 14645 times)
  738. What are the largest radio wavelengths observed from radio sources in the sky? (viewed 14347 times)
  739. Why was Mir burnt up in the atmosphere? (viewed 14238 times)
  740. How can we discern different galaxies/clusters along the same line of sight? (viewed 14068 times)
  741. Why does Titan, in spite of being smaller than Mars, have an atmosphere more dense than Earth's? (viewed 14031 times)
  742. Can we harvest H & O from space to make water? (viewed 13983 times)
  743. What is the relationship between the width of a star trail on a photo and the star's intensity? (viewed 13676 times)
  744. What happens to the Earth as the moon gets farther away and will it ever go away entirely? (viewed 13360 times)
  745. What is between the Oort cloud and the closest star? (viewed 13218 times)
  746. Could a planetary system survive if its star merged with another, or if its star went supernova? (viewed 12305 times)
  747. Why is the Moon higher in the sky in winter and lower in the summer? (viewed 12236 times)
  748. Are there solar tides? (viewed 12175 times)
  749. Is the Moon always visible during winter on the North Pole? (viewed 11983 times)
  750. Is Earth-moon tidal friction causing global warming? (viewed 11907 times)
  751. Does weightlessness affect hunger? (viewed 11839 times)
  752. Is the moon spherical? (viewed 11800 times)
  753. Do planets radiate noise? (viewed 11666 times)
  754. Is dark energy affected by black holes? (viewed 11548 times)
  755. Where are the protons and electrons in a Neutron Star? (viewed 11548 times)
  756. What would happen if a nuclear-powered shuttle exploded? (viewed 10933 times)
  757. Wait, I'm still confused why information can't travel faster than the speed of light. (viewed 10917 times)
  758. Will the Pioneer and Voyager probes ever leave the Milky Way? (viewed 10155 times)
  759. Will Comet Elenin (C/2010 X1) affect the Earth on its close approach in Fall 2011? (viewed 10028 times)
  760. Do more meteorites fall at low latitudes? (viewed 9972 times)
  761. What are the possible ends of the universe? (viewed 9941 times)
  762. Did the Moon or planets form in a manner similar to that of Earth? (viewed 9879 times)
  763. If there are infinity universes, will every thing that is possible happen? (viewed 9706 times)
  764. Is it sensible to consider terraforming Mars? (viewed 9575 times)
  765. What color are meteors? (viewed 9431 times)
  766. Where is everybody? (viewed 8827 times)
  767. Why do astronomers use telescopes? (viewed 8766 times)
  768. Why does Mars have a dusty atmosphere? (viewed 8675 times)
  769. Does the singularity in a black hole create a new Universe? (viewed 8428 times)
  770. The naming of Mars (viewed 8387 times)
  771. If I were traveling through space, could I see distant galaxies with my own eyes? (viewed 8385 times)
  772. Is the reddish dust of Mars biogenic? (viewed 8377 times)
  773. Where is the Spitzer Space Telescope? (viewed 7693 times)
  774. When will humans travel to Mars and revisit the Moon? (viewed 7291 times)
  775. How likely is it for a planet to transit its star? (viewed 7208 times)
  776. What causes the aurora? (viewed 7028 times)
  777. Does the particles involved in a star's final core collapse travel faster than the speed of light? (viewed 6632 times)
  778. When is the best time to observe zodiacal light? (viewed 6529 times)
  779. How did a transit of Venus provide astronomers with the first measurement of the Earth-Sun distance? (viewed 5789 times)
  780. Can the Sun be closer to the Earth than any planet is to Earth? (viewed 5334 times)
  781. Cosmologists say the expansion of the universe is accelerating, what is driving this? (viewed 4466 times)
  782. Can we hear sound on Titan? (viewed 4181 times)
  783. Does the direction of the moon's crescent change through the night? (viewed 4034 times)
  784. What do all the angles in a table for a planet's orbit mean? (viewed 3905 times)
  785. How do I maximize my chances of seeing shooting stars? (viewed 3439 times)
  786. Are exoplanets real? (viewed 2894 times)
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