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 2149726 times)
  2. What color is each planet? (viewed 949404 times)
  3. At what speed does the earth move around the sun? (viewed 615885 times)
  4. Is the Moon moving away from the Earth? When was this discovered? (viewed 591007 times)
  5. How far is each planet from Earth? (viewed 488412 times)
  6. When will Halley's Comet return? (viewed 440749 times)
  7. How long does it take for the Sun's light to reach us? (viewed 403983 times)
  8. Why do the planets orbit the sun? (viewed 399406 times)
  9. How many stars are there in our Galaxy (Milky Way)? (viewed 395181 times)
  10. What is the universe expanding into? (viewed 381535 times)
  11. How do you measure the distance between Earth and the Sun? (viewed 359901 times)
  12. Why do stars twinkle? (viewed 328473 times)
  13. Which planets have rings? (viewed 327610 times)
  14. Does the Moon rotate? Are there other moons that always keep one face toward their planet? (viewed 309391 times)
  15. Can you hear sounds in space? (viewed 302299 times)
  16. How do I build a model rocket? (viewed 294689 times)
  17. What are the different kinds of astronomers? (viewed 279512 times)
  18. What color is Venus? (viewed 278905 times)
  19. What is a white hole? (viewed 273799 times)
  20. What is that ring (or rainbow) around the moon? (viewed 249518 times)
  21. What is the life cycle of a star? (viewed 249037 times)
  22. What are the names of the earth, moon, sun, and solar system? (viewed 246441 times)
  23. What makes the Earth rotate? (viewed 244129 times)
  24. What are shooting stars? (viewed 237267 times)
  25. Can artificial gravity be created in space? (viewed 224666 times)
  26. How do we know the age of the Universe and the Earth? (viewed 224414 times)
  27. What is the largest star? (viewed 223432 times)
  28. Is the universe expanding faster than the speed of light? (viewed 217870 times)
  29. Why do planets rotate? (viewed 217626 times)
  30. What do astronauts eat in space? Can they grow food? (viewed 217232 times)
  31. How does the location of sunrise and sunset change throughout the year? (viewed 212539 times)
  32. How can we see the Milky Way if we are inside it? (viewed 195026 times)
  33. Where did the name 'Earth' come from? (viewed 184463 times)
  34. How does the position of Moonrise and Moonset change? (viewed 183394 times)
  35. Why is a day divided into 24 hours? (viewed 183306 times)
  36. What would happen if we did not have a Moon? (viewed 181278 times)
  37. Why isn't the sky bright at night if the universe has so many stars? (viewed 177241 times)
  38. How many Earths fit into the Sun? (viewed 175376 times)
  39. Why do airplanes take longer to fly West than East? (viewed 173443 times)
  40. When was the last time all 9 planets were aligned? (viewed 170181 times)
  41. Who named the planets and who decides what to name them? (viewed 170002 times)
  42. Why are the Moon and Sun sometimes orange or red? (viewed 163457 times)
  43. How can I find the star I have "bought"? (viewed 157912 times)
  44. Is the distance from the Earth to the Sun changing? (viewed 155939 times)
  45. What is at the end of the Universe? (viewed 154859 times)
  46. Is Pluto a planet? (viewed 153128 times)
  47. How much money is spent on space exploration? (viewed 150327 times)
  48. What is a nova? (viewed 148722 times)
  49. Does your weight change between the poles and the equator? (viewed 144474 times)
  50. How do astronauts take baths and use restrooms in space? (viewed 140214 times)
  51. Can we feel the Earth spin? (viewed 137856 times)
  52. What direction do planets rotate? (viewed 134667 times)
  53. Why are there both high and low tides? (viewed 133009 times)
  54. Do stars move in the sky? (viewed 132399 times)
  55. Is the Sun expanding? Will it ever explode? (viewed 132121 times)
  56. What is the largest galaxy? (viewed 128301 times)
  57. Why do all the planets orbit in the same plane? (viewed 127851 times)
  58. How many known galaxies are there? (viewed 127242 times)
  59. What are the advantages and disadvantages of using a telescope in space? (viewed 127153 times)
  60. What is the physical difference between a star and a planet? (viewed 125309 times)
  61. How are light and heavy elements formed? (viewed 122207 times)
  62. Can I buy a star? (viewed 121241 times)
  63. Why do planets have elliptical orbits? (viewed 119200 times)
  64. Are there telescopes that can see the flag and lunar rover on the Moon? (viewed 118168 times)
  65. Why hasn't NASA gone back to the moon? (viewed 117930 times)
  66. Will the sun go supernova in six years and destroy Earth (as seen on Yahoo)? (viewed 117555 times)
  67. What is the significance of the Tropic of Cancer, Tropic of Capricorn, Arctic Circle and Antarctic Circle? (viewed 116688 times)
  68. Who first measured the speed of light? (viewed 116488 times)
  69. How do stars move in the Galaxy? (viewed 115993 times)
  70. Does the Sun have a scientific name? (viewed 115922 times)
  71. What happens when galaxies collide? (viewed 114523 times)
  72. How do rockets work? (viewed 114065 times)
  73. What is the hottest time of day? (viewed 112835 times)
  74. Does evolution contradict the second law of thermodynamics? (viewed 111763 times)
  75. What is the size of the Solar System? (viewed 111611 times)
  76. What would happen if an impact caused Earth to stop rotating? (viewed 110700 times)
  77. What do astronauts do all day in the International Space Station? (viewed 110631 times)
  78. How much money do astronomers make? (viewed 110600 times)
  79. How do you calculate the lifetime of the Sun? (viewed 110160 times)
  80. What will happen to life on Earth when the Sun becomes a red giant? (viewed 109931 times)
  81. What was there before the Big Bang and what is there outside of our universe? (viewed 108781 times)
  82. Will the magnetic field of the Earth reverse its direction in the future? Will this cause problems? (viewed 108573 times)
  83. What elements make up the Sun? (viewed 108475 times)
  84. What is the observational difference between a star and a planet? (viewed 108190 times)
  85. What are constellations used for? (viewed 108063 times)
  86. When is the next comet due to arrive? (viewed 108061 times)
  87. What would happen if the gravity on Earth was suddenly turned off? (viewed 108028 times)
  88. Does gravity vary across the surface of the Earth? (viewed 107002 times)
  89. How long does a solar eclipse last? (viewed 106796 times)
  90. Do black holes die? If so how? (viewed 106614 times)
  91. How many constellations are there? (viewed 105753 times)
  92. What's the difference between astronomy and astrology? (viewed 104682 times)
  93. Does the Sun rotate? (viewed 103504 times)
  94. Why do different stars appear with seasons? (viewed 102272 times)
  95. How many meteorites hit Earth each year? (viewed 101747 times)
  96. Does the Sun move around the Milky Way? (viewed 100945 times)
  97. What kind of schooling is necessary to become an astronomer? (viewed 100409 times)
  98. Which planet is most similar to Earth? (viewed 99490 times)
  99. What is apparent magnitude? (viewed 99035 times)
  100. Is there a proof that Earth moves? (viewed 95038 times)
  101. What is the difference between a "star" and a "sun"? (viewed 94998 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 94768 times)
  103. How do astronomers use math in their jobs? (viewed 94695 times)
  104. How can a star burn with no oxygen? (viewed 93178 times)
  105. Where did the Universe come from? (viewed 93011 times)
  106. Why is the Universe flat and not spherical? (viewed 92863 times)
  107. Does the Sun orbit the Earth as well as the Earth orbiting the Sun? (viewed 92840 times)
  108. Why are stars and planets round? (viewed 92805 times)
  109. How critical is the Earth-Sun distance in maintaining our average temperatures on Earth? (viewed 92516 times)
  110. What are the requirements for being a planet? (viewed 92329 times)
  111. Why is the Moon so bright? (viewed 91823 times)
  112. What is a singularity? (viewed 91794 times)
  113. What makes the wind? (viewed 91303 times)
  114. What would happen if an asteroid 10 kilometers across hit the Earth? (viewed 90355 times)
  115. Have astronomers discovered Earth's second moon? (viewed 88991 times)
  116. Since Earth is spinning, why do we land in the same place when we jump or fall? (viewed 86302 times)
  117. Why does the Earth tilt back and forward once a year? (viewed 86207 times)
  118. What are RA and DEC? (viewed 86080 times)
  119. Where does the name "Milky Way" come from? (viewed 85191 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 84108 times)
  121. How many stars are born and die each day? (viewed 83761 times)
  122. What would happen if Earth had more than one moon? (viewed 82720 times)
  123. Why is the moon in a different place every night? (viewed 82537 times)
  124. Why aren't there any green stars? (viewed 81059 times)
  125. How do we weigh objects in space? (viewed 79699 times)
  126. How are galaxies formed? (viewed 79349 times)
  127. What kind of rock is the moon made of? (viewed 79260 times)
  128. Did astronauts really go to the Moon, or is it a hoax? (viewed 79101 times)
  129. Will the Sun become a black hole one day? (viewed 77605 times)
  130. What is the density of a black hole? (viewed 77313 times)
  131. What would happen if a supermassive black hole came close to the Earth? (viewed 76615 times)
  132. How are black holes made? Could one be made close to us? (viewed 76481 times)
  133. How do rockets move in space? (viewed 75915 times)
  134. Can moons have moons? (viewed 75744 times)
  135. What happens to a substance if its speed is more than the speed of light? (viewed 75738 times)
  136. What would happen if you took off your helmet in space? (viewed 75716 times)
  137. What is the evidence supporting the nebula theory of Solar System formation? (viewed 75548 times)
  138. Why can't you see stars during the day? (viewed 75057 times)
  139. Do most astronomers believe in God based on the available scientific evidence? (viewed 75020 times)
  140. Does the Mediterranean sea have tides? (viewed 74924 times)
  141. When the Sun converts mass to energy, do the orbits of the planets change? (viewed 74879 times)
  142. How do astronomers measure the brightness of stars? (viewed 74779 times)
  143. Who has landed on the moon? (viewed 74420 times)
  144. What would you see from inside a black hole? (viewed 74257 times)
  145. Why do we not have eclipses every month? (viewed 74027 times)
  146. How often does the Sun pass through a spiral arm in the Milky Way? (viewed 74019 times)
  147. What are some of the effects of solar flares on Earth? (viewed 73317 times)
  148. How do we know the mass of the Earth and the Moon? (viewed 73152 times)
  149. How can the Universe expand faster than the speed of light during inflation? (viewed 73056 times)
  150. Can you fire a gun on the Moon? (viewed 72625 times)
  151. How is astronomy impacted by trigonometry? (viewed 72201 times)
  152. How do you measure a planet's mass? (viewed 71960 times)
  153. How does the Moon stay "suspended" in the air? (viewed 71685 times)
  154. Is it possible to measure the temperature of the Sun? (viewed 71618 times)
  155. How are elements heavier than iron formed? (viewed 71513 times)
  156. Why do stars change colour when they twinkle? (viewed 71214 times)
  157. How does the Sun compare to other stars? (viewed 70578 times)
  158. What are the "dog days of summer"? (viewed 68149 times)
  159. Does quantum entanglement imply faster than light communication? (viewed 67875 times)
  160. How long would it take the Earth to fall into the Sun? (viewed 67306 times)
  161. How does light pollution affect astronomers? (viewed 67222 times)
  162. What kinds of jobs do astronomers do? (viewed 66925 times)
  163. If the universe is infinite does that mean there is an infinite number of "me"s? (viewed 66662 times)
  164. Where does the name "Moon" come from? (viewed 66597 times)
  165. How did the stars get named? (viewed 66217 times)
  166. Where did the matter in the universe come from? (viewed 66127 times)
  167. How do you measure the mass of a star? (viewed 65969 times)
  168. Why doesn't the earliest sunset occur on the shortest day of the year? (viewed 65873 times)
  169. Are there stars outside of galaxies? (viewed 65846 times)
  170. Traveling at light speed, how long would it take to get to the nearest galaxy? (viewed 65791 times)
  171. What are Altitude and Azimuth? (viewed 65417 times)
  172. What are black holes made of? (viewed 65200 times)
  173. How did asteroids form and what is the difference between an asteroid and a comet? (viewed 64950 times)
  174. Why is looking out into space the same as looking back in time? (viewed 64645 times)
  175. What causes seasons? (viewed 64632 times)
  176. How fast is the Universe expanding? (viewed 64012 times)
  177. What's the difference between dark matter and dark energy? (viewed 64002 times)
  178. Where, in relation to the entire universe, is the Milky Way located? (viewed 63726 times)
  179. When can I see the Moon through the hole in the Pantheon? (viewed 63666 times)
  180. Why do planets not twinkle? (viewed 63510 times)
  181. What's the best college for astronomy? (viewed 63009 times)
  182. What would happen to us if the sun went out for an hour? (viewed 62802 times)
  183. Why doesn't the length of each day change much around the solstices? (viewed 62767 times)
  184. Why does the Sun's apparent path through the sky change throughout the year? (viewed 62750 times)
  185. What can we learn from the color of a star? (viewed 62512 times)
  186. How does astronomy benefit humankind? (viewed 62358 times)
  187. What is the mass of the Universe? (viewed 61522 times)
  188. How can I calculate the position or path of the Sun for a given time and location? (viewed 61107 times)
  189. How does the parachute in a model rocket work? (viewed 60890 times)
  190. What is the origin of spiral structure in galaxies? (viewed 60775 times)
  191. Why does the Earth have only one moon? (viewed 60515 times)
  192. How close was the Moon to the Earth when it formed? (viewed 60502 times)
  193. How do the astronauts communicate in space if sound cannot travel in a vacuum? (viewed 60435 times)
  194. Can any galaxies be seen with the naked eye? (viewed 60361 times)
  195. Does the Moon rotate? (viewed 60116 times)
  196. Could there be life in the galaxies nearest to the Milky Way? (viewed 60112 times)
  197. How long does the supernova stage of a star last? (viewed 59525 times)
  198. What makes up most of the Universe? (viewed 59399 times)
  199. If gravity is a "curvature of space" rather than a force, why do a ball and bullet follow different paths? (viewed 58648 times)
  200. What is a star's "spectrum"? (viewed 57480 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 57285 times)
  203. How do astronauts use math in their jobs? (viewed 57210 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 57126 times)
  205. What happens to a bullet fired on the moon? (viewed 56974 times)
  206. How do we measure the size of the Moon and of the Sun? (viewed 56693 times)
  207. How do you calculate the azimuth and altitude of an object? (viewed 56503 times)
  208. What is the size of a black hole? (viewed 56282 times)
  209. Where did all the water in the universe come from? (viewed 56230 times)
  210. What is the largest structure in the universe? (viewed 56225 times)
  211. Which constellation does our Sun belong to? (viewed 55849 times)
  212. Where are stars born? (viewed 55822 times)
  213. How can I find the distance to the Sun on any given day? (viewed 55565 times)
  214. Are names given to black holes? (viewed 55297 times)
  215. Which hemisphere has the best view of the Milky Way? (viewed 55065 times)
  216. Why is twilight short near the equator? (viewed 55060 times)
  217. Can you see satellites? (viewed 54995 times)
  218. What other careers involve Astronomy besides Astronomer? (viewed 54636 times)
  219. Why do we see stars? (viewed 54315 times)
  220. What do a galaxy's colors mean? Are they its true colors? (viewed 54221 times)
  221. Are meteorites hot or cold when they hit Earth? (viewed 53854 times)
  222. Why is the sky blue and not blue & purple? (viewed 53838 times)
  223. Are aliens or UFOs real? (viewed 53760 times)
  224. Is the speed of light constant? (viewed 53743 times)
  225. How can I measure the distance of a star? (viewed 53684 times)
  226. Are there any asteroids on a collision course with Earth? (viewed 53475 times)
  227. Would your weight change as you go underground? (viewed 53242 times)
  228. How long has there been water on Earth? (viewed 53219 times)
  229. How do we know what other planets (and stars, galaxies, etc.) are made of? (viewed 52862 times)
  230. What would happen if the Moon fell out of its orbit around Earth? (viewed 52855 times)
  231. How is the time of sunrise calculated? (viewed 52670 times)
  232. What are some astronomy science fair projects? (viewed 52332 times)
  233. Can we look back far enough in time to see the Big Bang? (viewed 52229 times)
  234. What skills do astronomers need? (viewed 51983 times)
  235. Are the planes of solar systems aligned with the plane of the Galaxy? (viewed 51912 times)
  236. Why does the Moon look big on the horizon? (viewed 51673 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 51509 times)
  238. Who discovered each planet? (viewed 51383 times)
  239. Is time travel possible? (viewed 51367 times)
  240. What is the difference between nutation and precession of the Earth? (viewed 51126 times)
  241. Can the acceleration of the Universe be analogous to apparent acceleration in a airplane? (viewed 50940 times)
  242. What's the difference between astronomy and astrophysics? (viewed 50628 times)
  243. Why is it difficult to understand the expansion of the universe? (viewed 50465 times)
  244. What is a graviton? (viewed 50241 times)
  245. Why are most months 30 or 31 days long? (viewed 50237 times)
  246. If light has no mass, then what draws it into a black hole? (viewed 50057 times)
  247. Why do the size and brightness of the full moon change? (viewed 49133 times)
  248. Can we find the place where the Big Bang happened? (viewed 48836 times)
  249. Do supermassive black holes cause galaxy rotation? (viewed 48825 times)
  250. Why does the Sun appear larger on the horizon than overhead? (viewed 48468 times)
  251. What do I need to do to become an astronomer? (viewed 48093 times)
  252. Why don't people walk upside-down on the bottom of the Earth? (viewed 48041 times)
  253. How are black holes discovered? (viewed 48013 times)
  254. How do gravitons escape black holes to tell the universe about their gravity? (viewed 48007 times)
  255. What is a wormhole? (viewed 47806 times)
  256. The Moon slows the Earth's rotation, but how fast was it spinning billions of years ago? (viewed 47796 times)
  257. Do dead stars still shine? (viewed 47562 times)
  258. Why are there stars? (viewed 47234 times)
  259. Is the Earth slowly getting larger? (viewed 46892 times)
  260. Did life originate on Earth, or did it come from somewhere else? (viewed 46658 times)
  261. Will we get sucked into the black hole at the center of the Milky Way? (viewed 46539 times)
  262. Why can't we see Venus at night when it is an inner planet? (viewed 46496 times)
  263. Are Kuiper Belt Objects asteroids? Are large Kuiper Belt Objects planets? (viewed 46214 times)
  264. How do galaxies collide in an expanding universe? (viewed 46171 times)
  265. Why does Barnard 68 appear dark? (viewed 46141 times)
  266. Where is the nearest black hole? (viewed 46053 times)
  267. Can I calculate the size of the Universe by converting light years to kilometres? (viewed 45567 times)
  268. Are there eclipses on other planets? (viewed 45059 times)
  269. How much can the location of sunset differ from due West? (viewed 44744 times)
  270. How long could life on Earth survive if the Sun stopped shining? (viewed 44738 times)
  271. How does Astronomy involve Chemistry? (viewed 44682 times)
  272. Could the Universe have expanded faster than the speed of light at the Big Bang? (viewed 44600 times)
  273. Why does the location of sunrise change? (viewed 44584 times)
  274. Is there a "South Star"? (viewed 44580 times)
  275. What is the difference between the "Doppler" redshift and the "gravitational" or "cosmological" redshift? (viewed 44447 times)
  276. What is the best way to see the Milky Way? (viewed 44368 times)
  277. Has there been an experiment that measured speed faster than the speed of light in vacuum? (viewed 44171 times)
  278. What happens to spacetime inside a black hole? (viewed 43953 times)
  279. How would the weather on Earth be different if it were a cube? (viewed 43943 times)
  280. What are the names of the three stars in Orion's belt? (viewed 43497 times)
  281. Was the Sun made in a supernova? (viewed 43326 times)
  282. Why doesn't dark matter fall into a black hole? (viewed 43163 times)
  283. How much longer will the Earth last? (viewed 42962 times)
  284. What is the biggest crater recorded on Earth? (viewed 42946 times)
  285. Why can we see the sun's image before sunrise and after sunset? (viewed 42869 times)
  286. What if the Earth rotated twice as fast? (viewed 42479 times)
  287. Why does the Earth only see one side of the Moon? (viewed 42345 times)
  288. Why do people draw stars with five points? (viewed 42134 times)
  289. Can I buy land on the Moon? (viewed 42101 times)
  290. How do we feel heat? (viewed 42051 times)
  291. Is the Sun always up for exactly 12 hours at the equator? (viewed 42034 times)
  292. Is the Moon hollow? (viewed 41865 times)
  293. What happens when two black holes get too close? (viewed 41860 times)
  294. Could someone travel the universe in his or her own lifetime? (viewed 41672 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 41577 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 41498 times)
  298. What is time dilation? (viewed 41482 times)
  299. How do we know that nuclear fusion is still going on in the Sun? (viewed 41299 times)
  300. How can two moons of Saturn share the same orbit? (viewed 41275 times)
  301. How fast does the Earth go at perihelion and aphelion? (viewed 41225 times)
  302. What's the biggest meteorite? (viewed 41197 times)
  303. Do you think it's possible to maintain life on other planets? (viewed 41073 times)
  304. What is the most distant known galaxy? (viewed 41032 times)
  305. Why can't a plane fly slowly and let the Earth pass underneath? (viewed 40974 times)
  306. Can terrestrial planets have rings? (viewed 40955 times)
  307. How do we define distance in an expanding universe? (viewed 40636 times)
  308. Why are Saturn's rings flat? (viewed 40594 times)
  309. Does the Sun have an iron surface? (viewed 40526 times)
  310. What are "blue stragglers" in globular clusters? (viewed 40486 times)
  311. How long would it take for a mini-black hole to eat the Earth? (viewed 40248 times)
  312. How many Astronauts have been in space? (viewed 40115 times)
  313. Who (and when) discovered that the earth's axis is on a 23 degree tilt? (viewed 40058 times)
  314. If a white dwarf is a "dead" star, why is it so hot? (viewed 40000 times)
  315. On which days can I see the Moon in the evening / morning and why is this so? (viewed 39878 times)
  316. Why do pictures of distant galaxies have higher resolution than those of nearby planets? (viewed 39855 times)
  317. Can you see the future as you fall into a black hole? (viewed 39813 times)
  318. Can a person go into a black hole and come out alive? (viewed 39738 times)
  319. What is the typical size of a visible shooting star? (viewed 39614 times)
  320. Are all stars the same? (viewed 39473 times)
  321. Is the Great Wall the largest galaxy cluster? (viewed 39428 times)
  322. What is a dimension? (viewed 39398 times)
  323. Does Mt. Everest cast a shadow on the moon? (viewed 39227 times)
  324. Where do planetary rings come from, and what are they made of? (viewed 39140 times)
  325. How can the universe be "flat"? We're 3D! (viewed 39100 times)
  326. How does night and day work? (viewed 38958 times)
  327. How do we determine the age of the universe? (viewed 38930 times)
  328. Can I communicate faster than light? (viewed 38897 times)
  329. What companies or businesses can astronomers work for? (viewed 38662 times)
  330. What is the speed of gravity? (viewed 38461 times)
  331. What is Earthrise over the Moon? (viewed 38384 times)
  332. What is the approximate GPA needed in High School in Math and Science to be an astronomer? (viewed 38324 times)
  333. How are photons created and destroyed? (viewed 38286 times)
  334. How do we know the Milky Way is a spiral galaxy? (viewed 38143 times)
  335. Where is the supernova remnant that led to our solar system? (viewed 38052 times)
  336. What kind of eyepieces do I need to look at planets? (viewed 38032 times)
  337. If the universe is 15 billion years old, how can it be larger than 15 billion light years across? (viewed 38006 times)
  338. Is there a beginning and an end to a galaxy's life? (viewed 37984 times)
  339. Why are there blue shifted galaxies? (viewed 37919 times)
  340. Why is sea water salty, and not lake water? (viewed 37793 times)
  341. What can I use for fuel in my homemade rocket? (viewed 37742 times)
  342. How big is the universe? (viewed 37724 times)
  343. Is there really a 10th planet? (viewed 37651 times)
  344. Does the Coriolis force determine which way my toilet drains? Does it affect black holes? (viewed 37567 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 37071 times)
  347. Can you describe a day on the job as an astronomer? (viewed 37064 times)
  348. How are planets detected around other stars? (viewed 37004 times)
  349. How many stars can I see? (viewed 36947 times)
  350. How do I tell which planet is which? (viewed 36869 times)
  351. What is the pattern to the distances between each planet and the sun? (viewed 36795 times)
  352. How can I find my age on another planet? (viewed 36669 times)
  353. Why do humans want to go in space? (viewed 36587 times)
  354. Can a lunar and a solar eclipse happen in the same month? When will this happen next? (viewed 36523 times)
  355. What is the significance of the second focus of elliptical orbits of planets in our Solar System? (viewed 36449 times)
  356. Do the Sun's or Earth's magnetic field reverse? (viewed 36360 times)
  357. Will we ever stop having solar eclipses because of the moon's motion away from the Earth? (viewed 36347 times)
  358. How hot is each one of the layers of the sun? (viewed 36266 times)
  359. Why have star signs shifted by one constellation? (viewed 36051 times)
  360. Is Andromeda part of the Milky Way? Where can I find them in the sky? (viewed 35939 times)
  361. Is the Local Group expanding along with the entire Universe? (viewed 35768 times)
  362. How do astronauts communicate with their families from space? (viewed 35665 times)
  363. Who came up with the name "black hole"? (viewed 35563 times)
  364. How can we estimate the number of Earth-like planets in the Galaxy? (viewed 35386 times)
  365. What would happen if two stars collided? (viewed 35204 times)
  366. What was that really big falling star that I saw? (viewed 35056 times)
  367. How do I become both an astronaut and an astronomer? (viewed 35050 times)
  368. Why don't astronomers use everyday units to measure distances (what is an AU or a pc)? (viewed 34999 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 34911 times)
  371. How is it that we see farther out in space (farther back in time) than in the past? (viewed 34817 times)
  372. When we look back to the Big Bang, why don't we see the universe as a tiny speck of matter? (viewed 34776 times)
  373. How do sunrise and sunset times change with altitude? (viewed 34643 times)
  374. Will the Moon be invisible in 500 million years? (viewed 34518 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 34047 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 33935 times)
  379. How dangerous are the asteroids? (viewed 33920 times)
  380. Which American colleges teach astronomy? (viewed 33870 times)
  381. Is the universe really like an expanding balloon? (viewed 33851 times)
  382. Why do constellations look the same after several years even though all the stars are moving? (viewed 33816 times)
  383. Why are there no craters on Earth? Did all the meteorites miss us? (viewed 33475 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 33432 times)
  386. Do we see the same stars from above and below the equator? (viewed 33410 times)
  387. Does the Moon look different in the northern and southern hemispheres? (viewed 33364 times)
  388. Why do astronauts in space need to exercise? (viewed 33089 times)
  389. What are quasars made of? (viewed 32898 times)
  390. Can superheavy elements (such as Z=116 or 118) be formed in a supernova? Can we observe them? (viewed 32840 times)
  391. Does the Milky Way spin counter-clockwise? If so, do all spiral galaxies spin in this direction and why? (viewed 32831 times)
  392. How can I calculate distances between stars? (viewed 32806 times)
  393. What is dark matter? (viewed 32623 times)
  394. Why is the time between two successive full moons different from the lunar synodic month? (viewed 32591 times)
  395. What would happen if a human were exposed to space without wearing a spacesuit? (viewed 32578 times)
  396. Why doesn't gravity change the speed of light? (viewed 32565 times)
  397. How big a change in the Earth's orbit would be required to destroy all life? (viewed 32328 times)
  398. Can we see dead stars with the naked eye? (viewed 32123 times)
  399. Is it possible to count the stars? (viewed 32114 times)
  400. How do we measure distances to other stars? (viewed 31991 times)
  401. Is time travel possible using merging black holes? (viewed 31970 times)
  402. Did the speed of light change over the history of the universe? (viewed 31961 times)
  403. How can we tell what the interiors of planets are like? (viewed 31955 times)
  404. What is happening just around the black hole in the center of the Milky Way? (viewed 31932 times)
  405. How do I make a scale model of the Solar System? (viewed 31903 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 31757 times)
  407. What do "homogeneity" and "isotropy" mean? (viewed 31748 times)
  408. What happens when an antimatter black hole collides with a matter blackhole? (viewed 31638 times)
  409. What happens when you change the mass of a White Dwarf or Neutron Star? (viewed 31423 times)
  410. Are time machines possible? (viewed 31296 times)
  411. How many moles of stars are in the known universe? (viewed 31254 times)
  412. What is the farthest in space that we have gone? (viewed 31175 times)
  413. How are galaxy distances inferred from their recessional velocities? (viewed 31143 times)
  414. Will the seasons change due to precession? (viewed 31032 times)
  415. Can astronauts produce water in space? (viewed 31032 times)
  416. How was the starting point for the Julian Date system chosen? (viewed 31027 times)
  417. How can we know that there are other galaxies if we cannot leave ours? (viewed 30838 times)
  418. How do we know if the universe will keep expanding forever? (viewed 30800 times)
  419. Aren't jobs in astronomy scarce? (viewed 30573 times)
  420. Why does the SETI project search for radio signals? (viewed 30478 times)
  421. Why do we study black holes? (viewed 30415 times)
  422. Is there any limitation to what a black hole can "suck" in? (viewed 30406 times)
  423. When are there 5 Sundays in February? (viewed 30401 times)
  424. How long does it take the Big Dipper to move in the sky? (viewed 30334 times)
  425. What are the closest and/or brightest stars? (viewed 30283 times)
  426. How can I tell if the rock I found is a meteorite? (viewed 30255 times)
  427. Do astronomers believe in astrology? (viewed 30172 times)
  428. Do you believe in UFOs? (viewed 30114 times)
  429. What's that dark spot on the Sun? (viewed 30091 times)
  430. Why are telescopes located in remote places? (viewed 30069 times)
  431. Can you use an infinite line of reflectors to send light to the edge of the Universe? (viewed 29959 times)
  432. Did I see the Aurora Borealis as a child? (viewed 29943 times)
  433. Why do most moons orbit their planets at the equator? (viewed 29846 times)
  434. What are the facts about the Star of Bethlehem? (viewed 29840 times)
  435. Wouldn't the Big Bang theory be considered a hypothesis and not a theory? (viewed 29832 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 29523 times)
  439. Could you tell me about the life cycle of galaxies? (viewed 29500 times)
  440. Why do so many of the world's UFO sightings happen in America? (viewed 29495 times)
  441. What colors are visible through an amateur telescope? (viewed 29437 times)
  442. Could an astronaut or satellite fall into a black hole that we didn't know about? (viewed 29402 times)
  443. What is the origin of the stellar classification system "OBAFGKM"? (viewed 29369 times)
  444. How can geometry be different in space? (viewed 29089 times)
  445. Why are the compositions of comets and asteroids different? (viewed 29085 times)
  446. Was I hit by a meteorite? (viewed 28962 times)
  447. How are galaxies named? (viewed 28959 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 28920 times)
  450. How do astronomers measure the radius of a star? (viewed 28903 times)
  451. Can two lunar eclipses occur in the same month? (viewed 28821 times)
  452. How do asteroids, meteors and comets disappear? (viewed 28602 times)
  453. How do I explain to my children why the Moon has phases? (viewed 28346 times)
  454. How much time do astronomers spend looking through telescopes? (viewed 28246 times)
  455. Will winter and summer constellations change due to abnormal warmth or cold on Earth? (viewed 28224 times)
  456. How can we see galaxies if their stars are so faint? (viewed 28204 times)
  457. Do asteroids hit the sun? (viewed 28162 times)
  458. Can a human give birth in space? (viewed 28157 times)
  459. How are galaxies and solar systems similar? (viewed 28027 times)
  460. Have there been other Big Bangs before? (viewed 28001 times)
  461. Do the magnitudes and colors of stars ever change? (viewed 27911 times)
  462. How will the two black holes that are going to collide affect Earth? (viewed 27838 times)
  463. Is there a project I can do on black holes? (viewed 27747 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 27601 times)
  466. Is there oxygen in the atmospheres of other planets? (viewed 27532 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 27495 times)
  469. Which part of the sky did the famous 'wow' signal originate from? (viewed 27458 times)
  470. Is the Milky Way a collision of two galaxies? (viewed 27457 times)
  471. What causes gamma ray bursts? (viewed 27404 times)
  472. How do scientists slow light down? (viewed 27395 times)
  473. What supernova created the Crab nebula? (viewed 27286 times)
  474. How close does a supernova need to be to damage the Earth's environment? (viewed 27276 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 27180 times)
  477. Can double stars have planets? (viewed 27178 times)
  478. Is infinite temperature possible? (viewed 27129 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 27127 times)
  480. Do we know everything about the Sun? (viewed 27038 times)
  481. Can one star orbit another? (viewed 26930 times)
  482. Can astronauts play musical instruments in space? (viewed 26797 times)
  483. When did people discover that the Sun is a star? (viewed 26759 times)
  484. What will happen to the Milky Way in the future? (viewed 26758 times)
  485. How far does a galaxy extend? (viewed 26734 times)
  486. What is sidereal time? (viewed 26724 times)
  487. Are planetary nebulae the result of supernovae? (viewed 26655 times)
  488. Which way does the sun travel in the southern hemisphere? (viewed 26641 times)
  489. How do I polar align my telescope? (viewed 26615 times)
  490. Is there sound coming from the Sun? (viewed 26575 times)
  491. What type of energy does a black hole have? (viewed 26528 times)
  492. What's the object I saw that moved across the sky and then got very bright? (viewed 26526 times)
  493. What is the farthest Northern Latitude in which the Magellanic Clouds can be seen? (viewed 26518 times)
  494. What is "nothing", from a scientific point of view? (viewed 26502 times)
  495. Why is the shadow on the Moon the shape it is? (viewed 26497 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 26486 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 26344 times)
  500. Why do the explosions of Type Ia supernovae have a more predictable spectrum than those of regular Type II supernovae? (viewed 26279 times)
  501. What is our galaxy's halo made of, and how was it formed? (viewed 26278 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 26150 times)
  504. When unmanned spacecraft accelerate in space, what causes them to slow down? (viewed 26123 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 26069 times)
  507. What is the difference between homogeneity and isotropy? (viewed 26064 times)
  508. How do we know that sunspots are associated with the Sun's magnetic field? (viewed 25968 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 25876 times)
  511. What calculations go into predicting eclipses? (viewed 25859 times)
  512. How are asteroid compositions and classifications determined? (viewed 25826 times)
  513. Are there any dark stars or dark galaxies made of dark matter? (viewed 25799 times)
  514. Can I see a quasar? (viewed 25739 times)
  515. Is there a list of the sizes of different kinds of stars? (viewed 25658 times)
  516. How many sunspots can the Sun have at once? (viewed 25619 times)
  517. Would the biggest airplanes cause tsunamis if they crashed? (viewed 25619 times)
  518. Can I see details on Venus? (viewed 25614 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 25527 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 25405 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 25346 times)
  527. Did a giant impact cause the Dark Ages? (viewed 25345 times)
  528. What equipment do I need for astrophotography? (viewed 25283 times)
  529. How is it proved that the Universe is expanding? (viewed 25268 times)
  530. Have gravitational waves been proven to exist? (viewed 25261 times)
  531. What is a Dyson Sphere? (viewed 25205 times)
  532. How do unmanned space probes avoid running into things? (viewed 25176 times)
  533. If the Universe was infinitely dense at the Big Bang, why didn't time stand still? (viewed 25100 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 24908 times)
  537. Can you give me advice on buying a telescope? (viewed 24829 times)
  538. How long do supernova remnants last? (viewed 24823 times)
  539. How can I contribute to science as an amateur astronomer? (viewed 24818 times)
  540. How can we compare dark matter and dark energy? (viewed 24715 times)
  541. Why is it important to study meteorites? (viewed 24674 times)
  542. How big was the Sun when it first "fired up"? (viewed 24658 times)
  543. How do solar flares affect airline pilots? (viewed 24607 times)
  544. Why do photos of space taken from space never show any stars? (viewed 24591 times)
  545. What caused Shoemaker-Levy 9 to split up? (viewed 24579 times)
  546. Could we send a space mission to a comet? (viewed 24574 times)
  547. Why doesn't NASA build rotating spacecraft to simulate gravity? (viewed 24553 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 24513 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 24389 times)
  553. Could a different theory of gravity explain the dark matter mystery? (viewed 24343 times)
  554. Where does the kinetic energy of infalling bodies come from? (viewed 24314 times)
  555. Did I really hear a meteor? (viewed 24230 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 24093 times)
  560. Can you tell time by the Big Dipper? (viewed 24034 times)
  561. Do the Earth's magnetic poles ever change places? (viewed 23999 times)
  562. Do unmanned spacecraft like Voyager travel in straight lines? (viewed 23913 times)
  563. Why is the Hubble Space Telescope in space? (viewed 23907 times)
  564. How could galaxies have gotten so far away in only 15 billion years? (viewed 23881 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 23776 times)
  569. How powerful are quasars? (viewed 23768 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 23704 times)
  573. Are there any new craters on the moon? (viewed 23643 times)
  574. How do I become an astronomical artist? (viewed 23606 times)
  575. Can supernovae hinder the formation of life in galaxies? (viewed 23568 times)
  576. How do astronomers observe the Sun's interior? (viewed 23563 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 23491 times)
  580. Could there have been multiple Big Bangs at different places in the universe? (viewed 23481 times)
  581. How do planets capture satellites? (viewed 23473 times)
  582. What kind of telescope should I use for astrophotography? (viewed 23434 times)
  583. Could dark energy come from matter anti-matter pairs forming spontaneously and then annihilating? (viewed 23312 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 23175 times)
  587. Does the Sun have any heavy elements? (viewed 23078 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 23020 times)
  590. What class of spiral galaxy is the Milky Way? (viewed 23003 times)
  591. Why do spacecraft need heat shields coming back to Earth but not leaving? (viewed 22977 times)
  592. Where was the water in the big bang? (viewed 22933 times)
  593. Could we send a manned mission to the outer planets? (viewed 22918 times)
  594. Will we discover an 11th planet? What would it be called? (viewed 22904 times)
  595. Are the properties of extrasolar planets known? (viewed 22866 times)
  596. How can water be chemically trapped in rocks? (viewed 22815 times)
  597. What month was it when Odysseus saw Orion in 1000BC? (viewed 22679 times)
  598. Is it possible for amateurs to do optical interferometry? (viewed 22671 times)
  599. What makes a satellite geosyncronise itself with Earth's orbit? (viewed 22563 times)
  600. Why does the apparent density of galaxies drop off at larger distances? (viewed 22458 times)
  601. Would a planet near the galactic center have a brighter night sky? (viewed 22389 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 22330 times)
  604. Why are accretion disks flat? (viewed 22283 times)
  605. How can the Sun have such a strong gravitational field if it's made of gasses? (viewed 22268 times)
  606. Why was the Platonic year named after Plato? (viewed 22057 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 21923 times)
  610. How are supernovae discovered? (viewed 21867 times)
  611. What is meant by "stopping down a telescope"? (viewed 21845 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 21622 times)
  617. If photons have zero mass, why do they feel the effects of gravity? (viewed 21588 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 21491 times)
  621. What is the SU(3) quark model? (viewed 21450 times)
  622. Do constellations looks the same from space? (viewed 21378 times)
  623. Can gravitational lensing from intervening galaxies cause the observed ripples in the Cosmic Microwave Background? (viewed 21361 times)
  624. Does a photon observe other photons moving past it at the speed of light? (viewed 21280 times)
  625. How can we find galaxies behind the Milky Way? (viewed 21213 times)
  626. Why is the WMAP picture of the CMB an ellipse? (viewed 21161 times)
  627. Could photons be dark matter? (viewed 21155 times)
  628. How fast do particles travel in space? (viewed 21138 times)
  629. What's new with the Big Bang? (viewed 21104 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 20995 times)
  632. Why can we have solar eclipses? (viewed 20985 times)
  633. What are collections of galaxies called? (viewed 20969 times)
  634. Where can I find information on the moons of other planets? (viewed 20935 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 20923 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 20710 times)
  639. Did the Sumerians measure precession? (viewed 20677 times)
  640. How did Mars get so dusty? (viewed 20651 times)
  641. What are the boundaries of the constellations? (viewed 20588 times)
  642. What kinds of star clusters are there? (viewed 20575 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 20407 times)
  645. Why don't astronauts sublimate in space? (viewed 20335 times)
  646. How do bars form in spiral galaxies? (viewed 20334 times)
  647. Why aren't discoveries of extrasolar planets reported on the news? (viewed 20289 times)
  648. Why is the Cosmic Microwave Background not absorbed by interstellar hydrogen? (viewed 20283 times)
  649. How do astronomers come up with their facts? (viewed 20280 times)
  650. Do electrons age? (viewed 20170 times)
  651. Can HST see the Oort cloud? (viewed 20098 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 20038 times)
  654. How does melting a material reset its radioactive clock? (viewed 20028 times)
  655. Why don't all neutron stars become pulsars? (viewed 20022 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 19940 times)
  659. How does the color index of a star relate to its actual color? (viewed 19920 times)
  660. Why is it called astronomy when all the other sciences end in -ology? (viewed 19915 times)
  661. Does the shuttle worry about space junk? (viewed 19884 times)
  662. Where can I see Newton's original reflecting telescope? (viewed 19875 times)
  663. How do you classify galaxies? (viewed 19806 times)
  664. How can we understand the meaning of large numbers like "a million million?" (viewed 19782 times)
  665. Are black holes spherical? (viewed 19778 times)
  666. Why do supernova remnants look like rings rather than spheres? (viewed 19754 times)
  667. If nothing can escape a black hole, why do some black holes have jets? (viewed 19725 times)
  668. What causes a particle to decay? (viewed 19648 times)
  669. What is the best time of the year to see eclipses? (viewed 19606 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 19513 times)
  672. How can I nominate myself for a Nobel Prize in Physics? (viewed 19465 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 19350 times)
  675. What are "curled" dimensions? (viewed 19275 times)
  676. Do asteroids ever do anything good in the Solar System? (viewed 19242 times)
  677. What would happen if you went back in time and killed your grandmother? (viewed 19234 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 19007 times)
  683. What was that eclipse I saw in the sky? (viewed 18989 times)
  684. Why will fusion wait until hydrogen is gone before starting to fuse heavier atoms? (viewed 18963 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 18902 times)
  687. How can I watch the Perseid meteor shower? (viewed 18864 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 18814 times)
  690. Can astronomers observe anything when the moon is full? (viewed 18758 times)
  691. Do we really observe the edges of galaxies at different epochs? (viewed 18730 times)
  692. How are astronauts trained for weightlessness? (viewed 18715 times)
  693. How do supernovae show us that the Universe's expansion is accelerating? (viewed 18709 times)
  694. When measuring the expansion of the universe, do astronomers consider that they're seeing how galaxies moved long ago, not today? (viewed 18707 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 18548 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 18256 times)
  701. Is cosmic expansion happening on microscopic scales? (viewed 18206 times)
  702. Could neutrinos be dark matter? (viewed 17928 times)
  703. How can I find out if the new moon has been sighted? (viewed 17917 times)
  704. Do we have to worry about relativity when studying galactic objects? (viewed 17788 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 17570 times)
  707. How does a star take mass from another star? (viewed 17535 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 17380 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 17226 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 17163 times)
  714. Is the green flash real? (viewed 17062 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 16738 times)
  717. How can observations of the distant universe prove that the expansion is accelerating *now*? (viewed 16698 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 16571 times)
  721. What do meteorites tell us about life on other planets? (viewed 16555 times)
  722. No matter how fast the universe is expanding, shouldn't gravity eventually make it recollapse? (viewed 16504 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 16454 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 16029 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 15981 times)
  730. When will Hale-Bopp return? (viewed 15866 times)
  731. How do we detect incoming meteorites? (viewed 15842 times)
  732. Has anyone ever seen a star "turn on"? (viewed 15788 times)
  733. Are there any 'lonely galaxies'? (viewed 15635 times)
  734. Why are craters round? (viewed 15555 times)
  735. Can the sun rise from the west on Mars? (viewed 14814 times)
  736. During close approaches, can Mars appear in our sky as large as the Moon? (viewed 14811 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 14237 times)
  740. How can we discern different galaxies/clusters along the same line of sight? (viewed 14066 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 13982 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 13350 times)
  745. What is between the Oort cloud and the closest star? (viewed 13217 times)
  746. Could a planetary system survive if its star merged with another, or if its star went supernova? (viewed 12303 times)
  747. Why is the Moon higher in the sky in winter and lower in the summer? (viewed 12232 times)
  748. Are there solar tides? (viewed 12172 times)
  749. Is the Moon always visible during winter on the North Pole? (viewed 11976 times)
  750. Is Earth-moon tidal friction causing global warming? (viewed 11905 times)
  751. Does weightlessness affect hunger? (viewed 11838 times)
  752. Is the moon spherical? (viewed 11800 times)
  753. Do planets radiate noise? (viewed 11664 times)
  754. Is dark energy affected by black holes? (viewed 11548 times)
  755. Where are the protons and electrons in a Neutron Star? (viewed 11546 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 10913 times)
  758. Will the Pioneer and Voyager probes ever leave the Milky Way? (viewed 10154 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 9705 times)
  764. Is it sensible to consider terraforming Mars? (viewed 9575 times)
  765. What color are meteors? (viewed 9430 times)
  766. Where is everybody? (viewed 8827 times)
  767. Why do astronomers use telescopes? (viewed 8755 times)
  768. Why does Mars have a dusty atmosphere? (viewed 8674 times)
  769. Does the singularity in a black hole create a new Universe? (viewed 8428 times)
  770. The naming of Mars (viewed 8386 times)
  771. If I were traveling through space, could I see distant galaxies with my own eyes? (viewed 8383 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 7025 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 5788 times)
  780. Can the Sun be closer to the Earth than any planet is to Earth? (viewed 5331 times)
  781. Cosmologists say the expansion of the universe is accelerating, what is driving this? (viewed 4465 times)
  782. Can we hear sound on Titan? (viewed 4180 times)
  783. Does the direction of the moon's crescent change through the night? (viewed 4032 times)
  784. What do all the angles in a table for a planet's orbit mean? (viewed 3904 times)
  785. How do I maximize my chances of seeing shooting stars? (viewed 3438 times)
  786. Are exoplanets real? (viewed 2894 times)
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