Guest Posted January 4, 2019 Share Posted January 4, 2019 2 hours ago, ballpoint said: http://www.planetary.org/blogs/guest-blogs/2018/20180615-queqiao-orbit-explainer.html Thanks for this! What makes the L2 a halo orbit? Is it because Moon sways from side to side, compared to Earth? Does Earth's mass have anything else but a miniscule effect to L2 position? Link to comment Share on other sites More sharing options...
Skeptic7 Posted January 4, 2019 Share Posted January 4, 2019 3 hours ago, ballpoint said: I realise you're being facetious, but putting on my pedantic hat, the dark side gets as much sunlight as the "light" side. It just doesn't get any reflected light from the Earth. Correct. Plenty light on the 'dark side'. It's only perpetually dark from Earth's perspective. the "dark" side of the moon has always, from its perspective, gotten plenty of light. When Earth sees a waning crescent, the far side is nearing fullness. full article w/awesome vid here: https://www.washingtonpost.com/news/speaking-of-science/wp/2015/02/09/nasa-gives-us-an-amazing-look-at-the-dark-side-of-the-moon/?noredirect=on&utm_term=.14ada9b0d50e 3 hours ago, ballpoint said: 23 posts in and not a single mention of Pink Floyd? This place has gotten serious in 2019. This article doesn't miss it! https://www.space.com/42886-not-dark-side-of-moon-china-lunar-farside.html Link to comment Share on other sites More sharing options...
Dumbastheycome Posted January 4, 2019 Share Posted January 4, 2019 9 hours ago, Longcut said: Who took the picture? Unknown but I hope who ever it was took care not to let a soy sauce bottle roll into view ! Link to comment Share on other sites More sharing options...
ballpoint Posted January 4, 2019 Share Posted January 4, 2019 50 minutes ago, oilinki said: Thanks for this! What makes the L2 a halo orbit? Is it because Moon sways from side to side, compared to Earth? Does Earth's mass have anything else but a miniscule effect to L2 position? For any body in orbit around another in space, such as the Earth and Sun, or in this case, the moon and Earth, there will be three points along a line drawn through their centres where a halo orbit is possible. (These are called Lagrange points, which is where the L in L2 comes from). L1 is between the two, at the distance where the gravity of each partially cancel one another out, so will be closer to the smaller body. L2 is beyond the smaller body (here the moon). Normally, any object in Earth orbit beyond the moon will have a higher period than the moon does, however at the L2 point, the combined gravity of the Earth and moon keep it fixed relative to the moon. L2 orbits the Earth at the same period as the moon, and the Chinese satellite orbits L2. L3 is beyond the larger body, a little beyond the orbit distance of the smaller body. The principle is the same as L2, whereas the combined gravity of the two bodies keep it fixed relative to the smaller one. ie it will always be directly opposite the moon relative to the Earth. There are also two other Lagrangian points, L4 and L5, determined by drawing a line from centre to centre of the two bodies and then making that line the base of an equilateral triangle. L4 and L5 will be at the apexes of that triangle. A number of asteroids and interplanetary dust in fixed, stable orbits are found at these points (from the Sun-planet interaction) off many of the planets, including Earth. This diagram is for the Earth and Sun, but the principle is the same for the moon and Earth. Link to comment Share on other sites More sharing options...
Guest Posted January 4, 2019 Share Posted January 4, 2019 For the Lagrange points L1 and L2 are easy. L3 is kind of easy if it's on higher orbit, slightly following the Earth's orbit. L4 and L5 has puzzled my brain for years. How does those work. I think I finally got my head around L5, which follows the gravity pull of the smaller mass, like Earth together with the Sun. If an object in L5 slows down, it drops to a lower and therefore quicker orbit. Earth gravity pulls it to faster speed and therefore it goes back to the higher orbit. If the object on L5 for some reason speeds up, it would go to higher orbit, where the orbit is longer and therefore it would stay behind from the Earth. However the Earth gravity pull would keep it locked with Earth. L4 should work in the similar way, but with smaller gravitational well radius if I understood how the forces effect to small asteroids or space telescopes correctly. I guess this is one way to spend a Friday evening and get an headache meanwhile. Link to comment Share on other sites More sharing options...
ballpoint Posted January 4, 2019 Share Posted January 4, 2019 1 hour ago, Skeptic7 said: Correct. Plenty light on the 'dark side'. It's only perpetually dark from Earth's perspective. the "dark" side of the moon has always, from its perspective, gotten plenty of light. When Earth sees a waning crescent, the far side is nearing fullness. full article w/awesome vid here: https://www.washingtonpost.com/news/speaking-of-science/wp/2015/02/09/nasa-gives-us-an-amazing-look-at-the-dark-side-of-the-moon/?noredirect=on&utm_term=.14ada9b0d50e This article doesn't miss it! https://www.space.com/42886-not-dark-side-of-moon-china-lunar-farside.html Yes, there is even a push in astronomical circles to get it renamed to avoid confusion. Personally, if the side we see is the front side then the reverse should be the back side, but "China lands probe on moon's backside" doesn't have the same gravitas. Some might even take it to mean they'd declared war on South Korea. Link to comment Share on other sites More sharing options...
ballpoint Posted January 4, 2019 Share Posted January 4, 2019 13 minutes ago, oilinki said: I guess this is one way to spend a Friday evening and get an headache meanwhile. Quite appropriate when talking about halo orbits: It makes a welcome change from arguing over Trump/Brexit/Prayuth/the Thai Baht/cars/etc/etc/etc though. Link to comment Share on other sites More sharing options...
Guest Posted January 4, 2019 Share Posted January 4, 2019 23 minutes ago, ballpoint said: It makes a welcome change from arguing over Trump/Brexit/Prayuth/the Thai Baht/cars/etc/etc/etc though. Indeed so. Talking and wondering about sciences & technology is so much more fun and educational than many other discussions. Tip to the folks who select the news. If possible, increase the amount of scientific news and you'll be rewarded as well behaving boys and girls who much rather talk of these kind of topics ???? We already have a good base of people who are more interested about sciences than politics. Link to comment Share on other sites More sharing options...
tifino Posted January 4, 2019 Share Posted January 4, 2019 the Chinese will soon next declare their slice of Spratly Moon Cheese... but then the boy who cried wolf syndrome will evolve into reality; just like how the fake stealth fighter programme - didn't... there really is only the one terrestrial authority I'd believe when it comes to The Far Side topic: and that is: Larsen maybe they should be adventurous and upscale their quest, and go look at the backside of uranus Link to comment Share on other sites More sharing options...
Guest Posted January 4, 2019 Share Posted January 4, 2019 6 hours ago, ballpoint said: Yes, there is even a push in astronomical circles to get it renamed to avoid confusion. Personally, if the side we see is the front side then the reverse should be the back side, but "China lands probe on moon's backside" doesn't have the same gravitas. Some might even take it to mean they'd declared war on South Korea. The last time astronomers were allowed to vote for a meaningful definition, which had a meaning for the rest of the 99.9942% of the people, they voted Pluto to no to be a real planet. Their vote was wrong to humankind. I think it's time to get the philosophers back to the equation to interpret, to be translators between physicists and the people. Link to comment Share on other sites More sharing options...
balo Posted January 4, 2019 Share Posted January 4, 2019 I am a bit disappointed , I was expecting to meet my old childhood friends hiding on the dark side. Link to comment Share on other sites More sharing options...
Rhys Posted January 4, 2019 Share Posted January 4, 2019 Does Dr. Greer have an opinion on this? Link to comment Share on other sites More sharing options...
Kiwiken Posted January 5, 2019 Share Posted January 5, 2019 On 1/3/2019 at 1:26 PM, otherstuff1957 said: The Chinese space agency has cooperated with pretty much all the other space-exploring countries, except for the US. Because the USA does not trust them and Yet! Co operates with Russia? Link to comment Share on other sites More sharing options...
ballpoint Posted January 5, 2019 Share Posted January 5, 2019 4 hours ago, balo said: I am a bit disappointed , I was expecting to meet my old childhood friends hiding on the dark side. Expecting to meet them? You certainly dropped a clanger there. You're whistling up the wrong planet. Link to comment Share on other sites More sharing options...
harada Posted January 5, 2019 Share Posted January 5, 2019 I certainly hope that news of this landing was beamed out to their concentration camps, the inmates will be ecstatic. Link to comment Share on other sites More sharing options...
kokopelli Posted January 5, 2019 Share Posted January 5, 2019 On 1/4/2019 at 6:55 AM, Crossy said: From the BBC coverage, spot the deliberate error. Nice view of the Earth from the dark side of the moon. Link to comment Share on other sites More sharing options...
kokopelli Posted January 5, 2019 Share Posted January 5, 2019 On 1/4/2019 at 1:34 PM, simon43 said: An interesting (for me) aspect of this project is that it's the first time (AFAIK) that a satellite has been placed in what is probably a long-term orbit around another planet. Sure, many space vehicles and satellites have orbited other planets as part of their mission, but only for a limited amount of time. If China placed this satellite in orbit around the moon, then it will probably stay in orbit for some time, (unless intentionally sent elsewhere..), because the Moon's gravity is much less than the Earth's - so the 'pull' of gravity on the satellite is much weaker. Here ends today's Science lesson ???? There have been orbiters around Mars for many years. The Chinese orbiter will remain in orbit due to absence of an atmosphere on the Moon; not a result of weaker gravity. Link to comment Share on other sites More sharing options...
ballpoint Posted January 5, 2019 Share Posted January 5, 2019 28 minutes ago, kokopelli said: There have been orbiters around Mars for many years. The Chinese orbiter will remain in orbit due to absence of an atmosphere on the Moon; not a result of weaker gravity. The Queqiao relay satellite isn't orbiting the moon, but a gravitationally stable point in space (the L2 point - see previous posts for more details), some 65,000 km beyond it, meaning it is always visible to the lunar lander and to Earth. It will remain in orbit for 5 years, so it's likely that the Chinese will launch further missions in that time to make use of it. Just how to communicate with a lunar lander that is unreachable via direct radio contact from Earth has been one of the reasons why no one has previously sent a mission to the dark/far/back side of the moon, and the fact that the Chinese have successfully achieved it should give pause to some of the China bashers that have already posted on this thread. The fact that the far side is shielded from Earth's radio signals may make it an ideal place for setting up a radio telescope, where it should be free from any man made interference, so landing there isn't just a matter of national pride, but could be very valuable scientifically. Finally, here's a picture of the rather bright dark side, taken by the Apollo 16 mission. It's the moon, captain, but not as we know it. Where's the rabbit? Link to comment Share on other sites More sharing options...
Guest Posted January 5, 2019 Share Posted January 5, 2019 1 hour ago, ballpoint said: Where's the rabbit? That was the 2nd reference of rabbit related to Chinese Moon efforts. First was Jade Rabbit few years back. I had to google what's the meaning of a Rabbit in Chinese folklore. Quote The moon rabbit in folklore is a rabbit that lives on the Moon, based on pareidolia that identifies the markings of the Moon as a rabbit. The folklore originated in China, and then spread to other Asian cultures.[1] In East Asian folklore, it is seen pounding with a mortar and pestle, but the contents of the mortar differ among Chinese, Japanese, and Korean folklore. In Chinese folklore, it is often portrayed as a companion of the Moon goddess Chang'e, constantly pounding the elixir of life for her; but in Japanese and Korean versions, it is pounding the ingredients for rice cake. In some Chinese versions, the rabbit pounds medicine for the mortals. https://en.wikipedia.org/wiki/Moon_rabbit That also explains the name Chang. Which I previously thought of meaning a elephant.. no, no.. meaning change as in English for changing time. It is probably meaning both the Moon's goddess and the change. Clever multidimensional word association. Link to comment Share on other sites More sharing options...
Peasandmash Posted January 5, 2019 Share Posted January 5, 2019 they landed on the side of the moon no one can see? LOL. It's a hoax and I don't believe it. Link to comment Share on other sites More sharing options...
Mosha Posted January 6, 2019 Share Posted January 6, 2019 And the UK sends China Foreign Aid.Sent from my SMART 4G GEN C 5.0 using Tapatalk Link to comment Share on other sites More sharing options...
Guest Posted January 8, 2019 Share Posted January 8, 2019 The Moon and our Earth. Seen from beyond Moon. Link to comment Share on other sites More sharing options...
balo Posted January 8, 2019 Share Posted January 8, 2019 Beautiful , I hope one day we can have a moon base there so tourists can visit , after all it's almost 2020 and when I was a kid they told me we would be flying in space ships to other planets around this time. Link to comment Share on other sites More sharing options...
ballpoint Posted January 8, 2019 Share Posted January 8, 2019 2 minutes ago, balo said: Beautiful , I hope one day we can have a moon base there so tourists can visit , after all it's almost 2020 and when I was a kid they told me we would be flying in space ships to other planets around this time. Only 20 years too late... and counting. Link to comment Share on other sites More sharing options...
sammieuk1 Posted January 8, 2019 Share Posted January 8, 2019 It was so dark they could have stuck a flag in Mr Kim by mistake???? Link to comment Share on other sites More sharing options...
Guest Posted January 11, 2019 Share Posted January 11, 2019 Pure space sex.. Moment ago prodcasted updates of Chang'e-4 lander Link to comment Share on other sites More sharing options...
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