1 00:00:00,120 --> 00:00:03,160 Speaker 1: Stuff happens, just don't let it happen to your photos, music, 2 00:00:03,200 --> 00:00:06,920 Speaker 1: and documents. Protect your important files with Mosey by e MC, 3 00:00:07,320 --> 00:00:10,400 Speaker 1: the most trusted name in cloud backup Save ten percent 4 00:00:10,520 --> 00:00:14,000 Speaker 1: today with promo code brain Stuff at mosey dot com. 5 00:00:14,000 --> 00:00:17,400 Speaker 1: That's m o z y dot com. Welcome to brain 6 00:00:17,400 --> 00:00:28,840 Speaker 1: Stuff from how stuff works dot com where smart Happens. Hi, 7 00:00:28,880 --> 00:00:33,120 Speaker 1: I'm Marshall Brain with today's question, how does gravity assist 8 00:00:33,320 --> 00:00:38,839 Speaker 1: work with interplanetary satellites? When NASA sends satellites out to 9 00:00:38,880 --> 00:00:41,760 Speaker 1: the outer reaches of the Solar System, it will often 10 00:00:41,920 --> 00:00:46,160 Speaker 1: send the satellites past the planet for a gravity assist. 11 00:00:46,720 --> 00:00:50,240 Speaker 1: The satellite speeds up in the process. The idea behind 12 00:00:50,240 --> 00:00:53,239 Speaker 1: a gravity assist is to use the planet's motion to 13 00:00:53,479 --> 00:00:58,200 Speaker 1: accelerate the satellite. For example, as satellite heads towards Jupiter 14 00:00:58,600 --> 00:01:02,760 Speaker 1: in the process, it accelerates because it's falling towards Jupiter 15 00:01:02,920 --> 00:01:07,039 Speaker 1: through Jupiter's gravity. Then it passes fairly close to the 16 00:01:07,080 --> 00:01:10,720 Speaker 1: planet and starts speeding away from it. However, at that point, 17 00:01:10,800 --> 00:01:13,840 Speaker 1: the satellites starts slowing down because gravity is pulling it 18 00:01:13,880 --> 00:01:17,279 Speaker 1: back towards the planet. From that description, it would seem 19 00:01:17,360 --> 00:01:20,600 Speaker 1: like the net effect of gravity assist is zero. The 20 00:01:20,640 --> 00:01:23,920 Speaker 1: satellite gains speed as it falls towards the planet, but 21 00:01:23,920 --> 00:01:26,480 Speaker 1: then it loses it as it heads away. The thing 22 00:01:26,520 --> 00:01:29,120 Speaker 1: that makes the assist work is the fact that the 23 00:01:29,200 --> 00:01:33,200 Speaker 1: planet is in motion in its orbit. Jupiter, for example, 24 00:01:33,600 --> 00:01:37,039 Speaker 1: is about five hundred million miles away from the Sun, 25 00:01:37,120 --> 00:01:40,240 Speaker 1: which means that the circumference of its orbit is about 26 00:01:40,280 --> 00:01:44,759 Speaker 1: three billion miles. Jupiter travels that distance in about twelve years, 27 00:01:44,760 --> 00:01:47,960 Speaker 1: so it's moving through space at about thirty thousand miles 28 00:01:47,960 --> 00:01:51,320 Speaker 1: per hour. If the satellite is moving in the same 29 00:01:51,360 --> 00:01:54,760 Speaker 1: direction as Jupiter in its orbit, then it can actually 30 00:01:54,800 --> 00:01:58,480 Speaker 1: increase its speed by thirty thousand miles per hour. That's 31 00:01:58,520 --> 00:02:02,880 Speaker 1: a huge speed increase, and it's completely free. The problem 32 00:02:02,920 --> 00:02:05,000 Speaker 1: with the assist is that you have to wait for 33 00:02:05,040 --> 00:02:07,640 Speaker 1: the planets to line up correctly for it to work. 34 00:02:08,120 --> 00:02:11,640 Speaker 1: That's why missions have to fly within certain time windows. 35 00:02:13,120 --> 00:02:15,560 Speaker 1: For more on this and thousands of other topics, is 36 00:02:15,600 --> 00:02:22,320 Speaker 1: it How stuff works dot Com Protect your photos, music 37 00:02:22,360 --> 00:02:25,040 Speaker 1: and documents and access to them anywhere with mosey by 38 00:02:25,080 --> 00:02:27,720 Speaker 1: e m C the most trusted name and cloud backup 39 00:02:28,160 --> 00:02:31,200 Speaker 1: and now save ten with promo code. Brain Stuff at 40 00:02:31,240 --> 00:02:33,880 Speaker 1: mosey dot com. Get started today at m o z 41 00:02:34,200 --> 00:02:35,280 Speaker 1: y dot com