Wikipedia:Reference desk/Archives/Science/2019 September 3

= September 3 =

spy satellites, aids to optics
If one had a spy satellite with great optics, could image quality be improved even more by somehow combining the visual information with information gathered simultaneously by pulsed radar or masers/lasers?Rich (talk) 02:15, 3 September 2019 (UTC)


 * Possibly, but if they detected those active systems they might well take that as an attack, and shoot down the satellite, if they could. They would say "We were attacked by lasers", and the power levels and frequencies wouldn't be understood by the general public. SinisterLefty (talk) 02:52, 3 September 2019 (UTC)
 * See LIDAR -- uses lasers, and nobody is complaining about being attacked. —2606:A000:1126:28D:C4E6:C890:C83B:1F95 (talk) 08:09, 3 September 2019 (UTC)


 * Is it used to spy on anyone ? People get a lot more cranky when you do that. SinisterLefty (talk) 12:02, 3 September 2019 (UTC)
 * Adaptive optics can use an artificial guide star created by a laser. This is used by telescopes looking out into space. Spy satellite operators probably don't want to be so obvious. Graeme Bartlett (talk) 12:08, 3 September 2019 (UTC)


 * USA 224 likely uses adaptive optics to get to the resolution shown in Trump's tweet. The resolution is near the diffraction limit of a telescope as large as the Hubble space telescope, the satellite is a large bright satellite that cannot be hidden. Count Iblis (talk) 12:32, 3 September 2019 (UTC)
 * Imaging radar shows examples of what can be done Gem fr (talk) 12:39, 3 September 2019 (UTC)

How much slower is a tornado at 10 meters than at the fastest height?
Internet says max wind is 300 feet up. Sagittarian Milky Way (talk) 16:22, 3 September 2019 (UTC)


 * That's going to depend on what's on the ground. A forest will really slow the wind down, as that energy is used up ripping up trees. Lakes or oceans also slow it down, as water is heavy, so the tornado uses up a lot of energy lifting it (waterspouts are typically quite mild compared with tornadoes). A paved surface wouldn't slow the wind down as much, unless it's powerful enough to rip up the pavement. SinisterLefty (talk) 19:56, 3 September 2019 (UTC)
 * Not that simple. You see, a tornado is basically a big updraft, meaning, the energy lost on the ground for whatever reason (friction, lifting material like sand or water, ...) is also lost for the whole tornado and will impact the max wind. Gem fr (talk) 21:10, 3 September 2019 (UTC)


 * Are you looking for a formula for vertical wind shear? Here's a semi-empirical formula I sort of remember from introductory atmospheric physics class (ten years ago). Yanping Nora Soong (talk) 23:38, 4 September 2019 (UTC)


 * Do you know why max wind is so low above surface level compared to an average of the first hundred or so hurricane eyewalls ever measured which was 500 meters? Does it have something to do with tornados often being funnel shaped? Sagittarian Milky Way (talk) 03:00, 5 September 2019 (UTC)


 * Hurricanes are just so much larger in every dimension, including height. They can extend up to the borders of the stratosphere, some 9 miles up: . SinisterLefty (talk) 03:08, 5 September 2019 (UTC)