tag:blogger.com,1999:blog-8625613341885362314.post8205452953372402217..comments2024-03-19T00:59:50.887-07:00Comments on Dear Planetary Astronomer Mike: Planetary Astronomy, Clouds, and the Space StationAnonymoushttp://www.blogger.com/profile/09811782087879425394noreply@blogger.comBlogger6125tag:blogger.com,1999:blog-8625613341885362314.post-8280733718773509362009-04-18T13:45:00.000-07:002009-04-18T13:45:00.000-07:00For our school sciece fair we are focusing on the ...For our school sciece fair we are focusing on the question why do the stars twinkle? I was wondreing if you could maybe share some info with us that would help with our project!<br />ThanksLittle Miss Room 18https://www.blogger.com/profile/05220025980339191727noreply@blogger.comtag:blogger.com,1999:blog-8625613341885362314.post-73459105143571284102009-03-29T13:04:00.000-07:002009-03-29T13:04:00.000-07:00Is this alo visible on google sky?Is this alo visible on google sky?TThttps://www.blogger.com/profile/15147175927877791153noreply@blogger.comtag:blogger.com,1999:blog-8625613341885362314.post-90694460338184478432009-03-12T08:43:00.000-07:002009-03-12T08:43:00.000-07:00@jmankoff:Actually, water and ice droplets do fall...@jmankoff:<BR/><BR/>Actually, water and ice droplets do fall - it's what we call "rain and snow". :)<BR/><BR/>The issue here is that the particle has to grow large enough that gravitational forces on it are stronger than inertial surface forces keeping it suspended in air. It's a bit like how a single speck of dust can float in a dust mote, while a lump of dirt will just fall to the ground.<BR/><BR/>This again has to do with the surface-area-to-volume ratio I mentioned in my explanation of the Poynting-Robertson effect:<BR/>http://dearplanetaryastronomermike.blogspot.com/2009/03/follow-up-when-stars-are-not-where-they.html<BR/><BR/>"Terminal velocity" is the maximum velocity a falling body can reach before air resistance keeps it falling at constant speed. It's directly proportional to the surface-area-to-volume ratio, and for very small, microscopic droplets (or dust specks) that terminal velocity is so small that the droplet essentially just moves with the surrounding parcel of air holding it. It's only when it grows large enough - and thus when the surface-area-to-volume ratio decreases enough - that it can overcome that atmospheric drag force and fall to Earth.<BR/><BR/>@w.w.i.i.g.g.s.s.:<BR/><BR/>Sound is just compression waves transmitted though a medium, most commonly air. The whole reason you hear, say, someone ringing a bell is because a resonating bell also resonates the air around it...those waves travel through the air, and start your eardrum resonating, which sends a signal to your brain. At the same time, the bell eventually stops ringing because the air around it is stealing energy of the bell's resonating motion.<BR/><BR/>In space, there is no air, so there's no sound to transmit. If someone bangs against the side of the space shuttle, the shuttle begins resonating...but there's no surrounding medium to steal energy from it, so it just continues resonating. <BR/><BR/>Eventually, though it's damped by internal inhomogeneities of the resonating object. If you imagine you fill a bell with foam or some other damping material, it would be pretty hard to ring it.<BR/><BR/>In practice, they introduce these internal inhomogeneities into spacecraft to do just that. There's a lot of sound-absorbing foam installed inside spacecraft to take on that energy-stealing role - and is exactly what they had to do for the Zvezda module when they realized it didn't have enough.<BR/><BR/>- Planetary Astronomer "In Space, No One Can Hear You Scream" Mike.Planetary Astronomer Mikehttps://www.blogger.com/profile/17634987043230222436noreply@blogger.comtag:blogger.com,1999:blog-8625613341885362314.post-86733778156776215832009-03-11T22:31:00.000-07:002009-03-11T22:31:00.000-07:00Cool stuff.Cool stuff.Space Mountain Manhttps://www.blogger.com/profile/08601530063058057125noreply@blogger.comtag:blogger.com,1999:blog-8625613341885362314.post-17486221724885087342009-03-11T11:48:00.000-07:002009-03-11T11:48:00.000-07:00Please expand on sound in space. A ringing bell th...Please expand on sound in space. A ringing bell that keeps ringing blows my mind.wwhhaatt??https://www.blogger.com/profile/08195545102701365027noreply@blogger.comtag:blogger.com,1999:blog-8625613341885362314.post-16997522751086831852009-03-10T15:47:00.000-07:002009-03-10T15:47:00.000-07:00Thanks for all your answers ... I have one follow ...Thanks for all your answers ... I have one follow up question: Why don't the water and ice droplets fall (or maybe when don't they fall and when do they?)jmankoffhttps://www.blogger.com/profile/01140958610146705422noreply@blogger.com