Movement

[zarnic]

Perhaps I'm jus' dense but ...&nbsp;if space is virtually a vacuum why show objects, such&nbsp;as asteroids, tumbling? <div class="Discussion_UserSignature"> <p><em>Wisdom doesn't automatically come with old age. Nothing does - except wrinkles.</em> A. Van Buren, 1978<br />* <em>An unbreakable toy is useful for breaking other toys.</em>  -- according to Van Roy</p> </div>

 

[bearack]

Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Perhaps I'm jus' dense but ...&nbsp;if space is virtually a vacuum why show objects, such&nbsp;as asteroids, tumbling? <br />Posted by zarnic</DIV><br /><br />I'm a simpleton and maybe that's my reasoning, but I don't quite understand your question. <div class="Discussion_UserSignature"> <p><br /><img id="06322a8d-f18d-4ab1-8ea7-150275a4cb53" src="http://sitelife.space.com/ver1.0/Content/images/store/6/14/06322a8d-f18d-4ab1-8ea7-150275a4cb53.Large.jpg" alt="blog post photo" /></p> </div>

 

[nimbus]

Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Perhaps I'm jus' dense but ...&nbsp;if space is virtually a vacuum why show objects, such&nbsp;as asteroids, tumbling? <br /> Posted by zarnic</DIV>Sounds like you see a contradiction between vacuum and conservation of spin.. Which is actualy contrary to reality: no ambient pressure means no friction, means nearly infinite conservation of angular momentum.<br /> <div class="Discussion_UserSignature"> </div>

 

[derekmcd]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Perhaps I'm jus' dense but ...&nbsp;if space is virtually a vacuum why show objects, such&nbsp;as asteroids, tumbling? <br /> Posted by zarnic</DIV></p><p>Aerodynamic forces don't play much of a role out in space where the medium is insignificant.&nbsp; Any spin and/or tumbling are imparted on object through other means.</p><p>Conservation of angular momentum is a major player for large objects that have spin such as the sun and earth.&nbsp; When these two were initially forming, they most likely started out as large flat disks with a relatively slow spin rate.&nbsp; As gravity takes over and particles in the center of that disk start gather into clumps, an accretion disk is formed.&nbsp; As matter is pulled in towards the central object, the spin rate increases due to conservation of angular momentum similar to how you see an ice skater pull their arms in while spinning and they speed up.&nbsp; </p><p>Tidal forces between two objects can also play a significant role on how an objects spins.&nbsp; This too is directly related to the conservation of angular momentum.&nbsp; Without the moon, the Earth would be spinning on it's axis considerably faster. </p><p>As for objects like asteroids, their spin or tumbling is imparted on them through collisions with other objects.&nbsp; Without any significant medium in space to create drag on the object, the spin or tumbling action will continue on until some other force changes it.</p> <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

 

[baulten]

What derekmcd said, basically.&nbsp; All objects must obey the law of the conservation of angular moment.&nbsp; They will continue to "spin" in space for a very long time.&nbsp; There is very little friction in space to slow them down, and tidal force take a long time to reduce that angular momentum.

 

[MeteorWayne]

Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>What derekmcd said, basically.&nbsp; All objects must obey the law of the conservation of angular moment.&nbsp; They will continue to "spin" in space for a very long time.&nbsp; There is very little friction in space to slow them down, and tidal force take a long time to reduce that angular momentum. <br />Posted by baulten</DIV><br /><br />Another process which slowly changes spin is absorbtion and reradiation of solar energy, mostly from the visible through infrared part of the EM spectrum. But like all other processes, they operate very slowly so basicically if an asteroid is whcked and starts spinning, it will do so for a looooong time. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[derekmcd]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Another process which slowly changes spin is absorbtion and reradiation of solar energy, mostly from the visible through infrared part of the EM spectrum. But like all other processes, they operate very slowly so basicically if an asteroid is whcked and starts spinning, it will do so for a looooong time. <br /> Posted by MeteorWayne</DIV></p><p>Radiation.&nbsp; Good point.&nbsp; I forgot about that one despite the recent topic we had going about albedo.&nbsp; I keep forgeting those pesky little photons have momentum.&nbsp; <img src="http://sitelife.space.com/ver1.0/content/scripts/tinymce/plugins/emotions/images/smiley-smile.gif" border="0" alt="Smile" title="Smile" /> </p> <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

 

[MeteorWayne]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Radiation.&nbsp; Good point.&nbsp; I forgot about that one despite the recent topic we had going about albedo.&nbsp; I keep forgeting those pesky little photons have momentum.&nbsp; <br />Posted by derekmcd</DIV><br /><br />Wiki has a pretty good article:</p><p>http://en.wikipedia.org/wiki/YORP_effect</p><p>&nbsp;</p><p>Coincidentally asteroid 54509 YORP has a "close" approach to earth at ~ 67X lunar distance on Aug 1</p><p>Actually it's not so much of a coincidence, since YORP passes near the earth every year near the beginning of August.</p> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[derekmcd]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Wiki has a pretty good article:http://en.wikipedia.org/wiki/YORP_effectCoincidentally asteroid 54509 YORP has a "close" approach to earth at ~ 67X lunar distance on Aug 1Actually it's not so much of a coincidence, since YORP passes near the earth every year near the beginning of August. <br /> Posted by MeteorWayne</DIV></p><p>Yeah.&nbsp; I already read that piece when we were talking about 'painting' asteroids.&nbsp;</p> <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

 

[zarnic]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Aerodynamic forces don't play much of a role out in space where the medium is insignificant.&nbsp; Any spin and/or tumbling are imparted on object through other means.Conservation of angular momentum is a major player for large objects that have spin such as the sun and earth.&nbsp; When these two were initially forming, they most likely started out as large flat disks with a relatively slow spin rate.&nbsp; As gravity takes over and particles in the center of that disk start gather into clumps, an accretion disk is formed.&nbsp; As matter is pulled in towards the central object, the spin rate increases due to conservation of angular momentum similar to how you see an ice skater pull their arms in while spinning and they speed up.&nbsp; Tidal forces between two objects can also play a significant role on how an objects spins.&nbsp; This too is directly related to the conservation of angular momentum.&nbsp; Without the moon, the Earth would be spinning on it's axis considerably faster. As for objects like asteroids, their spin or tumbling is imparted on them through collisions with other objects.&nbsp; Without any significant medium in space to create drag on the object, the spin or tumbling action will continue on until some other force changes it. <br />Posted by derekmcd</DIV></p><p>Ohhhhhh, I see. Thks all.<br /></p> <div class="Discussion_UserSignature"> <p><em>Wisdom doesn't automatically come with old age. Nothing does - except wrinkles.</em> A. Van Buren, 1978<br />* <em>An unbreakable toy is useful for breaking other toys.</em>  -- according to Van Roy</p> </div>