Do we really know all the stuff infered by "runt

[nexium]

Not many years ago lack holes were hypothesis. Now Space.com is making unqualified statements. If matter in a thin accreation disk spirals in, why would not the planets of our sun spiral in toward the sun? Neil

 

[Saiph]

It's a matter of the size of the gravitational field.<br /><br />All orbiting objects are supposed to give of gravitational waves the same way charges moving in a circle give of electromagnetic radiation.<br /><br />However in nearly all cases this amounts to diddly squat in terms of energy. The earth doesn't really radiate much at all. The sun and earth are to small, and orbit to slowly, for this effect to be of any significance.<br /><br />However, things near a black hole orbit at near the speed of light, and can give of such gravitational radiation.<br /><br /><br />The other factor (and also a very, very important one a bit further away from the BH) is friction. The accretion disk is a huge mass of gas. As such it is very common for the gas particles to collide, and have some lose energy. By doing so they move further in, closer to the BH. The other one would gain energy, and move out, or get ejected (a source of material for BH jets for instance). These collisions also heat up the gas, causing it to radiate, and give quasars their characteristic spectra. <br /><br /><br />Once you get to more localized systems, like planets, where there isn't anything of comparable size for them to run into, the friction effect disappears. <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"This is my Timey Wimey Detector.  Goes "bing" when there's stuff.  It also fries eggs at 30 paces, wether you want it to or not actually.  I've learned to stay away from hens: It's not pretty when they blow" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>