tag:blogger.com,1999:blog-2259795590215649830.post1317042606870331816..comments2010-04-12T08:01:44.477-04:00Comments on The Tall Pale Physicist's Blog: Gravitational Waves, a Whole Other SpectrumTall Pale Jasonhttp://www.blogger.com/profile/07604021768548703310noreply@blogger.comBlogger9125tag:blogger.com,1999:blog-2259795590215649830.post-73776674663141742402009-02-16T15:14:00.000-05:002009-02-16T15:14:00.000-05:00Ugh, I just read my posted comment and my grammar ...Ugh, I just read my posted comment and my grammar is terrible. Sorry about that.Tall Pale Jasonhttps://www.blogger.com/profile/07604021768548703310noreply@blogger.comtag:blogger.com,1999:blog-2259795590215649830.post-72006231963450368352009-02-16T15:10:00.000-05:002009-02-16T15:10:00.000-05:00I should say as physical laws go, that information...I should say as physical laws go, that information can't travel faster than the speed of light is of a higher order than a given theory of gravity or than most scientific theories for that matter. This is a result we have never yet found to be incorrect and every way we look at it, it comes out the same. This idea is what led Einstein to create GR. When applying the idea to gravity as curvature, think of this mind game. Imagine a sheet stretched out. If I hold my finger down on one part of the sheet, a curvature is induced. If I then lift my finger, the sheet does not immediately go back to being flat but takes time for the effect to be felt everywhere. Thus, information about curvature travels at or below the speed of light. This is exactly why I specify information rather than light. Information is a far broader concept and it's technically more accurate to say that information can't travel faster than the speed of light than to say particles or light can't travel faster than the speed of light. <BR/><BR/>In a sense, your question about gravity being built into the rest of the forces has some merit. If you look at my equation of the geodesic (the one with the 'x's and dots), that equation describes how a particle moves in the absence of force but in a curved spacetime. You know it is in the absence of forces because it equals zero. To add forces, I would simply replace the zero with the value of the force. So in a sense, you intuition about gravity being built in is right - however, as a relativist, I would see it exactly inverse of that! :-)<BR/><BR/>As to Stephen Hawking's recent public talk, he was discussing information in general (remember this should be regarded a a theory of a higher order) and the mechanism by which information is retrieved can be through gravitational radiation or through the three "real forces". While this isn't my field, I believe I have a cursory understanding of the problem (though don't quote me on this). If you imagine a spherical black hole and some matter falls into it, there is a great deal of information connected to that matter. Now we state that the interior of a black hole (inside the event horizon) is causally disconnected to the exterior (meaning the inside does not affect the outside). So it would seem that information is lost a matter falls into a black hole. Just as we tend to think information travels at the speed of light, we tend to also think information is preserved so it would seem ideas of matter falling into a black hole and ideas of the conservation of information are at odds with each other. However, as the matter falls into a black hole, the matter leaves a change in the shape of the event horizon. You could imagine individual particles leaving little bumps on the event horizon. These bumps would fade over time. My interpretation of what Hawking's said was that the information in these bumps is preserved and can be retransmitted - through both gravitational radiation and more traditional "force-based" radiation. Thus the existence of black holes does not conflict with the conservation of information.<BR/><BR/>Great questions!Tall Pale Jasonhttps://www.blogger.com/profile/07604021768548703310noreply@blogger.comtag:blogger.com,1999:blog-2259795590215649830.post-48142589438267382192009-02-13T14:38:00.000-05:002009-02-13T14:38:00.000-05:00Dude this is awesome...took me a while to comprehe...Dude this is awesome...took me a while to comprehend with leave in London and large amounts of booze getting in my way. Maybe I didn't read carefully enough still, but I'm confused about one thing. If gravity is not a force but curvature of space time, then why does information about it need to travel at light speed? If the sun disappeared, wouldn't Earth automatically fly off the hinge rather than waiting eight minutes to do so? No force, no causality, no waves? Is there a difference between gravity and information about it. I feel like you satisfactorily explained gravity by declassifying it as a force but then used used force-logic to describe it. If it's not a force, shouldn't it rather be a constant built into the three other forces?<BR/><BR/>Also, with gravitational radiation, is this what Hawking means when he says information is retained in black holes and is this how it gets out?<BR/><BR/>Sorry if all of this sounds really dumb...thanks if you take time to respond to us simple folk! :-) Plus I'm scared that if you get mastery over of gravity it'll be a big advantage you'll have over me in universe domination.Scott Bohlingerhttps://www.blogger.com/profile/16421289031251633045noreply@blogger.comtag:blogger.com,1999:blog-2259795590215649830.post-44116089628820611932009-02-02T18:02:00.000-05:002009-02-02T18:02:00.000-05:00This comment has been removed by a blog administrator.Mohamedhttps://www.blogger.com/profile/14625410152094305159noreply@blogger.comtag:blogger.com,1999:blog-2259795590215649830.post-61087326424732519412009-02-02T15:39:00.000-05:002009-02-02T15:39:00.000-05:00Sorry, I wasn't thinking. Comment was removed to ...Sorry, I wasn't thinking. Comment was removed to comply.Tall Pale Jasonhttps://www.blogger.com/profile/07604021768548703310noreply@blogger.comtag:blogger.com,1999:blog-2259795590215649830.post-40376949010160627132009-01-27T14:28:00.000-05:002009-01-27T14:28:00.000-05:00You shouldn't identify people on the internets.You shouldn't identify people on the internets.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-2259795590215649830.post-11792334169142079992009-01-25T01:59:00.000-05:002009-01-25T01:59:00.000-05:00This comment has been removed by the author.Tall Pale Jasonhttps://www.blogger.com/profile/07604021768548703310noreply@blogger.comtag:blogger.com,1999:blog-2259795590215649830.post-81870444324817626582009-01-24T23:45:00.000-05:002009-01-24T23:45:00.000-05:00I've got to say, I kind of lost interest around "T...I've got to say, I kind of lost interest around "These are Maxwell's equations". <BR/><BR/>"gravitational information on the position of masses is not instantly available" - so does this mean if we were to suddenly, say, remove the sun, its effect on the earth wouldn't be felt immediately, but rather since the gravity wave goes at the speed of light, the effect would be felt at exactly the moment we saw the sun disappear, even though the actual removal happened like 8 minutes ago?Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-2259795590215649830.post-86862922568179063462009-01-21T20:17:00.000-05:002009-01-21T20:17:00.000-05:00I'd invite anyone who looks at this to post questi...I'd invite anyone who looks at this to post questions and comments on anything they feel needs more explanation / needs a better explanation. Doing so will help me better develop this discussion and the talk I am developing to go along side this.Tall Pale Jasonhttps://www.blogger.com/profile/07604021768548703310noreply@blogger.com