tag:blogger.com,1999:blog-9163501679982013672.post2477990673313367364..comments2024-03-28T16:01:34.909+11:00Comments on Cosmic Horizons: The only thing that isn't moving at the speed of light is light itself!Cusphttp://www.blogger.com/profile/12515740423567038683noreply@blogger.comBlogger7125tag:blogger.com,1999:blog-9163501679982013672.post-19263772740495218172013-02-17T20:59:30.579+11:002013-02-17T20:59:30.579+11:00Oh.
"All reference frames"? Even the fr...Oh.<br /><br />"All reference frames"? Even the frame of the massive object itself? <br /><br />I have no doubt that you are right but the concept is hard to grasp.<br /><br />Ggreybeardhttps://www.blogger.com/profile/14936927497649860045noreply@blogger.comtag:blogger.com,1999:blog-9163501679982013672.post-31880842571907619622013-02-17T10:03:06.410+11:002013-02-17T10:03:06.410+11:00Just to be clear, massive objects moving at the sp...Just to be clear, massive objects moving at the speed of light through space-time, while photons move at zero, is seen in *all* reference frames :)Cusphttps://www.blogger.com/profile/12515740423567038683noreply@blogger.comtag:blogger.com,1999:blog-9163501679982013672.post-11653810707749934992013-02-16T22:18:35.879+11:002013-02-16T22:18:35.879+11:00Thanks, Geraint. :)
2. I am still battling with ...Thanks, Geraint. :) <br /><br />2. I am still battling with the concept that everything except a photon is travelling at the speed of light. Our everyday experience is of course the exact opposite. Is that my clue? <br /><br />Is it just a convenient way of saying that because light, (which travels at "c" in our frame of "0"), has it's own proper speed of zero; therefore to maintain the cosmic speed limit, everything else (in it's frame) must be travelling at ...errrmmm..."light speed"? <br /><br />Is it just simply a matter of deciding which of the two reference frames you are considering?<br /><br />:)Ggreybeardhttps://www.blogger.com/profile/14936927497649860045noreply@blogger.comtag:blogger.com,1999:blog-9163501679982013672.post-23989077813460999432013-02-16T19:02:41.898+11:002013-02-16T19:02:41.898+11:001) Yes, this is a reasonable way of looking at thi...1) Yes, this is a reasonable way of looking at things - there is no proper time for a photon, it is, in a rough sense, born and killed in the same instance. <br /><br />2) Sorry, this is something that physicists do - you set the problem out to be in units which makes the numbers easier to deal with. So, in relativity, we often set the speed of light, c, to 1, and then express all velocities relative to this. So, 1 means "at the speed of light"<br /><br />3) Relativity says so! Massless particles are "null" and so their speed is zero, and massive particles are "time-like" and have a velocity of 1. Tachyons (if they exist) are space-like and have velocities of -1!!<br /><br /><br />4) You have to remember that minus sign in the expression - the photon may trace out a change in distance (dx) and change in time (dt), but with the minus, on a photon path these cancel out, leaving the velocity zero.Cusphttps://www.blogger.com/profile/12515740423567038683noreply@blogger.comtag:blogger.com,1999:blog-9163501679982013672.post-11307024256820295632013-02-16T16:17:23.856+11:002013-02-16T16:17:23.856+11:00I struggle with some relativistic concepts (no - I...I struggle with some relativistic concepts (no - I'll be honest. I struggle with them all). I truly appreciate your efforts to explain them to lay persons who find the concepts interesting but elusively non-intuitive.<br /><br />1. "The speed that light travels through space-time is zero." - if I understand this correctly, this is because in the time frame of a photon, velocity is infinitely large and distance is infinitely small. In other words, magnetic radiation always reaches it's destination instantaneously (in its own reference frame).<br /><br />2. "Your motion through space-time is the speed of light." I am afraid I cannot see the reasoning behind this statement. You plonked a "1" on the right hand side of the equation and told us that represents "c"! Can you please expand a bit? <br /><br />3. Why does matter travel at "1" whilst photons travel at "0"? <br /><br />4. Your 3D space-time diagram shows particles, strings and branes meandering through two spacial dimensions and one time dimension. That is very clearly understandable but where does a photon sit in such a diagram? Surely it also travels through it at "c" not "o"?Ggreybeardhttps://www.blogger.com/profile/14936927497649860045noreply@blogger.comtag:blogger.com,1999:blog-9163501679982013672.post-7294283246308110082013-02-15T22:09:16.152+11:002013-02-15T22:09:16.152+11:00Alas, I think this is beyond control.Alas, I think this is beyond control.Cusphttps://www.blogger.com/profile/12515740423567038683noreply@blogger.comtag:blogger.com,1999:blog-9163501679982013672.post-13601024619236172662013-02-15T19:42:12.795+11:002013-02-15T19:42:12.795+11:00The problem with the long load time is back. This...The problem with the long load time is back. This occurs from time to time. Normally, the page loads in about a second. Today, 5 minutes. As always, Blogger blogs are affected.<br />Phillip Helbighttps://www.blogger.com/profile/12067585245603436809noreply@blogger.com