JohnSadlerAstro Posted August 12, 2016 Share Posted August 12, 2016 Hi everyone, I'm interested to hear fellow astronomer's thoughts on the theory of C-decay (the possibility of a decrease in the speed of light over the past). I've read somewhere that observations of the speed of light over the past 100 years show a definite decrease up to the current speed. I'm wondering what effect that could have on the so-called Doppler effect, as well, if the theory was correct. Could red-shift be caused by changes in the speed of light, not movement, or could it be a combination of both? It would be interesting to hear people's views on this. John 1 Link to comment Share on other sites More sharing options...
Spikey Posted August 12, 2016 Share Posted August 12, 2016 Pseudoscience nonsense straying into religion. I'm afraid neither have any place on SGL. Link to comment Share on other sites More sharing options...
Mr Spock Posted August 12, 2016 Share Posted August 12, 2016 Yes, complete nonsense and not worthy of discussion. Link to comment Share on other sites More sharing options...
JohnSadlerAstro Posted August 12, 2016 Author Share Posted August 12, 2016 Ok, Sorry if I said something that is against the rules, I'm not meaning to make religion part of the discussion at all--apparently this theory is held by many entirely secular scientists, not just religious ones, after all. As I'm not yet 16, I'm wanting to ask questions and form opinions of my own; is it wrong to question commonly held ideas? If Galileo hadn't done that, we might still think the Sun went round the Earth!!! John 2 Link to comment Share on other sites More sharing options...
Bonnylad Posted August 12, 2016 Share Posted August 12, 2016 1 hour ago, JohnSadlerAstro said: ... I've read somewhere that observations of the speed of light over the past 100 years show a definite decrease up to the current speed... apparently this theory is held by many entirely secular scientists... Once you enter into debate, you need to support any argument/viewpoint with evidence. 'Having read somewhere' and not producing links to any peer-reviewed material won't wash. As with your last phrase... apparently etc., just who are these peer-reviewed entirely secular scientists? It always helps to do research and see what actually debunks these young-earth creationist myths masquerading as science. Asking questions is fine - but research will take you out of the 'he said she said, apparently...' frame. You're always aiming for intellectual honesty. 2 Link to comment Share on other sites More sharing options...
JohnSadlerAstro Posted August 12, 2016 Author Share Posted August 12, 2016 Hi, The Russian paper, Physical Constants and the Evolution of the Universe [1987], by Vladimir G. Troitskii, of the Russian Academy of Sciences is one example of a secular scientist who supports CDK, he makes reference to papers by Bellert, 1977, and Mansfield and Malin, 1976. Although Troitskii does not support the Big Bang Theory, he is not religious in any way. As far as I can find, his paper has not yet been refuted by any other professional scientists, as all his arguments and results are scientific and sound. John 1 Link to comment Share on other sites More sharing options...
Floater Posted August 12, 2016 Share Posted August 12, 2016 3 hours ago, Spikey said: Pseudoscience nonsense straying into religion. I'm afraid neither have any place on SGL. 3 hours ago, Mr Spock said: Yes, complete nonsense and not worthy of discussion. Gentlemen, I am unqualified to enter this discussion. But I feel that the tenor of your responses is dismissive and high-handed. I fear the wrath of Mods but I am moved to point out that a question was posed and you have merely swept it aside. John mentions his age - which ought to be irrelevant here - but, nevertheless, warrants recognition. An inquisitive mind and, in this case, a young inquisitive mind, interrogating 'accepted wisdom' is to be encouraged, not slapped aside. As Bonnylad writes, prove your stance; refute the hypothesis, by all means. Think of all those who, in the past, were 'certain' and have proved merely to have been ignorant of the full picture. And my take on it is that more and more scientists are being honest and saying things like 'we think' this is what is happening or 'the evidence we have suggests'. To be so unremittingly dogmatic does not become you. 'There are more things in heaven and earth, Horatio, than are dreamt of in your philosophy.' 6 Link to comment Share on other sites More sharing options...
acey Posted August 13, 2016 Share Posted August 13, 2016 Variable speed of light (VSL) theories have been seriously looked at by a number of physicists. The idea does not currently have strong support but it certainly isn't pseudoscience. Usually the approach is to consider variation over time of a dimensionless combination of fundamental constants. The book Faster Than The Speed Of Light by Joao Magueijo (professor of theoretical physics at Imperial College) described work on the theory. https://en.wikipedia.org/wiki/Variable_speed_of_light https://en.wikipedia.org/wiki/João_Magueijo 1 Link to comment Share on other sites More sharing options...
Putaendo Patrick Posted August 13, 2016 Share Posted August 13, 2016 Vsevolod Sergeevich Troitskii (1913–1996) was a serious scientist with an impeccable CV. The article which John mentions is available at the SAO/NASA Astrophysics Data System (ADS) http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1987Ap&SS.139..389T&classic=YES and is well worth reading especially if you come to it with no preformed bias. Perhaps more like Copernicus than Galileo, Troitskii in his short article sought to provide a plausible mathematical explanation to certain problems. What he proposes is indeed elegant, although I think he would have agreed it is not the only possibility. The expression which comes to mind is "flying a kite" - let's see what happens and where (if anywhere) we can go with this. Barry Setterfield on the other hand seized on Tritskii's paper to spend the last thirty years or so building arguments which support his views as a young earth creationist. I don't have a horse in this particular race, but there is no doubt that by the standards of accepted scientific research, Setterfield has made a very large number of fundemental errors. Link to comment Share on other sites More sharing options...
Stu Posted August 13, 2016 Share Posted August 13, 2016 Good contributions all. Let's keep the thread heading down the serious science side and away from any creationist angle and I'm sure we can help John with his research further. Thanks all! 2 Link to comment Share on other sites More sharing options...
JohnSadlerAstro Posted August 13, 2016 Author Share Posted August 13, 2016 Hi, Thanks for the comments, guys! It looks like there are probably two theories here: The idea that: 1. The speed of light has decreased exponentially over time. Or the suggestion that: 2. Variations in the speed of light are possible and may happen. On the second point: On several threads on SGL I have noticed that people have mentioned the universe expanding faster than the speed of light. But in Hawking's The Universe in a Nutshell, he states that nothing can go faster than the speed of light. (I'd like to put in a quote here, but the book was borrowed from the library last year. ) Can anyone explain? John 1 Link to comment Share on other sites More sharing options...
Paul M Posted August 13, 2016 Share Posted August 13, 2016 (edited) 15 minutes ago, JohnSadlerAstro said: On the second point: On several threads on SGL I have noticed that people have mentioned the universe expanding faster than the speed of light. But in Hawking's The Universe in a Nutshell, he states that nothing can go faster than the speed of light. (I'd like to put in a quote here, but the book was borrowed from the library last year. ) Can anyone explain? John I'm no expert but my understanding is that cosmological expansion is quite different to simple regression. The farthest reaches of the Universe are not so much flying through apace at greater than light speed, this isn't allowed, but the intervening space is expanding. Don't ask me to explain the difference between the distance between objects and the space between them. Two different beasts I think. Edited August 13, 2016 by Paul M Link to comment Share on other sites More sharing options...
cloudsweeper Posted August 13, 2016 Share Posted August 13, 2016 As I understand it, the space between galaxies can expand faster than c, but this does not contravene the STR because it is not a physical object or info that is moving at such speeds. Doug. Link to comment Share on other sites More sharing options...
Alien 13 Posted August 13, 2016 Share Posted August 13, 2016 The one thing that confuses me is the term "the speed of light" speed is distance/time and time is not a constant and neither is distance with the expanding space, perhaps someone could invent a better term. Alan Link to comment Share on other sites More sharing options...
JohnSadlerAstro Posted August 13, 2016 Author Share Posted August 13, 2016 Hi, Sorry to be so slow, but surely increasing the space between two objects and moving them apart are the same? Is it that if both objects are moving at c in opposite directions, their speed relative to each other is 2 times c? John Link to comment Share on other sites More sharing options...
JohnSadlerAstro Posted August 13, 2016 Author Share Posted August 13, 2016 (edited) 13 minutes ago, Alien 13 said: The one thing that confuses me is the term "the speed of light" speed is distance/time and time is not a constant and neither is distance with the expanding space, perhaps someone could invent a better term. Alan Hi, I think the constant (supposing that the value of c is always the same) is the proportion of time and distance; i.e., the distance light travels per unit of time. As the two are in a direct relationship, if the time side of the proportion increases, so does the distance travelled. The proportion remains the same, so long as the same units for time and distance are maintained throughout. The distance travelled by light in 1 second is approximately 299,792,458 metres. Therefore the ratio, or proportion, of distance travelled to time is 299792458/1. This outs the speed of light at 299792458m/sec. Hope this makes sense! John Edited August 13, 2016 by JohnSadlerAstro Link to comment Share on other sites More sharing options...
cloudsweeper Posted August 13, 2016 Share Posted August 13, 2016 11 minutes ago, JohnSadlerAstro said: Hi, Sorry to be so slow, but surely increasing the space between two objects and moving them apart are the same? Is it that if both objects are moving at c in opposite directions, their speed relative to each other is 2 times c? John ...No. According to Special Relativity, relative velocity cannot exceed c. You can only do simple addition and subtraction of velocities at low, non-relativistic velocities. (But of course, for most practical purposes, things do not move at anything even approaching such velocities. A case where they do would be that of charged particles in an accelerator.) Doug. Link to comment Share on other sites More sharing options...
michaelmorris Posted August 14, 2016 Share Posted August 14, 2016 On 13/08/2016 at 09:53, JohnSadlerAstro said: Hi, Sorry to be so slow, but surely increasing the space between two objects and moving them apart are the same? Is it that if both objects are moving at c in opposite directions, their speed relative to each other is 2 times c? John Imagine a train travelling along a track between London and Bristol. It travels along the track at let us say 70 mph. Now imagine that the earth is expanding and the distance between London and Bristol keeps getting bigger (and the track expands at the same rate). Now the train is still travelling along the track at 70 mph. If the rate of expansion is 50mph, then the train would appear to an outside observer to be travelling at 50mph + 70 mph =120mph. In fact of course the train hasn't sped up, it is still travelling along the track at 70mph. Now substitute light for the train, the speed of light for the train's speed along the track, and space for the track. 3 Link to comment Share on other sites More sharing options...
JohnSadlerAstro Posted August 15, 2016 Author Share Posted August 15, 2016 Hi, I understand now!!! Thanks for the explanation. John Link to comment Share on other sites More sharing options...
Cornelius Varley Posted August 15, 2016 Share Posted August 15, 2016 On 14/08/2016 at 08:59, michaelmorris said: Imagine a train travelling along a track between London and Bristol. It travels along the track at let us say 70 mph. A train travelling between London and Bristol at 70mph ? In what universe are you living ? 1 Link to comment Share on other sites More sharing options...
michaelmorris Posted August 15, 2016 Share Posted August 15, 2016 1 hour ago, Cornelius Varley said: A train travelling between London and Bristol at 70mph ? I know, this is where my analogy falls down! 2 Link to comment Share on other sites More sharing options...
JohnSadlerAstro Posted August 16, 2016 Author Share Posted August 16, 2016 21 hours ago, Cornelius Varley said: A train travelling between London and Bristol at 70mph ? In what universe are you living ? Hi, Although the 'High Speed' trains running between Bristol and Paddington (via Chippenham!) are meant to have a top speed of 125 mph, with all the track works going on, you're likely to find yourself in a bus travelling down a winding D-road at not even quarter of that! The joys of rail replacement busses !!! John Link to comment Share on other sites More sharing options...
xanthic Posted August 18, 2016 Share Posted August 18, 2016 What mechanism limits the speed of light to c? Is that something that is understood? Link to comment Share on other sites More sharing options...
saac Posted August 18, 2016 Share Posted August 18, 2016 (edited) Yes the mechanism is understood, indeed very well understood. The Scottish physicist James Clerk Maxwell showed the way. Two properties of the universe in particular conspire to limit the speed at which any electromagnetic wave (not just light) can propagate through free space. Those two properties are: the permittivity of free space (εO) which regulates the propagation of the electric field, and the permeability ( µO ) which regulates the propagation of the magnetic field. The speed of light is related to those two universal constants as follows: c = 1/( εO µO)^0.5. Placing the values of εO = 8.8541878176 x10^-12 F/m and µO = 1.2566370614 x 10^-6 H/m fixes the value of C at approximately 3 x 10 ^8 m/s. So in effect, it is a property of the very stuff that the universe is made from that limits the speed at which light may pass through it; it (the universe) simply does not allow light to propagate any faster. Jim Edited August 19, 2016 by saac 3 Link to comment Share on other sites More sharing options...
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