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Author Topic:   What Properties Might Light of Millennia Past Have that Today's Doesn't?
JonF
Member (Idle past 282 days)
Posts: 6174
Joined: 06-23-2003


Message 51 of 170 (674547)
09-30-2012 9:51 AM
Reply to: Message 50 by Percy
09-30-2012 9:28 AM


"Tired light" and the various theories that c was different in the past (e.g. Setterfield) are two very different and independent things.
Tired light is the theory that light loses energy as it travels. No matter what its speed.

This message is a reply to:
 Message 50 by Percy, posted 09-30-2012 9:28 AM Percy has replied

Replies to this message:
 Message 53 by Percy, posted 09-30-2012 12:48 PM JonF has not replied

  
JonF
Member (Idle past 282 days)
Posts: 6174
Joined: 06-23-2003


Message 73 of 170 (674698)
10-01-2012 8:48 PM
Reply to: Message 72 by LimpSpider
10-01-2012 8:14 PM


Re: Really?
Asking questions which you may never have asked yourself?
Perhaps you shoould have asked if we had considered the possibility of a change in c?
The answer to that question is yes.

This message is a reply to:
 Message 72 by LimpSpider, posted 10-01-2012 8:14 PM LimpSpider has replied

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 Message 74 by LimpSpider, posted 10-01-2012 8:54 PM JonF has not replied

  
JonF
Member (Idle past 282 days)
Posts: 6174
Joined: 06-23-2003


Message 88 of 170 (674756)
10-02-2012 3:56 PM
Reply to: Message 86 by foreveryoung
10-02-2012 3:34 PM


I don't care how many times it has been repeated; it is merely your assertion and nothing more. All of the constants are derived from a deeper reality and they don't change alone but in tandem. This tandem change keeps all the ramifications that you insist would happen from happening.
Nobody has yet been able to find a set of changes, in tandem or not, that are consistent with observations. That includes you. For some specifics, here's physicist Steve Carlip on Barry Setterfield's "theory" and stars and planets:
quote:
Here's the upshot. The minimum number N of nucleons (protons and neutrons) needed for a star to "ignite" goes as (a/a_G)^{3/2}. From point (1), Setterfield's a is constant; from point (4), his a_G goes as 1/c^2. Hence his N goes as c^3. The present value of N is a few percent of the number of nucleons in the Sun. Thus in Setterfield's model, an increase in c by a factor of a little more than 2 will turn off the Sun. Setterfield has various "fits'' of the rate of change of c, but by my reading this would have been about 1000 years ago. I think it would have been noticed.
You get an even more dramatic dependence on c if you ask about the energy output, or luminosity, of a star. This goes as (a_G)^4 (see Barrow and Tipler, section 5.6), or, in Setterfield's model, c^{-8}. A 10% change in c would thus cut the luminosity of the Sun by a factor of two. Setterfield would have this happen in the past 600 or 700 years, I think. Again, it would have been noticed.
You run into the same sort of problem if you look at the sizes of planets. A planet is in equilibrium when gravitational attraction, which changes in time according to Setterfield, balances repulsive forces, which don't. The radius of a planet depends on quantities that vary, in Setterfield's model, as (a_G)^{-1/2}(m_e)^{-1}, where m_e is the mass of an electron (see Barrow and Tipler, section 5.3). This varies, according to Setterfield, as c^3. Thus a 10% decrease in the speed of light -- in the past 700 years! -- would have meant about a 30% decrease in the radius of the Earth. Again, this would have been noticed.
And here he is again, on various aspects:
quote:
There is overwhelming evidence that the speed of light (c) has not changed substantially in a very long time.
Let's start with the most precise. Atoms emit light at certain precise energies, which are determined by a constant called the fine structure constant, a (that should really be alpha, but ASCII doesn't do Greek). Now, a=e^2/hc, where e is the charge of an electron and h is Planck's constant. Changes in c would result in corresponding changes in a, which would in turn shift spectra. It's slightly more complicated than that (observed spectra are also affected by red shift, so you need to compare different spectral lines to extract the fine structure constant), but still fairly straightforward. Such observations give a limit on the change in c of less than about a part in 10^15 per year, over most of the history of the Universe.
Now, you can try to get around this by suggesting that h or e also change, in exactly the right way to cancel changes in c. But that would mean that any clock based on electromagnetic interactions (quartz clocks, atomic clocks, etc.) would give the usual, unchanged speed of light; more on this below.
Next, consider radioactive decay. For a period after the initial explosion of a supernova, much of the energy that emerges that we observe comes from the radioactive decays of cobalt-56 and cobalt-57. These decays can be identified because they emit gamma rays of very precise frequencies, which are easily detectable. We've looked at the decay rates from the most recent nearby supernova, SN1987A, and they're exactly the same as the ones we observe in the laboratory. But the decay rates go as c^4, so c cannot have changed significantly.
Again, you can try to get around this by suggesting that some other constant -- in this case, the Fermi constant -- also changes, in exactly the right way to cancel changes in c. But that would mean that any clock based on weak interactions would give the usual, unchanged speed of light.
Next, consider electron-positron annihilation. This process results in the emission of two gamma rays, with energies E=mc^2, where m is the electron mass. Changing c would change this energy. Observations of such annihilation radiation from fairly large distances -- the center of our galaxy, for example, which is about 30,000 light years away -- gives a limit on changes in c. It's much weaker than the limits from observing spectra, but it's still easily strong enough to exclude any "drastic" change.
Again, you can try to get around this by suggesting that m also changes, in exactly the right way to cancel changes in c. But this would mean that any clocks based on such annihilation processes would give the usual, unchanged speed of light.
Next, consider gravitational processes. Fusion in a star depends on a delicate balance between gravity and electromagnetism. A star must have a large enough mass to overcome the electric repulsion between protons, allowing them to get close enough to fuse; but a star that is too heavy becomes unstable against radiation pressure. A fairly easy calculation -- see Weisskopf, Science 187 (2/75) 605 for a beautiful explanation that uses only fairly elementary physics -- shows that a normal star must have between about 10^56 and 10^59 nucleons. But this number goes as c^3/2, so relatively small changes in c would, essentially, put out the stars. Things get even worse if you also have masses changing with time to keep the electron-positron annihilation energy consistent with observation; then you get a variation that goes as c^3 instead. It's even worse if you look at the luminosity rather than just the stability of stars. A 5% increase in c would dim the Sun enough to freeze the Earth's oceans, while a 12% decrease or so would boil the oceans. You run into the same problem if you look at the radii of planets, which depend on a balance between gravity and various repulsive atomic forces. This balance depends on the speed of light; changes in c by a few percent would change the radius of the Earth by a few percent (which would have been noticed!).
Again, you can try escape by suggesting that something else -- in this case, Newton's gravitational constant -- also changes, in exactly the right way to cancel changes in c. But this would mean that any gravitational clocks would give the usual, unchanged speed of light.
In short, a huge number of observations (I've given only a sample) rule out any significant changes in the speed of light. In each case, you can evade the conclusion only by postulating that other constants change in just the right way to cancel the effects. But in the end,that means that any *physical measurement* of c would show no change. Similarly, if you use this to argue for a young Earth, you end up with a theory in which the Earth is "young" but all possible measurements of its age give an "old" answer. The kindest thing I can say about that is that it requires one to use definitions of words like "young" and "old" that have little to do with their usual meanings. ("I'm only 24 minutes old, because what you call a year is what I call 30 seconds.")
The takeaway is that you don't just claim "in tandem" and walk away. You have to do calculations and demonstrate that the changes you propose are in accordance with our observations. This isn't a simple task (Setterfield's been trying for decades and hasn't succeeded yet). And you have to know a lot of physics just to know what observations are relevant and must be addressed (as you can see from the above, the ramifications spread into areas you might not consider without the appropriate knowledge)
Oh, and here's a link to one of Steve's articles on universal constants. Well worth reading, with a link to a significantly technical paper on the subject.

This message is a reply to:
 Message 86 by foreveryoung, posted 10-02-2012 3:34 PM foreveryoung has replied

Replies to this message:
 Message 91 by foreveryoung, posted 10-03-2012 12:25 AM JonF has replied

  
JonF
Member (Idle past 282 days)
Posts: 6174
Joined: 06-23-2003


(1)
(1)
Message 94 of 170 (674803)
10-03-2012 8:32 AM
Reply to: Message 91 by foreveryoung
10-03-2012 12:25 AM


If changes in the constants would show its effects no matter how the constants change in time, it should be a simple matter for you to show mathematically that there exists no such arrangements of constants that are changing in time that could produce a universe with no known effects.
I don't think so, but maybe. I haven't made any such claim. I claim that nobody has been able to come up with a set of changes that are not falsified by observation, and that's trivially true. I think that there is no such set of changes, but I can't prove it and I'm not claiming that there is no such set.
It is fairly well known that if all the constants that govern nuclear and atomic interactions changed, the result would be a universe that would be indistinguishable from the one we live in now. The trick is to find a set of constants in which at least one does not change, but others do, and produce the result you want.
The fact of the matter is that such changes in the constants have indeed produced visible effects on our universe. Those changes are 1.an enormous amount of radioactive decay in a very short time. 2. Starlight that has reached us from a distance that in an amount of time that would be impossible to replicate today. 3. Accelerated plate tectonics that occurred in much shorter time than would be possible with today's rates.
Those are not facts, they are wild and unsupported claims.
I'm quite familiar with the Accelerated Nuclear Decay (AND) claims. The major problem (but far from the only problem) with AND is that it would have left subtle effects that we would detect except for the fact that the surface of the Earth would be molten and we and all life would have been killed twice over by radiation and charbroiling. This is acknowledged by the few YECs who understand radioactivity, and no matter what a bold face they try to put on it the only way out is multiple miracles-to-order. See RATE in Review: Unresolved Problems. Probably the second most difficult issue is how the decay rates of many different processes that come under the umbrella of "radioactive decay" could have changed in such a way to provide the observed overwhelming agreement between dating methods based on those different processes.
The second and third claims have similar problems, especially the macroscopic plate tectonics lunacy (It could be very amusing to see you try to link fundamental constants to continents reeling and careening like drunken ballerinas, but I know you won't try). I'm not going to go into them unless you show some signs of discussing and supporting your claims.
You've made three claims in that message and supported none of them. Fish or cut bait, sonny.

This message is a reply to:
 Message 91 by foreveryoung, posted 10-03-2012 12:25 AM foreveryoung has replied

Replies to this message:
 Message 100 by foreveryoung, posted 10-03-2012 11:40 PM JonF has replied

  
JonF
Member (Idle past 282 days)
Posts: 6174
Joined: 06-23-2003


(3)
(1)
Message 105 of 170 (674921)
10-04-2012 8:57 AM
Reply to: Message 100 by foreveryoung
10-03-2012 11:40 PM


Those are not facts, they are wild and unsupported claims.
If those claims are unsupported then your claims are just as unsupported. Saying your claims are supported doesn't fly with me.
And yet you ignored the support I provided for the fact that there has been no accelerated radioactive decay. Here's more, from The Constancy of Constants, Part 2 by physicist Steve Carlip:
quote:
First, the physics of radioactive decay is quite well understood. ...
As described above, the process of radioactive decay is predicated on rather fundamental properties of matter. In particular, in order to explain old isotopic ages on a young Earth by means of accelerated decay, an increase of six to ten orders of magnitude in rates of decay would be needed.
Now, the fundamental laws of physics, as we presently understand them, depend on about 25 parameters, such as Planck's constant h, Newton's gravitational constant G, and the mass and charge of the electron, and a change in radioactive decay rates would require a change in one or more of these constants. The idea that these constants might change over time is not new, and is certainly not restricted to creationists. Interest in this question was spurred by Dirac's "large number hypothesis." The "large number" in question is the ratio of the electric and the gravitational force between two electrons, which is about 10^40; there is no obvious explanation of why such a huge number should appear in physics. Dirac pointed out that this number is nearly the same as the age of the Universe in atomic units, and suggested in 1937 that this coincidence could be understood if fundamental constants -- in particular, Newton's gravitational constant G -- varied as the Universe aged. The ratio of electromagnetic and gravitational interactions would then be large simply because the Universe is old. Such a variation lies outside ordinary general relativity, but can be incorporated by a fairly simple modification of the theory. Other models, including the Brans-Dicke theory of gravity and some versions of superstring theory, also predict physical "constants" that vary.
Frankly, physicists are not, for the most part, interested in silly creationist arguments. But they are interested in basic questions such as whether physical constants or laws change in time -- especially if such changes are proposed by such a great physicist as Dirac. As a result, there has been a great deal of experimental effort to search for such changes. A nice (technical) summary is given by Sisterna and Vucetich, Physical Review D41 (1990) 1034 and Physical Review D44 (1991) 3096; a more recent reference is Uzan, Reviews of Modern Physics 75 (2003) 403, available electronically at The fundamental constants and their variation: observational status and theoretical motivations. Among the phenomena they look at are:
  • searches for changes in the radius of Mercury, the Moon, and Mars (these would change because of changes in the strength of interactions within the materials that they are formed from);
  • searches for long term ("secular") changes in the orbits of the Moon and the Earth --- measured by looking at such diverse phenomena as ancient solar eclipses and coral growth patterns;
  • ranging data for the distance from Earth to Mars, using the Viking spacecraft;
  • data on the orbital motion of a binary pulsar PSR 1913+16;
  • observations of long-lived isotopes that decay by beta decay (Re 187, K 40, Rb 87) and comparisons to isotopes that decay by different mechanisms;
  • the Oklo natural nuclear reactor (mentioned in another posting);
  • experimental searches for differences in gravitational attraction between different elements (Eotvos-type experiments);
  • absorption lines of quasars (fine structure and hyperfine splittings);
    laboratory searches for changes in the mass difference between the K0 meson and its antiparticle;
  • searches for geological evidence of "exotic" decays, such as double beta decay of Uranium 238 or the decay of Osmium to Rhenium by electron emission, which are impossible with the present values of basic physical constants but would become possible if these changed;
  • laboratory comparisons of atomic clocks that rely on different atomic processes (e.g., fine structure vs. hyperfine transitions);
  • analysis of the effect of varying "constants" on primordial nucleosynthesis in the very early Universe.
While it is not obvious, each of these observations is sensitive to changes in the physical constants that control radioactive decay. For example, a change in the strength of weak interactions (which govern beta decay) would have different effects on the binding energy, and therefore the gravitational attraction, of different elements. Similarly, such changes in binding energy would affect orbital motion, while (more directly) changes in interaction strengths would affect the spectra we observe in distant stars.
The observations are a mixture of very sensitive laboratory tests, which do not go very far back in time but are able to detect extremely small changes, and astronomical observations, which are somewhat less precise but which look back in time. (Remember that processes we observe in a star a million light years away are telling us about physics a million years ago.) While any single observation is subject to debate about methodology, the combined results of such a large number of independent tests are hard to argue with.
The overall result is that no one has found any evidence of changes in fundamental constants, to an accuracy of about a part in 10^11 per year. There are some recent, controversial claims of observational evidence for changes in certain constants (notably the "fine structure constant") in the early Universe, but these are tiny, and would have minimal effects on radioactive decay rates.
So the idea that decay rates could vary enough to make a significant difference to measurements of ages is ruled out experimentally.
Don't forget to check out that link before you claim "no evidence" again.
BTW "The earth is orders of magnitude younger than 4.56 billions years old, therefore there has been accelerated radioactive decay." is just your opinion, not evidence.
Edited by JonF, : No reason given.

This message is a reply to:
 Message 100 by foreveryoung, posted 10-03-2012 11:40 PM foreveryoung has not replied

  
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