The Big Bang

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Scienitific method

elerner said:
More important, “chronos” whoever he is, does not seem to know what the scientific method is. Science advances though theories that make quantitative predictions that can be validated by observation. That is what makes science useful. When a theory makes clear predictions which are contradicted by observation it is falsified and has to be rejected. Eric Lerner
This is where Eric Lerner starts to go wrong. Its a simplistic philosophy which Lerner shouldn't take as a guide. In practice science does not proceed in this fashion. Both Stephen Hawking and more recently Penrose (2005) have said so. Without going into it, it is the outdated outlook of the discredited philosopher Karl Popper.

Pete
 

Garth

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peter.mason3 said:
Without going into it, it is the outdated outlook of the discredited philosopher Karl Popper.
Pete
Hi Pete! Just as a matter of interest I would like you to go into it! How do you think science progresses?

Garth
 
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Popper vs Quine/Duhem

Everybody knows that it is a logical fallacy to assume that a hypothesis is proven true if its prediction is actually observed:

H -----> O
________O___
H

This commits the fallacy of affirming the antecedent because other possible theories might imply the same prediction.

Thus, Popper argued that if you can't prove theory to be true, you can at least prove that it is false:

H -----> O
_______~O____
~H

This is a logically valid form of argument called "modus tollens" that counts as logical proof--at least within logic and mathematics.

In the real world, however, things are not so clear-cut. According to the Quine/Duhem thesis, it is just as impossible to falsify a hypothesis based on not observing its predicted empirical observation as it is to prove that the hypothesis is true. That is because in every real world experiment, there are unspoken assumptions built into the theory itself and into the experimental setup:

H & (A1 & A2 & A3 . . . An) ----> O
____________________________~O____
~H OR (~A1 OR ~A2 OR ~A3 . . . OR ~An)

Indeed, is this not what happens in most normal science? That is, the experimental data is rejected instead of the iconic theory.

The fact is that what data there is can be show-horned to fit both the BB theory and the SS theory. We'll have to resort to other scientific virtues to settle the issue. Logical falsification won't work.
 

Garth

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WarrenPlatts said:
We'll have to resort to other scientific virtues to settle the issue. Logical falsification won't work.
Thank you Warren that is what I think, however I hope that the "other scientific virtues" do include experimental verification/falsification and astronomical observation. It is interesting to conjecture, for example, what will happen if the Gravity Probe B results are not as GR predicts but many sigma significance different from them? Are you suggesting another 'epicycle' will be added to the 'Mainstream Model'?

Garth
 
Hi Garth, I think Warren is right. I was just looking up what Hawking and Penrose said, if it helps.

In Hawking’s A Brief History of Time, Hawking writes, “As philosopher of science Karl Popper has emphasised,” a good theory is characterised by the fact that it makes a number of predictions that could in principle be disproved or falsified by observation….but if ever a new observation is found to disagree, we have to abandon or modify the theory.
Then immediately adds: “At least that is what is supposed to happen, but you can always question the competence of the person who carried out the observation.” Taking the example of Newton and Einstein’s theories of gravity, Hawking goes on to show how, “in practice” falsified theories tend to be modified or “extended” rather than abandoned.

Roger Penrose, in his 2004 The Road to Reality (not 2005 as I thought) says that Popper has “too stringent a criterion, and definitely too idealistic a view of science in this modern world of ‘Big science’.” (p1020).

I think WarrenPlatts is correct but in addition I'm think we may say we are always likely to find contradictions within a theory - it's really how they develop - at some points a new theory is required, at other points, the theory is itself develping and deepening. I don't think there's any doubt myself that the Big bang theory is relatively new and developing.

Pete
 
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Garth said:
It is interesting to conjecture, for example, what will happen if the Gravity Probe B results are not as GR predicts but many sigma significance different from them? Are you suggesting another 'epicycle' will be added to the 'Mainstream Model'?
Garth
Einstein has never been wrong before, has he? :uhh:
 

turbo

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peter.mason3 said:
I don't think there's any doubt myself that the Big bang theory is relatively new and developing.
Pete
Interesting...I tend to think of the BB model as pretty mature - like a wealthy dowager attended by a crew of cosmetologists (not cosmologists) busily trying to keep her looking attractive and play down her faults.

It's not just the liberal application of DM, DE, Higgs bosons, gravitons, etc, but the repeated invocations of things that are logically inconsistent with causality. The BB needs not only inflation, but also the perfect simultaneous ending of inflation in all parts of the universe that were no longer in causal contact when inflation ended. Then we get around 6Gy of cosmological expansion slowing under the force of gravitation until simultaneously, all the regions in all the universe decide to start start expanding at an accelerated rate. Who ordered that?

I prefer Popper's broad definition that ideas that cannot be falsified are not scientific. The statement "the sun circles around the moon" is patently false, but it has some value as a scientific statement precisely because it can be falsified. The concept that the BB universe underwent a period of super-luminal inflation that stopped simultaneously in an incredibly smooth, coordinated manner in all parts of the non-causally-connected universe is not a scientific one. It cannot be falsified.
 
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Garth

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WarrenPlatts said:
Einstein has never been wrong before, has he? :uhh:
About quantum mechanics?

Well, if not, then there is always a first time.....

Garth
 

Garth

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peter.mason3 said:
In Hawking’s A Brief History of Time, Hawking writes, “As philosopher of science Karl Popper has emphasised,” a good theory is characterised by the fact that it makes a number of predictions that could in principle be disproved or falsified by observation….but if ever a new observation is found to disagree, we have to abandon or modify the theory.
Then immediately adds: “At least that is what is supposed to happen, but you can always question the competence of the person who carried out the observation.” Taking the example of Newton and Einstein’s theories of gravity, Hawking goes on to show how, “in practice” falsified theories tend to be modified or “extended” rather than abandoned.
Roger Penrose, in his 2004 The Road to Reality (not 2005 as I thought) says that Popper has “too stringent a criterion, and definitely too idealistic a view of science in this modern world of ‘Big science’.” (p1020).
The water often gets muddy, nevertheless where two concordant theories are competing and one is clearly falsifiable and the other not, I believe the falsifiable one has the edge as far as good scientific practice is concerned.

But on the other hand why not go the whole way and join the Flat Earth Society!

Garth
 
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turbo

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Garth said:
About quantum mechanics?
Well, if not, then there is always a first time.....
Garth
After developing GR, Einstein spent the remainder of his life trying to replace it with a more general field theory that would encompass all of physics. If you read papers that he wrote when he was in his forties, you will see where he was headed:
Einstein "On the Ether" said:
Furthermore, in my opinion, we have not as yet succeeded in going beyond a superficial integration of the electromagnetic forces into the general scheme of relativity. The metric tensor which determines both gravitational and intertial phenomena on the one hand, and the tensor of the electromagnetic field on the other, still appear as fundamentally different expressions of the state of the ether; but their logical independence is probably more to be attributed to the imperfection of our theoretical edifice than to a complex structure of reality itself. ...(snipped discussion of magnetic fields being produced by the rotation of neutral bodies like the Earth and the Sun)... If we have just dealt with a case where the field theory in its present shape does not appear to be adequate, the facts and ideas that together make up quantum theory threaten to blow up up the edifice of field theory entirely.
Einstein would be the first to tell you that GR is an approximation that is predictive WRT gravitation, but that the theory is at best incomplete.
 
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Garth said:
where two concordant theories are competing and one is clearly falsifiable and the other not, I believe the falsifiable one has the edge as far as good scientific practice is concerned.
turbo-1 said:
If we live in an infinite steady state universe...
There's your problem. The infinite universe is unproven, and comes with a number of problems - contradictions - known since Newton's time. Newton proposed God held the stars from universal gravitational collapse. Trying to get round Olbers paradox, as Turbo-1 tried to do above, leads to some tricky, unproven stuff. Ditto gravitational collapse.
Now the infinite universe can in theory be falsified, although it cannot be proved. But it appears that the steady state theory(s) (by the admission of Hoyle, for instance, himself) have to keep being altered.
Now Hoyle is (was?) a great scientist, but once you start moving backwards, from the BB and from GR, towards Newton, in the face of an accumilation of evidence, which in historical terms will be seen as relatively new, I wonder if the steady staters' infinte universe is an attempt to disprove Popper, not prove him.
Pete
 
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turbo

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peter.mason3 said:
There's your problem. The infinite universe is unproven, and comes with a number of problems - contradictions - known since Newton's time.
Every cosmological model is unproven.

peter.mason3 said:
Newton proposed God held the stars from universal gravitational collapse. Trying to get round Olbers paradox, as Turbo-1 tried to do above, leads to some tricky, unproven stuff. Ditto gravitational collapse.
At the time of Newton, physicists were thinking of an ether as a rather passive thing. There was no inkling of quantum physics or of the physical properties of the quantum vacuum. The vacuum happens to have a couple of competing qualities that cancel to an incredible precision (~120 OOM). One is that the gravitational equivalence of the vacuum should have crushed the entire universe to about the diameter of the Earth, and the other is that the expansive pressure of the vacuum energy is 120 OOM larger than observed. If these estimates are to be believed, we must contend with the possibility that the expansive and gravitational forces of the vacuum are always and everywhere in dynamical equilibrium, and that the universe is stable against both collapse and the "big rip".

As for the "tricky" stuff, if light is redshifted by interacting with the EM fields in "empty" space, at some distance light will be redshifted out of detectability. What's tricky about that? The concept is very simple and fundamental and is entirely concordant with classical physics. I personally believe that light is redshifted as it traverses the EM field of the quantuum vacuum. Others have proposed that cosmological redshift results from inelastic collisions with molecules in the rarified plasma of "empty" space.
 
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Hi Turbo,
"Every cosmological model is unproven."

But you would admit that many cosmologists consider the standard big bang model proven, whether you agree or not with this.

But my point was rather that infinity is pretty unprovable.

Your solution to Olbers paradox seems tricky in the sense of both unproven, and sounds a little difficult to prove also.

As for the balance of quantum forces in the vacuum, as Newton said, re gravity, its a bit like imagining an infinity of needles balancing on their points.

I don't buy equilibrium.
cheers
Pete
 

Phobos

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Interesting tidbits, but the OP has been answered and now we're getting into non-mainstream & personal theories which, in accordance with PF policy, are to be presented in the IR forum.
 

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