L. Susskind -- The "Megaverse"

[sol invictus]

I've already answered it. See above:

"The fine-tuned Universe is the proposition that the conditions that allow life in the Universe can only occur when certain universal fundamental physical constants lie within a very narrow range".

Only they aren't constant, and they don't lie within a very narrow range, so that's the end of that. Bye-bye Goldilocks multiverse. Bye-bye woo.

Because you apparently really actually don't get this, I'll explain. The value of alpha at zero energy is a constant - roughly 1/137. Physics depends on that value in a certain way. If you change that value a little, bye bye life (or at least that's the claim).

By the way, the variation of alpha over the range of energies relevant to biology is tiny, and well within the uncertainty allowed by such arguments.

 

[Farsight]

Because you apparently really actually don't get this, I'll explain. The value of alpha at zero energy is a constant - roughly 1/137.

Sol, that's like saying a variable is a constant whatever value it happens to be wherever/whenever we are located. It just doesn't stand up.

Physics depends on that value in a certain way. If you change that value a little, bye bye life (or at least that's the claim).

It's an unfounded claim sol, and a dishonest one because the people who make the claim keep quiet about running constants.

By the way, the variation of alpha over the range of energies relevant to biology is tiny, and well within the uncertainty allowed by such arguments.

One could advance an anthropic Goldilocks argument about anything. Like the Earth must be round because if it was flat all the air would fall off the edge, and we wouldn't be here. See criticisms.

 

[Reality Check]

"The fine-tuned Universe is the proposition that the conditions that allow life in the Universe can only occur when certain universal fundamental physical constants lie within a very narrow range".

Only they aren't constant, and they don't lie within a very narrow range, so that's the end of that. Bye-bye Goldilocks multiverse. Bye-bye woo.

Only that is the "lies to children" (simplified) version of the fine-tuned universe because it denies that our universe has life in it (no constants = no life) !

So all you have is a semantic argument that is quite ridiculous.

The better version is that the "The fine-tuned Universe is the proposition that the conditions that allow life in the Universe can only occur when certain universal fundamental physical constants lie within a very narrow range" where these can be running constants (which are not constant!) and thus are taken at zero energy where they are constants.

The fact is that scientists use these certain universal fundamental physical "constants" to set limits on the possibility of life in any universe (including ours).
Hello Goldilocks multiverse. Hello scientific hypothesis. Hello Fine-tuned Universe (and the ability to click on links, Farsight )

The fine-tuned Universe is the proposition that the conditions that allow life in the Universe can only occur when certain universal fundamental physical constants lie within a very narrow range, so that if any of several fundamental constants were only slightly different, the Universe would be unlikely to be conducive to the establishment and development of matter, astronomical structures, elemental diversity, or life as it is presently understood.[1]

And fundamental physical constants

αs, the coupling constant for the strong force (≈1)
...
The best known of the dimensionless constants is the fine structure constant:

where e is the elementary charge, ħ is the reduced Planck's constant, c is the speed of light in a vacuum, and ε0 is the permittivity of free space. The fine structure constant is fixed to the strength of the electromagnetic force. Note that at low energies, α ≈ 1/137, whereas at the scale of the Z boson, about 90 GeV, one measures α ≈ 1/127.

(also not a constant!)

 

[Reality Check]

Sol, that's like saying a variable is a constant whatever value it happens to be wherever/whenever we are located. It just doesn't stand up.

Farsight, it is a scientific fact that "The value of alpha at zero energy is a constant - roughly 1/137".

It is a scientific fact that if you change the value of alpha at zero energy then you change the value of alpha for all energies.

It is an actual fact that there exists a claim that "If you change that value a little, bye bye life": Fine-tuned Universe

It is an obvious fact that if you change the fine-structure constant enough then atoms do not exist and thus life does not exist.

It is an actual fact that the scientists who talk about fine-tuning know that running constants exist, i.e. that the fine-structure constant is not actually a constant. And that this does not matter unless you think that life can exist in conditions comparable to the beginning of the universe (energies of GeV).

 

[sol invictus]

Sol, that's like saying a variable is a constant whatever value it happens to be wherever/whenever we are located. It just doesn't stand up.

Sure it does, as long as you specify where you are located (in this case, at zero energy). Call it a constant or not, I don't care - that's semantics. The point is the value of alpha at zero energy is a well-defined quantity that (rather strongly) affects the laws of physics. Change it, and you change physics and biology.

It's an unfounded claim sol, and a dishonest one because the people who make the claim keep quiet about running constants.

Nonsense. They don't mention the running because it's irrelevant. As for "unfounded", that's an assertion with no evidence.

 

[Farsight]

A "constant" that isn't constant isn't something you can dismiss as mere irrelevant semantics, sol. It's the dagger in the heart of Goldilocks multiverse. It shows that there are no foundations to this unscientific untestable hypothesis, whereupon the whole castle-in-the-air comes crashing down. But then I suppose some people will defend it to their dying breath. Such is life. People do so love their woo.

 

[edd]

Farsight: do you think there is a minimum value of the fine structure constant and if so what is it?

 

[Acleron]

Sol, that's like saying a variable is a constant whatever value it happens to be wherever/whenever we are located. It just doesn't stand up.
It's an unfounded claim sol, and a dishonest one because the people who make the claim keep quiet about running constants.

One could advance an anthropic Goldilocks argument about anything. Like the Earth must be round because if it was flat all the air would fall off the edge, and we wouldn't be here. See criticisms.

A constant is a constant as defined, otherwise you could claim that the speed of light in a vacuum is not a constant because light is slower in glass.

 

[Perpetual Student]

One cannot cut through leather with a dull blade -- Mr. Duffield simply does not get it. End of story.

 

[sol invictus]

A "constant" that isn't constant isn't something you can dismiss as mere irrelevant semantics, sol. It's the dagger in the heart of Goldilocks multiverse. It shows that there are no foundations to this unscientific untestable hypothesis, whereupon the whole castle-in-the-air comes crashing down. But then I suppose some people will defend it to their dying breath. Such is life. People do so love their woo.

You didn't address anything in my post, Farsight.

Do you or do you not acknowledge that if the value of the fine structure constant at zero energy were different, the world and the laws of physics would be different too?

 

[Farsight]

A constant is a constant as defined, otherwise you could claim that the speed of light in a vacuum is not a constant because light is slower in glass.

Where have you been? I'm forever pointing to the Einstein quotes and the scientific evidence of NIST optical clocks and the Shapiro delay to try to get these guys to appreciate that the speed of light in vacuo varies with gravitational potential. People think the fine structure constant varies with gravitational potential too, see the abstract of SpaceTime Mission: Clock Test of Relativity at Four Solar Radii. Also see this section of the Wikipedia fine-structure-constant article.

Farsight: do you think there is a minimum value of the fine structure constant and if so what is it?

It's hard to say, edd. It's said to range between 1/128 and 1/137.035999074(44), and the latter is described as the "zero energy value". But if you were to get away from the Earth, then the Sun, then the Milky Way galaxy, I imagine you'd measure a lower value. Then if you waited a few billion years, I imagine you'd measure it lower still. It comes back to that "strength of space" thing I referred to with reference to energy density and dark energy and f(R) theories, and the way Einstein referred to a field as a state of space.

 

[Farsight]

One cannot cut through leather with a dull blade -- Mr. Duffield simply does not get it. End of story.

I get it. You hide behind anonymity and make snide remarks, and cling to your fine-tuned constants and multiverse fairytale regardless of what I tell you about running constants.

You didn't address anything in my post, Farsight.

Yes I did. You attempted to dismiss running constants as mere semantics. I knocked that on the head.

Do you or do you not acknowledge that if the value of the fine structure constant at zero energy were different, the world and the laws of physics would be different too?

See what I said to edd above, and replace "zero energy" with "ambient energy". Also strike out "the laws of physics", because the running of the fine-structure constant is not something illegal. That apart, yes, if the fine structure constant had a different value, things would be different. But one thing wouldn't be different: there would still be some Perpetual Student warbling on about the multiverse.

 

[sol invictus]

That apart, yes, if the fine structure constant had a different value, things would be different.

Then you have just admitted that all your nonsense was, in fact, nonsense. The fact that alpha runs doesn't change the fact that the value of alpha at zero energy is what it is, and different values would give different physics (and arguably preclude life).

 

[Reality Check]

It's hard to say, edd. It's said to range between 1/128 and 1/137.035999074(44), and the latter is described as the "zero energy value".

No "said" abut it Farsight. Fine structure constant

The currently accepted value of α is 7.2973525698(24)×10−3 = 1/137.035999074(44).[1][2]
...
While the fine-structure constant is known to approach 1/128 at interaction energies above 80 GeV,[11]

It's But if you were to get away from the Earth, then the Sun, then the Milky Way galaxy, I imagine you'd measure a lower value.

Your imagination and what evidence, Farsight?

Then if you waited a few billion years, I imagine you'd measure it lower still.

Your imagination and what evidence, Farsight?

The fact is that there is no evidence of the Fine structure constant varying in either space or time. There are observations that place upper limits on these variations, e.g.

In 2008, Rosenband et al.[36] used the frequency ratio of Al

+​

and Hg

+​

in single-ion optical atomic clocks to place a very stringent constraint on the present time variation of α, namely Δα̇/α = −1.6±2.3×10−17 per year. Note that any present day null constraint on the time variation of alpha does not necessarily rule out time variation in the past. Indeed, some theories[37] that predict a variable fine-structure constant also predict that the value of the fine-structure constant should become practically fixed in its value once the universe enters its current dark energy-dominated epoch.

Then It comes back to that "strength of space" thing I referred to with reference to energy density and dark energy and f(R) theories, and the way Einstein referred to a field as a state of space.

It comes back to that nonsense about an undefined "strength of space" and some fantasies about things that nothing to do with this thread and an obsession with old quotes by Einstein.

BTW Einstein was right - a field is a "state of space" (not that term appears on your citation) and time. Field

A field is a physical quantity that has a value for each point in space and time.[1]

 

[Xulld]

Fascinating topic, I have not read all 6 pages, just the first few posts. I have my own opinion and it mirrors some in the sense this is philosophy more than science.

I think in some sense we can gain perspective through science fiction. What makes this topic fascinating is our awe of our own significance.

Intelligence is a complex set of interactions when viewed on any scale we can comprehend.

If we propose for a minute an unconstrained set of all possible universes one can imagine, where perhaps entities exist that make human intelligence look like an ant in comparison, then how much less unlikely is the proposition that we live in a universe in which human intelligence is possible?

It seems to me the wider the net we cast the less compelling the question becomes.

I believe it is also a question of complex interaction more than what we might call intelligence. I think even now far more common is an under valuing of lesser complexities, perhaps intelligence exists where now we lack an appreciation.

I also often wonder if the question is flawed from an even more fundamental perspective. Perhaps universes simply cannot exist without electrons? Perhaps the set really is small and we just have nothing to prove that is true?

 

[Xulld]

Fascinating topic, I have not read all 6 pages, just the first few posts. I have my own opinion and it mirrors some in the sense this is philosophy more than science.

I think in some sense we can gain perspective through science fiction. What makes this topic fascinating is our awe of our own significance.

Intelligence is a complex set of interactions when viewed on any scale we can comprehend.

If we propose for a minute an unconstrained set of all possible universes one can imagine, where perhaps entities exist that make human intelligence look like an ant in comparison, then how much less unlikely is the proposition that we live in a universe in which human intelligence is possible?

It seems to me the wider the net we cast the less compelling the question becomes.

I believe it is also a question of complex interaction more than what we might call intelligence. I think even now far more common is an under valuing of lesser complexities, perhaps intelligence exists where now we lack an appreciation.

I also often wonder if the question is flawed from an even more fundamental perspective. Perhaps universes simply cannot exist without electrons? Perhaps the set really is small and we just have nothing to prove that is true?

There can be an infinity of apples without having any oranges.

 

[lpetrich]

Farsight's main argument on the fine structure constant is to quote sources like this NIST page: Current advances: The fine-structure constant. However, he continues with ignoring discussions of why it is variable, including calculations of its variability as a function of interaction energy.

I think that there some evidence of fine tuning, but I also think that our Universe is borderline habitable. Nearly all of it is inhospitable to humanity. I think that this is what we might expect of a multiverse with lots of different low-energy-physics limits. The large majority of universes would be uninhabited, with the inhabited ones being borderline habitable.

As to our Universe being intelligently designed, for all we know, our Universe could be part of a lab experiment in making universes. That is also consistent with the Universe being borderline habitable -- the experimenters haven't figured out a simple way to make a super habitable Universe.

 

[Farsight]

Oh boy, now it isn't just the multiverse, now it's intelligent design. Sheesh. lpetrich, look at what you're saying.

By the way, I haven't ignored discussions about why the fine structure constant is variable. That's physics, that's science. The multiverse isn't.

 

[lpetrich]

There is some evidence of fine tuning in the properties of various elementary particles and atomic nuclei, but there are lots of different ways that complicated structures can emerge, so it may be difficult to argue absolute fine tuning.

For atoms and molecules, we don't depend on having a precise value of the fine structure constant, only on having a value that's much less than 1. In fact, atomic and molecular structure is largely derived from electrons having spin 1/2 and thus being fermions. Nuclei also enter into that structure, but only as tiny opposite-charged objects much more massive than electrons.


It's hadrons and nuclei where we see the real fine tuning.

First, hadrons. The are only two long-lived ones, protons and neutrons, or collectively, nucleons. They are very close in mass because the up and down quarks are much less massive than the color-confinement energy scale. Color confinement forces these quarks to be in a much smaller size (about 10^(-15) m) than their Compton wavelengths (about 10^(-13) m). If one works out a "bag model" approximation, where quarks with mass m are confined within a radius R, then their energy is
E = ()/R + ()*m + ...

This is from quarks having Dirac wavefunctions -- that's why we don't get ()*m^2/R + ...

The ()'s are quantities that are approximately 1, quantities that I won't go through the trouble to calculate here.

The electromagnetic self-energy is ()*alpha/R.

At least in the electrostatic limit, the electromagnetic self-energy is larger for protons than for neutrons. But neutrons are more massive than protons. That implies that the down quark is more massive than the up quark, and odd circumstance. For the other quarks, it's the reverse: the charm quark is more massive than the strange quark, and the top quark more massive than the bottom quark.

If the color-confinement energy is much less than the mass of the least massive quark, then the lowest-energy state will be three quarks with that flavor with spins aligned, making total spin 3/2. The next states up in energy will be excited states of that system. It may make "molecules", but I'm not sure about that.


String theory yields the Standard Model by symmetry breaking, but that symmetry breaking is a function of the space-time topology. Different topologies will yield different low-energy limits, and assessing the habitability of universes with these various limits will be *very* difficult. So I'm not going to get into that aspect of the problem.

 

[Farsight]

I think it's best to start with electrons and protons, lpetrich. Then move on up to the hydrogen atom, then take it from there. The free neutron isn't stable, and unless you've got some clarity with the simple stuff you're on tricky ground with heavy nuclei.

Re topologies, look to TQFT, and think along these lines: different particles are different topologies, or different "field structures". Multiverses just don't come into it. If you want to talk fine structure to me, I'd be grateful if you did it on the other thread - I think this thread has run its course anyway. But I have to say I'm pushed for time at the moment. I can't talk much.