Multiverses are pseudo science, secularist, ideology

[o_mlly]

No, that's not the logic.

The various multiverses are predictions or implications of physical theories. The logic is something like:

1. Theory X is a good explanation for a significant set of observations.
2. Theory X predicts or implies a multiverse.
3. If theory X is correct, the predicted multiverse is very probably correct.

What exactly is Theory X? If Theory X is the multiverse speculation then point 2 is tautological making point 3 a non-sequitur.

That unreferenced Weinberg quote doesn't give any indication of which theory he's talking about, so ¯\_(ツ)_/¯

? Weinberg clearly refers to Dawkins mulitverse theory as the subject for his comments in the text and in the video.

I hope that puts things in perspective for you.

Your Weinberg quotes serve to affirm his comments and his perspective on the multiverse as demonstrated in the video. In science, an open mind must be the default position for any claim not proven false. However, an examination of the probability for such a claim can discount one's openness as Weinberg does in the video by identifying for Dawkins the number of multiverses necessary, ie., 10^120.

 

[FrumiousBandersnatch]

What exactly is Theory X? If Theory X is the multiverse speculation then point 2 is tautological making point 3 a non-sequitur.

Theory X is some scientific theory that includes among its predictions or implications the existence of a multiverse. For example, the various inflation theories that explain a number of otherwise puzzling observations about the early development of the universe and its large scale features. After they were formulated, it was realised that the processes they describe to produce our universe would continue ad-infinitum, generating an infinite number of universes in the same way.

? Weinberg clearly refers to Dawkins mulitverse theory as the subject for his comments in the text and in the video.

Dawkins is a biologist, he doesn't have a multiverse theory and isn't an authoritative source on them. He was talking in general terms - there are theories that predict multiverses. Attribution apart, the options he set out are broadly correct. Weinberg said he thinks we may never have an answer, which is possible - there are no guarantees.

The video's conclusion is based on a probabilistic 'argument from incredulity' fallacy and a false dichotomy fallacy - the current lack of a definitive explanation for fine-tuning does not prove God-did-it. And, as I explained previously, God does not meet the criteria for a good explanation any better than magic. So the choices seem to be: 1. Brute fact or Theory of Everything - the constants could not be different, 2. Multiverse - weak anthropic principle, 3. Magic, or creator deity of choice. But, as Weinberg points out, we may never know.

 

[Hans Blaster]

This reply is more about the video and one particular clip, than your message, but you did post it and I want the link back to work...

At about 2 minutes in, the Narrator introduces the cosmological constant and says cosmologists say that it must be finely tuned. Then (transcribed):

The fine tunings.. how fine tuned are they?

Most of them are 1% sort of things. In other words if things are 1% different everything gets bad and the physicist could say 'maybe those are just, luck'.

On the other hand, this cosmological constant is tuned to 1 part in 10^120, 120 decimal places. Nobody thinks that's accidental. That is not a reasonable idea that something is tuned to 120 decimal places by accident. That's the most extreme example of fine tuning.

As I said before, Susskind is wrong (or had been edited so.) Here's why...

The quantity the cosmological constant is compared to is the vacuum energy density of empty space. Let's call that "V". When the theoretical physicists calculate it with their renormalization of infinity, they arise at the value V. If you plug that into the standard FLRW expansion metric for the Universe, you would see that V is a ridiculous value, causing the Universe to expand so rapidly nothing would have ever happened. As such most assumed that the true value was zero, and they just didn't know how to properly cancel the infinities.

When the cosmologists measure the acceleration of the expansion of the Universe and plugged it into the FLRW equation, the found a cosmological constant, L. When L was compared to V, they were very different, in fact:

L = V * 10^-120

This is not a "part in 10^120" error, but a multiplicative factor of 10^120 error. It is a question of accuracy, not precision.

If the calculated values are either: 0, or V, and the the measured value is V * 10^-120, then either the calculation is not done correctly, or missing important physics, or not even relevant in the first place.

A "part in 10^120" error would be if

V = 1.234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901

and

L = 1.234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678900

(I've intentionally created values with repeats so that you can see the difference in the last decimal place. Since units are arbitrary human inventions, I could always create units in which that *was* the value.)

The error, (L - V)/L = 0.000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001.

That's a "part in 10^120" error.

The Universe also isn't anywhere near as sensitive as a "part in 10^120 error" to the cosmological constant. Life would be unaffected if it were 0. It could at least double without harm to life either. There is an upper limit to the "life safe" values of the cosmological constant, but it is somewhere around "several times" the measured value.

[Beyond this, there is no know physics for *setting* the cosmological constant if it's not the vacuum energy, so we couldn't determine a random probability for any particular value, including the one we have.]

 

[o_mlly]

Isn't that the "god is a necessary being" argument?

He's not mentioned in the argument.

 

[o_mlly]

Theory X is some scientific theory that includes among its predictions or implications the existence of a multiverse. For example, the various inflation theories that explain a number of otherwise puzzling observations about the early development of the universe and its large scale features. After they were formulated, it was realised that the processes they describe to produce our universe would continue ad-infinitum, generating an infinite number of universes in the same way.

As a substitute for the illogic I suggested that underpins the multiverse speculation, the addition of a Theory X would put us into Bentham's "Nonsense on Stilts" category. We ought not lift up multiverse from its present lack of a foundation by adding yet another speculation to support it.

Dawkins is a biologist, he doesn't have a multiverse theory and isn't an authoritative source on them. He was talking in general terms - there are theories that predict multiverses. Attribution apart, the options he set out are broadly correct. Weinberg said he thinks we may never have an answer, which is possible - there are no guarantees.

In the video, Dawkins is a proponent of the multiverse speculation as an idea to refute the "fine tuned universe" argument. Weinberg's sober response is possible but highly not probable.

The video's conclusion is based on a probabilistic 'argument from incredulity' fallacy and a false dichotomy fallacy - the current lack of a definitive explanation for fine-tuning does not prove God-did-it. And, as I explained previously, God does not meet the criteria for a good explanation any better than magic. So the choices seem to be: 1. Brute fact or Theory of Everything - the constants could not be different, 2. Multiverse - weak anthropic principle, 3. Magic, or creator deity of choice. But, as Weinberg points out, we may never know.

The conclusion to the fine tuning argument is not necessarily that "God exists" but the probability that a "Fine Tuner" exists is extraordinarily high. We may call this "Fine Tuner" by His scientific name, "Brute Fact".

 

[Hans Blaster]

The conclusion to the fine tuning argument is not necessarily that "God exists" but the probability that a "Fine Tuner" exists is extraordinarily high. We may call this "Fine Tuner" by His scientific name, "Brute Fact".

That the Universe exists is a brute fact. The existence of a "fine tuner" is just a presumption -- one that rests on the, as yet to be demonstrated, notion that the Universe is finely tuned.

 

[Ponderous Curmudgeon]

The conclusion to the fine tuning argument is not necessarily that "God exists" but the probability that a "Fine Tuner" exists is extraordinarily high. We may call this "Fine Tuner" by His scientific name, "Brute Fact".

Only in respect to your presupposition that the unknown is indicative of your concept of a god, a totally unevidenced presupposition. Logic Fail

 

[FrumiousBandersnatch]

As a substitute for the illogic I suggested that underpins the multiverse speculation, the addition of a Theory X would put us into Bentham's "Nonsense on Stilts" category. We ought not lift up multiverse from its present lack of a foundation by adding yet another speculation to support it.

Inflationary theories, with their predictions of a multiverse, are already popular among cosmologists, who, no doubt, care not a jot what you think of them. Even the physicist you chose to quote has explained why he thinks the idea should be taken seriously. OTOH, I notice he didn't dissent from Dawkins brusque dismissal of the 'God hypothesis'.

The conclusion to the fine tuning argument is not necessarily that "God exists" but the probability that a "Fine Tuner" exists is extraordinarily high. We may call this "Fine Tuner" by His scientific name, "Brute Fact".

There may be a reason for the appearance of fine-tuning, but the fact is, we don't yet know what it is or even whether there is one.

Like it or not, predictions of a multiverse, based on the fundamental physics underlying our most successful physical theories, have some theoretical grounding and a degree of explanatory power - unlike fanciful speculations of supernatural entities for which there is no theoretical or evidential basis, and which have no more explanatory power than magic. YMMV.

 

[Bradskii]

As a substitute for the illogic I suggested that underpins the multiverse speculation, the addition of a Theory X would put us into Bentham's "Nonsense on Stilts" category. We ought not lift up multiverse from its present lack of a foundation by adding yet another speculation to support it.

Theory X is not an addition to the multiverse speculation. Theory X is the result of observations that lead to cosmic inflation. Which implies a multiverse. As in: 'I think these observations support the theory of cosmic inflation. And gee, I just realised an implication of that...'.

If you've got a sequence A B C D E F then there's no guarantee that the next letter will be G. But that sequence certainly implies it. So no proof. And hey, there are quite a few varieties of 'multiverse' in any case. None with proof.

And none which deny God either. Are you arguing purely on a scientific basis here (being a scientist yourself) or are you worried about what a multiverse would do to any of your beliefs? I'd be interested to know which ones.

 

[sjastro]

Why is the value of cosmological constant Λ so small?
We can start off with a Newtonian approximation for the ΛCDM Big Bang cosmological model.

If the universe is expanding uniformly according to Hubble’s law v = H₀r where v is the recession velocity, r is the radius of the universe and H₀ is Hubble’s constant.
The kinetic energy T of a receding galaxy is T = (1/2)mv² where m is the mass of the galaxy.
Since v = H₀r, T= (1/2)mH₀²r².

The total energy of the galaxy E is the kinetic energy plus the potential energy.
E = T + U where U is the potential energy.

If we assume the universe has a spherical mass distribution of mean density ρ and mass M = 4πr³ρ/3 and the galaxy is at a distance r from the “centre”, then the potential energy of the galaxy U is
U = -GMm/r = (-4/3)πGρmr².

The total energy of the galaxy is therefore
E = (1/2)mH₀²r² - (4/3)πGρmr² = mr²[(1/2)H₀² - (4/3)πGρ].

If the mass density of the universe is large enough expansion will stop.
For this to occur then E = 0 and the term in the square brackets is zero or ρₑ = 3H₀²/8πG where ρₑ is the critical density.
A universe is closed if ρ > ρₑ and open if ρ < ρₑ.

The density parameter Ω₀ is defined as Ω₀ = ρ₀/ρₑ = 8πG/3H₀²ρ₀ where ρ₀ is the current density of the universe.
The evidence shows the density parameter is very nearly Ω₀ =1 in which case 8πG = 3H₀²ρ₀ which becomes important when considering dark energy.

Dark energy in the form of a cosmological constant Λ comes from the the general relativity field equations.

Rₐₑ - (1/2)Rgₐₑ + Λgₐₑ = (8πG/c⁴)Tₐₑ

Λ is a repulsive force and –Λ is the corresponding attractive force.

Using the FLRW metric ds² = c²dt² -a(t)²(dσ²/(1-kσ²) + σ²dθ² + σ²sin²(θ)dψ²) where k is the curvature and a(t) the time dependant scale factor and plugging this metric into the field equations the Friedmann equations are obtained.

(a) [(da/dt)² +kc²]/a² - Λ/3 = 8ΠGρ/3
(b) (2d²a/dt²)/a + [(da/dt)² +kc²]/a² - Λ = -8ΠGp/c²

For a gravitationally bound flat universe da/dt = 0 and k = 0 hence equation (a) reduces to
-Λ = 8ΠGρ₀ for the current universe with density ρ₀.

However 8ΠGρ₀ = 3Ω₀H₀² as shown in the Newtonian approximation hence the value of Λ corresponding to the attractive gravitation of the current mass density ρ₀ is;
-Λ = 3Ω₀H₀² ≈ 1.1 x 10⁻⁵² c²m⁻².
In terms of the Planck length Lp where Lp = 1.6 x 10⁻³⁵ m
-Λ = 2.9 x 10⁻¹²² c²Lp⁻².

Irrespective of whether SI or Planck units are used Λ is an extremely small value for the observed value to be very nearly Ω₀ =1.

 

[Bradskii]

Why is the value of cosmological constant Λ so small?
We can start off with a Newtonian approximation for the ΛCDM Big Bang cosmological model.

If the universe is expanding uniformly according to Hubble’s law v = H₀r where v is the recession velocity, r is the radius of the universe and H₀ is Hubble’s constant.
The kinetic energy T of a receding galaxy is T = (1/2)mv² where m is the mass of the galaxy.
Since v = H₀r, T= (1/2)mH₀²r².

The total energy of the galaxy E is the kinetic energy plus the potential energy.
E = T + U where U is the potential energy.

If we assume the universe has a spherical mass distribution of mean density ρ and mass M = 4πr³ρ/3 and the galaxy is at a distance r from the “centre”, then the potential energy of the galaxy U is
U = -GMm/r = (-4/3)πGρmr².

The total energy of the galaxy is therefore
E = (1/2)mH₀²r² - (4/3)πGρmr² = mr²[(1/2)H₀² - (4/3)πGρ].

If the mass density of the universe is large enough expansion will stop.
For this to occur then E = 0 and the term in the square brackets is zero or ρₑ = 3H₀²/8πG where ρₑ is the critical density.
A universe is closed if ρ > ρₑ and open if ρ < ρₑ.

The density parameter Ω₀ is defined as Ω₀ = ρ₀/ρₑ = 8πG/3H₀²ρ₀ where ρ₀ is the current density of the universe.
The evidence shows the density parameter is very nearly Ω₀ =1 in which case 8πG = 3H₀²ρ₀ which becomes important when considering dark energy.

Dark energy in the form of a cosmological constant Λ comes from the the general relativity field equations.

Rₐₑ - (1/2)Rgₐₑ + Λgₐₑ = (8πG/c⁴)Tₐₑ

Λ is a repulsive force and –Λ is the corresponding attractive force.

Using the FLRW metric ds² = c²dt² -a(t)²(dσ²/(1-kσ²) + σ²dθ² + σ²sin²(θ)dψ²) where k is the curvature and a(t) the time dependant scale factor and plugging this metric into the field equations the Friedmann equations are obtained.

(a) [(da/dt)² +kc²]/a² - Λ/3 = 8ΠGρ/3
(b) (2d²a/dt²)/a + [(da/dt)² +kc²]/a² - Λ = -8ΠGp/c²

For a flat universe k = 0 and equation (a) reduces to
-Λ = 8ΠGρ₀ for the current universe with density ρ₀.

However 8ΠGρ₀ = 3Ω₀H₀² as shown in the Newtonian approximation hence the value of Λ corresponding to the attractive gravitation of the current mass density ρ₀ is;
-Λ = 3Ω₀H₀² ≈ 1.1 x 10⁻⁵² c²m⁻².
In terms of the Planck length Lp where Lp = 1.6 x 10⁻³⁵ m
-Λ = 2.9 x 10⁻¹²² c²Lp⁻².

Irrespective of whether SI or Planck units are used Λ is an extremely small value for the observed value to be very nearly Ω₀ =1.

Well, that's easy for you to say...

 

[o_mlly]

Susskind does use the "part in 10^120" language himself. Perhaps this is a limitation of his history in theoretical physics.

Weinberg, a theoretical physicist and Nobel Laureate in physics, also refers to the same improbability for the multiverse speculation as 1 in 10^120.

 

[o_mlly]

Only in respect to your presupposition that the unknown is indicative of your concept of a god, a totally unevidenced presupposition. Logic Fail

Perhaps a refresher course in mind-reading is in order.

 

[o_mlly]

That the Universe exists is a brute fact. The existence of a "fine tuner" is just a presumption -- one that rests on the, as yet to be demonstrated, notion that the Universe is finely tuned.

But you have no problem on the lack of demonstration with the notion of "multiverses"?

 

[o_mlly]

Inflationary theories, with their predictions of a multiverse, are already popular among cosmologists, who, no doubt, care not a jot what you think of them. Even the physicist you chose to quote has explained why he thinks the idea should be taken seriously.

It appears you watched a different video then the one I posted.

“I don’t think one should underestimate the fix we are in ... No one has constructed a theory in which that is true. I mean,, the (multiverse) theory would be speculative, but we don’t even have a theory in which that speculation is mathematically realized" (Weinberg).

 

[o_mlly]

I notice he didn't dissent from Dawkins brusque dismissal of the 'God hypothesis'.

Read the title of the thread. The theist's beliefs are irrelevant to the topic. I've noticed that when pressed to defend their unsupported speculations, the non-believers attempt to change the debate to a religious argument.

Like it or not, predictions of a multiverse, based on the fundamental physics underlying our most successful physical theories, have some theoretical grounding and a degree of explanatory power ...

The truth of of the multiverse speculation is not a matter of taste. Whether one like it or not does not alter its probability of existing. What problems, beyond countering the fine-tuning argument, does a multiverse speculation resolve in physics?

 

[durangodawood]

I don't get why a few Christians argue against this.

We are the only planet.
We're not? OK, but we're the centre of all the other ones.
Oh, we're not? But these planets are all there are.
There are more? Really. Oh, well this is the only galaxy.
You're kidding...how many? Wow, well this is the only universe.
There could be a multiverse? Hah! Prove it!

Where in any of that was God denied?

1. The multiverse possibility destroys a number of famous "proofs" of God and arguments for God.

2. Many Christians have resisted any cosmological notion that contradicts or adds to the account of the cosmos as literally presented literally in Genesis. Some Christians hold a more mythical view of the creation account, which is adaptable to new findings or possibilities. But many cling to a literalism which cant admit another universe(s).

 

[Hans Blaster]

But you have no problem on the lack of demonstration with the notion of "multiverses"?

Have I made some claim that they do exist?

If not, I see no problem with discussion of an idea (multiverse) that is consistent with other ideas in physics.

 

[o_mlly]

And none which deny God either. Are you arguing purely on a scientific basis here (being a scientist yourself) or are you worried about what a multiverse would do to any of your beliefs? I'd be interested to know which ones.

Being exposed hurts, doesn't it?

Multiverse as a place-marker to allow a model to be further examined is fine as long as we remember that multiverse remains an unsupported assumption in need of an observation. We already have an opinion from a Nobel Laureate that the speculation is next to impossible, ie, 1 out of 10^120. Or are you smarter than Weinberg?

 

[Hans Blaster]

However 8ΠGρ₀ = 3Ω₀H₀² as shown in the Newtonian approximation hence the value of Λ corresponding to the attractive gravitation of the current mass density ρ₀ is;
-Λ = 3Ω₀H₀² ≈ 1.1 x 10⁻⁵² c²m⁻².
In terms of the Planck length Lp where Lp = 1.6 x 10⁻³⁵ m
-Λ = 2.9 x 10⁻¹²² c²Lp⁻².

Irrespective of whether SI or Planck units are used Λ is an extremely small value for the observed value to be very nearly Ω₀ =1.

Given the ratio between Λ and the vacuum energy density (which I called "V" above), then it would seem that V ~ c²Lp⁻². This reeks of "naturalness" preference in field theory, a notion that unitless combinations and ratios of constants should be about 1. I'm not familiar with the calculations that went into deriving the vacuum energy, but given this I'm beginning to wonder...