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Questions tagged [anthropic-principle]

This can be used for the strong or weak anthropic principle. Please be sure to mention in your question which you are talking about.

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Why am I a Boltzmann brain?

The Boltzmann brain hypothesis states that a big-bang-causing entropy fluctuation is larger than a brain-causing entropy fluctuation, therefore, you are much more likely to be a BB rather than a wet ...
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1answer
75 views

Why universe is so perfectly made for us? [duplicate]

I am very eager to learn that, "Why universe is so perfectly made for us?" Or our universe is just stable by chance?
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2answers
308 views

Is the universe really “fine-tuned for life”?

I understand what is meant when we say the universe is "fine tuned", but I've seen it claimed it's is fine tuned "for life". Is it? When I look at known or even speculated life in our universe, I see ...
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1answer
62 views

Would the universe be significantly different if neutrinos were massless?

As far as I know, neutrino oscillation experiments have fairly conclusively demonstrated that neutrino states have mass. However, neutrinos are so frequently taken to be massless in cosmology that I ...
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How fine-tuned is the expansion rate and the density of the universe?

I read somewhere that If the expansion rate of the universe were larger or the density of the universe were less , no galaxies would form. If the expansion rate of the universe were smaller or the ...
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1answer
67 views

Does ΛCDM imply infinitely many Boltzmann brains?

In this paper, Sean Carroll basically argues that the ΛCDM/'flat lambda' cosmological model has to be wrong since it implies that we're probably Boltzmann brains (and therefore shouldn't trust our ...
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1answer
70 views

Why does the lack of antimatter in the observable universe suggest a baryon asymmetry?

My title question relies on the answer to this question: Under the standard model and assuming baryon symmetry, is it possible (however unlikely) that some small local pocket of the universe might ...
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2answers
674 views

The Von Neumann-Wigner interpretation as the explanation for the fine-tuning problem and the existence of free-will [closed]

Disclaimer: Some of the concepts I'm using here are considered by some to be pseudo-science. I do not intend to have a hocus-pocus discussion and fairies and wizards here, my intention is to have a ...
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2answers
191 views

What makes '$c$' $c$? And what if it was slightly different? [duplicate]

I was thinking about what would be necessary to change to have a different value for $c$ (speed of light in vacuum, or speed of anything massless, or the one that seems most fundamental to me: he ...
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2answers
295 views

Vacuum energy and supersymmetry [closed]

Let us assume that dark energy is the energy of the vacuum. The density of this vacuum energy has been measured to be about $10^{-26}$ $kg/m^3$. Using the Compton wavelength formula, $\lambda=h/mc$, ...
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0answers
166 views

Why is Weinberg's prediction of omega sub lambda ($\Omega_{\Lambda}$) other than sophisiticated tautology?

I am not a physicist, but I do have a background in engineering (EE and computer science) and have followed physics and cosmology on a primarily conceptual basis for many years. I have looked at ...
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Is there any additional complexity in the physical laws that seems unnecessary for us to exist? [closed]

I am wondering if the universe is as simple as possible, at least given the constraint that humans exist on Earth. This is my second attempt at this question, which was marked as too broad, since I ...
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5answers
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Earth still exists - does this fact tell us anything about LHC safety?

When LHC was about to be launched there were many fears that it would destroy the world. To counter them scientists tried to carefully examine all possibilities and concluded that there is nothing ...
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2answers
3k views

Why do universal constants have the values they do?

This is meant to be a generic question of the type that we get repeatedly on this site, in different versions: The origin of the value of speed of light The gravitational constant G theoretically? ...
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0answers
59 views

Personalized “anthropic principle” and many-worlds divorce between Shroedinger's cats

Anthropic principle, at least in laymen explanations that I have encountered so far, sounds something like "the physical universe suits us exceptionally well because among all the possibilities we, ...
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1answer
586 views

Fine tuning: why is multiverse with anthropic principle considered a better explanation than anthropic principle alone?

I got the impression from several public lectures that, when it comes to the fine tuning problem, physicists tend to give multiverse together with anthropic principle as a plausible solution, but ...
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Pareto efficiency and Standard Model parameters

Pareto Efficiency is a well understood concept in economics, which basically is a condition where no one actor could be made better off without some one being made worse off. This condition allows ...
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4answers
2k views

Why aren't we Boltzmann brains in an infinite universe?

Either space is finite or it is infinite. a) - If space is infinite in extent, either it is thermal over an infinite volume, or it is in the vacuum state for most of it. If it is thermal, infinity ...
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1answer
242 views

Why doesn't the anthropic principle select for N=2 SUSY compactifications with an exactly zero cosmological constant?

The party line of the anthropic camp goes something like this. There are at least $10^{500}$ flux compactifications breaking SUSY out there with all sorts of values for the cosmological constant. Life ...
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1answer
442 views

What does anthropic mean as in Anthropic principle? [closed]

I'm reading a book about string theory, and it describes anthropic principle. Idea is clear to me, I understand this principle describes certain constants in modern physics that are so fine tuned as ...
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1answer
253 views

Is the only diffeomorphism invariant anthropic principle the final anthropic principle?

Quantum gravity is a gauge theory with the gauge symmetry spacetime diffeomorphisms. Presumably the quantum state of our universe is invariant under spacetime diffeomorphisms, including timelike ...
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1answer
347 views

Does a complete theory of quantum gravity require anthropic post-selection?

Does a complete theory of quantum gravity require anthropic post-selection? Certainly the black hole complimentarity and causal patch conjectures highlights the essential role of observers, at least ...
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1answer
305 views

Fine Tuned Universe

Is the fine tuning that cosmologists talk about (that our Universe is fine tuned for intelligent life) is the same as the fine tuning of the squared mass parameter of the Higgs in the Standard Model? ...
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6answers
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pros and cons of the anthropic principle

The anthropic principle has become a very popular explanation among theoretical physicists lately. Life is unlikely, but only life can observe, so we find ourselves in an unlikely position, so to ...
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3answers
192 views

Does the anthropic principle entail the existence of a huge multiverse? [closed]

As many cosmologists have pointed out, the universe is extremely fine-tuned for life in so many respects, and life, especially intelligent life, is extremely unlikely to emerge. The strong anthropic ...
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1answer
624 views

The measure problem in the anthropic principle

The anthropic principle is based upon Bayesian reasoning applied to the ensemble of universes, or parts thereof, conditioned upon the existence of conscious observers. That still leaves us with the ...
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6answers
2k views

Are many-worlds and the multiverse really the same thing?

Are many-worlds and the multiverse really the same thing? Not too long ago, Susskind and Bousso uploaded the article "The Multiverse Interpretation of Quantum Mechanics" with the thesis that the many-...
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2answers
530 views

Undergraduate-friendly reading material on the multiverse?

I'll be teaching a seminar for first-year undergraduates next year. The idea of my university's first-year seminar program is to expose students to exciting ideas and important texts in a somewhat ...
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6answers
687 views

Can (or How) Anthropic Principle be made into a scientific theory?

Anthropic Principle says physical Universe must be compatible with the conscious life that observes it. I thought it is just philosophy mumbo-jumbo and it's not physics. But I could be ...
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1answer
2k views

Where does the $10^{500}$ estimate for the number of stringy vacua come from?

This number is thrown around a lot so I'd like to understand its origin. I know that it counts compactifications of string theories on (not only) Calabi-Yau manifolds and probably also some other ...