The fundamental constants of nature must fall within a range
of values in order for the universe to develop structure and support life. This talk outlines the current constraints on these quantities and assesses the degree of tuning required for the universe to be viable. In the realm of particle physics, the relevant parameters are the strengths of the fundamental forces and the particle masses. Additional astrophysical parameters include the cosmic energy density, the cosmological constant, the abundances of baryons and dark matter, and the amplitude of primordial density fluctuations. These quantities are constrained by the need for the universe to live for a long time, emerge from its early epochs with an acceptable chemical composition, and successfully produce galaxies. On smaller scales, stars and planets must be able to form and function. The stars must have sufficiently long lifetimes and hot surface temperatures. We also consider potential fine-tuning related to the triple alpha reaction
that produces carbon, the case of unstable deuterium, and the
possibility of stable diprotons. For all of these issues, the goal is to delineate the range of parameter space for which universes can remain habitable. In spite of its biophilic properties, our universe is not optimized for the emergence of life, in that favorable variations could result in more galaxies, more stars, and potentially more habitable planets.
Some of the deepest questions in cosmology concern what features of our universe are generic and what are special, perhaps even in some sense "finely tuned" and "unlikely". Was the highly homogeneous state of the very early universe special in some sense (and so seemingly requiring explanation)? Do spacetimes such as ours generically possess black holes? To attempt to formulate such questions precisely and then address them requires probabilistic concepts and reasoning. Because of the peculiar and complex nature of the mathematical spaces involved in studying models of the universe in cosmology---generally, infinite-dimensional manifolds of a subtle type---standard forms of probabilistic concepts and reasoning do not apply: I state and sketch, in non-technical terms, the proof of a theorem whose natural interpretation is that there is, at present, no satisfactory framework for posing and addressing such questions about probability in the context of cosmology, not in any sense with pretensions of precision and rigor. Along the way, I explicate the role the topology of a probability space plays in these sorts of problems, an issue not adequately recognized in the literature on probabilistic reasoning, attending in particular to how this issue further complicates the problems in cosmology. I conclude by discussing the consequences for how we should assess the strength and, even more, the cogency of standard forms of argument in cosmology about what is "finely tuned" and therefore seems to call out for explanation.
So far, Earth is the only inhabited planet, even the only habitable planet we know of. Surprisingly, we still lack answers to some of the most fundamental questions about how it was assembled. In this talk I will summarize the state of our knowledge on building planets, informed by evidence from the solar system, observations of other young stellar systems, and extrasolar planets and will discuss how much fine-tuning - if any - the Solar System required.
Universe refers to reality as understood by the natural sciences. Are there any remaining questions at the limits of science? Cosmos invokes aesthetic appreciation or anthropological concerns. How can such elements exist in a universe understood by science? ‘Fine-tuning’ suggests there is someone setting the parameters, a creator behind the creation. How to think of these three views of reality? What does this imply about religion?
There is evidence that our universe is fine-tuned for life: if certain physical parameters were slightly different, life could not exist in our universe. It may also be that the universe is fine-tuned for life's origins. I claim that we don't yet have sufficient evidence that this is the case. I will discuss some hints that our universe is fine-tuned for both life and its origins, and end with some questions about the broader implications of either possible outcome: whether life in our universe is a pure chance phenomenon, or whether our universe is also fine-tuned for the origins of life.
As the past thirty years have revealed, the Galaxy—and by extension, the universe—is packed with planets. Yet at least for now, Earth is the only life-planet system we know of. Although drawing conclusions from a sample of one has well-known hazards, I want to suggest that the history of the Earth reveals several principles of life-planet development, and that these may allow tentative answers to three related questions. (1) Are other planets likely to be home to some form of life? (2) Are intelligent lifeforms that are capable and interested in observing the universe a typical outcome of planetary processes? And (3) what, if anything, might this imply about the fine-tuning of the universe?
Element generation in the Big Bang and in stars is a ?fine laboratory to test possible variations of the fundamental constants of the Standard Model. In this talk, I review the constraints from primordial nucleosynthesis on the electromagnetic ?fine-structure constant α_EM, the light
quark masses m_u; m_d; m_s and the CP-violating- Θ-parameter, with an emphasis on a thorough analysis of the systematic errors for the physical values of these parameters. Second, I discuss fine-tunings in the basic reactions generating the life-enabling elements carbon and oxygen via
the triple-alpha process and the radiative alpha-capture on carbon, the so-called holy grail of nuclear astrophysics. Finally, I also make contact to the anthropic principle.
Can we learn anything about the most basic fabric of the cosmos by inferring backward from what we see in the world, to an ‘ultimate ground’? In short – does reasoning about ‘grounding’ work, and what kind of fundamental truths could it tell us? More, if we found an ultimate ground – what kind of thing would it have to be?
A number of cultures have used an argument from counterfactual reasoning about the way a chaotic universe would be, to argue that there is a basic unified order at the ground of all things. On top of it, one Indian school of thought argued that the ground would equally determine, entail, and be characterized by all of reality’s contents, from matter to mathematics to meaning. Together these present not so much a ‘fine-tuning’ argument for a personal God’s telic plan to create life, as a ‘fine-tuning’ argument for a unified ordered of reality in which all kinds of things are equally contained. In this talk I will run through the argument and discuss its challenges and potential implications.
We discuss how a seeming fine tuning of some of the most important parameters of nature in reality follows from the consistency of fundamental physics. The two pressing examples we give are the dark energy and the CP-violating vacuum angle. In both cases, the fundamental consistency nullifies the fine tuning issue and results in the clearcut observational predictions that can be decisive for solving the fine tuning versus consistency dilemma.