DOCSLIB.ORG

Boltzmann Brain from Wikipedia, the Free Encyclopedia

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text

Load more

Boltzmann brain From Wikipedia, the free encyclopedia A Boltzmann brain is a hypothesized self-aware entity that arises due to random fluctuations out of a state of chaos. The idea is named for the physicist Ludwig Boltzmann (1844–1906), who advanced an idea that the Universe is observed to be in a highly improbable non-equilibrium state because only when such states randomly occur can brains exist to be aware of the Universe. The term for this idea was then coined in 2004 by Andreas Albrecht and Lorenzo Sorbo.[1] The Boltzmann brains concept is often stated as a physical paradox. It has also been called the "Boltzmann babies paradox".[2] The paradox states that if one considers the probability of our current situation as self-aware entities embedded in an organized environment versus the probability of stand-alone self-aware entities existing in a featureless thermodynamic "soup", then the latter should be vastly more probable than the former. Contents 1 Boltzmann brain paradox An image of Ludwig Boltzmann, for whom 2 Proposed resolutions Boltzmann brains are named 3 See also 4 Notes 5 References Boltzmann brain paradox The Boltzmann brains concept has been proposed as an explanation for why we observe such a large degree of organization in the Universe (a question more conventionally addressed in discussions of entropy in cosmology). Boltzmann proposed that we and our observed low-entropy world are a random fluctuation in a higher-entropy universe. Even in a near-equilibrium state, there will be stochastic fluctuations in the level of entropy. The most common fluctuations will be relatively small, resulting in only small amounts of organization, while larger fluctuations and their resulting greater levels of organization will be comparatively more rare. Large fluctuations would be almost inconceivably rare, but are made possible by the enormous size of the Universe and by the idea that if we are the results of a fluctuation, there is a "selection bias": we observe this very unlikely Universe because the unlikely conditions are necessary for us to be here, an expression of the anthropic principle. If our current level of organization, having many self-aware entities, is a result of a random fluctuation, it is much less likely than a level of organization which only creates stand-alone self-aware entities. For every universe with the level of organization we see, there should be an enormous number of lone Boltzmann brains floating around in unorganized environments. In an infinite universe, the number of self-aware brains that spontaneously and randomly form out of the chaos, complete with memories of a life like ours, should vastly outnumber the brains evolved from an inconceivably rare local fluctuation the size of the observable Universe. The Boltzmann brain paradox is that any observers (self-aware brains with memories like we have, which includes our brains) are therefore far more likely to be Boltzmann brains than evolved brains. So this refutes evolution in multiverses. It also refutes the anthropic principle and even multiverses altogether: Why should we accept the anthropic principle, or indeed any argument, if it just popped up randomly into our Boltzmann brain? No argument is reliable in a Boltzmann brain universe. Proposed resolutions One class of solutions to the question of why we don't appear to be Boltzmann brains makes use of differing approaches to the measure problem in cosmology: in infinite multiverse theories, the ratio of normal observers to Boltzmann-brain observers depends on how infinite limits are taken. Measures might be chosen to avoid appreciable fractions of Boltzmann brains.[3][4][5] Sean M. Carroll and colleagues have suggested that the formulation of the Boltzmann-brain problem is mistaken.[6][7] In particular, they claim that a quiescent de Sitter space does not actually have quantum fluctuations, because "[q]uantum fluctuations require time-dependent histories of out-of-equilibrium recording devices, which are absent in stationary states".[6]:1 Given quantum field theory in curved spacetime, a patch of de Sitter space can form only a small, finite number of Boltzmann brains as it approaches the vacuum.[6]:3–4 This argument relies on the many-worlds interpretation of quantum mechanics, and other interpretations likely would still yield Boltzmann brains.[6]:28 See also Brain in a vat Observer (physics) Bekenstein bound Matrioshka brain China brain Simulated reality Dream argument Simulation hypothesis Evolution of biological complexity Swampman Notes 1. Albrecht, Andreas; Sorbo, Lorenzo (September 2004). "Can the universe afford inflation?". Physical Review D. 70 (6). arXiv:hep-th/0405270 . Bibcode:2004PhRvD..70f3528A. doi:10.1103/PhysRevD.70.063528. Retrieved 16 December 2014. 2. "Boltzmann babies in the proper time measure". eScholarship. 2008-07-14. Retrieved 2011-08-22. 3. Andrea De Simone; Alan H. Guth; Andrei Linde; Mahdiyar Noorbala; Michael P. Salem; Alexander Vilenkin (14 Sep 2010). "Boltzmann brains and the scale-factor cutoff measure of the multiverse". Phys. Rev. D. arXiv:0808.3778 . Bibcode:2010PhRvD..82f3520D. doi:10.1103/PhysRevD.82.063520. 4. Andrei Linde; Vitaly Vanchurin; Sergei Winitzki (15 Jan 2009). "Stationary Measure in the Multiverse". Journal of Cosmology and Astroparticle Physics (01). arXiv:0812.0005 . Bibcode:2009JCAP...01..031L. doi:10.1088/1475-7516/2009/01/031. 5. Andrei Linde; Mahdiyar Noorbala (9 Sep 2010). "Measure problem for eternal and non-eternal inflation". Journal of Cosmology and Astroparticle Physics (09). arXiv:1006.2170 . Bibcode:2010JCAP...09..008L. doi:10.1088/1475-7516/2010/09/008. 6. Kimberly K. Boddy; Sean M. Carroll; Jason Pollack (1 May 2014). "De Sitter Space Without Quantum Fluctuations". arXiv:1405.0298 . 7. Grossman, Lisa (14 May 2014). "Quantum twist could kill off the multiverse". New Scientist. Retrieved 9 January 2015. References "Disturbing Implications of a Cosmological Constant", Lisa Dyson, Matthew Kleban, and Leonard Susskind, Journal of High Energy Physics 0210 (2002) 011 (at arXiv (http://arxiv.org/ab s/hep-th/0208013)) "Can the universe afford inflation?", Andreas Albrecht and Lorenzo Sorbo, Physical Review D 0 (2004) 063528 (at arXiv (http://arxiv.org/abs/hep-th/0405270)) "Is Our Universe Likely to Decay within 20 Billion Years?", Don N. Page, (at arXiv (http://arxiv.org/abs/hep-th/0610079)) "Sinks in the Landscape, Boltzmann Brains, and the Cosmological Constant Problem", Andrei Linde, Journal of Cosmology and Astroparticle Physics, 0701 (2007) 022 (at arXiv (http://ar xiv.org/abs/hep-th/0611043)) "Spooks in Space", Mason Inman, New Scientist, Volume 195, Issue 2617, 18 August 2007, Pages 26-29 (http://www.newscientist.com/channel/fundamentals/mg19526171.100-spooks-in -space.html) "Big Brain Theory: Have Cosmologists Lost Theirs?", Dennis Overbye, New York Times, 15 January 2008 (http://www.nytimes.com/2008/01/15/science/15brain.html?pagewanted=all) Retrieved from "https://en.wikipedia.org/w/index.php?title=Boltzmann_brain&oldid=742572649" Categories: Paradoxes Philosophy of thermal and statistical physics Physical cosmology Thought experiments in philosophy of mind This page was last modified on 4 October 2016, at 14:06. Text is available under the Creative Commons Attribution-ShareAlike License; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy. Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization..
Recommended publications
  • Vilenkin's Cosmic Vision a Review Essay of Emmany Worlds in One

    Vilenkin's Cosmic Vision a Review Essay of Emmany Worlds in One

    Vilenkin's Cosmic Vision A Review Essay of emMany Worlds in One The Search for Other Universesem, by Alex Vilenkin William Lane Craig Used by permission of Philosophia Christi 11 (2009): 231-8. SUMMARY Vilenkin's recent book is a wonderful popular introduction to contemporary cosmology. It contains provocative discussions of both the beginning of the universe and of the fine-tuning of the universe for intelligent life. Vilenkin is a prominent exponent of the multiverse hypothesis, which features in the book's title. His defense of this hypothesis depends in a crucial and interesting way on conflating time and space. His claim that his theory of the quantum creation of the universe explains the origin of the universe from nothing trades on a misunderstanding of "nothing." VILENKIN'S COSMIC VISION A REVIEW ESSAY OF EMMANY WORLDS IN ONE THE SEARCH FOR OTHER UNIVERSESEM, BY ALEX VILENKIN The task of scientific popularization is a difficult one. Too many authors think that it is to be accomplished by frequent resort to explanatorily vacuous and obfuscating metaphors which leave the reader puzzling over what exactly a particular theory asserts. One of the great merits of Alexander Vilenkin's book is that he shuns this route in favor of straightforward, simple explanations of key terms and ideas. Couple that with a writing style that is marvelously lucid, and you have one of the best popularizations of current physical cosmology available from one of its foremost practitioners. Vilenkin vigorously champions the idea that we live in a multiverse, that is to say, the causally connected universe is but one domain in a much vaster cosmos which comprises an infinite number of such domains.
  • States with Regards to Finding If the Cosmological Constant Is, Or Is Not a ‘Vacuum’ Field Andrew Beckwith, Beckwith@Aibep.Org

    States with Regards to Finding If the Cosmological Constant Is, Or Is Not a ‘Vacuum’ Field Andrew Beckwith, [email protected]

    Consequences of squeezing initially coherent (semi classical) states with regards to finding if the cosmological constant is, or is not a ‘vacuum’ field Andrew Beckwith, [email protected], Abstract The following document is to prepare an analysis on if the cosmological constant is a vacuum field. Candidates for how to analyze this issue come up in terms of brane theory, modified treatments of WdM theory (pseudo time component added) and/ or how to look at squeezing of vacuum states, as initially coherent semi classical constructions, or string theory versions of coherent states. The article presents a thought experiment if there is a non zero graviton mass, and at the end, in the conclusion states experimental modeling criteria which may indicate if a non zero graviton mass is measurable, which would indicate the existence, de facto of a possible replacement for DE, based upon non zero mass gravitons, and indications for a replacement for a cosmological constant. Introduction: Dr. Karim1 mailed the author with the following question which will be put in quotes: The challenge of resolving the following question: At the Big Bang the only form of energy released is in the form of geometry – gravity. intense gravity field lifts vacuum fields to positive energies, So an electromagnetic vacuum of density 10122 kg/m3 should collapse under its own gravity. But this does not happen - that is one reason why the cosmological constant cannot be the vacuum field. Why? Answering this question delves into what the initial state of the universe should be, in terms of either vacuum energy, or something else.
  • Exploring Cosmic Strings: Observable Effects and Cosmological Constraints

    Exploring Cosmic Strings: Observable Effects and Cosmological Constraints

    EXPLORING COSMIC STRINGS: OBSERVABLE EFFECTS AND COSMOLOGICAL CONSTRAINTS A dissertation submitted by Eray Sabancilar In partial fulfilment of the requirements for the degree of Doctor of Philosophy in Physics TUFTS UNIVERSITY May 2011 ADVISOR: Prof. Alexander Vilenkin To my parents Afife and Erdal, and to the memory of my grandmother Fadime ii Abstract Observation of cosmic (super)strings can serve as a useful hint to understand the fundamental theories of physics, such as grand unified theories (GUTs) and/or superstring theory. In this regard, I present new mechanisms to pro- duce particles from cosmic (super)strings, and discuss their cosmological and observational effects in this dissertation. The first chapter is devoted to a review of the standard cosmology, cosmic (super)strings and cosmic rays. The second chapter discusses the cosmological effects of moduli. Moduli are relatively light, weakly coupled scalar fields, predicted in supersymmetric particle theories including string theory. They can be emitted from cosmic (super)string loops in the early universe. Abundance of such moduli is con- strained by diffuse gamma ray background, dark matter, and primordial ele- ment abundances. These constraints put an upper bound on the string tension 28 as strong as Gµ . 10− for a wide range of modulus mass m. If the modulus coupling constant is stronger than gravitational strength, modulus radiation can be the dominant energy loss mechanism for the loops. Furthermore, mod- ulus lifetimes become shorter for stronger coupling. Hence, the constraints on string tension Gµ and modulus mass m are significantly relaxed for strongly coupled moduli predicted in superstring theory. Thermal production of these particles and their possible effects are also considered.
  • September Issue

    September Issue

    THE GLOBAL PRESS, ISSUE 1 OCT 4, 2013 JOHN MUIR K-12 MAGNET SCHOOL | BUILDING GLOBAL CITIZENS | FALL 2013 Sam Rempola - Editor-In-Chief Harry Pearce - Science & Technology Rahja Williams - Global Connections Pedro Quiroz & Tanya Reyes - Art Nicole Matthews - Food & Entertainment Mayra Jaramillo & Charday Drayton-White - Student Life Areli Ventura - Graphic Design Staff Writers: Genesis Felix, Rahel Garcia, Jose Juarez- Bardales, Riley Petka, Munah Togba Muir excited to announce class ambassadors by Mayra Jaramillo Annual peace march a success Being a class ambassador means by Jose Juarez students get the opportunity to On September 20th, John Muir held its annual peace walk, an event that brings together represent their classes and bring ideas students from all grades. As is the tradition, we were led by our own peace dove as we walked to the attention of ASB. Candidates were around the school holding signs and flags promoting peace. selected by their teachers based on maturity, academic standing, and leadership skills and then chosen by Muir welcomes new principal by Areli Ventura & Jael Villagomez their class. The ASB is looking forward appreciates the opportunity to have a direct to getting input from the more Muir students are happy to introduce our impact on students’ lives. Mrs. Bellofatto feels representatives of the student body, so new principal, Mrs. Laura Bellofatto. Mrs. being a principal is an amazing experience. the school supports all students. Bellofatto previously worked as a principal at Eleventh grade ambassador, Rahja When Mrs. Bellofatto is not at school, she Morse High and the Construction Tech likes to be outdoors.
  • The Anthropic Principle and Multiple Universe Hypotheses Oren Kreps

    The Anthropic Principle and Multiple Universe Hypotheses Oren Kreps

    The Anthropic Principle and Multiple Universe Hypotheses Oren Kreps Contents Abstract ........................................................................................................................................... 1 Introduction ..................................................................................................................................... 1 Section 1: The Fine-Tuning Argument and the Anthropic Principle .............................................. 3 The Improbability of a Life-Sustaining Universe ....................................................................... 3 Does God Explain Fine-Tuning? ................................................................................................ 4 The Anthropic Principle .............................................................................................................. 7 The Multiverse Premise ............................................................................................................ 10 Three Classes of Coincidence ................................................................................................... 13 Can The Existence of Sapient Life Justify the Multiverse? ...................................................... 16 How unlikely is fine-tuning? .................................................................................................... 17 Section 2: Multiverse Theories ..................................................................................................... 18 Many universes or all possible
  • Arxiv:Hep-Th/0209231 V1 26 Sep 2002 Tbs,Daai N Uigi Eurdfrsae Te Hntetemlvcu Olead to Vacuum Thermal the Anisotropy

    Arxiv:Hep-Th/0209231 V1 26 Sep 2002 Tbs,Daai N Uigi Eurdfrsae Te Hntetemlvcu Olead to Vacuum Thermal the Anisotropy

    SLAC-PUB-9533 BRX TH-505 October 2002 SU-ITP-02/02 Initial conditions for inflation Nemanja Kaloper1;2, Matthew Kleban1, Albion Lawrence1;3;4, Stephen Shenker1 and Leonard Susskind1 1Department of Physics, Stanford University, Stanford, CA 94305 2Department of Physics, University of California, Davis, CA 95616 3Brandeis University Physics Department, MS 057, POB 549110, Waltham, MA 02454y 4SLAC Theory Group, MS 81, 2575 Sand Hill Road, Menlo Park, CA 94025 Free scalar fields in de Sitter space have a one-parameter family of states invariant under the de Sitter group, including the standard thermal vacuum. We show that, except for the thermal vacuum, these states are unphysical when gravitational interactions are arXiv:hep-th/0209231 v1 26 Sep 2002 included. We apply these observations to the quantum state of the inflaton, and find that at best, dramatic fine tuning is required for states other than the thermal vacuum to lead to observable features in the CMBR anisotropy. y Present and permanent address. *Work supported in part by Department of Energy Contract DE-AC03-76SF00515. 1. Introduction In inflationary cosmology, cosmic microwave background (CMB) data place a tanta- lizing upper bound on the vacuum energy density during the inflationary epoch: 4 V M 4 1016 GeV : (1:1) ∼ GUT ∼ Here MGUT is the \unification scale" in supersymmetric grand unified models, as predicted by the running of the observed strong, weak and electromagnetic couplings above 1 T eV in the minimal supersymmetric standard model. If this upper bound is close to the truth, the vacuum energy can be measured directly with detectors sensitive to the polarization of the CMBR.
  • Avoiding Boltzmann Brain Domination in Holographic Dark Energy Models

    Avoiding Boltzmann Brain Domination in Holographic Dark Energy Models

    Physics Letters B 750 (2015) 181–183 Contents lists available at ScienceDirect Physics Letters B www.elsevier.com/locate/physletb Avoiding Boltzmann Brain domination in holographic dark energy models R. Horvat Rudjer Boškovi´c Institute, P.O.B. 180, 10002 Zagreb, Croatia a r t i c l e i n f o a b s t r a c t Article history: In a spatially infinite and eternal universe approaching ultimately a de Sitter (or quasi-de Sitter) Received 2 March 2015 regime, structure can form by thermal fluctuations as such a space is thermal. The models of Dark Received in revised form 10 August 2015 Energy invoking holographic principle fit naturally into such a category, and spontaneous formation of Accepted 2 September 2015 isolated brains in otherwise empty space seems the most perplexing, creating the paradox of Boltzmann Available online 7 September 2015 Brains (BB). It is thus appropriate to ask if such models can be made free from domination by Boltzmann Editor: M. Cveticˇ Brains. Here we consider only the simplest model, but adopt both the local and the global viewpoint in the description of the Universe. In the former case, we find that if a dimensionless model parameter c, which modulates the Dark Energy density, lies outside the exponentially narrow strip around the most natural c = 1line, the theory is rendered BB-safe. In the latter case, the bound on c is exponentially stronger, and seemingly at odds with those bounds on c obtained from various observational tests. © 2015 The Author. Published by Elsevier B.V.
  • Module 2—Evidence for God from Contemporary Science (Irish Final)

    Module 2—Evidence for God from Contemporary Science (Irish Final)

    Module 2—Evidence for God from Contemporary Science (Irish Final) Intro There is a long and strong relationship between the natural sciences and the Catholic Church. At least 286 priests and clergy were involved in the development of all branches of the natural sciences,1 and the Catholic Church hosts an Academy of Sciences with 46 Nobel Prize Winners as well as thousands of University and high school science departments, astronomical observatories and scientific institutes throughout the world (see Module III Section V). This should not be surprising, because as we saw in the previous Module most of the greatest scientific minds throughout history were believers (theists), and today, 51% of scientists are declared believers, as well as 88% of physicians. This gives rise to the question, “if scientists and physicians are evidence-based people, why are the majority of scientists and physicians believers?” What is their evidence? Many scientists, such as Albert Einstein and Eugene Wigner intuited clues of a divine intelligence from the wholly unexpected pervasive mathematical ordering of the universe.2 Today, the evidence for an intelligent transphysical creator is stronger than ever before despite the proliferation of many hypothetical new models of physical reality which at first seem to suggest the non-necessity of a creator. These new models include a multiverse, universes in the higher dimensional space of string theory, and multidimensional bouncing universes. So, what is this evidence that points to an intelligent creator even of multiverses, string universes, and multi- dimensional bouncing universes? There are 3 principal areas of evidence, each of which will be discussed in this Module: 1.
  • The Reason Series: What Science Says About God

    The Reason Series: What Science Says About God

    Teacher’s Resource Manual The Reason Series: What Science Says About God By Robert J. Spitzer, S.J., Ph.D. and Claude LeBlanc, M.A. Nihil Obstat: Reverend David Leigh, S.J., Ph.D. July 6, 2012 Imprimatur: Most Reverend Tod D. Brown Bishop of Orange, California July 11, 2012 Magis Center of Reason and Faith www.magiscenter.com USCCB Approval: The USCCB Subcommittee for Catechetical Conformity gives approval only for curricula, text book series, teacher’s manuals, or student workbooks that concern a whole course of studies. Partial curricula and programs may obtain ecclesiastical approval by imprimatur from the local Bishop. Since The Reason Series is such a partial curriculum its ecclesiastical approval by the USCCB is validated by the imprimatur. Cover art by Jim Breen Photos: Photos from the Hubble Telescope: courtesy NASA, PD-US Stephen Hawking (page 19): courtesy NASA, PD-US Galileo (page 20): PD-Art Arno Penzias (page 25): courtesy Kartik J, GNU Free Documentation License Aristotle (page 41): courtesy Eric Gaba, Creative Commons Albert Einstein (page 49): PD-Art Georges Lemaitre (page 49): PD-Art Alexander Vilenkin (page 51): courtesy Lumidek, Creative Commons Alan Guth (page 51): courtesy Betsy Devine, Creative Commons Roger Penrose (page 71): PD-Art Paul Davies (page 71): courtesy Arizona State University, PD-Art Sir Arthur Eddington (page 92): courtesy Library of Congress, PD-US Revision © 2016 Magis Institute (Garden Grove, California) All Rights Reserved No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the written permission of the author.
  • Time in Cosmology

    Time in Cosmology

    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Philsci-Archive Time in Cosmology Craig Callender∗ C. D. McCoyy 21 August 2017 Readers familiar with the workhorse of cosmology, the hot big bang model, may think that cosmology raises little of interest about time. As cosmological models are just relativistic spacetimes, time is under- stood just as it is in relativity theory, and all cosmology adds is a few bells and whistles such as inflation and the big bang and no more. The aim of this chapter is to show that this opinion is not completely right...and may well be dead wrong. In our survey, we show how the hot big bang model invites deep questions about the nature of time, how inflationary cosmology has led to interesting new perspectives on time, and how cosmological speculation continues to entertain dramatically different models of time altogether. Together these issues indicate that the philosopher interested in the nature of time would do well to know a little about modern cosmology. Different claims about time have long been at the heart of cosmology. Ancient creation myths disagree over whether time is finite or infinite, linear or circular. This speculation led to Kant complaining in his famous antinomies that metaphysical reasoning about the nature of time leads to a “euthanasia of reason”. But neither Kant’s worry nor cosmology becoming a modern science succeeded in ending the speculation. Einstein’s first model of the universe portrays a temporally infinite universe, where space is edgeless and its material contents unchanging.
  • Creation Ex Nihilo: Theology and Science William Lane Craig

    Creation Ex Nihilo: Theology and Science William Lane Craig

    Creation ex nihilo: Theology and Science William Lane Craig SUMMARY The biblical doctrine of temporal creation ex nihilo has received strong scientific confirmation from post-relativistic physics. Two lines of evidence point to an absolute beginning of the universe: the expansion of the universe and the thermodynamics of the universe. In each case attempts to maintain a past-eternal universe have become increasingly difficult to defend. Given the beginning of the universe, the question arises as to how the universe could have come into being. Attempts by some physicists to maintain that physics can explain the origin of the universe from nothing either trade on an equivocal use of the term “nothing” or else are guilty of philosophical faux pas. Supernatural creation ex nihilo is the better explanation. CREATION EX NIHILO: THEOLOGY AND SCIENCE Introduction “In the beginning God created the heavens and the earth” (Gen. 1.1). With majestic simplicity the author of the opening chapter of Genesis thus differentiated his viewpoint, not only from the ancient creation myths of Israel’s neighbors, but also effectively from pantheism, such as is found in religions like Vedanta Hinduism and Taoism, from panentheism, whether of classical neo- Platonist vintage or twentieth-century process theology, and from polytheism, ranging from ancient paganism to contemporary Mormonism. The biblical writers give us to understand that the universe had a temporal origin and thus imply creatio ex nihilo in the temporal sense that God brought the universe into being without a material cause at some point in the finite past. [1] Moreover, the Church Fathers, though heavily influenced by Greek thought, dug in their heels concerning the doctrine of creation, sturdily insisting on the temporal creation of the universe ex nihilo in opposition to the prevailing Hellenistic doctrine of the eternity of matter.
  • Why Is There Something, Rather Than Nothing?

    Why Is There Something, Rather Than Nothing?

    Why Is There Something, Rather Than Nothing?∗ Sean M. Carroll Walter Burke Institute for Theoretical Physics California Institute of Technology, Pasadena, CA 91125, U.S.A. [email protected] February 8, 2018 It seems natural to ask why the universe exists at all. Modern physics suggests that the universe can exist all by itself as a self-contained system, without any- thing external to create or sustain it. But there might not be an absolute answer to why it exists. I argue that any attempt to account for the existence of some- thing rather than nothing must ultimately bottom out in a set of brute facts; the universe simply is, without ultimate cause or explanation. Science and philosophy are concerned with asking how things are, and why they are the way they are. It therefore seems natural to take the next step and ask why things are at all – why the universe exists, or why there is something rather than nothing [1, 2]. Ancient philosophers didn’t focus too much on what Heidegger [3] called the “funda- mental question of metaphysics” and Gr¨unbaum [4] has dubbed the “Primordial Existential Question.” It was Leibniz, in the eighteenth century, who first explicitly asked “Why is there something rather than nothing?” in the context of discussing his Principle of Sufficient Rea- son (“nothing is without a ground or reason why it is”) [5]. By way of an answer, Leibniz arXiv:1802.02231v1 [physics.hist-ph] 6 Feb 2018 appealed to what has become a popular strategy: God is the reason the universe exists, but God’s existence is its own reason, since God exists necessarily.