Time Since the Beginning While there is no consensus about the history of time since the beginning, in this paper I will discuss some possibilities. We have a pretty clear picture of cosmic history from the electroweak phase transition through the time of recombination, a period which includes the QCD phase transition and big bang nucleosynthesis. This paper includes a quantitative discussion of the age of the universe, of the radiation-matter transition, and of hydrogen recombination. There is much evidence that at earlier times the universe underwent inflation, but the details of how and when inflation happened are still far from certain. There is even more uncertainty about what happened before inflation, and how inflation began. I will describe the possibility of ``eternal'' inflation, which proposes that our universe evolved from an infinite tree of inflationary spacetime. Most likely, however, inflation can be eternal only into the future, but still must have a beginning. Published as: Astrophysical Ages and Time Scales," Astronomical Society of the Pacific Conference Series, vol. 245, pp. 3-17 (2001) arXiv categories: astro-ph

the Past TT Cosmic Time 78 The Beginning of Time 80 Measuring Time 83 The Nature of Time--A Virtual Reality … Chapter 1--Introduction--Meaning and Philosophy 1 Description of Parts 1 Meaning and Philosophy 3 Chapter … Reality? 85 The Arrows of Time 90 Einstein, Death, and the Illusion of Time 99 Consciousness, Death and

# Cosmic inflation and the arrow of time Cambridge University Press eBooks. Published: 2004-04-22. Preprint. 45 citations. ## Authors - Andreas Albrecht (University of California System): h-index 43; 12,588 citations; corresponding author ## Topics - Advanced Thermodynamics and Statistical Mechanics - Cosmology and Gravitation Theories --- # Cosmic Inflation and the Arrow of Time 1 ## Abstract Cosmic inflation claims to make the initial conditions of the standard big bang "generic". But Boltzmann taught us that the thermodynamic arrow of time arises from very non-generic ("low entropy") initial conditions. I discuss how to reconcile these perspectives. The resulting insights give an interesting way to understand inflation and also compare inflation with other ideas that claim to offer alternative theories of initial conditions. 1 Introduction..... ## Introduction One of the most obvious and compelling aspects of the physical world is that it has an "arrow of time". Certain processes (such as breaking a glass or burning fuel) appear all the time in our everyday experience, but the time reverse of these processes are never seen. In the modern understanding, special non-gen

# Physical time for the beginning universe arXiv (Cornell University). Published: 2024-08-02. Preprint. 0 citations. ## Authors - C. Wetterich: h-index 73; 22,900 citations; corresponding author ## Topics - Cosmology and Gravitation Theories - Earth Systems and Cosmic Evolution - Relativity and Gravitational Theory --- # Physical time for the beginning universe ## Abstract We propose that physical time is based on counting the oscillations of wave functions. The discrete counting of the ticks of these clocks does not depend on the metric frame. It remains well defined for the beginning epochs of the universe. The photon clock counts the oscillations of electromagnetic plane waves in the cosmic reference frame. It can be gauged with clocks for other massless or massive particles. These equivalent clocks form a clock system which defines a common universal continuous physical time. For the photon clock this physical time coincides with conformal time. The universe is eternal towards the past for typical models of inflationary cosmology -the photon clock ticks an infinite number of times. We compare the photon clock system to geodesic physical time, which is a frame invariant

# Inflation and the Meaning of Time Tags: spacetime, time, big-bang, cosmological-inflation - Score: 19 - Views: 1887 - Answers: 2 - Answered: yes - Asked by: Jim (403 rep) - Asked: 2014-03-26 - Site: physics ## Question I'm not quite sure how to ask this so that it can be answered in layman's terms, but I have lately seen, in several places, that with cosmological inflation, there was a point where the universe expanded faster than the speed of light. In this explanation, the following is stated: Gravity itself would have split off at the Planck time, 1e-43 of a second The strong nuclear force by about 1e-35 of a second Within about 1e-32 of a second, the scalar fields would have done their work, doubling the size of the Universe at least once every 1e-34 of a second (some versions of inflation suggest even more rapid expansion than this). It goes on to say that this rapid expansion is enough to take a quantum fluctuation 1e-20 times smaller than a proton and inflate it to a sphere about 10 cm across in about 15 x 1e-33 seconds. The conclusion is that this expansion occurred at faster than light speed. My main question is about the role of time in all of this, and I'm on