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Title: The Atom of the Universe: The Life and Work of Georges Lemaître


No abstract prepared.

Publication Date:
OSTI Identifier:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics Today; Journal Volume: 69; Journal Issue: 7; Other Information: (c) 2016 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States

Citation Formats

NONE. The Atom of the Universe: The Life and Work of Georges Lemaître. United States: N. p., 2016. Web. doi:10.1063/PT.3.3238.
NONE. The Atom of the Universe: The Life and Work of Georges Lemaître. United States. doi:10.1063/PT.3.3238.
NONE. 2016. "The Atom of the Universe: The Life and Work of Georges Lemaître". United States. doi:10.1063/PT.3.3238.
title = {The Atom of the Universe: The Life and Work of Georges Lemaître},
author = {NONE},
abstractNote = {No abstract prepared.},
doi = {10.1063/PT.3.3238},
journal = {Physics Today},
number = 7,
volume = 69,
place = {United States},
year = 2016,
month = 7
  • Current evidence suggests that the cosmological constant is not zero, or that we live in an open universe. We examine the implications for the future under these assumptions, and find that they are striking. If the universe is cosmological constant-dominated, our ability to probe the evolution of large-scale structure will decrease with time; presently observable distant sources will disappear on a timescale comparable to the period of stellar burning. Moreover, while the universe might expand forever, the integrated conscious lifetime of any civilization will be finite, although it can be astronomically long. We argue that this latter result is farmore » more general. In the absence of possible exotic and uncertain strong gravitational effects, the total information recoverable by any civilization over the entire history of our universe is finite. Assuming that consciousness has a physical computational basis, and therefore is ultimately governed by quantum mechanics, life cannot be eternal. (c) 2000 The American Astronomical Society.« less
  • Cited by 1
  • We, first, analytically work out the long-term, i.e. averaged over one orbital revolution, perturbations on the orbit of a test particle moving in a local Fermi frame induced therein by the cosmological tidal effects of the inhomogeneous Lemaître-Tolman-Bondi (LTB) model. The LTB solution has recently attracted attention, among other things, as a possible explanation of the observed cosmic acceleration without resorting to dark energy. Then, we phenomenologically constrain both the parameters K1 doteq ddot frakR / frakR and K2 doteq ddot frakR' / frakR' of the LTB metric in the Fermi frame by using different kinds of solar system data.more » The corrections Δdot varpi to the standard Newtonian/Einsteinian precessions of the perihelia of the inner planets recently estimated with the EPM ephemerides, compared to our predictions for them, yield preliminarily K{sub 1} = (4±8) × 10{sup −26} s{sup −2}, K{sub 2} = (3±7) × 10{sup −23} s{sup −2}. The residuals of the Cassini-based Earth-Saturn range, compared with the numerically integrated LTB range signature, allow to preliminarily obtain K{sub 1} ≈ K{sub 2} ≈ 10{sup −27} s{sup −2}. Actually, the LTB effects should be explicitly modeled in the ephemerides softwares, so that the entire planetary and spacecraft data sets should be accordingly re-processed. The LTB-induced distortions of the orbit of a typical object of the Oort cloud with respect to the commonly accepted Newtonian picture, based on the observations of the comet showers from that remote region of the solar system, point towards K{sub 1} ≈ K{sub 2}∼<10{sup −30}−10{sup −32} s{sup −2}. Such figures have to be compared with those inferred from cosmological data which are of the order of K{sub 1} ≈ K{sub 2} = −4 × 10{sup −36} s{sup −2}.« less
  • We study the validity of the Newtonian description of cosmological perturbations using the Lemaître model, an exact spherically symmetric solution of Einstein's equation. This problem has been investigated in the past for the case of a dust fluid. Here, we extend the previous analysis to the more general case of a fluid with non-negligible pressure, and, for the numerical examples, we consider the case of radiation (P=ρ/3). We find that, even when the density contrast has a nonlinear amplitude, the Newtonian description of the cosmological perturbations using the gravitational potential ψ and the curvature potential φ is valid as longmore » as we consider sub-horizon inhomogeneities. However, the relation ψ+φ=O(φ{sup 2})—which holds for the case of a dust fluid—is not valid for a relativistic fluid, and an effective anisotropic stress is generated. This demonstrates the usefulness of the Lemaître model which allows us to study in an exact nonlinear fashion the onset of anisotropic stress in fluids with non-negligible pressure. We show that this happens when the characteristic scale of the inhomogeneity is smaller than the sound horizon and that the deviation is caused by the nonlinear effect of the fluid's fast motion. We also find that ψ+φ= [O(φ{sup 2}),O(c{sub s}{sup 2φ} δ)] for an inhomogeneity with density contrast δ whose characteristic scale is smaller than the sound horizon, unless w is close to −1, where w and c{sub s} are the equation of state parameter and the sound speed of the fluid, respectively. On the other hand, we expect ψ+φ=O(φ{sup 2}) to hold for an inhomogeneity whose characteristic scale is larger than the sound horizon, unless the amplitude of the inhomogeneity is large and w is close to −1.« less