Physics for Scientists and Engineers with Modern Physics
10th Edition
ISBN: 9781337553292
Author: Raymond A. Serway, John W. Jewett
Publisher: Cengage Learning
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Chapter 44, Problem 33P
(a)
To determine
The value of Planck length.
(b)
To determine
The value of Planck time.
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Classical general relativity views the structure of spacetime as deterministic and well defined down to arbitrarily small distances. On the other hand, quantum general relativity forbids distances smaller than the Planck length given by L = (hG/c3)1/2. (a) Calculate the value of the Planck length. The quantum limitation suggests that after the Big Bang, when all the presently observable section of the Universe was contained within a point-like singularity, nothing could be observed until that singularity grew larger than the Planck length. Because the size of the singularity grew at the speed of light, we can infer that no observations were possible during the time interval required for light to travel the Planck length. (b) Calculate this time interval, known as the Planck time T, and state how it compares with the ultrahot epoch mentioned in the text.
The photons that make up the cosmic microwave background were emitted about 380,000 years after the Big Bang. Today, 13.8billion years after the Big Bang, the wavelengths of these photons have been stretched by a factor of about 1100 since they were emitted because lengths in the expanding universe have increased by that same factor of about 1100.
Consider a cubical region of empty space in today’s universe 1.00 m on a side, with a volume of 1.00 m3. What was the length s0 of each side and the volume V0 of this same cubical region 380,000 years after the Big Bang?
s0 = ? m
V0 = ? m^3
Today the average density of ordinary matter in the universe is about 2.4×10−27 kg/m3. What was the average density ?(rho)0 of ordinary matter at the time that the photons in the cosmic microwave background radiation were emitted?
(rho)0 = ? kg/m^3
The time before which we don’t know what happened in the universe (10-43 s) is called the Planck time. The theory needed is a quantum theory of gravity and concerns the three fundamental constants h, G, and c. (a) Use dimensional analysis to determine the exponents m, n, l if the Planck time tP = hmGncl . (b) Calculate the Planck time using the expression you found in (a).
Chapter 44 Solutions
Physics for Scientists and Engineers with Modern Physics
Ch. 44.2 - Prob. 44.1QQCh. 44.5 - Prob. 44.3QQCh. 44.5 - Prob. 44.4QQCh. 44.8 - Prob. 44.5QQCh. 44.8 - Prob. 44.6QQCh. 44 - Prob. 1PCh. 44 - Prob. 2PCh. 44 - Prob. 3PCh. 44 - Prob. 4PCh. 44 - Prob. 5P
Ch. 44 - Prob. 6PCh. 44 - Prob. 7PCh. 44 - Prob. 8PCh. 44 - Prob. 9PCh. 44 - Prob. 10PCh. 44 - Prob. 11PCh. 44 - Prob. 12PCh. 44 - Prob. 13PCh. 44 - Prob. 14PCh. 44 - Prob. 15PCh. 44 - Prob. 16PCh. 44 - Prob. 17PCh. 44 - Prob. 18PCh. 44 - Prob. 20PCh. 44 - Prob. 21PCh. 44 - Prob. 22PCh. 44 - Prob. 23PCh. 44 - Prob. 24PCh. 44 - Prob. 25PCh. 44 - Prob. 26PCh. 44 - Prob. 27PCh. 44 - Prob. 29PCh. 44 - Prob. 30PCh. 44 - The various spectral lines observed in the light...Ch. 44 - Prob. 33PCh. 44 - Prob. 34APCh. 44 - Prob. 35APCh. 44 - Prob. 36APCh. 44 - Prob. 37APCh. 44 - Prob. 38APCh. 44 - Prob. 39APCh. 44 - Prob. 40APCh. 44 - An unstable particle, initially at rest, decays...Ch. 44 - Prob. 42APCh. 44 - Prob. 43APCh. 44 - Prob. 44APCh. 44 - Prob. 45APCh. 44 - Prob. 46CPCh. 44 - Prob. 47CPCh. 44 - Prob. 48CPCh. 44 - Prob. 49CP
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