Physics for Scientists and Engineers with Modern Physics
10th Edition
ISBN: 9781337671729
Author: SERWAY
Publisher: Cengage
expand_more
expand_more
format_list_bulleted
Concept explainers
Question
Chapter 44, Problem 33P
(a)
To determine
The value of Planck length.
(b)
To determine
The value of Planck time.
Expert Solution & Answer
Want to see the full answer?
Check out a sample textbook solutionStudents have asked these similar questions
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
Knowledge Booster
Learn more about
Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, physics and related others by exploring similar questions and additional content below.Similar questions
- The geometry of spacetime in the Universe on large scales is determined by the mean energy density of the matter in the Universe, ρ. The critical density of the Universe is denoted by ρ0 and can be used to define the parameter Ω0 = ρ/ρ0. Describe the geometry of space when: (i) Ω0 < 1; (ii) Ω0 = 1; (iii) Ω0 > 1. Explain how measurements of the angular sizes of the hot- and cold-spots in the CMB projected on the sky can inform us about the geometry of spacetime in our Universe. What do measurements of these angular sizes by the WMAP and PLANCK satellites tell us about the value of Ω0?arrow_forwardConsider a cosmological spacetime in which the line element is given by ds? = a²(t)(-dt + dr² + dy² + dz²), where a(t) > 0 is the scale factor. Two light rays tangent to l = (1,1,0, 0) and l = (1,0, 1,0) are received at time t = u" = (a-'(to), 0, 0, 0). Compute the observed angle between the correspond- ing images. to by someone with 4-velocityarrow_forwardConsider a cosmological spacetime in which the line element is given by ds? = a°(t)(-dt + da² + dy° + dz?), where a(t) > 0 is the scale factor. Two light rays tangent to l4 = (1, 1, 0,0) and = (1,0, 1,0) are received at time t = to by someone with 4-velocity u" = (a-'(to), 0, 0, 0). Compute the observed angle between the correspond- ing images.arrow_forward
- Name: Hubble Distances Redshift z parameter The relativistic redshift is parametrized by z and given by Δ In terms of the scale factor, 2= X do - de de 1+z= ao a (2) Problem 01. Find the redshift z for a Hydrogen spectral line originally at 656 nm which has been observed at a wavelength of 1.64 μm. Astro 001 Fall 2022 Problem 02. How much smaller was the universe when this light was emitted? U₁ = DHO Using the redshift to measure the velocity, we find D~ (1) 0.1 Hubble's Law Hubble's Law states that the recession velocity of a redshifted galaxy is given by the product of the distance and the Hubble constant. (3) ZC Ho where c = 3 x 108 m/s and Ho = 2.3 x 10-18 s in standard units. The standard measurement of the Hubble constant is Ho = 71 (km/s)/Mpc. Problem 03. What is the distance in Mpc and ly to the galaxy measured in problem 01? 1 pc = 3.26 ly.arrow_forwardConsider the energy-momentum tensorT_µν = (ρ + p) u_µ u_ν + p g_µνapplied to the matter/energy distribution in the universe on large scales, and assume an equation of state of the form p = wρ, with w a constant. Determine the type of matter/energy dominating the universe if the energy-momentum tensor is traceless, that is, T^µ_µ = 0.arrow_forwardAlbert Einstein’s theory of relativity, which he developed in the context of his special theory of relativity, are inconsistent with several experiments. This is not the case with the general theory of relativity, whose predictions coincide with the experiments without contradiction and whose experimental confirmations were celebrated as great scientific achievements. The latter made the physicists obviously blind to the contradictions of the foundations of the theory of relativity and led to an immunization against critical statements on the theory of relativity. Explain this in simpler terms.arrow_forward
- Consider the energy-momentum tensor Tμv = (p+p) uu+P9μ applied to the matter/energy distribution in the universe on large scales, and assume an equation of state of the form p = wp, with w a constant. Determine the type of matter/energy dominating the universe if the energy-momentum tensor is traceless, that is, T"μ = 0.arrow_forwardThe bright radio galaxy, 3c84, is observed to be moving away from the Earth at such high speed that the emitted blue 434-nm Hγ line of hydrogen is Doppler-shifted to 442 nm. Edwin Hubble discovered that all objects outside the local group of galaxies are moving away from us, with speeds v proportional to their distances R. Hubble's law is expressed as v = HR, where the Hubble constant has the approximate value H ≈ 22 ✕ 10−3 m/(s · ly). Determine the distance from the Earth to this galaxy. _________ lyarrow_forwardUse Wien’s law to answer the following questions: (a) The cosmic background radiation peaks in intensity at a wavelength of 1.1 mm. To what temperature does this correspond? (b) About 379 000 y after the big bang, the universe became transparent to electromagnetic radiation. Its temperature then was 2970 K.What was the wavelength at which the background radiation was then most intense?arrow_forward
- (a) Let L be the diameter of our galaxy.Suppose that a person in a spaceship of massm wants to travel across the galaxy at constantspeed, taking proper time τ. Find the kineticenergy of the spaceship. (b) Your friend is impa-tient, and wants to make the voyage in an hour.For L = 105 light years, estimate the energy inunits of megatons of TNT (1 megaton=4×109 J).arrow_forwardThe peak intensity of the CMBR occurs at a wavelength of 1.1 mm. (a) What is the energy in eV of a 1.1-mm photon? (b) There are approximately 109 photons for each massive particle in deep space. Calculate the energy of 109 such photons. (c) If the average massive particle in space has a mass half that of a proton, what energy would be created by converting its mass to energy? (d) Does this imply that space is “matter dominated”? Explain briefly.arrow_forwardEstimate the age of the universe (in Gyrs) at the time when radiation was emitted from an object with redshift z. For 1 < z < 3200, you can assume the Universe is matter dominated, in which case a ∝ t^2/3 and equation 5.102 should hold. Values: Assume H0 = 70 km/s/Mpc Ωm,0 = 0.3 z=3.6 Equation 5.102 is : a(t) = (3/2 (sqrtΩm,0 ) H0 t)^2/3arrow_forward
arrow_back_ios
SEE MORE QUESTIONS
arrow_forward_ios
Recommended textbooks for you
- Physics for Scientists and Engineers with Modern ...PhysicsISBN:9781337553292Author:Raymond A. Serway, John W. JewettPublisher:Cengage LearningModern PhysicsPhysicsISBN:9781111794378Author:Raymond A. Serway, Clement J. Moses, Curt A. MoyerPublisher:Cengage Learning
Physics for Scientists and Engineers with Modern ...
Physics
ISBN:9781337553292
Author:Raymond A. Serway, John W. Jewett
Publisher:Cengage Learning
Modern Physics
Physics
ISBN:9781111794378
Author:Raymond A. Serway, Clement J. Moses, Curt A. Moyer
Publisher:Cengage Learning