
Concept explainers
Lord Kelvin and the Age of Earth
Figure 4.25 (a) William Thomson (Lord Kelvin). 1824-1907, was a British physicist and electrical engineer. (b) Kelvin used the heat diffusion equation to estimate the age of Earth (credit: modification of work by NASA).
During the late 1800s, the scientists of the new field of geology were coming to the conclusion the Earth must be “millions and millions” of years old. At about the same time. Charles Darwin had published his treatise on evolution.
Darwin’s view was that evolution needed many millions of years to take place, and he made a bold claim that the Weald chalk fields, where important fossils were found, were the result of 300 million years of erosion.
At that time, eminent physicist William Thomson (lord Kelvin) used an important partial differential equation, known as the heat diffusion equation, to estimate the age of Earth by determining how long it would take Earth to cool from molten rock to what we had at tha time. His conclusion was a range of 20 to 4(X) million years, but most likely about 5() million years. For many decades, the proclamations of this irrefutable icon of science did not sit well with geologists or with Darwin.
tJR ead Kelvin’s paper (http:Iiwww.openstaxcollege.orgIlI2O KelEarthAge) on estimating the age of the Earth.
Kelvin made reasonable assumptions based on what was known in his time, but he also made several assumptions that turned out to be wrong. One incorrect assumption was that Earth is solid and that the cooling was therefore via conduction only, hence justifying the use of the diffusion equation. But the most serious error was a forgivable one—omission of the fact that Earth contains radioactive elements that continually supply heat beneath Earth’s mantle. The discoveiy of radioactivity came near the end of Kelvin’s life and he acknowledged that his calculation would have to be modified.
Kelvin used the simple one-dimensional model applied only to Earth’s outer shell, and derived the age from gsaphs and the roughly known temperature gs-adietn near Earth’s surface. Let’s take a look at a more appropriate version of the diffusion equation in radial coordinates, which has the form
(4.23)
Here, T(r.t) is temperature as a function of r (measured from the center of Earth) and time i. K is the heat conductivity—for molten rock, in this case. ibe standard method of solving such a partial differential equation is by separation of variables, where we express the solution as the product of functions containing each variable separately. In this case, we would write the temperature as

Want to see the full answer?
Check out a sample textbook solution
Chapter 4 Solutions
Calculus Volume 3
Additional Math Textbook Solutions
Calculus: Early Transcendentals (2nd Edition)
A Problem Solving Approach To Mathematics For Elementary School Teachers (13th Edition)
Elementary Statistics: Picturing the World (7th Edition)
Basic Business Statistics, Student Value Edition
University Calculus: Early Transcendentals (4th Edition)
Elementary Statistics (13th Edition)
- R₂ = X2 2) slots per pole per phase = 3/31 B-18060 msl kd Kasi Sin (1) I sin (6) sin(30) Sin (30) اذا ميريد شرح الكتب بس 0 بالفراغ 3) Cos (30) 0.866 4) Rotating 5) Synchronous speed s = 1000-950 1000 Copper losses: 5kw Rotor input 5 0.05 6) 1 120 x 50 G loo kw ined sove in peaper I need a detailed solution on paper please Q3// x²y// +xy/ + (x² - ½) y = x³/². اذا ميريد شرح الكتب فقط look 7) rotor DC Q4// x²y// - (2x+x²)y/ + (2 + x)y = x³. dy 2x+2y+4 = dx 2x-y-3arrow_forward۳/۱ R2X2 2) slots per pole per phase = 3/31 B, 18060 msl Kas Sin() 1sin() sin(30) Sin (30) kd اذا ميريد شرح الكتب بس 0 بالفراغ 3) Cos (30) 0.866 4) Rotating 5) Synchronous speeds S = 1000-950 1000 Copper bosses 5kw 120*50 loca G Rotor input 5 loo kw 6) 1 0.05 اذا ميريد شرح الكتب فقط lookw 7) rotor DC ined sove in peaper I need a detailed solution on paper please 064 Q1// Find the solution of QI/Find the solution of Inxy= 7357 x+2y³ y' = xy3arrow_forwardR₂ = X2 2) slots per pole per phase 3/31 msl 180 60 Kd Ka Sin (1) Isin (6) sin(30) Sin (30) اذا ميريد شرح الكتب بس 0 بالفراغ 3) Cos (30) 0.866 4) Rotating 5) Synchronous speed, 120*50 1000 6 S = 1000-950 1000 Copper bosses: 5kw Rotor input 5 0.05 : loo kw 6) 1 اذا ميريد شرح الكتب فقط 100 7) rotor DC ined sove in peaper I need a detailed solution on paper please Find the general solution of the following equations: Q2lyl-4y+13y=esinx. Find the general solution of the following equations: " Qly (49) - 16y= 0. 151arrow_forward
- ۳/۱ R₂ = X2 2) slots per pole per phase = 3/31 B-18060 msl kd Kasi Sin (1) I sin (6) sin(30) Sin (30) اذا ميريد شرح الكتب بس 0 بالفراغ 3) Cos (30) 0.866 4) Rotating 5) Synchronous speed s = 1000-950 1000 Copper losses: 5kw Rotor input 5 0.05 6) 1 120 x 50 G loo kw اذا میرید شرح الكتب فقط look 7) rotor DC ined sove in peaper I need a detailed solution on paper dy please 04 12=-cosx.y + 2cosx with y(x) = 1 か 'Oy + xlny + xe")dx + (xsiny + xlnx +*dy=0. 01arrow_forward٣/١ R2X2 2) slots per pole per phase = 3/31 B, 18060 msl kd Kas Sin (1) 1sin() sin(30) Sin (30) اذا ميريد شرح الكتب بس 0 بالفراغ 3) Cos (30) 0.866 4) Rotating 5) Synchronous speeds S = 1000-950 1000 Copper bosses 5kw 120*50 loca G Rotor input 5 loo kw 0.05 6) 1 اذا ميريد شرح الكتب فقط lookw 7) rotor ined sove in peaper I need a detailed solution on paper please DC 口 04 on its wheels as shown in figure. The the door is 8 m below the free surface o is located at the center of the d no water leaks an accident and lands at the bottom of the lake 12m high and I m wide, and the top edge of water Determine the hydrostatic force on the discuss if the driver can open the door, if ong person can lift 100 kg, the passenger The door can be approximated as a vertical rec | 279|-|(23+2+12+20=2) AA Find the general solution of the following equations: 11 - 1/4+xy/-(1-x²³)= 0. 2arrow_forward۳/۱ : +0 العنوان I need a detailed drawing with explanation R₂ = X2 2) slots per pole per phase 3/31 Le msl 180 60 Kd Ka Sin (1) Isin (6) sin(30) Sin (30) اذا ميريد شرح الكتب بس 0 بالفراغ 3) Cos (30) 0.866 4) Rotating 5) Synchronous speed, 120*50 1000 6 S = 1000-950 1000 Copper bosses: 5kw Rotor input 5 loo kw 0.05 6) 1 اذا ميريد شرح الكتب فقط ١٥٠ 7) rotov DC ined sove in peaper I need a detailed solution on paper please 064 Q1// Find the solution of: ( texty Q1// Find the solution of: '' y' -2y= 22% √y³arrow_forward
- R2X2 2) slots per pole per phase = 3/31 B-180-60 msl kd Ka, Sin (1) I sin (6) sin(30) Sin (30) اذا ميريد شرح الكتب بس 0 بالفراغ 3) Cos (30) 0.866 4) Rotating 5) Synchronous speed s = 1000-950 1000 Copper losses 5kw 120 50 G Rotor input 5 loo kw 6) 1 ۳/۱ 0.05 إذا ميريد شرح الكتب فقط look 7) rotov DC ined sove in peaper I need a detailed solution on paper please Find the general solution of the following equations: " yll + 4y = tan2x. Find the general solution of the following equations: 01-24+7=0 T el [A] G ха =T Marrow_forwardR₂ = X2 2) slots per pole per phase = 3/31 B-18060 msl kd Kasi Sin (1) I sin (6) sin(30) Sin (30) اذا ميريد شرح الكتب بس 0 بالفراغ 3) Cos (30) 0.866 4) Rotating 5) Synchronous speed s = 1000-950 1000 Copper losses: 5kw Rotor input 5 0.05 6) 1 120 x 50 G loo kw اذا میرید شرح الكتب فقط look 7) rotor DC ined sove in peaper I need a detailed solution on paper please 0 64 Solve the following equations: = dx x²+y2 with y(0) = 1. 7357 Solve the following equations: dy x³+3xy² Q1// = dx 3x²y+y³° 01arrow_forward٣/١ R2X2 2) slots per pole per phase = 3/3 1 B18060 msl Kd 3 Kol Sin (1) 1sin() sin(30) Sin (30) اذا میرید شرح الكتب بس 0 بالفراغ 3) cos (30) 0.866 4) Rotating 5) Synchronous speeds 120*50 G looo 1000-950 1000 50:05 Copper losses: 5kw Rotor input 5 loo kw 0.05 6) 1 اذا ميريد شرح الكتب فقط look 7) rotor DC ined sove in peaper I need a detailed solution on paper please 0 64 (Find the solution of the initial-valued problems: xy' + 2y = x³e* ;y(1) = 0 Q1// Find the solution of: (1) y' + ytqpx = see²x y³arrow_forward
- A fluid has density 800 kg/m³ and flows with velocity v = xi + yj + zk, where x, y, and z are measured in meters, and the components of u are measured in meters per second. Find the rate of flow outward through the part of the paraboloid z = 64 - x² - y² that lies above the xy plane.arrow_forward۳/۱ : +0 العنوان I need a detailed drawing with explanation R₂ = X2 2) slots per pole per phase 3/31 Le msl 180 60 Kd Ka Sin (1) Isin (6) sin(30) Sin (30) اذا ميريد شرح الكتب بس 0 بالفراغ 3) Cos (30) 0.866 4) Rotating 5) Synchronous speed, 120 x 50 S = 1000-950 1000 Copper bosses: 5kw Rotor input 5 6 : loo kw 6) 1 0.05 اذا ميريد شرح الكتب فقط 100 7) rotor DC 1000 ined sove in peaper I need a detailed solution on paper please // Find the solution of: |(2xy³ + 4x)y' = x²y² + y² 351 // Find the solution of: (1) 2xyy' = 1+ y² 01 175 T Τ Marrow_forwardFind the flux of the vector field F = (y,−x, 2²) through the helicoid with parameterization r(u, v) = (u cos v, u sin v, v) 0 ≤ u≤ 3, 0 ≤v≤ oriented away from the origin.arrow_forward
- Algebra & Trigonometry with Analytic GeometryAlgebraISBN:9781133382119Author:SwokowskiPublisher:CengageLinear Algebra: A Modern IntroductionAlgebraISBN:9781285463247Author:David PoolePublisher:Cengage LearningTrigonometry (MindTap Course List)TrigonometryISBN:9781337278461Author:Ron LarsonPublisher:Cengage Learning

