83. For isotropic materials, the coefficient of linear expansion α is related to that for volume expansion by

α =

1
3

β (Eq. 19-11). The radius of Earth may be found in the Appendix. With these assumptions, the

radius of the Earth should have increased by approximately

∆R

E

=

R

E

α∆T

=

6.4

× 10

3

km

 1

3



3.0

× 10

−5

/ K



(3000 K

− 300 K)

=

1.7

× 10

3

km .