Ever since Galileo pointed his crude telescope toward the heavens and observed the moons of Jupiter and postulated a heliocentric solar system of planets revolving about the sun; and ever since Newton connected the gravitational force that keeps the moon in orbit about the earth as the same force that keeps the planets in orbit about the sun, man has understood the difference between planets and stars. Before that time, all the lights in the night sky were stars, some were movable stars and some were fixed. The four brightest night sky lights other than the moon are the four major planets. Yet, they do not emit any light of their own; all their light is a reflection of the sun. Even the earth as seen from space is reflecting sunlight.
However, our sun, as well as all the other stars, are emitters of their own light which they generate. How is this light generated? In the old days, before the atomic age, man thought that there must be a big deposit of coal burning on the sun. No one could imagine what kind of fire could produce so much heat and light without running out of fuel. Now we know that every star is a nuclear furnace and that the energy is generated by a thermonuclear reaction involving both fission and fusion. Heavy elements in the core of the star are breaking apart and converting mass into energy according to Einstein's equivalence equation; and this energy causes a fusion reaction in the outer envelope in which two deuterium atoms are united into one helium atom producing the equivalent of a sustained H-bomb explosion. Since mass is continually being used up, some have wondered how long the sun will last. We have been assured that many thousands of years will expire before the sun will burn out. However, stars do expire over millions of years. We see stars that have exploded into novae, imploded into white dwarfs or neutron stars or even black holes, and expanded into red giants. At the present time, our sun is a medium sized, yellow star that seems fairly stable.
We are told in Isaiah that in the last days darkness will cover the earth and gross darkness the people, but that God's brightness will shine upon us and His glory will be seen upon us, and that the Gentiles will be attracted to that light (Isa. 60:1-3). In these days of moral darkness we are to reflect the rays of light from the Sun of righteousness and our sons and daughters and all people will see the light and become radiant, and their hearts will swell with joy (Isa. 60:4,5). When the saints are gathered on the other shore, not only will there be stars in their crowns, but those that have led many to righteousness will shine like the stars forever and ever (Dan. 12:30); their fire will never go out; they will have been changed from "reflectors to emitters."
