If the Sun is Losing 5 Feet of Diameter Every Hour, Wouldn't It Have Been Too Large Billions of Years Ago?
This argument comes from a paper published in 1979 by astronomer John Eddy. After studying observations from 1836 through the 20th century, he found the sun had contracted 2 arc seconds. He had found proof of what atronomers had suspected and know for a fact today: that the sun's diameter oscillates in an 80 year cycle. It does not constantly shrink.
Within the sun, and every star, there are 2 opposing forces: the intense gravity of the star, trying to crush it, and the intense heat of nuclear fusion, trying to blow it apart. As the gravitational field causes the surface to shrink ever so slightly, it builds incredible pressure inside the star, which speeds up the fusion reactions (think of a pressure cooker). The increased fusion then pushes the surface back out again, and the cycle starts over. Because the sun is truly gigantic, about 1 million times the size of Earth, this cycle plays out on what we would consider a slow scale: every 80 years.
[ References: The Legend of the Shrinking Sun (Till) ]