Is the Universe Expanding?
Ever since Einstein’s theory of general relativity was applied to what is known about the universe as a whole, it has been suspected that the universe was expanding. When Edwin Hubble and Milton Humason discovered in the 1920s that practically all galaxies in the sky were moving away from us at great speeds, this boosted suspicions that the universe was expanding at a rapid rate. Yet it was not until 2000 that decisive evidence was finally found in favor of the universe’s expansion, in the form of extensive redshift surveys of very distant objects. The expanding universe is often cited as the most significant finding in modern cosmology. In Einstein’s time, the steady-state theory was the predominant one, which stated that the universe remained balanced at the same size. Einstein, whose equations predicted universal expansion or contraction but not stasis, artificially introduced a stabilizing variable into his equations, called the “cosmological constant.” After realizing from Hubble’
Measurements indicate that the universe is continually expanding, or spreading out. Current belief is that space itself is enlarging, carrying along the galaxies that are embedded within space. The most distant galaxies and quasars seems to have departing speeds that are close to the speed of light. The evidence is based on the redshift of light. If a light source such as a galaxy is moving away from the earth, there will be a shift toward the longer wavelength end of the spectrum, that is, in the direction of red-colored light. This shift is noticed for nearly all of the galaxies beyond those in the vicinity of the Milky Way. Such galaxies don’t actually turn red, but their spectra reveal the shift of their wavelength toward longer wavelengths. The redshift of starlight is often taken as evidence for the big bang theory. Yesterday the universe was a bit smaller than it is today, and it was smaller yet a year ago. By this backward extrapolation, the universe is hypothetically contracte
