The Big Bang Never Happened

THE C0SM0L0GICAL DEBATE■Big Bang theory. On the other, it gave astronomers a powerfultool—by measuring the light from a galaxy one could calculateits distance from earth.MEASURING THE DISTANCE TO A GALAXYAs an object travels farther away, its light shifts to the redend of the spectrum, just as a train whistle's pitch drops as itpasses. Light waves (or sound waves) on the receding side ofthe object are more spread out than on the approaching side.A longer wavelength means a shift to the red (Fig. 1.3a). Theredshift can be used to measure an object's velocity.When light from a distant galaxy is put through a prism orgrating, it produces a spectrum with characteristic dark lines.Comparing the frequency or color of the dark lines with thoseproduced by heated gases on earth, astronomers in the twentiesfound that the galaxy lines shifted to the red, implyingthat the galaxies are receding at high velocity (Fig. 1.3b).Astronomer Edward Hubble found that the dimmer a galaxyis, and thus presumably the more distant it is, the higher theredshift velocity (Fig. 1.3c). Astronomers can use redshifts tomeasure distance far beyond the limits of other methods.In the seventies, Brent Tully and J. R. Fischer developedanother method of determining distance. They found thatthe intrinsic brightness of a galaxy was proportional to thefourth power of the rotational velocity (Fig. 1.3d). Becausethe rotational velocity could be measured from earth by comparingthe redshifts on each side of a galaxy, the intrinsicbrightness can be calculated. Knowing how bright the galaxyappeared in the sky would then give its distance.18