Red Shift

Red Shift

The astronomer Halton Arp has found enigmatic and disturbing cases where a galaxy and a quasar, or a pair of galaxies, that are in apparent physical association have very different red shifts.

Occasionally there seems to be a bridge of gas and dust and stars connecting them. If the red shift is due to the expansion of the universe, very different red shifts imply very different distances But two galaxies that are physically connected can hardly also be greatly separated from each other – in some cases by a billion light years. Skeptics say that the association is purely statistical: that, for example, a nearby bright galaxy and a much more distant quasar, each having very different red shifts and very different speeds of recession, are merely accidentally aligned along the line of sight; that they have no real physical association.

Such statistical alignments must happen by chance every now and then. The debate centers on whether the number of coincidences is more than would be expected by chance.

The red shift is not the only evidence of the Big Bang. Image: © Elena

Arp points to other cases in which a galaxy with a small red shift is flanked by two quasars of large and almost identical red shifts. He believes the quasars are not at cosmological distances, but instead are being ejected, left and right, by the “foreground” galaxy; and that the red shifts are the result of some as yet unfathomed mechanism. Skeptics argue coincidental alignment and the conventional Hubble-Humason interpretation of the red shift.

If Arp is right, the exotic mechanisms proposed to explain the energy source of distant quasars – supernova chain reaction, supermassive black holes and the like – would prove unnecessary. Quasars need not then be very distant. But some other exotic mechanisms will be required to explain the red shift. In either case, something very strange is going on in the depths of space.

In fact the apparent recession of the galaxies, which the red shift interpreted through the Doppler effect, is not the only evidence of the Big Bang. Independent and quite persuasive evidence derives from the cosmic black body background radiation, the faint static of radio waves coming quite uniformly from all directions in the Cosmos and just the intensity expected in our epoch from the now substantially cooled radiation of the Big Bang.

Light is also a wave. The closer together the waves of sound or light are, the higher the frequency or pitch; the farther apart the waves are, the lower the pitch. If the car is racing away from us, it stretches out the sound waves, moving them, from our point of view, to a lower pitch and producing the characteristic sound with which we are all familiar. If, however, the car were racing toward us, the sound waves would be squashed together, the frequency would be increased and we would hear a high-pitched wail. If we knew what the ordinary pitch of the horn was when the car was at rest, we could deduce its speed blindfolded, from the change in pitch.