126 ANTTOAL REPORT SMITHSONIAN INSTITUTION, 1942 



table 1, suggest that the law of red shifts i^robably does not operate 

 within the group. This conclusion is positive evidence supporting the 

 validity of the theory. If the universe is expanding, the group main- 

 tains its dimensions as the theory requires. 



The remainder of the recently accumulated information is not favor- 

 able to the theory. It is so damaging, in fact, that the theory, in 

 its present form, can be saved only by assuming that the observational 

 results include hidden systematic errors. The latter possibility will 

 naturally persist until the investigations can be repeated and improved. 

 Nevertheless, a careful reexamination of the data now available sug- 

 gests no adequate explanation of the discrepancies. 



Table 2. — Radial velocities in the Local Group 



The observed velocities (second column) represent a more reasonable distri- 

 bution than the velocities corrected for red shifts (fifth column). The latter 

 are all large and negative with the exception of the first two, for which the red 

 shifts are insignificant. This fact suggests that the law of red .shifts does not 

 operate within the Local Group. 



LOCAL GROUP 



Distance in Velocity 

 million with 



Observed ligbt- Expocted red shift 



Known members velocity years red shift removed 



L M C + 45 0.085 +13 +32 



SMC +13 0.095 +10 — 3 



M 31 —130 0.7 +110 —240 



M 33 —150 0.7 +110 —260 



NGC 6822 +20 0. 5 +85 — 60 



IC 1613* 1.3 +210 



Fornax — 40 0.6 +100 —140 



Probable members 



NGC 6946 +90 1.6 +265 —175 



NGC 1569 + 60 2.3 +370 —310 



TC 342 +30 2.3 +370 —340 



*A spectrum of an object in IC 161.3, obtained by Baade. shows a definitely negative 

 velocity. The numerical value of the velocity is ratlier uncertain, and, for this reason is 

 not included in the table. However, the negative sign indicates that IC lfil3 is consistent 

 with the other members of the Local Group. 



THE INTERPRETATION OF RED SHIFTS 



The investigations were designed to determine whether or not red 

 shifts represent actual recession. In principle, the problem can be 

 solved; a rapidly receding light source appears fainter than a simi- 

 lar but stationary source at the same momentary distance. The ex- 

 planation of this well-known effect is quite simple when the beam 

 of light is pictured as a stream of discrete quanta. Rapid recession 

 thins out the stream of quanta, hence fewer quanta reach the eye 

 per second, and the intensity, or rate of impact, is necessarily re- 



