When I suggested in my first publication on this subject that some emanations from the stars might be beneficial or injurious, and that a central position might be essential in order to render these emanations equable, one of my astronomical critics laughed the idea to scorn, and declared that 'we might wander into outer space without losing anything more serious than we lose when the night is cloudy and we cannot see the stars.'[22] How my critic knows that this is so he does not tell us. He states it positively, with no qualification, as if it were an established fact. It may be as well to inquire, therefore, if there is any evidence bearing upon the point at issue.
Astronomers are so fully occupied with the vast number and variety of the phenomena presented by the stellar universe and the various difficult problems arising therefrom, that many lesser but still interesting inquiries have necessarily received little attention. Such a minor problem is the determination of how much heat or other active radiation we receive from the stars; yet a few observations have been made with results that are of considerable interest.
In the years 1900 and 1901 Mr. E.F. Nichols of the Yerkes Observatory made a series of experiments with a radiometer of special construction, to determine the heat emitted by certain stars. The result arrived at was, that Vega gave about 1/200000000 of the heat of a candle at one metre distance, and Arcturus about 2.2 times as much.
In 1895 and 1896 Mr. G.M. Minchin made a series of experiments on the Electrical Measurement of Starlight, by means of a photo-electric cell of peculiar construction which is sensitive to the whole of the rays in the spectrum, and also to some of the ultra-red and ultra-violet rays. Combined with this was a very delicate electrometer. The telescope employed to concentrate the light was a reflector of two feet aperture. Mr. Minchin was assisted in the experiments by the late Professor G.F. Fitzgerald, F.R.S., of Trinity College, Dublin, which may be considered guarantee of the accuracy of the observations. The following are the chief results obtained:—
| Source of Light. | Deflection in Millimetres | Light in Candles. | E. M. F. Volts. | |
| 1896 | Candle at 10 feet distance | 18.70 | ||
| Betelgeuse (0.9 mag.) | 12.80 | 0.685 | 0.026 | |
| Aldebaran (1.1 mag.) | 5.21 | 0.279 | 0.012 | |
| Procyon (0.5 mag) | 4.89 | 0.261 | 0.011 | |
| Alpha Cygni (1.3 mag.) | 4.90 | 0.262 | 0.011 | |
| Polaris (2.1 mag.) | 3.10 | 0.166 | 0.007 | |
| 1 volt. | 432.00 | |||
| 1895 | Arcturus (0.3 mag.) | 8.2 | 1.01 | 0.019 |
| Vega (0.1 mag) | 11.5 | 1.42 | 0.026 | |
| Candle at 10 feet | 8.1 |
N.B.—The standard candle shone directly on the cell, whereas the star's light was concentrated by a 2-foot mirror.
The sensitive surface on which the light of the stars was concentrated was 1/20 inch in diameter. We must therefore diminish the amount of candle light in this table in the proportion of the square of the diameter of the mirror (in 1/20 of an inch) to one, equal to 1/230400. If we make the necessary reduction in the case of Vega, and also equalise the distance at which the candle was placed, we find the following result:—
| Observer. | Star. | Candle power at 10 ft. |
| Minchin. | Vega | 1/162250 |
| Nichols. | " | 1/22000000 |
This enormous difference in the result is no doubt largely due to the fact that Mr. Nichols's apparatus measured heat alone, whereas Mr. Minchin's cell measured almost all the rays. And this is further shown by the fact that, whereas Mr. Nichols found Arcturus a red star, hotter than Vega a white one, Mr. Minchin, measuring also the light-giving and some of the chemical rays, found Vega considerably more energetic than Arcturus. These comparisons also suggest that other modes of measurement might give yet higher results, but it will no doubt be urged that such minute effects must necessarily be quite inoperative upon the organic world.
There are, however, some considerations which tend the other way. Mr. Minchin remarks on the unexpected fact that Betelgeuse produces more than double the electrical energy of Procyon, a much brighter star. This indicates that many of the stars of smaller visual magnitudes may give out a large amount of energy, and it is this energy, which we now know can take many strange and varied forms, that would be likely to influence organic life. And as to the quantity being too minute to have any effect, we know that the excessively minute amount of light from the very smallest telescopic stars produces such chemical changes on a photographic plate as to form distinct images, with comparatively small lenses or reflectors and with an exposure of two or three hours. And if it were not that the diffused light of the surrounding sky also acts upon the plate and blurs the faint images, much smaller stars could be photographed.