Treatise on natural philosophy : Vol 1. Part 2 / by Sir William Thomson and Peter Guthrie Tait.
- Date:
- 1883
Licence: Public Domain Mark
Credit: Treatise on natural philosophy : Vol 1. Part 2 / by Sir William Thomson and Peter Guthrie Tait. Source: Wellcome Collection.
Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.
521/594 page 491
![Cent.; and the greatest quantity of heat that we can explain, with any probability, to have been by natural causes ever acquired by the sun (as we shall see in the third part of this article), could not have raised his mass at any time to this tem- perature, unless his specific heat were less than 10,000 times that of water. We may therefore consider it as rendered highly probable that the sun’s specific heat is more than ten times, and less than 10,000 times, that of liquid water. From this it would follow with certainty that his temperature sinks 100° Cent, in some time from 700 years to 700,000 years. Sun’s specific heat probably between 10 and 10,000 times that of water; and fall of tempera- ture 100° Cent, in from 700 to 700,000 years. PART II. ON THE SUN’S PRESENT TEMPERATURE. % At his surface the sun’s temperature cannot, as we have many reasons for believing, be incomparably higher than tem- peratures attainable artificially in our terrestrial laboratories. Among other reasons it may be mentioned that the sun radiates heat, from every square foot of his surface, at only about 7,000 horse power*. Coal, burning at a rate of a little less than a pound per two seconds, would generate the same amount \ and it is estimated (Rankine, ‘ Prime Movers,’ p. 285, Ed. 1859) that, in the furnaces of locomotive engines, coalburns at from one pound in thirty seconds to one pound in ninety seconds, per square foot of grate-bars. Hence heat is radiated from the sun at a rate not more than from fifteen to forty-five times as high as that at which heat is generated on the grate- bars of a locomotive furnace, per equal areas. peratnre of the whole sun’s mass must (Part ii. below) be much higher than the “ surface temperature,” or “ effective radiational temperature.”—W. T Nov 9 1882.] * One horse power in mechanics is a technical expression (following Watt’s estimate), used to denote a rate of working in which energy is evolved at the rate of 33,000 foot pounds per minute. This, according to Joule’s determination of the dynamical value of heat, would, if spent wholly in heat, be sufficient to raise the temperature of 23£ lbs. of water by 1° Cent, per minute. [Note of Nov. 11, 1882. This is sixty-seven times the rate per unit of radiant surface at which energy is emitted from the incandescent filament of the Swan electric lamp when at the temperature which gives about 240 candles per horse power.] Sun’s superficial tempera- ture com- parable with what may be artificially produced.](https://iiif.wellcomecollection.org/image/b21987312_0521.jp2/full/800%2C/0/default.jpg)
