Ideas have interesting consequences. In the eighteenth century, Immanuel Kant (above, left) hypothesized that the solar system and the galaxy were the result of Newton’s laws of gravitation and motion. These would cause a cloud of matter, a nebula, to collapse into a disk — forming the Sun and its planets in the case of the solar system; forming the galactic disk in the case of the galaxy. So, does this idea immediately lead you to thinking about the existence of life on Earth? Well, Kant’s idea indeed had consequences regarding life on Earth. Sir William Thompson (right) talked about some of these in an address he gave at the forty-first meeting of the British Association for the Advancement of Science, held in Edinburgh, Scotland in August of 1871.
Thompson was the President of the Association at the time. He gave a long address — roughly 15,000 words (eight times the length of this post!) — about the BAAS, the prominent scientists of the past who had been part of it, and the progress of science since its formation. The last quarter of the talk, however, he dedicated to the subject of origins. “The old nebular hypothesis,” he said, speaking of Kant’s idea, “supposes the solar system and other similar systems through the universe which we see at a distance as stars, to have originated in the condensation of … nebulous matter. This hypothesis was invented before the discovery of thermo-dynamics,” that is, the physics of heat. Thompson noted how Hermann von Helmholtz, “adopting the nebular hypothesis,” showed in 1854 that the mutual gravitation within the original nebula would have generated heat — enough to explain “the present high temperature of the Sun.” The Sun should continue to be hot for “for several million years.” But nonetheless, he said, a slow cooling is taking place everywhere, and the current heat of the Sun is in large part a reflection of its “thermal capacity” being “enormous.” Smaller bodies like Earth, it follows, cool faster.
What, then, Thompson asked, does this mean for life? Because at one point, he noted, the Earth must have been barren:
Tracing the physical history of the Earth backwards, on strict dynamical principles, we are brought to a red-hot melted globe on which no life could exist. Hence when the Earth was first fit for life, there was no living thing on it. There were rocks…, water, air all round, warmed and illuminated by a brilliant Sun, ready to become a garden. Did grass and trees and flowers spring into existence, in all the fulness of ripe beauty, by a fiat of Creative Power?
That explanation won’t do, Thompson said. While he would end his speech by affirming “one ever-acting Creator and Ruler,” Thompson said that invoking that Creator’s power to explain life was not the role of science. “Science is bound,” he said, “by the everlasting law of honour, to face fearlessly every problem which can fairly be presented to it. If a probable solution, consistent with the ordinary course of nature, can be found, we must not invoke an abnormal act of Creative Power.”
Nor would science allow for the traditional scientific explanation for the existence of life — the “hypothesis of spontaneous generation,” as Thompson called it. This was the idea that, under the right conditions, life emerges naturally from inanimate matter. It has been the topic of many posts here at Sacred Space Astronomy (click here for some of those). Nineteenth-century science was killing off the spontaneous generation idea, which had endured since at least the time of Aristotle. It was becoming clear that life could never, ever be observed to be springing out of inanimate matter.
Thus, Thompson rejected that “very ancient speculation, still clung to by many naturalists.” He insisted that “science brings a vast mass of inductive evidence against this hypothesis of spontaneous generation…. Careful enough scrutiny has, in every case up to the present day, discovered life as antecedent to life. Dead matter cannot become living….”
So, if life does not naturally emerge from inanimate matter, and if science should not be invoking the Power of God to explain life’s origin, then what explanation did Thompson propose for its arising on Earth?
Meteors.
Things will collide in the universe, he said, and when something large enough collides forcefully enough into a life-bearing planet, bits of material with life on it will be hurled into space. These may eventually fall as meteors on some other planet, seeding it with life in the way life on Earth seeds a newly-formed volcanic island.
Should the time when this Earth comes into collision with another body… be when it is still clothed as at present with vegetation, many great and small fragments carrying seed and living plants and animals would undoubtedly be scattered through space. Hence and because we all confidently believe that there are at present, and have been from time immemorial, many worlds of life besides our own, we must regard it as probable in the highest degree that there are countless seed-bearing meteoric stones moving about through space. If at the present instant no life existed upon this Earth, one such stone falling upon it might, by what we blindly call natural causes, lead to its becoming covered with vegetation.
Thompson acknowledged that there were scientific objections to this idea, and that it “may seem wild and visionary”; but, the objections are “all answerable”; the idea is “not unscientific” (the contrast here with spontaneous generation or the invoking of Divine Power, he left unsaid). He continued:
From the Earth stocked with such vegetation as it could receive meteorically, to the Earth teeming with all the endless variety of plants and animals which now inhabit it, the step is prodigious; yet, according to the doctrine of continuity… all creatures now living on earth have proceeded by orderly evolution from some such origin. Darwin concludes his great work on “The Origin of Species” with the following words:
It is interesting to contemplate an entangled bank clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner, have all been produced by laws acting around us…. There is grandeur in this view of life with its several powers, having been originally breathed by the Creator into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms, most beautiful and most wonderful; have been and are being evolved.
With the feeling expressed in these two sentences I most cordially sympathise.
Thus, to sum up Thompson’s idea: Earth was once a lifeless red-hot globe, but when it had itself evolved to the point where it was ready to become a garden, it was seeded with some organism that had survived the rigors of being hurled from its native world and transported through space. From that space seed, life on Earth evolved, into all its elaborately constructed forms, so different from each other.
The idea of space seeds may have been wild and visionary, but it appealed to others, including Helmholtz, who had also started to advocate for it in the early 1870s. In Helmholtz’s view, life was an integral part of the universe, passing endlessly from world to world. The idea may seem improbable, he wrote in a preface to a translation he did of one of Thompson’s books,
But it seems to me a perfectly correct scientific procedure, when all our efforts to produce organisms from lifeless matter fail, to ask whether life ever arose at all, whether it is not just as old as matter, and whether its germs, carried from one celestial body to another, have not developed wherever they have found favorable soil.
The idea of space seeds did away with the question of an origin to life.
Svante Arrhenius had a similar view. The 1903 Nobel laureate for chemistry wrote in his 1908 book Worlds in the Making that,
Man used to speculate on the origin of matter, but gave that up when experience taught him that matter is indestructible and can only be transformed. For similar reasons we never inquire into the origin of the energy of motion. And we may become accustomed to the idea that life is eternal, and hence that it is useless to inquire into its origin.
Arrhenius gave the space seeds idea a catchy name, “panspermia”. He also proposed a gentler means of seeding space than collisions — tiny organisms that had been swept by winds into the upper atmosphere of their planet could be blown out of that atmosphere by the pressure of the light from its star. The light would accelerate them rapidly enough to transport them across the solar system in months, and to nearby stars in less than 10,000 years. Experiments with microbes at low temperatures suggested that the cold of space would preserve them.
Arrhenius would go on to argue in 1927 that the Earth was being seeded even now. He thought that thermophilic bacteria (those that live in very high temperatures), could only have evolved on a higher-temperature planet, and probably cannot sustain a population here over the long term. Therefore, Earth must be being supplied with them, and the most likely source was Venus. Arrhenius cited recent astronomical studies, suggesting that the temperature there might be around 120°F (50°C) — perfect for the bacteria he was noting. Organisms blown out of the Venusian atmosphere when Venus was passing between the Earth and the Sun could make it to the Earth in mere days, he said.
Thus, following Thompson, Helmholtz and Arrhenius, the panspermic Universe would be filled with life. Space would be filled with the drifting small organisms that are being blown continually into space from planets. Some of these seeds would be finding their way to other planets. If the planet a seed reached was not suitable to it, it would not thrive. If it was suitable, it would thrive. If the planet was suitable and lifeless, the seed could thrive over time — and through evolution, could lead to a life-filled world, an “entangled bank,” of diverse creatures. The universe should be rife with life-filled worlds.
Of course, one problem with this picture is that the astronomical studies of the 1920s were wrong about Venus. The temperature is far higher than Arrhenius supposed. Venus is a furnace-like, acid-swept hell-scape. Nothing lives there. There are other problems as well. But it is interesting to see how an idea about the formation of the solar system prompted thought about life on Earth.
