I don’t really have the energy to talk about climate change at the moment, but did come across a paper that I thought some might find interesting. It’s by Steven Balbus and is called Dynamical, biological, and anthropic consequences of equal lunar and solar angular radii. As the title indicates, the Moon and the Sun have about the same angular size and people have often pondered if this was simply a coincidence or not. Could it be that having the same angular size has played a role in the evolution of a – supposedly – intelligent species?
A consequence of this similar angular size is that the tidal influence of the Moon and the Sun are about the same. This means that when you combine their influence, you get a beat pattern in the tidal height: over a period of many days, the height of the tide can vary quite substantially. This wouldn’t happen if there were only a single body producing the tides, or if one body were very dominant. This is illustrated in the Figure below which, you may notice, is for the Devonian period (420 – 360 Million years ago).
So, why is this interesting for the Devonian? This is where I get well outside my comfort zone, but my understanding is that the Devonian is the only period during which vertebrates moved from the oceans to the land. Also, if you look at the figure below, which is for the early Devonian, this happened mainly on the coastline on either side of the narrowing channel between the continents.
The basic idea in the Balbus (2014) paper is that this narrowing channel meant that the tidal height would increase as the tide moved into this channel (the tidal height figure above is only for the equilibrium tide). When the tide was very high, it would wash quite far inland. However, when the tide height started dropping, it would do so rapidly and would leave behind many now isolated tidal pools. The consequence of this is that those vertebrates that could maneuver on land, would have an advantage. They could both escape from the isolated pools if trapped, but could also feed on other animals trapped in these pools. The basic idea is therefore that a combination of the combined tidal influence of the Moon and Sun, the configuration of the continents during the Devonian, and Natural Selection is what lead to the movement of some vertebrates from the oceans to the land.
One can also consider the relevance of this with respect to the anthropic principle. The anthropic principle (in its weak form at least) is that the reason our planet and the Solar system look the way they do is because if they didn’t, we wouldn’t be here to ask that question. Of course, we don’t actually know if the conditions for the development of complex, intelligent life are rare or not. However, the more we encounter rather unlikely scenarios that seem to have been required for our development (such as that presented in Balbus 2014), the more we might start concluding that complex, intelligent life in our galaxy is more likely to be rare, than common. Maybe we really are alone.