The term “Kelvin’s Clouds” is a reference to a famous lecture given by Lord Kelvin (William Thomson) in 1900. It is often used to illustrate the limits of physics. I use it as the title of this blog as a reminder of the humility needed when considering fundamental questions about reality and the human condition.

Lord Kelvin was a famous scientist after whom the Kelvin temperature scale was named. On April 27, 1900, he delivered the Friday Evening Lecture at the Royal institution in London. In that lecture, he described two urgent challenges of conventional physics regarding “the theory of heat and light”. One of the challenges had to do with the luminiferous ether, and the other with something called the equipartition of energy. He described each of these problems as “clouds”.¹

The first cloud, regarding the ether, was resolved with the development of the theory of special relativity. The second cloud was resolved with the development of quantum physics. The development of these two new branches of physics completely redefined our understanding of reality.²

Today, we face a larger, even growing, set of clouds. For example, a theory called “M-theory”, which was hoped to unify relativity and quantum mechanics, has not been supported by the latest particle physics experiments, leaving a whole host of questions without a clear path to solution. Other examples exist both within and outside physics such that we clearly need to be careful when making assertions of absolute truth.

In particular, metaphysical views are often held with deep certainty even though Kelvin’s Clouds should teach us that we need to be humble and constantly learning. Questions regarding science and religion are often contentious, but it seems clear that we really don’t know enough about the world to be certain about things like the existence of God, the ultimate nature of consciousness and humanity, whether life has purpose and meaning beyond what we give it, and so on.

Of course, over time we will continue to learn and perhaps some clouds will be eliminated, perhaps some mysteries will be solved. But, maybe not all. Maybe there are fundamental limits to our ability to know.

In either case, we can’t just throw up our hands until everything is clear, we need to decide how to live in the face of uncertainty, to prioritize and make decisions in life. We each need some perspective, some worldview to make sense of what we do know.

Ideally, one’s worldview would be informed by a variety of perspectives, constantly learning and (when necessary) adapting, and rational without being dogmatic.

The goal of this blog is to explore my own views on science and faith, hopefully in a way that embodies those principles.

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(1) many references to this speech describe Kelvin’s second cloud as having to do with block body radiation, but that is incorrect. A good description of the speech and its history can found in this paper: Oliver Passon , “Kelvin’s clouds”, American Journal of Physics 89, 1037-1041 (2021) https://doi.org/10.1119/10.0005620

(2) In addition, the development of quantum mechanics and relativity have shown us that there may be fundamental limits in our ability to describe reality due to the lack of infinite precision in measurements and the hard limit of the uncertainty principle.