Threshold 5—Life Lecture 12
Most of the Universe as I’ve described it so far is still technically dead. It’s not alive. It can do lots of interesting things, as we’ve seen, but it’s not—strictly speaking—alive, not alive in the sense that you and I are alive.
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Lecture 12: Threshold 5—Life
e have described the creation of our Universe, our Sun, and our Earth. This lecture crosses a new threshold with the appearance of life. What is life? Life is one of those things that may seem easy to de¿ne until you try. Traditional accounts have often seen life as a divine gift, dependent on some kind of life force. But it has proved impossible to demonstrate scienti¿cally the existence of a creator-deity, and as we have seen, deistic theories always generate a new question: How was the creator created? Until the early 19th century, many scientists argued that there was a basic difference between the “organic” chemicals from which living organisms were made and the “inorganic” chemicals from which nonliving things were made. This idea was disproved in 1828 when German chemist Friedrich Wöhler (1800–1882) synthesized a simple organic chemical (urea) in a laboratory. Just as Newton has argued that the same physical laws applied in the heavens and on Earth, so this suggested that the same chemical laws applied to living and nonliving things. This implies there is a continuum between life and non-life, which may be why it is so hard to distinguish rigorously between life and non-life. Nevertheless, living organisms are different. First, they count as a higher level of complexity. Like all complex things, their existence depends on very speci¿c ways of organizing matter. Get the plan wrong and the organism dies. They have a degree of stability but eventually die. They display new, emergent properties. And they depend on Àows of energy to maintain their complexity. Indeed, these Àows seem to be denser than in all the other complex things we have seen, which justi¿es the claim that living organisms represent a higher level of complexity. Eric Chaisson has argued that energy 54
