What, you may be thinking, have those three things in the title have to do with each other? Answer: exponential growth – I would say so in the title, but I wanted you to read on. Thank you, keep reading.
What these things, Earth’s population and much else have in common is exponential growth. That is repeated multiplication: doubling, doubling, doubling, … or tripling, tripling, …but I have a word-count limit. But while that can be done in mathematics, in the real world – I mean physics – it cannot happen forever; something always happens to stop it. With the possible exception of the expansion of the Universe, and we’re not sure about that.
We’re also not sure how our Universe got started – about 13.7 billion years ago. But the best theory we have is called “inflation.” That supposes the whole universe started out a trillion-trillion times smaller than the period at the end of this sentence. Something caused it to grow exponentially; we don’t know what, but theorists are working on it. In a US-decillionth (0 point 33 zeros!) of a second it became the size of a baseball. Then that inflation suddenly stopped. Space became incredibly hot (that’s the Big Bang) and continued expanding more gracefully. It still is, cooling as it expands. If that inflation had not stopped when it did, we would not be here.
In an atomic bomb, a uranium or plutonium nucleus is hit by a neutron and breaks apart, releasing energy and more neutrons, each of which can break more nuclei. That’s a chain reaction, exponential growth, another big bang (small b’s). That cannot continue, as the sudden intense heat blows the nuclei far enough apart to stop multiplying – fortunately.
In an infectious disease, if one person infects two others one day, and if they each infect two more the next day, that would be exponential growth. In 20 days more than a million people would be infected. That’s just mathematics, and I said “if” twice; in the real world those ifs do not happen so fast, largely by limiting contact, avoiding crowds, “social distancing.” And not everyone gets infected.
The world’s population is growing exponentially, albeit slowly – the doubling time is now about 60 years. But that cannot possibly continue forever; science forbids it. If we do not slow the growth ourselves, it will happen catastrophically. Another thing atom bombs and pandemics could have in common. Take care.
