Do you believe in miracles?

Wait — I thought this was a science corner! It is; I am using part of a definition of “miracle” in the Oxford English Dictionary: “An extraordinary and welcome event that is not explicable by natural or scientific laws,” it says. The very first event, fitting that definition perfectly, was when our universe came into existence about 13.8 billion years ago, in what we call the Big Bang. That dictionary definition continues, “… and is therefore attributed to a divine agency.” While reasonable people can debate the meaning of that phrase, it is outside the domain of science (as is music, love and so much else). Science does not have an answer to this ultimate question of life, then universe and everything, unless it is 42 (check Douglas Adams).

The second miracle, happening right after the first, is that a tiny difference, one part in a billion, between matter and antimatter appeared. Scientists do not know how, but think it resulted in all the antimatter being annihilated. The leftover matter formed all the stars, planets and us. But this may be “explicable by a scientific law” one day; scientists are developing theories. It would still be “an extraordinary and welcome event”!

Life is most likely to develop on planets that are “not too hot, and not too cold, but just right”: the Goldilocks principle. In our solar system, Venus, Earth and Mars are in the so-called Goldilocks zone. The star Kepler-62 has seven known planets, three of which could have liquid water. The physics in the universe is also just right for life. How miraculous is that? Image: NASA/Ames/JPL-Caltech

“Lucky for us,” things kept happening. Hours after the Big Bang the universe was a rapidly expanding hot plasma of protons, electrons, antineutrinos and radiation, with some helium nuclei and little else. Helium nuclei are two protons and two neutrons stuck together by the strong nuclear force. But any free neutrons all decayed into protons, electrons and antineutrinos. This is possible because the neutron is a little heavier than a proton, but only by 0.14%. By all the known laws of physics it could have been the other way around, with neutrons lighter. Then free protons would have decayed into neutrons and positrons (and neutrinos), and hydrogen atoms would not exist. Oh dear!

Life as we know it needs carbon, too. That is another “lucky for us” piece of physics. No carbon was made in the Big Bang; it was made by three helium nuclei sticking together in exploding stars much hotter than the sun. In 1953 Fred Hoyle said this could happen only if carbon nuclei have an “internally excited state” with an energy close to 7.68 energy units (MeV). An experiment then confirmed this state, at 7.656 MeV. Had it been less than 7.3 or more than 7.9, very little carbon would have been made, and life as we know it would be impossible. Of the over 100 elements, only carbon has the ability to form molecules as complex as those in living creatures.

Many other miracles make our universe “just right for life” — the Goldilocks principle.

Food for deep thought.

Mike Albrow is a scientist emeritus at Fermilab.

This is a version of an article that originally appeared in Positively Naperville.