Our Goldilocks Planet By William Lama, Ph.D
Our Universe
Eight billion people is a fantastic achievement, but the amazing part of that story is how we all got here.
The Earth was clumped together from gas and dust surrounding the young Sun by gravitational forces about 4.5 billion years ago. For a few billion years the Earth’s environment was totally hostile to life, much less human life. So, what happened?
I’m reminded of when I bagged groceries at my parent’s store while mom womaned the cash register. For female customers I frequently offered to carry bags to their cars. Sometimes the women would say something nice about me to my mom. Her standard reply was: “You don’t think he came out that way!” Indeed, I did not. And neither did the Earth. Our Goldilocks planet had to change massively in innumerable ways to support life, much less 8 billion homo-sapiens.
In fact, the entire Universe had to be precisely constructed and governed to make our existence possible. In my last article I mentioned some of the unique conditions that made a life-supporting world possible. Nature’s laws seemed to be “fine-tuned” to enable the creation of a planet where life could exist. They called this the “anthropic principle” - but many scientists dreamed up a magical “multiverse” in an attempt to explain our miraculous luck.
Do You Believe in Magic? by William Lama, Ph.D — Palos Verdes Pulse
In the opinion of astronomer Fred Hoyle: “A common sense interpretation of the facts suggests that a super-intellect has monkeyed with physics, as well as with chemistry and biology.”
Astrobiology is the science that studies the conditions necessary to support life. Let’s begin with timing.
Timeline
The universe was born 13.7 billion years ago, if you believe in the Big Bang.
Big Bang Cosmology - Believe it or Not by William Lama Ph.D. — Palos Verdes Pulse
It took about a billion years for the first stars to condense and our solar system formed about eight billion years later. The timing was fortuitous. A life-supporting planet requires elements heavier than the hydrogen and helium that were formed in the aftermath of the Big Bang. Carbon, nitrogen, oxygen and other crucial elements are made in the nuclear furnaces of giant stars, and that took billions of years.
Radioactive isotopes are needed in the core of the Earth to produce the heat that drives plate tectonics that leads to the production of continents. The heat from the radioactive isotopes also drives the circulating currents that produce the Earth’s magnetic field that shields us from dangerous cosmic rays. Such critical isotopes as uranium-235 and thorium-232 are produced by exploding supernova. These supernova processes took about eight billion years. Is it a magical coincidence that the Solar System was formed about eight billion years after the Big Bang, when the crucial elements and isotopes were available?
But when was the Earth completely ready to support life?
The young Sun was a source of x-ray and gamma-ray emission that would kill any life within the Solar System. But by 4.5 billion years after its birth the Sun’s flaring activity and intensity had decreased to levels sufficient to protect our atmosphere, hydrosphere, and living creatures.
In the following figure the y-axis is logarithmic. The Sun’s flaring activity level (and its x-ray and gamma-ray emission) was 100,000 times higher just after its formation than it is now. We live at just the right time (dashed line) on our Goldilocks Earth.
Moon's Early Magnetic Field Made Human Existence Possible - Reasons to Believe
More recently, the Earth has experienced Ice Ages for the last several million years. The temperature of the most recent Ice Age is plotted in the following figure.
The Last Ice Age. Data from the North Greenland Eemian Ice Core.
Note that the temperature scale is relative to today = 0 (actually today = +15C) and that time runs from right to left. We live in the Holocene interglacial period.
At the last glacial maximum, the average Earth temperature was 9C less than today. That Ice Age lasted for 100,000 years and life for humans was precarious. On the other hand, the temperature for the last 9000 years has been remarkably constant and conducive to the growth of agriculture and civilization. The human population exploded from a few million to 8 billion today. We live at absolutely the best time in the history of the Earth, and in just the right place.
Location, location, location.
Like the importance of location in real estate, our location in the Solar System is ideal for life.
The Earth is in the ideal orbit, with a livable average temperature, an atmospheric concentration of carbon dioxide that regulates the Earth’s temperature, and a strong magnetic field that blocks harmful cosmic rays. Our neighbors Venus and Mars are not so hospitable.
Astrobiologists refer to the planetary orbits where life could exist as “habitable zones.”
Liquid water must be available on the planet surface. Impacts of asteroids and meteors with the Earth delivered just the right amount of water and an ideal atmosphere, including the carbon needed for life.
UV radiation from the sun must be neither too strong nor too weak. Vitamin D production requires adequate exposure to UV, while too much UV is harmful. The planet’s atmosphere must contain sufficient ozone to block most of the extreme UV.
Habitable zones must enable plant photosynthesis, which requires specific ranges of light intensity, temperature, carbon dioxide, minerals and water.
These and other very special requirements for the existence of life on a planet are described in the fascinating book Improbable Planet by Hugh Ross
Some say the world will end in fire,
Some say in ice.
From what I’ve tasted of desire
I hold with those who favor fire.
Robert Frost
In addition to our ideal orbit, we also needed a companion. Formation of our Moon tuned-up the Earth for the possibility of life. According to planetary theory, a large Mars-sized object (called “Theia”) collided with the young Earth and glanced off. Heavy metals including iron and uranium from Theia sank into the Earth. What was left of Theia settled into a stable orbit around the Earth. This new Moon’s mass stabilized the rotation axis of the Earth protecting us from extreme climate variations.
Our Future
Given that we are living in just the right place at just the right time, it is natural to wonder how long our good luck will last. By looking at the temperature history of the Earth prior to the last Ice Age we get a hint of the future.
This graph shows the Earth temperature and carbon dioxide concentration for the last four Ice Age cycles. Prior to the Eemian warm period there was another 100,000-year Ice Age. In fact, the cycle of Ice Ages and interglacial warm periods has persisted for two million years. It is interesting that the change in temperature precedes the change in CO2 as time progresses from right to left.
The drivers of this cyclic behavior are well understood (Improbable Planet) and this cycle is expected to persist for at least another million years. Within a thousand years or so we will see the ice return.
In the 1970’s the Earth cooled a bit and many people worried about the return of the Ice Age. Science News published an issue in 1975 with a cover showing the returning glaciers destroying New York City.
Imagine the price of land in Palos Verdes when that happens.
The Ice Age Cometh? March 1, 1975
William Lama Bio
Dr. William Lama has a PhD in physics from the University of Rochester. Taught physics in college and worked at Xerox as a principle scientist and engineering manager. Upon retiring, joined the PVIC docents; served on the board of the RPV Council of Home Owners Associations; served as a PV Library trustee for eight years; served on the PV school district Measure M oversight committee; was president of the Malaga Cove Homeowner's Association. Writes about science, technology and politics, mostly for his friends. email: wlama2605@gmail.com
