Rare Jewel: Earth-like Planets May Be Very Rare

Archdiocese of Washington ^ | 02-28-16 | Msgr. Charles Pope

[Salvation]

Rare Jewel: Earth-like Planets May Be Very Rare

Msgr. Charles Pope • February 28, 2016 •

I have written a good bit over the years about what is known as the “Rare Earth” Hypothesis. A recent blog on discovermagazine.com ponders how high the odds are against the existence of another Earth-like planet. More on that in a moment. But first let’s review some of the basics of the Rare Earth Hypothesis.

While most people, including most scientists, believe that there may be billions of inhabitable planets out there a capable of sustaining complex life, the Rare Earth Hypothesis suggests that such a large number is overstated.

This is because there are not just a few things that come together to support life here on Earth, there are many. Here are some:

1. Earth is at just the right distance from the Sun so that water is warm enough to melt, but not so hot as to boil and steam away into space. Water is also able, in this habitable zone (the so-called “Goldilocks” region), to both evaporate and condense at lower levels in the atmosphere, thus permitting a more even distribution of water, and the cycle of water over dry land known as precipitation.
2. For suns to spawn Earth-like planets they must have sufficient “metallicity,” which is necessary for the formation of terrestrials rather than gaseous planets.
3. Earth is in a “habitable zone” within the galaxy as well. Closer to the center of galaxies, radiation and the presence of wandering planetoids make life there unlikely.
4. Earth exists in a disk-shaped spiral galaxy (the Milky Way) rather than in an elliptical (spheroid) galaxy. Spiral galaxies are thought to be the only type capable of supporting life.
5. Earth’s orbit around the sun is an almost perfect circle rather than the more common “eccentric” (elongated) ellipse. Steep elliptical orbits take a planet relatively close to and then relatively far from the sun, with great consequences for warmth and light. Earth’s stable, nearly circular orbit around the sun keeps our distance from it relatively constant, and hence the amount heat and light does not vary tremendously.
6. Two nearby “gas giants” (Jupiter and Saturn) attract and catch many wandering asteroids and comets and generally keep them from hitting Earth. The asteroid belts also keep a lot of flying rock in a stable orbit and away from us.
7. Our molten core creates a magnetic field that holds the Van Allen radiation belts in place. These belts protect Earth from the most harmful rays of the sun.
8. Earth’s volcanism plays a role in generating our atmosphere and in cycling rich minerals widely.
9. Our sun is just the right kind of star, putting out a fairly steady amount of energy. Other types of stars are more variable in their output and this variance can utterly destroy life or cause it to be unsustainable due to the extremes caused.
10. Earth’s fairly rapid rotation reduces the daily variation in temperature. It also makes photosynthesis viable because there is enough sunlight all over the planet.
11. Earth’s axis is tilted just enough relative to its orbital plane to allow seasonal variations that help complex life but not so tilted as to make those variations too extreme.
12. Our moon also has a good effect by causing tides that are just strong enough to permit tidal zones (a great breeding ground for diverse life) but not so severe as to destroy life by extreme tides.

There are many more items on the list (see the first video below), but let these suffice. The conditions that come together on this planet such that it is capable of sustaining complex life are complicated, remarkable, and some argue rare in the universe. The ability to support life here is the balance of many fascinating things. We cannot but be amazed at the complexity of life and the intricacies it takes in order for it to flourish here. It would appear that for complex life to be sustained, many factors must come together in just the right way. The sheer number of these factors sharply decreases the number of possible Earth-like planets, despite the many billions of galaxies and stars.

All this background information leads us back to the recent blog at discovermagazine.com: Earth-is-a-1-in-700 quintillion kind of place. (700 quintillion is 7 followed by 20 zeros). The blog references a study by Astrophysicist Erik Zackrisson from Uppsala University in Sweden.

Here are some excerpts:

Zackrisson’s work suggests an alternative to the commonly held assumption that planets similar to Earth must exist, based on the sheer number of planets out there …. Current estimates hold that there are some 100 billion galaxies in the universe containing about 10^18 stars, or a billion trillion …. Probability seems to dictate that Earth-twins are out there somewhere.

But according to Zackrisson … Earth’s existence presents a mild statistical anomaly in the multiplicity of planets …. Most of the worlds predicted … orbit stars with different compositions—an important factor in determining a planet’s characteristics. His research indicates that, from a purely statistical standpoint, Earth perhaps shouldn’t exist …. Researchers are confident in the broader implications of their model: Earth is more than your garden-variety planet.

I write on this topic more in wonder and awe than anything else. There is no necessary requirement of our faith that we must believe ourselves alone in the whole universe. God can, and even might have, created intelligent beings on other planets, beings with whom He interacts and whom He loves.

But neither should we too quickly assume that Earth is not a rare jewel. Statistically, it would seem that there is good evidence that we and Earth are rare jewels. Humble amazement at all that it takes to sustain life on our planet is a proper stance at this stage of the evidence. The more we learn, the more it seems that the convergence of all the factors we enjoy on Earth is rare rather than commonplace. Consider well all that God and nature, sustained by God, have done so that you and I can exist. Be amazed; be very amazed!

[Salvation]

Video I

Video II

[Bidimus1]

The goldilocks zone is a small place indeed.

That Life might exist on planets not like earth is of course a possibility, who 100 years ago would have thought the deep sea vent ecology could exist ?

[Salvation]

Monsignor Pope Ping!

[CodeToad]

“who 100 years ago would have thought the deep sea vent ecology could exist ?”

That’s been my thought. We never knew hot sulfur regions could support life.

[BenLurkin]

Plus the nature of the Earth and moon as an unusual “double planet” makes a huge difference as well.

[JimRed]

Since the universe goes on forever, this rare occurrence may only consist of hundreds of trillions of inhabited planets. God’s wonders!

[Robert A Cook PE]

Well, you only need one place. One Eden for life to begin as we know it.

He never did promise us more than one.

[stocksthatgoup]

Could we exchange our Pope for a Catholic?

[posterchild]

I’d be curious to learn more about the reasoning behind 4.

There may well be other ways of achieving a ‘goldilocks zone.’ Imagine a description of a modern automobile and declaring all it’s attributes as the ideal way to provide transport just because that is the prevalent example we have.

[Pelham]

“Since the universe goes on forever”

It’s finite.

[Lazamataz]

I speculate that creatures made up entirely of cohesive magnetic fields exist inside stars.

[Ransomed]

“It would appear that for complex life to be sustained, many factors must come together in just the right way. The sheer number of these factors sharply decreases the number of possible Earth-like planets, despite the many billions of galaxies and stars.”

Seem like all this is only true if the hypothetical life is exactly like the only extant organic life we know of, us. So I’m not sure we can say how rare something is or not based on an example of the one place we know of where it occurs.

Freegards

[Lazamataz]

The universe does not go on forever. It goes on forever plus one foot.

[Delta 21]

Expand your mind to try to grasp and comprehend how our God tossed out the entire universe like so many marbles from the hand of a child into the sand. Then made this one especially just to hold his children.

[Delta 21]

A life of endless uber-gravity and magnetic swirlings is no life at all, man.

[Rebel_Ace]

Some of the points are easily observable in both our and extra solar systems. For example:

"For suns to spawn Earth-like planets they must have sufficient “metallicity,” which is necessary for the formation of terrestrials rather than gaseous planets."

This has been observed in extra solar star forming regions.

"Earth is in a “habitable zone” within the galaxy as well. Closer to the center of galaxies, radiation and the presence of wandering planetoids make life there unlikely."

Fair point, but if you create a "donut shape" around the center of the Milky Way, delineating this habitable zone, there are lots and lots of stars to consider.

"Earth’s orbit around the sun is an almost perfect circle rather than the more common “eccentric” (elongated) ellipse."

The orbits of Venus and Mars are also highly circular. So are the orbits of most of the others in our solar system. So, just in our neck of the woods, we are something like 6 out of 8.

"Earth’s axis is tilted just enough relative to its orbital plane to allow seasonal variations that help complex life but not so tilted as to make those variations too extreme."

Mars is currently tilted at the nearly the identical angle. Again, just in our Solar System, we are 2 for 8.

"Earth exists in a disk-shaped spiral galaxy (the Milky Way) rather than in an elliptical (spheroid) galaxy. Spiral galaxies are thought to be the only type capable of supporting life."

No reason is given for this assumption. If a DISK shaped galaxy has a donut shaped habitable zone, then a SPHERE shaped galaxy should have a Spherical Shell shapped habitable zone.

"Our sun is just the right kind of star, putting out a fairly steady amount of energy. Other types of stars are more variable in their output and this variance can utterly destroy life or cause it to be unsustainable due to the extremes caused."

Red Dwarfs also fall into the category of steady producers of energy, and they have the added advantage of being much, MUCH longer lived.

Just a few things to consider when pondering how rare the Earth is. Also, keep in mind what a tiny, tiny, really, really tiny fraction of the galaxy we have had any real kind of look at.

[PIF]

If you hold up your thumb to the sky at night, you block the light from a trillion galaxies; If you hold up a grain of sand to the sky at night, you block the light from a billion galaxies.

How many thumbs does it take to completely block the night sky around the entire globe of the Earth? Compute the total number of galaxies in the universe. Hint: find a number above 70 billion trillion.

Multiply that number times the average number of stars in a galaxy (300,000,000) to get the total number of stars in the universe.

Assume each star has only 1 planet; assume that only 20% of all plants are in the carbon cycle habitable zone; assume that of those planets only 1 percent currently have intelligent life: how many planets is that?

Assume you have a starship capable, for arguments sake, of Warp Nine and can stop instantaneously: how long will it take the ship to visit all the planets which currently have intelligent life?

Discuss how the number of planets with intelligent life will change during the course of the trip. And discuss whether or not you will have to visit and revisit all the stars that exist by the time you finish visiting them all the first time.

[Moonman62]

The Rare Earth position matches observations, at least up to this point.

[PIF]

And like a Spanish prison, when you get to the extra one foot make G-d adds another foot ...

[butlerweave]

What if Earth type planets are the worst type to live on and habitable planets are completely different ? It’s always about us