If We Are Alone

It's Full of Planets!

Over 400 exoplanets discovered so far. Finding more expolantes is almost becoming normal - and its not just "hot Jupiters" that are being found. Increasingly, as our techniques and equipment improve and more telescopes are brought online to join the hunt, smaller terrestrial planets are being found. Everywhere we look, it seems, we find planets. It is looking like the universe is full of planets.

Think abut that. Full of planets. Maybe in 2001: A Space Odyssey astronaut David Bowman should've exclaimed "The thing's hollow—it goes on forever—and—oh my God—it's full of planets!"

Apply the Drake Equation, and it's looking like the universe is also full of life, including intelligent life.

However...

This does not automatically mean we are not alone. If the universe is infinite, and life arose in one spot of it, it does seem incredibly unlikely we would be the only ones. Even if the universe is not infinite - it still contains at least 100 billion galaxies, each with many stars (our own contains an estimated 100 billion stars), many of which may contain planets. The number of possible planets is astounding. However, while it may seem rather implausible, just because the universe may be populated with planets is not a Q.E.D. proof that we are not alone, despite, as Jodi Foster's character in the movie Contact propositions, that "if we are the only ones, it would be an awful waste of space, wouldn't it?"

If We Are Alone

What would that mean, if we were alone? That we are given, or by chance have, all this space in which to  explore, expand, and evolve in? If we are given all of the immense space filled with stars and planets, but no other life - what is the purpose of that gift? What are our responsibilities? Should we go forth, multiply and replenish not only the Earth but the universe? Or should we leave other planets alone and not contaminate them with Earth probes and the Earth microbes that may be on them?

And does it even have to have a meaning? The universe does not know it is immense, or teeming with planets. A star does not know that it exists. It does not feel itself traveling through space, circled by planets. Gravity acts upon it without it knowing that anything at all is happening. A planet does not know that it is barren, or that it has life on it. It is barren, or life-filled, only to us (if any of this has an echo of familiarity to it, it may be because you've read Nobel Prize winning Polish poet Wislawa Szymborska's thought provoking poem "View with a Grain of Sand"). Meaning is arbitrary, maybe illusory.

What is Meant

But even if that meaning is arbitrary, and only has meaning to us - that may be enough. It may be up to us to give beauty to the universe, to create meaning, even if it is only for our benefit, our pleasure, our peace of mind.

I have no answers. I would be stunned if there were no other life forms outside the Earth. But, I also realize that true absolutes rarely exist, and to say it is impossible is wrong. It may be astronomically (if you'll excuse the pun) improbable, but not impossible.

What do you think?


Image Credits: 1. Warner Bros. 2. Chris Butler.

Life Outside the "Zone."

As I've stated in earlier posts, I support the idea that extrasolar life may be readily found outside the traditional "Habitable Zone" or the "Goldilocks" zone around a star - the band of space around a star that is neither too cold nor too warm for liquid water to exist. This is too simplistic. Liquid water can be found outside this zone - mainly on moons circling large planets. The tidal forces of the planet on the moon can cause the moon to heat up through internal friction. This is especially true if the moon is in an elongated orbit.

How does this work? This is due to the fact that gravity decreases with distance and the gravitational pull on the near side of the moon is greater than the gravitational pull on the far side. For a moon in a circular orbit, the moon will adjust its shape to adapt to this gravitational differential, and no tidal heating will occur. But for a moon in an eccentric orbit, the gravitational differential will change rhythmically, and the moon will be kneaded like a lump of bread dough (OK, a bit of an exaggeration). This will heat a moon even if it is outside of the solar system's main habitable zone. This increases the areas in a solar system where life can form.

Recent research by Brian Jackson, Rory Barnes, and Richard Greenberg of Arizona's Lunar and Planetary Laboratory extends this idea to planets (this research will be published in an upcoming issue of Monthly Notices of the Royal Astronomical Society). Most extrasolar planets found to date circle their stars in elongated orbits. Like a moon circling a large planet, these planets circling a large star in elongated orbits will experience tidal stress, which will cause internal heating and possibly tectonic activity. This internal heating may be enough to warm the planet to where liquid water can exist even when the planet's orbit takes it outside of its star's traditionally defined Habitable Zone.

However, because the tidal heating scales with the size of the planet, for "super-Earths," terrestrial planets 2 to 10 times the size of the Earth, the tidal heating would be too great to make the planet habitable - the planet may become too hot, with many large active volcanoes.

But for Earth-sized or smaller terrestrial planets that would otherwise be too small or too cold to support life, this type of tidal heating may help them become habitable by not only warming them up so that liquid water can exist but also by causing tectonic activity which may help life to arise. Some scientists feel that the Moon was essential to the origin of life on the Earth due to the tidal mixing which helped to mix, mainly from erosion caused by the tides, chemicals from the soil with the oceans, creating the chemical soup from which life arose. The tidal forces of a star on planet in an elongated orbit may have the same result. In addition, tectonic activity helps regulate carbon dioxide.

Therefore, I believe that the famous Drake Equation may be a bit too conservative. The number of planets (or moons!) that potentially can support life may be higher than first thought.

Reference:

"Tides have major impact on planet habitability." Astronomy. Kalmbach Publishing Co. 14 Oct. 2008. Web. 31 Oct. 2008. Provided by the Div. for Planetary Sciences of the American Astronomical Society. <http://www.astronomy.com/asy/default.aspx?c=a&id=7505>.

Habitable Moons - Are They Common?

"Thetis Moon" © DigitalBlasphemy.com

Earlier posts discussed the possibility of habitable moons, including how they may increase the habitable zone of a solar system, which would then affect the Drake Equation, giving it a larger number for N (the number of civilizations we can communicate with at this time in the galaxy).

Recent work by Caleb Scharf, Columbia University's Director of Astrobiology, points to the possibility that habitable moons may not be rare - they may even be as common as habitable planets.

Take a look at our own solar system as an example. Our solar system has several moons that, if orbited the sun instead of a planet, would be large enough to be considered planets themselves. Several of them have atmospheres, and at least one, Europa, is almost certain to have liquid water - though recent articles, which will be discussed in later posts, suggest that life can exist in ice, and that, thus, liquid water may not be necessary for life to exist (though it may be necessary for sentient life to evolve).

If our system is not unusual, then it should be common for extrasolar systems to have many moons as well, some of them large enough to have atmospheres and to retain water. As we've seen in previous posts, water is found to be rather common in planetary discs and systems (¹).

However, a heat source is needed. And to the rescue comes tidal forces: tidal forces caused by the moon's parent planet which will create internal heat for the moon. This is due to the fact that gravity decreases with distance and the gravitational pull on the near side of the moon is greater than the gravitational pull on the far side. For a moon in a circular orbit, the moon will adjust its shape to adapt to this gravitational differential, and no tidal heating will occur. But for a moon in an eccentric orbit, the gravitational differential will change rhythmically, and the moon will be kneaded like a lump of bread dough (OK, a bit of an exaggeration). This will heat a moon even if it is outside of the solar system's main habitable zone. This increases the areas in a solar system where life can form.

So when we are looking for extrasolar life, we need to look at large moons as well as planets. Right now our technology allows us to detect only large gas giants. However, rapid advances will (possibly as early as this year) allow the ability to detect terrestrial planets. The ability to detect water planets is on the horizon as well. I can not say if the ability to detect habitable moons will exist in the near future, but I would not rule it out.

Notes:

1. Many chemicals are found in space, including interstellar gas clouds of sugar and of beer!

References:

Browne, Malcom W. "Alcohol-Laden Cloud Holds the Story of a Star." New York Times. 30 May 1995. 5 February 2008. <http://query.nytimes.com/gst/fullpage.html?res=990CE7D81531F933A05756C0A963958260>.

Scharf, Caleb A. “The potential for tidally heated icy and temperate moons around exoplanets.” Astrophysical Journal. 648 (2006) 1196-1205.

Amoebic Intelligence

© www.microscope-microscope.org

I promise we will return to preliminary speculative discussions of alien technology soon but this topic in Physics News caught my eye due to previous contemplations on the importance of intelligence to survival - if intelligence is a natural and expected result of evolution, if it is a natural tendency, a natural law in our Universal Biology then the likelihood of other intelligent advanced beings existing in the universe increases.

"Amoebas Anticipate Climate Change," the Physics News Update reports January 3. In it, there is indication of a extremely rudimentary intelligence in these single celled creatures. For the presence of intelligence, even a very rudimentary one, to exist in the amoeba may indicate that intelligence is common - and that there is a strong evolutionary pressure, if you will, for it to arise and evolve.

Which also shows that Drake's original calculation for fi (percent of habited planets where intelligent life evolves) in his Drake Equation may be too low (he calculated 1%).

PHYSICS NEWS UPDATE

The American Institute of Physics Bulletin of Physics News

Number 852 January 3, 2008 www.aip.org/pnu

by Phillip F. Schewe and Jason S. Bardi

AMOEBAS ANTICIPATE CLIMATE CHANGE A new experiment shows that amoebas will slow their motion in synch with periodic adverse changes in their environment, and will, as if in anticipation, even slow down when the adverse condition is not delivered. A team of scientists from Hokkaido University and the ATR Wave Engineering Laboratories in Japan cultured the single-celled slime mold Physarum polycephalum (a member of the amoeba clan) in a bed of oat flakes on agar. Every ten minutes the air was made slightly cooler and drier, which had the effect of slowing the movement of the amoebas down a narrow lane. Then more favorable air would be restored and the motion continued as before. After several cycles, the amoebas slowed even when the adverse conditions did not materialize. Later still, when the organisms have been tricked into anticipating impending climate change several times, they refrain from slowing without an actual change in conditions. One of the researchers, Toshiyuki Nakagaki from Hokkaido (nakagaki@es.hokudai.ac.jp), cautions that amoebas do not have a brain and that this is not example of classic *Pavlovian* conditioned response behavior. Nevertheless, it might represent more evidence for a primitive sensitivity or *intelligence* based on the dynamic behavior of the tubular structures deployed by the amoeba. (Saigusa et al., Physical Review Letters, 11 January 2008; journalists can obtain the article from www.aip.org/physnews/select)

The above quoted article "is provided free of charge as a way of broadly disseminating information about physics and physicists. For that reason, you are free to post it, if you like, where others can read it, providing only that you credit AIP."

Introduction to The Drake Equation

The Drake Equation

I really shouldn't go on without at least an introductory mention of the famous (and controversial) Drake Equation created by Dr. Frank Drake in 1960.

Dr. Drake's equation is a tool for estimating the number of intelligent advanced civilizations presently in the Milky Way galaxy that we would theoretically be able to communicate with.

The Drake Equation is

N=(R)(fp)(ne)(fl)(fi)(fc)(L)

where N is the number of civilizations we can communicate with at this time in the galaxy, and where:

• R = average star formation rate (10/yr)
  
• fp = percent of those with planetary systems (50%)
  
• ne = average number of planets that can potentially support life per star with planetary systems(2)
  
• fl = percent of the above planets where life actually begins - life started on Earth very quickly, water and the complex organic building blocks for life are common in the universe (100%)
  
• fi = percent of habited planets where intelligent life evolves (1%)
  
• fc = percent of intelligent life that develop communication technology capable of transmitting into space(1%)
  
• L = lifetime of all such civilizations on a particular planet - civilizations may collapse and rise again, or nearly wipe themselves out and the survivors rebuild (10,000 years)

The values in the parentheses are Dr. Drake's estimations. Using Dr. Drake's original values we arrive at N=10. As new data rolls with increasing frequency, these values tend to change. For more discussion see below. 

Assumptions

• Liquid water is required for life, 
• type M stars are too cool, 
• type O and B stars are too short lived, 
• life will develop if given a chance, 
• developing intelligence gives a survival edge, 
• and technologically advanced civilizations do not consistently prematurely destroy themselves because of their technological advances (global atomic war, for instance).

R, fi, and ne Discussion

As mentioned above, as new data rolls with increasing frequency, these values tend to change. Presently, the value for R is thought to be 6 per year. And, as mentioned a few times before in other postings in this blog, we are increasingly discovering certain intelligent traits first thought to be reserved just for humans cropping up in other animals: birds that make and keep tools, ferrets purposefully lying, and dogs mapping language to mention just a few. This indicate that the first estimation for fi (a mere 1%) may be too low.

If, however, sentient, intelligent life is so rare that we are the only one in the galaxy, or even the universe, then the vale for fi may be infinitesimally small. But, if we are the average result of habitable planetary system, and if life is found to have once existed on Mars, and to exist on Europa, then the value for fi becomes 33% (and ne becomes 3). That life formed quickly on Earth, a wet rock orbiting an average star in a nondescript part of the galaxy, then maybe, just maybe, it can form in extrasolar systems as well.

Calculate N for Yourself

See the Drake Equation Calculator on the right. Type in your own values for the variables in the Drake Equation to calculate N.

Habitable Zones and Habitable "Hot Spots"

Personally, I believe the habitable zone estimates are a bit conservative. For instance, Jupiter's moon Europa, despite being outside of our solar system's Habitable Zone, may have liquid water beneath its icy surface, and many scientists feel that Europa could support life. Thus, Habitable Zones could actually be larger, or a system could have Habitable "Hot Spots" (which includes not only planets, but large moons as well) in addition to its Habitable Zone . Maybe even an occasional type M stars could have habitable planet (see Color of Life for some discussion about life in a M class star system).

In addition, the equation does not take into account life that is spread to other planets by advanced civilizations (whether unintentionally from exploration or purposefully from terraforming). And finally, life is constantly surprising us with its great diversity here on Earth - our definition of what is life may need to be expanded.

Additional Drake Equation Posts.


Reference:

Schilling, Govert and Alan. M. MacRobert. "The Chance of Finding Aliens." SETI: Searching for Life. Sky and Telescope Magazine. 15 January 2008. <http://www.skyandtelescope.com/resources/seti/3304541.html>


Image credit: © Lynette Cook