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NASA Ames Research Center

Alien Life Threat Scale
Larry W. Waterfield
February, 2011


These are exciting times, with the discovery of hundreds of new exo- planets around distant stars. Some of these planets may be earth-like, with moderate temperatures, liquid water and possibly even life.

Now may also be the time to listen again to the admonitions of those who urge caution in seeking out possible alien intelligence:

“Across the gulf of space, minds that are to our minds as ours are to those of beasts that perish, intellects vast and cool and unsympathetic, regarded this earth with envious eyes, and slowly and surely drew their plans against us.”

--H.G. Wells

“If alien life visits us, the outcome would be much as when Columbus landed in America, which didn’t turn out well for Native Americans.”

--Stephen Hawking

With these cautions in mind, it might be timely to propose a scale for evaluating alien life forms in light of their potential threat to humanity. This would be a follow-up to the famous Drake Equation that attempts to predict the likelihood and prevalence of life on other worlds. That equation factors in time for development, prevalence of planets in a livable zone, and many other variables—some of which are only now being added to the equation.

Here is one attempt to develop a “threat” scale for evaluating alien life forms. It is meant to be a kind of thought provoker, but it has a serious intent. Someday it will come in handy. With tongue in cheek, I have dubbed it the Scale for Evaluating Possible Threats from Alien Life Forms, or more simply, The Alien Life Threat Scale (ALTS.)

The Alien Threat Level, with the lower number corresponding to the higher threat.
(The ALTS.)

Level 1: Intelligent beings, highly advanced, possibly war-like or aggressive,
                  with an unknown or unfavorable moral or ethical outlook.

Level 2: Intelligent beings, technically advanced, without indications of
                  aggression or an unfavorable moral or ethical outlook.

Level 3: Intelligent beings, primitive or lower development, with an unknown moral system.

Level 4: Intelligent beings, primitive development, non-hostile,
                  with a generally peaceful moral outlook.

Level 5: Life forms, without intelligence or advancement, and
                  presenting a zero or negligible threat.

I mention Stephen Hawking because he has famously cautioned that we might well be advised to avoid contact because intelligent alien life forms might well be aggressive, war-like and seeking Earth’s abundant resources. He likened them to nomadic marauders who had exhausted the resources of their home planet.

Good alien versus bad alien is a theme played out over and over in the popular culture, on TV, in books and films. It is a staple of science fiction. There are examples of both camps.

Alien Life Threat Scale: Level 5
Alien Life Threat Scale: Level 5

Examples of “bad aliens” show up in the writings of H.G. Wells, notably The War of the Worlds; in the stories of Rod Serling, in which humans wind up as alien hors-d’oeuvres; in stories and films such as The Thing from Another World; Independence Day; Invasion of the Body Snatchers, and numerous others.

“The good alien” can be found in Carl Sagan’s Contact, and Stephen Spielberg’s E.T.: The Extra-Terrestrial and Close Encounters of the Third Kind.

Sometimes the aliens react according to how humans react to them. An example is the film, The Day the Earth Stood Still. The visitors are forced to defend themselves.

The universe may well be chock full of life, including intelligent life. Contact is another matter. We are in our little valley, walled off from other valleys by vast cordilleras of space-time. We send out messages and search for messages. Can we trust any message we might receive? An alien is not likely to say, “We’re coming to gobble up your planet.”

There will come a time when we will have to consider leaving the Earth.
The evolution of the sun, with its slow increase in heat, will render the Earth uninhabitable at some point.

When we venture forth in search of a new “Goldilocks” planet, not too hot or too cold,
then other beings may view us with caution.
If they have a similar Threat Scale, we’ll rank as Level 2, and unfortunately maybe even Level 1.