Would life not exist on Earth if it was one kilometer closer to, or farther from, the sun?

A lot of my friends (especially creationist ones) tell me that if planet earth was one kilometer closer to the sun, it would heat up too much and life wouldn't exist. On the other hand, if planet earth was one kilometer farther from the sun, it would freeze up and life wouldn't be able to survive, either.

Of course, my answer was that life developed and adapted to earth's conditions and not the other way around. I was curious, however, if their claim about earth's position is correct.

Example sources of claim: Yahoo Answers question, Facebook linked by Fundies Say the Darndest Things, Facebook post by Aperture Science, Blog debunking the claim, Someone citing their priest, and others.

• The side of the Earth facing the sun (the day side) is hundreds of kilometres closer to the sun than the side facing away from it (the night side). People don't start freezing to death at sunset. Common sense tells that this claim is very very dubious for just that reason alone. Mar 4, 2015 at 13:13
• I'm a creationist, but the "1 kilometer" thing sounds like either you misheard them, or they misunderstood distances. Since the average distance from the earth to sun varies by over 3 million miles, a kilometer wouldn't matter. Mar 6, 2015 at 19:08
• Basically, their numbers are off but that does not change their argument. There is a moderately small distance that the earth could be moved that would of made life impossible as far as we know. That is our absolute best guess. That there is this "Goldilocks zone" that is not that big. We are in it, and if were were not we would almost certainty not be here. But then if life had not developed on earth there would be no one to make the argument. All life by definition sprang up in conditions favorable for life, regardless or a creator god or not. Mar 9, 2015 at 15:30
• It is like saying. What are the chances of me being me. There is like a 1/10^999999999999999999999999999 chance that I was born with this exact face and these exact fingerprints. My birth must of been influenced by someone for this unlikely event to have occurred. Mar 9, 2015 at 15:31
• @JonathonWisnoski - that's called "Anthropic Principle" Mar 18, 2015 at 18:09

Their claim is incorrect. On an astronomical scale, one kilometer is a very small value. In fact, Earth's orbit regularly varies by far more than 1km.

According to the NASA's Solar System Exploration website's facts and figures,

Perihelion (closest)

• Metric: 147,098,291 km
• Imperial: 91,402,640 miles
• Scientific Notation: 1.47098 x 108 km (0.983 A.U.)

Aphelion (farthest)

• Metric: 152,098,233 km
• Imperial: 94,509,460 miles
• Scientific Notation: 1.52098 x 108 km (1.017 A.U.)

That is, Earth's distance from the Sun varies by 5 million kilometers during a single year. A change of one kilometer would not be noticeable.

• Does this answer the question Mar 8, 2015 at 0:03
• @Oddthinking Yeah, does it? I can't see from this answer that a small change in average distance would not have the claimed effects after billions of years. The other answer seems better suited to actually answer the question. Mar 9, 2015 at 12:00
• @kutschkem I understood the claim as implying that the distance from the Earth to the Sun was constant. If you read it as being about the average distance, then yes, the other answer addresses it better. However, I doubt that creationists are making an argument about the effects after billions of years. Mar 9, 2015 at 17:35
• You're going to bring facts into evaluating a "common sense/gut feeling" meme? I guess that's one way to go. :D Sep 21, 2016 at 16:16

The Goldilocks zone ("Circumstellar habitable zone") is a real thing:

In astronomy and astrobiology, the circumstellar habitable zone (CHZ), or simply the habitable zone, colloquially known as the Goldilocks zone, is the region around a star within which planetary-mass objects with sufficient atmospheric pressure can support liquid water at their surfaces. The bounds of the CHZ are calculated using the known requirements of Earth's biosphere, its position in the Solar System and the amount of radiant energy it receives from the Sun.

But it's rather more than one kilometre wide:

Estimates for the habitable zone within the Solar System range from 0.725 to 3.0 astronomical units, though arriving at these estimates has been challenging for a variety of reasons. Numerous planetary mass objects orbit within, or close to, this range and as such receive sufficient sunlight to raise temperatures above the freezing point of water. However their atmospheric conditions vary substantially. The aphelion of Venus, for example, touches the inner edge of the zone and while atmospheric pressure at the surface is sufficient for liquid water, a strong greenhouse effect raises surface temperatures to 462 °C (864 °F) at which water can only exist as vapour. The entire orbits of the Moon, Mars, and numerous asteroids also lie within various estimates of the habitable zone.

Converted into kilometers, that's "Estimates for the habitable zone within the Solar System range from about a hundred million to about half a billion kilometres".

In this diagram, dark green is the minimum estimate, light green is the maximum (image source).

And so it's not at all unusual to find planets within that zone:

On November 4, 2013, astronomers reported, based on Kepler space mission data, that there could be as many as 40 billion Earth-sized planets orbiting in the habitable zones of sun-like stars and red dwarf stars within the Milky Way Galaxy. 11 billion of these estimated planets may be orbiting sun-like stars.

So the implied claim that the existence of an Earth-like planet within the habitable zone is unlikely to have occurred anywhere in the universe purely by chance (and therefore is proof of purposeful creation), seems pretty clearly false to me, because there look to be approximately 40 billion counter-examples.

See:

One out of every five sunlike stars in the galaxy has a planet the size of Earth circling it in the Goldilocks zone — not too hot, not too cold — where surface temperatures should be compatible with liquid water, according to a herculean three-year calculation based on data from the Kepler spacecraft by Erik Petigura, a graduate student at the University of California, Berkeley.

We find that 22% of Sun-like stars harbor Earth-size planets orbiting in their habitable zones.

1 in 5 stars like the one at the center of the solar system hosts a planet capable of holding liquid water on its surface and — if it had the right chemical ingredients — supporting life.

One should also remember that our type of life is not the only possible type of life. Perhaps there are other forms of life for which an Earth-like planet would be outside their habitable zone.

Alien Life May Live in Various Habitable Zones, Discovery.com

in the cosmological context there’s no obvious reason why life has to be exclusively dependent on a water-based environment. Life could be so opportunistic and adaptable it may simply work with whatever liquid is at hand. Alternative solvents considered by astrobiologists include dihydrogen (a simple molecule composed of two hydrogen atoms), sulfuric acid, dinitrogen, formamide, and methane, among others.

If so, this antiquates the notion of a narrow habitable zone encircling billions of stars in our galaxy. Depending on your flavor of life, there could be multiple habitable zones around the sun and other stars.

It's even possible that life - our own kind of water-based life - may exist within our own solar system but outside of the 'Goldilocks zone', perhaps getting its energy from sources other than the sun. Jupiter's moon Europa is often considered as a candidate for for life:

Many scientists believe Europa is the best location in our solar system to find existing life. It has a subsurface ocean in contact with rock, an icy surface that mixes with the ocean below, salts on the surface that create an energy gradient, and a source of heat (the flexing that occurs as it gets stretched and squeezed by Jupiter's gravity).

In other words: Europa could have fish.

If they're intelligent fish, perhaps they chat amongst themselves about how they came to live in a place where the conditions for life exist, and whether such a thing could happen by chance or must be a matter of design.