Searching for the Goldilocks Planet

The first That’s a Fact video for November is called Goldilocks Planet. The theme is, for the most part, the same as was explored last weekend – while the video starts off on the subject of exoplanets it quickly finds itself in “Earth is special” territory.

Alpha Centauri Bb, an uninhabitable Earth-sized planet

Scientists have been looking for the Goldilocks planet for years. The name obviously comes from the popular Goldilocks fairytale. Now, the Goldilocks idea – much like the fairytale – is all about finding a planet that’s just right for life. But finding the right planet is harder than you might think, especially when you think about how special the Earth is.

Artist impression of Kepler-22bDepending on how stringent you intend to be the detection of a “goldilocks planet” could indeed be quite difficult, but this has less to do with “how special the Earth is” than it does our presently-inadequate methods and technology. You will remember the recent discovery of the approximately earth-sized planet Alpha Centauri Bb, the nearest exoplanet to the solar system. It was found because it orbits quite close to its parent star, an important part of of most planetary detection systems (especially for smaller bodies). If there was a similar planet located in a more habitable region further out in that system we wouldn’t actually know.

If we’re prepared to accept a planet that orbits within the habitable zone (the usual “goldilocks” definition) but is a fair bit heavier than Earth (going against the definition apparently used here by the ICR) then we already have such a planet: Kepler-22b. We will no doubt find lighter versions in the future.

Earth is the only known planet in our universe that can support life.

We have only searched an extremely small portion of the galaxy, evenThis is debatable. Certainly, Earth is the only planet known to support life, but it may well be possible that certain extremophiles (the bane of fine-tuning arguments everywhere) could be successfully introduced to certain extraterrestrial habitats within our solar system. We have no data supporting or denying the existence of “life as we know it” on the handful of planets that come close to the conditions that could support it. The phrase “only known planet in our universe” implies a great deal more negative evidence than we actually have, especially as we are yet to find a planet outside our own galaxy.

Earth has water, animals, and people – all necessary to support life.

This is by far the strangest line in the whole video. Water, sure, is necessary to support life (again, “as we know it”), but the other two examples are themselves life. What’s more, you could have a planet with life yet lacking animals, not to mention the pesky subgroup known as “humans.” Bacteria, for all their love of water, care little for the struggles of multicellular life.

Earth is just the right distance from the Sun. If we were any closer it’d be too hot. If we were any further we’d be freezing.

This is the “habitable zone” requirement, but the zone is fairly vast. Mars and Venus are sometimes said to be within or on the edge of the zone, and there is quite a bit of room to move while remaining within it.

The Earth also has just enough gravity to support an atmosphere, and yet not so much as to crush us.

Again, there would be plenty of room for variation in this condition also. We can survive accelerations several times that of Earth gravity, and we have the added aspect that we are evolved to survive in the conditions that we find ourselves in – not some ideal world that the Earth by chance conforms to.

Take any other planet. Mars has a very thin, unbreathable atmosphere of carbon dioxide.

The “any other planets” are, of course, merely the other rocky planets of the inner solar system.

Venus has a thick, crushing atmosphere with clouds of sulphuric acid.

I find it funny that the sulphuric acid is the part that keeps getting seized upon. Mars, after all, has (water) ice clouds. Venus, meanwhile, has an atmosphere made even more of carbon dioxide than Mars does, and the pressure (a little less than 100 times Earth’s at the base, but perfectly tolerable at a certain height) is really the least of your worries.

And Mercury is just way too hot.

Indeed, but that’s simply because it’s so close to the Sun.

Not too hot, and not too cold. Not too heavy, or too light, but just right for life. As created by a loving God.

And, as everyone knows, omnipotent dieties are utterly incapable of creating life wherever they like. Case closed, right?

2 thoughts on “Searching for the Goldilocks Planet

  1. I did a rough calculation which suggested that the habitable zone/goldilocks zone for our solar system is quite wide, say at least 55 million miles wide – stretching from partway to the mean distance from the Sun of Venus to almost as far as the mean distance from the Sun or Mars; some think the zone can be extended beyond Mars (Mars may once have harboured microbial life).
    On the other hand, the role of Earth’s moon is also important in allowing life to take a hold here.


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