I realize that the earth is in the ‘Goldilocks Zone’ for our Sun, but what are the inner and outer limits of that zone?
We are about 93 million miles away from the Sun. Venus is 67 million miles and Mars is 141 millions miles away.
If the earth was only 80 million miles away, or was 120 millions miles away would we still be in the Goldilocks zone that would allow for carbon-based life as we know it?
How broad/narrow is the Goldilocks Zone in our solar system?
My daughter (5th grade) was taught in school that if our orbit was even 1 inch different then life as we know it would be impossible.
Doesn’t sound even remotely credible to me (I mean, doesn’t our orbit vary somewhat anyway, possibly by hundreds or thousands of miles?.. it’s not like the planet is on rails…) but I haven’t had any luck in convincing her that the teacher is wrong (I’m just a parent after all, what do I know).
Not sure if the teacher literally believes this or is simplifying things for them (much like we were taught that the Civil War was about ending slavery, when really there was much more to it, but that would suffice for a time.)
I will be watching this thread with interest.
There are many estimates (see here)- a rough mean of these might be roughly from the orbit of Venus to just outside the orbit of Mars.
Does your daughter by chance go to a fundamentalist school taught by people with zero accreditation? That’s the kind of belief often espoused by creationists and the like.
In reality, the Earth’s orbit around the Sun is an ellipse, not a perfect circle, and the distance from the Earth to the Sun varies between 152,098,232 km and 147,098,290 km.
As a simple means of contradicting the ludicrous notion that the Earth would fry/freeze if it were an inch off, trying jumping. Note how when you are 3 inches off the ground, you don’t get turned into a crispy critter or a popsicle.
If Earth’s atmosphere and albedo never changed, the Earth would warm about 1°C every 150 million years, due to increasing solar output. Thus, if all else were equal, the Cambrian Period would have been about 3°C cooler than the present.
But it wasn’t! It was about 4°C warmer, due to high levels of greenhouse gases. In other words, smallish differences in the atmosphere can compensate for orbital distance or solar brightness.
In James Lovelock’s famous Gaia hypothesis, a planet teeming with life may have feedback mechanisms maintaining temperature and other parameters suitable for life.
There are many variables and many different ways of estimating what the circumsolar habitable (so-called “Goldilocks”) zone is but the most credible estimates for a planet which can maintain an atmosphere which can sustain liquid water on the surface are between about 0.75 and 1.2 AU (astronomical units, where 1 AU is the average radius of Earth’s orbit), which naturally puts to question the possibility of terraforming Venus or Mars, notwithstanding the exotic technology and energy which would be required for such efforts. Limits for a planet with an Earth-like atmosphere are tighter (often as little as 0.98 to 1.02 AU), but this assumes that the atmospheric composition would be independent of solar incidence, but realistically Earth maintains a degree of non-equilibrium thermodynamic equilibrium which, according to some hypotheses, is mediated by the existence of life itself to maintain habitable (albeit variable) conditions.
Note that liquid water is often assumed to be a necessary precursor to life as a barely polar solvent which can support. This is necessary for life as we are familiar with it, but it is certainly possible to form complex organic molecules in other environments with sufficient energy to allow polymerization and other interactions to develop more sophisticated structure. Spectra from amino acids have even been observed in interstellar space, although whether the environment would be sufficiently stable to initiate and evolve life is questionable.
The claim that a habitable environment could not be sustained if the planet were altered by distances on the order of an inch are absurd on the face. In addition to the orbital eccentricity, normal perturbations due to other planets alter the trajectory of the Earth by substantially more than that (although still tiny fractions of the overall orbital radius).
Stranger
Are these teachers unaware of the shape of an ellipse? Also, that isn’t a simplification; it’s flat out wrong and sounds like some strain of ID rhetoric.
If that were my child, I’d be making inquiry into exactly what the hell my child was being taught.
Thanks everyone. Sounds like there are a number of variables involved but Earth luckily ended up in the middle of the zone.
Note that even that sentence sounds like the ID folks – we hit the jackpot by being created in the perfect place for life..
It is actually the other way around. Life only turns up in those places suited for it.
This is one of the reasons why multiple choice tests can be more difficult for people with more education and intelligence. Little kids memorize factoids. Grad students see a question on the origin of the Civil War and though they know that the common answer is slavery, they know that Johnson (1935) put forth a fairly good argument that conflicts between Northern and Southern church conferences over economic control of dioceses touched off the war when the Southern Baptist Convention encouraged violence to prevent tithes from going to Philadelphia, McDougal, Smith, and Rodriguez (1974) argued that the war was triggered by a strike by the Irish Garment Workers Union who were opposed to slavery because it ensured a supply of cheap non-white labor and thus drove down wages, and Schneider (2013) just published a paper offering a hypothesis of climate change triggering mental illness in John Brown and indirectly causing the war.
(yes, I’m making the examples up)
I’ve heard statements like the “one inch off” made by secular types as well, especially environmentalists who seem to believe that the entire planet is on a razor’s edge and if we make any change at all, we’re all doomed. One such person told me that we needed to limit shuttle launches to make sure we didn’t push the Earth away from the sun…
As far as the original question about the Goldilocks zone, it seems to me that the Goldilocks zone idea is on its way out. Deep sea thermal vents (among other things) on Earth prove that surface temperature and sunlight are not as important to life as we used to think. Heck, it seems like Europa might be a better bet for life than Mars.
I’m with you. If you look at earth, there is an organism in almost every ecological niche from Mt Everest to the sea vents on the bottom of the ocean and from Antarctica to the equatorial regions.