"If the Earth were just a little bit further from or closer to the Sun, we would all freeze or burn"
I'm sure we've all heard this argument by theists employing the fine-tuning argument. Are you aware, however, of exactly how much this "little bit" really is? Theists would have us think that the slightest change in the distance would have drastic implications for survivability. But that is actually not the case.
We are probably all familiar with the factoid that the Earth is 93 million miles from the Sun. But this is not a fixed distance, but an average distance. The Earth's orbit around the Sun is not perfectly circular but elliptical. Earth's distance from the Sun varies depending on the time of the year. When the Earth is closest to the Sun in early January (at its Perihelion) it is 91.4 million miles away from it. When the Earth is furthest from the Sun in early July (at its Aphelion) it is 94.5 million miles away from it. So during the course of a year, the Earth's distance from the Sun varies by over 3 million miles!
To put that 3 million miles into perspective, the Moon is a little over 238,000 miles away. Now imagine travelling more than 12 times the distance to the Moon. That great distance is the extent to which Earth's distance from the Sun varies - with minimal affects to the temperature on Earth. Mile for mile, the Earth's tilt actually has greater effect on temperature variation than the planet's distance from the Sun. And we can even go into the very important role that Earth's rotation and atmosphere plays in maintaining habitable temperatures.
Of course, the Earth's distance from the Sun is important. My point is that the notion that this distance is perfectly fine tuned and the slightest change would have dire consequences, is simply not true. There would have to be significant change in distance to make life on Earth impossible. The 3 million mile variance does not even represent the full extent of Earth's habitable zone. I'm willing to bet that if the distance were varied by as much as 6 million miles, life on Earth would still be possible although the temperatures would be less comfortable.
Yes I find the finely tuned universe factoid to be hilarious. The same people fail to grasp the fact the finely tuned earth will one day be swallowed up by the finely tuned Sun when it becomes a finely tuned red giant.
Yes, and who can get forget all those finely tuned mass extinctions.
There are many factors that would make a planet or moon able to support life, but the most basic factor is the body having liquid water available.
The habitable zone is the orbital region around a star in which a body can possess liquid water on its surface and possibly support life. Liquid water is essential to all life on earth, so the definition of a habitable zone is based on the idea that extraterrestrial life would share that same requirement.
Distance from the star primarily determines the habitable zone, but there are other factors in having liquid water. The reflectivity of the planet or moon, its green-house gases, internal heat of the mass, volcanic activity- these are factors that increase the probability that liquid water may be present on the surface. It's also possible that liquid water is present in some subsurface way to allow for some kind of simple life. It is accepted that Jupiter's moon, Europa has a liquid ocean below the surface. So Europa may be outside of the scientific habitable zone, but it still might support life.
Life on earth is special. Being in the habitable zone and having a large moon and all kinds of other factors have aided in the existence of "Life as we know it." But life-as-we-don't-know-it may very well have evolved here if the factors were different.
Many scientists accept that the habitable zone for our sun, based on an earth-type planet with green house gases can be from 0.9 to 1.5 times the actual distance of earth to the sun. [1.5] is quite a bit.
The changing conditions of the star effect the zone too. Venus may well have been very "habitable" when the sun was younger and Mars (and other outer bodies) may be very "habitable" a few billion years from now as the sun gets older.
Back when I was still in, I often had fun with this one by correcting JWs who brought it up in a conversation...
...I told them that the Earth didn't orbit at so much a fixed distance as it followed a "corridor" that had measurable cyclic variations, which incidentally, were what contributed to the Ice Ages.
If they brought up any objections to the possibility of Ice Ages, I'd simply ask, "well, then why else would wooly mammoths have the thickest fur of any known land animal?"
Seeing the "jeezus-I-never-thought-of-that" look on their faces never got old.
Liquid water planets can be produced in many ways, one would be to have a planet closer to a cooler, smaller, slower hydrogen fusing star. that would be even a finer tuning for wt purposes, "everlasting " life would be longer than just another measly 4 billion years. and, are we not lucky, we on the northern hemisphere, as Island Man pointed out ,-- that the sun is closer in January than July. Many factors would go to live in a Goldilocks zone, not as rare as we might think.
The details about how close or how far, is not all that important. The important thing is to understand that the only reason why the earth seems to be at the perfect position, is because if it wasn't, it probably would have ceased to exist.
To illustrate, if you have a table with a heater at each end, where the only cool place is exactly in the middle, i can throw a bucket full of chocolate squares on the table, and if one lands in the middle, it will survive, the others will melt. This doesn't mean that someone put that one chocolate in the perfect place.
Good point, redvip2000. Also, there have been many recent discoveries of planets orbiting stars within the habitable zone. So the Earth is really not that special in this regard.
Just imagine if life has evolved in the sub-surface oceans of Europa - it must be marveling at how finely tuned its environment was just for it - this life wouldn't be able to survive if not for Europa's oceans. The frozen surface of the ocean keeps the life forms from venturing too close to the surface where they'd be killed by the radiation from Jupiter. Europa is even just the right distance from Jupiter that tidal forces keep the internal temperature perfect without tearing the moon apart. These life forms would surely think that the odds of another planet existing with these fine-tuned conditions would be astronomical. Surely Europa was created just for them!
“This is rather as if you imagine a puddle waking up one morning and thinking, 'This is an interesting world I find myself in — an interesting hole I find myself in — fits me rather neatly, doesn't it? In fact it fits me staggeringly well, must have been made to have me in it!' This is such a powerful idea that as the sun rises in the sky and the air heats up and as, gradually, the puddle gets smaller and smaller, frantically hanging on to the notion that everything's going to be alright, because this world was meant to have him in it, was built to have him in it; so the moment he disappears catches him rather by surprise. I think this may be something we need to be on the watch out for.”