From The University Corporation for Atmospheric Research:
The Goldilocks Principle can be summed up neatly as "Venus is too hot, Mars is too cold, and Earth is just right." The fact that Earth has an average surface temperature comfortably between the boiling point and freezing point of water, and thus is suitable for our sort of life, cannot be explained by simply suggesting that our planet orbits at just the right distance from the sun to absorb just the right amount of solar radiation.
Our moderate temperatures are also the result of having just the right kind of atmosphere. A Venus-type atmosphere would produce hellish, Venus-like conditions on our planet; a Mars atmosphere would leave us shivering in a Martian-type deep freeze.
Instead, parts of our atmosphere act as an insulating blanket of just the right thickness, trapping sufficient solar energy to keep the global average temperature in a pleasant range. The Martian blanket is too thin, and the Venusian blanket is way too thick! The 'blanket' here is a collection of atmospheric gases called 'greenhouse gases' based on the idea that the gases also 'trap' heat like the glass walls of a greenhouse do.
*ahem*
From elsewhere on their site:
Venus - average distance from Sun 67 million miles
Earth - average distance from Sun 93 million miles
Mars - average distance from Sun 226 million miles
As the intensity of light received from an object is inversely proportional to the square of the distance, it'd be reasonable to expect the Sun's rays on Venus to be 193% as intensive as on Earth, and on Mars to be only be 17% as intensive on Earth. Which might have something to do with the temperature differences.
*/ahem*
What detracts from my argument is that the Moon's average temperature is about -36 C, 50 C colder than Earth*, despite it being the same average distance from the Sun, which I'd put down to a mixture of the Moon being paler in colour (so reflects more light) and not having a giant molten iron core, as well as it not having an atmosphere.
UPDATE: further to comments to this post, I have done a bit more reading and wish to retract and re-write that last paragraph, which I will cover in a later post.
* 21 C warmer than Mars, despite having no atmosphere at all.
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13 comments:
I really don't see what the problem is with that global warming...
They say we're running out of oil.
Coal is now a banned substance.
We've burnt down most of the rain forests by now.
Pollution and overfishing means the oceans are full of CO2 eating blue/green algae.
Gormless Brown has tackled the causes of over gritting, thereby allowing the vast UK snow-fields to reflect enormous quantities of evil sunlight back into space.
The mass installation of nice but dim CFLs has resulted in great numbers of our old folk falling down the stairs; ending their wanton use of one bar electric fires, electric blankets and hot water bottles.
So, as you can see from just these small examples; global warming is able to self correct itself. We really don't need to worry about it.
And if all else fails and it gets a little hot in the UK, we can switch on all those giant fans they've built in the countryside to keep us cool.
Next week: Solving the Palestinian problem.
Now come on! We all know that the moon is made of cheese. Even Wallace & Gromit know that. And that NASA faked all the 'moon landings'. Clearly a moon mde of cheese is not going to have an atmosphere anyone would ever want try and breathe.
Do you think there are any other earths out there?
JP, I actually laughed at that. Does that make me a bad person?
L, maybe so, but highly reflective cheese at sub-zero temperature.
JH, yes of course, the odds say so. Will we ever know for sure? Nope. Is it relevant to anything? Nope.
The possibility of life on Earth being known to aliens cannot be discounted.
Speculation may occur huge distances away from us, upon the bizarre forms life must take to survive the climate.
JP. First class.
Hello, there is something about a petition which could interest you in the top right-hand corner at the following address: http://eternal-cartesian.blogspot.com/ . Cordially
The Sun has got warmer over the last few billion years. The early Earth had a CO2 atmosphere. It is an interesting piece of luckiness that not only are we well placed for life but that, even though the reqirements have changed we have always been well placed.
Professor Lovelock thinks this is because the Earth is deliberately doing this (Gaia hypothesis). I think it means intelligent life is going to be awfully rare in the universe.
Neil crang: I agree, intelligent life will be rare in the universe, if the population of the Earth is anything to go on.
The last sentence of goldilocks is crap.
You've correctly identified the Moon as the perfect counter-example to your argument.
btw. There was a 1-hour program broadcast by a San Diego TV station last night. It gives a run-down of the non-science and chicanery surrounding the AGW scam. Reasonably non-technical ( although I'm not the best judge of that). It's on their site as 5 flash videos. The first is so-so. The others are pretty good. Number 4 could be an eye-opener to those who don't know the story. The people involved are sound - although expect the attack dogs to be at them even as I write.
It's here
http://www.kusi.com/weather/colemanscorner/81583352.html
VFTS, which sentence do you mean, exactly?
The moon is not paler than the Earth and does not reflect more light. It has an albedo (reflectivity) of 7% compareed to the Eraths 30-40% (depending on cloud cover). Close up, moondust is very dark, like charcoal.
Late to the party again. I see you've already covered what would have been my answer to your last question.
It's the lack of atmosphere that brings about the low surface temp on the moon when the sun's not shining on it.
Pressure at Mars' surface is about 0.006 times Earth's. At Venus' surface is about 92 times Earth. That plus the inverse square makes the big difference between the 3 planets.
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