… or is it? An interesting effect comes into play when one considers:
Asymmetries of water/land in north (60% water) vs. south (80% water) hemispheres
Water absorbs and releases heat more slowly than land.
Total effect on global Climate

ok, now given these effects… I have no clue what the effects will be.

The primary source than I’m looking for is the unredacted Facebook page, or the name of the real people involved in the situation, not some 3rd or 4th level screen shot. That seems like something that is made up for a joke. There is nothing real about it except the appearance, and appearances can be deceiving even when they appear to support a particular viewpoint. PZ wants theists to appear stupid, so he picks up on a screenshot that he likes and treats it like fact. His article is just as flawed factually as the straw man screenshot that someone has set up. Did he check to see whether the screenshot was real? He never says that he did, and he doesn’t reference any real primary source. But all his congregation said, “Amen!” Bad science.

Still waiting for someone to reproduce the original Facebook source (page location or person).

Glad you recognized I wasn’t commenting on policemen but on seasons with Matt.

http://m.wolframalpha.com/input/?i=earth%20Perihelion%201844

Seems vaguely familiar from somewhere – maybe?

@53. chris j. :

people can easily jump to the conclusion that the earth is in exactly the right place, and that there is no margin for error, when in fact the zone is many millions of km wide, and depending on whom you ask, may include Venus and Mars as well.

Don’t forget Europa either!

Possibly Enceladus and Mars still – the main problem with Mars being its low mass rather than its orbital position or so I gather.

It has been speculated that Venus may have life in certain cloud layers (read Ben Bova’s eponymous novel) and the same also goes for the gas giants with Clarke postulating living creatures floating inside Jupiter as well as Europa in the Space Odyssey novels. Scientists (& SF writers) have speculated about life on Titan and Enceladus and inside comets and even in deep space itself so ..? Well, there’s a lot of ideas and guesswork and little clear evidence in my understanding of things here.

I think our current level of knowledge is insufficent to really determine whether the notion of a Habitable Zone (HZ) is all that valid or not. Life may or may not be like us & like we imagine it might be.

first, the “few thousand miles between burning and freezing” part is clearly the result of reading too much into the “goldilocks zone” where the solar radiation the earth receives is “just right.” people can easily jump to the conclusion that the earth is in exactly the right place, and that there is no margin for error, when in fact the zone is many millions of km wide, and depending on whom you ask, may include venus and mars as well.

second, many global warming denialists claim that the recent warming trend can be attributed to increased solar output, writing off anthropogenic sources of CO2 and other GHGs. but they can’t account for this periodic shift in the amount of sunlight we receive, meaning that the composition of our atmosphere is vastly more significant than the relative quantity of light we get from the sun, and any variations in that quantity.

What a lovely way to start the first working day of the new year!

Mother Sun holds the baby Earth
Close with her loving potion.
To explain it all, for what it’s worth -
It’s nought but relative emotion.

Of course he knows better. You might pardon me for re-emphasizing it…because the Good Doctor takes another 7 paragraphs to justify the statement in his opening paragraph, “every moment since then [July], our planet has edged closer to the nearest star in the Universe, approaching it at over 1100 kilometers per hour, 27,500 km/day, 800,000 km every month”.

“Every moment since then…” That is just not true. Unfortunately, by the time he does get around to it, he conflates the rate at which we approached the Sun since last July with our much swifter tangential (orbital) velocity AROUND the Sun at perihelion, which is not directly relevant to the issue. The rest of that paragraph you cite continues with this final sentence: “The exact speed changes, because at perihelion, we’re closer to the Sun and feel its gravity a bit more strongly, so our speed AROUND the Sun is a bit faster than at aphelion.” [Emphasis mine]. That doesn’t address the RADIAL speed component of the Earth’s orbital motion (strictly toward and away from the Sun) over the course of the year.

Nobody needs to provide any “exact math” featuring the calculus of orbital mechanics (with “all the little variables” as you put it) to succeed in accurately characterizing a general concept. But Phil introduced a point up front then dropped the ball when he had an opportunity to fix it: that the AVERAGE (which he “estimated very simply”) is constant (“Every moment since then…”) is wrong gets a little daylight (“The exact speed changes…”) but then he muddies the radial velocity issue with orbital velocity (“…because at perihelion, we’re closer to the Sun and feel its gravity a bit more strongly, so our speed around the Sun is a bit faster than at aphelion”) and goes on to say:

“Together, the tangential and radial velocities add up to gives us our overall orbital velocity, which changes with distance from the Sun. In fact, at perihelion today we’ll be moving around the Sun at 30.1 km/sec, and at aphelion in July that will have slowed to about 29.6 km/sec. That’s a change of about 1.7%…”

- without ever explaining how the Earth manages to snap instantly in RADIAL velocity by over 2200 km/hour every July and January…as explicitly implied by his opening paragraph.

There isn’t just one point in his post, which is what I like about many of Phil’s posts, no matter how long they are (and many are in fact longer). Instead, he goes on to another point he wants to make, leaving the previous one writhing with a wound in need of proper treatment. It wouldn’t have been at all hard to dispense with the opening phrase in that second sentence of this post: “Every moment since then…” and adding to its tail end, “…on average”. That would have REDUCED his post by 2 words AND satisfied accuracy, which I am sure Phil loves more than dramatic turns of phrase. (Many pardons for raising the issue, Phil).

For the potential distant future problems with Mercury – note from there :

“…the good news: there’s only about a 1 percent chance that Mercury will go crazy before the Sun bloats into a red giant billions of years from now. “If you’re an optimist,” says Laughlin, “then you say the glass is 99 percent full.”

This link gives one source :

http://www.space.com/scienceastronomy/solarsystem/death_of_earth_000224.html

on Earth moving out as the Sun’s stature shrinks. Although it mentions that :

“If the sun loses mass before it gets too big, then Earth moves into a larger orbit and escapes,” Willson told SPACE.com. “The sun would need to lose 20 percent of its mass earlier in its evolution, and this is not what we expect to happen.”

Also, elsewhere it has been suggested that the Earth may raise a tidal bulge in the red giant Sun’s surface causing our world to eventually spiral inwards to destruction & there still seems to be some uncertainty over our globe’s eventual fate.

Also here :

http://www.space.com/scienceastronomy/planetearth/earth_move_010207.html

is the space.com article mentioned about us moving Earth further from the swelling Sun. Talk about ambitious plans – & forward thinking, long term ones at that!

Then again, Anaxagoras (or was it Pythagoras? Or another classical Hellenic thinker?) once famously (sorta) suggested it first :

“Give me a lever long enough and I’ll move the Earth!”*

* In Ancient Greek naturally & also may not be exact quote. (Typing from memory only.)

.. I would say this ,the Earth has been in this orbit since it formed 4.5 billon years ago and it will most likely be in it until its end.

[Pedant mode on] Actually, that’s not quite accurate. As our Sun loses mass especially towards the end of its main-sequence life and into its red giant phase we have good reason to think that Earth’s orbit will probably shift outwards.

There’s also the slim (~1% or so if memory serves) chance that our inner solar system planets incl. Earth could have their orbits destabilised and perhaps even end up colliding or being ejected because of Mercury & Venus chaotically interacting gravitationally.

That’s assuming we don’t move it further out of harm’s way ourselves as suggested in a space-dot-com article.

Off Topic : I saw a fireball last night while observing.

Excellent! Nothing quite like a decent fireball in the night. Love it when I look up at just the right time to observe that.

@33. Bill Nettles : D’oh! Having just checked (too late natch) I’ve realised that while I’d mistakenly thought you were responding to the confrontation with the police officer by (#22.) Pete Jackson, you were *really* responding to a confrontation over where our Sun / Earth is in season by (#23.) Matt instead. Mea culpa. My apologies.

[Puts it down to my brain still being affected by the traditional New Year's Day hangover & still not working right yet. ]

I took a lighter approach in writing about the perihelion. Launched my Sun appreciation art campaign today.

Folks may be interested, I’d love to hear feedback: http://SUNWORSHIP.info/2011/perihelion/