Question on Black Body Physics

[Grand Moff Yenchin]

Recently I was in a debate where a creationist proposed an ice shell with two holes (on the opposite sides) surrounding 400Km above the earth as the source of water for Noah's flood.

The radius of the holes he proposed was about 650Km. The thickness of the ice was about 2Km. One hole was always facing the sun.

Besides most problems that were easily pointed out, there were these odd claims of this proposal which kind of made me curious on how good they were.

1. The ice shell with the holes will become a black body. Like the cavity models used in the lab.

2. The ice shell won't melt because since it's a black body, it will be emitting the heat it recieved from the sun. Punching numbers into the Stefan-Boltzmann equation there will be an absolute temperature of 198K.

[kheegster]

1. The ice shell with the holes will become a black body. Like the cavity models used in the lab.

2. The ice shell won't melt because since it's a black body, it will be emitting the heat it recieved from the sun. Punching numbers into the Stefan-Boltzmann equation there will be an absolute temperature of 198K.

What a brilliant case of completely misunderstanding an analogy and applying to justify stupidity. The cavity thought experiment states that the apparent radiation emitted from the cavity is approximately a black-body, not the object as a whole. So a gigantic ice shell would most certainly melt very quickly, cavity or no cavity.

That's of course ignoring the question of how the bloody thing got there in the first place.

[Lord Zentei]

Not to mention the problem of where the water went after it receded. And if the shell surrounded the Earth, how did people see the Moon and stars? How did the shell maintain its structural integrity?

And of course, God must have known in advance that he was going to flood the Earth when he created it. But then, he's God, right?

[Beowulf]

Gravitationally, the ice shell would be unstable in movement except in the direction of the ice holes. Net result: ice shell crashes into earth, resulting in massive climatological changes (extinction level event, most likely). (Just in case this wasn't mentioned).

[Grand Moff Yenchin]

What a brilliant case of completely misunderstanding an analogy and applying to justify stupidity. The cavity thought experiment states that the apparent radiation emitted from the cavity is approximately a black-body, not the object as a whole. So a gigantic ice shell would most certainly melt very quickly, cavity or no cavity.

That's of course ignoring the question of how the bloody thing got there in the first place.

LOL that means without regarding the shell melting, Earth is sealed up in a 198K environment? That's a "cool" place. As for how the bloody thing got there, I believe this stupid proposal is similar to what the "Vapor Canopy" people say: It was created this way. (What a wonderful world...)

Not to mention the problem of where the water went after it receded. And if the shell surrounded the Earth, how did people see the Moon and stars? How did the shell maintain its structural integrity?

Let me share his answers to you guys for laughs:

First question: Most of it went underground, causing land to float on top of it, resulting in plate tectonics. So after the flood mountains rose fiercely. (He tried to dodge the question of water amount by lower mountain heights. Which doesn't help. Since he's a YEC, he needs the mountains to raise thousands of meters in about 1000 years, resulting in massive earthquakes and other disasters.)

As for the second question, this is where the hole comes handy (he thinks). A friend of mine calculated the brightness and pointed out that he will basically need to have about 8 thousand nuclear plants working through the hole to have the brightness of about 1 lumin.

Structural integrity. In short: The moron uses his troll tactics to maintain the integrity.

[Lord Zentei]

Not to mention the problem of where the water went after it receded. And if the shell surrounded the Earth, how did people see the Moon and stars? How did the shell maintain its structural integrity?

Let me share his answers to you guys for laughs:

First question: Most of it went underground, causing land to float on top of it, resulting in plate tectonics. So after the flood mountains rose fiercely. (He tried to dodge the question of water amount by lower mountain heights. Which doesn't help. Since he's a YEC, he needs the mountains to raise thousands of meters in about 1000 years, resulting in massive earthquakes and other disasters.)

How does rock float on water? Seriously, underground water reservoirs only exist because the rock above them is porous. And what's this "mantle" I keep hearing about? How is new crust formed as tectonic plates part if there is just water underneath?

As for the second question, this is where the hole comes handy (he thinks). A friend of mine calculated the brightness and pointed out that he will basically need to have about 8 thousand nuclear plants working through the hole to have the brightness of about 1 lumin.

Huh? I meant that if the hole faces towards the Sun at all times, line of sight to the stars and Moon should be blocked, since the relative positions of the Sun and stars change over the course of the year, and the relative position of the Sun and Moon changes over the course of a day. Unless there are thousands of holes in that ice that are actually capable of moving around as relative to the surface.

Structural integrity. In short: The moron uses his troll tactics to maintain the integrity.

Nothing can penetrate the skull of Ferrous Cranous.

[Grand Moff Yenchin]

Gravitationally, the ice shell would be unstable in movement except in the direction of the ice holes. Net result: ice shell crashes into earth, resulting in massive climatological changes (extinction level event, most likely). (Just in case this wasn't mentioned).

He actually thinks that air buoancy can support the shell. Not to mention that the difference in gravity will "adjust" it.

The funny part? Assuming that air at 400Km high is thick enough and ignoring other factors, simple harmonic motion of this shell caused by this "adjustment" will fuck up everything. (With the holes you might even get a huge whistle.)

[Grand Moff Yenchin]

How does rock float on water? Seriously, underground water reservoirs only exist because the rock above them is porous. And what's this "mantle" I keep hearing about? How is new crust formed as tectonic plates part if there is just water underneath?

Well since he's been dodging the question of rock floating on water for two exchanges so...

Huh? I meant that if the hole faces towards the Sun at all times, line of sight to the stars and Moon should be blocked, since the relative positions of the Sun and stars change over the course of the year, and the relative position of the Sun and Moon changes over the course of a day. Unless there are thousands of holes in that ice that are actually capable of moving around as relative to the surface.

This is where his other plot device comes from: "light scattering". Which of course doesn't work. (And debates involving the moon diminished after a couple of exchanges as well).

The reason why I was focusing on the brightness of the sun itself was because the Earth wouldn't be even be inhabitable without sufficient sunlight. Not to mention the "nice climate" creationists like to pretend.

[Lord Zentei]

What does he mean by "light scattering"? That the Sun's light scatters through the ice, and this becomes the stars and Moon? If so, the "stars" and "Moon" would of course not be constant, but be varying smears of light.

Where the hell is this going on, anyhow? Rapture Ready?

[Grand Moff Yenchin]

What does he mean by "light scattering"? That the Sun's light scatters through the ice, and this becomes the stars and Moon? If so, the "stars" and "Moon" would of course not be constant, but be varying smears of light.

No he actually thinks the light can scatter throughout the atmosphere. (He at least conceeded that a 2km ice shell will block light, so he had to rely on the hole and other mumbo jumbo.)

Where the hell is this going on, anyhow? Rapture Ready?

tw.bbs.soc.religion, a Chinese speaking usenet group. Creationist morons are a worldwide species.

[wolveraptor]

I highly doubt ice has the structural integrity to maintain a sphere that huge. The pressures on it must be enormous.

[Kuroneko]

Ice is simply not strong enough--in fact, it's over a thousand times times weaker than it needs to be for this trick to work structurally. The holes are small comparative to the shell itself (mass adjustment of around 1/50), so for comparison purposes I'll ignore them. Earth's radius is about R = 6.3710e7m, so that assuming a shell of inner radius r = 400km above the surface and t = 2.0km thick, we have m = 1.2e21kg of ice, for a total gravitational force of F = 1.0e22N. Since t<<(R+r), the configuration is that of a thin spherical pressure vessel, so that the stress is is around σ = [Fr/(4π(R+r)²)]/[2t] ≅ 30GPa.

More in line with the original question, ice has comparatively high albedo, so that its emissivity is very low. However, at equilibrium, these factors cancel out. The total incident radiation is about J = [3.827e26W/(4πAU²)][π(R+r)²] = 2.0e17W, so that the average absolute temperature is T = [J/(4πσ(R+r)²)]^(1/4) = 280K. This is the average; since one side is supposed to be always facing the sun, the local temperature on that side will be significantly higher.

Even the average temperature is high enough to boil the water, considering that the vapor pressure will be high relative to vacuum of space. The whole configuration is massively unstable, both structually and thermodynamically. It's a wonder why anyone would expect otherwise--comets have visible tails even when they're farther away from the Sun than Earth's orbit.

Fun exercise: consider what happens when a 1.2e21kg is dropped from 400km, more or less uniformly over the Earth and over short period of time (since the structure cannot hold, no 150-day delivery involved).

[Darth Wong]

I particularly enjoy the part about "air buoyancy" holding up the ice. Is this moron friend aware that ice is several orders of magnitude denser than air? Does he even understand what buoyancy is and how it works?

This magic lighter-than-air ice material must be some rather amazing stuff.

[Grand Moff Yenchin]

Fun exercise: consider what happens when a 1.2e21kg is dropped from 400km, more or less uniformly over the Earth and over short period of time (since the structure cannot hold, no 150-day delivery involved).

It's not gonna be nice. Worse than that BDZ bombardment of 40 days rain.

And on a sidenote: Dr. Dino proposed a giant comet to do the job.

This magic lighter-than-air ice material must be some rather amazing stuff.

Well he has rocks which could float on water...

[wolveraptor]

The best flood theory so far is, "Well God had a lot to drink for lunch, and he couldn't make it to a portaloo on time..."

[Darth Wong]

I would actually like to see somebody try and make a movie showing this "ice shell" around the Earth, because I have a feeling that the concept would look really stupid if you tried to visualize it, so that true believers would be impressed but everyone else would just laugh his ass off.

[darthdavid]

I would actually like to see somebody try and make a movie showing this "ice shell" around the Earth, because I have a feeling that the concept would look really stupid if you tried to visualize it, so that true believers and most of the generally moronic population would be impressed but the small part of the population that's not terminally stupid would just laugh his ass off.

Fixed...

[Losonti Tokash]

Ah, this story again. I had a college professor a year or so ago make this exact claim during a lecture. For some strange reason, half of the students dropped out after the first couple classes.