You make a very interesting point here, one that sent me running to look up some numbers and find a calculator. My fast crappy math seems to suggest that we could very plausibly see the moon from Mars with a decent camera.
When the rovers were launched, Mars was about 78 million km from Earth. The average distance from Earth to the moon is roughly 400000 km. So assuming the angles are right, there would be a maximum angular separation of about s/r = 0.005 radians or 0.3 degrees - more than enough to distinguish with the naked eye. The moon is fairly large; its diameter is about 3/4 that of Mercury. Although it is not as brightly illuminated due to greater distance from the sun, my intuition is that it ought to be visible to the naked eye.
I don't know if the Spirit or the Opportunity cameras are up to it, or if the orbital configurations are so convenient right now, but a photo of the Earth and moon like that you suggest seems entirely plausible.
As it turns out, mineralogy may be a perfectly adequate way of determining mode of deposition. Sediment deposited by water will likely exhibit a whole series of chemical alterations characteristic of water-lain sediment. The first mineral indicator that occurs to me would be clay - it forms in contact with water, and is too fine-grained to be effectively deposited by wind. Clay has a distinctive x-ray diffraction pattern, and would probably show up uniquely on the spectrometers.
Additionally, aeolian (wind-lain) sediments have very characteristic grain shapes - they are unusually rounded and generally uniform in size. Sediments deposited underwater have greater variation in both size and shape. If the rover is equipped with high resolution cameras for imaging mineral grains, it should be able to make out the difference.
Should the rover be able to get up close and take decent pictures of the rocks, it should not be too hard to come to a final conclusion as to their origin. Cross-bedding as seen in the pictures can come from a wide variety of geological phenomenon, and it is too early to draw conclusions.
Wow! A personal connection
on
The Year In Ideas
·
· Score: 5, Interesting
It's sort of neat to see a story like this, because Dr. Stevenson was one of my advisors at Caltech. He's a great guy with a cool New Zealand accent and a wide assortment of knowledge about almost everything. But I can shed a little light on this, both because I know him and because I have a geology background.
First, for the credulous, he's semi-joking. The physics of the iron sinking into the core is actually plausible, but his tone when talking about "generating a crack in the crust" is tongue-in-cheek. This would require a much larger nuclear detonation, say, than has ever been tested by anybody. The seismic consequences would be... bad. What's more, we aren't anywhere even close to being able to design probes that could survive such an environment and send messages back.
To dispel a common misconception, the interior of the earth is NOT molten. Omitting some interesting boundary layers, the Earth is composed of the following chunks from the inside out: the inner core (solid iron alloy), the outer core (molten iron alloy), the mantle (solid rock), and the crust (we live on it). If you're curious as to how we know, it's because liquids and solids have dramatically different properties as far as transmitting seismic waves. I just found a decent site at JPL here that illustrates the earth's structure nicely, although it appears to have been written for grade schoolers.
The idea that the mantle is liquid is one of the most widely held misconceptions about major geological concepts. It exhibits ductile deformation, so it flows something like a liquid, with a speed of centimeters or meters per year. Magma, however, results when rock is pushed up into the crust from the mantle - the decrease in pressure lowers the melting temperature. It can also be generated when water seeps into hot rocks - wet rock has a lower melting temperature. It is NOT evidence that the mantle itself is liquid.
So why would this work? A large body of iron would be much denser than mantle rock, and at a hundred million kilograms, the net downward force would be considerable enough to force mantle rock out of the way. I'm too lazy to figure out the physics for this post, but I would imagine this is the content of the Nature article. The interesting question would be, "would ductile deformation occur quickly enough to get the iron down in a reasonable amount of time?" The answer, apparently, is 'yes'.
I am a 23-year-old high school teacher, and I was raised with a keyboard in hand. As someone with a technical background and not much older than the students, I am certainly comfortable with installing, using, and maintaining computers. However, I have grave doubts about their extensive use in the schools.
One point that has not been adequately made is that this will be a recurring expense. Computers obsolesce quickly, to a degree such that 5-year-old computers will generally not run new software. Not only are computers for each student a significant expense, but the investment must be made again in 5 years!
At North Hollywood High School, where I teach, each classroom was recently equipped with three or four modern PCs. Less than six months later, perhaps 80% of them were nonfunctioning, generally due to abuse by students or teachers. In some cases, kids actually opened up the cases to steal the RAM or hard drives for use at home.
Computers are an excellent research tool and can be a good source of explanatory animations for difficult concepts. However, they cannot teach students to think, which is the primary function of an education. They certainly have applications, but the idea that a regular curriculum should be largely supplanted by a computer-based one is absurd.
What's so great about the article? The reason this particular spammer quit!
He quit because of hostile, harassing emails from the angry public! They work! Every email you've sent telling a spammer that they're a worthless turd of a human being had some miniscule effect!
Even now, the guy admits no moral qualms about his former job. He's still a thoughtless punk who sees nothing wrong with the practice, and I'd still like to punch him in the nose. But he QUIT, because we made his life miserable in return.
The lesson: keep giving 'em hell. It's not just gratifying, it sometimes works.
As it turns out, absolute zero is not the "coldest possible temperature". It is impossible to attain absolute zero, as a little basic quantum mechanics tells us. Particles will ALWAYS retain some amount of energy, the "Zero Point Energy", which cannot be removed. More accurately, we can say that absolute zero is the lower bound on the range of possible temperatures - but is not included.
...or is the military run by 7-year-old boys? In third grade, I too would have been very excited about a truck with missile launchers and a huge artillery system termed "Crusader".
Don't even get me started on the names of operations. "Infinite Justice", anybody? It sounds like something out of the Mighty Morphin' Power Rangers.
Actually, about two years ago, I had a maddened craving for some SC2 action. My old disks were long gone, probably somewhere in my father's bin of obsolete computer stuff - and certainly not handy. So I poked around some on the Web.
I was thrilled to find that Accolade was actually actively still selling the game. They'd taken the whole thing, along with scanned versions of the docs, and packed it into one self-extracting ZIP. For $10 or $15, you could download the game (at 10 meg or so). It worked just fine, and my nostalgia trip was more than worth the money.
Their webpage seems sorta screwed up at the moment, and I don't feel like taking the time to research the details - but I loved the idea. It would be nice if more gaming companies would package older games into downloads and sell them over the Web. Their costs = 0, and they squeeze a few extra marginal profits out of the business. At our end, it becomes a lot easier to find vintage games.
Of course, this whole OSing (is that a verb) of the code rocks, and I'm thrilled to see the game perpetuated and potentially improved. Not that you could do much to make it better.
*happy campers we are*
Re:I would have to say...
on
The Aging Gamer
·
· Score: 5, Insightful
> That is quite scary, considering that gaming is at an all time high right now...so, if in 20 years > 90+% of gamers are over 35, i wouldn't be shocked....
Ummmm. That really doesn't make any sense. The birth rate isn't plummetting catastrophically. I teach high school - and I assure you that a large fraction of the 14-year-olds on down are quite hooked. They'll be 34 in 20 years, and I don't see any likely reason that gaming would stop gaining recruits. 10 or so to 35 is an awfully big fraction of the population, much more than 10% - even if they WERE underrepresented in the gaming group, they'd claim more than 10% of it. And I see such an underrepresentation as unlikely. A higher fraction of today's youth are gamers, for instance, than were gamers in the 70s.
Easy enough to calculate the approximate pH change, at least assuming the lake isn't buffered (probably a poor assumption).
3.5 lbs = 1.6 kg Na
Assuming the reaction occurs completely:
2Na + 2H2O --> 2Na(+) + H2 + 2OH(-)
Each molecule of Na should generate one hydroxide molecule. So 1600 g Na * (1 mol / 40 g) = 40 mols Na and 40 mols OH(-) generated.
Now we look at the pond: 1 acre = 4000 m^2 (approx). Figure a shallow pond, average depth 3 m. Then volume = 12000 m^3 or 12 million liters. Concentration OH(-): 40 mol/12 million L.
High school chem is your friend. Moderate pH change, nothing huge, but maybe bad for the fish. In reality, the number is probably considerably less - I'd imagine that organic buffers would soak up all those extra hydroxide ions.
Slashdot Mirror
You make a very interesting point here, one that sent me running to look up some numbers and find a calculator. My fast crappy math seems to suggest that we could very plausibly see the moon from Mars with a decent camera.
When the rovers were launched, Mars was about 78 million km from Earth. The average distance from Earth to the moon is roughly 400000 km. So assuming the angles are right, there would be a maximum angular separation of about s/r = 0.005 radians or 0.3 degrees - more than enough to distinguish with the naked eye. The moon is fairly large; its diameter is about 3/4 that of Mercury. Although it is not as brightly illuminated due to greater distance from the sun, my intuition is that it ought to be visible to the naked eye.
I don't know if the Spirit or the Opportunity cameras are up to it, or if the orbital configurations are so convenient right now, but a photo of the Earth and moon like that you suggest seems entirely plausible.
As it turns out, mineralogy may be a perfectly adequate way of determining mode of deposition. Sediment deposited by water will likely exhibit a whole series of chemical alterations characteristic of water-lain sediment. The first mineral indicator that occurs to me would be clay - it forms in contact with water, and is too fine-grained to be effectively deposited by wind. Clay has a distinctive x-ray diffraction pattern, and would probably show up uniquely on the spectrometers.
Additionally, aeolian (wind-lain) sediments have very characteristic grain shapes - they are unusually rounded and generally uniform in size. Sediments deposited underwater have greater variation in both size and shape. If the rover is equipped with high resolution cameras for imaging mineral grains, it should be able to make out the difference.
Should the rover be able to get up close and take decent pictures of the rocks, it should not be too hard to come to a final conclusion as to their origin. Cross-bedding as seen in the pictures can come from a wide variety of geological phenomenon, and it is too early to draw conclusions.
It's sort of neat to see a story like this, because Dr. Stevenson was one of my advisors at Caltech. He's a great guy with a cool New Zealand accent and a wide assortment of knowledge about almost everything. But I can shed a little light on this, both because I know him and because I have a geology background.
First, for the credulous, he's semi-joking. The physics of the iron sinking into the core is actually plausible, but his tone when talking about "generating a crack in the crust" is tongue-in-cheek. This would require a much larger nuclear detonation, say, than has ever been tested by anybody. The seismic consequences would be... bad. What's more, we aren't anywhere even close to being able to design probes that could survive such an environment and send messages back.
To dispel a common misconception, the interior of the earth is NOT molten. Omitting some interesting boundary layers, the Earth is composed of the following chunks from the inside out: the inner core (solid iron alloy), the outer core (molten iron alloy), the mantle (solid rock), and the crust (we live on it). If you're curious as to how we know, it's because liquids and solids have dramatically different properties as far as transmitting seismic waves. I just found a decent site at JPL here that illustrates the earth's structure nicely, although it appears to have been written for grade schoolers.
The idea that the mantle is liquid is one of the most widely held misconceptions about major geological concepts. It exhibits ductile deformation, so it flows something like a liquid, with a speed of centimeters or meters per year. Magma, however, results when rock is pushed up into the crust from the mantle - the decrease in pressure lowers the melting temperature. It can also be generated when water seeps into hot rocks - wet rock has a lower melting temperature. It is NOT evidence that the mantle itself is liquid.
So why would this work? A large body of iron would be much denser than mantle rock, and at a hundred million kilograms, the net downward force would be considerable enough to force mantle rock out of the way. I'm too lazy to figure out the physics for this post, but I would imagine this is the content of the Nature article. The interesting question would be, "would ductile deformation occur quickly enough to get the iron down in a reasonable amount of time?" The answer, apparently, is 'yes'.
I am a 23-year-old high school teacher, and I was raised with a keyboard in hand. As someone with a technical background and not much older than the students, I am certainly comfortable with installing, using, and maintaining computers. However, I have grave doubts about their extensive use in the schools.
One point that has not been adequately made is that this will be a recurring expense. Computers obsolesce quickly, to a degree such that 5-year-old computers will generally not run new software. Not only are computers for each student a significant expense, but the investment must be made again in 5 years!
At North Hollywood High School, where I teach, each classroom was recently equipped with three or four modern PCs. Less than six months later, perhaps 80% of them were nonfunctioning, generally due to abuse by students or teachers. In some cases, kids actually opened up the cases to steal the RAM or hard drives for use at home.
Computers are an excellent research tool and can be a good source of explanatory animations for difficult concepts. However, they cannot teach students to think, which is the primary function of an education. They certainly have applications, but the idea that a regular curriculum should be largely supplanted by a computer-based one is absurd.
What's so great about the article? The reason this particular spammer quit!
He quit because of hostile, harassing emails from the angry public! They work! Every email you've sent telling a spammer that they're a worthless turd of a human being had some miniscule effect!
Even now, the guy admits no moral qualms about his former job. He's still a thoughtless punk who sees nothing wrong with the practice, and I'd still like to punch him in the nose. But he QUIT, because we made his life miserable in return.
The lesson: keep giving 'em hell. It's not just gratifying, it sometimes works.
As it turns out, absolute zero is not the "coldest possible temperature". It is impossible to attain absolute zero, as a little basic quantum mechanics tells us. Particles will ALWAYS retain some amount of energy, the "Zero Point Energy", which cannot be removed. More accurately, we can say that absolute zero is the lower bound on the range of possible temperatures - but is not included.
...or is the military run by 7-year-old boys? In third grade, I too would have been very excited about a truck with missile launchers and a huge artillery system termed "Crusader".
Don't even get me started on the names of operations. "Infinite Justice", anybody? It sounds like something out of the Mighty Morphin' Power Rangers.
Actually, about two years ago, I had a maddened craving for some SC2 action. My old disks were long gone, probably somewhere in my father's bin of obsolete computer stuff - and certainly not handy. So I poked around some on the Web.
I was thrilled to find that Accolade was actually actively still selling the game. They'd taken the whole thing, along with scanned versions of the docs, and packed it into one self-extracting ZIP. For $10 or $15, you could download the game (at 10 meg or so). It worked just fine, and my nostalgia trip was more than worth the money.
Their webpage seems sorta screwed up at the moment, and I don't feel like taking the time to research the details - but I loved the idea. It would be nice if more gaming companies would package older games into downloads and sell them over the Web. Their costs = 0, and they squeeze a few extra marginal profits out of the business. At our end, it becomes a lot easier to find vintage games.
Of course, this whole OSing (is that a verb) of the code rocks, and I'm thrilled to see the game perpetuated and potentially improved. Not that you could do much to make it better.
*happy campers we are*
> That is quite scary, considering that gaming is at an all time high right now...so, if in 20 years
> 90+% of gamers are over 35, i wouldn't be shocked....
Ummmm. That really doesn't make any sense. The birth rate isn't plummetting catastrophically. I teach high school - and I assure you that a large fraction of the 14-year-olds on down are quite hooked. They'll be 34 in 20 years, and I don't see any likely reason that gaming would stop gaining recruits. 10 or so to 35 is an awfully big fraction of the population, much more than 10% - even if they WERE underrepresented in the gaming group, they'd claim more than 10% of it. And I see such an underrepresentation as unlikely. A higher fraction of today's youth are gamers, for instance, than were gamers in the 70s.
Easy enough to calculate the approximate pH change, at least assuming the lake isn't buffered (probably a poor assumption).
3.5 lbs = 1.6 kg Na
Assuming the reaction occurs completely:
2Na + 2H2O --> 2Na(+) + H2 + 2OH(-)
Each molecule of Na should generate one hydroxide molecule. So 1600 g Na * (1 mol / 40 g) = 40 mols Na and 40 mols OH(-) generated.
Now we look at the pond: 1 acre = 4000 m^2 (approx). Figure a shallow pond, average depth 3 m. Then volume = 12000 m^3 or 12 million liters. Concentration OH(-): 40 mol/12 million L.
[OH-] = 3.3 x 10^-6
pH = -log ((10^-14)/[OH-]) = 8.5
High school chem is your friend. Moderate pH change, nothing huge, but maybe bad for the fish. In reality, the number is probably considerably less - I'd imagine that organic buffers would soak up all those extra hydroxide ions.