Generally when people are talking about the Sun's power density, they are talking about the region where fusion actually occurs, in the core, not the entire visible sphere, which is the number you are using. That would be a bit like talking about the energy density in a tokamak by averaging the power output over the volume of the entire tokamak structure rather than just the actual fuel confined in the magnetic field.
The Solar core is 19% of the Solar radius, and thus the energy density in the core, where fuel is burned, is 150 times higher - 40 W/m^3.
The likely calculation - at this moment in history it is better for Californians to have a seasoned hand experienced at dealing with Senate shenanigans, and positioned to take a powerful position (as the second most senior Democrat in the Senate) when the Democrats take the Senate in 2020.
Both parties made that calculation and so Democrats voted in re-elect her, and Republicans voted for the new guy.
And frankly, it's not clear to me that most travelers actually care that much, based on the fact that although legroom information is available from the airlines, only one of the major flight search tools provides it.
Data is not being provided in useful convenient form to consumer, therefore the consumer doesn't care that much? No, it just means that the booking tools chose not to provide it.
Offering premium economy is the norm rather than the exception. Most airlines offer a bigger seat/more leg room without the extra "package" of business/first class.
First sentence of the linked Wikipedia article "Premium economy is a travel class offered on some airlines."
No, it is not the norm, it is the exception, and without standards and data disclosure requirements, you don't know what the dollars versus legroom trade-off really is.
Then you're not traveling enough for business or you'd get upgraded automatically and for free. Anyway, most businesses will let you pay for the upgrade cost out of your own pocket. And most airlines will let you book the upgrade separately immediately after ticket purchase so long as they do not buy a basic economy fare. And if your company is trying to save $80 on your ticket by buying basic economy then you ought to put your foot down and tell them you won't travel if they're not willing to spend a few extra dollars so that you have the option to buy an upgrade.
Actually they did, or rather do. Those "low prices" are difficult to compare because of the unbundling of services (like "checked baggage") with ever multiplying fees stacked on top. It becomes very difficult to compare equivalent fares. There are tons of complaints about this situation.
And leg room information is not provided with your fare. It you paid a higher ticket price, would you be able to reasonably expect more leg room? Please. If there is a difference it is as likely to be less, plus you just paid more for (less than) nothing.
You can't shop for "more leg room" on flights unless you go whole hog and jump to business class. I have started to see offers for "pay for more legroom starting at $X" when I do the kiosk baggage check, but they don't provide comparative data about what you are buying, and it is offered at the worst possible time to make an informed decision.
This is yet another case where the market place is racing to the bottom, and regulations are needed to step in to set minimum standards and providing honest information to the consumer.
I'm just an astronomy fan boy, but if something's coming in from the Oort Cloud, isn't that far enough away that all orbits are going to look parabolic to the limits of measurable accuracy? I mean we can barely determine orbits in the Kupier belt, right?
Bingo.
Not really to the "limits of measurable accuracy" but to the "limits of accuracy measured", sure. Accurate orbital determination requires lots of observations of very dim objects, and telescope time is limited. Not enough observations along a long arc, and it becomes insufficiently determined.
But we do know which are comets are closest to being true parabolas. It is easy to determine. They hit the Sun.
This is not rare, in fact about 100 comets a year do this. In 2010, a good year for sun-diving comets it was 200. In fact, most comets that are being discovered now hit the Sun. Partly this is because we have SOHO in space doing the observations, and lots of small comets suddenly brighten as they approach the Sun as they vaporize all at once under the super-spot-light that is the Sun, kind of like seeing lots of moths near a light. They do cluster there, and mostly can't see them at all unless they are near the light. Such observations were hard to do from Earth's surface due the scattered glare of the Sun.
The little ones that don't hit the Sun that are dim, we never see them at all.
The body of near-parabolic comets we know of are relatively large, but many are still dim enough that observations far from the Sun are difficult.
You only get a parabolic orbit if it's traveling exactly at escape velocity. OK, yes, I understand that there are limits to how precise our measurements are and that leads to a margin of error in the calculated orbit, but I can't help but think that there's something wrong when there are hundreds of comets discovered since 1950 with calculated orbits at exactly escape velocity, as close as we can calculate it.
Hang on. In other papers these same researchers use the term "near-parabolic" for this same class of comets, this short paper needed an editor. In some cases the observational errors (particularly in the earlier comets) are large that we cannot distinguish them from parabolic orbits. Nothing mysteriously wrong.
FWIW there is no great discovery revealed by this paper. It shows that a recent comet has a sufficiently poorly known orbit that it could be significantly hyperbolic. Or not. The data isn't available. This paper is a plea for more systematic observation procedures.
Refrigeration equipment, on the other hand.... is designed to contain CFCs, not release them.
And as we all know all refrigeration equipment is leak-free and lasts forever. Why, every refrigerator, and AC system for factories or houses or cars ever made are still in existence and maintaining their original coolant inventory unchanged even 60 years later! Why, when cars are scrapped they carefully remove their air conditioning systems for permanent storage!
Refrigeration equipment only temporarily stores refrigerant, until it leaks, or becomes contaminated or otherwise is emptied for servicing, or reaches the end of its service life whereupon it is scrapped, and no one bothers to recover the refrigerant in it. The average retention period across all cooling systems back in the 1970s when this problem was identified was less than a decade. So all the refrigerant that is manufactured gets put into the atmosphere, with aonly hte last deacde of production or so held back.
Assuming everything works out, can it produce iron from ore cheaper than existing carbon oxidation based processes? (Probably not.)
Very little raw iron is made in the U.S. now. The iron production industry has moved to China and India, or Europe (including Russia). If it is a more expensive process then governmental action of various forms will be needed to achieve adoption in the places were pig iron is still being produced in quantity.
BTW, most of U.S. coal export is metallurgical for making iron overseas. Adoption of this process will accelerate the decline of the U.S. coal industry.
My favorite stupid Utopia idea included in this very good list is Arcosanti in Arizona. The list (based on a comment in a referenced article) asserts that Arcosanti, and its economy, was to be based on selling wind-chimes. This is false. Soleri paid not attention to the economic basis of his supposed Utopia at all. He was an architect and all he thought about was building vast complex structures. No thought about paying for them, or how they would be supported by economic activity.
The problem with nearly all manufactured Utopias (thus far) is that all societies and communities must have an economic base. That must come first, only then can you plan on an "optimal" design. Kibbutzim in Israel worked fairly well because they were planned and intended as functioning farm economies from the start, and after years of success at that plowed revenue into developing local industries.
Five hundred years ago, the fastest a human being had ever travelled was 25mph on a horse. A hundred years ago, early planes could reach 100mph. Fifty years ago, the Apollo missions travelled at 24,000 mph.
In another fifty years, we'll have space liners going several times the speed of light, and popping to an asteroid will be like walking over the road to a corner shop.
Not sure if this was intended seriously or not.
A real account of human travel is that humans were limited to 4 MPH for long distances, until they learned to ride horses about 5500 years ago, and then they reached 25 MPH. But that reached the limit of the new technique no further progress was made for 5300 years.
The steam locomotives were invented, and then internal combustion engines, and the ability to travel rose to around 100 MPH by the beginning of the 20th Century. But that came close to reaching the practical limit of land transportation, and has only climbed to about 250 MPH recently (on limited routes)more than a century later, and any prospects for further increase depend on exotic evacuated tunnels on even more limited routes.
But airplanes were invented at the start of the 20th Century, and by 1940 had got close to the practical limit for air transportation of just below the speed of sound (about 750 MPH), though it was not until about 1960 that this became available generally (with extremely limited aircraft travel up to about 1600 MPH). And having reached the practical limit of air travel, has not advanced at all in 60 years, speed-wise.
But rockets were demonstrated that could propel humans to 25000 MPH by the late 1960s, but this was close to the practical limit for chemical rockets, and in the next 50 years it has not advanced at all.
Exotic space propulsion (electric drives, nuclear propulsion) promised higher velocities, up to 360,000 MPH maybe but until fusion power comes along that will be roughly the limit. No know physics will support travel faster than about 5% c.
I remember an speculative article in Analog Science Fiction Magazine from the 1970s that extrapolated from the (then recent) increase in manned speeds (25000 MPH) to confidently predict that by the power of this arithmetic magic, that we would be travelling at light-speed right now, which clearly we aren't.
The real story is that new technologies come along, boost maximum speeds until they reach their technical limit. The progress stops (and least as measured as distance traveled in time "t").
I wonder if the German spy company Wolf Intelligence's name was inspired by Markus Wolf, the most notorious spymaster of the East German Stasi -- the spy organization with a state attached.
For comparison desalinization technology currently produces water for 0.2 cents per liter. This water-from-the-air process produces water at the cost of $20,000 per acre-foot, to use the U.S. unit of measurement for water systems. Not sure what water at this price is good for. Nearly everywhere, no matter how far inland, desalinizing seawater and pumping it to them would be much cheaper.
Therein you have a vast, bright open space full of life and where you can live basically wherever you want; the lowest-mass option for crew quarters is just large tents hanging from catenaries (non-rigid) or the frame (rigid). Don't get along with someone? Move half a kilometer away from them, to the opposite side of the habitat.
You can't do this on Earth - live where ever you want. Why would this be possible in the far, far more space constrained Venus colony structure?
On any off-world colony, where all available space is part of a man-made structure (and in this case all space not just habitable living space) it will be at a premium and will be strictly allocated by a management/legal system (like land, or apartments, or offices, here on Earth).
The lifting capacity of Venus's atmosphere does not lead to living on an almost empty open plain under a huge empty volume, it leads to an apartment and office building in the sky that keeps its average density to below 0.5 kg/m^3. In Landis's piece he links to he describes living on Venus as "The result would be an environment as spacious as a typical city", and as long as he means "a typical well built-up city" I agree.
Supplies are essential, but they're aren't *that* essential.
Considering that most wars are lost based on the lack of supplies... or won, by making the enemy suffer from a lack of supplies... just saying.
In defense of im_thatoneguy, while logistics are essential they also fungible. To a well supplied military (like the U.S.) no particular supply vehicle is essential. If an unmanned supply vehicle gets blown up there is another one with replacement materiel that will be along fairly soon. Not so troops. There have been historical periods were troops were "cannon fodder" that is not the case now - every casualty attracts attention and potentially undermines political support.
Also it would be a stretch to argue that most wars are won or lost on supplies. Adequate logistics are essential in every war, for both sides, but most wars are won or lost based on fighting, not supply issues.
Q. What acute problem does an E-Scooter solve?
A. Nothing!
The acute problem is the "last few miles" problem of urban mass transit rail systems (the "Metro" as it is called in many cities around the world). You can take a Metro into the city center to commute to your job, but then you have get to that final destination on foot. On a Metro can cross an urban area at an average speed of 30 MPH, but then you have to get to your final destination at 3 MPH. The whole commuting strategy is much improved if you can do that final bit at 15 MPH.
Slashdot Mirror
Generally when people are talking about the Sun's power density, they are talking about the region where fusion actually occurs, in the core, not the entire visible sphere, which is the number you are using. That would be a bit like talking about the energy density in a tokamak by averaging the power output over the volume of the entire tokamak structure rather than just the actual fuel confined in the magnetic field.
The Solar core is 19% of the Solar radius, and thus the energy density in the core, where fuel is burned, is 150 times higher - 40 W/m^3.
I don't even know what to make of that.
The likely calculation - at this moment in history it is better for Californians to have a seasoned hand experienced at dealing with Senate shenanigans, and positioned to take a powerful position (as the second most senior Democrat in the Senate) when the Democrats take the Senate in 2020.
Both parties made that calculation and so Democrats voted in re-elect her, and Republicans voted for the new guy.
And frankly, it's not clear to me that most travelers actually care that much, based on the fact that although legroom information is available from the airlines, only one of the major flight search tools provides it.
Data is not being provided in useful convenient form to consumer, therefore the consumer doesn't care that much? No, it just means that the booking tools chose not to provide it.
Offering premium economy is the norm rather than the exception. Most airlines offer a bigger seat/more leg room without the extra "package" of business/first class.
First sentence of the linked Wikipedia article "Premium economy is a travel class offered on some airlines."
No, it is not the norm, it is the exception, and without standards and data disclosure requirements, you don't know what the dollars versus legroom trade-off really is.
Then you're not traveling enough for business or you'd get upgraded automatically and for free. Anyway, most businesses will let you pay for the upgrade cost out of your own pocket. And most airlines will let you book the upgrade separately immediately after ticket purchase so long as they do not buy a basic economy fare. And if your company is trying to save $80 on your ticket by buying basic economy then you ought to put your foot down and tell them you won't travel if they're not willing to spend a few extra dollars so that you have the option to buy an upgrade.
See everyone? No problem! /s
Or, let's just skip that and start the beatings. It'll be more humane than forcing airline CEOs to use their own airlines.
You can do both. Just saying.
Actually they did, or rather do. Those "low prices" are difficult to compare because of the unbundling of services (like "checked baggage") with ever multiplying fees stacked on top. It becomes very difficult to compare equivalent fares. There are tons of complaints about this situation.
And leg room information is not provided with your fare. It you paid a higher ticket price, would you be able to reasonably expect more leg room? Please. If there is a difference it is as likely to be less, plus you just paid more for (less than) nothing.
You can't shop for "more leg room" on flights unless you go whole hog and jump to business class. I have started to see offers for "pay for more legroom starting at $X" when I do the kiosk baggage check, but they don't provide comparative data about what you are buying, and it is offered at the worst possible time to make an informed decision.
This is yet another case where the market place is racing to the bottom, and regulations are needed to step in to set minimum standards and providing honest information to the consumer.
I'm just an astronomy fan boy, but if something's coming in from the Oort Cloud, isn't that far enough away that all orbits are going to look parabolic to the limits of measurable accuracy? I mean we can barely determine orbits in the Kupier belt, right?
Bingo.
Not really to the "limits of measurable accuracy" but to the "limits of accuracy measured", sure. Accurate orbital determination requires lots of observations of very dim objects, and telescope time is limited. Not enough observations along a long arc, and it becomes insufficiently determined.
But we do know which are comets are closest to being true parabolas. It is easy to determine. They hit the Sun.
This is not rare, in fact about 100 comets a year do this. In 2010, a good year for sun-diving comets it was 200. In fact, most comets that are being discovered now hit the Sun. Partly this is because we have SOHO in space doing the observations, and lots of small comets suddenly brighten as they approach the Sun as they vaporize all at once under the super-spot-light that is the Sun, kind of like seeing lots of moths near a light. They do cluster there, and mostly can't see them at all unless they are near the light. Such observations were hard to do from Earth's surface due the scattered glare of the Sun.
The little ones that don't hit the Sun that are dim, we never see them at all.
The body of near-parabolic comets we know of are relatively large, but many are still dim enough that observations far from the Sun are difficult.
You only get a parabolic orbit if it's traveling exactly at escape velocity. OK, yes, I understand that there are limits to how precise our measurements are and that leads to a margin of error in the calculated orbit, but I can't help but think that there's something wrong when there are hundreds of comets discovered since 1950 with calculated orbits at exactly escape velocity, as close as we can calculate it.
Hang on. In other papers these same researchers use the term "near-parabolic" for this same class of comets, this short paper needed an editor. In some cases the observational errors (particularly in the earlier comets) are large that we cannot distinguish them from parabolic orbits. Nothing mysteriously wrong.
FWIW there is no great discovery revealed by this paper. It shows that a recent comet has a sufficiently poorly known orbit that it could be significantly hyperbolic. Or not. The data isn't available. This paper is a plea for more systematic observation procedures.
Refrigeration equipment, on the other hand.... is designed to contain CFCs, not release them.
And as we all know all refrigeration equipment is leak-free and lasts forever. Why, every refrigerator, and AC system for factories or houses or cars ever made are still in existence and maintaining their original coolant inventory unchanged even 60 years later! Why, when cars are scrapped they carefully remove their air conditioning systems for permanent storage!
Refrigeration equipment only temporarily stores refrigerant, until it leaks, or becomes contaminated or otherwise is emptied for servicing, or reaches the end of its service life whereupon it is scrapped, and no one bothers to recover the refrigerant in it. The average retention period across all cooling systems back in the 1970s when this problem was identified was less than a decade. So all the refrigerant that is manufactured gets put into the atmosphere, with aonly hte last deacde of production or so held back.
Well, the FAA, not NASA. It was called Operation Bongo II. Is this Operation Bongo III?
Oops wrong thread. Go about your business.
Well, the FAA, not NASA. It was called Operation Bongo II. Is this Operation Bongo III?
Assuming everything works out, can it produce iron from ore cheaper than existing carbon oxidation based processes? (Probably not.)
Very little raw iron is made in the U.S. now. The iron production industry has moved to China and India, or Europe (including Russia). If it is a more expensive process then governmental action of various forms will be needed to achieve adoption in the places were pig iron is still being produced in quantity.
BTW, most of U.S. coal export is metallurgical for making iron overseas. Adoption of this process will accelerate the decline of the U.S. coal industry.
My favorite stupid Utopia idea included in this very good list is Arcosanti in Arizona. The list (based on a comment in a referenced article) asserts that Arcosanti, and its economy, was to be based on selling wind-chimes. This is false. Soleri paid not attention to the economic basis of his supposed Utopia at all. He was an architect and all he thought about was building vast complex structures. No thought about paying for them, or how they would be supported by economic activity.
The problem with nearly all manufactured Utopias (thus far) is that all societies and communities must have an economic base. That must come first, only then can you plan on an "optimal" design. Kibbutzim in Israel worked fairly well because they were planned and intended as functioning farm economies from the start, and after years of success at that plowed revenue into developing local industries.
Statistics about statistical fraud. Down the rabbit hole we go.
Maybe you should rethink this. You'll look a lot better in artist renderings.
Five hundred years ago, the fastest a human being had ever travelled was 25mph on a horse. A hundred years ago, early planes could reach 100mph. Fifty years ago, the Apollo missions travelled at 24,000 mph.
In another fifty years, we'll have space liners going several times the speed of light, and popping to an asteroid will be like walking over the road to a corner shop.
Not sure if this was intended seriously or not.
A real account of human travel is that humans were limited to 4 MPH for long distances, until they learned to ride horses about 5500 years ago, and then they reached 25 MPH. But that reached the limit of the new technique no further progress was made for 5300 years.
The steam locomotives were invented, and then internal combustion engines, and the ability to travel rose to around 100 MPH by the beginning of the 20th Century. But that came close to reaching the practical limit of land transportation, and has only climbed to about 250 MPH recently (on limited routes)more than a century later, and any prospects for further increase depend on exotic evacuated tunnels on even more limited routes.
But airplanes were invented at the start of the 20th Century, and by 1940 had got close to the practical limit for air transportation of just below the speed of sound (about 750 MPH), though it was not until about 1960 that this became available generally (with extremely limited aircraft travel up to about 1600 MPH). And having reached the practical limit of air travel, has not advanced at all in 60 years, speed-wise.
But rockets were demonstrated that could propel humans to 25000 MPH by the late 1960s, but this was close to the practical limit for chemical rockets, and in the next 50 years it has not advanced at all.
Exotic space propulsion (electric drives, nuclear propulsion) promised higher velocities, up to 360,000 MPH maybe but until fusion power comes along that will be roughly the limit. No know physics will support travel faster than about 5% c.
I remember an speculative article in Analog Science Fiction Magazine from the 1970s that extrapolated from the (then recent) increase in manned speeds (25000 MPH) to confidently predict that by the power of this arithmetic magic, that we would be travelling at light-speed right now, which clearly we aren't.
The real story is that new technologies come along, boost maximum speeds until they reach their technical limit. The progress stops (and least as measured as distance traveled in time "t").
I wonder if the German spy company Wolf Intelligence's name was inspired by Markus Wolf, the most notorious spymaster of the East German Stasi -- the spy organization with a state attached.
That 2 cents per liter is cheap, no?
No, not cheap at all, for water.
For comparison desalinization technology currently produces water for 0.2 cents per liter. This water-from-the-air process produces water at the cost of $20,000 per acre-foot, to use the U.S. unit of measurement for water systems. Not sure what water at this price is good for. Nearly everywhere, no matter how far inland, desalinizing seawater and pumping it to them would be much cheaper.
Therein you have a vast, bright open space full of life and where you can live basically wherever you want; the lowest-mass option for crew quarters is just large tents hanging from catenaries (non-rigid) or the frame (rigid). Don't get along with someone? Move half a kilometer away from them, to the opposite side of the habitat.
You can't do this on Earth - live where ever you want. Why would this be possible in the far, far more space constrained Venus colony structure?
On any off-world colony, where all available space is part of a man-made structure (and in this case all space not just habitable living space) it will be at a premium and will be strictly allocated by a management/legal system (like land, or apartments, or offices, here on Earth).
The lifting capacity of Venus's atmosphere does not lead to living on an almost empty open plain under a huge empty volume, it leads to an apartment and office building in the sky that keeps its average density to below 0.5 kg/m^3. In Landis's piece he links to he describes living on Venus as "The result would be an environment as spacious as a typical city", and as long as he means "a typical well built-up city" I agree.
Supplies are essential, but they're aren't *that* essential.
Considering that most wars are lost based on the lack of supplies ... or won, by making the enemy suffer from a lack of supplies ... just saying.
In defense of im_thatoneguy, while logistics are essential they also fungible. To a well supplied military (like the U.S.) no particular supply vehicle is essential. If an unmanned supply vehicle gets blown up there is another one with replacement materiel that will be along fairly soon. Not so troops. There have been historical periods were troops were "cannon fodder" that is not the case now - every casualty attracts attention and potentially undermines political support.
Also it would be a stretch to argue that most wars are won or lost on supplies. Adequate logistics are essential in every war, for both sides, but most wars are won or lost based on fighting, not supply issues.
Because in nut-land there can only be one answer to all situations everywhere in the world.
That this won't see the light of day.
Q. What acute problem does an E-Scooter solve? A. Nothing!
The acute problem is the "last few miles" problem of urban mass transit rail systems (the "Metro" as it is called in many cities around the world). You can take a Metro into the city center to commute to your job, but then you have get to that final destination on foot. On a Metro can cross an urban area at an average speed of 30 MPH, but then you have to get to your final destination at 3 MPH. The whole commuting strategy is much improved if you can do that final bit at 15 MPH.