I was already assuming a 25% duty cycle (flashing aka moving the laser). I don't think you can trim it more than that without increasing the power required to make it noticeable to the naked eye. But we're still talking about a faint flashing in the sky... Not anything that demands attention.. just something subtly noticeable.
The 100mW figure was based on the brightness of the moon in the daytime sky. Surely not bright, but at least visible. Maybe 10x more would be better for people to stop and notice it...
But 1kw lasers are considered pretty high power, so we're still off by a factor of 100 or 1,000...
The realities of using a laser for this is just stupid.
The reality of "computer vision" for example was "wow, that's impossible with current technology, but it sure would be cool if we could figure out how".
This whole laser bit runs into issues of physics. We know how much light is lost in the atmosphere and how much power is lost in a laser ocilator and how much energy is output by the sun.
Even given 100% perfect efficiency on all of those, you're talking about 100 square kilometers of solar panels.
or... 10GW hours worth of batteries... yes. *chuckles* Unless we're talking about an antimatter reactor, that's still outside our capabilities. our best lithium polymer batteries get about 10 watts per pound. So... 1 billion pounds of batteries *chuckles*. Or 900 million tons of hydrogen fuel cells.... We would only need a few ounces of antimatter, given a perfect conversion. Or a couple of hydrogen bombs perfectly harnessed all at once.... right.
The idea of wide ranging signalling for tsunamis is interesting. The idea of using a geostationary laser is not. It's kinda funny actually.
To better address your question and lay a bit more clarity to it...
If a person were... say... flying... and they were up in the sky right next to the sun. Do you think a mirror in their hand would make them visible?
A mirror signaling is effective because it's done against the backdrop of the ground, which is not quite so bright as the sky, especially the sky immediately surrounding the sun.
How, dare say, do you propose to move the sattellite around when it happens to be directly in line with the sun, so as to be completely invisible.
Oye, there's so many parts of this that are just stupid.
Aside from this not working when it's cloudy, this also doesn't work when the sun is high in the sky. This is system is totally borked from 10am-6pm when the sun is up high in the sky and you won't see a flashing light against that backdrop, no matter how bright it is...
The full moon is quite visible during the day, but only if it's in the dark part of the sky. It has a stellar luminance of about -12 on the scale. I would figure you would need about -18 or so to have a "bright light" that would capture people's attention in broad daylight.
The approximate power required would be about 20 lux (lumens per square meter) incident on the surface, which is about 100mW per square meter.
The total coastline of places like Indonesia is hard to estimate, but it is somewhere around 60,000km. Assume 1/4 would be affected by a large non-localized tsunami and you're signaling to an area of coastline around 15,000km.
Presuming you can paint the coastline with a precise beam, say... all area within 500 meters from the water. Lets also say you're using a flashing with a 25% duty cycle (it's only on about 1/4 of the time), you're looking at 15000/8= 1800 square km or about 1.8 billion square meters "painted" at any given time.
With laser efficiency around 65% (in the best high output research lasers) and the power required around 100mW per meter incident on the surface and atmospheric losses around 40% (60% efficiency)...
((1.8b *.1) / (.65)) /.6 = 461.7 MegaWatts
Lets limit this to populated areas, say 10% of the coast. We're down to 46.2 MW.
Since the sun in space hits with about 1200W/m2, and given about 40% cell efficiency, we need about 96 square kilometers of solar cells, or about 100 4-ton steam turbines in a reactor (whether nuclear or otherwise).
Keep in mind, we're just looking at the coast of Indonesia....
Lets assume only 5% of the coast is occupied, that will reduce our power need to 23mW (only a few square KM of solar cells). But considering all the populated coastline in the Atlantic for an event like the proposed Azores landslide tsunami, lets multiply by 20.
Regardless, we're in the "entire power output of multiple massive reactors" sort of range, not the "strap it to a rocket and shoot it into orbit" sort of size.
A mirror uses the power of the sun 100w/m2 to signal over a small area (maybe a few feet).
You're talking about matching that power over a hundred thousand square miles?
Wow.
You're just not understanding the scale, I think. My flash will burn your eyes out from 5 feet away, but from the upper level of a stadium, wouldn't even make the slightest dent in the illumination. From a mile away, I don't know if it would be bright enough to get someone's attention who wasn't already staring in the right direction.
From 30,000km, it wouldn't even be close to visible.
Understanding the power of the sun, the scale of distance and the scale of the target area... Go try some experiments with lasers. They're cool, but they're not that cool. 1Kw is a lot of output for a satellite. I would wager that even a fine-beam focus from a 1kW laser on just a few hundred meters of surface would have trouble penetrating the atmosphere and being strong enough to capture someone's attention in daylight from 30,000km.
How is this something that can be replicated over.. say... 10,000 square km? You're talking terawatts of power....
As someone pointed out earlier, the island of Hawaii receives more sunlight energy than the entire output of all human power production combined... How do you even remotely close to match this?
What if it's a cloudy daytime. That would be like multi-terawatt lasers... To penetrate daytime clouds and still produce a bright light over an area of several thousand Km.
Are you assuming this would only work on cloudless nights?
How does a "warning system" that only works 15% of the time in some areas sound like a good idea to you?
Even providing you could produce enough power to make a "bright star" (which you can't), have you considered daytime (when you DO have to outshine the sun, indirectly at least) AND local weather.... during the monsoon season in some areas (or in places like British Columbia in winter), people don't see the open sky for weeks at a time.
It doesn't even seem worth thinking about, let alone expending significant effort on.
In order to make the "flashing light" appear as anything, it has to be several orders of magnitude brighter than whatever else it is around. If the sun is overhead, then it has to be brighter than the sun.
Go tell your local fire department to park their truck in a parking lot in broad daylight and tell me if the lights flash off the walls. They don't. Trust me.
In order to make it visible from the area affected by a tsunami (several thousand km of coastline, at least)....
my god this whole discussion is inane. You've OBVIOUSLY never done any experimental work with daytime lighting, or photography.
As a former professional photographer, in order to adequately light up an area (brighter than direct sunlight) with a flash in broad daylight, we're looking at a flash strong enough to have physical concussion on your hand. My bigger flash heads can give you an instant flash-burn if you were to stand directly in front of it, but will only give me about 20-30 feet of range in broad sunlight.
The absolute power of sunlight is profoundly stronger than most people realize. The amount of light in a shaded area in daylight is 8-10 times less than in direct sun. The amount of light during twilight is 20-30 times less than in broad daylight.
The efficiacy of illumination also follows the inverse square rule, where moving away from the source reduces the light in an exponential manner, not a linear one (obviously, this isn't quite the same for a laser, but regardless)...
Go take a pen laser outside and shine it on the sidewalk where the sun shining.
Try taking a maglight (which can be visible from hundreds of feet at night) and stand 40 feet away from someone who is not looking, and try to use it to get their attention. It simply won't work. The daytime is too bright.
And frankly, a warning system that requires people to notice a faint, flickering star in the sky that wasn't there the previous night might be problematic, especially many areas of the tropics (where tsunamis are most common) are cloudy almost 80% of some seasons.
I think the issue is that the judges and court officials who know well enough recognize that they're not really a serious danger, enough to justify life in prison.
However, people who don't know any better freak out when they find out one lives x hundred feet from the playground and threaten to not re-elect John City Council if he doesn't institute regulations on where they live.
This is probably where this legal limbo comes from. I think it's just the result of soccer moms freaking out and leaning into city council members who dream about being state senators some day.
The only libel lawsuit I've ever heard of in the AGW arena is the one mentioned below of a skeptic suing a legitimate scientist after badly twisting some facts around to try to prove a point....
If you look at the propaganda of the day, it was actually strongly focused against Mexican migrant workers, who were the largest profile users of the day and (just as today in some circles) regarded to be a blight on the American countryside.
I agree the DOW Chemical line is probably not the primary cause (even if it might have been a small contributor).
There are some provisions of the DMCA that indemnify an ISP that is merely a "conduit" of information.
quoting wikipedia:
The Online Copyright Infringement Liability Limitation Act (OCILLA) is United States federal law that creates a conditional safe harbor for online service providers (OSPs, including Internet service providers) and other Internet intermediaries by shielding them from liability for the infringing acts of others. OCILLA was passed as a part of the 1998 Digital Millennium Copyright Act (DMCA) and is sometimes referred to as the "Safe Harbor" provision or as "DMCA 512" because it added Section 512 to Title 17 of the United States Code. By exempting Internet intermediaries from copyright infringement liability provided they follow certain rules, OCILLA attempts to strike a balance between the competing interests of copyright owners and digital users.
The Devils advocate position is that by requiring customers to wait for arbitrary showtimes and having an arbitrary limited selection pretty significantly impedes the flow of copied materials.
If I want to watch "Uncross the Stars" tonight, I don't have any way of doing that other than paying the movie companies (or downloading it).
In fact, I would wager that said movie will never be aired on any sort of television station that many people have.
So, while the concept of suing customers is unpalatable to me, as well as you, I disagree that it's "exactly the same thing" as a VCR.
Yeah, I was thinking a national health system akin to Canada or Norway or Sweden or Finland or Denmark (all of whom rank higher in both median income and 'quality of living' in every single world economic survey than the US).
But, you have to remember that the only reason we DONT ALREADY HAVE (as a successor to the Patriot Act) a national ID card was resistance from the liberal democrats.
Now, I would think it might pass.... But I have a feeling the republicans are too busy trying to stick their thumb in Obama's eye to actually care about what the content of the bills are anymore.:-)
Warren Buffet is very fond of pointing out that he pays a much lower tax rate (17%) than his secretary (27%).
I dunno. I think this whole tax issue is a straw man set up as a way to undermine politicians rather than a legit beef. 3% tax on top of the worlds lowest tax rate in a developed economy does not to me seem like revolutionary "Marxist" policy.
Or those who want a political victory so that they can garner support for their favorite politician who espouses their particular brand of religion....
which I think might be the most common out of these.:-)
Do you ask Warren Buffet that question? He's a big advocate of higher and stricter taxation for the super-rich. The color of his sky is OBVIOUSLY green.
Slashdot Mirror
I was already assuming a 25% duty cycle (flashing aka moving the laser). I don't think you can trim it more than that without increasing the power required to make it noticeable to the naked eye. But we're still talking about a faint flashing in the sky... Not anything that demands attention.. just something subtly noticeable.
The 100mW figure was based on the brightness of the moon in the daytime sky. Surely not bright, but at least visible. Maybe 10x more would be better for people to stop and notice it...
But 1kw lasers are considered pretty high power, so we're still off by a factor of 100 or 1,000...
I dunno... Just for indonesia...
Unless you're an actor unfamiliar with the metric system who decides it's cooler to mispronounce things for artistic effect in a bad 1980s movie!
The realities of using a laser for this is just stupid.
The reality of "computer vision" for example was "wow, that's impossible with current technology, but it sure would be cool if we could figure out how".
This whole laser bit runs into issues of physics. We know how much light is lost in the atmosphere and how much power is lost in a laser ocilator and how much energy is output by the sun.
Even given 100% perfect efficiency on all of those, you're talking about 100 square kilometers of solar panels.
or... 10GW hours worth of batteries... yes. *chuckles* Unless we're talking about an antimatter reactor, that's still outside our capabilities. our best lithium polymer batteries get about 10 watts per pound. So... 1 billion pounds of batteries *chuckles*. Or 900 million tons of hydrogen fuel cells.... We would only need a few ounces of antimatter, given a perfect conversion. Or a couple of hydrogen bombs perfectly harnessed all at once.... right.
The idea of wide ranging signalling for tsunamis is interesting. The idea of using a geostationary laser is not. It's kinda funny actually.
The sun casts 1200W/m2 on objects in space. That's about 20% more than on the surface.
It's not magic sauce, it's just 20% more efficient. Whoever said that about China was an ignorant tool.
To get 25GW, you would need ten thousand square km of solar panels. Solar wind isn't a substitute for reality. :-)
To better address your question and lay a bit more clarity to it...
If a person were... say... flying... and they were up in the sky right next to the sun. Do you think a mirror in their hand would make them visible?
A mirror signaling is effective because it's done against the backdrop of the ground, which is not quite so bright as the sky, especially the sky immediately surrounding the sun.
How, dare say, do you propose to move the sattellite around when it happens to be directly in line with the sun, so as to be completely invisible.
Oye, there's so many parts of this that are just stupid.
I'm done... moving on...
good luck with your idea there, sparky.
Aside from this not working when it's cloudy, this also doesn't work when the sun is high in the sky. This is system is totally borked from 10am-6pm when the sun is up high in the sky and you won't see a flashing light against that backdrop, no matter how bright it is...
Oye...
To follow up with this, i did some research.
The full moon is quite visible during the day, but only if it's in the dark part of the sky. It has a stellar luminance of about -12 on the scale. I would figure you would need about -18 or so to have a "bright light" that would capture people's attention in broad daylight.
The approximate power required would be about 20 lux (lumens per square meter) incident on the surface, which is about 100mW per square meter.
The total coastline of places like Indonesia is hard to estimate, but it is somewhere around 60,000km. Assume 1/4 would be affected by a large non-localized tsunami and you're signaling to an area of coastline around 15,000km.
Presuming you can paint the coastline with a precise beam, say... all area within 500 meters from the water. Lets also say you're using a flashing with a 25% duty cycle (it's only on about 1/4 of the time), you're looking at 15000/8= 1800 square km or about 1.8 billion square meters "painted" at any given time.
With laser efficiency around 65% (in the best high output research lasers) and the power required around 100mW per meter incident on the surface and atmospheric losses around 40% (60% efficiency)...
((1.8b * .1) / (.65)) / .6 = 461.7 MegaWatts
Lets limit this to populated areas, say 10% of the coast. We're down to 46.2 MW.
Since the sun in space hits with about 1200W/m2, and given about 40% cell efficiency, we need about 96 square kilometers of solar cells, or about 100 4-ton steam turbines in a reactor (whether nuclear or otherwise).
Keep in mind, we're just looking at the coast of Indonesia....
Lets assume only 5% of the coast is occupied, that will reduce our power need to 23mW (only a few square KM of solar cells). But considering all the populated coastline in the Atlantic for an event like the proposed Azores landslide tsunami, lets multiply by 20.
Regardless, we're in the "entire power output of multiple massive reactors" sort of range, not the "strap it to a rocket and shoot it into orbit" sort of size.
To quote Mr Scott.
"WE SIMPLA DONT HAVE THE POWER KEPTIN"
A mirror uses the power of the sun 100w/m2 to signal over a small area (maybe a few feet).
You're talking about matching that power over a hundred thousand square miles?
Wow.
You're just not understanding the scale, I think. My flash will burn your eyes out from 5 feet away, but from the upper level of a stadium, wouldn't even make the slightest dent in the illumination. From a mile away, I don't know if it would be bright enough to get someone's attention who wasn't already staring in the right direction.
From 30,000km, it wouldn't even be close to visible.
Understanding the power of the sun, the scale of distance and the scale of the target area... Go try some experiments with lasers. They're cool, but they're not that cool. 1Kw is a lot of output for a satellite. I would wager that even a fine-beam focus from a 1kW laser on just a few hundred meters of surface would have trouble penetrating the atmosphere and being strong enough to capture someone's attention in daylight from 30,000km.
How is this something that can be replicated over.. say... 10,000 square km? You're talking terawatts of power....
As someone pointed out earlier, the island of Hawaii receives more sunlight energy than the entire output of all human power production combined... How do you even remotely close to match this?
Lighting up the daytime sky across the entirety of a major ocean coastline would cost a lot more than hundreds of millions of dollars. :-)
What if it's a cloudy daytime. That would be like multi-terawatt lasers... To penetrate daytime clouds and still produce a bright light over an area of several thousand Km.
This is just ROFL.
Radar is used for this purpose. It also penetrates clouds.
Using a laser from orbit for anything other than curiosity experiments is just inane.
It's cloudy 80% of half the year in Indonesia (monsoon).
What about this system is remotely practical enough to even consider?
Are you assuming this would only work on cloudless nights?
How does a "warning system" that only works 15% of the time in some areas sound like a good idea to you?
Even providing you could produce enough power to make a "bright star" (which you can't), have you considered daytime (when you DO have to outshine the sun, indirectly at least) AND local weather.... during the monsoon season in some areas (or in places like British Columbia in winter), people don't see the open sky for weeks at a time.
It doesn't even seem worth thinking about, let alone expending significant effort on.
*slaps forehead*
You're an idiot.
In order to make the "flashing light" appear as anything, it has to be several orders of magnitude brighter than whatever else it is around. If the sun is overhead, then it has to be brighter than the sun.
Go tell your local fire department to park their truck in a parking lot in broad daylight and tell me if the lights flash off the walls. They don't. Trust me.
In order to make it visible from the area affected by a tsunami (several thousand km of coastline, at least)....
my god this whole discussion is inane. You've OBVIOUSLY never done any experimental work with daytime lighting, or photography.
As a former professional photographer, in order to adequately light up an area (brighter than direct sunlight) with a flash in broad daylight, we're looking at a flash strong enough to have physical concussion on your hand. My bigger flash heads can give you an instant flash-burn if you were to stand directly in front of it, but will only give me about 20-30 feet of range in broad sunlight.
The absolute power of sunlight is profoundly stronger than most people realize. The amount of light in a shaded area in daylight is 8-10 times less than in direct sun. The amount of light during twilight is 20-30 times less than in broad daylight.
The efficiacy of illumination also follows the inverse square rule, where moving away from the source reduces the light in an exponential manner, not a linear one (obviously, this isn't quite the same for a laser, but regardless)...
Go take a pen laser outside and shine it on the sidewalk where the sun shining.
Try taking a maglight (which can be visible from hundreds of feet at night) and stand 40 feet away from someone who is not looking, and try to use it to get their attention. It simply won't work. The daytime is too bright.
And frankly, a warning system that requires people to notice a faint, flickering star in the sky that wasn't there the previous night might be problematic, especially many areas of the tropics (where tsunamis are most common) are cloudy almost 80% of some seasons.
This whole topic is just idiotic.
What if it was your daughter? Your wife? Your son? You'd still think it was 'unfair' to ban him from a computer? Seriously?
If my daughter decided to be an FBI agent running stings, and was this guy's victim, I'd be proud of her for doing her job well...
what was the point again?
I think the issue is that the judges and court officials who know well enough recognize that they're not really a serious danger, enough to justify life in prison.
However, people who don't know any better freak out when they find out one lives x hundred feet from the playground and threaten to not re-elect John City Council if he doesn't institute regulations on where they live.
This is probably where this legal limbo comes from. I think it's just the result of soccer moms freaking out and leaning into city council members who dream about being state senators some day.
The only libel lawsuit I've ever heard of in the AGW arena is the one mentioned below of a skeptic suing a legitimate scientist after badly twisting some facts around to try to prove a point. ...
And what was your point exactly?
If you look at the propaganda of the day, it was actually strongly focused against Mexican migrant workers, who were the largest profile users of the day and (just as today in some circles) regarded to be a blight on the American countryside.
I agree the DOW Chemical line is probably not the primary cause (even if it might have been a small contributor).
There are some provisions of the DMCA that indemnify an ISP that is merely a "conduit" of information.
quoting wikipedia:
The Online Copyright Infringement Liability Limitation Act (OCILLA) is United States federal law that creates a conditional safe harbor for online service providers (OSPs, including Internet service providers) and other Internet intermediaries by shielding them from liability for the infringing acts of others. OCILLA was passed as a part of the 1998 Digital Millennium Copyright Act (DMCA) and is sometimes referred to as the "Safe Harbor" provision or as "DMCA 512" because it added Section 512 to Title 17 of the United States Code. By exempting Internet intermediaries from copyright infringement liability provided they follow certain rules, OCILLA attempts to strike a balance between the competing interests of copyright owners and digital users.
The Devils advocate position is that by requiring customers to wait for arbitrary showtimes and having an arbitrary limited selection pretty significantly impedes the flow of copied materials.
If I want to watch "Uncross the Stars" tonight, I don't have any way of doing that other than paying the movie companies (or downloading it).
In fact, I would wager that said movie will never be aired on any sort of television station that many people have.
So, while the concept of suing customers is unpalatable to me, as well as you, I disagree that it's "exactly the same thing" as a VCR.
Yeah, I was thinking a national health system akin to Canada or Norway or Sweden or Finland or Denmark (all of whom rank higher in both median income and 'quality of living' in every single world economic survey than the US).
But, you have to remember that the only reason we DONT ALREADY HAVE (as a successor to the Patriot Act) a national ID card was resistance from the liberal democrats.
Now, I would think it might pass.... But I have a feeling the republicans are too busy trying to stick their thumb in Obama's eye to actually care about what the content of the bills are anymore. :-)
Loopholes still exist.
Warren Buffet is very fond of pointing out that he pays a much lower tax rate (17%) than his secretary (27%).
I dunno. I think this whole tax issue is a straw man set up as a way to undermine politicians rather than a legit beef. 3% tax on top of the worlds lowest tax rate in a developed economy does not to me seem like revolutionary "Marxist" policy.
Shrug
Or those who want a political victory so that they can garner support for their favorite politician who espouses their particular brand of religion....
which I think might be the most common out of these. :-)
wow. This IS Slashdot, but i don't think ANYONE read TFA
Do you ask Warren Buffet that question? He's a big advocate of higher and stricter taxation for the super-rich. The color of his sky is OBVIOUSLY green.