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Why Protesters In Cairo Use Laser Pointers
New submitter Ahmed Shaban writes "Why do protesters in Cairo use laser pointers? At the beginning, they were used to light up snipers on rooftops. Later, it just became fashionable to use them, and such things spread very fast among the youth of Cairo, who can find the high power laser pointers for sale on the sidewalks. The article contains amazing photos of a chopper lit up by green laser pointers."
No. Laser tag have fog machines.
Atmospheric effects like fog machines and hazers are why you can see them in Laser tag.
You can see the ones in the Egypt videos because they're just really powerful. Far more powerful that what is legally available in the USA without a variance.
09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0 is the magic number.
With the Egyptian military completely on board with the protesters this time around, I guess the laser pointers dont have much actual purpose anymore.
Its actually quite remarkable what is happening there. More people were protesting than had voted for the president because the president decided that their constitution didnt apply to him, so the military takes down the president in response but remarkably doesnt assume power.
How many countries actually have a military that would do this sort of thing? I'm fairly certain that mine, with a military that runs an agency well known now for violating the constitution, would not.
"His name was James Damore."
Anyone want to invest in a cataract treatment center in Cairo, they're going to need it in a few years...
I know the 'copters are being illuminated by hand-held laser pointers but the photographs do look like those produced by Michael Yon http://www.michaelyon-online.com/the-kopp-etchells-effect.htm showing the Kopp-Etchells Effect https://en.wikipedia.org/wiki/Helicopter_rotor.
...are the moronic A/Cs on /. who seem happy to denigrate the Egyptian people for celebrating the peaceful overthrow of a useless leader.
The fact that the army has removed these incompetants and are immediately handing power back to the people is un-precedented and incredible. The Egyptian people and army could teach some other nations a thing or two, I think, not to mention some of the ignorant bigots who plague /.
Smivs on the intertubes!
The military is on their side!...
Aren't these the same people that shoot live bullets in the air to celebrate? Maybe lasers are somewhat less dangerous...
A single green laser is very disorienting. There are a number of videos on Youtube which shows it. Military provide pilots with goggles which filter out that particular wavelength.
Technically they did have democracy and got what they voted for, but what they didn't have were safeguards to ensure that a president couldn't just declare himself dictator for life after being elected. And so that's what he tried to do as early as possible. They need to adjust their system, institute checks and balances, constitutional changes requiring national referendums etc.
You use your cat to confuse riot police?
Most laserpointers are 1mW or less, so they don't reflect enough particulates in the air unless it's foggy. The green ones in the video are usually at least 5mW, which is powerful enough to reflect off enough dust in the air to be visible under normal conditions.
It's one of the big errors that scifi movies have with lasers in space combat (the other error being that laser pulses move slow enough to be seen). even with insanely powerful lasers, they'd be practically invisible in space because there's nothing for them to reflect off. Unless, of course, you want to pretend that all laser space battles take place in dust or gas clouds...
Agreed. We use 10mW and 20mW green lasers for star pointing in astronomy. They're clearly visible to nearby users but get more than about 10-20ft away and that's no longer the case. Judging by the pictures in TFA the ones the protestors were using were probably in the 150mW+ range.
The Geneva Convention only applies to consenting militaries.
while(1) attack(People.Sandy);
My understanding is that they didn't really have much of a choice in who to vote for. It was between a known bad guy and a probably bad guy, so they went with the latter due to lack of choices to begin with. Is it really a free and democratic election if you don't have choices?
Police and cats have much in common
1) They both enjoy stalking weaker prey
2) They both enjoy toying with their prey
3) They both have a love/hate relationship with lasers
4) There's tons of videos on YouTube of them both doing dumb things
If lasers are being sold for cheap on the street, odds are good that they're producing a wide range of wavelengths. The cheaper the laser, wider the range of wavelengths it emits. It's one of the reasons better lasers come with an IR filter to help reduce accidental blinding of observers.
Um, no. Not enough to say so, at least.
What makes a laser a laser is that it is a single wavelength. The light amplification process itself only works on a specific wavelength, and weeds out other light. You have to put extra circuitry into a laser to get it to produce a wider range.
Used to; I stopped when the changed something about the composition of their vests and the cat started to fart like crazy after eating a few.
Seems the same in US too..
I was in the dorms at college when Obama was elected for the first time. His supporters rioted and caused a bunch of property damage and ruffed up people.
There's also been cases of sports fans rioting when their team has won.
People do crazy shit to celebrate that just seems counterproductive to an outside observer.
If it were so easy, many South American countries would have become as prosperous and democratic as the US since their constitutions were basically copies of the US Constitution. Yet, somehow, it didn't really work.
You can see the same in many former British colonies. If you read their Constitution, you'll see that they're not much different from what you find in any modern democracy. Bill of rights, checks and balances, constitutional protections for both negative and positive rights. They also inherited the common law tradition and much of their legislation is copy-pasted from UK legislation circa 1960. It's so similar in theory that UK-trained lawyers can usually practice with minimum to nil extra training, as most of the legal education is done from UK textbooks and case books anyway.
Yet, in practice, it's quite different. Sure, you have the same theoretical protections, but they do little good when everyone is free to ignore them. It's nice to tell the courts that they have to be independent and fair, but how do you guarantee that?
"They need to adjust their system, institute checks and balances", etc. is all wishful thinking. It's about as useful as telling a developing country that all they need to do is grow. It's true but pretty useless as far as advice goes. The tricky part is knowing how to move from the equilibrium where the law is widely ignored, where formal checks and balances don't work, where the constitution is not worth the paper it's written on, to a better equilibrium. As far as I can tell, no-one has yet found a magic recipe for that because things are usually the way they are for a reason. It's not like bad institutions just spring up at random: they are usually people who have an interest in maintaining the status quo, and we were able to see times and times again that removing whoever happens to be in power doesn't do much to solve the structural problems and can even lead to worse outcomes (Iraq? Libya?).
If an aircraft is on auto-pilot, there's negligible risk.
If an aircraft is currently under human control while cruising, there's a slight risk.
If an aircraft is under human control while taking off, landing or performing any sort of maneuver, there's a reasonably significant risk.
Have you ever had someone shine a bright flashlight in your face? It's a lot like that. It causes you to jerk away, confuses you, and partially blinds you for anywhere from a few seconds to several minutes. Any of those can be deadly given that the person with the laser probably doesn't know if the aircraft is on autopilot or is preparing to land.
It's one of those laws where, sure, 98% of the time nothing bad will happen if you do it. But that last little bit of a time, something *really* bad could happen. So it's a felony.
Nope, just mail order that mofo. These guys sell 1W+ blue lasers:
Wicked Lasers -- any colour, any power, get em before they're gone.
---
ECHELON is a government program to find words like bomb, jihad, plutonium, assassinate, and anarchy.
Some laser pointers do put out IR wavelengths as a byproduct of the way they're built. Low-power laser pointers aren't a problem, the IR simply isn't powerful enough to do anything. But with 100mW+ laser being sold to ordinary people, there is a very real IR hazard from cheaply-made badly-filtered (or not filtered at all) laser pointers, especially green laser pointers.
The reason it's so dangerous is that unless you have special dual-wavelength safety glasses, they'll only filter out the visible light, leaving the IR output to wreck havok on your eyes.
http://en.wikipedia.org/wiki/Laser_pointer#Infrared_hazards_of_DPSS_laser_pointers
Eat the rich.
"The pilot should have bailed out and let the damned thing crash into the crowd."
Pilot bailing out....of a conventional helicopter.
And to think /. was once a techy site.
"This post is an artistic work of fiction and falsehood. Only a fool would take anything posted here as fact."
It's one of the big errors that scifi movies have with lasers in space combat (the other error being that laser pulses move slow enough to be seen).
If you had asked me, I would have said that it was lasers makes pew-pew noises in space.
When information is power, privacy is freedom.
You can see the ones in the Egypt videos because they're just really powerful. Far more powerful that what is legally available in the USA without a variance.
You didn't read the article at all did you?
As crowds packed Tahrir Square in the centre of Cairo to celebrate the overthrow of President Mohammed Morsi on Wednesday night, three things filled the air - noise, fireworks and, unusually, laser beams.
Fireworks make lots of smoke
So you have experience from flying a helicopter (blindfolded)? I don't believe the remaining senses are enough to be able to fly.
It's all fun and games, 'til someone loses an eye.
We used to have a Bill of Rights. Now, with the rights gone, all we have left is the bill.
Egyptians revere cats.
So obviously they are fascinated with laser pointers as well.
Troll is not a replacement for I disagree.
Is that not the textbook definition of a coup d'etat?
Just because a government is democratically elected doesn't mean it's a democracy. History is full of democratically elected governments that then turn into totalitarian regimes.
If Obama woke up tomorrow and ordered that all Tea Party members be arrested, I would expect our military to essentially remove him from office - in the immediate case by ignoring him, and in the longer case by Congress impeaching him and removing him from office - which would still require the cooperation of the military (they'd have to decide to listen to Congress and not the President.)
In Egypt, there isn't really a constitutional mechanism to get rid of a leader who, while democratically elected, isn't fulfilling his responsibilities as a democratic leader, so the best thing they have is the Army takes care of it.
So while this may technically be a coup in that the elected leader is being removed from office through a non-elective means, it's not necessarily undemocratic, if you believe the elected leader is abusing the freedoms of the people and the coup is to create the opportunity for someone who does respect the rights of the people to be elected.
paintball
It's one of the big errors that scifi movies have with lasers in space combat (the other error being that laser pulses move slow enough to be seen). even with insanely powerful lasers, they'd be practically invisible in space because there's nothing for them to reflect off. Unless, of course, you want to pretend that all laser space battles take place in dust or gas clouds...
Thus the use of sandcasters in the Traveller RPG. Basically dump bags of sand into space around your ship to absorb/reflect any laser weapons.
'The tyrant will always find pretext for his tyranny.' - Aesop's Fables
Space is full of dust on an astronomic scale. On a scale relative to humans, it's a void. When projecting a narrow beam of light through space, the odds of it hitting enough dust to give a visible reflection to an observer is pretty small. The average density of space* is around one atom per cubic centimer. That means you would have to project a laser with a 1cm diameter about three million kilometers before it interacted with enough atoms to constitute a single single spec of dust. That's nearly eight times the distance of the Earth to the moon.
Of course, it might hit high density dust pockets, but those are fairly far about and would just be seen as a few glimmers of light between the projector and the target, certainly not enough to make any sort of line as projected in Science Fiction.
* http://hypertextbook.com/facts/2000/DaWeiCai.shtml
It's one of the big errors that scifi movies have with lasers in space combat (the other error being that laser pulses move slow enough to be seen
But combine those two errors, and we have a bit less of an error - Simply one of nomenclature rather than physics.
Pulses of light like we see in the movies would would more likely come from some sort of particle beam. It would travel slower than the speed of light, and most likely radiate energy during its trip (thus making it visible from the side).
Of course, I don't particularly expect that Hollywood grasps either point, they just like cool glowy weapons that also happen to make noise.
Enough energy to vapourize a ship would have enough energy to create particle/anti-particle pairs all along its length. The creation/annihilation of these particles would give off radiation in all directions.
When our name is on the back of your car, we're behind you all the way!
+1 for the Traveller reference. Brings back memories.
Are agnostics skeptical of unicorns too?
I am sorry but you are plain wrong! "Enough energy to vapourize a ship" can be achieved with an infrared laser (photons of energy below 1 eV). Even if you allow for multiphoton interactions it is orders of magnitude below the threshold for the pair creation (1.02 MeV for electron-positron) . There aro no lasers that produce photons in MeV range. Also, the annihilation of electron and positron, which is the lowest energy particle-antiparticle anihilation, produces gama photons ~.51 MeV which are quite invisible to humans.
What makes it a laser is how the light is produced. In most cases the lasers available to consumers are just very bight lamps with narrow bandwidth, good collimation, and not monochromatic.
It takes extra care to build a laser that produces only one frequency and even more care for the output to be coherent for any distance which is why holography and interferometry have problems with solid state lasers and gas laser are still used.
Well, if you actually want to blind someone, you aim it properly and use it in a pulsed mode. Much lesser chance of hitting something you didn't intend to. But of course, the "enraged crowd" part is kind of at odds with playing nice.
Ezekiel 23:20
I thought some sci-fi got around that by saying those beams weren't lasers at all, but instead were plasma or perhaps something altogether different. According to Star Trek canon, for instance, their beams are "phasers" which are actually FTL; in a battle between FTL-capable ships, lasers would be pretty useless after all since the ships could easily outrun the lasers.
Morsi tried to "declare himself dictator for life after being elected."
Sorry, but citation needed. I've been Googling for this and can't find him guilty of anything above rank incompetence.
If anybody can show me what he did that was so bad other than being a crap leader or vague accusations of being devious and manipulative (of course he is! He's a frikkin' politician!) I'd love to see it.
The most factual account I can find is here where author Esam Al-Amin says:
"The people in Egypt went to the polls at least six times: to vote for a referendum to chart the political way forward (March 2011), to vote for the lower and upper house of parliament (November 2011-January 2012), to elect a civilian president over two rounds (May-June 2012), and to ratify the new constitution (December 2012). Each time the electorate voted for the choice of the Islamist parties to the frustration of the secular and liberal opposition.
"To the discontent of the Islamists, all their gains at the polls were reversed by either the Mubarak-appointed Supreme Constitutional Court (SCC) or the military."
I'm really trying not to be a troll but people keep saying that Morsi wanted to become a dictator but I can't find any stories of him doing anything other than breaking election promises. In my country, that's considered pretty normal and no cause for a coup.
--- "We've always been at war with Eastasia."
Well... it sounded good until someone started clouding the issue with facts. :-)
When our name is on the back of your car, we're behind you all the way!
People bring up the Lincoln thing all the time (usually it's some bitter old southern racist who still hates Republicans for their "war of aggression" against his slave-owning grandpappy and who is angry the rest of the Democrats have moved-on...) but Lincoln was in an utterly unique situation (for the U.S.) which was that half the country, including parts of the military, had broken-off to form their own country over their demand that they had the right to own, and treat like cattle, another chunk of the population. At that moment in time, with even many families split by the war and brothers fighting against brothers, Lincoln was in a place never contemplated by the Constitution. if Half of America was currently Muslim-Brotherhood-aligned, blowing-up buildings and bridges, openly fighting the US military in cities around the country with hundreds of thousands of dead people and the US Military actually losing some of the battles, not many sane people would criticize a President for taking Lincoln-style actions. The criticisms of Bush43 and Obama is that they have undertaken many actions more severe than Lincoln did but without facing a threat anywhere near what Lincoln faced.
Lincoln was a good man, and his cause was entirely just. The founders of the nation tolerated slavery in the south as part of forming the union to fight for independence from King George... but they wrote at the time that they expected slavery to come to a natural end on its own. By 1860, however, it was quite clear that the Democrats were never going to give-up on owning black people and indeed they were demanding that new states added to the union be slave states. When Lincoln was elected, running as an opponent to slavery, the Democrats went crazy and split the nation over the fear he would free their slaves. They were dirtbags who deserved to lose the war. I hate sugar-coating. I'm sure some Democrat, unable to handle the truth, will flag this as a troll post... but it is a provable, well-documented FACT that no Republican ever owned a slave and nearly every slave owner was a Democrat. Indeed, after the war, it was Democrats who formed the KKK and one of the groups the KKK targeted for violence was Republicans (these too are documented FACTS.... as is this: Many Democrats currently sitting in the US Senate have knowingly cast at least one vote to have as their party Senate leader an actual Klan member (the Late Dem. Sen. Robert Byrd)).
Although atmosphere does reduce the power, it's columnated light and in a vacuum anyway it would not lose any of its power. Dust, fog, humidity in the air will lower the power, but also cause you to be able to see the beam in the air. If you can't see the beam of a laser, it's likely delivering very close to 100% of its output power on target.
Years ago, when laser pointers were expensive, I had a 5mw red laser that we tested at 1/4 mile. It lit up an entire dumpster very nicely. (lenses weren't that good back then, it wouldn't hold a point for more than 25 feet or so, and TONS of scatter)
But on the other issue of power, just because it's a laser doesn't make it any more destructive than something else of the same power. A 100w lightbulb puts out 100x the power of a 1w laser pointer. And you don't see lightbulbs catching helicopters on fire. (even if focused in a spotlight) The only reason 1w lasers catch paper on fire is they're concentrating 1w of power into a 2mm x 2mm area. That would probably feel like a match at 1/2", enough to light paper. That's not going to melt metal obviously, at any range. The laser just lets you project that "half inch from a match" out several hundred yards. It doesn't make it more (or less) intense.
Somewhat back on topic though... wow.... that flight had to SUCK for those helicopter pilots. Someone hits one 727 with a laser pointer and the whole city loses their mind and the swat team rolls. That heli looks like it had 3-4 dozen green and at least two blue pointed at it. They would have to be out of their minds to look down except through cameras, and imagine the refractions going on inside the cockpit, with greens and blues scattering off all the shiny things. I bet that is an incredibly effective deterrent for the pilots.
Ironic, they sent in the helicopters as a show of force, and got driven off by the demonstrators using cheap, commonly available tech. Sort of like making the water canon truck leave by throwing rocks at it. Embarrassing.
I work for the Department of Redundancy Department.
Interestingly enough, the crowd on Tahrir square was actually cheering the military on. Every time the helicopters showed up it was cause for celebration. The crowd likely had no idea that they were annoying the pilots.
That sounds implausible to me. In fact I used to work with low-power (could put your hand in the beam without feeling it) IR lasers in college and we needed extra safety gear specifically because a stray beam could be shining into your eye without you noticing until serious permanent damage began to set in.
It may not cause dazzle or other forms of temporary blindness due to over-stimulated rods and cones, but except in extreme cases I believe such damage usually repairs relatively quickly, but its no less dangerous for permanent damage (actually cooking the lens or retina). More so in fact because you don't know to look away and your pupils won't constrict to block out the excess.
Where it unquestionably is safer is legally - because nobody will notice the source, and any damage inflicted will likely not be dramatic enough to associate with a specific event.
--- Most topics have many sides worth arguing, allow me to take one opposite you.