The siphon in the experiment stopped working when the pressure was reduced below 0.18 atm. The water was not boiling, the air pressure was just no longer enough to get the water over the 1.5 meter high apex.
Liquid doesn't pull (at least not much), but you can get an effect much like a pull if there's enough pressure on the other side. The pressure at the apex is not negative, it's just lower than atmospheric.
Mod this up insightful, I don't know who modded it down. Indeed, a siphon can't reach 33 feet. And in the nature experiment, it couldn't even reach 1.5 meters anymore once air pressure was reduced below 0.18 atm. So air pressure is needed for a siphon to work.
Siphons stop working if the atmospheric pressure is too low. What's important is not the difference between atmospheric pressure on both sides (which is negligible), but the fact that there's enough atmospheric pressure to push the water into the siphon on any side. The experiment in Nature showed that the siphon turned into a double barometer when the atmospheric pressure was too low. So yes, air pressure does have someting to do with it.
Water doesn't pull (at least not much). Atmospheric pressure is pushing the water in from both sides, like two connected barometers. The barometer that has to push the water up over the lowest height difference (i.e. the side of the high reservoir) is the one that wins the fight, so water flows from that side to the other. If the height is too high, the barometers no longer meet and the siphon turns into a double barometer with vacuum or some water vapour in between. Boiling doesn't really have much to do with it, with mercury for example you'd just get a vacuum like the one you have in a mercury barometer.
I gave a slightly longer explanation, explained differently, here.
The shorter column is not "dragged up", you can't drag up more than a small droplet of water. The water in the shorter column is actully pushed up by atmospheric pressure just like in a barometer. Reduce the atmospheric pressure like in the experiment referenced in the article, and the water breaks up when the pressure gets too low (0.18 atm for a 1.5 meter apex).
In fact it's not even wrong to say that air pressure makes a siphon work. If you look at it a certain way, it kind of does. It's like two connected barometers that are fighting each other, with gravity helping the higher one. Take away the atmospheric pressure, and it no longer works.
Nope. Strange how many people get this wrong, it's really not that complicated.
The water doesn't work like a chain, the cohesion of water is only just enough to hold a drop of water together, certainly not enough to pull a whole column of water along through a siphon. The motion is caused by gravity BUT atmospheric pressure is needed as well (as shown in the actual experiment that was referenced in the Slashdot summary and described in more detail in Nature). Here's how a siphon acually works:
Suppose you have a source reservoir and a destination water reservoir, with the water level of the destination lower than that of the source. The reservoirs are connected by a tube that goes from the source reservoir up to an apex above both water levels and then down into the destination reservoir. The tube is filled with water (you have to start the siphon somehow by filling it with water before it can work).
Now, if you would calculate the pressure at the apex starting from the inlet, it should be equal to atmospheric pressure MINUS the water pressure from the difference in height between the apex and the source reservoir level. On the other hand, if you calculate the pressure at the apex starting from the outlet, it should be equal to atmospheric pressure MINUS the water pressure from the difference in height between the apex and the destination water level. If the destination water level is lower, the latter value for the pressure at the apex is lower than the former. Of course there can only be one pressure at the apex, which will be in between these two pressures. It is lower than what you would expect when calculating from the inlet, and higher than what you would expect when calculating from the outlet, so the pressure gradient will suck water in from the inlet and push it out of the outlet.
But note the two times I wrote "MINUS" in bold capital letters. You can't go below zero pressure. When the atmospheric pressure is too low to push the water from the source reservoir up to the apex, the siphon breaks up.
That's exactly what happened in the experiment described in Nature. They tested it with a 1.5 meter siphon in a pressure chamber. The water in the siphon broke up when they reduced pressure to below 0.18 atmosphere, which makes perfect sense because at that point the pressure at the apex would start to approach zero. The siphon actually turned into a double barometer with vacuum (or a bit of water vapour, actually) in between.
So yes, the motion is caused by gravity but you DO need atmospheric pressure or it simply won't work. In fact, if you look at it a certain way, it's not even wrong to say that atmospheric pressure is pushing the water up to the apex and therefore making the siphon work.
When you hold your head under water, even 50 cm (that's a pretty deep bath), you do feel some pressure on your eardrums. Certainly not enough to damage them, but you will clearly feel it and a lot of people find this unconfortable.
A train going into a tunnel at high speed (much faster than an elevator) does indeed cause a bit of a pressure increase because the air only has one way to go, though I doubt it's even as much as your 50 cm of water. And an elevator shaft normally has plenty of vents to let the excess air pressure escape out of the shaft.
Seriously, have you ever even been in a cable car in the mountains? Or flown in an airplane? Or even driven down a steep hill at high speed? In those cases, no shaft is involved but you do clearly feel the pressure on your ears. Which you get rid of by frequently swallowing or yawning, for example.
I'm a pilot, and I've made the mistake of flying with a cold even after the briefings we had had telling us not to. It was extremely painful but fortunately no damage was done. A good friend of mine was less lucky and was off for a month on medical leave with a damaged ear drum. Like I said, the cabin pressure at cruise altitude corresponds to that at 8000 ft, less than 5 times the height of that building. If that's enough to damage an ear drum, you can certainly feel one fifth of it.
Tell that to all the crying babies in airplanes or in mountain cable cars. Or to those adults unfortunate enough to burst their eardrums when flying with a serious cold. The 8000 ft of pressure difference between cabin pressure at cruising altitude and on the ground can sometimes be enough to rupture them if air cannot get into the inner ear through the blocked eustachian tube. Of course that's eight times as much as the difference between 0 and 1000 ft, but even that is very noticeable if the change happens in a short amount of time. Not dangerous, but uncomfortable to a lot of people.
Divers can indeed go down relatively quickly, but they constantly pop their ears to allow the pressure to equalize through the eustachian tube. If they can't, they won't go down more than two meters or so without experiencing serious pain. Have you ever dived to the bottom of a pool without swallowing to pop your ears? Definitely don't go diving if you have a cold.
The pressure change from the lift moving in the shaft is certainly much less (if even measurable at all) than the pressure from the altitude change. Really, the pressure on your ears is solely from the altitude change.
No, the pressure changes definitely comes from the change in altitude, the motion of the lift in the shaft has little to do with it. There may be a slightly higher pressure on one side of the cage and a slightly lower pressure on the other side, but there will be vents to reduce that effect and it won't translate in a difference in pressure inside the cage.
The difference between sea level and 1000 ft is far from negligible, though. Its about 30 hPa (300 kgf/m^2)
Airliners are usually limited to a pressure change corresponding to 500 sea level feet per minute (the pressure change rate that corresponds to climbing/descending at 500 feet per minute at sea level). 1200 feet per minute going down will definitely hurt your ears.
I wonder how they avoid the popping. The article says that they use some kind of fancy pressurization system for that, but you still have to change altitude in a short amount of time, so how do you "avoid" that pressure change? You could pressurize the whole building, but then the windows couldn't open, you couldn't have a terrace (except if it had an ear-popping airlock), and there would be a constant strong draft from top to bottom unless you kept the floors sealed airtight (which is kind of hard to do if you have things like elevators)
I imagine the best they can do, is spread out the pressure change over the slightly longer period that includes the slower parts of the journey and the wait for the doors to open, but that won't make such a huge change.
Accelerate with a "jerk" (derivative of acceleration) of 3620 m/s^3 for 0.07455 s to a top acceleration of 269.9 m/s^2, speed is 10.06 m/s at that time. Keep accelerating, but with acceleration decreasing back to zero during the next 0.07455 s. Top speed is 20.12 m/s. During the next 0.07455 s, deceleration increases from zero to 269.9 m/s^2, speed goes down to 10.06 m/s During the last 0.07455 s, deceleration decreases to zero which is reached exactly as speed reaches zero.
Total time is 0.298 s, top acceleration is 269 m/s^2 which, if you take the 1 g from gravity into account, gives 28.5 g during the acceleration and 26.5 g during the deceleration.
If you want the maximum experienced g-force to be the same during acceleration and deceleration, you either have to reduce the derivative of the acceleration (so that it's not the same as that of the deceleration) or add a short time of constant acceleration between the first two phases. This would make the calculations slightly more complicated but frankly, I don't think the passengers will really notice so maybe it's not worth the bother.
Nope, you're off by a factor of two, I'm afraid. It should have been:
1/2 a t^2 = 3/2 t being the acceleration time (half the trip time), a the acceleration while going up, 3/2 the total distance while accelerating (half the trip), and a*t = 20.12
That works out to: a = 135 m/s^2 = 13.75g.
Which would be 14.75g while accelerating up, and 12.75g while decelerating, since you get 1g from just standing still.
If you want the same experienced g-force for acceleration and deceleration, it would be: 1/2 v^2 / (a+g) + 1/2 v^2 / (a-g) = 3 which works out to a very slightly higher: a = 135,6 m/s^2
Of course this all assumes a very jerky immediate acceleration and deceleration, which might lead to complaints from passengers. What we really ought to do, is figure out how to do it with a third derivative that has a constant absolute value. The maximum acceleration will be a bit higher then.
Since the aircraft needs to be pressurized, the number of hatches to get in and out of the cabin is limited as much as possible. This avoids depressurization through leaking or damaged hatches. Some long haul aircraft have a large electronics bay with access from both inside and outside, but on most aircraft you can only get into the cabin via the doors.
Depends on the aircraft type. In the main wheel bay of an A330 you can easily fit a whole family, since the bay is the same size as that of an A340 which has an extra body gear. Some aircraft also have versions with or without an extra fuel tank in the belly, and that space is usually wide open if this extra fuel tank isn't installed.
In one company I used to fly for, someone had flown multiple legs in an A330's wheel bay before his body was finally found when someone noticed a strange smell... According to the report I read, he might have survived the first leg from Africa but remained unconscious and then died on the second leg. I don't remember after how many flights he was finally found.
When you look at communism, you can just look at the result (failed economies, empty shelves) to see how bad an idea it was.
When we look at the arguments against eugenics, they are always about how it was done, not about any results. People were sterilized or killed based on some perceived abnormality or inferiority, it was extremely crude and inhuman, I completely agree. But all those arguments disappear if we do things in a more modern way while respecting human dignity, using today's technology. Unlike communism, where it's hard to imagine a method that might actually work.
If you understand anything about evolution, it is quite clear that the human genome will tend to degenerate thanks to the comfort of modern civilisation. I'm not talking about things like intelligence (because apparently that's one area where evolution is sill alive and kicking, intelligent people being more attractive contrary to what has often been feared), but look at our senses (sight, smell, hearing), physical strength and endurance, resistance to diseases, etcetera. Our genome gets bombarded with random changes all the time, and natural selection isn't weeding out the bad changes (which are the vast majority of all mutations). We do all we can to help people overcome their defects, lead a normal life, and reproduce. Which is great, but it does mean that in the long term we will need some other mechanism to replace natural evolution. Because evolution is not just necessary to evolve a better lifeform, it's also necessary to keep it from degenerating.
Moles evolved from some kind of rat that probably had very good eyes, yet after thousands of generations moles are as good as blind because nearly blind moles have exactly the same chance of reproducing as moles with better eyes. The same is happening to us. Old-style eugenics would simply say "ok, let's sterilize all people with bad eyes, then". Today we can just say "hey, we found the cause of your bad eyesight, it's a mutation in this gene, and we can make sure your children don't inherit it". Or even replace the bad genes with a better version. What's wrong with that?
If we don't do this at some point, we will constantly need to improve all our medical techniques to fix all the defects people have been inheriting. Babies will hardly ever be born without needing immediate medical attention after birth, because we can't allow mother nature to kill the bad genes.
Wouldn't it be better to just start the next phase of evolution by taking things into our own hands? Natural selection, which is cruel and indiscriminate, has all but disappeared for us, and that's a good thing because we can do much better than that now. But we'll have to actually do that some time.
So what? Look at how many different kinds of dogs there are, and that's even without genetic manipulation. Why not have the same diversity in humans? Some with eagle eyes (from the genome of actual eagles), some with different colors (hell, we've got that already to some degree), why do all humans have to look like "God created them"?
OK, we may have to set up some rules to keep things from getting ridiculous, but I don't agree with this fear of "oh, my god, we must not mess with the Lord's creation!". There's plenty of opportunities for improvement in the human genome.
This is one of the most often repeated misunderstandings in aviation: the vast majority of crashes is caused by pilots, so we should replace them with automation since that's much more reliable. Errr... no, not by a long shot.
The vast majority of crashes is due to pilot error because the vast majority of possible crashes due to equipment failures are prevented by the pilots. I am a pilot, have never been in a crash, but have had several autopilot and other failures where, if we had not intervened, the aircraft would have crashed. But of course, all those possible crashes due to equipment failures don't make it into the statistics because no actual crash occurred. It's merely a note in the company's safety magazine for crews (along with dozens of others each month). So when an aircraft does crash (even if it's due to equipment failure), it's usually still considered the pilots' fault, and correctly so, because they should have been able to prevent it.
Take the Turkish Airlines that crashed in Amsterdam. Due to a radio altimeter failure during an automatic approach, the aircraft thought it was directly above the runway and pulled the throttles back, while in fact it was still several hundred feet above the ground. Most crews would have seen the speed decreasing (and indeed, this kind of incident had happened many times before to other crews without causing a crash) but this crew reacted much too late and "caused" the airplane to crash.
Or take the Air France that crashed after the pitot tubes froze up. The automation actually failed so the pilots had to take over. Without pilots, the airplane would have crashed anyway. And here, too, this kind of incident had already happened to other crews multiple times, but each time the crew had handled the situation correctly (even though it was not something that was trained in the simulator or accurately described in the procedures). This time the crew did not handle it correctly, in part because they were confused by conflicting warning messages from the airplane's systems telling them the plane was overspeeding and stalling at the same time. They even got aural warnings when they started to, temporarily, apply the exact correction they needed to meke. The automation was not helping them, but actually working against them and telling them they were wrong when they were, in fact, right.
If you want to have an idea of how reliable automation is, just look at the number of military drones that have crashed so far. Their mission couldn't be simpler: take off, fly over some area, come back and land. They only fly in relatively nice weather, there are vaslty less drones than passenger aircraft, yet there are many more drone crashes than passenger aircraft crashes.
It's certainly a good thing that Darpa is trying to make aircraft automation more reliable, but right now pilots are still by far the most important asset for the safety of an airplane.
In Safari on my Mac, I got a warning saying the security certificate could not be verified, and I could choose to simply continue. So then I got the text saying I shouldn't be able to see that site. Shouldn't the browser have actually said the security certificate had been revoked?
Slashdot Mirror
The siphon in the experiment stopped working when the pressure was reduced below 0.18 atm. The water was not boiling, the air pressure was just no longer enough to get the water over the 1.5 meter high apex.
Correct explanation here.
Liquid doesn't pull (at least not much), but you can get an effect much like a pull if there's enough pressure on the other side. The pressure at the apex is not negative, it's just lower than atmospheric.
Then why did the siphon in the Nature experiment stop working when pressure was reduced below 0.18 atm? (For a 1.5 meter high apex).
Correct explanation here.
Mod this up insightful, I don't know who modded it down. Indeed, a siphon can't reach 33 feet. And in the nature experiment, it couldn't even reach 1.5 meters anymore once air pressure was reduced below 0.18 atm. So air pressure is needed for a siphon to work.
Siphons stop working if the atmospheric pressure is too low. What's important is not the difference between atmospheric pressure on both sides (which is negligible), but the fact that there's enough atmospheric pressure to push the water into the siphon on any side. The experiment in Nature showed that the siphon turned into a double barometer when the atmospheric pressure was too low. So yes, air pressure does have someting to do with it.
QED.
Water doesn't pull (at least not much). Atmospheric pressure is pushing the water in from both sides, like two connected barometers. The barometer that has to push the water up over the lowest height difference (i.e. the side of the high reservoir) is the one that wins the fight, so water flows from that side to the other. If the height is too high, the barometers no longer meet and the siphon turns into a double barometer with vacuum or some water vapour in between. Boiling doesn't really have much to do with it, with mercury for example you'd just get a vacuum like the one you have in a mercury barometer.
I gave a slightly longer explanation, explained differently, here.
You are completely right. The experiment did show that the water column broke up when the air pressure was reduced enough.
The shorter column is not "dragged up", you can't drag up more than a small droplet of water. The water in the shorter column is actully pushed up by atmospheric pressure just like in a barometer. Reduce the atmospheric pressure like in the experiment referenced in the article, and the water breaks up when the pressure gets too low (0.18 atm for a 1.5 meter apex).
In fact it's not even wrong to say that air pressure makes a siphon work. If you look at it a certain way, it kind of does. It's like two connected barometers that are fighting each other, with gravity helping the higher one. Take away the atmospheric pressure, and it no longer works.
Nope. Strange how many people get this wrong, it's really not that complicated.
The water doesn't work like a chain, the cohesion of water is only just enough to hold a drop of water together, certainly not enough to pull a whole column of water along through a siphon. The motion is caused by gravity BUT atmospheric pressure is needed as well (as shown in the actual experiment that was referenced in the Slashdot summary and described in more detail in Nature). Here's how a siphon acually works:
Suppose you have a source reservoir and a destination water reservoir, with the water level of the destination lower than that of the source. The reservoirs are connected by a tube that goes from the source reservoir up to an apex above both water levels and then down into the destination reservoir. The tube is filled with water (you have to start the siphon somehow by filling it with water before it can work).
Now, if you would calculate the pressure at the apex starting from the inlet, it should be equal to atmospheric pressure MINUS the water pressure from the difference in height between the apex and the source reservoir level. On the other hand, if you calculate the pressure at the apex starting from the outlet, it should be equal to atmospheric pressure MINUS the water pressure from the difference in height between the apex and the destination water level. If the destination water level is lower, the latter value for the pressure at the apex is lower than the former. Of course there can only be one pressure at the apex, which will be in between these two pressures. It is lower than what you would expect when calculating from the inlet, and higher than what you would expect when calculating from the outlet, so the pressure gradient will suck water in from the inlet and push it out of the outlet.
But note the two times I wrote "MINUS" in bold capital letters. You can't go below zero pressure. When the atmospheric pressure is too low to push the water from the source reservoir up to the apex, the siphon breaks up.
That's exactly what happened in the experiment described in Nature. They tested it with a 1.5 meter siphon in a pressure chamber. The water in the siphon broke up when they reduced pressure to below 0.18 atmosphere, which makes perfect sense because at that point the pressure at the apex would start to approach zero. The siphon actually turned into a double barometer with vacuum (or a bit of water vapour, actually) in between.
So yes, the motion is caused by gravity but you DO need atmospheric pressure or it simply won't work. In fact, if you look at it a certain way, it's not even wrong to say that atmospheric pressure is pushing the water up to the apex and therefore making the siphon work.
When you hold your head under water, even 50 cm (that's a pretty deep bath), you do feel some pressure on your eardrums. Certainly not enough to damage them, but you will clearly feel it and a lot of people find this unconfortable.
A train going into a tunnel at high speed (much faster than an elevator) does indeed cause a bit of a pressure increase because the air only has one way to go, though I doubt it's even as much as your 50 cm of water. And an elevator shaft normally has plenty of vents to let the excess air pressure escape out of the shaft.
Seriously, have you ever even been in a cable car in the mountains? Or flown in an airplane? Or even driven down a steep hill at high speed? In those cases, no shaft is involved but you do clearly feel the pressure on your ears. Which you get rid of by frequently swallowing or yawning, for example.
I'm a pilot, and I've made the mistake of flying with a cold even after the briefings we had had telling us not to. It was extremely painful but fortunately no damage was done. A good friend of mine was less lucky and was off for a month on medical leave with a damaged ear drum. Like I said, the cabin pressure at cruise altitude corresponds to that at 8000 ft, less than 5 times the height of that building. If that's enough to damage an ear drum, you can certainly feel one fifth of it.
Tell that to all the crying babies in airplanes or in mountain cable cars. Or to those adults unfortunate enough to burst their eardrums when flying with a serious cold. The 8000 ft of pressure difference between cabin pressure at cruising altitude and on the ground can sometimes be enough to rupture them if air cannot get into the inner ear through the blocked eustachian tube. Of course that's eight times as much as the difference between 0 and 1000 ft, but even that is very noticeable if the change happens in a short amount of time. Not dangerous, but uncomfortable to a lot of people.
Divers can indeed go down relatively quickly, but they constantly pop their ears to allow the pressure to equalize through the eustachian tube. If they can't, they won't go down more than two meters or so without experiencing serious pain. Have you ever dived to the bottom of a pool without swallowing to pop your ears? Definitely don't go diving if you have a cold.
The pressure change from the lift moving in the shaft is certainly much less (if even measurable at all) than the pressure from the altitude change. Really, the pressure on your ears is solely from the altitude change.
No, the pressure changes definitely comes from the change in altitude, the motion of the lift in the shaft has little to do with it. There may be a slightly higher pressure on one side of the cage and a slightly lower pressure on the other side, but there will be vents to reduce that effect and it won't translate in a difference in pressure inside the cage.
The difference between sea level and 1000 ft is far from negligible, though. Its about 30 hPa (300 kgf/m^2)
Airliners are usually limited to a pressure change corresponding to 500 sea level feet per minute (the pressure change rate that corresponds to climbing/descending at 500 feet per minute at sea level). 1200 feet per minute going down will definitely hurt your ears.
I wonder how they avoid the popping. The article says that they use some kind of fancy pressurization system for that, but you still have to change altitude in a short amount of time, so how do you "avoid" that pressure change? You could pressurize the whole building, but then the windows couldn't open, you couldn't have a terrace (except if it had an ear-popping airlock), and there would be a constant strong draft from top to bottom unless you kept the floors sealed airtight (which is kind of hard to do if you have things like elevators)
I imagine the best they can do, is spread out the pressure change over the slightly longer period that includes the slower parts of the journey and the wait for the doors to open, but that won't make such a huge change.
Depends on who the other occupant is and how romantic you are about dying together.
OK, with a bit of mathematica:
Accelerate with a "jerk" (derivative of acceleration) of 3620 m/s^3 for 0.07455 s to a top acceleration of 269.9 m/s^2, speed is 10.06 m/s at that time.
Keep accelerating, but with acceleration decreasing back to zero during the next 0.07455 s. Top speed is 20.12 m/s.
During the next 0.07455 s, deceleration increases from zero to 269.9 m/s^2, speed goes down to 10.06 m/s
During the last 0.07455 s, deceleration decreases to zero which is reached exactly as speed reaches zero.
Total time is 0.298 s, top acceleration is 269 m/s^2 which, if you take the 1 g from gravity into account, gives 28.5 g during the acceleration and 26.5 g during the deceleration.
If you want the maximum experienced g-force to be the same during acceleration and deceleration, you either have to reduce the derivative of the acceleration (so that it's not the same as that of the deceleration) or add a short time of constant acceleration between the first two phases. This would make the calculations slightly more complicated but frankly, I don't think the passengers will really notice so maybe it's not worth the bother.
Nope, you're off by a factor of two, I'm afraid. It should have been:
1/2 a t^2 = 3/2
t being the acceleration time (half the trip time), a the acceleration while going up, 3/2 the total distance while accelerating (half the trip), and a*t = 20.12
That works out to: a = 135 m/s^2 = 13.75g.
Which would be 14.75g while accelerating up, and 12.75g while decelerating, since you get 1g from just standing still.
If you want the same experienced g-force for acceleration and deceleration, it would be:
1/2 v^2 / (a+g) + 1/2 v^2 / (a-g) = 3
which works out to a very slightly higher: a = 135,6 m/s^2
Of course this all assumes a very jerky immediate acceleration and deceleration, which might lead to complaints from passengers. What we really ought to do, is figure out how to do it with a third derivative that has a constant absolute value. The maximum acceleration will be a bit higher then.
No, no. They were talking about going from one floor to the next, which would only be about 3 m. I'm pretty sure they were joking, though.
That only exists in the movies :-)
Since the aircraft needs to be pressurized, the number of hatches to get in and out of the cabin is limited as much as possible. This avoids depressurization through leaking or damaged hatches. Some long haul aircraft have a large electronics bay with access from both inside and outside, but on most aircraft you can only get into the cabin via the doors.
Depends on the aircraft type. In the main wheel bay of an A330 you can easily fit a whole family, since the bay is the same size as that of an A340 which has an extra body gear. Some aircraft also have versions with or without an extra fuel tank in the belly, and that space is usually wide open if this extra fuel tank isn't installed.
In one company I used to fly for, someone had flown multiple legs in an A330's wheel bay before his body was finally found when someone noticed a strange smell... According to the report I read, he might have survived the first leg from Africa but remained unconscious and then died on the second leg. I don't remember after how many flights he was finally found.
When you look at communism, you can just look at the result (failed economies, empty shelves) to see how bad an idea it was.
When we look at the arguments against eugenics, they are always about how it was done, not about any results. People were sterilized or killed based on some perceived abnormality or inferiority, it was extremely crude and inhuman, I completely agree. But all those arguments disappear if we do things in a more modern way while respecting human dignity, using today's technology. Unlike communism, where it's hard to imagine a method that might actually work.
If you understand anything about evolution, it is quite clear that the human genome will tend to degenerate thanks to the comfort of modern civilisation. I'm not talking about things like intelligence (because apparently that's one area where evolution is sill alive and kicking, intelligent people being more attractive contrary to what has often been feared), but look at our senses (sight, smell, hearing), physical strength and endurance, resistance to diseases, etcetera. Our genome gets bombarded with random changes all the time, and natural selection isn't weeding out the bad changes (which are the vast majority of all mutations). We do all we can to help people overcome their defects, lead a normal life, and reproduce. Which is great, but it does mean that in the long term we will need some other mechanism to replace natural evolution. Because evolution is not just necessary to evolve a better lifeform, it's also necessary to keep it from degenerating.
Moles evolved from some kind of rat that probably had very good eyes, yet after thousands of generations moles are as good as blind because nearly blind moles have exactly the same chance of reproducing as moles with better eyes. The same is happening to us. Old-style eugenics would simply say "ok, let's sterilize all people with bad eyes, then". Today we can just say "hey, we found the cause of your bad eyesight, it's a mutation in this gene, and we can make sure your children don't inherit it". Or even replace the bad genes with a better version. What's wrong with that?
If we don't do this at some point, we will constantly need to improve all our medical techniques to fix all the defects people have been inheriting. Babies will hardly ever be born without needing immediate medical attention after birth, because we can't allow mother nature to kill the bad genes.
Wouldn't it be better to just start the next phase of evolution by taking things into our own hands? Natural selection, which is cruel and indiscriminate, has all but disappeared for us, and that's a good thing because we can do much better than that now. But we'll have to actually do that some time.
So what? Look at how many different kinds of dogs there are, and that's even without genetic manipulation. Why not have the same diversity in humans? Some with eagle eyes (from the genome of actual eagles), some with different colors (hell, we've got that already to some degree), why do all humans have to look like "God created them"?
OK, we may have to set up some rules to keep things from getting ridiculous, but I don't agree with this fear of "oh, my god, we must not mess with the Lord's creation!". There's plenty of opportunities for improvement in the human genome.
Also, how do I actually invest in SpaceX? Or just in Google Glass, which is a tiny fragment of GOOGL?
This is one of the most often repeated misunderstandings in aviation: the vast majority of crashes is caused by pilots, so we should replace them with automation since that's much more reliable. Errr... no, not by a long shot.
The vast majority of crashes is due to pilot error because the vast majority of possible crashes due to equipment failures are prevented by the pilots. I am a pilot, have never been in a crash, but have had several autopilot and other failures where, if we had not intervened, the aircraft would have crashed. But of course, all those possible crashes due to equipment failures don't make it into the statistics because no actual crash occurred. It's merely a note in the company's safety magazine for crews (along with dozens of others each month). So when an aircraft does crash (even if it's due to equipment failure), it's usually still considered the pilots' fault, and correctly so, because they should have been able to prevent it.
Take the Turkish Airlines that crashed in Amsterdam. Due to a radio altimeter failure during an automatic approach, the aircraft thought it was directly above the runway and pulled the throttles back, while in fact it was still several hundred feet above the ground. Most crews would have seen the speed decreasing (and indeed, this kind of incident had happened many times before to other crews without causing a crash) but this crew reacted much too late and "caused" the airplane to crash.
Or take the Air France that crashed after the pitot tubes froze up. The automation actually failed so the pilots had to take over. Without pilots, the airplane would have crashed anyway. And here, too, this kind of incident had already happened to other crews multiple times, but each time the crew had handled the situation correctly (even though it was not something that was trained in the simulator or accurately described in the procedures). This time the crew did not handle it correctly, in part because they were confused by conflicting warning messages from the airplane's systems telling them the plane was overspeeding and stalling at the same time. They even got aural warnings when they started to, temporarily, apply the exact correction they needed to meke. The automation was not helping them, but actually working against them and telling them they were wrong when they were, in fact, right.
If you want to have an idea of how reliable automation is, just look at the number of military drones that have crashed so far. Their mission couldn't be simpler: take off, fly over some area, come back and land. They only fly in relatively nice weather, there are vaslty less drones than passenger aircraft, yet there are many more drone crashes than passenger aircraft crashes.
It's certainly a good thing that Darpa is trying to make aircraft automation more reliable, but right now pilots are still by far the most important asset for the safety of an airplane.
Just wait until the pupils affected by the change are old enough to actually take the PISA test.
In Safari on my Mac, I got a warning saying the security certificate could not be verified, and I could choose to simply continue. So then I got the text saying I shouldn't be able to see that site. Shouldn't the browser have actually said the security certificate had been revoked?
Exactly. Maybe I'll believe it when I see an actual universe.