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Earth Science

Noctilucent Clouds Likely Caused By Shuttle Launches 132

Posted by kdawson
from the tunguska-was-a-comet dept.
icebike writes "In our recent discussion of the phenomenon of noctilucent clouds, there was some suggestions that these might be the product of global warming due to moisture being lofted high into the atmosphere. It now appears that these clouds are simply the product of Shuttle launches. In a story about the Tunguska blast, Science News says: 'Each launch of a space shuttle, which burns a combination of liquid hydrogen and liquid oxygen as fuel, pumps about 300 metric tons of water vapor into the atmosphere at altitudes between 100 and 115 kilometers. Soon after the January 16, 2003, launch of the shuttle Columbia, a liftoff that took place just after the height of summer in the Southern Hemisphere, noctilucent clouds appeared over Antarctica. Similarly, a widespread display of the night-shining clouds showed up over Alaska two days after the shuttle Endeavour blasted off on August 8, 2007. Previous studies show that in both instances those clouds included material from the shuttle plumes.' So, man-made after all?"
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Noctilucent Clouds Likely Caused By Shuttle Launches

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  • by mveloso (325617) on Wednesday July 29, 2009 @02:35AM (#28862895)

    Those damn environmentalists were right!

    • Re: (Score:2, Insightful)

      by boliboboli (1447659)
      sarcasm> Anything in the sky that isn't normal (what is normal exactly?) is caused by global warming, duh! /sarcasm
      • Re: (Score:1, Insightful)

        by LKM (227954)

        Normal: Things we have observed for a long time. Not normal: Things we have observed only recently.

        Since global warming is the main change currently happening to our climate, attributing other changes to global warming is often an acceptable first hypothesis, at least if there's a known mechanism that could potentially link the two.

        • by Capsaicin (412918)

          Since global warming is the main change currently happening to our climate, attributing other changes to global warming is often an acceptable first hypothesis, at least if there's a known mechanism that could potentially link the two.

          Well the "known mechanism" is probably a good thing to have before you move from hunch to public announcement.

        • AFAIK - The best explaination has always been rockets [slashdot.org], photos and comentry of the clouds have been posted on APOD [google.com.au] several times. The previous /. article is the first time I recall hearing it linked to AGW by an atmospheric scientist.
    • Re: (Score:3, Insightful)

      Correlation is not causation! [wikipedia.org]

      Someone had to say it. I wish CmdrTaco would write a bot which automatically inserts the "Correlation is not causation" thing into every discussion, along with an automatically selected XKCD cartoon.

    • I guess we can all relax now knowing that we are only seeing the signs of shuttle damage to the extreme edge of the atmosphere.

        I have been concerned for a while now about the possibility of disturbing what must for the most part be a very stable part of the atmosphere. Does anyone know how many pollutants ie N/SOx these launches distribute or if the chemistry of that region is likely to be affected?

    • Re: (Score:2, Insightful)

      by intheshelter (906917)

      Actually they weren't right because they said it was due to global warming. But what I don't get is that they are "scientists". They use the "scientific method". All their conclusions are "peer reviewed". They are smarter than all non-scientists. How could they be wrong? And if they were wrong about this is it possible that they could be wrong about other statements of "fact"? I thought scientists couldn't be wrong? That is was impossible for a non-scientist to question their conclusions?

      Could it b

    • Re: (Score:3, Funny)

      by NReitzel (77941)

      And now, they're putting toxic chemtrails in space!

      • Re: (Score:3, Funny)

        by Gilmoure (18428)

        At least they're not throwing around a lot of radioactive stuff in space. Would turn it in to some kind of inhospitable void.

  • by zooblethorpe (686757) on Wednesday July 29, 2009 @02:40AM (#28862929)

    The previous Slashdot thread included the tidbit that the first noctilucent clouds mentioned in recorded history were in 1887 (also noted here [wikipedia.org]). So unless someone was using hydrogen-oxygen rocketry almost a full century before the first shuttle launch, it would seem that they are not purely anthropogenic.

    Cheers,

  • Finally! (Score:3, Insightful)

    by supersat (639745) on Wednesday July 29, 2009 @02:58AM (#28863015)
    Finally, solid evidence that the government controls the weather.
  • JUST when I thought all my conspiracy-theorist friends would have something new to pursue in their spare time...
  • Why now? (Score:5, Interesting)

    by KlaymenDK (713149) on Wednesday July 29, 2009 @03:07AM (#28863067) Journal

    Disregarding the 1887 thing, which is amply discussed above, what amazes me is this:

    If these luminous clouds are caused by shuttle launches, why has it taken, 32 years and 128 launches for someone to discover this relation?
    Or, has something else happened to the atmosphere not-so-long ago which, together with the launches, have been causing these clouds only recently?

    • Re:Why now? (Score:4, Insightful)

      by Kjella (173770) on Wednesday July 29, 2009 @04:48AM (#28863555) Homepage

      An obscure topic of meteorology, that appears to occur naturally from time to time, being correlated with space shuttle launches? And probably with a significant delay between release and formation of the clouds, one would think. I think you vastly overestimate the degree of weather observation that actually gets done, and our understanding of the weather system. Yes, there's much ground-based data of temperatures, precipitation and cloud cover but very little on the actual conditions up there - the lone weather balloons they used to send up don't amount to much. It's really only in the last few decades of satellites we've been studying it in detail.

      In any case, I'm sure this will be used as another "disproof" of global warming. Like with Darwin when he gets 95% right and 5% wrong people always want to pretend that theories are either perfect or completely wrong, even though that makes no sense. Or assume some irrational assumption of uniform effects, so the results can violate them. Mess with say the Gulf stream and everything from Mexico, eastern US and Europe could get colder even during a global warming. Sometimes I wonder if they don't understand or if they just pretend not to...

      • by KlaymenDK (713149)

        I think you vastly overestimate the degree of weather observation that actually gets done, and our understanding of the weather system.

        Very likely, yes. Thanks for the insight.

        Oh and by the way, I'm not reading any global warming (dis)proof into this -- that's one thing I *know* I'm not qualified for. :D

    • by tpheiska (1145505)

      It didn't take that long.

      I distinctly remember hearing about this in a lecture back in 2006 in Kiruna space campus. They have investigated stuff like this for a while there and remarked that spacecraft launches 'also' cause them. Shuttles were not specifically mentioned.

      The clouds that are not man-made were said to dissolve ozone, but not in big quantities, they are completely "natural".

      • by Morty (32057)

        Indeed, the article implies that it is old news that noctilucent clouds can be caused by the shuttle. The new point in the article is that Tunguska was the likely cause of noctilucent clouds that occurred shortly after, which implies an impacting body containing a lot of water rather than a lot of rock. The slashdot article summary does actually convey this, although the slashdot article title is misleading.

        Note that there are parallels here with the first manned American orbital mission. John Glenn obse [dailyhistory.net]

    • Because the shuttle connection is just sensationalist journalism. This will necessarily happen for any rocket that emits water vapor at the appropriate altitude. There are launches going up all the time so the occurrences aren't as easily correlated to the shuttle.

  • Facts FUD (Score:3, Interesting)

    by Meor (711208) on Wednesday July 29, 2009 @03:08AM (#28863073)
    Only 300 metric tons? By doing a simple 1 minute Google search I've found that a single cloud weighs on the order of 100 tons-100,000 tons and more. Great bullshit kdawson.
  • So the volume of shuttle exhaust material is enough to fill a significant portion of the upper atmosphere of the North Pole?
    Why don't we see people rolling around choking at shuttle launches as the huge volume of exhaust displaces the breathable atmosphere from sea-level to stratosphere?
    • by mudimba (254750)

      I'm no rocket scientist, but I am pretty sure that they largely use liquid oxygen for the rocket boosters. Most of the exhaust is probably water vapor and oxygen.

      • Easy enough to verify. Aaaaaand, nope. Only the shuttle's main engines use liquid oxygen/hydrogen. The boosters use a solid mixture and each one provides over twice the force generated by all three main engines combined (therefore it's safe to assume the boosters are expelling a significant amount of the total exhaust).

        • Except that the boosters are done by about 46 kilometres. From there on up, the shuttle runs on its main engines.
    • So the volume of shuttle exhaust material is enough to fill a significant portion of the upper atmosphere of the North Pole?

      Really depends on how much you spread it out. If the air up there was only 1/1000 thick as it is a sea level, then, a volume of gas which might be a cubic 100 meters at sea level would be considerably larger in the upper atmosphere... miles across maybe.

      • by Reziac (43301) *

        Which gave me this odd thought: Since the planet continuously loses some atmosphere into space -- maybe it behooves us to thicken up that top layer and slow down the process... ;)

  • by wisebabo (638845) on Wednesday July 29, 2009 @03:47AM (#28863279) Journal

    So, can shuttle launches get "carbon credits"? (I know that they aren't actually reducing carbon emissions but if these clouds reduce global warming perhaps they'd be eligible). Is the amount so negligible that it wouldn't come close to offsetting the (horrendously) expensive launches?

    Do other spacecraft (Arianne, Delta, Soyuz) also create these clouds?

    • Re: (Score:3, Informative)

      by maxwell demon (590494)

      Since the water vapor brought into the atmosphere in high altitudes likely increases global warming (water vapor is a more effective greenhouse gas than CO2), I don't think they could get carbon credits.

      • Re: (Score:2, Insightful)

        by jonadab (583620)
        > (water vapor is a more effective greenhouse gas than CO2)

        That's kind of like saying gasoline is more flammable than wood.

        As infrequent as shuttle launches are, the relatively tiny amount of water vapor they've released is almost certainly not a significant contributor to global warming. There's just not enough quantity there.

        But if somehow a *lot* of water got up there, enough to form a continuous layer from the equator to the poles, you'd be looking at world-wide year-round subtropical temperatures,
  • by Zocalo (252965) on Wednesday July 29, 2009 @03:54AM (#28863313) Homepage
    I can't read the article due to Slashdot effect, but if shuttle launches are contributing to or causing (big difference there!) the formation of the noctilucent clouds then there should be a correlation to check for. Specifically, there should be a fall in the number of observed clouds during the two extended periods of time when the shuttle wasn't flying following the Challenger and Columbia disasters. IIRC, there was a similar fall off in percentage cloud cover over the US during the days after 9/11 when almost no aircraft were flying within US airspace.
    • Re: (Score:3, Insightful)

      That's an interesting point. Similarly, I wonder if the conditions that NASA chooses to launch during are related to conditions that allow noctilucent cloud formation.

    • Re: (Score:3, Informative)

      by mykdavies (1369)

      I can't read the article due to Slashdot effect, but if shuttle launches are contributing to or causing (big difference there!) the formation of the noctilucent clouds then there should be a correlation to check for.

      They did and there was - http://www.nrl.navy.mil/pressRelease.php?Y=2003&R=35-03r [navy.mil]

  • by BenevolentP (1220914) on Wednesday July 29, 2009 @03:59AM (#28863347)
    Wow, that was the easiest way to get rid of these pesky modpoints ever. Go back to the old article and retroactively mod everyone up who vaguely mentioned something spaceshuttly.
  • by Anonymous Coward on Wednesday July 29, 2009 @04:45AM (#28863537)

    From June, 2003:
    http://apod.nasa.gov/apod/ap030615.html [nasa.gov] .... note the last sentence.
    6 years.

    Sometimes it takes main stream media a while to catch on.

    Note that this APOD entry has further links to US Navy research on the topic.

  • Such nonsense. Recently noctilucent clouds have been observed with uncommon frequency all over the world, not just the US: http://www.nlcnet.co.uk/ [nlcnet.co.uk]

    These idiotic explanations (global warming, space shuttle) show that a political agenda is being protected. It is quite simple: noctilucent clouds are a symptom of cooling of the upper atmosphere. Only that allows ice crystals to survive at a height of 80 kilometers at such low latitudes.

    This true explanation cannot be allowed to penetrate the public mind becaus

    • by bcmm (768152)
      I'm pretty sure temperatures at 80km up have been cold enough for ice for several million years at least.

      Wikipedia says that the mesosphere extends from 50 to 80-85 km up, and the thermosphere from 80-85 to over 640km, and that the mesopause (the boundary between the two layers, at 80-85km) "is the coldest place on Earth, with a temperature of 100C" [wikipedia.org]. The really hot bit is well above the mesopause.

      Not to mention that cooling of parts of the atmosphere, if it was real, would still be evidence of climate cha
      • by Eukariote (881204)

        Wikipedia says that the mesosphere extends from 50 to 80-85 km up, and the thermosphere from 80-85 to over 640km, and that the mesopause (the boundary between the two layers, at 80-85km) "is the coldest place on Earth, with a temperature of 100C".

        Make that -100C, but yes, true, it is well below freezing. However, the somewhat more physically complete explanation than simply "the upper atmosphere is getting colder" is that less energy is being put into the upper atmosphere on account of unusually low UV and

    • Re: (Score:2, Informative)

      by jagsta (1607283)
      Please, how have you managed to turn this into a rant about a global warming conspiracy?

      There are 3 requirements for these clouds to form:

      1. Dust in the mesosphere to seed the accumulations
      2. Moisture in the mesosphere
      3. Temperatures less than about 150K

      There isn't a lot of either dust or water in this part of the atmosphere, and things like volcanic eruptions, and shuttle launches are one mechanism by which large quantities of both can be transported to this layer of the atmosphere, which is what TFA is sa
      • by Eukariote (881204)

        It is related to global warming/cooling as follows: the required low temperatures in the upper atmosphere are only attained if the solar UV/EUV/X-ray flux, mostly originating from the solar corona, is very low: that part of the spectrum does not penetrate well and hence is absorbed in the upper atmosphere.

        Since this UV/EUV/X-ray flux is a significant fraction of the solar output and varies strongly with coronal conditions, it is the most important driver of global warming/cooling. The solar corona is a very

        • Re: (Score:3, Interesting)

          by Abcd1234 (188840)

          Since this UV/EUV/X-ray flux is a significant fraction of the solar output and varies strongly with coronal conditions, it is the most important driver of global warming/cooling.

          And that's why you see a strong correlation between solar output and global mean temperature!

          Except, of course, there is no such correlation. After all, as you say, "the data does not lie". Whoops!

          • by Eukariote (881204)

            And that's why you see a strong correlation between solar output and global mean temperature! Except, of course, there is no such correlation.

            Don't be stupid. As any child knows, the sun heats the earth so there is obviously a correlation between solar output and earth temperature.

            However, the highly variable part of the solar output is mostly in the UV/EUV/X-ray range and as such is not easy to measure on earth. No correlations of global temperature with ground-based or narrow-band solar flux measurements

            • by Abcd1234 (188840)

              Don't be stupid. As any child knows, the sun heats the earth so there is obviously a correlation between solar output and earth temperature.

              How ironic. You accuse me of stupidity while, apparently, not understanding the term "mean global temperature".

              No correlations of global temperature with ground-based or narrow-band solar flux measurements are to be expected.

              Bullshit. We've had satellites studying the sun for decades.

              You're basically suggesting some sort of solar output measurement that's been growing

              • by Eukariote (881204)

                How ironic. You accuse me of stupidity while, apparently, not understanding the term "mean global temperature".

                Imagine the solar output doubles. What do you figure will happen to the mean global temperature? Assume it halves. What will happen? In what way is that not a correlation?

                We've had satellites studying the sun for decades.

                Indeed, and guess what: we have found strong variations in UV output http://www.ingentaconnect.com/content/klu/sola/1998/00000177/00000001/00134956?crawler=true [ingentaconnect.com]. The shorter the

                • by Abcd1234 (188840)

                  Imagine the solar output doubles. What do you figure will happen to the mean global temperature? Assume it halves. What will happen? In what way is that not a correlation?

                  Yes, my point exactly. And since solar output has a predictable variation, and that variation *does not correlate with global mean temperature*, the link between solar output and global warming is tenuous at best.

                  The variations are definitely correlated to the solar cycle which is not surprising

                  Oh FFS, so you admit, then, that the variati

                  • by Eukariote (881204)

                    Oh FFS, so you admit, then, that the variations in these other bands are linked to the solar cycle.

                    Yes they are linked, but not in the simple way you seem to suggest. The linking mechanism to the solar cycle I described is indirect. Also, UV/EUV/X-ray output variation have been observed to occur on much shorter timescales than the 11 year solar cycle. Part of that has of course to do with solar flares, but there are also medium-timescale (days/weeks) variations that correlate to changes in the solar wind pr

                    • by Abcd1234 (188840)

                      And unless you can provide evidence that said flux has shown an increasing trend over the last 50 years (okay, let's say the last 20 or so, since we've had reliable satellite data), your supposition that those bands are linked to GW is baseless.

                      In case you don't understand this argument, let me rephrase: The global mean temperature has been markedly increasing (and the rate of increase has been increasing) for at least the last 50 years. Whatever mechanism you claim is linked to GW must, therefore, show a

                    • by Eukariote (881204)

                      And unless you can provide evidence that said flux has shown an increasing trend over the last 50 years (okay, let's say the last 20 or so, since we've had reliable satellite data), your supposition that those bands are linked to GW is baseless.

                      I am sure you can agree that simple physics dictates that variations in the solar flux must drive global average temperatures. After all, the energy present in the solar radiation reaching the earth is mostly absorbed by the earth's atmosphere, surface, and sea. This

                    • by Abcd1234 (188840)

                      Wow, you just don't get it. Look up the definition of the word "correlated". Then look at the solar output over the last 50 years. Then look at the global mean temperature for the last 50 years, and the rate of change of the global mean temperature over the last 50 years. Then apply the aforementioned definition to those data sets. You might discover, much to your surprise, that there is *no correlation* between the increase in global mean temperature and the change in solar output over the last 50 yea

                    • by Eukariote (881204)

                      I guess part of the confusion lies in that we use a different meaning for "global warming". What I mean is an increase in the average global atmospheric temperature, something which can have many causes. I think you mean something more narrow: anthropogenic greenhouse-gas driven global warming.

                      Then look at the solar output over the last 50 years.

                      That cannot be done. We do not have that data. A lot of the solar output is in the EUV. It has only recently started to be measured: http://www.usc.edu/dept/space_s [usc.edu]

                    • by Abcd1234 (188840)

                      That cannot be done. We do not have that data.

                      And, again, that's a bullshit cop-out. At minimum, we have had solar output data from satellites for decades, now, which is more than enough to determine if there's a correlation between the observed increase in global mean temperature and solar output. The answer, which is hardly surprising, is that there is no such correlation.

                      Anyway, it's clear you're unwilling to listen to actual reason, so I'm done here. Hopefully anyone reading this thread will see how

                    • by Eukariote (881204)

                      At minimum, we have had solar output data from satellites for decades, now, which is more than enough to determine if there's a correlation between the observed increase in global mean temperature and solar output.

                      No we have not had that. Realize that measuring the solar flux in the EUV and X-ray spectrum is not that easy even when in space. These wavelengths are easily absorbed: lenses and mirrors cannot be used to focus those photons on a detector. You need tricky instruments like grazing-incidence spectr

            • by Abcd1234 (188840)

              For the recent trend in global temperatures, see here: http://www.canadafreepress.com/index.php/article/12865 [canadafreepress.com].

              As an aside, I'm not sure it was intentional, but you've done a very good job of citing an article which illustrates the dangers of cherrypicking data to suit your own agenda. I mean, honestly, selecting the last 5 years and using that to pick out a temperature trend. It's absolutely absurd. And it's well known that El Nino was responsible for the spike in global temperature in the mid-90s. The

  • poor quality american electronics. if the entire system was built by the Russians we wouldn't even have a single issue... the advantage of the russian system is that it isn't man-controlled, if 1 single blip comes up on their computer the entire shuttle is turned-off it can't take off (like the hacked around nasa ones). it was funny when on the discovery channel the Russian ISS engineers said: we always have to rewire all the american made ISS parts because everything is done in inches (the only country in
  • More wishful thinking that man's slightest activity can cause changes on a global scale. The numbers don't add up. Sure, that's a lot of tons of water vapor sent up a couple of times a year, but compared to the volume of the hemisphere's atmosphere, it's virtually nothing. Add to that the osmotic pressures that cause dilution, supersonic currents that dissipate the vapor, and the movement of the ship itself which leaves just a slender tendril through the air. Now we are expected to believe that this wat
  • "In our recent discussion of the phenomenon of noctilucent clouds..." ... we had plenty of input on the history and nature of them, including an uncharacteristically (for recent examples) detailed and accurate recounting from Wired.

    So how is it one can reference an article with such good, clear information, and then utterly ignore all of that in order to posit such a ridiculous assertion? Worse than submission of such junk articles is the complete lack of editorial effort in determining whether the submissi

  • ... which is the layer of the atmosphere, 50km-85km, immediately above the statosphere. This is a very lonely place, the air's too thin to float baloons, airplanes and such, and too thick for orbiting spacecraft. Its major inhabitants are falling meteors and rocket ships enroute to outer spaces. Also hosts the D Layer of the ionosphere (during daylight hours) which tends to absorb radio waves transmitted from the ground.
    Convection stops in the stratosphere (because there is no temperature inversion there
  • Cognitive filtering (Score:3, Informative)

    by argStyopa (232550) on Wednesday July 29, 2009 @08:08AM (#28864485) Journal

    Here's what I find interesting: the bulk of the 'data' behind anthropogenic global warming points to a rise in temps THIS century of a small handful of degrees. The concern is over the consequences of a further rise of, again, a small handful of degrees.

    Now, drag out all the charts, graphs, and politically-motivated reports you want, for and against; the only actual modern large-scale experiment that gives us any proof regarding human impact on temperature was the week after 9/11.

    The complete lack of aircraft over the US had a SIGNIFICANT effect on high and low temperatures immediately.

    Couple that with this current evidence that a single shuttle launch can apparently impact cloud formation over the Antarctic, and I'd say that's a far-more-tangible red flag than the supposed connections made over CO2 or other 'global warming' gases.

    So why isn't there a significant, sustained effort to minimize air travel?

    • Re: (Score:2, Insightful)

      by OrangeDoor (936298)
      I am unsure about your reasoning regarding the effect of airplanes, seems like there are many dots missing. Firstly, link about the temperature drop from no aircraft? That is curious and I wonder if it has a much greater effect because of the altitude at which the gases are released (though the long-term result may be the same despite the immediate evidence, that is all the ground level gas released is just as damaging as that from the airplanes).

      Secondly, What is the effect of noctilucent clouds on on o
    • Re: (Score:3, Insightful)

      by hawkfish (8978)

      Now, drag out all the charts, graphs, and politically-motivated reports you want, for and against; the only actual modern large-scale experiment that gives us any proof regarding human impact on temperature was the week after 9/11.

      It was three days. Citation with reference here [realclimate.org].

      The complete lack of aircraft over the US had a SIGNIFICANT effect on high and low temperatures immediately.

      Three days is far too short a time period to say anything conclusive about climate. You might as well argue that the sustained low temperatures last winter are a sign that the world is cooling...

      Couple that with this current evidence that a single shuttle launch can apparently impact cloud formation over the Antarctic, and I'd say that's a far-more-tangible red flag than the supposed connections made over CO2 or other 'global warming' gases.

      So why isn't there a significant, sustained effort to minimize air travel?

      You mean like this [yahoo.com]? Judging from this and the rest of your comments, you really need to get out more...

    • Re: (Score:3, Insightful)

      by radtea (464814)

      So why isn't there a significant, sustained effort to minimize air travel?

      Because we like air travel and hate industry. Minimizing air travel would inconvenience too many of "the right kind of people."

      The same kind of thinking can be seen in the summary: "It now appears that these clouds are simply the product of Shuttle launches." The key word here is "simply", implying that there's nothing to worry about, because shuttle launches are a Good Thing.

      AGW may be real--the signal in ocean heat content is pr

    • Re: (Score:3, Insightful)

      by Reziac (43301) *

      Considering how variable the weather is in September, how can you be sure you're seeing causation, and not mere correlation? Having 3 or 4 days of temps significantly warmer or cooler than the week before is normal that time of year, as it's when winter fronts start moving across the continent.

      While I've seen the sky completely haze over between morning and afternoon due to contrail spreading (if you work outside all day and can watch the sky, you can see this happen) I'm still not convinced it's significan

    • So why isn't there a significant, sustained effort to minimize air travel?

      $$$

      not too hard to figure out. and really what is the alternative to air travel for moving vast amounts of people vast distances.
      I don't know, but you seem to have all the answers.

  • I remember growing up in New York when the Space Shuttle launched it always rained the next day.

    • by Tacvek (948259)

      Sure, but it rains often enough up there that I would not be willing to blame the shuttle. More likely the times that conditions are best in Florida for a shuttle launch tend to come the day before it rains in New York.

      But I'm sure you posted your anecdote more to be humorous than to seriously suggest a causal link.

  • In the science field, there's a saying "anecdotes are not data."

    Let's see some real statistics.

  • by peter303 (12292) on Wednesday July 29, 2009 @10:54AM (#28866485)
    Interesting PBS NOVA show on Global Dimming [pbs.org] or the effects of a hundred thousand US jet flights a day. they mostly halted the three days after 9-11. The upper atmosphere become noticeably more clear in that short period.
  • It's completely natural. Space launches are a natural product of evolution.

    Or, to put it another way: if God didn't want us to go into space, he wouldn't have made it so easy to react hydrogen with oxygen.

Simplicity does not precede complexity, but follows it.

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