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Most people know that at high altitudes the air is both thinner and, typically, colder, than at low altitudes.
To combat global warming, then, one thing we could do is simply make the air thinner than it is now. We could do this by liquefying and storing some of it --not to the extent where it is
dangerous (see the "Atmospheric Warfare" link). I'm suggesting a mere 10% reduction in sea-level air pressure here.
See the "pressure calculator" link. Normal pressure at sea level (zero meters or feet of altitude) is associated with "760mm of mercury". If we reduce this pressure by 10% then that is 760-76=684mm of mercury, or the equivalent of having increased one's altitude by about 2900 feet or 880 meters. If you have ever visited such an altitude, and compared it to sea level, you would know that indeed the world's air is generally cooler higher-up than lower-down. Logically, therefore, if worldwide air pressure was reduced, this would be a valid way to combat global warming. (Not necessarily practical, but certainly valid.)
A better variation on the theme is to store ("sequester") only nitrogen, not "whole" air. This way the total oxygen in the atmosphere remains constant (the "partial pressure" of oxygen stays the same; its percentage as a constituent of air would increase from the current 20% or so, to a little more than 22% . Nobody would have any greater difficulty breathing than before, even at multi-thousands of meters of high altitude, because the same amount of oxygen would exist up there as exists now.
Another advantage is that the production of liquid nitrogen is already being done on an industrial scale (I once read the price of liquid nitrogen was about the same price as milk; don't know if still true). It is easy to extract simply because air is mostly (about 79%) nitrogen; it is LOTS easier to extract than carbon dioxide!!! So, we have the basic technology in place, and would merely need to ramp it up to a rather larger extent, if we wanted to pursue this Idea. And, of course, we would need a nice big place to put all that LN2. (The "Atmospheric Warfare" idea talks about open pit mines; they are still there, waiting to be used for something....)
Atmospheric Warfare
Atmospheric_20Warfare
An old Idea, referenced in the main text. [Vernon, Dec 23 2009]
Pressure Calculator
http://www.csgnetwo...ressurealtcalc.html
This lets you find the altitude typically associated with a specified air pressure. [Vernon, Dec 23 2009]
Fiery Coal Mines
Extinguishing_20Coal_20Mine_20Fires
Open pit mines are not the only places that could hold LN2; some places might even benefit from the experience (well, after the fires are put out, of course!). [Vernon, Dec 23 2009]
mirrors vs global warming
http://www.thaindia...ng-2_100160505.html
As mentioned in an annotation [Vernon, Dec 24 2009]
On moving worlds....
http://www.stainles...oppings.com/?p=1073
If you want to know how it might be possible to move the Earth to a wider orbit (where reduced sunlight equals lesser warming), read this book. [Vernon, Dec 24 2009]
Some Mars atmosphere data
http://www.daviddar...ia/M/Marsatmos.html
numbers used in an annotation [Vernon, Dec 24 2009]
Some Earth CO2 data
http://www.newton.d...ci/env99/env188.htm
numbers used in an annotation [Vernon, Dec 24 2009]
[link]
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//the price of liquid nitrogen was about the same price as milk//
Bovine? Ovine? Rangiferine? Lupine? |
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First, is the basic assumption correct? In other words, if
we make the atmosphere thinner, will it reduce global
temperatures? I am not sure. |
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If I understand correctly (which happens sometimes), heat
is trapped by the various components of the earth's
atmosphere. I am pretty sure that it makes no difference
whether these components are mixed (as in our
atmosphere), or considered as several "shells" of different
gases. You're reducing the amount of nitrogen, but the
main greenhouse gases are CO2 and methane. |
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So, will reducing the total amount of nitrogen in our
atmosphere have any effect on global temperatures?
Where did you get your figure of "10%" from? How great
will the effect be? You say that thinner air "holds" less
heat, but this is a canard - it's a question of how well it
insulates, not how much thermal energy it holds. |
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Second, if you are going to liquify and thereby sequester a
gas from the atmosphere, why not CO2? It is easier to
liquify (or solidify) and, mass for mass, has a far greater
greenhouse effect than N2. So, why nitrogen? |
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Third, you will of course have calculated the tonnage of
nitrogen involved in your plan, and the volume (in cubic
km) it will occupy? |
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[MaxwellBuchanan], I pulled the 10% out of thin air; this Idea is more of a suggestion than a detailed plan. And, of course, this is the HalfBakery, where half-baked ideas are welcomed. But it remains true that even with the current content of CO2, methane, and other greenhouse gases, the air is cooler at higher altitudes than at lower altitudes. Therefore I'm confident the basic Idea is sound (again, in terms of validity, not practicality), even if I deliberately didn't figure out a lot of details. |
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Unfortunately, it's not sound unless you deliberately do
figure out the details. |
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Let me give you an alternative argument. A large
proportion of the solar radiation hitting the earth is
reflected back into space. Much of this reflection is done
by nitrogen, and much more of it is done by water droplets
and ice crystals which require a certain atmospheric
density in order to form. If you reduce the nitrogen in the
air (and hence total atmospheric pressure), less insolation
will be blocked. However, exsolation in infrared
wavelengths is blocked mainly by CO2 and methane, which
will remain unaltered. |
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Therefore, sequestering nitrogen (and thereby making the
atmosphere relatively richer in CO2 and methane) will
cause an increase in greenhouse effects, and a rise in
surface temperatures. |
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Now....I have no idea if any of what I have just said is
correct. It may well be complete bollocks because "I
deliberately didn't figure out a lot of details". Likewise,
what you propose may well be complete bollocks for the
same reason. |
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The trick of doing science is to worry about the numbers.
Those positive and negative signs matter. |
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And again, why not sequester CO2, which is easier and
much, much more likely to be effective? |
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//in terms of validity, not practicality// [marked-for-tagline] |
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And as for some numbers... the earth's atmosphere has mass
of about 5x10^18kg (according to Mr. Wiki's Pedia), of which
nitrogen is, what, 80%? So, 10% of atmospheric nitrogen
would be 4 x 10^17kg. |
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The density of liquid nitrogen is something like .8 , so we're
looking at 3 x 10^20 cubic centimetres, or 300,000 cubic
kilometres of liquid nitrogen. |
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Please ignore this if it is
considered trolling, but I have a side
question. My parents though smart
people listen and actually believe Rush
Limbaugh and at Thanksgiving told my
wife while I was outside, that global
warming in so much as it is caused by
humans is a farce. Now afterwards when
I heard I was agast but did a little more
research and now I'm not sure. Again I'm
not trying to troll, but one question,
how do global warming proponents
explain the dairy farms in Greenland? I
looked on the web but couldn't find an
answer. |
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[MaxwellBuchanan], which has more total heat, a red-hot nail or a bathtub full of cold water? The answer is, "the water", because total heat depends upon both temperature and mass. It so happens that at very high altitude (say 30km) the gas molecules are each individually moving very fast and have a lot of kinetic energy (high temperature, well over 100C), but the total mass of air at that altitude is so low that if you stick your hand out into it, it will freeze far faster than it will roast. |
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To a lesser extent the above is the primary reason why even a 10% reduction in the mass of air will have a general consequence of being cooler. Venus is hot not just because is closer to the Sun and its atmosphere is mostly CO2, it is also hot because its atmospheric pressure at its surface is 90 times that of Earth. |
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[MisterQED], the best answer to the question is, "It doesn't matter to what extent human activities have contributed to global warming, IF we don't want the phenomenon to have devastating consequences." We still need to do something about it! That likely means a mulitude of approaches. One could be to replace asphalt roads everywhere with concrete (higher albedo). One could be to reduce or sequester CO2 production, since it is KNOWN to be a greenhouse gas, and therefore MUST be a contributing factor (regardless of exact degree). One could be to put mirrors into space (see link). In the long term, the Sun, which while becoming about 5 billion years old has also become 30% brighter than when it was born, is due to become brighter yet, so we might want to eventually consider moving the entire Earth-Moon system to a wider orbit. And so on... Thinning the atmosphere is just another option, that so far as I know has not previously been proposed. |
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To further Vernon's comment, there are natural cycles,
which mean that there are small scale climate shifts. The
dairy farms in greenland would have occurred during the
mediaeval warm period, a slight increase in temperature. |
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The problem is that the current warming trend is out of
sequence with all known cycles, and trends upwards once
they are taken into account. It is probably close to the
peak of the mediaeval warm period right now, and shows
no signs of slowing down. |
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Vernon, whilst much of what you say is true, the fact
remains that the total insolation trapped by the earth's
atmosphere is due to a combination of the heat retention
by all the gasses in the atmosphere, of which nitrogen is
one of the least potent. A 10% reduction in the total
amount of nitrogen around the planet will have a
negligible effect. |
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Again, if you're going to sequester an atmospheric gas, why
choose nitrogen (a naturally-abundant gas which is hard to
sequester and has a very small insulative effect) rather
than CO2 (a partially man-made gas which is easier to
sequester and has a huge insulative effect)? |
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What are the merits in sequestering N2 instead of CO2? |
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[MaxwellBuchanan], you seem to have missed the point that a larger mass cools more slowly than a smaller mass. So, if we thin the atmosphere by 10%, it obviously is 10% less massive and thus can cool more quickly than at present. Also, note that a thicker atmosphere can hold more water vapor, which also is a greenhouse gas. You will still have both these issues even if you extract all the CO2 from the air. |
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A smaller mass also warms up more faster than a larger one.
Also, the capital of Peru is Lima. What of it? |
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Anyway, I'm just curious to know why you want to sequester
nitrogen rather than CO2. |
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But no matter - it's Christmas, and therefore not the time to
bandy about "mfd bad science"s. |
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[MaxwellBuchanan], I have explained the rationale for this Idea, to extract nitrogen. See the last part of my last annotation, for example. You want another? Note that CO2-sequestration is an old idea, while this one is new and HalfBakery-worthy. OK? |
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But you also want some numbers, so here: The atmosphere of Mars is 97%CO2 at an average of 7 millibars of pressure (that translates to about 5.1 millimeters of mercury). The partial pressure of CO2 in the Earth's atmosphere is about 0.0004 of its total 760 millimeters of mercury, or about 0.3mm. So, if CO2 was the main reason for holding heat in an atmosphere, then with 17 times as much CO2 gas pressure on Mars than on Earth, Mars' air should be holding heat better than the Earth's. It doesn't. Because the air on Mars is lots lots thinner than the air on Earth! |
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The production of CO2 (as dry ice and pressurized liquid) is
also done on an industrial scale, and is easier than that of
LN2. |
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Also, given the choice between removing 10% of the
earth's atmospheric nitrogen with almost no effect, and
50% of the earth's atmospheric CO2 to more than offset
anthropogenic effects, the latter involves approximately
400 times less gas. |
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Yes, removing earth's atmosphere will make it cooler. And
yes, it is a novel idea. It's just not a very good one. But
hey. |
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1) Making the atmosphere thinner (by removing some
Nitrogen) might trend toward cooling, but the amount
needed to do so would probably be so enormous as to
offset any benefits.
2) There is already a limited effect of this: farmers do it all
the time when they plow the fields ... aeration of the land
does plow some Nitrogen into the soil. Its good for the
crops.
3) Considering the cost v. benefit ... the work energy
required would never really offset the thermal load
contributed to the atmosphere = work, even at high
efficiencies, generates heat. The massive amount of work
energy needed to take an appreciable amount on Nitrogen
out of the air would certainly be greater than any cooling
realized. |
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[MaxwellBuchannan] absolutely slays me! He nailed it on almost every assertion. Kudos to [MechE] also, I didn't know that he was smart. |
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BTW, how much net heat is the Earth retaining by extracting, and refrigerating, N²? Does it offset the INCREASED penetration of radiation of the sun because of less "stuff" in the way? The same amount of Solar radiation hits the Earth no matter what: about 1.39 kW/M² constantly. Remember the Second Law Of Thermodynamics. |
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Prove it, [Vernon]! Tell us why! This is the œbakery, not the Œbakery. And you're usually the resident Meta-Physician, so I hear... |
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CO² is unbelievably easier to extract than nitrogen - (Speed and energy wise.) - incidentally. If you can come up with an solution, than the airlines will probably $ you big for your patent, so that their fuel tanks can ostracize O² in a more timely manner. |
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It might be easier to extract the nitrogen by fixing it rather than pressurizing it. That high pressure gas is just an accident waiting to happen, whereas urea or other organic nitrogen could be stored in large guanolike heaps in the Mojave or perhaps cast into blocks and used to build a castle for the Atmospheric Overlord. |
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I wonder if increasing the relative percentage of atomospheric O2 will produce more fires? Certainly cigars will need to be longer. |
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//easier to extract the nitrogen by fixing it// |
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Chemical fixation of nitrogen is certainly easy, and is already
done on an industrial scale to produce fertilizers. |
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This process consumes roughly 7% of the world's fossil fuel
energy. |
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//[MisterQED], the best answer to the question is, "It doesn't matter to what extent human activities have contributed to global warming, IF we don't want the phenomenon to have devastating consequences." We still need to do something about it!// |
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//To further Vernon's comment, there are natural cycles, which mean that there are small scale climate shifts. The dairy farms in greenland would have occurred during the medieval warm period, a slight increase in temperature. |
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The problem is that the current warming trend is out of sequence with all known cycles, and trends upwards once they are taken into account. It is probably close to the peak of the mediaeval warm period right now, and shows no signs of slowing down.// |
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My apologies, but neither of these is seems an accurate answer based on what I can find. It does matter to what extent human activities have contributed to global warming because if the answer is zero or nil, then we may be in a naturally occurring cycle of heating and cooling. If that is true then there are no “devastating consequences” to avoid. Greenland seems way too cold to support farming and from the chart on Wikipedia, we are not near the average peak temperature of 750AD, so why should we see present conditions as more than normal cyclical changes? Was 800AD around the time of any major eruptions? Though I don’t think even major eruptions have 10+ year effects. Maybe what we should be worried about is a cyclical pattern of eruption events that always cool the Earth off. |
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Again I’m not trolling, I assumed that these questions had already been asked and answered. I’m just looking for those answers. {MechE], can you give me a link to published temperature cycles that show we are out of normal range? |
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Greenland is called that because of ancient Viking marketing. Still, the place really did have a fair amount of greenery when it was colonized at the height of that era. And, yes, one reason the Viking era ended was because the world entered a cooling trend that culminated as the Little Ice Age of the early-to-middle 1600s. |
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There are some people who think that at that time humans ramped up the burning of fossil fuels to keep warm, and one consequence, especially when worldwide human population increase is included (since it began to explode as this was also near the beginning of the Industrial Age), is that we kept the LIA from becoming the next Major Ice Age. |
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Logically, though, it would behoove us to know certain details from the height of the Viking era, such as what the average sea level was, so that we could compare it to current events. To the extent that we think this will be surpassed, and start drowning coastal lands occupied by tens of millions of people, that is an extent to which we might decide that human intervention, even against purely natural global warming, might be warranted. |
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//it would behoove us to know certain details from the
height of the Viking era// I sincerely hope not. I for
one do not fancy being behooved. The helmets with horns
on were quite camp enough. |
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A lot of people have pointed out that, even if we are
unsure as to whether global warming is happening; and
even if we are unsure as to whether it is anthropogenic or
natural, it would be prudent to counteract it by reducing
CO2 emissions. |
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This is true only if there are unlimited resources of money
and motivation. But there are not. Therefore, unless we
are really quite sure about global warming, we risk
diverting money, effort and attention from what may well
be much greater threats to humanity and to the planet. |
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//Methinks you're not grasping economics.// That is quite
likely, and I do have a very simplistic view of this sort of
thing. But I can't help feeling that if we put as much effort
into population control as we are saying we should put into
CO2 reduction, we'd solve a lot more problems for a lot
longer term. |
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Well, the human population is probably six-fold above its
optimum. And you don't need any punitive taxes or child-
limits. If you made contraception free and widely
available, addressed child mortality in developing
countries, and gave every 40-year-old woman the
equivalent of 20 times the average annual income in her
country if she had only one child, I think you'd bring the
population back down to a reasonable level in a few
generations. And the cost would be a fraction of that
proposed as the planetary spend on CO2 controls. And
you'd solve global warming, environmental encroachment,
resource depletion and many other problems at the same
time. |
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Based on the current level of unsustainable technology we could use a few extra bodies, but take that away and the place is quite overstuffed. |
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//Well, the human population is probably six-fold above its optimum// I second [bigsleep]s question. My knee jerk reaction is to say the world has too many people, but deeper thoughts hope some of those people are working on my flying car, and other world issues that I haven't gotten to yet, so the issue is more complicated than just keeping people off my lawn. I also agree that getting people to use energy more efficiently is a good idea, but unless someone comes up with some better data, I'm still dubious that CO2 is causing global warming to any significant extent and this is an important issue as people are planning large projects to counter the greenhouse effect which can have other effects (iron seeding oceans to cause blooms, etc.). |
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I would think sea level would be an easily measurable quantity over the centuries. Especially in those remote lowland islands and places like Venice where the change is SOO noticable. Does anyone know if we have we reached a new high tide line? Shouldn't there be some kind of geological evidence of tides? Or is that obscured by plate tectonics? |
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having just seen a History Channel special on the Sahara... yeah, plate tectonics would tend to munge things up a bit. |
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//Do you have a source for that ? // |
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No. It's just that I happened to bump into five people I don't
like. |
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Well, I just figured a billion people was a nice round
number. It's what the population was in around 1800, only
two centuries ago, and clearly that level was sufficient to
be workable. |
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It's interesting to ask how many people there should be.
Below some threshold density, there aren't enough people
to maintain infrastructures, maintain industrial and
cultural diversity, and create a rich society. Above that
density, in effect we are just living to live: extra people
just produce whatever extra it takes to maintain them, on
a global view. |
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My guess is that, with the current levels of automation and
mechanisation, a billion people is more than sufficient.
Above that number, it's just a question of sharing finite
resources (land, water, whatever) amongst a greater
number of people. |
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Travel destinations are just another resource. The more people, the less space in the world per person. A desire for a certain amount of open space is part of our overall makeup (otherwise no city would have public parks), and that is one reason why people go off to less-crowded places to relax. Logically, it would be simpler if there was less crowding to begin with. |
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// Logically, it would be simpler if there was less crowding to begin with.//
That is one of the reason I want there to be advancement, because sooner or later we will open up space to habitation and then we can all have LOTS of space. |
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not really looking forward to the future equivalent of GPS Nav systems ("turn right, here"). |
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