# Vacuming out the dust from prehistoric Earth's atmosphere

I have dinosaurs, I have an asteroid I want to save the dinosaurs from the asteroid, but I'm not allowed to use the giant laser again, after that incident in Alderaan. So I have only one chance left...

## The Giant Housemaid mech.

I want to make things sure, so I need a vacuum cleaner that is big and strong enough to suck out half of the current Earth's atmosphere under a week. I also want to make sure that the dinosaurs don't get killed so, it's important to know, What effects would this vacuum cleaner have in the planet's weather? (this implies, that the air gets filtered then immediately returned to the atmosphere.

There were other factors to the extinction, but let's focus on the more pressing matters at hand.

• I suggest editing your question, the dust was only part of the problem. See Effects of impact here – Joe Kissling Apr 6 '17 at 14:36
• @JoeKissling How was it about the unspoken rule, that I should ask one question at a time? Wait... – Mephistopheles Apr 6 '17 at 14:41
• Just trying to help you avoid getting answers just telling you that only filtering the air (probably) won't save the dinosaurs. – Joe Kissling Apr 6 '17 at 14:45
• It's likely the asteroid wasn't the only cause. Large dinosaurs were declining before the asteroid ever hit us. – Mormacil Apr 6 '17 at 14:46
• Hmm... you can't blow up the asteroid, but maybe you should tug it gently into Jupiter before you kill those giant lizards you were supposed to save? I'm not sure what vacuuming up Earth should achieve, either. – John Dvorak Apr 6 '17 at 15:01

As many have pointed out so far, Mega Maid has some physical limitations. It's almost like it's just a plot point in a movie or something! But that doesn't mean there's not options.

What you are looking to do is similar to what we have to do in real life in clean rooms. In fact, it's something similar to what we do with normal air conditioners as well:

A critical factor in cleanroom design is controlling air-change per hour (ACH), also known as the air-change rate, or ACR. This refers to the number of times each hour that filtered outside air replaces the existing volume in a building or chamber. In a normal home, an air-conditioner changes room air 0.5 to 2 times per hour. In a cleanroom, depending on classification and usage, air change occurs anywhere from 10 to more than 600 times an hour.

10 to 600 air changes in an hour is a lot! That's way more than your half-an-atmosphere-in-a-week criteria, though admittedly for a much much much smaller volume of air. But they also have an interesting criteria called "laminar flow." Basically, the air circulators in a clean room aren't allowed to create any turbulence. If they created turbulence, the eddies could suspend particles for an unknown amount of time, but if the flow is smooth, the lifespan of a particle in the air is well defined, and quite short.

You're not going to need laminar flow to do your job, but your calls to not change the weather are very reminiscent of that requirement. Weather typically goes hand in hand with chaotic turbulent flow, so if you minimize the amount of turbulence you create, you're going to minimize your weather issues. You can take lessons from the clean rooms and apply them to save your dinosaurs!

One of the big keys to how clean rooms do their job is distributed air handling. They don't have just one air intake on one side of the room. The area is peppered with holes for the air handlers to pull air out of the room. The ceilings also are designed to maximally distribute the air across many openings so that there is an even flow of air from ceiling to floor, pulling all the dust out they can.

You should do the same. Now I don't know what your budget is, but given that you've gone back in time, I'm assuming you can predict the result of enough football games to cover some pretty outrageous bills. This should be enough to build enough hardware to distribute your megamaid across the entire earth.

Now don't get me wrong, you're going to do some environmental damage. Let's say we want out air handler to take up 1% of the total surface area of the earth. That's going to involve cutting down a lot of forests, but it's distributed so you should be able to do so without causing the extinction of too many species. Install the the "return vents" near the ground this way, and we'll put the outlets way up high. The stratosphere should do the trick.

Now our air intake area is pretty massive. It's now 5,100,000 square kilometers! As Chris M. pointed out, the atmosphere is 4,200,000,000 cubic kilometers, so to process that in 7 days you need to process about 7000km^3/s. Now seven thousand cubic kilometers of air is a lot of air to move in a second, but we get to move it with a substantial distributed air intake, so the air flow rate only has to be 1.3 m/s!

Now that's a noticeable 3mph breeze, straight down, so it will definitely have some effect on the weather, but a manageable one. If you can expand your budget by predicting a few more UFC tournaments, and can take up 10% of the planet's surface area, you can bring it down to 0.3mph, which would be unnoticeable.

• How much of an impact on the weather would the device itself have, at this colossal size? – Frostfyre Apr 6 '17 at 17:45
• That's a good question. I think it depends on a lot of details. You're going to want to match the albedo of the intakes with the albedo of the ground you're covering so you don't create a hot spot or a cold spot. The question I'm not sure about is how much of an effect would be caused by the pipes you'd need to move the air up into the stratosphere. That might depend on your structural capabilities and energy supply -- how small can you make the pipes and how fast can you accelerate the air up through them. – Cort Ammon Apr 6 '17 at 18:02
• One issue is that even if your intake is 5100000 square kilometers, the atmosphere only reaches up some 10 kilometers, and it won't flow as nicely as you would expect. You would mostly just deprive one specific area of Earth of air (if you managed to remove it from the surface, that is; you'd probably need a giant compressor right at the intake - and additional ones each extra few kilometers - because just vacuum wouldn't cut it) – John Dvorak Apr 6 '17 at 19:28
• @JanDvorak That's why you need to make it distributed. If your clean rooms had one mega-vac in the corner, they would have the exact same issue you describe. Instead, the floor is perforated (or at least can be perforated) and the air flows through all floor tiles evenly. – Cort Ammon Apr 6 '17 at 19:42
• There's all kinds of non-linear math that this answer is not taking into account. If there was one giant device that took up 5100000 km^2, even if a given section is only sucking in 1.3 m/s, the cross section of the atmosphere around the device isn't that large, so the air velocity is going to have to be much larger to compensate. And then double when you take into account that there needs to be an air out-flow for the air you've filtered. – Shufflepants Apr 7 '17 at 15:21

I'm not sure if it just my vacuum cleaner on my rugs, or if it is an aspect of all vacuum cleaning everywhere, but the static electricity in the air seems to rise whenever I clean the rugs.

Scale that up to planetary size and your maid mech might just be trading a nuclear winter for the mother of all lightning storms. Do you prefer your extinct dinosaurs frozen or fried?

• Neither. I prefer using the Eiffel tower as our makeshift lightning rod, for giggles and laugh. – Mephistopheles Apr 6 '17 at 15:00
• @RedactedRedacted I'm sorry in that case. The tip of a lightning can't see any further than sixty meters. If Henry is right about the electric discharge, your dinosaurs will be electrocuted. – John Dvorak Apr 6 '17 at 15:03
• Fried, please. With a side of mashed potatoes and steamed vegetables. Do you do peppercorn sauce? – AndreiROM Apr 6 '17 at 15:06
• @AndreiROM C'mon, if I had a giant mecha maiden floating in space, making giant batteries from graphene is really nothing. – Mephistopheles Apr 6 '17 at 15:09
• @RedactedRedacted If you had a time machine to take the Eiffel tower back to the time of the dinosaurs, why wouldn't you just use it on the asteroid? – Spencer Apr 6 '17 at 20:46

One extinction for another

The atmosphere has a mass of $5.5\times10^{18} kg$ processing half of it ($~2.75\times10^{18}kg$) in a week means processing $4.5\times10^{12}kg$ of atmosphere a second. That's four and a half trillion kilograms per second.

Now the fastest you can get air to move using a vacuum is the speed of sound, so about $340 m/s$. The majority of the mass of the atmosphere is in the troposphere and one cubic meter of air has a mass of about one kilogram. Therefore we can assume a volumetric flow rate of $4.5\times10^{12}m^3/s$ of the atmosphere. With those parameters, the opening of your vacuum would have to have an area of $1.3\times10^{10} m^2$. We are limiting our work to the troposphere so the height is ~10000 meters making the aperture 1.3 million meters long or 1300 kilometers.

Moving air this fast creates pressure drops that will be in their own right fatal over a large area. This pressure drop will also create enormous super storms and lightning and likely kick up megatons of dust. And that's just the info flowing of the air.

The outflow is worse, again dust storms, lightning, supersonic winds. But now with all that hot air you will produce the mother of all storms: Supercells and Hypercanes if too close to water. Driven by super heating these storms will push water vapor into the upper atmosphere and destroy the ozone layer.

You just kill them faster

Earth's atmosphere is something like 4.2B cubic kilometers. Source To remove half of it in a week, you'd need a vacuum cleaner that can move:

2.1 x 10^9 km^3 / 7 days

conversion math

Approximately 7.4 x 10^24 cfm.

Ignoring the fact that this would take yottawatts of power to do, you're going to at minimum create absolutely ridiculous windstorms drawing that much air that quickly through a filter. Weather patterns will be interrupted, massive tidal waves will form, and you'll probably end up sucking all the flying dinos into the filter.

Also, you're going to heat the air quite a bit during filtration, so you might accelerate the natural warming and cooling of the Earth and cause an ice age when you're done. And probably cause extreme weather beyond anything the planet has seen up to this point as the weather patterns try to resume.

Maybe...maybe don't do that. Or do it anyway, but realize you're probably just killing all the dinosaurs faster.

Let it rain. No really. Rain clears up the sky nicely. But it will need to be long. I don't think it needs to be heavy. So it doesn't have to be a storm. Your beloved dino's will be wet for some time, and some will die. But those pesky mammals and humans will not get their change this time. Shower Bot it is.

It will lead to other problems, like that rain is toxic now. River systems will change with the amount of new material. And I don't want to know what happens to reefs.

And you might end up with a flooding event. Bugger...

• So then I have to start building a giant pool cleaner. – Mephistopheles Apr 6 '17 at 15:22
• Well, you wanted to clean the air... And I reckon that in most peoples eyes Dino's were on land, so there it that. – Flummox Apr 6 '17 at 15:24
• In before a giant mecha maid is what ultimately caused the giant flood described in Genesis 6-8. – John Dvorak Apr 6 '17 at 16:47

The volume of the atmosphere at sea level 4,200,000,000 cubic kilometers.

Cleaning half of it in 1 week means you have to clean 300,000,000 cubic kilometers a day, in other words 3472 cubic kilometers/second.

To have this with a wind of 10 m/s (0,01 km/s), you need an opening of 374200 square kilometers. Limiting the height of the suction hose to 10 km, you need to have it 37420 km long, which is roughly the Earth circonference (40075 km).

I don't venture forth in calculation, but I am pretty sure this will disrupt atmospheric circulation as the dust is already doing.

When Designing your Mega Maid, get a hold of the voltron and pwer rangers design teams to creat...Mini Maids. These things will still be enormous, but instead of one giant mega-maid, you add flexibility to your response.

Arrange them close, but not too close, to the point of impact and spread them out from there. Say only a few thousand on the point opposite the point of impact, but they get denser and denser the closer they get to where the projected impact will be. Each Mini Maid will be equipped with a super air chiller to bring the air temp down to normal as it exits the exhaust. Also, efforts to reduce electro-static charge will be made. Finally, condensation that may result from chilling will go through a sprinkler head to create "rain" and help further filter the air.

Finally, once all of the dust has been collected, route all Mini Maids to a remote part of the pacific ocean to empty the collection containers. We will call this collection area...Australia. Any nasty stuff picked up can be taken to Washington DC. Creature remains should be distributed randomly to make future scientists think that the planet had one super continent. We can laugh at them in generations to come.

The point of a clean room, as has been stated, is to achieve many many air changes. One large filtration unit will create devastating effects, but several hundred thousand will probably lessen these to a great degree and be more efficient to boot.

Lets just hope that not too many dinosaurs get sucked up in the process. Those carpet brushes can do a number on small, squeaky things.