A god shows up and it wants to test humanity--see if we are worthy of living. It tells us we have 2 years to slow the rotation of the planet by twenty percent. If it is not slowed by >= 20% in 2 years time, it will destroy the planet (in the thought experiment, everyone on the planet is sure that this will happen--there's no doubt that the god was real, presented itself, gave its terms, and will enforce them). It will be back in 2 years to hold to its word.

Does earth have a chance? Is it such a hard task that we abandon mother earth and start the race to colonize space? Do nations ban together and enforce martial law? Does most of the planet work to slow the rotation and deal with the consequences that would come from doing that while some portion has no faith and parties like its 1999? For some reason I've been thinking a lot lately about what humanity would do if this were to really happen.

Moment of inertia or earth almost I=2.5*M*R^2=9.8*10^37 Kgr*m^2

Kinetic energy from rotation about axis 1/2*I*w^2 w=2*Pi/86400 rad/sec

or 2.6*10^29 Joules. That is to be reduced by 20% to say 0.8*w or loss of 36% of the total rotational energy or 9.4*10^28 J

That is 160 mil times the annual energy consumption of mankind.

So its not gonna happen that easily so fast nomatter how ingenious we get about it or devote all we have to it.

Establishing permanent survival on Mars and the moon and Venus and Ceres and Mercury is piece of cake if we absolutely have to right now. 3D printing instantly becomes 24/7 research priority and at least we buy 200-300 years the settlements will survive until innovation there may recover it to have local factories deliver the same as now on earth.


Initially you need 100 years of head start with multiple backup for most important tools, machines and replacement devices for functionality of colonies. Hopefully in that time frame the industry is redeveloped if 3d printing cannot get you there itself.

At the very least 3d printing must be able to get you back to early 19th century in technology basic tools and some chemistry.

We would need to be able to secure a permanent starting point near 19th century technology far from our current factories with elementary 3d printing methods of basic tools.

We need smelting and basic chemical processing plants in all sites created in closed environment beneath surface radiation protected until more can be developed.

An entire mega purpose factory with many possible products of various utilities need to be developed in as compact size as possible. Definitely something that can create elementary tools.

It is absolutely doable. Multiple parts computers need to be assembled and hopefully we will be able to do semiconductor manufacturing there eventually before all computers have failed in time.

>50k people and all our data and DNA from all species , some well selected animals/plants and all plant seeds easily can survive to live there.

A site that can last 1000 years in resources for up to 100 people can be developed everywhere. In that time they have to find a way to restart it using local resources. Its all about spacesuits and controlled environment and indoors you will recover everything in time if you have some well thought initial degrees of freedom and renewable energy sources.

A full compact nuclear plant can last a century and more if you have spare parts. Solar can keep you ok for centuries too.


The main thing is to establish the minimal effort self sufficient system that can maintain its survival properties indefinitely (ie a closed atmosphere system with water and plants). Then all will be recovered in time due to human ingenuity and current science and technology knowhow.

A dome or underground life support system with artificial light provided by solar from the surface that can constantly be sealed and repaired with minimal technology that is replicated by 3d printing must be achieved.

Solar panels and atmosphere preserving connections/seals that can be created by 3d printing and some semiconductor industry methods of printing will be required to be indefinitely reproduced. Once we have something minimal that preserves life indefinitely and reproduces its parts we will be saved for good.

First we must establish what is the minimal most compact low technology but advanced knowledge system that can be replicated indefinitely supporting inhabitants in it.

The alternative is to have a very good solid start that will survive 100-200-300 years and in that time frame find a way to reproduce computers and chemical industry/manufacturing etc.

We may need to develop in parallel some low tech method (hard to fail and run out of parts) that is self replicated that produces, secures and maintains a sealed standard O2/N2 environment.

I already did. It wasn't a physical test however.

So the goal is to be able to print anything you might need in the future, that way you dont have to be carrying around things you dont need. That makes sense, but there is only so much filament you can carry before you run out. So is the goal to be able to print the tools needed to mine -> make more tools? Or is it to print the tools needed to make a filament factory? Basically we need maker place on each settlement?

Also, just to make sure masq, you are basically saying we dont even try to save the planet because its not likely we could do it?

Given the limited amount of ships / colonies, do we do a merit based system to see who goes, or some sort of lottery, or will it likely be the powerful that end up in space?

Is there no way to alter the earths core or earths mass to slow down rotation that way? I’m sure this will have devasting effects to the planet but those seem unavoidable no matter what just due to the restraints. Seems easy to do but near impossible to do while preserving earths conditions and atmosphere.

Would 7 billion ppl jogging in the opposite direction to Earth's rotation do the trick?

It's worth a try. Most people are morons anyway and this would give them something to do and keep them occupied; thus diminishing all the chaos they cause with their random stupidity.

What happens when they all stop jogging at the same time?

Wouldn’t that would be counterproductive?

If it’s truly impossible, then we’re dealing with a malevolent god who isn’t testing humanity to see if we’re worthy of living, but rather tormenting humanity before inevitably killing us all (wherever we are). So escape is futile; plan cancelled. (Good plan, though).

Either it’s possible to save all of humanity with a test of our humanity, or it doesn’t matter. Our only real option is to prove our humanity by loving one another and having faith the proverbial mountains will be moved and the earth’s rotation slowed.

I wouldn't worry about it. The omnipresent (everywhere at the same time) can’t measure relative velocity, anyway. Tough to come up with a frame of reference if you’re everywhere at the same time.

Pray for a reprieve. Slowing the rotation that much that fast just not going to happen.

Good luck on getting colonies going in space in 2 years but go for it anyways. That's your hail mary pass.

The net angular momentum of the system doesnt change because of that. The rotation of the planet would change a bit if objects in it were rotating also relative to it but its so stupidly ridiculous that you compare the mass of 8*10^9 * 100 kgr even with weights carrying ie 8 *10^11 kgr with 6*10^24 of the planet. Here is where the futility emerges.

If you rotate in the opposite you accelerate it actually although by a tiniest ever bit only still...

When you stop its all back to normal also.


We do have an effect on rotation with global climate change with very tiny effect still because of change of moment of inertia of ice melting.

You need an external torque to make it happen. Convert the planet to a giant sail but still unimportant.


You will all be surprised how easy it is to survive on Mars for 100 years easily if we actually cared to spend 1.5 tril $ to it in 1 year instead of in defense against each other.

I dont give a damn in that case if i live or not. I will live forever the only way that matters to me if i find a way or contribute for some of the species to live.

Proper mix is likely top scientists and engineers say 30% and the other 70% random very healthy not depressed but reasonably educated overall young people. 100k people is enough to save it all. They can take all our DNA with them too.

How's about hooking a chain to the moon?

How about sending a ship to land on a comet and change its path so that it collides with the earth at an angle such that it slows its rotation. Could we all move to one side of the earth and pelt the other with space debris until it slows?

No its not going to happen that way. It will have to be enormous speed to alter the rotation of such huge object as earth (the biggest of all solid planets) . That takes vast energy. At such speed it will destroy the earth by the collision plus it cannot be altered if very massive to achieve that to begin with.

I can calculate it if you are curious for a sideways collision (angular momentum is m*v*b where b is the impact parameter)

I'*w'~I*w+m*v*b, m*v*b needs to be comparable to I*w

I=2/5*M*R^2 R~b here M earth mass m other body mass, R radius of earth w, w' the angular velocity before and after . I~I' here as collision doesnt change I by a lot.



Earth is very dense planet and the asteroids and other minor planets are hundreds to thousands of times smaller in mass and wont make a change as big possible. The smaller that can be manipulated will not even change it 0.01% plus its not gonna happen that fast in 2 years anyway because nothing big is that close that can be taken there.


Just call "God's" bluff. Tell them if they are really ethical they wouldn't be doing that and if they are not ethical then they can be defeated by a more ethical system.


Of course technically the climate change is such an event coming anyway plus there is chance for a true collision anyway eventually that can wipe out civilization and we need to have colonies everywhere soon plus AI can only be risked to be sentient if we are away from earth already and "hedged" or develop it away from earth!

I know you are joking but if you didnt then this thing would collapse under gravity and it cant be built to begin with because it also takes enormous energy to secure its stability against collapse.

Of course there may be ways to entangle the moon electromagnetically to create torques but its still impossibly expensive.

Going to settle other systems in 2 years is super easy in comparison to all this.

People live already in submarines and space stations for years if needed.

In a solid surface the living is 100 times easier actually than it is in space station right now plus offers chances to start using the environment to your benefit like we did for thousands of years anyway.

A minimum of technology plus 100-200 years of supplies can find a solution on Mars in the same type of small steps mankind evolved on earth but with massively more impressive knowledge at start. They will find a way to come out of the dome or cave installation and win over the planet in 100 years of study and experimentation.

First humanity needs to conclude whether it's flat or not. That would waste most of them years. Or perhaps not, since the physics is more or less the same ;p

Party like it's 1999, but hopefully with better music.

Prince is the best, and so were the 90s. GTFO

If there's certain knowledge of God's existence then whatever action we take will be the right action.

A really thick one. Think the moon weighs a bit too little though, and what's more spins in the same direction. The chain will pull the moon towards earth and induce Armageddon btw. And still not getting that 20% off.

Edit, we need to check our numbers: the moon's orbital velocity is about 1 km/s, while the surface of the earth only goes 0.5 km/s at the equator. So the moon would actually speed us up!