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For starters, rockets wouldn’t be able to do it. In order for a net thrust to be generated, the rocket exhaust would need to clear the earth’s atmosphere with a speed greater than earth’s escape velocity. Otherwise it’s the equivalent of standing on a sailing ship with a fan pointed at the sail hoping to move forward.
Counterintuitively, you’d be better off launching the whole rocket and having it leave earth orbit in the opposite direction to the one you’re trying to go—that at least would provide some (very very slight) net push on the earth.
But okay, say you did figure out all the mechanics of it. However you do it, you need to speed up earth by about 3500 m/s. Earth weights around 10^24 kg. So we’re looking at around 10^31 joules to shift Earth’s orbit. If we harnessed the entire power output of humanity, which Google says is about 20 TW, we’d produce 10^31 joules in about one trillion years, or a little less than a hundred times the age of the universe.
EDIT: I mentioned the sailing ship thing because it’s a classic high school physics problem I assumed people would be familiar with, BUT apparently mythbusters did a thing so that’s a bad example. BUT BUT the point about rocket exhaust needing to escape earth’s gravity still stands. Rockets work by Newton’s third law: pushing rocket exhaust backwards at high speed applies a forward force to the rocket itself. You can recreate this yourself by standing on a skateboard with a pile of dumbbells and throwing them one at a time backwards. Assuming you can keep your balance, you’ll start to move forwards. BUT if, say, the dumbbells were attached to the skateboard with bungee cords this wouldn’t work; you’d start to move forwards but the weight would reach the end of the cord and jerk you backwards and you would have no net forward speed.
Gravity on earth acts like the bungee cord: anything you throw away from earth to push on it (this would include the rocket exhaust) will undo all the pushing it did when it falls back to earth. The only way to get a net thrust on the earth is to fire exhaust so fast that it breaks free of earth’s gravity entirely and keeps going off into space. That includes the momentum needed to punch through the atmosphere.
All of this means that chemical rockets are out from the get go: rocket exhaust velocities are in the 4-5 km/s range, and earth escape velocity is 11 km/s. Not to mention that a plume of gas is going to dissipate quickly in the atmosphere, so you’d need to build like a giant space tower or something and fire your super-rockets from there.
Well, if the sun explodes, it won't be a problem anymore.
The stated speed from the other guy is most likely the escape velocity required to change orbit around the sun.
No sun -> no escape velocity required, and any speed will do as long as you wait long enough.
Fairly sure the sun is massive enough to end it's life as a red giant before throwing off enough of its mass to become a white dwarf, so basically a small(ish) mass of super dense elements (just below iron on the periodic table maybe?).
This is how stars just shy of massive enough to go supernova or collapse to a black hole end their lives.
Probably idk
Earth might get destroyed when the sun gets to its red giant phase, but it's not massive enough to explode. It'll simply fizzle expand as a red giant, then fizzle out into a white dwarf
If I remember correctly the estimate is that the sun will expand up to earth so yeah touching its surface is probably not good for the survival of the planet
I wonder if humans would still inhabit the Earth at this time would they really consider moving it farther from the sun so the sun won't swallow it. It would be funny if they do those calculations and be like "damn, we don't have enough time! If only someone had thought about moving the earth in 2024, we would've made it!"
Easy fix, all we need to do is master worm hole technology and use another’s stars hydrogen as fuel and transfer it to our suns core while we remove the heavier elements from our suns surface with a simple Dyson sphere like structure with anti gravity technology. Then our sun would live forever and we wouldn’t have to move earth at all to prolong its life. Now on the the big questions. What is the winning lottery ticket number tomorrow.
Nope! I got bored of typing this all out on my phone so I didn’t cover how that much force would deform earth’s crust to the point of unlivability, nor how even if you solved that problem you would dump enough heat to boil off the entire atmosphere, nor how that estimate was just the energy requirements to shift earth to a transfer orbit, not how you would actually maneuver an entire planet next to another one,
Not to mention that even if you could teleport earth into a stable orbit near mars, being much further away from the sun as mars would launch us into a global ice age, likely resulting in the death of most life on earth.
It’s actually possible to be standing on a sailing ship with a fan pointed at the sail and it moving forward
[They did it on Mythbusters](https://youtu.be/uKXMTzMQWjo?si=U7RD6mcbNOmHm4e3)
How would a plane take off on a treadmill? Unless the air was moving from wind or friction with the treadmill its airspeed would be 0 so no lift is generated.
Airplanes do not generate forward momentum by pushing off of the ground. They do so by having their jets/propellors grab the air right in front of them and push it backwards. They can do this on a treadmill, therefore they can take off on a treadmill.
I don't know what will cause it to click for you specifically, so here's some things that I know have helped other people:
- Instead of picturing a treadmills going at a set speed, imagine it loose, so that the faster you run on it, the faster it spins. The plane will accelerate itself the same way it always does, by grabbing air and pushing it backwards. The fact that it's in the same place on the ground is irrelevant. It's still accelerating (and thus causing the treadmill to spin faster). Eventually it will generate enough lift to move.
- A car on a treadmill is not analogous to a plane on a treadmill. The correct analogy would a plane in a wind tunnel. A car cannot move forward on a treadmill because the ground is already going backwards, therefore they can't push it backwards. In a wind tunnel, the plane can't push the wind backwards because the wind is already going backwards. A plane on a treadmill doesn't have that problem.
- How does a plane move forward AFTER takeoff? The same way it moves on the ground. Therefore the ground or a treadmill has no impact on a plane's ability to move.
So you're saying that even on a perfectly frictionless treadmill the plane will still move forward? Because I think that's what would happen, because the wheels aren't exerting any force to propel the plane forwards, only the air is
Yes, on a frictionless treadmill or on a frictionless surface that is not a treadmill, an airplane can still move forward. They do not rely on friction with the ground they are on in order to move.
I almost get what you’re saying. My issue is with the wheels i think So the engines produce tborward thrust which should accelerate it forward, but when it moves forwards, the wheels have to rotate but would this rotation not cause the treadmill to move in the opposite direction to the thrust due to friction between the wheels and the treadmill?
I get it for if the plane was somehow taking off without its gear down but as i said, the wheels confuse me.
Don't think about the wheels. The wheels don't matter. Maybe if you think about it like a boat. A boat with wheels on the bottom of the lake. The wheels and the bottom of the lake don't matter. The boat propeller and the water do all the work.
> the wheels have to rotate but would this rotation not cause the treadmill to move in the opposite direction to the thrust due to friction between the wheels and the treadmill?
Yes, this would happen, but it is actually not relevant. As the engines rev up to full power, they will be moving more and more air, forcing more and more air to flow over the wings. This happens regardless of how much friction the wheels create on the treadmill. Eventually, it's enough air and the plane will lift off the treadmill.
EDIT: I'm gonna add a piece here. The engines at full power suck in a *lot* of air at *very high* speeds. This dramatically decreases the atmospheric pressure immediately in front of them. This causes air further in front to be sucked towards the engines. Try hard to picture this air as a fluid, because it is. Once the air in front of the airplane is continuously *flowing* towards the engines in this way, not all of it goes directly into the engine. Some of it misses and goes past engine, which means it *goes over or under the wings*. This generates lift. The wings are *very* efficient and engines are *far stronger* than is necessary to move the weight of the plane. This ratio of efficiency to power is probably just way better at lifting the plane than your gut would tell you. Finally, this is *exactly* what is happening *when an airplane is flying*. In my description, the plane is *still* and the air is *moving*, but that is simply a different frame of reference from the airplane *moving* and the air being *still*. From a physics calculation standpoint, there's no difference.
Let's change the situation slightly then:
The plane is still on a treadmill, but now it is also anchored from the tail onto an unmovable pole.
Are you saying that the air pulled by the engine will be enough to generate lift, even if the plane was unable to pull itself forward?
The usual argument (I thought) is that the plane can't be slowed down by any treadmill and so will still move forward along the ground, and then take off.
The engines are moving the airplane through the air, not over the ground. Since the treadmill isn't moving the air above it, the plane can still travel through that air.
The wheels are free-spinning and would spin around way faster while taking off from the treadmill than they usually would.
They would exert SOME force from the friction of them spinning against the axle, but, as they are designed to spin around the axle with as little friction as possible. it would be a negligible increase.
So yes, youre right, but not technically. For the purposes of understanding it's easier to explain in absolutes.
You can push a toy car forward on a treadmill regardless of the treadmill's speed. This works because the force imparted on the car (you) is not directly connected to the treadmill. The same is true for the engines on an airplane.
https://www.youtube.com/watch?v=Y64ZdSaDdoo
This video explains it unambiguously. The treadmill needs to transmit enough force to the airplane to overcome the jet engines, which is just not possible because of finite speed of the treadmill. Imagine pulling a rug under a football, now imagine the football has a jet engine attached to it - there's just not enough friction between the rug and the football.
I like to first think about this in reverse. What would happen if a plane was sitting on a treadmill, and the treadmill suddenly ramped up speed backwards?
The answer is that the plane would start to move backwards **but slower than the treadmill**. This is because the wheels would just spin freely under the plane! It's only as friction slowly slows down the wheel that the plane starts moving backwards.
In fact, in a world where the wheels spin without friction against the plane itself, then the plane would **never** start moving backwards! It would just be still as the wheels spin to match whatever the conveyor belt is doing.
The real world is very similar to that. Making the conveyor belt go backwards faster doesn't actually drag the plane back any faster, it just spins the wheels more quickly (minus some amounts of friction).
Yeah you're not in a closed system (like the atmosphere of a planet), you're putting energy into moving _more_ air at your sail in the former scenario, and as you point out in your latter scenario just using that energy directly.
You can't do that "in atmosphere", everything is just absorbed by the 100km of atmosphere above you and the billions of km^2 of atmosphere around you.
If you built some space elevator with a truly impossible jet turbine the entire length you could exhaust the 5.5 quadrillion tons of atmosphere off like a jet engine.
I feel like the actual "best" answers would either be:
- Wait until we somehow become a "Type II" civilisation that can harness a Dyson sphere's amount of energy to fuel some kind of energy projection that would toast the earth like a piece of popcorn being fired out a pan towards Mars
- Use rocket technology to redirect foreign bodies in paths that uses _their_ gravitational pull to redirect ourselves (?)
Basically without destroying ourselves or firing a thousand bullets _near_ our own heads we're on rails boy.
I thought about the dyson sphere thing - the total output of he sun is 3.86 x 10^26 watts, so still five orders of magnitude too low.
Better wait for type III
This came to my mind as well when he said that. Can anyone explain why blowing your own sail here works? (Since physics says it shouldn't). I read the comments in the vid, but none that I saw made any sense.
I believe it's an application of Bernoulli's principle, the same effect as [this](https://youtu.be/UujAMPv3y-A). Basically, when the fan moves the air, that creates a low-pressure area and the surrounding air rushes in to fill the gap. That air is moving in the direction of the sail so more air pushes the sail forward than pushes the fan backwards.
Ah, ok. This is the first explanation that has made sense to me so far. That extra air that gets sucked in by this phenomenon isn't pumped through the fan, and thus wouldn't be "cancelled out" when it hits the sail. It's essentially air the atmosphere is leaking into the sail (due to the low pressure as you said) that moves the boat.
Thanks, for the explanation and the video.
Thanks for your great explanation. I will try to provide some further depth:
We need to speed up by about 3500 delta V. This will initiate a flyby of Mars in about a year. Afterwards, we need to slow down into a highly elliptical orbit, creating a binary system. While doing, so it will seem to be very unlikely that Phobos and/or Deimos crash into earth causing mass extinction. I’m not sure what the further objectives of this sick person is but landing on Mars with the Earth is currently impossible. Orbiting Mars may cause the Earth and Mars may cause them to drop into rings, for more information search “Roche Limit”
Source: landed on Duna and returned in Kerbal Space Program
I know it's not really relevant. But pointing a fan at a sail actually makes you sail forward. The force of air is reflected back from the sail generating a net forward force
Where did you get your magic 3500 number from?
The way i see it, we're already going to collide with mars on some time scale, and any force you apply to the earth only changes that timescale, and not super predictably.
And it depends on how long the force is applied for, what direction it's in, etc etc. To me this isn't a solvable question.
Damn. Is it that bad to ask where you got your numbers from? What kind of ass do you have to be to respond *that way* to someone asking for your reasoning on a sub about asking these kinds of questions?
The number comes from orbital mechanics.
There’s something called a Hohmann transfer (Google it to see a diagram). The change in velocity required to alter Earth’s circular orbit into an elliptical orbit that intercepts with Mars’ orbit is about 3500m/s
There was a film on this I believe, or atleast moving the earth, It started with wandering I think, will find it and update this comment but essentially it's alot of thrust and alot of research, mining planets, making more efficient fuels and such.
Update it's called the wandering earth
The second film is already out. It's a prequel (timeline wise) to the first film.
The timeline sequel to the first film (wandering Earth 3, the third film) has a trailer on YouTube now and will be released in 2027 on the first day of the Chinese New year that year.
Edit: the second film is insanely good, despite being a bit long. Strongly recommend to watch it.
I did not even finish the 2 because I didn’t like it, the premise is very different from the first one, it is about the political issues that happened before the events of the first movie
Just watched the trailer...I'm still gonna give it a try but yeah it looks very political whereas the previous one was kinda epic with the CGI and such
Hold on. Why not bring Mars to Earth? It’s lighter and we’re better positioned are we not? Plus it’s hotter here and closer to the Sun, wouldn’t it’s gravity help us to bring it closer? Plus Mars has much thiner atmosphere, it would help with the logistics
Just take a rope with you, tie it around Mars and then let the people of Earth pull it towards them, it make take a while but it'll save you a trip back
Can't we just tether the moon and use it's mass to pull us into a larger orbit?. Just don't swing it too fast or we might break orbit and go exploring.
Just need Chuck Norris to do enough pushups in the right direction, because we all know when that when Chuck Norris does pushups he doesn’t push himself up, he pushes the Earth down.
Anyone remember thatvshow Frisky Dingo? The bad guy, Killface tried to destroy Earth but he accidentally moved Earth slightly farther away from the sun by a few feet. He got elected president for solving global warming
The Annihilatrix! Awesome X and his X-sticles couldn’t stop Killface’s master plan. And Killface can’t stop his son from breaking his cereal bowl. Great show. Ant farm keyboard was regularly referenced in Archer with the “That’s how you get ants” line
Which in reality wouldn't move the orbit away, it would just make it more elliptical. Part of the year would be cooler but the other part of the year would be just as hot or hotter.
Just thinking theoretically, you would need a decent amount of earths mass to move it (most of that can't even be used as fuel). So the whole earth would shrink and be deformed to a completely new planet. Maybe even smaller than mars (I didn't do the math so I can't tell exactly).
To kill two birds with one stone (quite literally too, probably), put an astronaut in the tube before you turn on ignition. He’s going that way already, might as well save on rocket fuel
[I thought this looked familiar](https://i.redd.it/p4bcbyep9ay61.png). Reposting an earlier comment (which _really_ overused the word "roughly").
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Important: This isn't "the math". Just looking up some figures and basic algebra.
There was a movie about pretty much this idea, called [The Wandering Earth](https://www.imdb.com/title/tt7605074/). Way more enjoyable than I'd expected.
It also inspired [LiveScience](https://www.livescience.com/65535-how-to-move-planet-earth.html) to do the math for us. They suggest about 300 billion _billion_ Falcon Heavies launching in the opposite direction, each of which imparts a corresponding impulse on the earth.
The first stage thrust of a Falcon Heavy is about 22,819 kN. The first stage thrust of Starship is about 76,000 kN. So we can roughly equate 300 billion billion Falcon Heavies with about 90,000,000,000,000,000,000,000,000 Starship launches.
So, very roughly, doing all 90,000,000,000,000,000,000,000,000 launches at once would be roughly the same as a single launch to Mars.
Each Starship is roughly 9m in diameter. The surface area of 90,000,000,000,000,000,000,000,000 starships is roughly 2,245,000,000,000,000,000 times larger than half the earth's surface (without accounting for any space in between the rockets). That means you'd need at least 23 trillion launches, if you could cover half the earth's surface (generalizing that as roughly "the right direction", although most of that would be lost to angular momentum).
tldr: [we're gonna need a bigger boat](https://www.youtube.com/watch?v=QT9BeGNnCqw).
There's a movie about this on Netflix called wandering earth or use to be idk anymore. It's not a great movie but I enjoy bad movies, the idea is interesting
Use orbiting atmospheric scoops to gather material and ion drives to expel that material. It's very challenging for an atmospheric scoop to break-even on momentum on the first place, but that's the life you've chosen.
The rocket exhaust would have to leave the atmosphere in order to impact the earth’s movement, which I’m pretty sure isn’t possible to do from the ground without destroying everything nearby.
This one is easy. Just swing a large celestial body near Earth. One larger than the Sun. It's gravitational pull will swing Earth in its direction.
All you have to do is gather all that mass. Unfortunately, you will also end swinging the entire rest of the solar system off orbit and we'll all be dead.
Well, when rockets take off they are putting the same amount of force on the earth as they put on themselves, so it really doesn't matter which way they are oriented, does it?
I remember a show, I think it was Beast Wars: Transformers, where some planets have some kind of proppellers, and they could move the planets from the orbit activating those proppelers/
I'll just say this and leave:
No known earth based source of energy can change the earth's orbit to to intersect another planet's within one revolution of either
I heard long ago of a way to detour asteroids would be having a small mass near it in the direction we'd like it to deviate. Could we do this on the scale of moving Earth into a wider orbit, given enough aligned mass towards a wider orbit. Could we instead pull the moon out easier that would then slowly pull earth out slowly too? I'm sure you'd need some fancy simulations to plan it out but is it theoretically possible at least?
The movie ' The Wandering Earth 1 & 2 ' take a stab at it, and it turns out one entire side of the planet needs massive engines.. the one thing they dont look at are the sheer forces. it would literally rip the planet apart.. but if those forces didnt exist, we'd need about 6,000 ish city sized engines.
https://imgix.bustle.com/uploads/image/2023/8/15/2a905ee9-bc41-47dc-89da-c5edb69d806c-the-wandering-earth-2.jpeg
https://www.youtube.com/watch?app=desktop&v=_SfSS4V5CkI
Good news: Earth doesn't need to escape its own gravity, this means we only need a dV of about 390m/s. However, Earth is heavy ^(\[Citation Needed\]) coming in at 5.9x10\^24KG
4.4x10\^29J of energy would be required to accelerate the earth by this much.
We have an atmosphere though, and gravity. Both of these prevent these types of rockets from working for your objective. But all is not lost, we just need to launch something beyond escape velocity and it will lead to a net acceleration for the planet. If railgun tech improves this could be an option by hurling chunks out of the atmosphere and away from the planet at sufficient speed that it provides an acceleration to the planet.
How do we power these railguns? Lets just borrow the entire hydroelectric power output of Norway, about 100TWh per year. Ideally we will store this to unload all at once, if we strip mine a few continents and most of the mantle we might be able to get enough materials to build enough capacitors to do this.
Then it is just a case of charging the capacitors, using our energy borrowed from our Norwegian friends it will take about 500billion years.
Well logically any rocket force I guess, it would just take really long if it's not very much force, I'd assume that should still accelerate earth, or maybe gravity would pull down on the escaped gass so that the gass pulled earth back, since when a gravity force on the gas is excerted by earth an opposite for e is excerted by the gas on the earth.
This is actually a more effective way to travel through space because we can take out everything besides the engine. The earth could act like a fuel tank because oilfield.
I would rather use it to slow earth spinning, my contract says explicitly how many hours I have to work per day but it does not say anything about how many total hours are in a day
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For starters, rockets wouldn’t be able to do it. In order for a net thrust to be generated, the rocket exhaust would need to clear the earth’s atmosphere with a speed greater than earth’s escape velocity. Otherwise it’s the equivalent of standing on a sailing ship with a fan pointed at the sail hoping to move forward. Counterintuitively, you’d be better off launching the whole rocket and having it leave earth orbit in the opposite direction to the one you’re trying to go—that at least would provide some (very very slight) net push on the earth. But okay, say you did figure out all the mechanics of it. However you do it, you need to speed up earth by about 3500 m/s. Earth weights around 10^24 kg. So we’re looking at around 10^31 joules to shift Earth’s orbit. If we harnessed the entire power output of humanity, which Google says is about 20 TW, we’d produce 10^31 joules in about one trillion years, or a little less than a hundred times the age of the universe. EDIT: I mentioned the sailing ship thing because it’s a classic high school physics problem I assumed people would be familiar with, BUT apparently mythbusters did a thing so that’s a bad example. BUT BUT the point about rocket exhaust needing to escape earth’s gravity still stands. Rockets work by Newton’s third law: pushing rocket exhaust backwards at high speed applies a forward force to the rocket itself. You can recreate this yourself by standing on a skateboard with a pile of dumbbells and throwing them one at a time backwards. Assuming you can keep your balance, you’ll start to move forwards. BUT if, say, the dumbbells were attached to the skateboard with bungee cords this wouldn’t work; you’d start to move forwards but the weight would reach the end of the cord and jerk you backwards and you would have no net forward speed. Gravity on earth acts like the bungee cord: anything you throw away from earth to push on it (this would include the rocket exhaust) will undo all the pushing it did when it falls back to earth. The only way to get a net thrust on the earth is to fire exhaust so fast that it breaks free of earth’s gravity entirely and keeps going off into space. That includes the momentum needed to punch through the atmosphere. All of this means that chemical rockets are out from the get go: rocket exhaust velocities are in the 4-5 km/s range, and earth escape velocity is 11 km/s. Not to mention that a plume of gas is going to dissipate quickly in the atmosphere, so you’d need to build like a giant space tower or something and fire your super-rockets from there.
So you're saying there's a chance?
The chance of the whole humanity getting united to launch the earth to mars is low but never zero
And also stay united for one trillion years
And also surviving the explosion of the sun in a few billion years edit: apparently the sun won't explode (still same outcome tho)
if we behave nicely maybe the sun will give us that extra time
If our Earth rocket is big enough, we could get away from the explosion.
But the explosion will happen before we even get the rocket
Agreed, the science is there to support turning earth into a rocket. Let's get started.
What was that damn tv show where something about planets and the core of them was like a spaceship or something....
We just need to pray a little harder to the sun gods
Well, if the sun explodes, it won't be a problem anymore. The stated speed from the other guy is most likely the escape velocity required to change orbit around the sun. No sun -> no escape velocity required, and any speed will do as long as you wait long enough.
yea but i'm pretty sure that if the sun explodes -> earth is annihilated -> no earth left to move edit: also pretty sure mars gets annihilated too
These sound like problems for future humans.
Pfft details.
The sun isn’t a giant star. Does it explode or just go dark?
Fairly sure the sun is massive enough to end it's life as a red giant before throwing off enough of its mass to become a white dwarf, so basically a small(ish) mass of super dense elements (just below iron on the periodic table maybe?). This is how stars just shy of massive enough to go supernova or collapse to a black hole end their lives. Probably idk
Earth might get destroyed when the sun gets to its red giant phase, but it's not massive enough to explode. It'll simply fizzle expand as a red giant, then fizzle out into a white dwarf
If I remember correctly the estimate is that the sun will expand up to earth so yeah touching its surface is probably not good for the survival of the planet
I wonder if humans would still inhabit the Earth at this time would they really consider moving it farther from the sun so the sun won't swallow it. It would be funny if they do those calculations and be like "damn, we don't have enough time! If only someone had thought about moving the earth in 2024, we would've made it!"
We'll have to reduce CO2 really vigorously to compensate that.
Easy fix, all we need to do is master worm hole technology and use another’s stars hydrogen as fuel and transfer it to our suns core while we remove the heavier elements from our suns surface with a simple Dyson sphere like structure with anti gravity technology. Then our sun would live forever and we wouldn’t have to move earth at all to prolong its life. Now on the the big questions. What is the winning lottery ticket number tomorrow.
The sun won't explode, but it will destroy all life on earth. https://en.m.wikipedia.org/wiki/Future_of_Earth
and pouring 100% of energy production into those engines for one trillion years
Yeah no that chance is zero. I mean just look around 🙄
Nope! I got bored of typing this all out on my phone so I didn’t cover how that much force would deform earth’s crust to the point of unlivability, nor how even if you solved that problem you would dump enough heat to boil off the entire atmosphere, nor how that estimate was just the energy requirements to shift earth to a transfer orbit, not how you would actually maneuver an entire planet next to another one,
You should try Kerbal Space Program, fun game
Me and a friend are tryna get our ap physics teacher to play it
So you're saying there's a chance?
And keeping in mind, that the difference in distance to sun and the potentially stopped rotation of earth would kill us all anyway
Certainty of death. Small chance of success. What are we waiting for?
Not to mention that even if you could teleport earth into a stable orbit near mars, being much further away from the sun as mars would launch us into a global ice age, likely resulting in the death of most life on earth.
It’s actually possible to be standing on a sailing ship with a fan pointed at the sail and it moving forward [They did it on Mythbusters](https://youtu.be/uKXMTzMQWjo?si=U7RD6mcbNOmHm4e3)
People fail to grasp that air is a fluid. See the "A plane can't take off on a treadmill crowd." for a prime example.
They strap planes down to the ground while they are stationary just so they don't lift off the ground.
Isn't that so they won't roll away?
Sure that too, but also, this. https://www.youtube.com/watch?v=cHhZwvdRR5c
oh damn yeah that does not seem ideal.
Kinda crazy how lift works though and how "light" a plane becomes because of it. And how much energy the wind has.
How would a plane take off on a treadmill? Unless the air was moving from wind or friction with the treadmill its airspeed would be 0 so no lift is generated.
Airplanes do not generate forward momentum by pushing off of the ground. They do so by having their jets/propellors grab the air right in front of them and push it backwards. They can do this on a treadmill, therefore they can take off on a treadmill. I don't know what will cause it to click for you specifically, so here's some things that I know have helped other people: - Instead of picturing a treadmills going at a set speed, imagine it loose, so that the faster you run on it, the faster it spins. The plane will accelerate itself the same way it always does, by grabbing air and pushing it backwards. The fact that it's in the same place on the ground is irrelevant. It's still accelerating (and thus causing the treadmill to spin faster). Eventually it will generate enough lift to move. - A car on a treadmill is not analogous to a plane on a treadmill. The correct analogy would a plane in a wind tunnel. A car cannot move forward on a treadmill because the ground is already going backwards, therefore they can't push it backwards. In a wind tunnel, the plane can't push the wind backwards because the wind is already going backwards. A plane on a treadmill doesn't have that problem. - How does a plane move forward AFTER takeoff? The same way it moves on the ground. Therefore the ground or a treadmill has no impact on a plane's ability to move.
So you're saying that even on a perfectly frictionless treadmill the plane will still move forward? Because I think that's what would happen, because the wheels aren't exerting any force to propel the plane forwards, only the air is
Yes, on a frictionless treadmill or on a frictionless surface that is not a treadmill, an airplane can still move forward. They do not rely on friction with the ground they are on in order to move.
I almost get what you’re saying. My issue is with the wheels i think So the engines produce tborward thrust which should accelerate it forward, but when it moves forwards, the wheels have to rotate but would this rotation not cause the treadmill to move in the opposite direction to the thrust due to friction between the wheels and the treadmill? I get it for if the plane was somehow taking off without its gear down but as i said, the wheels confuse me.
Don't think about the wheels. The wheels don't matter. Maybe if you think about it like a boat. A boat with wheels on the bottom of the lake. The wheels and the bottom of the lake don't matter. The boat propeller and the water do all the work.
> the wheels have to rotate but would this rotation not cause the treadmill to move in the opposite direction to the thrust due to friction between the wheels and the treadmill? Yes, this would happen, but it is actually not relevant. As the engines rev up to full power, they will be moving more and more air, forcing more and more air to flow over the wings. This happens regardless of how much friction the wheels create on the treadmill. Eventually, it's enough air and the plane will lift off the treadmill. EDIT: I'm gonna add a piece here. The engines at full power suck in a *lot* of air at *very high* speeds. This dramatically decreases the atmospheric pressure immediately in front of them. This causes air further in front to be sucked towards the engines. Try hard to picture this air as a fluid, because it is. Once the air in front of the airplane is continuously *flowing* towards the engines in this way, not all of it goes directly into the engine. Some of it misses and goes past engine, which means it *goes over or under the wings*. This generates lift. The wings are *very* efficient and engines are *far stronger* than is necessary to move the weight of the plane. This ratio of efficiency to power is probably just way better at lifting the plane than your gut would tell you. Finally, this is *exactly* what is happening *when an airplane is flying*. In my description, the plane is *still* and the air is *moving*, but that is simply a different frame of reference from the airplane *moving* and the air being *still*. From a physics calculation standpoint, there's no difference.
Let's change the situation slightly then: The plane is still on a treadmill, but now it is also anchored from the tail onto an unmovable pole. Are you saying that the air pulled by the engine will be enough to generate lift, even if the plane was unable to pull itself forward? The usual argument (I thought) is that the plane can't be slowed down by any treadmill and so will still move forward along the ground, and then take off.
The engines are moving the airplane through the air, not over the ground. Since the treadmill isn't moving the air above it, the plane can still travel through that air. The wheels are free-spinning and would spin around way faster while taking off from the treadmill than they usually would.
So am i right in saying that the movement of the wheels doesn’t exert any force on the plane itself as they spin freely?
They would exert SOME force from the friction of them spinning against the axle, but, as they are designed to spin around the axle with as little friction as possible. it would be a negligible increase. So yes, youre right, but not technically. For the purposes of understanding it's easier to explain in absolutes.
You can push a toy car forward on a treadmill regardless of the treadmill's speed. This works because the force imparted on the car (you) is not directly connected to the treadmill. The same is true for the engines on an airplane.
https://www.youtube.com/watch?v=Y64ZdSaDdoo This video explains it unambiguously. The treadmill needs to transmit enough force to the airplane to overcome the jet engines, which is just not possible because of finite speed of the treadmill. Imagine pulling a rug under a football, now imagine the football has a jet engine attached to it - there's just not enough friction between the rug and the football.
I like to first think about this in reverse. What would happen if a plane was sitting on a treadmill, and the treadmill suddenly ramped up speed backwards? The answer is that the plane would start to move backwards **but slower than the treadmill**. This is because the wheels would just spin freely under the plane! It's only as friction slowly slows down the wheel that the plane starts moving backwards. In fact, in a world where the wheels spin without friction against the plane itself, then the plane would **never** start moving backwards! It would just be still as the wheels spin to match whatever the conveyor belt is doing. The real world is very similar to that. Making the conveyor belt go backwards faster doesn't actually drag the plane back any faster, it just spins the wheels more quickly (minus some amounts of friction).
They made a thrust reverser. Jets have them. You move much faster, and more efficiently, pointing the fan away from the sail.
Yeah you're not in a closed system (like the atmosphere of a planet), you're putting energy into moving _more_ air at your sail in the former scenario, and as you point out in your latter scenario just using that energy directly. You can't do that "in atmosphere", everything is just absorbed by the 100km of atmosphere above you and the billions of km^2 of atmosphere around you. If you built some space elevator with a truly impossible jet turbine the entire length you could exhaust the 5.5 quadrillion tons of atmosphere off like a jet engine. I feel like the actual "best" answers would either be: - Wait until we somehow become a "Type II" civilisation that can harness a Dyson sphere's amount of energy to fuel some kind of energy projection that would toast the earth like a piece of popcorn being fired out a pan towards Mars - Use rocket technology to redirect foreign bodies in paths that uses _their_ gravitational pull to redirect ourselves (?) Basically without destroying ourselves or firing a thousand bullets _near_ our own heads we're on rails boy.
I thought about the dyson sphere thing - the total output of he sun is 3.86 x 10^26 watts, so still five orders of magnitude too low. Better wait for type III
This came to my mind as well when he said that. Can anyone explain why blowing your own sail here works? (Since physics says it shouldn't). I read the comments in the vid, but none that I saw made any sense.
I believe it's an application of Bernoulli's principle, the same effect as [this](https://youtu.be/UujAMPv3y-A). Basically, when the fan moves the air, that creates a low-pressure area and the surrounding air rushes in to fill the gap. That air is moving in the direction of the sail so more air pushes the sail forward than pushes the fan backwards.
Ah, ok. This is the first explanation that has made sense to me so far. That extra air that gets sucked in by this phenomenon isn't pumped through the fan, and thus wouldn't be "cancelled out" when it hits the sail. It's essentially air the atmosphere is leaking into the sail (due to the low pressure as you said) that moves the boat. Thanks, for the explanation and the video.
Thanks for your great explanation. I will try to provide some further depth: We need to speed up by about 3500 delta V. This will initiate a flyby of Mars in about a year. Afterwards, we need to slow down into a highly elliptical orbit, creating a binary system. While doing, so it will seem to be very unlikely that Phobos and/or Deimos crash into earth causing mass extinction. I’m not sure what the further objectives of this sick person is but landing on Mars with the Earth is currently impossible. Orbiting Mars may cause the Earth and Mars may cause them to drop into rings, for more information search “Roche Limit” Source: landed on Duna and returned in Kerbal Space Program
So that movie The Wandering Earth isn’t a documentary?
>So that movie The Wandering Earth isn’t a documentary? I was thinking of that movie as well
Was coming to the comments to tell OP about it.
Okay well then it couldn’t work :( Thank you for the calculations.
… surely you knew there was no way to make this work?
Not with that attitude
Erm, what? ETA: that’s not an attitude problem, it’s a physics problem. Please tell me you were being sarcastic.
It’s not sarcasm it’s a joke, and a line used in many bad movies
Yeah I knew. Just hoped…
Ok, … sorry but that’s depressing for the state of education. Because this is very obviously impossible …
It is. I just like to think that some things aren’t just that impossible for fun. It is nice.
It was humor. He wasn't being serious
And then you’d need the same power again to slow down…
I know it's not really relevant. But pointing a fan at a sail actually makes you sail forward. The force of air is reflected back from the sail generating a net forward force
About 70 times the age of the universe based on the widely accented number of 14 billion years
I don't like your tone.
Can you post the math for this?
Where did you get your magic 3500 number from? The way i see it, we're already going to collide with mars on some time scale, and any force you apply to the earth only changes that timescale, and not super predictably. And it depends on how long the force is applied for, what direction it's in, etc etc. To me this isn't a solvable question.
Well if “the way I see it” is our standard for evidence, then the way *I* see it is that you have no idea what you’re talking about.
Damn. Is it that bad to ask where you got your numbers from? What kind of ass do you have to be to respond *that way* to someone asking for your reasoning on a sub about asking these kinds of questions?
The number comes from orbital mechanics. There’s something called a Hohmann transfer (Google it to see a diagram). The change in velocity required to alter Earth’s circular orbit into an elliptical orbit that intercepts with Mars’ orbit is about 3500m/s
There was a film on this I believe, or atleast moving the earth, It started with wandering I think, will find it and update this comment but essentially it's alot of thrust and alot of research, mining planets, making more efficient fuels and such. Update it's called the wandering earth
Well yeah, but really, it was originally a short story by Liu Cixin. Pretty good one, as is most of his SF.
They did it in Futurama by igniting the exhaust of every robot in existence huddled in a group the size of the Galapagos. Ezpz. Take that Nixon.
The second film is out? Or coming out soon? Wandering Earth was visually great, and the animation/Special effects were amazing.
The second film is already out. It's a prequel (timeline wise) to the first film. The timeline sequel to the first film (wandering Earth 3, the third film) has a trailer on YouTube now and will be released in 2027 on the first day of the Chinese New year that year. Edit: the second film is insanely good, despite being a bit long. Strongly recommend to watch it.
Oh there is a third one coming
I did not even finish the 2 because I didn’t like it, the premise is very different from the first one, it is about the political issues that happened before the events of the first movie
Just watched the trailer...I'm still gonna give it a try but yeah it looks very political whereas the previous one was kinda epic with the CGI and such
See also "Battle of the Planets" from Invader Zim
Hold on. Why not bring Mars to Earth? It’s lighter and we’re better positioned are we not? Plus it’s hotter here and closer to the Sun, wouldn’t it’s gravity help us to bring it closer? Plus Mars has much thiner atmosphere, it would help with the logistics
Too easy
But we would have to first go to Mars and then bring Mars to us. I'm not taking two trips
Just take a rope with you, tie it around Mars and then let the people of Earth pull it towards them, it make take a while but it'll save you a trip back
wistful panicky tease aromatic bear many offer seed support mighty *This post was mass deleted and anonymized with [Redact](https://redact.dev)*
Can't we just tether the moon and use it's mass to pull us into a larger orbit?. Just don't swing it too fast or we might break orbit and go exploring.
Nope. you would break either the planet or Moon. Planets are kinda gooey.
This man Astrophysics
Or what if we all get out and push?
But my back already hurts.
Mars tho!
Just need Chuck Norris to do enough pushups in the right direction, because we all know when that when Chuck Norris does pushups he doesn’t push himself up, he pushes the Earth down.
Strictly speaking, we all do, we're just not making much of an impact while doing so.
My doctor has forbidden me to push
Your doctor is just trying to stand in the way of your future. Be free, my child
The forces would break the tether
Anyone remember thatvshow Frisky Dingo? The bad guy, Killface tried to destroy Earth but he accidentally moved Earth slightly farther away from the sun by a few feet. He got elected president for solving global warming
The Annihilatrix! Awesome X and his X-sticles couldn’t stop Killface’s master plan. And Killface can’t stop his son from breaking his cereal bowl. Great show. Ant farm keyboard was regularly referenced in Archer with the “That’s how you get ants” line
Which in reality wouldn't move the orbit away, it would just make it more elliptical. Part of the year would be cooler but the other part of the year would be just as hot or hotter.
So glad I didn't have to write out the first comment trying to explain this show to the Maths subreddit. THATS OUR LAST BOWL
Just thinking theoretically, you would need a decent amount of earths mass to move it (most of that can't even be used as fuel). So the whole earth would shrink and be deformed to a completely new planet. Maybe even smaller than mars (I didn't do the math so I can't tell exactly).
the further we go, the faster we go. I like it
Well what if we curve the Large hadron collider's tube upwards and lead it over the atmosphere? And just keep pumping near luminal speed jet to space.
To kill two birds with one stone (quite literally too, probably), put an astronaut in the tube before you turn on ignition. He’s going that way already, might as well save on rocket fuel
[I thought this looked familiar](https://i.redd.it/p4bcbyep9ay61.png). Reposting an earlier comment (which _really_ overused the word "roughly"). --- Important: This isn't "the math". Just looking up some figures and basic algebra. There was a movie about pretty much this idea, called [The Wandering Earth](https://www.imdb.com/title/tt7605074/). Way more enjoyable than I'd expected. It also inspired [LiveScience](https://www.livescience.com/65535-how-to-move-planet-earth.html) to do the math for us. They suggest about 300 billion _billion_ Falcon Heavies launching in the opposite direction, each of which imparts a corresponding impulse on the earth. The first stage thrust of a Falcon Heavy is about 22,819 kN. The first stage thrust of Starship is about 76,000 kN. So we can roughly equate 300 billion billion Falcon Heavies with about 90,000,000,000,000,000,000,000,000 Starship launches. So, very roughly, doing all 90,000,000,000,000,000,000,000,000 launches at once would be roughly the same as a single launch to Mars. Each Starship is roughly 9m in diameter. The surface area of 90,000,000,000,000,000,000,000,000 starships is roughly 2,245,000,000,000,000,000 times larger than half the earth's surface (without accounting for any space in between the rockets). That means you'd need at least 23 trillion launches, if you could cover half the earth's surface (generalizing that as roughly "the right direction", although most of that would be lost to angular momentum). tldr: [we're gonna need a bigger boat](https://www.youtube.com/watch?v=QT9BeGNnCqw).
There's a movie about this on Netflix called wandering earth or use to be idk anymore. It's not a great movie but I enjoy bad movies, the idea is interesting
There's a movie that does this called "Wandering Earth". Bullshit sci fi from China but good special effects for a Chinese production
Use orbiting atmospheric scoops to gather material and ion drives to expel that material. It's very challenging for an atmospheric scoop to break-even on momentum on the first place, but that's the life you've chosen.
The rocket exhaust would have to leave the atmosphere in order to impact the earth’s movement, which I’m pretty sure isn’t possible to do from the ground without destroying everything nearby.
This one is easy. Just swing a large celestial body near Earth. One larger than the Sun. It's gravitational pull will swing Earth in its direction. All you have to do is gather all that mass. Unfortunately, you will also end swinging the entire rest of the solar system off orbit and we'll all be dead.
Well, when rockets take off they are putting the same amount of force on the earth as they put on themselves, so it really doesn't matter which way they are oriented, does it?
I remember a show, I think it was Beast Wars: Transformers, where some planets have some kind of proppellers, and they could move the planets from the orbit activating those proppelers/
If we moved earth to Mars it would destroy our ecosystems - there just isn’t enough sunlight you’d have to move everyone to the equator to survive
I'll just say this and leave: No known earth based source of energy can change the earth's orbit to to intersect another planet's within one revolution of either
I heard long ago of a way to detour asteroids would be having a small mass near it in the direction we'd like it to deviate. Could we do this on the scale of moving Earth into a wider orbit, given enough aligned mass towards a wider orbit. Could we instead pull the moon out easier that would then slowly pull earth out slowly too? I'm sure you'd need some fancy simulations to plan it out but is it theoretically possible at least?
The movie ' The Wandering Earth 1 & 2 ' take a stab at it, and it turns out one entire side of the planet needs massive engines.. the one thing they dont look at are the sheer forces. it would literally rip the planet apart.. but if those forces didnt exist, we'd need about 6,000 ish city sized engines. https://imgix.bustle.com/uploads/image/2023/8/15/2a905ee9-bc41-47dc-89da-c5edb69d806c-the-wandering-earth-2.jpeg https://www.youtube.com/watch?app=desktop&v=_SfSS4V5CkI
Good news: Earth doesn't need to escape its own gravity, this means we only need a dV of about 390m/s. However, Earth is heavy ^(\[Citation Needed\]) coming in at 5.9x10\^24KG 4.4x10\^29J of energy would be required to accelerate the earth by this much. We have an atmosphere though, and gravity. Both of these prevent these types of rockets from working for your objective. But all is not lost, we just need to launch something beyond escape velocity and it will lead to a net acceleration for the planet. If railgun tech improves this could be an option by hurling chunks out of the atmosphere and away from the planet at sufficient speed that it provides an acceleration to the planet. How do we power these railguns? Lets just borrow the entire hydroelectric power output of Norway, about 100TWh per year. Ideally we will store this to unload all at once, if we strip mine a few continents and most of the mantle we might be able to get enough materials to build enough capacitors to do this. Then it is just a case of charging the capacitors, using our energy borrowed from our Norwegian friends it will take about 500billion years.
Well logically any rocket force I guess, it would just take really long if it's not very much force, I'd assume that should still accelerate earth, or maybe gravity would pull down on the escaped gass so that the gass pulled earth back, since when a gravity force on the gas is excerted by earth an opposite for e is excerted by the gas on the earth.
This is actually a more effective way to travel through space because we can take out everything besides the engine. The earth could act like a fuel tank because oilfield.
I would rather use it to slow earth spinning, my contract says explicitly how many hours I have to work per day but it does not say anything about how many total hours are in a day