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digitall565 t1_jefshw6 wrote

The ground doesn't move beneath you when you jump because you're going the same speed as the planet. Everything on Earth is going at the same speed as its rotation and same speed it's traveling through space.

It's the same reason you can jump on a bus or an airplane and not move either. You're accelerating at the same speed. However, if you jump and the bus speeds up or slows down, you do fall somewhere different. But the Earth doesn't speed up or slow down, so you never feel it and you always fall in the same place.


Mammoth-Mud-9609 t1_jefqt00 wrote

It does move but the vast differences in the mass of the objects involved means that the mass of the Earth moves less than the width of an atom.


notmyting t1_jefqjjg wrote

Technically, it does. But by such a small amount, we can't even measure it with the most precise tools we have. This is because the earth is very heavy compared to us, so the jump has a much bigger effect on us than it does the earth.


Alternative_Bar_6441 OP t1_jefr3v0 wrote

So if i stay on the same spot afloat for 12 hours would i technically be in another far away place


Bonneville865 t1_jefrwt9 wrote

Not really, for the same reason that if you throw a baseball into the air inside a car, the baseball doesn’t land behind you, in the spot where it left your hand.

You, like the baseball, have forward momentum in the direction the earth is moving. You aren’t actually jumping straight up; you’re jumping forward at about 1,000 miles per hour. It just feels like straight up because everything else is also moving at the speed of the earth’s rotation.


Alternative_Bar_6441 OP t1_jefsdf1 wrote

So everything we have been taught about jumping is a lie,is it just forward momentum?


PM_ur_Rump t1_jeft0tg wrote

No. You are jumping up, but also moving sideways at a speed basically equal relative to the Earth's rotation.

You are already moving at that speed, as is everything around you, including the air (assuming no wind), so from your perspective, all the motion is up/down.


WarmMoistLeather t1_jeftszw wrote

What do you mean by "same spot"? Relative to what? The sun? The galactic center?

I'm going to assume you mean the standard "what would happen if I hovered in a helicopter for hours, would I be somewhere else?"

No. You are moving right now. When a helicopter (or you) hovers, it is matching the rotational speed of the ground below it. Let's say what you mean is that you take off at sunrise and for 12 hours you want to keep the sun at the same visual spot on the horizon. You would no longer be hovering because you would have to counter your current speed, meaning you would have to race West at something like 1000 miles an hour. You have to counter the rotational speed of the earth at your latitude and I believe if you do this at sunrise, you don't have to add the Earth's speed around the sun, you just have to maintain your elevation because the earth is moving toward you as it sounds beneath you.


notmyting t1_jefrjap wrote

That is also true yes, the earth is moving around the sun at an average speed of 29.78 km/s. And the sun is moving around the galactic centre at roughly 220 km/s. So you will move relatively far over 12 hours.


DestinTheLion t1_jeh0ohd wrote

If you are moving fowards and jumping, what would slow you down? Air resistance. But in the case of you jumping with the earth, the air is moving forwards with you overall. So you keep moving at the same speed as the earth.


throaway174881 t1_jefwp0j wrote

Its the same reason you don’t move when you jump while standing on a train or in a bus. when you are standing on a train, your moving the same speed over the earth as the train. If you jump you dont just magically slow down. Same thing goes for the earth spinning/moving


GetARoundToIt t1_jefxzac wrote

Let’s take an everyday example.

We are riding in a car, speeding down the highway at 70mph. If we toss something (a ball?) softly up in the air, does it land right back in our hand? Or does it go spat against the back windshield, because when it lost contact with our hand it is supposed to fly backward at 70mph relative to the car?

So how does it work?

When the car is driving. Everything in the car, you, me, the ball, the air inside the car, are all going forward at the same speed. When we toss the ball upwards, we give it an upward force , but we didn’t change its forward speed. So the ball still kept going in the forward direction at the same speed as before, which is at the same speed as your hand. That’s why it can fall right back into your hand, as if the car was still.


rkhbusa t1_jefzjd9 wrote

Relative to the earth you aren’t moving. The simplest way to explain it is using the car example, from inside a car cruising at highway speed you can drop a penny it will fall straight down to the floor of the vehicle as you perceive it relative to the car it didn’t move horizontally in space at all but when you look outside as you drop the penny it becomes evident that the penny has actually moved about 30 feet horizontally relative to the earth in the time from when it was released to when it hit the floor of the car. The earth is our car maintaining a constant velocity as it travels over its highway that is space, looking outside the windows of our car we can extrapolate that relative to the solar system and our universe we are moving very quickly but because we are all moving as one with our planet and there is no noticeable acceleration or deceleration, from our perspective relative to the earth we’re stationary.


QuantomField t1_jefx9fc wrote

The Earth does move when you jump, but you are traveling the same speed as the Earth's rotation all the time. It only looks like you're not moving from the perspective of standing on the earth.

If someone in space could watch you jump they would see you move with the Earth before, during, and after the jump.

Not only is the Earth spinning, but it is orbiting the Sun. The Solar system is traveling through space around the galaxy, and our galaxy is moving through space. We are always in motion.

Something else to consider is that we don't sense movement. We sense changes in movement. That's why sitting in a car and sitting on the couch feels the same.

Lastly motion and speed can only be calculated in relation to something else. As an example if you're in a car travel at 50 mph, that means you are traveling at 50mph in relation to your starting position. You are still traveling at roughly 500k mph through space in relation to the Milky way galaxy. You just don't feel it because it's a constant speed.


Any-Growth8158 t1_jegebvy wrote

It moves a very little. It moves so very little that it isn't measurable because even if you are unbelievably morbidly obese your mass is insignificant compared to that of the Earth.

Let's say you weigh a health 100kg. The Earth has 60,000,000,000,000,000,000,000 times your mass.

Obligatory XKCD reference.


defalt86 t1_jefqwtj wrote

Every force has an equal and opposite force, so when you jump, the same force does, in fact, apply to earth. But the Earth is so large that the force applied from the jump is nowhere near enough to move the earth any measurable amount.


defalt86 t1_jefrd3p wrote

Another fun answer is that motion is relative to your frame of reference. From the jumper's perspective, the Earth DOES move and its the jumper that remains still. Scientifically, both points of view are valid.


Alternative_Bar_6441 OP t1_jefrijx wrote

No she mean like the earth is spinning why when we jump we dont move even 1cm


freddwnz t1_jefymca wrote

Because we are moving at the same speed as the earth rotates. You don't just magically stop moving once you lift off from the floor, you are still spinning with the earth at the same speed, just like the air in the atmosphere.