Im having a hard time understanding why we feel acceleration. If a rogue planet crossed our solar sistem close enough to pull us away from the sun, accelerating us until we are expeled into the cosmos, would we feel this acceleration from the surface of the earth?
In: Physics
This seems to be more of a biology question. We can sense acceleration due to “the vestibular system” in our inner ear. The same system is responsible for our sense of balance and stuff.
If the Earth (the literal ground under us) starts accelerating, then yes, we would feel like. Similarly to how we can feel it when a car speeds up.
If a planet got into the *miraculous* exact right trajectory to pull on the earth for extended period of time,
the acceleration would still be so slow that I doubt we’d be able to feel anything
You do not feel acceleration due to gravity, no, because it is exerting force on every part of you equally, so there is no internal force in your body that you could detect. This is why astronauts in orbit are “weightless.” In reality they are almost as heavy as they are on the ground, and are accelerating at 8.7 m/s^2 at all times. But as far as they can “feel” it is indistinguishable from there being no gravity at all.
If something exerts a gravitational pull on earth to the degree that we could “feel” an acceleration. We would likely not care as we would be busy worrying about the kilometer high tsunamis, earthquakes and volcanic eruptions happening at the same time.
But theoreticly, we should notice if we suddenly got lighter/heavier depending on which direction the entire earth accelerates towards.
Our orbit around the sun isn’t a perfect circle. There is a periapsis and apoapsis. These are the points where we are at the furthers and closest to our star. We are going at our slowest at the peak distance away from our star and our fastest when we are at our closest.
Think of it like throwing a rock into the air. As it reaches its peak height, it slows down and then accelerates back to the ground. Same things happen in an orbit except the fall misses the object it’s accelerating towards and flings back around it.
Essentially, we already experience shifts in the speed the earth goes around the sun, but tbf it is quite minimal. 30.29 km/s at its fastest and 29.29 km/s at its slowest. It takes about 6 months then to accelerate 1 km/s.
If it accelerated faster, like from says 30 km/s to 100 km/s in the space of let’s say, a second. Then yes. You would feel it. And you would find yourself either 70km from where you were in 1 second if invincible or instantly dead if vincible. Exactly like if you were standing atop a train. If it instantly accelerated to 100 km/h, that shit leaving you behind.
You typically do not feel acceleration from gravity, because every part of you experiences almost exactly the same force, at almost exactly the same time, and so does the ground and the walls, and so everything accelerates at almost the same rate.
For instance, we only arguably feel the acceleration from Earth’s gravity (you obviously can tell that it happens, but do you *feel* it? It’s more like we’d notice if it was missing, and we feel the force our muscles need to exert to stay standing on the ground to counteract gravity.)
And we can’t detect the fact that we are accelerating around* the Sun.
For larges gravitational fields, and/or large objects, you can feel ‘tidal forces’. For instance, if you were near a black hole, you might feel your body get ripped into pieces. Or if you were as large and fluid as the ocean, then you’d kinda feel how the moon causes you to bulge towards it, and how the change in that gravity causes the tides.
(*well, techncially we accelerate towards the Sun, due to how orbits work)
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So, I don’t think we’d notice only a planet passing by, at least not with our direct internal senses. (We might see it in the sky, or read the news about the tides changing, or various astronomers might point out obviously changed readings.)
The Earth is accelerating right now. Can you feel it?
The Earth is moving in a circle around the Sun. Circular motion requires constant acceleration. Thus, the whole planet and everything on it is accelerating towards the Sun.
That’s not because it’s very small (although it is), it’s because it affects everything around us pretty much equally.
When you’re in freefall, you don’t feel the acceleration due to gravity. The astronauts on the ISS don’t feel like they’re accelerating.
So why do you feel heavy when you’re standing on the surface? It’s not the gravity you’re feeling, it’s the force pushing up on you from the surface. This force acts upwards through your feet, and exerts a stronger force on the bottom of your body than on the top of your body, which compresses you slightly.
That’s what you feel. The compression. When you feel a force, what you feel is the internal effects caused by uneven forces. But when you’re free falling towards the Sun, every part of your body is affected equally, as are all the particles in the air around you and the atoms in the dirt below you, so you don’t feel anything, and you don’t notice anything that looks like acceleration.
So the answer would depend on how the force was applied. For example, if someone strapped a giant rocket booster to the Earth and shot it off into space, we’d feel that, for the same reason we feel weight when we’re on the ground. It’d be acting on your upwards through whatever part of your body is in contact with the ground.
Afaik you would feel the initial change in velocity, but that’s all you feel.. it maybe a tug, or maybe a lasting tug, or maybe nothing at all, small acceleration changes can be unnoticed even if measurable if its gradual enough.
It’s probably similar to the feeling of being in a lift. Where you are feel a tug of acceleration before it reaches a steady speed. If the elevator is like roller coaster where the acceleration changes depending on the turns, up and down, you probably feel the tug each time the acceleration changes. And if the roller coaster turns into a plane taking off or a bullet train, you’d feel the tug far longer.
So the answer would be dependent on how gradual is the acceleration?
All celestial bodies move in geodesics, or in other words pathways defined by objects with mass. When you move through a geodesic, you feel weightless.
Let’s assume instead of earth, you’re floating in space around the sun. You won’t feel any acceleration. Even if say another body of the mass of the sun came through, you still wouldn’t feel a thing because you’re simply moving through the geodesic, which simply changes on the introduction of the newly introduced body (with same mass as sun)
Let’s bring earth back and you’re standing over it. You’re being continuously accelerated upwards because you are stuck at the surface, unable to move through the geodesic leading up to the center of the earth. So the only influence you’d feel is that of the earth.
You’d not feel any acceleration external to the system of you and the earth, unless earth collides with something.
More info: https://youtu.be/XRr1kaXKBsU?si=oQ5aCzxtzm8S2XZQ
I would think, depending on the size of the change, we would feel it for a brief moment and then nothing. As mentioned by others, it’s more that everything at relatively the same speed. Imagine driving in a car. You don’t really feel the car moving forward after you stop accelerating, but you do notice any changes in direction or speed. But as long as the velocity goes back to zero, your ability to recognize the change vanishes.
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