My coworker told me gravity isn’t a force it’s an effect mass has on space time, like falling into a hole or something. We’re not physicists, I don’t understand.
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The answer is gravity is an invisible force that pulls objects toward each other. Earth’s gravity is what keeps you on the ground and what makes things fall. An animation of gravity at work. Albert Einstein described gravity as a curve in space that wraps around an object—such as a star or a planet.
Gravity is not a force of attraction between masses so much as it is a force that bends the space around masses.
Mass warps spacetime, and that warping of spacetime is gravity. The common analogy is imaging a bowling ball sitting on a really taught bed sheet. Where the ball sits will create a funnel, and if you rolled a marble or some small spehere in a straight line you can see how it quickly goes into an orbit like pattern.
Of course we don’t live in a 2d world, and the 3d version is difficult to imagine.
As to whether it’s really a force or not, I’m not sure. I feel like it’s kind of semantics at this point. We call it the 4th force but it behaves differently from the others and we have a unified theory of the other 3, but not gravity.
I think it’s currently unknown, they are looking for gravitons… if they exist, then it’s a force.
The force between your feet and the ground is percectly real and it’s reasonable to describe gravity as a force.
You *can* describe gravity as “not a force” since its an emergent property of motion through a curved spacetime, but then you can argue the other fundamental forces are also “not forces” since these “forces” also arise as emergent properties of something else.
Lets talk a little history! It’ll help understand much better than just an answer
So this guy Isaac Newton in 1687 published a physics paper describing gravity basically perfectly, and gave equations for it and everything. Huge deal, He described it as a force which objects ‘attract’ one another over any distance and his equations could be used to describe what we see in the world extremely well. He got it right. Except that, its completely and totally wrong. His equation do work in describing the world from a math perspective, but only to a point and then they don’t work
So Einstein comes, and well, does a lot, but instead of Newton’s ‘gravity is attraction’ thing, he says, No, Newton, the previous god of science and math was wrong. There isn’t any such thing as an attractive force or gravity, Gravity instead is an outcome we see, not an attractive force itself. Instead, space itself is affected by things with mass. This mass, any mass, bends and curves space towards them, instead of being attracted to each other, space itself is bent and things can ‘fall’ towards each other, but there is no force. We had previously been interpreting these objects ‘falling’ towards each other as an attractive force of gravity– it is not, it is just us seeing space bending.
Einstein basically said, Newton’s stuff is good, like super good, but thats not at all how it actually works… its way weirder
And now we have Einstein’s theory… which many people in physics now–and for a long time–have also felt isn’t entirely correct either (basically its just missing something, otherwise its mostly correct), although for very different reasons than Newton’s not being right. Even Einstein wasn’t entirely convinced his was the final solution, though he wavered on that a bit. So people are looking at ways Einstein’s theory can be improved, kinda like he improved Newton.
This doesn’t mean that gravity isn’t a force though… it just depends on how you define force, in some definitions, gravity would not be force, in others, it may be.
If you attach a ball to a string and spin it around, you can feel forces acting on the ball because it is attempting to go in a straight line, and you’re consistently applying energy get around the conservation of momentum. You can do this in space, on Earth, or anywhere.
The mass will keep trying to go in a straight line, and if you let go of the rope, it will.
Consider then, why a satellite can orbit around the Earth in a circle forever (ELI5 version of forever), without needing to constantly correct it’s direction (as there’s no rope to constrain it), and no accelerometer would ever be able to tell that you were in fact going in a circle.
Mass, via gravity, has changed the shape of spacetime such that your satellite is in fact going in a straight line around the Earth, and there is subsequently no violation of the conservation of momentum. It’s not actually doing anything to the satellite, so much as to the spacetime that the satellite is passing through.
Let’s look at Newton’s first law
> A body remains at rest, or in motion at a constant speed in a straight line, unless acted upon by a force.
But we look up in the sky and see that the planets and the moon aren’t moving in straight lines and there aren’t any obvious forces acting on them. So Newton explained that with gravity as a force.
Have you ever seen the [flight path of plane on a map](https://imageio.forbes.com/specials-images/imageserve/5e546df1d378190007f43538/LONGEST-FLIGHT-IN-THE-WORLD/960×0.jpg?format=jpg&width=1440)? Why do they take such roundabout routes instead of just flying in a straight line? Well, they *are* flying in a straight line. But the surface of the Earth itself is curved, so any straight lines on the surface also become curved. Wait a minute…
So Einstein proposes that the planets and the Moon *are* moving in straight lines. And gravity is not a force. It’s just the stuff that they’re moving through, space and time, are curved, so their straight lines also end up curved. And that curvature of spacetime is called gravity.
Assume you are traveling through space. You pass by the earth and suddenly you feel like you are getting closer to it, even though you don’t feel like you are being pulled towards it at all.
This is because your body is still traveling in a straight line, at rest. What’s really happening is that the earth is so massive it makes a giant sinkhole in space, so your straight line has become a curve.
When you are standing on earth, the ground is actually pushing you away from it. This is the normal force. If you hold an uncalibrated accelerometer in your hand, it would show -9.8m/s because your hand is pushing it away from the straight line path that leads straight down.
gravity can be seen as not a force, all forces can be interpreted as geometry but gravity does not have a known a particle responsible for interaction.
What you think of as gravity is actually electromagnetism making you accelerate upwards due to repulsion. If you were not stopped by the ground you would not be able to differentiate between freefall and there being no gravity.
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