I was watching a Vsauce video and learned that any two objects, like two baseballs, are attracted to each other because of their mass, and the bigger the mass, the more gravity an object has. What does mass have to do with gravity, and what causes gravity? Why does something just attract other things around it?
In: Physics
Serious answer: Because.
Science ulitimately describes and models. It’s a mistake to assume that the descriptions and models, however good, are what’s actually happening, or “explain” it – even though that’s the language we tend to use.
Newton said roughly what you did – that bodies attract each other according to how massive they are (and also how far apart they are). That was a good fit to reality, but not a perfect one (notably, using Newton’s rules alone didn’t quite work to explain Mercury’s orbit).
Einstein described things in terms of curved space and time. That gave a better fit, and if you want to explain things in those terms, that’s fine (other people in this thread will and have described things in those terms). But just because the description is better, that doesn’t mean it’s necessarily what’s actually happening – it’s just a good match. It’s also incompatible with another excellent description of the way things “are”, namely quantum theory. One or both will have to give at some point.
It’s perfectly possible that, tomorrow, someone will make an observation that indisputably flies in the face of Einstein’s explanation – or maybe find a different way of describing things that works even better, and isn’t at odds with quantum theory. And then, quite possibly, we’ll be describing and “explaining” it in some other way completely. Either way it will still ultimately be a shorthand for “The universe behaves, roughly, as if this were the case” rather than “This is what is actually happening”.
I watch a lot of science programs, so I’m an expert. My most basic understanding is that space is like a stretchy, invisible fabric with time woven within it. Material objects have mass and sit on the fabric. Depending how heavy or light the object is, affects how much it stretches the fabric, and how other objects fall in towards it.
On Earth, you only feel this falling in one direction: down. In space, far away from Earth, the falling effect is felt in all directions. You can fall towards heavy things like stars and planets every which way.
The concept gets harder, I think, when you start to realize time is also part of the fabric and is likewise getting stretched. But we are only talking about gravity.
Your question made me research and learn about it. It’s funny because I didn’t do it at school… I guess I just needed the right incentive 🙂
I read this [answer](https://www.quora.com/How-is-gravity-generated-by-mass) and found it pretty interesting. Even due other people explained it great here so far
Since mass is an undefined, unexplained property, and always has been since it was introduced, physicists cannot answer: How is gravity generated by mass? However, answers abound. The reason why this occurs is because mass was arbitrarily made an undefined property. When mass was made an undefined property, disunity was immediately introduced into physics equations. The continue existence of fundamental disunity makes it possible for successful but partial theories to coexist. This flexibility results because the unexplained property of mass can be molded to fit into someone’s theory.
Mass could have been and should have been made a defined property along with force. Empirical evidence gives us guidance on how this can be done. The equation f/m=a shows the way by which mass can be made a defined property. The equation m=f/a doesn’t accomplish this because f=ma defined force. Solving the equation for mass cannot define mass because it would be a circular definition. However, f/m=a does contain guidance on how both force and mass can be individually defined. One must go directly to empirical evidence for definitions of both force and mass. Empirical evidence is represented by the letter ‘a’.
With regard to this question, there is no answer and will be no answer until mass is defined. I defined mass and have put it to work reproducing the equations of physics; but, all current highly favored theories are built with the undefined status of mass in their foundation. So, there seems to be little official incentive to define mass. However, there is no way to re-introduce fundamental unity into physics equations other than to go back and define mass. That will immediately regain fundamental unity for mechanics. For Thermodynamics defining mass will not be enough. Temperature must also become a defined property.
Gravity isn’t really a force, that’s just an easy way to describe it. Gravity is actually the result of the bending of spacetime, which mass does. Imagine you place a bowling ball on a mattress. It’s going to make an indentation in the mattress while it sits there, right? Now imagine you put a smaller ball next the the bowling ball. What’s it going to do? It’s going to roll downhill into the indentation created by the bowling ball until it’s touching the bowling ball. Now that smaller ball makes an indentation as well, it’s just a lot smaller than the bowling ball because the bowling ball is a lot more massive.
The idea that objects with mass are attracted to each other is the old Newtonian model of gravity. However, Einstein developed a more accurate model with General Relativity and in General Relativity things work differently. (However, Newton’s Universal Gravitation is a very close approximation of General Relativity in most cases and it’s a lot simpler to work with so it’s still very useful).
The ELI5 of General Relativity is that all mass and energy causes space-time to curve, and objects will try and follow a straight line in that curved space-time. So a very massive object will curve space-time in towards itself and other objects that get nearby will follow that curve towards the object.
A common analogy that’s used is the rubber sheet analogy where a heavy object makes a dent in a rubber sheet which causes things going near the object to follow the curve made by the dent. However, keep in mind that space-time is 4-dimensional and one of those dimensions is time so it’s a lot more complicated than that.
Incidentally, this means that the common explanation for black holes being something that you can’t escape because the escape velocity is faster than light isn’t quite complete. What actually happens at the event horizon is that the curvature of space-time gets so extreme that things get really weird. Specifically, what happens is that the curvature of space-time gets so twisted that all straight lines that go towards the future point towards the singularity so no matter which way you face or how fast you go, you can only ever go towards the singularity.
Lol great question. Maybe we can get back to you in another 100 years when we have a better understanding.
Ball. sheet,-spacetime. Space is Bent by mass causing objects to fall into another point. Gravity. Fact.
don’t listen to the bullshit in this thread. it’s just the way it is and no one understands it. and don’t even think about asking about dark matter.
GOOD. FREAKING. QUESTION.
So the explanation given elsewhere here, which I won’t repeat because they’re pretty good, is that spacetime becomes curved in the presence of mass, and all things (apparently so far) curve spacetime the same direction, so when things get near each other, they follow the curvature caused by the distrotion, which pulls object closer to each other.
But what is the “spacetime” that is curving, and why do some particles cause a larger bending than others when not moving is still not particularly well established. The current theory is that some particles, notably bosons which are things like quarks that go on to make up protons and neutrons in matter, interact with a field known as the Higgs Field, like the particle you’ve no doubt heard of, and by interacting with this field they gain mass and curve spacetime. Other particles, like photons the particles that are responsible for light, don’t interact with the field and are thus don’t have mass, only energy.
But this is a huge rabbit hole of particle physics that ultimate remains not decidedly answered. There are several theories for how mass is generated and how they interact with gravity at many different scales, and much of it remains up for investigation. I would argue reconciling the connection between particle mass and gravity is the current holy grail of modern physics, in that even in a purely observational sense we can’t answer all of the relevant questions. This isn’t even bringing up things like dark matter, which is a big screw you question mark in the face of all of this.
I’m probably butchering this as I’m just a random guy that likes to watch space videos online.
But I actually think it’s too simplistic to say two things are attracted to one another. It appears as if gravity is the curvature of spacetime.
From our perspective that curvature makes objects act like they’re attracted to one another… But, that’s not exactly what’s happening.
A simplistic way to think about it would be like if you stretched a bedsheet out tight on 4 poles and threw some marbles on it. Then you jumped in the middle. All the marbles would roll towards you like they were attracted to you. But those marbles aren’t so much attracted to you, they’re more just following the curvature of the sheet.
Spacetime is basically the sheet but only 4-dimensional and it’s unintuitive to our senses to think about it as a thing.
Now WHY does mass appear to be curving spacetime? IDK. It just does. I don’t think anybody has really pinned that part down yet. A lot of people are working on it.
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