I think I understand the nuts and bolts of How gravity works, but why? Why do objects with larger masses attract those with smaller masses? Is this a question that can be answered?
Oversimplification: because the larger mass bends space and the smaller objects falls into that bend.
yes, the smaller objects bend space, but their bend is big enough to suck in the larger objec’s bend…
picture a flat pliabe surface, like a very very large sheet …with a large ball resting on it, causing a depression in the surface…and a smaller marble rolls by, causing a smaller depression in said surface…and you will not be surprised when the smaller marble rolls into the depression caused by the large ball. And imagine how speed could overcome the depression caused by the larger ball…and imagine how just the right speed to cause the marble to orbit the larger ball…until friction took over and slowed it until in fell into the larger ball…except that the friction is magnified over the type of frictional slow down thay say the moon has…but it is the same concept.
Those are good points Philster, but perhaps I’m looking at a wider scale. I mean, in a hypothetical universe, couldn’t the reverse be true? Smaller objects attracting larger objects? Of course the laws of physics would change to accomodate the new relationship to mass. But my question is, is there anything more concrete to the current mass/gravity relationship other than the fact that we see that the relationship exists?
LL, there are ‘laws’, and as the universe works now, this is how Einstein chose to explain it.
In a hypothetical universe, you can create any laws you want, so the reverse can be true “there”, but not “here”…not with these laws which are products of the forces on the large and quantum scale.
So, in your hypothetical universe, the burden is on you to come up with the ‘how’…you need to tell us ‘how’ it would work in your hypothetical universe.
Such is the beauty of the laws of physics.
I may be misinterpreting this, but I think you have the wrong idea; large masses do NOT attract smaller masses. Gravity is a force that acts equally on BOTH masses; it exists between them, as it were. The smaller mass is more accelerated because it’s smaller: F=ma. If you’re trying to hypothesize a universe where this isn’t true, you’re not talking about changing gravity, you’re talking about changing Newtonian mechanics.
Physics explains how things work; nobody knows why.
Why does a large mass ‘bend space’? Why does picturing a pliable surface explain why gravity works? It doesn’t. It’s just a sufficient model - a good enough metaphor - for now.
Nonsense. I know why Gravity works. It owes alimony to Magentism, back from when they divorced.
One of the most fundamental laws of physics is Newton’s Third Law, the action/reaction one. What it means is that forces never act just one way: The Earth exerts a force on me, and I exert a force of exactly the same magnitude on the Earth.
Why doesn’t it seem that way? Well, Newton’s Second Law tells us what forces do: F = ma, which means that a force on an object causes an acceleration depending on the mass of the object. So, since I have much less mass than the Earth, my acceleration due to the gravity of the Earth is much greater than the Earth’s acceleration due to my gravity. Since we’re usually measuring accelerations rather than forces directly, the force of Earth on me is more obvious.
Isn’t there a Feynman article about magnetism, where he explains that he can only describe HOW it works, not WHY it works?
Along the same lines, why does spacetime have 4 dimensions? Why not fewer or greater, and what keeps it that way? Why is mass/energy conserved? What makes the laws of physics remain constant and continue existing? If our universe is just a quantum fluctuation, why does it continue having the laws it has? If there is a hyper-physics which describes the laws which cause the known laws, doesn’t there have to be a hyper^2 physics which describes those law-describing laws, and a hyper^3 physics, etc.?
It’s turtles all the way down!
Bob Pirsig was a scientist before his troubles. Maybe a physicist? Here’s a famous piece about the law of gravity being a ghost:
http://www.aoe.vt.edu/~ciochett/lit/part1.html
http://www.educ.drake.edu/romig/FYS046/zen.html
What I'm driving at,'' I say, is the notion that before the beginning of the earth, before the sun and the stars were formed, before the primal generation of anything, the law of gravity existed.’’
``Sure.’’
``Sitting there, having no mass of its own, no energy of its own, not in anyone’s mind because there wasn’t anyone, not in space because there was no space either, not anywhere…this law of gravity still existed?’’
Now John seems not so sure.
If that law of gravity existed,'' I say, I honestly don’t know what a thing has to do to be nonexistent. It seems to me that law of gravity has passed every test of nonexistence there is. You cannot think of a single attribute of nonexistence that that law of gravity didn’t have. Or a single scientific attribute of existence it did have. And yet it is still `common sense’ to believe that it existed.’’
John says, ``I guess I’d have to think about it.’’
``Well, I predict that if you think about it long enough you will find yourself going round and round and round and round until you finally reach only one possible, rational, intelligent conclusion. The law of gravity and gravity itself did not exist before Isaac Newton. No other conclusion makes sense.
And what that means,'' I say before he can interrupt, and what that means is that that law of gravity exists nowhere except in people’s heads! It’s a ghost! We are all of us very arrogant and conceited about running down other people’s ghosts but just as ignorant and barbaric and superstitious about our own.’’
``Why does everybody believe in the law of gravity then?’’
``Mass hypnosis. In a very orthodox form known as `education.’’’
``You mean the teacher is hypnotizing the kids into believing the law of gravity?’’
``Sure.’’
``That’s absurd.’’
``You’ve heard of the importance of eye contact in the classroom? Every educationist emphasizes it. No educationist explains it.’’
John shakes his head and pours me another drink. He puts his hand over his mouth and in a mock aside says to Sylvia, ``You know, most of the time he seems like such a normal guy.’’
I counter, ``That’s the first normal thing I’ve said in weeks. The rest of the time I’m feigning twentieth-
century lunacy just like you are. So as not to draw attention to myself.
But I'll repeat it for you,'' I say. We believe the disembodied words of Sir Isaac Newton were sitting in the middle of nowhere billions of years before he was born and that magically he discovered these words. They were always there, even when they applied to nothing. Gradually the world came into being and then they applied to it. In fact, those words themselves were what formed the world. That, John, is ridiculous.
``The problem, the contradiction the scientists are stuck with, is that of mind. Mind has no matter or energy but they can’t escape its predominance over everything they do. Logic exists in the mind. Numbers exist only in the mind. I don’t get upset when scientists say that ghosts exist in the mind. It’s that only that gets me. Science is only in your mind too, it’s just that that doesn’t make it bad. Or ghosts either.’’
They are just looking at me so I continue: ``Laws of nature are human inventions, like ghosts. Laws of logic, of mathematics are also human inventions, like ghosts. The whole blessed thing is a human invention, including the idea that it isn’t a human invention. The world has no existence whatsoever outside the human imagination. It’s all a ghost, and in antiquity was so recognized as a ghost, the whole blessed world we live in. It’s run by ghosts. We see what we see because these ghosts show it to us, ghosts of Moses and Christ and the Buddha, and Plato, and Descartes, and Rousseau and Jefferson and Lincoln, on and on and on. Isaac Newton is a very good ghost. One of the best. Your common sense is nothing more than the voices of thousands and thousands of these ghosts from the past. Ghosts and more ghosts. Ghosts trying to find their place among the living.’’
I subscribe to the school of thought that says gravity, like just all quantum scale phenomena, cannot be explained or understood by us exactly as they are. We exist in a macro world and simply do not have anything remotely comparable in our experience. We do not have the words or concepts to encapsulate them.
What we can do is say it’s ‘like’ something else. Gravity is ‘like’ indentations on a rubber sheet. It’s also ‘like’ stretched elastic between two objects. But it’s only ‘like’ these things in certain ways, take the analogy too far and inevitably it falls apart. They’re just models to help us comprehend them. It’s ‘like’ them, but it far more unlike them in other aspects.
Similarly light is ‘like’ a wave, but it’s also ‘like’ a particle. Some think there’s a big problem with this, as obviously it can’t be both. But really, it’s neither. They are both just models we use to help us grasp what light is. We apply either model when it suits our purposes. But what is really is is currently beyond our comprehension. Perhaps it always will be beyond us.
So, to address the OP, the answer is no. It cannot be answered.
Futile Gesture,
Do you think it could be answered though? I mean you suggest that perhaps it will always elude our grasp, but I guess my larger question is:
Are there some questions in life that can never be answered through science (as opposed to faith.)?
Liquid : Maybe here’s the way to think about it. What kind of answer could you get that wouldn’t make you ask another ‘why does THAT happen?’. Can you imagine any kind of final answer to a ‘Why’ question?
Suppose you did get an explanation for why gravity works (‘because mass bends space’). Now you’re going to want an explanation for why mass bends space (uh, ‘cosmotronic blooberphons’). OK fine, now you ask why cosmotronic blooberphons exist…
In other words, any time you ask ‘why?’ you may be able to get an answer at a better level of detail, but you can’t keep doing that forever. At some point, you have to accept the answer ‘Because that’s the way the universe works.’ As science advances, sometimes we can add a few more levels of detailed descriptions before we get to the ‘just because’ answer, but we have to get there eventually.
I fear you might be right Quercus. Could the fact that we will never be able to answer “why” be an argument for the existence of God? Not necessarily of a White Guy With A Beard, but of some sort of “creator” entity? I know that’s horribly off the OP, but since I wrote the original OP…
‘God’ might as well be all the factors that go into making things they way there are. Why gravity is like this, and why quantum mechanics is like that, and why electrons do this, and why…
…and all those things that must happen for everything to “be” (for us from our consciousness) might as well be “god”.
Heavy convo, from Gravity to God.
The ‘rubber sheet’ analogy perplexes me; I can see that massive objects on the sheet deform it more than little ones, but the fact that a passing object rolls into the depression relies on gravity; the analogy is recursive.
Even more OP:D
If this is the way you ppl want to lead the argument then first of all lets define ‘GOD’…
“There is no gravity. The whole world sucks.”
[sub]Sorry, couldn’t resist.[/sub]
**Liquid[\b]: Little masses aren’t attracted to big masses - all mass is attracted to all other mass. Its just that large masses deform spacetime a lot, whereas little masses don’t deform spacetime as much. The amount of deformation, or curvature if we’re getting technical, is related to the mass of the object. Also, gravity really isn’t a force, its more of a measure of spacetime curvature - this arises from the laws of special relativity, and “action at a distance” being disallowed.
So if you have 2 masses, with m1 larger than m2, (m1, m2 are the two masses), m1 deforms spacetime more than m2. Now, everything moves in straight lines in spacetime (note: not in space), and a large mass curves spacetime, such that a straight line in space time isn’t a straight line in space. So, as we’re three dimensional creatures moving through four dimensions, we only see the effect of the distortion in three dimensions; i.e. the two masses move about their mutual centre of mass, which in this case is approximately the position of m1. Hence you see m2 attracted to m1.
**Mangetout[\b]: It i*is[\is] recursive if you think about it that way. However, gravity isn’t a real force - its just the curvature of local spacetime. So, like I’ve said above, something moving in a straight line in spacetime, must move in a curve in space, since the presence of mass distorts spacetime.
Isn’t this just substituting “God” for “cosmotronic blooberphons” in Quercus’ post?