Is Gravity Just a Byproduct of Time?

[czimborbryan]

I read somewhere that time and gravity are interrelated which may reflect Gravity as a byproduct of time. In other words, the force we perceive as gravity could be the movement created by the differential of two points of time in space. And sorry for not citing the source - I can't remember.

 

[A.T.]

I read somewhere that time and gravity are interrelated which may reflect Gravity as a byproduct of time. In other words, the force we perceive as gravity could be the movement created by the differential of two points of time in space. And sorry for not citing the source - I can't remember.

Newton modeled gravity as an interaction force. Einstein as a coordinate effect:

 

[jbriggs444]

I read somewhere that time and gravity are interrelated which may reflect Gravity as a byproduct of time.

In general relativity, gravity is not a force. It is instead, seen as a manifestation of how four dimensional space-time is curved. Objects in free fall are viewed as falling on straight lines known as "geodesics" in a curved space-time. Objects subject to forces other than gravity deviate from these geodesic paths.

In order to appreciate a curved space-time you should learn at least some non-Euclidean geometry. If you are after an intuitive understanding rather than a formal mathematical understanding of non-Euclidean geometry then you could do worse than the classic "Sphereland" by Edwin A. Abbot. However, that book will just give you a taste. Things get way deeper. Calling gravity a "byproduct of time" is an oversimplification of monstrous proportions.

 

[pervect]

I read somewhere that time and gravity are interrelated which may reflect Gravity as a byproduct of time.

Welcome to PF.

Time and gravity are related, the most obvious manifestation of this in my opinion is gravitational time dilation. Only gravity directly causes time dilation - other forces do not cause time dilation, except insofar as they may additionally cause gravity, which in turn causes the time dilation. Note that the time dilation is not directly related to the "force" of gravity, time dilation is approximately (in the weak field) proportional to the gravitational potential energy, which is the product of force * distance.

In other words, the force we perceive as gravity could be the movement created by the differential of two points of time in space. And sorry for not citing the source - I can't remember.

I am not sure what this means, so I can't really comment sensibly on it. Gravity can be regarded as curved space-time, though. One can find a reference to this in Wiki, see for instance http://en.wikipedia.org/w/index.php?title=General_relativity&oldid=661864735. General relativity is basically a geometric theory, as the Wiki article mentions.

General relativity generalizes special relativity and Newton's law of universal gravitation, providing a unified description of gravity as a geometric property of space and time, or spacetime. In particular, the curvature of spacetime is directly related to the energy and momentum of whatever matter and radiation are present.

One can also regard gravity as a necessary consequence of gravitational time dilation, given some other assumptions (such as what's commonly called the principle of maximal aging). This seems enough similar to what you might have meant, that it's worth mentioning, but it's hard to be sure whether or not it's what you had in mind.

While general relativity is most commonly regarded as a geometric theory, sometimes people do regard gravity as a force, so it's not necessarily totally wrong to regard it as a force. The principle of equivalence suggests, though, that gravity and inertia are closely related. This implies the "force" of gravity is more like the fictitious force one finds in an accelerating elevator or car, i.e. "Einstein's elevator" - it's a "force" that's really just a manifestation of matter's inertial. Newtonian theory regards gravity differently - it regards it as a real force, but Newtonian theory is unable to explain why the gravitational mass should have exactly the same value as the inertial mass. The equality of gravitational and inertial mass (one form of the principle of equivalence) suggests that gravity is more closely related to a fictitious force than a real force.

 

[czimborbryan]

Pervect,

Yes, gravitational time dilation. Wouldn't this dilation cause movement? In other words, the difference between two dilated times would cause movement from low to high energy toward the center of mass. If true, wouldn't this be the essence of gravity? Any charts around showing the ratio of gravity and dilated time? Curious about the extent of dilated time in deep space devoid of large masses.

 

[czimborbryan]

I hope my oversimplification does not offend anyone as I am not as well equipped with technical knowledge as the rest of you.

 

[czimborbryan]

Also, from what I understand. - if time dilation did not exist, movement through space would be impossible. Is this correct?

 

[PeterDonis]

if time dilation did not exist, movement through space would be impossible.

You have this backwards. Time dilation is not logically prior to motion. Time dilation is a side effect of motion (among other things). Time dilation is not a fundamental concept; it's a derived concept.

 

[czimborbryan]

Yes I inderstand that time dilation is not prior to motion. It coincides with motion. But without time dilation, objects in space could not move - correct? In other words, time dilation allows for movement. However, in terms of there being increased time dilation from the center of a mass, that would in effect create movement - ie gravity (right?). I'm visuslizing this, but I'm not quite sure how to explain what I'm seeing. And like you said, it is likely I am making an error in how I'm understanding this. I'm inquiring if time dilation is actually the "force" we call gravity because an object caught in different dilated times would have to move to resolve the difference.

 

[A.T.]

Yes I inderstand that time dilation is not prior to motion. It coincides with motion. But without time dilation, objects in space could not move - correct? In other words, time dilation allows for movement. However, in terms of there being increased time dilation from the center of a mass, that would in effect create movement - ie gravity (right?). I'm visuslizing this, but I'm not quite sure how to explain what I'm seeing.

You are confusing two different types of time dialtion:
- Kinetic time dilation due to relative movement.
- Gravitational time dilation between different positions, at different potentials in a gravitational field.

Gravitational "attraction" is related to the gradient (change) of gravitational time dilation. Free falling objects always tend towards areas of slower time passage (lower potential). This is simplified in the top picture here:

http://www.physics.ucla.edu/demoweb..._and_general_relativity/curved_spacetime.html

I'm inquiring if time dilation is actually the "force" we call gravity because an object caught in different dilated times would have to move to resolve the difference.

It's more like a rolling axle with two wheels, that will deviate towards the side with greater rolling resistance. The slower wheel represents slower advance in time on one side.

 

[PeterDonis]

It coincides with motion.

Not always. See A.T.'s post.

without time dilation, objects in space could not move - correct?

No. Once again, you have the causality backwards. Objects follow different worldlines in spacetime, and this causes differences in the elapsed proper time between selected events, which we call "time dilation". It makes no sense to ask whether objects could or could not move "without time dilation", because the concept of "time dilation" only makes sense once you have the concept of objects following different worldlines, and comparing their elapsed proper times.

 

[czimborbryan]

But I thought the concept of curved space time was just a model for better calculations. In other words, curved space time is a metaphor for what's actually occurring, not a direct representation. So this would make world lines a part of that model which does not explain the "essence" of gravity, but it explains the mathamatical formulations of gravity. So if we're asking "What is Gravity?", we must find where the force originates. I'm questioning if gravity (the force as described using space time calculations) is actually a "force" originating with time itself and not derived from particles or energies within mass. So what I'm visualizing is the real gravitational time dilation as the smoking gun for revealing the essence of gravity by way of an object having to resolve the time dilation it experiences within its boundaries. In other words, time is warped therefore an object must move along its path yielding what is observed as gravity.

Ok, I'm done and I completely accept that the way I'm seeing this is probably skewed, but had to get it out. And thanks for humoring my thoughts.

 

[A.T.]

But I thought the concept of curved space time was just a model for better calculations.

All of physics is. Physics is about quantitative predictions, not about some "essence".

 

[PeterDonis]

I thought the concept of curved space time was just a model for better calculations

That doesn't make sense in view of this statement further down in your post:

In other words, time is warped

If time is warped, then space must be warped as well, because time and space are interrelated; you can't separate the two. So spacetime must be warped. So it looks like you believe that curved spacetime is not just "a model for better calculations" but "the way things really are"; otherwise your statement about time being warped makes no sense.

In other words, if you agree that time is warped and you think that's what causes gravity, then you are basically agreeing with the GR model of gravity as being due to spacetime curvature.

 

[czimborbryan]

I know I'm contradicting myself because I lack the necessary vocabulary. So here's an article explaining that despite knowing the mathematical formulations of gravity, we really don't know what it is: http://www.universetoday.com/75705/where-does-gravity-come-from/ I think it explains what I'm trying to say from when I say essence of gravity. So I'm saying rather than gravity being a wave or a particle, it may be an artifact of time. - now after reading a few more things may be staying the obvious especially in terms of curvature of time, but does time dilation occur at the quantum level and can this account for the strange behavior of gravity? In other words time being on a giant sliding scale from quantum to galactic. And the difference between time being the unifying theory?

You guys keep sucking me in and I have a feeling I have done no better at explaining myself. - Or I have and I'm just not making any sense.

 

[PeterDonis]

despite knowing the mathematical formulations of gravity, we really don't know what it is

Sure we do. It's spacetime curvature. But whenever you get an answer like this in any science, you can always ask another question. In this case, that next question is: how is spacetime curvature "built" out of whatever quantum theory of gravity underlies it?

(Bear in mind that the article you linked to is a pop science article, not a scientific paper or textbook. It's never a good idea to try to actually understand science from pop science articles. Even when they're written by scientists, they end up doing more harm than good to your understanding.)

I'm saying rather than gravity being a wave or a particle, it may be an artifact of time

What does "an artifact of time" mean? Based on what you've described, I think it's just another way of saying "spacetime curvature".

does time dilation occur at the quantum level and can this account for the strange behavior of gravity?

At the quantum gravity level, there isn't any such thing as "spacetime"; that's the whole point. The challenge of quantum gravity is to build spacetime out of something that isn't spacetime--some underlying quantum theory that has spacetime as an emergent property. At that underlying level, there won't be any "time dilation" because there won't be any spacetime to begin with.

 

[pervect]

A few comments: I'd say it's an overstatement to say that physics does or can us "what" gravity is. But good physics will tell us how gravity acts. If two different models of gravity give the same predictions, physics doesn't have any definite way of choosing which model to use. It typically doesn't make any direct difference, but it may make a difference when it comes time to expand the theory to cover more and broader situations. It's generally impossible to tell in advance which form of a theory will be the most amenable to expansion, however.

I believe "Exploring Black Holes" would be the best source for explaining how gravity comes out of the principle of maximal aging. I don't have a copy of the book, unfortunately, to give any quotes, but there are a few tidbits on Taylor's website, http://www.eftaylor.com/leastaction.html. This is the closest I can think of to what I would guess the OP may be asking, though I suspect it's not a really great match. It's close enough to be interesting to him, perhaps, but I'm not sure if there is a good elementary treatment of it out there.

There are some other interesting models of gravity that don't initially involve geometry at all, such as Straumann's "Reflections on gravity". Interestingly, geometry comes out in the end. I suspect the paper is too advanced for the OP, however. I'll give the link anyway - http://arxiv.org/abs/astro-ph/0006423.

My personal view is that trying to reduce gravity to "just a force" winds winds up a lot like the fabled Procrustes, who would make people fit an iron bed by stretching their bodies in a rack, or cutting their legs down to size, rather than adjusting the size of the bed.

 

[czimborbryan]

Ok cool. I feel like I'm getting somewhere - which just happens to be back to space time. Without having a formal undetstanding if this, you helped me realize that this is pretty much what I was thinking all along.

So gravity really isn't a force, it's s

 

[nitsuj]

I'm still re-reading it, but is interesting. "Conceptual Foundations of Quantum Field Theory". The differences between classical and quantum field theory seems to be too much to say there is spacetime, and gravity changes it's geometry.

Of course within the theory of General Relativity the "answer" is gravity is a geometric effect on spacetime.

That link is the first result in a google search of "why is there a presumption of spacetime" lol

Also this http://philsci-archive.pitt.edu/9055/, it's titled Substantivalist and Relationalist Approaches to Spacetime

 

[Neandethal00]

I read somewhere that time and gravity are interrelated which may reflect Gravity as a byproduct of time. In other words, the force we perceive as gravity could be the movement created by the differential of two points of time in space. And sorry for not citing the source - I can't remember.

I can not prove my comment theoretically or experimentally. So, do not ask. But I observed some strange similarities between gravity and certain phenomena in nature.
From those observations I'm leaning towards this conclusion: Origin of gravity may not be physical.
Einstein's GR may be a hint. But it is not exactly what's happening in nature.
My 2 cents.

 

[BiGyElLoWhAt]

Let me ask the OP a question that might get them thinking:

What is a force?
I'm not asking you to give me the interaction definition, but WHAT is it? Why is it?

 

[PeterDonis]

Origin of gravity may not be physical.

What does this mean? "Phenomena in nature" are physical. So is spacetime. So is whatever quantum "stuff" underlies spacetime.

 

[czimborbryan]

So here's another thought I thought I knew. I thought the geometric models of space time were simply mathematical cheats for calculating gravity and not actual geometry based on what space time is. Yes? No?

 

[Nugatory]

So here's another thought I thought I knew. I thought the geometric models of space time were simply mathematical cheats for calculating gravity and not actual geometry based on what space time is. Yes? No?

No.

OK, that deserves a longer answer...
Geometry makes statements about the relationships between things (parallel lines do or do not intersect, the interior angles of triangles do or do not add up to 180 degrees, ...). Those geometries that are consistent with the Einstein field equations (which require that the geometry be connected to the distribution of mass and energy in a particular way) predict gravitational effects better than anything else that we've found so far. The geometrical interpretation is incomplete in that there are conditions under which is does not apply (very strong gravitational effects concentrated in very small regions, as when the mass of a star is concentrated into a flyspeck) but that doesn't make the geometrical models a "mathematical cheat" any more than it is a mathematical cheat to say that the Earth is round instead of flat.

 

[czimborbryan]

Ok then. Here's another (and very likely strange) thought.

I was under the assumption that time dilation could occur from an energetic event. For example, compounding waves could reach an energy capable of forming particles because time "stuck". - similar with black holes. The energetic event creating the black hole was so powerful, time dilation froze the event. Yep, over the deep end on this one.

 

[jtbell]

I thought the geometric models of space time were simply mathematical cheats for calculating gravity and not actual geometry based on what space time is. Yes? No?

How would we tell the difference?

 

[Neandethal00]

What does this mean? "Phenomena in nature" are physical. So is spacetime. So is whatever quantum "stuff" underlies spacetime.

Can I just leave it there? More discussion on my comment will bring in a huge elephant into the room and I do not have enough weapons to defend the animal. I'll clearly lose the argument in a minute.

It came from my simple observation that everything in the universe, matters, particles, living things, have a survival instinct. This can not be formulated in any type of mathematics or well defined laws at this time.
So, I surrender. My comment was simply offered as food for thought.

 

[PeterDonis]

It came from my simple observation that everything in the universe, matters, particles, living things, have a survival instinct.

You do realize that elementary particles can be created or destroyed in various interactions described by quantum field theory, right?

 

[Nugatory]

I was under the assumption that time dilation could occur from an energetic event.

Time dilation happens any time that two observers cannot find a single unequivocal and universe-wide standard for "at the same time" - and as Einstein's relativity of simultaneity thought experiment with the train demonstrates, all that's necessary for such a standard to be impossible is that the observers be moving relative to one another.

The easiest way to see that time dilation emerges from relativity of simultaneity is to consider that the statement "A's time is not dilated relative to B's time" is equivalent to "if, at the same time that A's clock reads noon B's clock reads X, then at the same time that A's clock reads 1:00 PM B's clock will read X plus one hour". The appearance of the phrase "at the same time" tells us to be watching out for relativity of simultaneity. (Note also that relativity of simultaneity explains how A's clock can be slow relative to B's clock yet B's clock can also be slow relative to A's clock).

Gravitational curvature is just another thing that interferes with our ability to find a single universe-wide standard for "at the same-time" and hence leads to time dilation.

 

[Hellmut1956]

I do enjoy reading threads like this one. Even more in another physics forum a gentleman seems to spend his time just contributing to this forum. When he commented on a concrete questions his physics knowledge became evidently smoke! Why am I writing this?

Physics and when it deals with concept alien to our day-2-day experience like quantum and relativistic theories, when it deals with cosmology, it wakes in us aficionados an avalanche of thinking and reflection! But I like to get back to basics with 2 statements that I believe explain what I mean!

1. As expressed here in this thread a couple of times, the physics science does not claim to say what is real! Physics works with models whose quality is given by how well they predicts what we perceive in experiments and observation through measurement.

2. The only language that gets us to speak the "same language" in physics are "mathematics"! If we do not speak this language we are like an analphabet who wants to grasp the wealth of Shakespeare by just being able to grasp the images of a printing with pictures! Mathematics are the language that allows us to express us about alien concepts with the smallest amount of ambiguity!

So as a kid in school first has to learn to read and write so that our civilization becomes accessible to him, same is true with Physics. Learn the mathematics and then start to "read" what is available about a topic in physics. The good think of this day is that you do no have to become a mathematician expert in applying mathematics, but proficient enough to be able to "read" mathematical notation understanding the principles of the applied mathematical tools. A tool like Mathematica from Wolfram Software can help you to "apply mathematics", but you have to have a certain knowledge about the mathematics involved! Both to read mathematical "text" and grasp what is said, as to "apply mathematics" using a tool like mathematica and its solvers!

To learn this mathematical concepts a very valuable tool are the courses available for free from the MIT in Boston via its "OpenCourseware" offering.

I am applying this to myself, even as I do enjoy the course videos about Cosmology and Inflation available at OCW, even while enjoying the reading of books like "The first three minutes from Steven Weinberg ot the one from Martin Reese, Just Six Numbers! As fascinating such readings are, it is just like watching picture in a comics books. You grasp what is being presented, but you are unable to "judge" the quality of the concepts presented nor are you able to understand and judge by yourself what is justifying opposing models and theories!

The result are tons and tons of reflection from readers that try to interpret the "pictures" they have seen and express what they guess they have understood using the highly ambiguous "normal language", like english in this case! After reading this kind of thread contributions I get bored and the feel of loosing my time. The writers should invest their own time to learn, so that then they might be qualified to discuss the topics and use the valuable time of others, or they are already having in mind to be exchanging ambiguous contributions with people equally qualified, in this case reading such a thread is waste of time!

Why do I waste my time? I am of the generation that believes in "evangelism" as a mean to "educate" the market!

 

[Nugatory]

This thread has wandered far from its origins... Time to close it.