Gravitational Waves Observed

[JIkj fjds j]

Things move because gravity applies an attractive force to objects, pure and simple. Whether this results in a stable orbit or a direct collision depends on what other motion has already been imparted to the objects.

Actually, things move through space because there is nothing stopping them.
Gravity is constant. It isn't like a seasonal thing. When summer days get longer and warmer gravity isn't getting weaker.

[Hashi Lebwohl]

Check the other thread where I mention that matter acts like an attractor; the greater the mass the larger the size of the basin of attraction. A large mass warps spacetime, inducing an acceleration vector which points towards the center of the mass; any other object entering that basin of attraction/gravity well will be influenced by the acceleration vector and move along the path of least resistance towards the other object.

All other things aside, gravity is still weird. It isn't carried by particles; rather, it seems to be a side-effect of coalesced matter itself, even though matter is nothing more than highly compressed spacetime. As noted in the other thread, it seems to be a "spillover" from an unreachable higher dimension where distance has no meaning, hence gravity's ability to have infinite reach.

[Fist and Faith]

I'm quoted you there here. Heh

The "center of gravity" for any given object is an attractor, with the size of the basin of attraction being based on the amount of mass present. Of course, this doesn't answer why mass is an attractor, only describing that it is one.

The fact that gravity has infinite reach means that the attractive force we know as gravity is somehow linked to one of those higher dimensions (we have 11 of them, remember?) where "distance" as we know it has no meaning. I once read someone's speculation that "gravity" is actually the "spillover" of that force from that dimension into the four we experience. *shrug*

There was a fringe science site I saw some years ago that talked about people's experiments into trying to induce acceleration vectors, which would directly lead to the ability to accelerate an object by manipulating local space-time. There were no conclusive results at the time, of course, but if such a thing were possible then interstellar travel becomes a possibility. It might still take 100 years to reach nearby systems but at least it would be possible.

All I know about this stuff is from Brian Greene. Particularly his Ted Talk on String Theory. Which paints a very different picture of the extra dimensions than whatever it is you're talking about. He says the others are "tiny, curled up dimensions, curled up so small, even though they're all around us, that we don't see them." They are "deeply tucked into the fabric of space itself". Ten dimensions of space, and one dimension of time. These tiny dimensions "have a very rich, intertwined geometry." They might form what's known as a Calabi-Yau shape. (The idea is that the Strings can vibrate a certain number of ways within the allowable geometry of these intertwined dimensions. And these certain ways explain the very specific numbers that science has determined are so delicately tuned to allow our universe's existence. Exact strength of the electromagnetic force; strong and weak nuclear forces; mass of the elementary particles; etc. But I digress. We're talking about gravity.)

So what do you mean by "higher dimensions?"


Wikipedia's entry on String theory says that, in Einstein's general theory of relativity, "the phenomenon of gravity is viewed as a consequence of the geometry of spacetime." I think this is the answer that I'm looking for. There isn't anything that "grabs and pulls", or is a lasso, or however we might think of it. Maybe without any matter, spacetime is a perfect lattice of x, y, and z axes, in straight lines. And maybe that perfect lattice does not cause movement. Maybe something sitting in warped spacetime must move. One bit of matter in that lattice would warp spacetime around it, but it would just sit where it is, because it is at the center of the warp-shape, the gravity well, it produces. (Of course, without another thing to measure it's position, we couldn't know if it was moving or not. But I hope you know what I mean anyway.) But a second mass would also warp spacetime. Now that our first mass is not sitting in a lattice warped only by (and to) itself, it moves. It must move, because it is simply a property of spacetime that, if it is warped, anything within that warp must move toward the point of the greatest warp - the center of the gravity well.

I have no idea if I'm explaining what I mean. And, most definitely, I have no idea if that's what general relativity is saying. But if, as you say in the post above (not the one I quoted), gravity is not carried by particles (They've given up on gravitons?), then maybe this is what they're saying?

[And if we figure out how to warp spacetime through other means, we'll be able to make artificial gravity.]

[Hashi Lebwohl]

Yes, when I say "higher dimension" I mean precisely those, the other dimensions which are accessible only at the quantum level, which is why we will never be able to detect them or be able to travel through them. I say "higher" because we exist in the "lowest" four--x, y, z, and time.

Distance as we know distance doesn't exist there, which is why gravity has infinite range even though there is nothing being emitted which "carries" the force of gravity; it merely is as a side-effect of the way in which this universe coalesced into existence.

Once we are able to figure out how to warp local spacetime so that it induces an acceleration vector then the stars will no longer be out of our reach. We would still need to convert ourselves into non-organic forms but that is another discussion entirely.

[Zarathustra]

Gravity is not merely modeled as a warp in space, it is actually a warp in spacetime. We can see this in the lens effect of galaxies bending light itself--which has no mass--and thus magnifying images of galaxies behind them much farther away.

We can also see this (now) in gravity waves. The ripples are distortions in spacetime, not merely models of distortions. They are real. They've been detected. That's the whole point of this thread!

Motion is relative. Things don't have to move. In the absence of another object, a singular object couldn't be said to be moving at all (well, perhaps if it were spinning ...). Motion is simply the time/space relationship between objects. There's nothing necessary about it, it's all contingent upon initial conditions, reference frame, and physical laws which explain/define how those initial conditions unfold within their reference frame. You might as well ask why there is space or time. Objects were already in motion from the moment of the Big Bang. Gravity is merely one facet of the shape of that motion, which to us looks like a force, because it can accelerate objects. But acceleration as defined in physics is merely a change in velocity, which is a vector (rather than scalar) quantity, which means that a change in direction (e.g. orbiting in an ellipse) is an acceleration. Orbiting objects are in freefall through curved space. The curve isn't a model, it's reality. Saying otherwise completely misses the point of this discovery, i.e. gravity waves, in addition to numerous others in the past century (e.g. light passing through curved space), and indeed the whole point of Einstein's general theory of relativity.

[Fist and Faith]

Still trying to make sure I understand this... Gravity is not a force that reaches out from one mass to another, and pulls. It's simply the shape of the landscape? If we made a machine the size and mass of my fist that could warp space-time as much as the Earth does, objects everywhere would react to it the same way they react to the Earth. Because it's not the mass that things react to, it's the warped space-time the mass causes that things react to. Things cannot NOT react to warped space-time. And they wouldn't care, or know, if the warping was the result of a mass, or a machine that warps space-time through other means.

Anything inaccurate in there?

[wayfriend]

It seems to me that saying gravity is caused by a "warp" begs the question ... how does a "warp" cause objects to move towards each other? And how does mass cause a "warp"?

You could imagine a warp as mass "sucking in" the space around it, and objects in nearby space would, by virtue of inertia, be pulled along. (Imagine some marbles on a satin tablecloth, and then a vacuum cleaner hose planted into the middle of the cloth - the cloth gets sucked up, and the marbles move closer to the hose as this occurs.)

But we've only moved the question, from how does mass attract mass, to how does mass attract space.

It's a useful model if it helps us find answers to things. But that doesn't mean it's not a model. Light waves, being accepted for a century now, are still just a model despite that.

[Fist and Faith]

You may be right. But if what I'm thinking is accurate, then at least we've moved the question from the wrong one (What are the mechanics of the force that reaches from one object to another, pulling them torward each other?) to the right ones (How does mass warp space-time? & Why do things move along the curves of warped space-time, instead of just sitting still?) .

[Zarathustra]

Reaching a level where our "why" isn't answered doesn't mean we've begged the question. We'll always be able to ask a new "why" every time we answer a previous question. Explanation is an infinite regress into deeper explanations. We're always at the Beginning of Infinity.

We could ask the same "why" questions of a force: why does mass exert a "pulling" force that we call gravity? Why is this force attractive rather than repulsive? Why are there forces in the first place? The presence of these additional questions don't invalidate the force model; Einstein's proven theory and observations do.

It's a damn good question to wonder why matter warps space. Einstein's theory doesn't explain that. Perhaps once quantum mechanics is united with GR we'll know. However, given that "empty" space isn't actually empty and there really isn't a zero energy state, space could be thought of as matter in a very low energy state. Perhaps matter and space/time are simply two forms of the same thing, one more condense than the other. Maybe matter is just a really tight ball of space. A tight warp in space. Maybe everything is an illusion of geometry; pure math. [I'm not sure how serious I am about that ...]

It seems that it would be pretty natural for there to be warps in space like this after such a chaotic event like the BB. Just like swirls in gas after an explosion. Not only are there local phenomena, but larger ripples as well. It might all be the same phenomenon.

[Hashi Lebwohl]

Perhaps matter and space/time are simply two forms of the same thing, one more condense than the other. Maybe matter is just a really tight ball of space. A tight warp in space.

This is already known to be true even though we still don't know *why* matter (condensed spacetime) has "gravity" as a side effect. I suppose we could imagine a "quantum field" that encompasses the entire universe as if it were one large flat sheet of stretchable fabric. When we tightly fold or condense one small part of it the rest of the entire sheet gets pulled in that direction; the greater the concentration the greater the pull. That still doesn't explain *why* but it gives us a starting point as to *how*.

Once we start to get some more answers as to what happens at that nebulous threshold between "quantum" and "macro" we might obtain some more insights as to how matter "creates" gravity.

[I'm Murrin]

I don't know if it's correct, but I always tend to picture spacetime and everything in the universe as being of a single substance, with matter and energy and so on being local fluctuations in that substance - what we see as distinct particles are just types of local fluctuation that exhibit particular behaviour relative to the whole. So everything is actually part of a single thing, it just varies in different parts, and each part is constantly connected to everything around it and influencing it. Matter, in this model, is a fluctuation in spacetime that warps the substance of the universe in such a way as to cause effects throughout the whole, pulling the substance of spacetime and everything in it towards that matter.

Matter is not therefore a bowling ball on a rubber sheet, distorting the medium it rests upon; it is the distortion in the sheet itself. The substance and the effect are one and the same thing.

[Zarathustra]

Matter is not therefore a bowling ball on a rubber sheet, distorting the medium it rests upon; it is the distortion in the sheet itself. The substance and the effect are one and the same thing.

Yep. The rubber sheet analogy is a good example of begging the question, since it requires the very thing it is trying to explain, namely, gravity pulling things down the warped rubber sheet. It might be better to say that matter *is* the warp in space rather than ask why matter causes the warp. If the former is true, the latter would be like asking why matter causes itself, and the question reduces to nonsense.

So since the universe has been expanding all this time, maybe we shouldn't think of the matter of Earth (for instance) being contained to this one spot we call earth, but extended on as far as its gravitational effect goes ... basically, infinity. Maybe the earth (or any object) is a shape, a process, an interaction rather than a thing.

[Fist and Faith]

All that isn't just pretty and poetic; it's true. E=MC^2 tells us it is to a certain degree. And if string theory is correct, it is to an absolute degree.

Still, that's not how we examine and understand reality. Chunks of universe-stuff don't always act the same as other chunks of universe-stuff. And we want to know why. So let's get to it!

[Vraith]

My biggest stumbling block, the source of frustration/comprehension even by analogy is this:

What is the "stuff" that spacetime is "made" of, that it can have a property like flatness or curvature AT ALL?
It is obvious, given what we know, that it can't be "stuff" at all in any ordinary sense.
A seldom mentioned conflict [probably because it is expressible---I think mathematically equivalent--- to other conflicts] between G.Relativity and Quantum is similar.
In GR, spacetime is smooth and continuous, in quantum it is discrete.
Still, it is "something" with "properties."

And, in an interesting twist---according to some [quite a few, actually], the waves, predicted by E. and evidence of GR, can be used [with some tech improvements] to examine the spectrum emissions of black holes and other really massive bodies [and perhaps truly giant stellar explosions, if caught in the act] to test whether gravitons, and gravity as a force, exist---though GR has no gravitons or force.
Kinda like the Hulk---the more you think you hurt him, the tougher he gets.

[Hashi Lebwohl]

That is where our approximation models break down--spacetime isn't made of other stuff; rather, spacetime is the stuff out of which everything else is made. It is the irreducible foundation of reality. When anyone speaks of it being "flat" or "curved" or "stretched" those are merely conveniences which allow us to have a mental picture approximating what is happening from our Newtonian point of view. The old analogy of putting a bowling ball and a tennis ball on a bed to cause the bowling ball to make the tennis ball fall towards it is inaccurate because stars and planets don't "sit" on some flat surface...but it helps visualize the situation.

I wonder if it would be possible to artificially create gravity waves?

[Vraith]

I wonder if it would be possible to artificially create gravity waves?

In one way, sure, it would be relatively easy [relatively in an absurdly relative way]. Just a problem of engineering improvement. Send out machines to start pushing stars together in a couple places, then, once you have a couple black holes, push them close to each other. [[you could, of course, gather up preexisting neutron stars or black holes---but that involves a lot more travel---and lots of galaxies depend on black holes for their very survival. Talk about fucking up the environment!]]

But I'm sure that's not what you're talking about. You want a generator to make electricity and use it, not some giant airship flying around trying to herd thunderstorms.
Maybe---but how it's done requires an answer first: is it a force, with a particle, the graviton? Or not?
We've got plenty of experience playing around with forces and particles...we have none at all manipulating the non-material fabric/geometry/"stuff" of spacetime itself.
We'd need an entirely new kind of tool.

[Hashi Lebwohl]

I doubt that gravity waves are carried by particles; I think they are disturbances in spacetime itself. Yes, I think it would be amazing for us to be able to artificially create them in a laboratory environment but I don't think we know enough about spacetime to be able to manipulate it yet, much less detect it as it exists.

[Zarathustra]

What is the "stuff" that spacetime is "made" of, that it can have a property like flatness or curvature AT ALL?
It is obvious, given what we know, that it can't be "stuff" at all in any ordinary sense.

What is "stuff?" Seriously. Matter is mostly empty space. Particles themselves aren't really "stuff." They are little "pockets" of energy interacting in specific ways. Everything is ultimately relations between relations. I don't think there's really a dividing line between matter-energy and space-time. It's all patterns of interaction. The universe is like "living math," and nothing more.

[Vraith]

What is the "stuff" that spacetime is "made" of, that it can have a property like flatness or curvature AT ALL?
It is obvious, given what we know, that it can't be "stuff" at all in any ordinary sense.

What is "stuff?" Seriously. Matter is mostly empty space. Particles themselves aren't really "stuff." They are little "pockets" of energy interacting in specific ways. Everything is ultimately relations between relations. I don't think there's really a dividing line between matter-energy and space-time. It's all patterns of interaction. The universe is like "living math," and nothing more.

Not sure I'd agree with "living math" analogy---but it seems to have some fun/interesting implications. Like it would imply---maybe necessitate---"unliving math." What could we make with that?

Think of all the things us living matter beings can make out of unliving matter....and that works pretty well with my belief that once we fully understand all, or even most of the "rules," we'll be able to change/create the rules...at least in local and very useful ways.

I agree that relations fundamental. If we postulate some "thing" exists yet has no relations/interactions at all---that "thing" would be completely unknowable.
But that wouldn't matter because it would ALSO be completely irrelevant to any and everything else.

There may well not be a clear dividing line.
But "what is "stuff" still matters and must be answered.
We know it has "properties." It can be flat, it can be curved, it can shrink and expand. All those things have effects, or its effects cause things---they are part and parcel of the relations/interactions.

If there is no hard line, nevertheless, the relations/things are contingent/emergent, each and every kind of "thing" a particular or special case/flavor/shape/something of the "stuff," its local "conditions."

Maybe there's even more than one kind of "stuff."...that gravity is such a problem because our theories can only accurately account for one kind of "stuff" at a time [so far]. Once we know what it is, we can do things with it.
We can already do astonishing things just by playing with the matter/energy conversion and equivalency.
Heh---isn't that what the Trek warp drive is? Using energy to alter the local fabric of space/time? There is a real [theoretical] version of that that supposedly might work. Tech/engineering insufficient right now, but the hardest problem is the amount of energy required to make it work.

What if the energy is only really a problem because enormous energy/mass is the only way we know to affect it so far? Seriously, we only got really cool things out of electricity once we started having some idea of what it really was...after a lot of time just watching what it did "naturally" with lightning and magnets, etc.

[Hashi Lebwohl]

A couple of fringe science sites claim that researchers have stumbled onto conditions under which they are able to alter localized gravity which is measurable via the results obtained on accelerometers. Other researchers suspect that this is the only viable way to cross interstellar distances--you cannot possibly carry enough fuel to make it even to the nearest star, much less traverse greater distances by using some sort of combustion engine but a trickle of power giving a ship an acceleration vector of even .001 m/s^2 means that it can cover the distance to Mars (we will approximate this at 85 Mkm) in only 5 months.