The gravity of things

originally posted by: andy06shake
a reply to: iamthevirus

I don't think Einstein's theory of general relativity predicted the existence of dark matter, it did however imply the existence of black holes.

So this is obviously the flat-earthers representation of how gravity works, I can even draw images of wormholes connecting from one place to another on a flat surface...


But as we all know this is ho it really looks... I wonder if someone can draw me a three dimensional wormhole and convey how it works using this image instead?


Quantum Physics has no solution for gravity so they call it dark matter maybe?

In a 2D representation the object with mass "pulls" another object towards it, that is why the expression is always used...

In the 3D representation spacetime "pushes" another object towards an object with greater mass, that's why I like to use the term (pushes)

/additionally, the composition of the interstellar medium differs from the intergalactic medium. the interstellar medium is comprised of mostly hydrogen gas... so does that mean there are two types of dark matter? the interstellar vs the intergalactic Dark Matter?

a reply to: iamthevirus

so does that mean there are two types of dark matter? the interstellar vs the intergalactic Dark Matter?

Given that over 80% of all matter in the universe is made up of material we have yet to see, im going to go with possibly.

a reply to: iamthevirus

I wonder if someone can draw me a three dimensional wormhole and convey how it works using this image instead?

Im in a park with the weans right now buddy, so probably not, and even if i was not out and about, im not sure i could be of much help there.

Quantum Physics has no solution for gravity so they call it dark matter maybe?

Apparently the difficulties of formulating a gravity theory where quantum physics is concerned is down to the fact quantum gravitational effects only appear at length scales near the Planck scale.

a reply to: andy06shake

Quantum gravity has a lot of holes man... frankly I'm kinda bored with all this "multi-verse" - "anything that can happen does happen" - "law of probability" type of stuff... it's like just an excuse to not have to provide any continuity in science heck and even in the entertainment industry.

All you have to do to make quantum anything work is to change the entire universe! well that's convenient lol.

We obviously do not experience reality the way the quantum physicists see it, so obviously it is not true...

Meanwhile GR just chugs right along confirming itself on a daily basis seemingly.

a reply to: iamthevirus

The problem is the scale and the micro/macro aspects that surround such.

From our perspective gravity pretty much rules much everything we can see in the Universe.

Down there amongst the quantum foam all the same things are apparently somewhat muable, same with time, or at least the arrow of such.

originally posted by: andy06shake
a reply to: iamthevirus

so does that mean there are two types of dark matter? the interstellar vs the intergalactic Dark Matter?

Given that over 80% of all matter in the universe is made up of material we have yet to see, im going to go with possibly.

So why don't we just go with the definition of dark matter being... the (Medium) and it is the dynamics of said medium (aka spacetime) which physicists like to call "dark matter"

How does that saying go about the simplest explanation tending to be the most accurate?

It is Quantum Mechanics which gives rise to the term Dark Matter when according to GR it's been there all along (known as spacetime)

One must "invent" a lot of stuff for QM which can in no way or even stands a hope of a chance at being displayed/presented/proven via experiment... it's all theory, none of it Law unlike in GR.

a reply to: iamthevirus

Well, black holes were just theory iamthevirus, and now we have pictures of them or thereabouts.

The holy grail would be a theory that would encompass both quantum and classical mechanics aka a "Theory of everything" far as im told.

Lovely... it always leads back to "nothing"

let's study the nothing because matter is comprised mostly of empty space, that's right you guessed it, matter is nothing!

guess what happens when one dies...? yep "nothing"

because everything came from "nothing"

gotta love QM

a reply to: iamthevirus

Cheer up mate you know what they say.

originally posted by: andy06shake

I tend to, that's why I'm with camp Einstein... besides a lot of these self-proclaimed Quantum Physicists have a tendency to commit suicide.

interesting documentary...

Dangerous Knowledge - the God Messenger

a reply to: iamthevirus

Medical doctors are apparently the worst profession where a tendency to commit suicide is concerned.

a reply to: Arbitrageur

Let me try again, and thanks for all the patience. I'm starting to think that maybe my vocabulary isn't adequate.

I would expect the inverse square of gravity to be constant from it's center outward, but apparently it is highest at the earths surface.
Is gravity something that is only emitted from the surface of matter or does it behave like a singular point?
If we calculate back with the gravity of other bodies, can we determine where the inverse square starts from, center or surface?

a reply to: iamthevirus

As I stated before, I also like GR better than QM, specially when dealing with gravity and the large-scale structure of the Universe. However, it is not QM that could solve the puzzle: it would be, if any, quantum gravity (something they should have really named quantum relativity, which already exists as a field.

But anyway, the problem with GR in what concerns dark matter (let's call it a deficit in the matter component of the field equation) is that we cannot account for it from GR without violating a sacred axiom of GR: there are no privileged reference frames.

We can explain dark matter without resorting to exotic particles or quantum effects, but at the cost of giving up the said sacred axiom. Something we are not ready to do.

originally posted by: Terpene
a reply to: Arbitrageur

Let me try again, and thanks for all the patience. I'm starting to think that maybe my vocabulary isn't adequate.

I would expect the inverse square of gravity to be constant from it's center outward, but apparently it is highest at the earths surface.

Vocabulary may be a problem, but it's not the only one. Someone else in the thread said that about gravity being highest at the Earth's surface, and I made a post on page 2 of this thread to specifically correct this apparent misconception, with a graph showing the maximum acceleration is predicted to occur at or near the "surface" of Earth's outer core. It seems like you didn't read my post, or ignored it, or if you read it, it didn't sink in the least little bit because it doesn't jive with your understanding at all.

www.abovetopsecret.com...

I didn't try to interpret the numbers on that graph on page 2 previously but I'll try now. We know the gravitational acceleration at the surface is just under 10 m/s², about 9.8 m/s². We can only measure it directly to a limited depth but we can model it and the model suggests it's about 10 m/s² from roughly 4100km radius to about 6000km radius (though the graph shows slight deviations from this value in this range). The maximum gravitational acceleration according to the graph appears to be about 10.6 m/s² at a radius of about 3400 km from earth's center, though you can probably find more accurate figures if you search for the source material.

Is gravity something that is only emitted from the surface of matter or does it behave like a singular point?

Again the model matters. In Newton's approximation gravity occurs between masses. In Einstein's model it's between masses and energy as I already explained in this thread, with a minutephysics video explaining this. So since individual atoms have mass and energy, gravity occurs even between atoms. But we don't usually talk about this much because the gravity is maybe a trillion trillion trillion times weaker than other forces, like the electromagnetic interaction, and is even weaker still from other forces, the strong and weak nuclear forces.

When we talk about gravity at Earth's surface, it's between every atom in your body being attracted to every atom in the Earth. If you go below Earth's surface toward the higher density inner core, the varying densities of the Earths' interior complicate things. It's still every atom in your body attracted to every atom in Earth, but inside the Earth you have different atoms pulling on you in different directions (or warping spacetime in different directions if you prefer), so how Earth's mass is distributed internally (which is not homogeneous) will affect the gravitational acceleration inside the Earth.

If we calculate back with the gravity of other bodies, can we determine where the inverse square starts from, center or surface?

That graph I posted showing the acceleration due to gravity inside the earth can be ignored for calculations outside the earth. From Earth's surface and up you can usually approximate Earth's gravity as inverse square from the center of Earth. But there are all kind of caveats if you want to be very, very precise. First, the Earth is not a sphere but an oblate spheroid which means the radius is larger at the equator than the poles due to "centrifugal force" from the Earth's rotation, and also gravity is not uniform all over the earth's surface even if you tried to model the ideal "oblate speroid". Some of these variations can have an effect even on low earth orbits at say 500 km above the Earth, which means you can't model Earth's gravity with perfect accuracy assuming it's from the center of the earth.

Perturbations in orbital elements of a low earth orbiting satellite

CHAMP is a satellite orbiting 500 km above the Earth at the moment. The perturbations are profound and measurable for the precise determination of the gravity field.

But by the time you get to the distance of the moon, none of those surface variabilities matter and you can probably treat Earth's gravity fairly accurately using Newton's model as emanating from Earth's center, even though it's really from the mass and energy of every atom comprising the Earth according to Einstein, but doing such a more complex calculation won't give you a much different answer than Newton's approximation at that lunar distance.

a reply to: Arbitrageur

I miss read, sorry. it has to do with the total of mass as the core makes up most of earth mass... I think, I was just a couple 1000km off in my understanding

If we calculate back with the gravity of other bodies, can we determine where the inverse square starts from, center or surface?

Yeah I certainly fail to express myself, for scientist to understand me

We certainly derived that inverse square trough measuring other bodies gravity, maybe the moon or sun? Or was this a purely theoretical assumption that we now try to proof(self-fulfilling prophecies?). It would probably be more telling, to do it with the sun, as we could mesure all-round the sun.
So if we take the figures and calculate back where does that inverse square of the sun starts? Center or surface?

originally posted by: Terpene
a reply to: Arbitrageur

I miss read, sorry. it has to do with the total of mass as the core makes up most of earth mass... I think, I was just a couple 1000km off in my understanding

The earth radius is 6378 km at the equator and if peak gravity occurs at about 3400 km from Earths' center, that's not close to the surface at all, it's just over half the distance to the surface.

We certainly derived that inverse square trough measuring other bodies gravity, maybe the moon or sun? Or was this a purely theoretical assumption that we now try to proof(self-fulfilling prophecies?). It would probably be more telling, to do it with the sun, as we could mesure all-round the sun.

We measure the gravitational constant in Newton's equation using an apparatus like this.
Gravitational Constant Measurement

Then we can observe the orbital parameters of any planet, and use those and the gravitational constant in Newton's gravity formula to calculate the sun's mass/gravity, and they all give about the same result so that's pretty good confirmation. If someone can come up with a better model to explain those observations, it would be welcome, in fact Einstein did that, but his model simplifies to Newton's model "in the limited case" as Einstein put it. There may be further refinements to Einstein's model, but they will need to still explain observations of planetary orbits as well as Newton's and Einstein's models do.

So if we take the figures and calculate back where does that inverse square of the sun starts? Center or surface?

Orbital calculations are typically made from the center, but if you wanted to know the gravitational acceleration profile inside the sun, it like the earth may have a non-inverse-square interior from the center to the surface due to variations in interior density. So calculations are typically made from the center, but the actual inverse square relationship is probably only reliable from the surface up, still using the center for the basis of calculations.

Actually the name Dark Matter being childish sounding doesn't really matter (no pun intended)

Originally Fritz Zwicky used the term missing matter, but later used dunkle materie (he was swiss-american)

The reason it is labelled as such because of the issues observables... or non observables i suppose, which is that it is matter that does appears not to produce, or interact with electromagnetic radiation, and is probably some form of matter since it produces gravitation.

Scientists do have complex terms for some things, but there is no need to go overboard for something so simple.

Similarly the neutrino... when it was proposed by wolfgang pauli, its name was chosen to be 'little neutral one' he himself didn't like his proposal, because it meant at the time fixing the issue with beta decays apparent non conservation of energy and momentum by inventing a particle you could not detect. it was an elegant solution, which turned out to be correct.

originally posted by: Direne
Thus, assuming there is a deficit in the visible mass that could explain the observations, we are left with only two possibilities: new particles, or a modification of GR that could account for that effect. I abhor modifying my beloved GR and would really prefer some new particle being responsible, but honestly I think introducing new particles would have a disastrous consequence for the rest of particle physics.

The Standard model of particle physics has a few places in which you could 'easily' insert a new particle, or lets say, that there are postulated candidates that would actually be quite welcomed.

Here are a few i can think of off the top of my head
1) Heavy right handed neutrino, responsible for mediation of neutrino oscillation. One mechanism by which neutrino oscillation can be made to work in the cheapest possible way is the addition of a right handed neutrino. It being right handed means it would basically be a non interacting, BUT still have an effect on the so called seesaw mechanism which i wont explain here. Basically the chirality of all neutrinos is left handed.
2) Similar to above, a high mass sterile neutrino. It is called sterile because it is even less weakly interacting than regular neutrinos in such a way that it drives only second order perturbations or affects on the standard model. Particle Physics experiments have been looking for hints of this for a while. The best hints thus far are the energy excess in fermi bubbles. There is a gamma line of unknown origin around the galactic centre. As dark matter, assuming it is particulate, would be present at a higher density it is one theory that this line is produced by self annihilation of this matter around accreting blackholes... or the SagA* for example.
3) Super Symmetry. The lowest mass component of most ss models predict a stable high mass particle,
While super symmetry is considered disfavoured by high energy physics experiments, its not totally forbidden and the parameter space of interest for detector has not yet been covered. The issue with it as it stands is that it would give us a VERY high mass WIMP candidate and a bit of difficult fine tuning to have the standard model ok as it is with the super symmetric particles existing above.
4) Axion like particle - basically a particle that mediates an interaction between photons and magnetic fields. If this was to exist, it wouldn't be an issue for the Standard model at all. its a boson... just like a regular force carrier.
5) Q-Balls - basically stable collection of bosons confined and stabilized as a result of being in a confined collection. Similar to an atomic nucleus... but of bosons rather than fermions


Adding particles and their consequences honestly has to do with the energy scale at which they are produced or present. Such as for example the higgs. We can create the higgs... but only at high energy, and it is a manifest excitation of the higgs field in a similar way to the photon being an excitation of the electromagnetic field. Particles interact with the higgs field to get mass, but not the higgs directly.