Some scientists claim that space is nearly empty.  What if it is not?  I suggest that the Solar System is full of Dark Matter.  Something we cannot see fills the Solar System and impacts the speed of our space probes.  I invite other opinions.

There is something wrong with our calculations of mass and gravity. The position of some far-distant satellites is off from scientific calculations by something on the order of a million miles, I think. So this error is non-trivial. Likewise something odd has been observed with certain galaxies and clusters that are moving at a high velocity... according to our current physics they do not have enough mass to stay together at these velocities, yet they still do. Scientists have theorized the existence of dark matter, unseen but having gravity, as one explanation for this.

Another possibility is that massive objects exist in another dimension, making them invisible to us but their gravity still affects objects in this universe.

It is with strong doubts that massive solid objects existing in other dimensions would be inhabiting our solar system, with only their gravity to show their presence. The reason for this is that their gravity would be more localized around their vicinity, just as gravity is more pronounced around a planet.

Say the object was like an invisible planet, maybe the size of Jupiter. If such an object really existed, it would have created all sorts of havoc with the orbits of our visible planets. Any such invisible object, even if smaller, would have already have made it’s presence known, by altering something else’s trajectory.

The fact that all of the outer solar system probes are slowing down in a general fashion would seem to indicate that the solar system as a whole is more massive, and not due to a concentrated massive invisible object within it.

Here is a simple analogy:

Say we all lived at the center of our Earth. Gravity would seem very light to us because the mass of our planet would be around us in all directions. Similar to us living near the center of our solar system. Say we then built a device that started tunneling up through the planet to reach it’s surface, (We’re explorers) but as the probe got closer and closer to the surface, it’s weight started holding it back. Yes it gains weight as it gets further away from the center of the Earth. That would surprise us, unless we could understand that the whole earth generates a gravity of it’s own, but we don’t feel it until we leave it’s center.

Well it appears that our solar system has a gravity of it’s own, that we don’t feel until we begin to leave it. Perhaps it is dark matter.

Perhaps. But what you said, about gravity at the center of the earth being low because the mass of the earth is wrapped around it, could just as well apply to the concept that larger objects are "wrapped" into another dimension, curved, as it were in a way that we cannot perceive directly. In that case, if the gravity of these unseen objects affects us in the 3-dimensional universe, it could attract matter or cause matter to collect in its vicinity. As one researcher put it, what we see is the debris or pollution.

Another analogy is that visible matter is like the foam created on ocean waves, as they curl in upon themselves.

I am not in a position to argue or advocate any of these theories, only that I know they exist and are being investigated by people who understand the mathematics behind them.

Dusty_Matter:

... Yes it gains weight as it gets further away from the center of the Earth.

A problem with analogies is they're often imprecisely described.

The probe doesn't "gain weight" as it moves away from the center of the Earth. What's happening is that while it was at the center, it was equally affected by the matter that lay around it in all directionless. Probe passengers would feel weightless and motionless at the center, because they're acted upon equally in all directions.The passengers aren't "weightless" -- they have "equal weight in all directions".

However, once the probe is some distance from the center, more of the Earth's mass lies in one particular direction ("behind them", relative to the direction they moved), so they'd feel an acceleration in that direction (more mass behind them).

At the Earth's surface, we experience "down" as the acceleration due to gravity, and weight as the force of our feet against the surface of the Earth (or a scale).

The gravity between two objects is directly proportional to their mass (the more mass, the larger the acceleration) and inversely proportional to the distance between them (the greater the distance, the less the "force"). But in your analogy, one body moves inside the other and is thus attracted in every direction simultaneously (to differing degrees, due to the different directions between the probe and the various centers of masses, except at the Earth's center of mass).

 

Very true Jeff, your description is much more accurate. I was only attempting a very simple, and brief explanation. The only point I was trying to explain is how localized the gravity becomes with the size of the objects in question, and small localized objects affect things in different ways than just what we are seeing with the space probes. Tele, debating about how higher dimensions might alter gravity however is pointless. It is what it is. (to us)

Dusty_Matter:

Tele, debating about how higher dimensions might alter gravity however is pointless. It is what it is. (to us)

If by debate you mean argument, I agree. I have no vested interest in defending a position. Especially since, most of us have no clue when it comes to really comprehending these ideas, other than imagery or what we might have heard about, or read somewhere. As physicist James Gates puts it, when we talk about advanced cosmological theories we are only describing them as when we hear a nice piece of music. We appreciate the sounds, but most of us cannot comprehend the underlying score.

 

Dear Telenoob, I read Dusty's reply to your letter, and agree with his description. I am putting up an alternative explanation to the "dark matter" theory. My idea (shared by others, but not many as yet) is that that peculiar material, antimatter, has negative gravitational mass. This means it still has the same inertial mass, so pushing a car made of antimatter would require the same force, but in the Earth's gravitational field an antiparticle would fall up. A positron and an electron would repel each other gravitationally. Unfortunately gravity is a tiny force, and the electrical, magnetic and nuclear (weak) forces would overwhelm this repulsion, making it very difficult to "see". The effects of this change in gravitational forces would be more evident, however. when you deal with large massive objects like stars, galaxies and cosmological events. Its just a theory, but I like it because you can see it and, if its wrong, disprove it by (extremely difficult) experiments. I am new tothis forum and am a New Zealander. We are a small nation, and like all small people, probably more aggressive than people from bigger countries... I may at times forget I'm not dealing with a bunch of Kiwis and get too pushy. Please say if this happens.

 I thought (Dusty) your first explanation was excellent. If you think of matter as bits, like 1kg blocks of cheese, then on the Earth's surface 1kg is pulled down with a force of 1 newton. This is the whole Earth pulling on it with the force of gravity. As you go down into a mineshaft (say) some of the Earth is above you and pulls your block of cheese up. So some of the downward force is cancelled and your cheese seems "lighter". By the time you get far enough down so half the Earth's mass is further from the centre than you are your 1kg block will only "weigh" 0.5 kg! And when you get to the centre, it will have no weight; ie: it will weigh 0 N. Note it still has a mass of 1 kg; "mass" here being inertial mass, what used to be defined as the amount of material (cheese) in the block. If my theory of antiparticles having negative gravitational mass is true, returning to the space probes changing velocity, the probes could be affected by a cloud of antimatter which may have passed between them and the Sun. Its repulsion force would cause them to accelerate. If they had passed through a ring (say), they should have slowed down as they approached the ring and then accelerated once past it. Of gourse if the material was composed of antimatter that could interact with the craft's material, the matter and antimatter particles would annihilate each other. This has not apparently happened.

Do we even have useful data on this phenomenon with the Voyager probes, since acceleration changes due to thruster use far exceed that due to purported dark matter?  That's what Aviation Week & Space Technology reported a few years ago anyway.  I suppose this problem would be solved after thruster propellant runs out (if it hasn't already), and a few years have gone by thereafter to acquire fresh data.

Dark-Matter nor Dark-Energy are responsible for the slowing down of the space probe Pioneer and Voyager. As both probe moved further from gravitanional influence within our Galaxy and closer to leaving it; it confronts oppositional forces from outside of our Galaxy. Both probe will need to fire enough thruster, if they still have enough to give it an escape vilocity that will permitted it to go out of this Galaxy. If both of these probe were not encounturing any resistance they will both speed up instead of slowing down but since there is a resistance they are force to slow down. In my line of thoughts I find a similarity just like our space ships that need so much speed in order to leave our atmosphere and entered into space. Its simple don't complicate and attached other phenomenon to it. 

Correction to my previous post.  It wasn't Aviation Week, rather The Planetary Report from May/June 2007 that covered this topic on the Pioneer probes (not Voyager due to attitude control thrusters).  "One of the possible causes of the anomaly is asymmetric thermal radiation from the spacecraft resulting from the placement of the heat sources such as the Radioisotope Thermal Generator power sources and from objects such as the communication dish."  In March 2008 The Planetary Report said that the anomaly could be partially (but not completely) explained by differential thermal heating and re-radiation of that heat.