Thanks to Marty who pointed out that Peter Dunns example is flawed. If we use the simple equation Ve=SQRT(2gr) with the constants g=274 m/s^2 and r=6.96x10^8 m we get the suns Ve=617.5 km/s. This is about 384 mi/s which is still well below 186,411 mi/s. My bad for not checking the math. (I can see OS shaking his head right now) First let me present a couple of interesting reads regarding gravity:

• Gravity as Falling Space
• The Cause of Gravity
• Can Gravity be Induced?
• The Speed of Gravity

I'm not saying I agree with the preceding articles, just that they present interesting views of gravity. Let me now ask another question. How do we truly know the mass of the earth or the sun? It has been calculated using Kepler's Third Law which is: P^2 = ((4pi^2)/(GM))a^3. Hmmm...seems we are relying on G again. My problem with all of this is that all these equations are based off of a set of localized observations. As stated here, " The key to proving Kepler’s Laws lay in Newton’s equation for gravitational force, which states that the gravitational force between two bodies is equal to the product of the gravitational constant G". The gravitational constant was originally proposed by Henery Cavendish in 1798 using a torsion bar expiriment. What is this constant G = 6.67 × 10^-11 N m^2 kg^-2? It's nice for describing behavior, but what generates it? The same question can be asked for vacuum permittivity (e0), what causes this value to be 8.854 X 10^-12? More food for thought.

I do quite a bit of reading on whatever my interest d'jour is. Recently it has been electromagnetism and gravity. While doing some reading on some of Poincare's theories and equations, I stumbled on this article which lead me to the field of Autodynamics. VERY INTERESTING!!! From the autodynamics web site:

Autodynamics is a theory of physics discovered by Argentinean physicist Ricardo Carezani in the 1940s after he found a mathematical error in Einstein's calculations for the theory of relativity. After correcting the math, a new set of equations appeared. According to the theory of Autodynamics, the fundamental underlying mechanism for the universe is the spontaneous change of energy to mass, and of mass to energy. Autodynamics is commonly abbreviated as AD. Autodynamics comes from conjoining the prefix "auto", as in "automatic", and "dynamic" meaning "changing".

For me the interesting part is the explanation of particle decay with decreasing charge. This eliminates the need for neutrinos! But supposedly neutrinos have been detected?!?! Since I have no way of detecting a neutrino in my garage, can I blindly assume neutrinos to exist? Food for thought.

As those of you who read my blog know, I have a lot of interests. I may have a mild form of adult ADD. ;) This leads me to a point that I've been kicking around in my head regarding gravity. What if mass does not create gravity but is simply affected by it? I have been studying the problem for a while now and have found quite a bit of work supporting this theory. One of the simpler supporting arguments was called out by Peter Dunn in July of 2003:

If gravity were simply generated by mass certain solar phenomena, ie the solar wind and coronal mass ejections, would not occur. This is why. The escape velocity required for an object (spacecraft - whatever) to break free of the Earth's gravitational embrace is 6.94 miles per second. Now the Sun's mass has been calculated at 333,400 times that of the Earth's so to calculate the corresponding escape velocity for the Sun we can simply multiply 6.94 by 333,400 which gives a speed of two million, three hundred and thirteen thousand, seven hundred and ninety six miles per second or, to put it another way, an impossible to achieve velocity that is a shade under twelve and a half times the speed of light. Material (in the form of the solar wind: calculated at 400mps, and coronal mass ejections: calculated at 600mps) is, however, streaming outward from the Sun all the time. Some might argue that this material does not really escape the Sun's gravity as it forms the heliosphere but, come on, a gravitational field of such intensity would not allow material to be thrown out beyond Mercury's orbit let alone Pluto's.

So what is gravity? In a traditional since it is the force of attraction between massive particles due to their mass. We can write things like F=G(m1m2)/r^2 to describe its behavior but that still does not adequately answer the question. Einstein takes us a bit further with his theory of general relativity where he states that gravity is a curvature of space-time due to the presence of mass or energy. Hmmm. It's obvious now right? String theory may be moving us closer to an answer, but there are still many questions, in many dimensions, to be answered using this model.

Right here in Milwaukee, UWM's Bruce Allen is conducting interesting gravity research with projects like LIGO (Laser Interferometer Gravitational Wave Observatory). The basis of LIGO is that it will detect space-time curvature ripples caused by large moving masses. LIGO (read Bruce Allen) has developed a free program Einstein@Home (like Seti@Home) to "help search our galaxy for undiscovered neutron stars." Maybe the results of the project will yield some more insight into the true nature of gravity...stay tuned.