Is General Relativity Really Better Than Newton's Theory of Gravity?
By Johny Jagannath
In this post I will compare General Relativity [GR] with Newton's theory of Gravity to see whether General Relativity is really better than Newton's theory or not. I argue that GR is not only not better but it actually takes us several steps backwards, keeping additional fundamental concepts such as inertia, centrifugal forces, and mass, in mind.
Dissimilarity #1, Mass In General Relativity.
In classical mechanics, Mass is very easy to define. Not so in General Relativity. Here are some relevant quotes from Wikipedia that support my contention.
Generalizing this definition to general relativity, however, is problematic; in fact, it turns out to be impossible to find a general definition for a system's total mass (or energy).How, then, does one define a concept as a system's total mass – which is easily defined in classical mechanics?
The disadvantage of all the [GR] definitions [of mass] mentioned so far is that they are defined only at (null or spatial) infinity; since the 1970s, physicists and mathematicians have worked on the more ambitious endeavor of defining suitable quasi-local quantities, such as the mass of an isolated system defined using only quantities defined within a finite region of space containing that system.
Dissimilarity #2, Inertia In General Relativity.
Inertia is an effect in General Relativity that arises out ether/spacetime [just like gravity]. In other words, inertia in General Relativity is an action-at-a-distance concept [as opposed to something that is born out of a contact force in classical mechanics]. Here's a relevant Wikipedia article, titled:
Source of inertia; speculative theories.
Various efforts by notable physicists such as Ernst Mach (see Mach's principle), Albert Einstein, Dennis William Sciama, and Bernard Haisch have been put towards the study and theorizing of Inertia. "An object at rest tends to stay at rest. An object in motion tends to stay in motion."
As a result of this redefinition, Einstein also redefined the concept of "inertia" in terms of geodesic deviation instead, with some subtle but significant additional implications.
Dissimilarity #3, Centrifugal forces In General Relativity.
Since inertia is a product of ether/spacetime in General Relativity, the centrifugal forces that are created by rotations [owing to inertia] are also a product of ether/spacetime; which means centrifugal forces are also reduced to action-at-a-distance in General Relativity. That is, if a bucket of water rotates, the concave surface that water gives itself is because the water molecules interact with ether/spacetime in General Relativity. Of course this has absolutely no mechanical basis. There is no valid mechanism that can explain this, nor this has been provided by Einstein. The absence of a valid mechanism is action-at-a-distance, in my book.
What is a valid mechanism?
When I throw a ball to my left, the ball should move in that direction [to the left]. But if the ball goes to the right when I threw it to the left, then this is not valid mechanics [assuming no wind forces]. Of course the force applied in this case is via a physical contact. But the contact-force was meant for the ball to go the left, not to the right. Such a phenomenon where the ball does not obey the laws of mechanics is also action-at-a-distance. General Relativity has many assertions that are similar to the mentioned ball-scenario. Read about them here.
General Relativity, by assigning ether [spacetime] as the source of perfectly mechanical ideas such as: inertia, and centrifugal forces, has chosen the path of action-at-a-distance which takes us several steps backwards. It has also turned the concept of mass into an undefinable entity.
So, why should we embrace General Relativity when such basic mechanical concepts that we take for granted are being redefined for no valid reasons? To me this is absolutely unacceptable given that General Relativity is not adding anything new to the table except muddying the waters further. So, no. GR is not better than Newton's theory of Gravity.