Chapter 2: Common Misconceptions About Gravity
What General Relativity Taught Us About Gravity is Mind-Boggling, and Scientists Still Struggle to Explain It.
This is the introduction of the companion articles to my Unifying Theory of Dimensional Geometry and Interaction series on YouTube. The goal is to go more in-depth and technical on the topics I discussed in my videos. You can view the series in progress by viewing the playlist here: https://www.youtube.com/playlist?list=PLhloW30YwYviMcZ_o6qpaREx2ZQbDL2tr
This article focuses on expanding Chapter 2, which is 15:11–25:42 in my video.
Before I move on to discussing new(ish) theories of gravity, we need to take a moment and focus on what we already know about gravity. Specifically, this chapter covers the common misconceptions about gravity. Once we review and clarify these misconceptions, it will be much easier to understand and demonstrate why myself, and others through the last century, think of gravity as an effect of a fourth spacial dimension.
Keep in mind that what I am covering in this chapter is still “accepted science" and will have references for further study.
Misconception #1: “Gravity is a Force"
When we call gravity a “force” we are specifically referring to what science calls the “fundamental forces.” This is different than the generic term “force” which is used in physics whenever an object causes another object to change its path or motion. In the generic case, and object “exerts a force on another object.”
When we label something a “fundamental force" in nature, we are referring to any observable phenomenon that influences an object without an identifiable cause or physical interaction. In other words, “force" is a placeholder for “we have no idea what causes it, it just happens.”
With this understanding, I think it is clear that there shouldn’t really be any “forces" in nature, and that all “forces" are nothing more than a clear demand for further study and investigation. It is an absolutely scientific statement to say “I do not know,” and acknowledging such is the foundation of empirical discipline. However, to say “We know what it is, and it’s a force.” is akin to saying “I know why the sky is blue, because it is.” This is NOT a scientific perspective.
With that said, you may have already seen one of the many videos on YouTube or articles in science publications that say “Gravity is not a force.” This is because that, since the publication of Einstein’s Theory of General Relativity (GR), we have come understand that gravity itself is a phenomenon comprised of several other physical principles. So, while we may not understand everything around gravity, it no longer qualifies under the enigmatic title of a “force.”
The principles underlying the observed phenomenon of gravity are currently understood as “curving of space-time.” In GR, space-time curvature can be quantified as time-dilation and/or an increase in length, almost always “curved,” in the vector space between two points. These are the mathematical tools we use calculated the effects of GR.
To understand how these effects cause the phenomenon of gravity, here is an illustration:
Imagine a rowboat, where the person paddling on one side of the boat is much stronger than the person on the other side. If the stronger person paddles as fast as they can, they will move the boat more on their side than the weaker paddler can move the boat on their side. This unequal motion on each side of the boat will cause the boat to turn.
In the same way, the closer you get to a gravitational mass, the more time is dilated, and the more the “vector space" increases between two points. This means that the part of the object closest to a mass will “move slower" from the perspective of the part of the object farther away from the mass. These are the effects which “pull" masses toward each other.
The reality of GR is that space itself has changed around a body of mass, and it is space that is causing the masses to “attract" each other, not a “force" pulling them together.
Reference 1: https://en.wikipedia.org/wiki/Spacetime
Reference 2: https://en.wikipedia.org/wiki/Einstein_field_equations
Video Recommendation:
Relativity 107c: General Relativity Basics — Curvature, Riemann Tensor, Ricci Tensor, Ricci Scalar
Misconception #2: We “Fall" Towards the Earth
Following logically from what we just discussed regarding the curve of space-time, we can build on that to better understand the effects of gravity here on Earth. One of the most mind-bending realities that we now understand from GR is that, according to the math, we don’t “fall towards the Earth” but rather the Earth is accelerating up toward us.
As “spacetime” curves and stretches around a massive object, like the Earth, moving in a straight line from the perspective of space means that you are actually moving down towards the Earth, especially when we are close to the ground. This means that the “weight” we feel is actually the pressure from the Earth accelerating up towards us. When spacetime is curved, the only way to “stay still” is to be constantly accelerating. Kinda like treading water.
If that’s hard to accept, think about an elevator. If you take a scale onto an elevator with you, your weight will increase as the elevator accelerates upward pushing against your feet. Likewise, as the elevator accelerates downward, you will get lighter from the perspective of the scale.
This is known in relativity as an “inertial frame of reference.” In other words, when you jump off a building, you experience a few moments when you are a “free body in space” with no forces (generic) acting on you. The sensation of falling towards the Earth comes from the fact that space is curved towards the Earth, and you are traveling in a straight line through space. The reason hitting the ground hurts so much, is because that, relative to space, the Earth is accelerating towards you.
If you are struggling with this idea, I highly recommend the videos below as they go in-depth on these ideas and have lots of examples. Understanding an “inertial frame of reference” is core to understanding the foundation of all Relativity.
Veritasium — Why Gravity is NOT a Force
Dialect — Why General Relativity (and Newton’s Laws) tell us The Sky is Falling Up
Misconception #3: The Speed of Light is Always Constant
You heard that right. While Special Relativity is founded on the principle that the speed of light is always constant to all observers, General Relativity shows us a case where the speed of light is NOT the same for all observers. At first glance, that may sound contradictory, but it is actually complementary. It only appears to be conflict because Relativity is often over-simplified when taught, and few people are familiar with all the nuances of the theories.
The first poorly communicated idea is that the “speed of light” is the thing that is constant. It is actually the speed of “c.” We use “c” in the equations of Relativity to represent the maximum speed of causality. In other words, “c” represents the fastest anything can move or happen, and it doesn’t just apply to light. In fact, many scientists hold the view that “c” is what limits the speed of light itself, and that without this constant in our universe, light may, in fact, have an infinite speed (completely academic, of course).
But, light can appear to travel below the speed of “c” as it travels through different mediums. That is why in Special Relativity the speed of “c” is referred to as the “speed of light in a vacuum.” Meaning that we are using a measurement of light free from any obstruction or interference.
However, even “c” is not always a constant in General Relativity to all observers. Again, this goes back to the curving and stretching of spacetime. If the distance of spacetime between two points is “stretched out” by gravity, then the perceived speed of “c” to an observer outside that gravitational frame of reference will appear slower.
In my video series I show this with an example of two spaceships shining a light through a gravitational field:
If you are feeling skeptical, you should know that we have actually tested this out experimentally. The experiment is called the “Shapiro Time Delay” and it was accomplished by sending a radar signal to bounce off the surfaces of Venus and Mercury. Keep is mind that radar is the same kind of an EM wave as light, just at a different frequency.
https://en.wikipedia.org/wiki/Shapiro_time_delay
The reason the phenomenon doesn’t violate Special Relativity (SR) is because SR only applies to “flat space.” GR builds upon SR. However, how we interpret what is actually happening in GR is still a great point of debate among physicists.
By one interpretation, “c” is mutable and is the primary thing curving and stretching in spacetime. However, to those of us who feel gravity is better interpreted as a fourth spacial dimension, “c” is still constant and immutable, and the fourth spacial dimension is how we account for the “extra distance” between two points in space.
So, with the background of Relativity established here, along with these critical points about what is actually happening with gravity in our mathematics, the next chapter will introduce the idea of gravity as a fourth spacial dimension.
