This interesting paper deserves to be known more widely: “And Yet It Moves: The Observability of the Rotation of the Earth” by Peter Kosso, Northern Arizona University, published in Foundations of Science, (2010) 15:213–225. Excerpts: Abstract A central point of controversy in the time of the Copernican Revolution was the motion, or not, of the […]
This follows a post on synchrony conventions here. The question is, What is the meaning of here and now for what is observed? Is everything than an observer observes part of their here and now? Some things observed may be a long distance away. Some things observed may be from signals sent in the past,
Since the development of relativity theory, space and time have been combined in a four-dimensional continuum. Because the speed of light is an absolute value in relativity theory, it acts as a conversion factor between space and time. Accordingly, the four dimensions may be understood as any combination of space and time: 4 + 0:
The value of an independent variable may be selected first, and so is arbitrary, even subjective. One may select anything or everything within its range. A graph normally covers a whole range of the independent variable. Given an independent time interval, different travel rates result in different travel distances or, the other way around, different
Clocks can easily be placed on moving bodies or observers to measure travel time continuously. A moving body can have on-board devices to measure cumulative travel distance. Observers have more difficulty measuring the cumulative travel distance of an external body but it can be done by motion tracking devices. If the distance is long, multiple
As I’ve noted several times, the physics of the observer takes duration as the dependent variable and measures the corresponding length or other variable. This fits well with the finding that gravity is an approximately constant acceleration, g, which equals 9.81 m/s². What is gravity in the context of an independently chosen distance and dependent
This post builds on the post Physics for travelers. Passengers are travelers or riders with a specific destination. In a way passengers are passive; they just sit as a vehicle takes them where they want to go. But that comes after they entered the vehicle, which comes after they accepted a ride or bought a
People have purpose and goals but natural science excludes final causes. People plan and design but natural science excludes formal causes. In that case call the science of formal and final (be)causes “hypernatural science”. These higher causes are not against nature (unlike supernatural) but are not inherent to nature (and so hypernatural). A physics for
Following the previous post on uniform motion, this post covers non-uniform motion in space and time. A simple way to get non-uniform motion is to join two uniform motions in different directions; the change in direction means the joint motion is non-uniform. Another way to get non-uniform motion is to accelerate at a constant rate.
Uniform linear motion is the motion of a body at a constant linear rate. Uniform circular motion is the motion of a body at a constant angular rate. In both of these cases the spatial extent of motion and the temporal extent of motion are in a constant proportion. Because of this constant proportion, from
