Interestingly enough, according to Chernin, et al. (https://arxiv.org/abs/0706.4068) the marbles will recede away from each other if they are beyond a certain distance apart. Per Chernin, gravity and antigravity balance each other out at what they refer to as the “zero gravity surface” and they...
Thanks for the info. It will take a while to fully digest...but the fact the distant objects are moving from us at v=Hr and ACCELERATING away from us as/if H(t) is constant is very interesting.
Hubble’s law tells us that the velocity of distant objects increases with distance as v = Hr. Does this mean that the farther a distant object gets the more rapidly that object will recede away from us? That is, are these distant objects accelerating away from us? Can we say
v = Hr, and so...
There are two types of acceleration: 1. “Relative” (also known as “Coordinate”) acceleration and 2. “Proper” acceleration. Relative acceleration may be the more familiar type and is simply the rate at which the velocity of the object changes over time and requires precise definition of the...
Inertial reference frames (IRFs) are defined as reference frames in which Newton’s Laws of Motion (NLM) are valid. Please cite a reference documenting that there is some other (just as precise) definition of a different type of IRF. Thank you.
Problems with Inertial Reference Frames, cont.
3. As to the third example:
“We can usually treat reference frames on the surface of the Earth as inertial frames. (Since the Coriolis effect is generally small enough to be ignored.)”
As conducting a LGT demonstrates, reference frames fixed...
Problems with Inertial Reference Frames, cont.
2. As to the second example: “An inertial frame of reference is a frame of reference that is not accelerating. “
(Again, assuming that IRFs exist, which they do not…) Reference frames in free fall are IRFs yet they can clearly be said to be...
Problems with Inertial Reference Frames, cont.
1. As to the first example: “All inertial frames are in a state of constant, rectilinear motion with respect to one another “
This is essentially claiming that IRFs do not accelerate relative to one another – which is wrong. Consider a...
The initial presentation of Newton’s Laws of Motion (NLM) to students often proceeds as follow: 1. The 3 laws are presented, 2. The caveat that the laws are only valid in Inertial Reference Frames (IRFs) is (sheepishly) mentioned, 3. An attempt is made to define an IRF, and 4. Some examples...
Thanks for the comment. I think I agree with you but am not sure. And in any case, the point my argument relies on is simply the claim that gravitational acceleration is not caused by a force – which everyone agrees with. Whether I describe what the cause of that acceleration is or not to the...
Thanks for the reply. We are in mutual agreement on much of this so please don’t take this as nit-picking but…Yes, terminology here is tricky because in fact the most standard definition of acceleration – and the one I am using - is the change in velocity as a function of time, regardless of...
It would be understandable if the next point to be explored was that Newton’s laws of motion are only valid in inertial reference frames – which is entirely correct. But the last comment in my original post alludes to the problems with definitions inertial and non-inertial reference frames and...
There is no confusion. Saying that gravitational acceleration is caused by the curvature of space-time is a commonly used short-hand and is immaterial. My point is – and which you appear to agree with – gravitational acceleration is not caused by a force, thus objects throughout the universe...
I’ve struggled with the concept of inertia as derived from Newton’s first law of motion for the following reason:
IF, as postulated by Einstein, gravitational acceleration is not caused by the application of a force to an object but is caused by the curvature of space-time…
AND IF...
I went out into flat empty space and set the rocket throttles such that the acceleration of the books on the rocket noses was measured to be g. The mass of the book is m, so the force accelerating the book is mg, regardless of the mass of the rockets. Is this what you disagree with? I’m sure...