Posts by Martin

Welcome Stas!

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We still cannot say with certainty, even with our modern instruments that have measured it with extraordinary precision, because the question of the sun’s “true” size is entangled with questions about the physical definition of the sun’s boundary that even twenty-first-century solar physics has not fully resolved. Epicurus did not know the number. Neither, in some sense, do we.

This is nonsense.
Every measurement of a continuous variable has an uncertainty but that does not make the measurement untrue.
Our senses indicate that the Sun has a well-defined size. At times when it is reasonably safe to observe the Sun, we can easily see it as a sphere (apparent circle when using no other information) that is sharp within the resolution which our eyes provide. That means there is a way to define what the size of the Sun means and how to measure it.
The radius of the Sun has been measured to be 696,342 km with an uncertainty of 65 km, at the time of the measurements.

Other than that, I found no obvious error in the text.
The text seems to be based more on Stenger than anyone else.

For questions 2 and 3: Once you have established the law of gravity and measured the gravitational constant with a laboratory scale setup, you can calculate the product M/r^3 (M = mass of the sun, r = radius of the circle for an approximately circular path around the sun) from the measured time it takes the planet for one round around its sun. If there is another planet, you can determine its product M/r'^3. By measuring its apparent diameter at different positions relative to the own planet, calculations for consistency should reveal M, r and r'. Then, you can calculate the diameter of the sun from the apparent size with r. With no other planet, no moon and no comets passing by, classical mechanics seems to be at a dead-end with M/r^3. With the capability to launch satellites, a satellite can be used instead of the moon for the needed additional measurements. Or a space probe can be sent to collect the needed additional measurements. If the path around the sun is not exactly circular and the axes of the elliptical path are sufficiently different and with knowledge of the neutron and after measurement of its half-life, the measured neutron flux density from the sun during one round around the sun can be used to determine values for the main axes of the ellipse which are consistent with the measured flux densities at the points closest and farthest from the sun on the elliptical path.

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infinite divisibility of matter is logically impossible

If Plato writes something like "finite divisibility of matter is logically impossible", we reject it because logic does not tell anything about reality, and logic is not in Epicurus' canon of truth.
The statement "infinite divisibility of matter is logically impossible" is to be rejected for the same reason. That infinite divisibility of matter is possible is demonstrated by the success of continuum theories, e.g. the classical theories of thermodynamics, electrodynamics and continuum mechanics. Experimentally determined coefficients make these theories work. Where continuum theories fail is at microscopic explanations and in microscopic systems. Atomism has much more explanatory power and can be used to calculate from small sets of fundamental constants the coefficients which are used in continuum theories.

Epicurus typical reasoning on basic physics applies the logic of indirect proof: It is inconceivable that [statement] is true. Therefore, the negation is true.
Meanwhile, the conceivability of some of what he thought was inconceivable has been established, so his indirect proof fails in these cases.
Atomism has won because of its far greater explanatory power for the phenomena, not because of logical impossibility of infinite divisibility of matter.

My approach regarding the innovations/updates in Epicurus' philosophy is to keep them mentally separate. Whereas I am fundamentally Epicurean (materialism, atomism, ethics, individualism, friendship), I am complementarily eclectic in aspects where Epicurus' philosophy has gaps and where some non-Epicurean philosophers and others have made progress beyond Epicurus' philosophy. I abandon obsolete details of Epicurus' physics and replace them with better alternatives. In this way, Epicurus' philosophy remains authentic and consistent as discussed on this forum, and it is up to each individual to decide which eclectic additions to make to one's personal philosophy.

There are analogies between modern physics and ancient philosophies. In comparison, the most and strongest analogies appear to be with Epicurean physics.

A new theory typically does not follow from the old theory it replaces. Nevertheless, the old theory typically has enabled the development of the new theory. Similarly, the development of modern physics was enabled by Epicurean physics.

In a Newtonian universe with absolute space and time and when there is a point in time where there is no motion of that atom in the chosen frame of reference, yes, this would be the case at all other points in time, the atom would never move and would have never moved in the past.
In an Einsteinian universe with only one atom, there would be no references to measure space and time. Therefore, statements like "the atom moves" or "the atom does not move" would have no meaning.

The case of two atoms in an infinite void:
In a Newtonian universe with absolute space and time and when there is a point in time where there is no motion of both atoms and there is a distance between them, both atoms would accelerate from that point in time toward each other, collide, move with decreasing speed back to their points of rest, simultaneously come to rest there and accelerate again toward each other, repeating that cycle all over again into eternity and would have done so in all eternity of the past. (This is the simplest example of an eternal, pulsating universe. Until the discovery of the accelerated expansion, eternal pulsation between big bang and maximum extension was a credible scenario for our universe.)
In an Einsteinian universe, the two atoms would behave similar to the two atoms in a Newtonian universe. The distance between resting points would provide a reference for measuring space in the direction along which the atoms move. The period for one pulsation would provide a reference for measuring time.

There is a caveat: The physics of a universe might depend on what is in it. So, the laws which we know for our universe of maybe 10^89 particles might not apply in a universe with considerably less particles.

Welcome Aeneadum!

Here is my comment to Patrikios' thought experiment:
Placing the object outside Earth’s gravity would not be enough because then it could be in the Sun's gravity. Placing it outside the Sun’s gravity would still not be enough because then it could be in the gravity of the Milky way.
We might find a point between two galaxies at which the gravitational forces of both galaxies cancel out each other and where the gravity of further away galaxies is too small to be significant for a reasonably long time of observation.
We can define a frame of reference there at which the object would stay at rest once placed there without initial speed in that frame of reference. (There is a logical circle in it because the definition of an inertial frame of reference is that an object without external force keeps moving with its initial speed, i.e. stays at its place if initially at rest.)
If we want to move that object, we need to apply a force to accelerate it. The proportionality constant between force and acceleration is the inertial mass. (I would not call that "potential for movement".)
If we place the object in a gravitational field, the gravitational mass of the object is the proportionality constant between the force on the object and the gravitational field strength.
Gravitational mass and inertial mass are conceptionally different. We have defined our system of measurement units such that both masses are measured in the same units.
In a system, in which the units are not the same, the two types of masses are proportional to each other but not identical, which makes the conceptional difference more obvious. This is an ongoing topic of research into the foreseeable future. Physicists keep designing new experiments to test the proportionality between gravitational mass and inertial mass with ever increasing measurement accuracy.

Here are my answers to Cassius' questions:

Gravity is one of four fundamental forces which can be considered as independent and their own entities in easy-to-understand models. There is a unified theory for the other three forces. Moreover, there are attempts toward a grand unified theory which would include gravity as well. I have no expertise in the unified theories. I am not aware of a generally accepted grand unified theory at this time.

In the easy-to-understand models, gravity appears to be uncaused. This might not by the case in more sophisticated models and is not the case in one type of monism.

Gravity is associated with "matter" in the adequate models I know.

I agree with the answer from Grok. There is one caveat which I mentioned in one of our Zoom calls. That mass (or energy) produces a gravitational field and curves spacetime is only one of three possibilities and assumes that mass and space exist independently (dualism) but affect each other. The other possibilities are that mass creates space (monism) and that space creates mass (monism). Each of the three possibilities is compatible with observations and the currently best models to explain the observations. Choosing one over the other three possibilities is rather belief akin to religion than knowledge at this time. In practice, publications typically imply dualism like in the quote from Grok.

Today's meaning of "weight" is indeed a poor fit. The modern term "inertial mass" seems to be accurate for βάρους in the context of Epicurean atoms moving with constant speed. There was no proper understanding of gravity in ancient times, but anyone could sense the effects of inertial mass.

Welcome M.Dango!

Welcome ReiWolfWoman!

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Here’s a good video I recommend everyone watch

No, it is a bad video which you should not waste your time to watch (unless you are into refuting nonsense statements on mathematics and reality.) Moreover, it is far out of the scope of our site.
Steve Patterson presents a string of truthful statements mixed in with nonsense. Among other falsities, he makes the claim that his mathematical nonsense proves something on our reality, like Plato. Mathematics is a useful tool to describe reality but not the other way round, that mathematics prescribes reality. That is already enough to refute the Kalam cosmological argument as well.
Where can I reimburse the 14 minutes which I wasted on that video?

Welcome Lamar!

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just like Lucretius and Diogenes of Oinoanda and many others let the size of the job stop them from what they accomplished

should be "just like Lucretius and Diogenes of Oinoanda and many others let the size of the job not stop them from what they accomplished".

Those are incorrect. Whereas Plato's school apparently degenerated into plain skepticism, Kant's version of idealism was not that skeptic. Within Kant's epistemology, certainty with respect to knowledge about phenomena is possible but the metaphysical claim that that knowledge is the truth about how things actually are is unfounded. Moreover, Kant's epistemology can be restated in a materialistic framework. Therefore, the classification of Kant as an idealist is not relevant in this discussion.
With trivial matters, the distinction between knowledge about phenomena and how things actually are does not matter: When I am hungry, I eat, then feel full.
The distinction matters when we want to get a deeper understanding or when knowledge expands.
Maybe this example can clarify this:
If we kick a stone resting on Earth into motion on a horizontal surface, its speed will gradually decline and eventually stop. A simple theory can be stated that the natural state of non-living heavy things on Earth is to be at rest, and after they have been forced into motion, they gradually relax into their natural state of rest. (Aristotle came up with something similar to that). At that stage, people might have thought that the simple theory is the truth about how things actually are. Until a few hundred years ago, there was no experimental setup which could refute that theory. Even today, we could still use that simple (but ontologically wrong) theory for accurate solutions of engineering problems in cases which stay within its limitations. Newton had no way to experimentally refute it when he came up with a more general theory of mechanics of which the first "axiom" contradicts that simple theory. His theory was quickly accepted because it could explain more phenomena and at a deeper level. At that stage, people might have thought that Newton's theory is the truth about how things actually are. However, they had no superior knowledge from which they could justify that thought. Later, we found out that Newton's theory fails when high speeds are involved, contradicts electrodynamics and needs to be replaced by Einstein's special theory of relativity to resolve these issues. We might think that now, Einstein's special theory of relativity is the truth about how things actually are. But again, there is no superior knowledge from where we could justify that thought.

It is exactly that sentence ("On one side stands a tradition stretching from Plato...") which is false because Kant rejected dogmatism and did not reject the senses. In Kant's view, we know about the world through the senses. His epistemology examines how we make sense out of the input of the senses. That sentence is false with respect to modern academic philosophy, too, and maybe even with respect to some Stoics.
A correct revision could be:
"On one side stands a tradition stretching from Plato through medieval theology into much of modern religion: the view that what is genuinely real must be eternal, unchanging, and accessible not through the senses but through some higher faculty — pure reason, divine revelation, or the intellectual intuition of necessary truths."

In this context: The article is excellent with respect to Plato and Epicurus. My own position is that Epicurus extreme affirmation on the real world made sense at his time as opposition to Plato's nonsense, but it is obsolete now, thanks to Kant and others. As this forum is focused on authentic Epicurean philosophy I refrain from elaborating on my heretic view here.

It should be made clear that the article is rather against Plato's idealism. Putting Kant in the same bucket as Plato is wrong because Kant removed the ideal forms and Plato's nonsense that reality is truthfully revealed only by the logic of philosophers like Plato. There are other issues with the text but just removing Kant from the text would already improve the credibility.

Welcome J.Tycherne!

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Would a Kantian take the position that it is not true that there are no supernatural gods, not true that there is no life after death, and not true that pleasure is the guide of life?

Kant himself does take these positions. However, later Kantians may differ. I am an Epicurean, not a Kantian. My reference to being "Kantian" is limited to him as being named as the original source of the distinction between a model and truth. He used different terminology and an idealistic framework. Others reformulated his epistemology within materialism. Other than that and his version of the golden rule, I do not know much about other aspects of his philosophy. I have read very little from Kant himself but more from those who refer to him.

I found two references for dummies on Kant's epistemology and one reference for professionals. Although the one frome Nature has been created with A.I. (which I usually would not want to read or share) I have to concede that it is convincing and easy to understand. The second reference is riddled with mistakes but seems to correctly present Kant's epistemology. The third one is mostly above my league:

Kantian Philosophy and Epistemology | Nature Research Intelligence

https://yohanesnuwara.medium.com/the-epistemology-of-immanuel-kant-5e5e7fbd1e48

Kant’s Ongoing Relevance for Philosophy of Science | Kantian Review | Cambridge Core

Kant’s Ongoing Relevance for Philosophy of Science - Volume 28 Issue 3

www.cambridge.org