MigL

You 'see' by that vast amount of radiation emitted by the fun, and somewhat filtered by our atmosphere, being partially absorbed and re-emitted, partially reflected and partially passing right through a structure which is almost 100% empty space. A miniscule fraction ( 0.4 to 0.7 um ) of the reflected light causes a chemical reaction in the receptors of your retina, which generates an electrical signal that our brain has learned to decipher as the structure in question. That is the only 'reality'; a description of effects. And don't get me started on how you actually touch and feel 'nothing'.

I had to chuckle when I read this. Do you understand the process of 'seeing' Davy_Jones ? Do you understand the process of 'touching, hearing, smelling or even tasting ? Tell us how you think they indicate 'reality'. I am reminded of Morpheus to Neo, during the Kung Fu training simulation in the Matrix "Do you think that's air you're breathing ?" Physics has learned to live beyond the 5 senses. There is 'something' 93 million miles away that emits the whole spectrum of Electromagnetic radiation, from gamma/X rays ( less than 10-12 m )to very long radio ( more than 105 m ), and you see but a small fraction of that radiation ( 0.4 to 0.7 um ) and are certain as to what it is, and how 'real' it is. We ( Physicists ) describe it, and its effects, using math. And that is about as real as it gets.

Don't go away Airbrush. The Big Bang theory is based on certain observations, like galactic recession increasing linearly with increasing distance and the CMBR. It is also predicated by GR, and the assumption that the universe is homogeneous and isotropic. So yes, you are right, it is an assumption.; and at large enough distances, a fairly accurate assumption, for the observable universe. Similarly GR does not allow for preferred frames, and a center of expansion certanly implies a preferred frame ( never mind the fact that the expansion with a center would look totally different unless we are the center; and what that implies for Religion ). So, unless drastic changes were made to GR, it would cease to be a viable theory. You are then left with the problem of having to explain the observational evidence for isotropic universal expansion, and the homogenous/isotropic CMBR. These are actual physical observations, and cannot be assumed away; they require an explanation. How would you do that ? B

I don't know, JC. It seems to have worked with D Trump supporters; none of them post here anymore.

Is it just me or does anyone else picture Dimreepr endlessly watching Monty Python, getting stoned, and occasionally posting hard-to-understand one liners when the mood strikes ? We love you, Dim 😄 !

In answer I can only offer a modified quote from a previous post ...

In developing countries, large numbers of male children are actually an economic advantage as they provide help in supporting the family ( never mind school ), while females are a detriment, as there is an associated cost ( dowry ) to marry them off. The economic model definitely needs to change.

Thanks for the recommendation; I will look into it. As for our discussion, I don't think he is trying to describe reality. I would say the mathematical model, which is common to all interpretations, describes elements ( but not completely, and only where applicable ) of any posible, underlying reality. The interpretation ( Copenhagen, many worlds, etc. ) are an attempt to convey the ideas of that probabilistic, mathematical model in common, everyday terms ( if superposition of states and multiple universes can be described as common oe everyday ).

Yes,I count seven ... These first three are the same question, and that has been answeed. Yes, positive curvature means parallel lines eventually meet, and, by travelling far enough, you can return to your starting point, as on the surface of the Earth. No, I did not. Given an infinite space, you can most certainly travel in a straight line to infinity if given an infinite amount of time. You can only return to your starting point in a positively curved space. I don't know, and I can't really ask him anymore. I would need to know what evidence he is basing his conclusions on.

Ahh ... Brings back memories.

Copenhagen is one of many INTERPRETATIONS of the probabilistic mathematics. Neither N Bohr or A Einstein had a problem with the actual mathematical model. There is also H Everett's 'many worlds' interpretation , using the same mathematical model; are you familiar with that ? Are we to infer that there are an infinite number of realities which grow in number with every interaction capable of multiple outcomes ? ( in Copenhagen Erwin's cat is both dead and alive until an interaction opens the box; in Many Worlds, Erwin's cat is alive in one possible universe, and dead in another universe when the interaction opens the box ) Einstein and Bohr also argued ( they were actually close friends ) about action at a distance, superposition and entanglement, and the Heisenberg Uncertainty Principle. Their most famous exchange had Einstein declaring "God does not play dice with the universe" To which Bohr replied "Yes he does, and sometimes he throws them where they cannot be seen" Sometimes Philosophers pretend they can see the dice ...

Whether there is a reality or not, or even if it can be described adequately is a philosophical question which I don't have the 'tools' to answer. If you wanna have a go at it, be my guest, but keep in mind that Philosophy and terms it uses ( which you just admitted are different from everyday English ), like knowledge, realist, idealist, true, etc. are based on a belief system ( justified true belief ??? ) an opinion which can be neither proven or disproven, but serves mainly to 'exercise' the mind with mental gymnastics ( see how I tied that in to my post in that other thread, several days ago 🙂 ). As far as Physics is concerned, I explained what our best, most accurate models describe, and it is certainly not reality, nor can you say it is true, or do you really think a cannonball is empty mathematical space, travelling as a dimensionless point ? So, for the 37th time, and in the 3rd thread, and the 9th person to do so, describing reality is not the business of Physics.

Maybe train designers don't think trains are subjected to extreme stesses. Aircraft designers learned their lesson a long time ago. Again in Britain; read up on the de Havilland Comet. Turns out square windows in a stressed tubular structure are a no-no. de Havilland Comet - Wikipedia

If I'm having a discussion with you, your opinion is the one that matters. As for the cannonball ... It could most certainly be real, depending on your criteria for reality. You must realize, while atoms have a discernible size, their constituent particles have none ( or very very little ). That cannonball may seem solid to your touch, or the light it absorbs/reflects, yet it is almost 100% empty space. What Physics does, is describe it according to Quantum Electrodynamic and Quantum Chromodynamic Field Theories. These theories say the cannonball is simply quantum fields, a mathematical construct which assigns one or more values ( and or direction ) to every point in space, and where that field has an excitation greater than a quantum of action, a particle is manifest. That is what Physics describes, very very accurately; is that reality, and true ? We can also describe the trajectory, and the effects, of that cannonball. To do so, we consider it to be a mass localized at a point; it has no spatial extent. And using that mathematical model/description, we can land a man on the moon ( 1/4 million miles away ) and do fly-bys of the outer solar system planets ( sorry, I'd have to look up the distances ). That is how Physics describes a trajectory, and obviously very very accurately; is that reality and true ?

That's no way to teach. ( although I enjoyed your description as well )

That song should have been banned long ago, Beecee. It's a lawsuit waiting to happen.

You seem to quote a lot of people. Philosophers you obviously admire, and whose thinking you respect. You also tend to put groups of people into different camps, like ( anti ) realists, ( contra ) idealists, etc. I was wondering, do you you ever post what YOU think about these subjects ? A scientist ( Physicist, as I like to pretend I am ), when asked will give you their opinion. Sometimes those opinions even differ, or are totally opposite, other scientists. But I assume you're human, just like the rest of us; surely you must have your own opinion without appealing to the authority of your (philosophical ) masters ? Tell us what YOU think that cannonball 'really' and 'truly' is ... edit And welcome back I thought you might have gotten upset and left us.

If the universe is not homogenous and isotropic, rewinding the clock back wll not lead to the Big Bang. If the universe is not expanding equallyin all directions there is no Big Bang. You don't seem to understand the Big Bang very well. Maybe you should ask questions, or read up on it, before making assertions.

No, assertions carry baggage. A center, or an edge, implies homogeneity and isotropy fly out the window; and we lose two sides of the foundation of the Big Bang Theory. They also imply a preferred frame, something which is not allowed by GR. With GR no longer valid, we lose the third foundation of the Big Bang Theory. We are left with a pretty wobbly structure. Just because we don't know what something is, does not mean we don't know what it can't be. That is the essence of science ( to wax Philosophical ), falsify what cannot be, and keep narrowing down the options of what it can be.

One could make the argument that climate change is simply one of those factors that determines the Earth's carrying capacity for humans ...

Don't try to butter me up after provoking me into almost downvoting you 😄 . I would think a good argument would accomplish the same while also educating less informed/less familiar future readers. I don't expect others to do the same as I do; it is a personal choice for me. And @TheVat seems to think along the same lines

To most Physicist, that is a non-sensical question. To Philosophers, apparently it invokes a lot of distress and hand -wringing ( I didn't want to say sanctimonius posturing; I need to be civil ). Why the concern with what Physics does ? If I have insulted you in any way, I apologize. I don't give downvotes, so you got none from me, as a matter of fact, you got my upvote in the Gravity thread. I appreciate your Philosophical take, much as I have appreciated Eise's over the years. Keep it coming. Just don't be so critical of our Physical take.

It annoys me also. If you disagree with someone's position, tell them why. I don't like it when a downvote is used instead of a good argument, or when you lack an argument. Does the downvote change their mind ? Or is it just a way for you to take out your frustrations ?

Not that Swansont needs me to answer for him ... You must realize, Davy_Jones, that Physics treats the trajectory of a cannonball by considering forces acting on its center of mass, or center of gravity. That is, as a point mass. Is that your 'true reality' ??? We may not know much concerning Philosophy, but you have no clue about Physics ( nor reality, for that matter ). Maybe we ( actually you ) should start over, and, instead of being antagonistic and telling us what is wrong with our world view, try to learn from each other.

The theories are certainly real, and that they make true predictions in applicable circumstances. But they tell us that the underlying 'reality', which you think Physics should be responsible for, is nothing more than indeterminate mathematical constructs like wavefunctions and fields. Even your cannonball and its trajectory is a wavefunction being influenced by a field. That is the knowledge we currently have; do you have the cojones tostand in front of people and say it is 'true' and 'real' ?