MigL

Not sure if I would goall the way o free, if there is really 'free' anything. But certainly subsidized enough so that a student could work a summer job to earn enough for his/her tuition. Things you have to work for are always more valued/appreciated.

Yet we saw th case, in 2008, where house hold debt, brought world economies to their knees.

Given that rates are historically low and practically zero, they have literally nothing BUT opportunity to raise them, significantly or otherwise. How so? One of the 'controls' used to keep inflation at manageable levels is variance of lending rates. Once the citizenry has taken on too much personal debt, the ability to raise lending rates has to be used very carefully ( or not at all ) as it would lead to massive defaulting on debt, bank failures and recession. As in 2008. We realized, then, that unrealistic debt levels were a problem, and stricter controls over borrowing were solutions, yet in my area, home ownership has become impossible or young pople, due to house prices doubling in the past two years ( over 1/2 Million is entry level ). Scarcity of rental property ownership has resulted in skyrocketing rents, and increased homelessness Have we already forgotten ?

Isn't the bolded part exactly what Physics does ? Thereby making Markus' statements, about Physics, 'true'. ( or am I just Philosophising ? 😄 ) I also think Davy_Jones brought some interesting topics to the forum that got people participating again. I must say, I did enjoy his brief time here.

You choose from your available options; I'll choose from mine. And sometimes we make our own 'hell' by the options we choose. It's not always someone else's fault.

And if those entities are Philosophers, they may open several threads to convince the rest of us that theirs is the only 'true' meaning of reality ?

If by 'keep on going' you mean do things, like work, then it is energy that keeps it 'going'. Energy has some funny properties. If you have a box divided by a partition, where one side has a more energetic gas than the other side, the partition will be accelerated, and move. That is an example of doing work ( much like the pistons moving in your car's engine let you travel down the road ) When the gas on both sides of the partition has equal energy, obviously the partition will stop moving, and no more work can be done. Notice that the total gas still has energy, but it is the difference in energy that allows work, and processes to happen. So, we have useable energy, which can do work, and un-useable energy which cannot. We call this process, of converting useable energy into un-useable, entropy. Entropy can also be a measure of the 'order' of a system, which means that, although it can be reversed locally ( life is proof of that ), it must always increase globally. That is where the idea for the 'heat death' of the universe comes from. Once entropy of the universe is maximized, and there are no more energy differences, all work and processes will cease, and the universe will essentially be dead. This is a rather simple explanation, which is, hopefully, suitable for your level of understanding. If you should need elaboration, don't be afraid to ask.

Studiot's example considers the space-time interval ( actually a 2d interval in his example ), but you are right md65536, it doesn't illustrate the geodesic deviation ( I have to stop saying curvature because of the implications ).

That is NOT true, and could not have really happened! You are not 300 years old so you could not possibly have heard him say that. On the other hand, it is certainly true that he said that, Don't you see the variability of the word 'true' ? Atoms are now real ? Their effects and interactions can be observed and measured for sure ... Ask Mr Perrin if the mass of three quarks, which cannot be separated, that make up a proton/neutron in an atom, add up to the mass of said proton/neutron. Ask him to measure the diameter of one of those quarks, or an electron, that make up those atoms. Then ask him by what definition of reality do the masses of three dimensionless points add up to less than 2% of the mass of the particle they make up. Surely his definition of 'real' is not the same as yours. I am learning a little Philosophy from you, as I hope you are learning a little science from me, however I must admit, I am a little puzzled by this Philosophical technique you are using. What do you call it ? Beating your head against the wall, and insisting others use your definitions to describe their concepts, even after being repeatedly tol that your definition is not applicable ? Oh, and I fail to see why the opinions of the scientists you quote are any more relevant than the opinions of the scientists on this forum. If anything, they simply illustrate the variability of words like 'real' and 'true' to scientists, as opposed to the one-and-only definition, written on a gold bar and stored in a vault in France, that you Philosophers think everyone should use.

Wasn't that the point of your other thread, where you were told science describes effects and interactions, but does not so much care if things are 'real' ? You place too much emphasis on the word 'real'. He means real in the sense that the oserved effects are due to a grvitational interaction between massive particles, as opposed to an inadequacy of our gravitational model ( see MOND ) or a misunderstanding of the science. Real and true are not sacred words to scientists, although Philosophers seem to think so. Was that not the thrust of your second thread, the difference between Philosophy and Science ? We have different uses for those two words ( and probably others ), yet instead of being multicultural, and celebrating those differences, you want to make us conform to the Philosophical usage. ( I'm from Canada, we embrace multiculturalism here 😄 ) edit Frank Sinatra and poached eggs are both overrated. I prefer Dean Martin and over-easy.

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 )