What does modern Physics say about reality?

[ralfcis]

"All particles in the universe have a wavelength."

Not when they're stationary they don't. When they're moving they're probably no longer particles.

[BadgerJelly]

Hyksos -

Your OP resonates with me. I believe the resistance you've felt is likely due to science being opposed to anything that cannot be objectively defined. Ambiguity is not the mainstay of the physicist unless you're already respected in the community of physicists.

I think I found soem agreement on this forum before regarding the differences of science and philosophy. Science deals with facts and philosophy deals with truths. The cross-over of these two categories of human investigation lead to a necessary resistance to each other.

Maybe it woukd be better for me to pick through the pdf you posted on the other thread piece by piece. Also my book order shoudl be delivered by the end of the week so I'll be getting more into my original teenage interest in physics and what constitutes the "universe". Really looking forward to reading book abotu chaos.

Anyway, thanks for truly sublime posts over the past year. Some are out of my knowledge range, but they've all been well presented.

[mitchellmckain]

"All particles in the universe have a wavelength."

Not when they're stationary they don't. When they're moving they're probably no longer particles.

It is an odd thing to say in some ways, for it implies that wavelength is a property of the particle, when in fact wavelength like velocity and total energy is relative to an inertial frame. This is the case for all kinds of waves, so it is not like massive particles are special in this regard. Thus it is true that every particle has a wavelength, but only in the sense that we can pick an inertial frame (other than the rest frame) and calculate the wavelength of the particle in that inertial frame the same as for light and other waves.

Actually the oddity of the statement becomes worse the more you think about it. When you understand that it is comparable to saying, "all particles in the universe have a velocity," then we also run into a problem with the uncertainty principle. This principle of QM tells us that if we have a precise measurement of the position of a particle then the particle doesn't have a velocity or a wavelength in any inertial frame.

[ralfcis]

I had a thought on my sun being plucked from the center of the solar system example. What if we stuck a large piece of glass between us and the sun thereby extending the light delay between us. Instead of being flung out into space at the same time the light would fade, the light would remain a little longer. The true reality is the sun is gone but the delay of the sun's info is what causes our reality. So where does invariance matter?

[Asparagus]

That which is undeniable is necessarily agreeable.

Undeniable and necessary are strong words, usually reserved for tautologies and a few first principles.

That's why space and time (being relative rather than invariant), are not a good basis for "reality". Better to stick with invariant spacetime intervals.

Spacetime is relative. If that's true, why wouldn't we say it reflects reality?

[ralfcis]

Yes our delayed reality is a time distorted reflection of the true reality we can't see directly in the instantaneous present. Two realities, both co-exist in a superposition like our reality is the sun is there or, if we could see the instantaneous present, it isn't if it had been removed less than 8 minutes ago. Both are reality but the one that's real to us is the reflection.There is absolutely no way to tell if the sun is really there or not in the present moment.

[hyksos]

A few people are (seemingly?) all opining about some aspect of Special Relativity here. While this is not being articulated incredibly effectively, the consensus seems to be something like the following : There was a traditional notion of "reality" that existed prior to Einstein's 1905-ish developments, that was either lost or trampled on by those developments.

Modern physics stopped talking about reality and began to discuss only what an observer might measure , given some boundary conditions and his own inertial frame. Taken to its apotheosis, physics becomes some kind of predictive 'device' to be employed to predict physical events. "Reality" is sent away to the philosophy dept on a permanent sabbatical.

Did reality lose something -- or was it dispensed with?

'Lost' or 'trampled'?

[Faradave]

"All particles in the universe have a wavelength." ...Not when they're stationary they don't.

Understandable concern. I offer a version of MM's fine reply.

If you travel at the speed of sound along side a sound wave, you won't hear it. You'll be synchronized with (i.e. at rest with) a particular pressure point in the wave. In such a reference frame, that sound should be recognized as a pressure variation in space rather than in time as your motion has "transformed away" its temporal variation.

Similarly, a "static" electric charge will take on magnetic characteristics if observed from a relatively moving frame.

science being opposed to anything that cannot be objectively defined.

Let's not give up on definitions which are objective, even "classical".

Undeniable and necessary are strong words

That's why these characteristics are so valuable.

Spacetime is relative.

Space and time are each relative. Spacetime (e.g. a spacetime interval) is valued, specifically because it is invariant i.e. (not relative). In seeking a framework to hang "reality" on, this is the best bet.

The true reality is the sun is gone but the delay of the sun's info is what causes our reality. So where does invariance matter?

"Delay" and "distance" invoke the relative values of time and space. Invariance suggests something simpler: If you are touching something, it's (still) there.

That's more accurate without the parentheses (which invoke time). From that perspective, if you feel (or see) light from the sun, you're touching it. If you orbit the sun, it's because the sun is touching (thus altering) the path in which you orbit. Gravity and light occur via invariant "lightlike" intervals, defined as zero interval separation.

"For lightlike paths ... the spacetime interval is identically zero."

In a less amicable forum, I've been banned for writing "Zero separation is contact." Go figure!

true reality...we can't see directly in the instantaneous present

Did reality lose something -- or was it dispensed with?

Correct, but understand that "the" suggests something uniquely privileged about our "present". But "present" is just a way of defining a particular spatial region (our "simultaneity": all space for our t=now). Different inertial observers will each have a different "present". In my opinion, these different "realities" are better considered as different views (i.e. space and time perspectives) of an underlying invariant reality.

[Asparagus]

@faradave
Gotcha. So are you thinking of different grades of reality? Does the individual observer have any reason to deny what he or she witnesses? If so, should we deny the news from all the clocks and maps we see? Or think in terms of a greater reality?

[Faradave]

Does the individual observer have any reason to deny what he or she witnesses? If so, should we deny the news from all the clocks and maps we see?

What an individual perceives constitutes a personal reality. That's OK. However it helps to realize, that particular "reality" may not be shared by others, thus dismissed by them. Science seeks common reality, which is sharable with others (scientists, at least).

So are you thinking of different grades of reality?

Science pursues the most generalizable principles, agreed by the most observers. Like universal speed limit c, value derives from invariance. It will be recognized by "enlightened" observers anywhere, doing anything.

[Asparagus]

@Faradave
But isn't it that if I tell you what's true for me, you can just crunch the numbers and discover what will be true for any given observer? So my experience plus number crunching = the invariant situation?


So what is the location of the observer of the invariant intervals? Isnt it that the intervals have these "personal realities" wrapped up in them?

[mitchellmckain]

Yes our delayed reality is a time distorted reflection of the true reality we can't see directly in the instantaneous present. Two realities, both co-exist in a superposition like our reality is the sun is there or, if we could see the instantaneous present, it isn't if it had been removed less than 8 minutes ago. Both are reality but the one that's real to us is the reflection.There is absolutely no way to tell if the sun is really there or not in the present moment.

There really is no such thing as an "instantaneous present" except locally at a singular position. But this is easily fixed and what you are saying still holds. If the present is everything which is not past or future then relative to a particular position it is everything outside the double light cone centered at that point. Physicists sometimes call this "the absolute elsewhere" because it is unknowable and beyond any reach at that moment and location. In other words, it is not just any particular inertial frame (what you call an "instantaneous present") which is unknowable at that moment, but all of them. The know something exists at a particular time then we must wait for that place and time to pass into our past light cone -- that is the region of know-ability. Likewise we an only reach or affect things in our future light cone -- that is the region of affect-ability.

[ralfcis]

Co-location is 1 instantaneous present between 2 participants. 2 participants separated and at 0 relative velocity also share instantaneous present. Relativity of simultaneity (vx/c)converts instantaneous present (the 3rd kind being on a line of present that is slanted due to relative velocity) to delayed present. But if v=0, there is no relativity of simultaneity so there is only an instantaneous present between the two. I guess this means any 2 on any shared line of present share an instantaneous present. Also entangled particles share an instantaneous present as evidenced by the fact no useful information can come out of an instantaneous transfer of information. All this i in more detail on my ralfativity 2.0 thread.

[Positor]

"Delay" and "distance" invoke the relative values of time and space. Invariance suggests something simpler: If you are touching something, it's (still) there.

That's more accurate without the parentheses (which invoke time). From that perspective, if you feel (or see) light from the sun, you're touching it. If you orbit the sun, it's because the sun is touching (thus altering) the path in which you orbit. Gravity and light occur via invariant "lightlike" intervals, defined as zero interval separation.

Isn't it the local radiation that we feel and see, rather than the sun directly?

In a less amicable forum, I've been banned for writing "Zero separation is contact." Go figure!

Perhaps because "contact" is usually thought of as zero space and zero time separation.

If we are "touching" the sun, how is it possible that the temperature we experience from the sun's rays is much lower than (any region of) the sun itself? Doesn't this temperature difference suggest that the site of the radiation's emission is distinct from that of its absorption, and that the term "contact" is therefore inappropriate?

[Faradave]

But isn't it that if I tell you what's true for me, you can just crunch the numbers and discover what will be true for any given observer? So my experience plus number crunching = the invariant situation? ...intervals have these "personal realities" wrapped up in them?

Yes. Einstein gave us that, allowing sufficient information.

Imagine there is a permanent mark on your desk (my mark below looks like a pencil). Two people are tasked with measuring the mark using only a transparent sheet with gridlines on it. Avoiding the easiest method, one sets the grid on the mark so the pencil is the hypotenuse of a 4, 3, 5 right triangle. The other sets his grid so the mark is the hypotenuse of a 3, 4, 5 right triangle.

Having adopted different coordinate systems, the two disagree on the x- and y- components of the triangle but the length of the mark (pencil) is agreed to be 5. So, their coordinate systems may be considered personal constructs of questionable "reality", whereas the mark has an undeniable ("real") length upon which they agree.

So, is there an undeniable (i.e. "real") desktop, which is measured in different ways by different observers? Yes, but to avoid argument and confusion its coordinates should be labeled something other than "x" and "y" (perhaps d₁ & d₂).

When it comes to spacetime, there are some complications. First, there are 4 widely-recognized dimensions rather than two. But a convenient 2-D slice often proves sufficient to make a point. Second, space and time have different units, so universal speed limit c serves as an widely-recognized and undeniable proportionality constant. Third, the relation between space and time is non-Euclidean, as reflected by a minus sign in the equation for calculating interval separation. Fourth, in the presence of gravity (or any acceleration), things get more complicated, so its easier to ignore this at first.

That said, the question at hand seems to be: Is there an invariant ("real") underlying continuum to which all observers (even those which are fundamental "particles") refer. My answer is yes. But to avoid argument and confusion its coordinates should be labeled something other than "space" and "time. They should all be interval coordinates. If that's confusing, they could be called "invariant separations" coordinates. The potential for separation is, after all, what dimensions ("time", "space", etc.) provide.

[ralfcis]

All data needs to be post processed to achieve universal acceptance of the underlying reality. Invariance or an absolute frame of reference is not the reality we experience, it's the reality we calculate. The two co-exist and are not mutually exclusive.

[Asparagus]

That said, the question at hand seems to be: Is there an invariant ("real") underlying continuum to which all observers (even those which are fundamental "particles") refer. My answer is yes. But to avoid argument and confusion its coordinates should be labeled something other than "space" and "time. They should all be interval coordinates.

Thanks! I think you're using the word "real" in a peculiar way, which is fine. I just didn't understand that usage. You could be interpreted this way: statements that are only relatively true are not statements about reality. Only statements that follow from consideration of multiple (or every possible) set of coordinates are about reality.

Some would say that it's confusing to use "undeniable" or "real" to describe the latter. It's absolute. Calling it that would mean you don't have to worry that you might be manufacturing true statements out of dubious, unreal stuff. The underlying ambiguity is real.

[wolfhnd]

The question here seems to be if modern physics has become so esoteric that it takes years of study to converse intelligently about it. The same is probably true of every other science as well. Then I suppose you have to ask if the different scientists have a shared reality. You can expand the question to every individual based on their experience having a unique reality. Which of course is self evident. The implied question then becomes does physics have a unique ability to simplify the universe in such a way that everyone can have at least for a moment, if at different times, a shared reality. For that to be the case then everyone would have to be able to understand it which is obviously not the case unless it can be simplified so everyone can. I see it is that physicists may start to believe that their reality is more real than everyone else's. That is somewhat self evidently not true. Which leads me to say that the meaning is in the purpose to which it can be put not the knowledge itself. Which is complicated by the fact that purpose gets in the way of the kind of abstract thinking that modern science requires. I say this because of how popular it has become to think that science hold the potential answer to everything including morality. So does modern physics have anything to say about morality? We may need a philosopher to answer that but I don't know two philosophers with the same reality.

[hyksos]

The danger is that Physics reduces to a mere calculating device. You put initial conditions into the machine , pull the crank, and it spits out predictions for some particular observer. It tells us what would be observed/measured, and does not (!??) tell us what is there -- what is, that is extant.

"What really happened?" The question should be able to be concretely investigated, provided there is some objective reality independent of observation. Instead, we just return back to the calculating devices to tell us what an observer of a size S , mass m , and velocity v would measure from his 'reference frame'.

Is "reality" equivalent to "what is measured by an observer"? Six, going on seven, centuries of physics, and it seems like we still cannot precisely declare that this is mere semantic distinction, and "Here is why". 120 odd years ago, we should have declared this a semantic distinction, and gone about the business of finding what the universe is made of.

Historically, this did not take place.

[mitchellmckain]

The danger is that Physics reduces to a mere calculating device. You put initial conditions into the machine , pull the crank, and it spits out predictions for some particular observer. It tells us what would be observed/measured, and does not (!??) tell us what is there -- what is, that is extant.

Physics doesn't tell us everything but it does tell us a lot. Calculation is not always required because there are simple examples and general conclusions are possible. Thus you don't have to calculate everything when comparing how fast same size solid balls of aluminum and lead fall to the ground -- even though the lead is four times heavier they still hit the ground at the same time. We know this from physics and yet we didn't have to crank a thing.

"What really happened?" The question should be able to be concretely investigated, provided there is some objective reality independent of observation. Instead, we just return back to the calculating devices to tell us what an observer of a size S , mass m , and velocity v would measure from his 'reference frame'.

We only need measuring devices when we want to make more precise tests. And for various thought experiments it is just a means of making invisible abstractions like time into something more visible and concrete. It helps to nail down what we are talking about more clearly.

Is "reality" equivalent to "what is measured by an observer"?

No. But what is measured by an observer IS a part of reality and furthermore it is a more objective (shared) aspect of reality than personal beliefs.

Six, going on seven, centuries of physics, and it seems like we still cannot precisely declare that this is mere semantic distinction, and "Here is why".

It is not a mere semantic distinction. It is in fact demonstrable that they are not the same thing. We can show that it is possible to know things when there is no measurable evidence of any kind. And thus it is a fact of life that we have to accept a diversity of belief about many things.

120 odd years ago, we should have declared this a semantic distinction, and gone about the business of finding what the universe is made of.

40 odd years ago some people were enslaved and often if others don't agree with what was dictated then they were simply exterminated. Most of the time in most eras of history, very few people cared about the truth. So deposit any idiotic romanticism about times past in the nearest garbage can. Yeah, now that people have the freedom to disagree and so many people take honest inquiry more seriously, things have become a bit more complicated -- get used to it. Simpler does not mean better and making things difficult for the manipulative control freaks is an improvement rather than otherwise.

[hyksos]

mitchellmckain ,

If you are going to equivocate the word "reality" with "that which is measured by an observer" then you are dispensing with the traditional notion of reality.

Special Relativity does not perform the process of specifying a universal Gods-eye-viewpoint of all the parts of a system, and then deduce from that what a particular observer sees. It vehemently does not do this. Instead, the SR calculating machinery demands you specify which observer will have his measurements predicted. The "machine" of SR then outputs intelligible predictions for that observer , and no one else.

(Taking SR seriously as a "depiction of reality" now) SR depicts reality as a collected set of distinct reference frames, within which measurements will disagree between and among, and any "objective state outside of which" does not exist or has no physical meaning.

I did not make any fallacious sophistry in deducing this conclusion. The only 'sin' I committed there was supposing that if the theory makes accurate predictions, it must therefore be hinting at some fundamental aspect of the outside objective world.

In this sense, we could conclude (with some honesty) that the concept that the world is "composed of stuff" is not fitting or appropriate. In this traditional worldview, the word "reality" refers to the "sum total of the stuff". In that situation we are allowed to ask "What happened, really?" and actually mean something concrete. Rather than asking the textbookish : "What will this observer in such an inertial frame measure?" (and then calculate). Modern physics only gives a calculating device, leaving the traditional question with a stone cold silence.

It might be better to talk about "reality" as if it were a collection of events, rather than stuff-like things.

So an observer 'Bob' will experience phenomenal "events" happening -- because reality is made up of events. The alternative does not make sense vis-a-vis SR. SR says two comoving observers will disagree on whether two events happened simultaneously or not. They will see the same object emitting different colors from redshift and blueshift of their "frames". If reality were composed of "stuff that reveals its state to observers" then Bob and Alice would always measure the same properties on the same object, rather than disagreeing completely on how fast such-and-such clock was ticking "from my vantage point".

SR reality can be given a funny name. We might call it Process Philosophy : Events , not Stuff

(-- and start yammering about Alfred North Whitehead.)

[mitchellmckain]

If you are going to equivocate the word "reality" with "that which is measured by an observer" then you are dispensing with the traditional notion of reality.

But I am not going to equate these two. When you asked the question of whether these two are equal, I said no. But neither will I go to the other extreme that you would like to say they are totally different. What is measured by an observer is PART of reality, just like everything else. Furthermore, science gives us a means to find what is the same for everyone, so it does give us a handle on the objective apprehension of reality as opposed to the subjective aspects of reality which we cannot expect any agreement about. My position is NOT to negate the subjective aspects of reality (and thus equate the objective with reality itself), but to recognize that when we do want the things we can agree upon then we must look to the objective aspects which science can give us.

Also I will oppose people who try to push their subjective apprehension as objective insisting that other people must accept what they dictate. A diversity of thought about such things must be accepted.

Special Relativity does not perform the process of specifying a universal Gods-eye-viewpoint of all the parts of a system, and then deduce from that what a particular observer sees. It vehemently does not do this. Instead, the SR calculating machinery demands you specify which observer will have his measurements predicted. The "machine" of SR then outputs intelligible predictions for that observer , and no one else.

Incorrect. It makes the correct prediction for EVERY observer in the same circumstances described (the same inertial frame). The fact that it gives different predictions for different circumstances does not subtract from the objectivity of its predictions in the slightest.

(Taking SR seriously as a "depiction of reality" now) SR depicts reality as a collected set of distinct reference frames, within which measurements will disagree between and among, and any "objective state outside of which" does not exist or has no physical meaning.

Correct, but the restriction is upon the objective view regarding physical measurements only. It is telling us the limits upon the objective determinations of science.

I did not make any fallacious sophistry in deducing this conclusion. The only 'sin' I committed there was supposing that if the theory makes accurate predictions, it must therefore be hinting at some fundamental aspect of the outside objective world.

I have no criticism of making subjective arguments in general as long as that subjectivity is acknowledged (and thus diversity of thought accepted).

In this sense, we could conclude (with some honesty) that the concept that the world is "composed of stuff" is not fitting or appropriate. In this traditional worldview, the word "reality" refers to the "sum total of the stuff". In that situation we are allowed to ask "What happened, really?" and actually mean something concrete. Rather than asking the textbookish : "What will this observer in such an inertial frame measure?" (and then calculate). Modern physics only gives a calculating device, leaving the traditional question with a stone cold silence.

I disagree. It is no more silent on the subject than religion, philosophy, and personal experience. It may be a background of noise to which you have to decide how to attach meaning, but it is NOT silence! Plus the difference from these other things is that it is the SAME "noise" for everyone.

It might be better to talk about "reality" as if it were a collection of events, rather than stuff-like things.

Sure... it MIGHT be. But don't go overboard with the claim that this is the ONLY way that science looks at things. Science also looks at reality in terms of "stuff-like things" too --particles, atoms, molecules, elements, stars, black holes, gasses, liquids, solids, etc... And there is one stuff-like thing, energy, which all of the things are different forms.

Also it MIGHT be better to look at the universe as a singular thing rather than a collection because it is all about rules concerning how all these supposedly different things are connected and can change into other things as if they are all a part of a greater whole.

So an observer 'Bob' will experience phenomenal "events" happening -- because reality is made up of events. The alternative does not make sense vis-a-vis SR. SR says two comoving observers will disagree on whether two events happened simultaneously or not. They will see the same object emitting different colors from redshift and blueshift of their "frames". If reality were composed of "stuff that reveals its state to observers" then Bob and Alice would always measure the same properties on the same object, rather than disagreeing completely on how fast such-and-such clock was ticking "from my vantage point".

They will only disagree as long as they insist on a motion picture film view of reality as consisting of instantaneous pictures strung together. But if they embrace the bigger vision of reality given by SR with a relativity of simultaneity and a present which includes everything between the past and future light cones (only defined relative to a given place and time) then they will not disagree any more. They will see the same object emitting light whose wavelength in the object's own inertial frame is fixed but which has a different wavelength in other inertial frames. AND THUS they CAN measure the same properties on the same objects, thereby going past appearances to the real stuff.

SR reality can be given a funny name. We might call it Process Philosophy : Events , not Stuff

(-- and start yammering about Alfred North Whitehead.)

Yeah all the different philosophies, religions, and ideologies are only too ready to cram the perspectives and understanding given by science into their own patterns of thought.

[wolfhnd]

How about this>

Suffering is truth. Physics informs us about a reality. Information needed to reduce suffering.