Things are observable either directly or indirectly. Direct observation of a thing is made with the senses, with sight for example. The moon can be directly observed. Indirect observation of a thing can be made by observing the effect it has on a directly observable thing. Electrons or x-rays, which can only be observed indirectly, produce observable effects on a phosphor screen or photographic film.

The existence of a thing is verified by observing it. Anything that cannot be directly or indirectly observed is a hypothetical thing whose existence is supposed or imagined.

The universe itself cannot be directly observed. Only a portion of what is out there can be directly observed. As for indirect observation, the universe does not seem to produce effects on the things that can be directly observed. Since the universe itself cannot be directly or indirectly observed, it seems to be a hypothetical thing.

Nonetheless, the universe is not considered to be hypothetical. Physical properties (such as density and entropy) and histories (such as Big Bang or Steady State) attributed to the universe presume that the universe physically exists. What justifies the idea that the universe has physical existence?

It doesn't all this is a figment of your imagination. In a moment you will wake up and it will all have gone away. Then you're in trouble :wink:

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'The eye can only see what the mind is prepared to accept'

Is the universe real? What is reality? Are we real?

You can drive yourself crazy...or just accept what *is*.

"Reality is merely an illusion, albeit a very persistent one." Albert Einstein

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An open mind is like an open window...without a good screen you'll get all sorts of weird bugs!

Attempt at a definition:

A universe is a group of galaxies whose light can be can be seen by one another, given enough time for the light to reach one another, and the space inbetween the galaxies. (I have to include 'maximal' somewhere, to make certain that you have all the galaxies and not just three or four or so).

Do we have anything that we can observe that fits the description? Yes? That's the universe. Nothing hypothetical, but not a 'thing' but more a group description. Like a galaxy, or a flock, or a cluster, or a troop. But slightly bigger!

Now, you can discuss if the universe is finite or infinite, steady state or inflarting or whatever, but that doesn't mean that it is imaginary or hypothetical. It could well be argued that 'other universes' are hypothetical though, but our universe, in my view, isn't.

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Knowledge is a curse, but ignorance is worse

You're asking questions that Kant answered quite some time ago. For anything within the universe to exist, the universe itself must be taken as a priori, or something taken as true so that everything else can follow. You cannot make any observations or predictions without assuming its truth.

Of course you're completely wrong in this!! [-(

You are all a figment of MY imagination and you're all history when my alarm goes of in the morning!!! :wink:

We can infer a likely existence for the universe by directly observing the portion we´re limited to (and it ´s not a small one). This portion has to be contained within a "totum". It is important to bear in mind that our senses themselves are very limited, preventing us from capturing the real essence of reality. They often fool us.

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"Shut up and calculate" R. Feynman

N C More wrote:We are limited to two kinds of experiences: those that originate from sensing of the world outside the mind and those that originate within the mind. The former always represent reality (even if not understood), while the latter can represent both the real and the unreal. The unreal exists only in the mind. A fundamental postulate of science is that objective reality is that which exists independent of any thinking subject

But just because the universe is considered to exist as a physical thing by many people doesn’t make that an *is*. There is ample evidence from that past that many people have thought many ideas to be true that were subsequently proven to be false.

Fram wrote That definition leaves some unresolved issues. A galaxy cluster is also a group of galaxies whose light can be seen by …etc. The universe and a galaxy cluster cannot share the same definition. Clusters, in turn, group together as superclusters, but we cannot be certain that superclusters are the ultimate building block of the universe. Nor can we be sure that there is such a thing as an ultimate building block of the universe.

Your definition, in terms of ‘light’, omits things that do not emit light and is therefore not sufficiently inclusive. Your use of the word ‘all’ in the term ‘all the galaxies’ shows that you consider the universe to be some kind of collection. Galaxies were known to be separate objects well before Hubble came on the scene. Hubble resolved individual stars of the Andromeda galaxy and verified that galaxies are huge collections of stars. He also verified that Andromeda was not a part of the Local galaxy as some had thought. Notice regarding galaxies that the existence of the container was verified before contents were assigned to it. The same cannot be said for the universe, whose existence has never been directly or indirectly verified.

Fram also wrote: If the universe is not a thing, then it cannot have physical properties and a history. You are taking the ATM side!

Normandy6644 wrote:Kant, of course, was not merely implying that for things to be inside a container there must first be a container . If Kant were alive today he would change some of his views in light of contemporary neurology. The a priori at the base of all knowledge is the neural system. It is pre-wired to let us recognize many things. The infant is born with not only the neural connections for several reflexes, but with mental templates for hunger, thirst, pain, pleasure, for correlation between the senses and the body location of the sensors, for meaningfulness, and for recognizing and expressing the concept of negation. It seems that even a template for grammar is one of them. It is only with those a priori features that everything else can follow. It is only because of those that observation, prediction, and verification of truth can be made. A universe is not needed to justify the existence of any thing. Rather, it is the universe idea that is now in need of justification, as I have indicated above.

Argos wrote:All we can verify by directly observing any sized portion of what’s out there is that certain things exist in that portion. We cannot infer that the universe exists from the fact that we have identified stars to exist, nor from the fact that we have identified galaxies to exist, nor clusters.

As for the claim that the portion is not a small one, the verdict is not in yet. It may be that the observable portion is infinitesimally small compared to what’s out there.

At whatever scale you wish (atoms, stars, galaxies, clusters, superclusters) if there are an infinite number of them, there is no “within”, no containment, no “totum”. Until it is proven that there is not an infinite number of anything, the idea of an infinite number of any cosmic thing is equally likely.

Actually, I'd claim that if you're going to get technical about this, nothing is directly observed. You experience certain sensoria, and infer the existence of external objects. This is just as true of chairs and tables as it is true of electrons and x-rays, though there may be more intermediate steps for the latter. That doesn't change the fact that the experience of more conventional objects remains indirect.

However, if we grant that there do exist external objects which are responsible for your sensory experiences, then the existence of the universe shouldn't be a problem. If we define the universe in the most reasonable fashion, as everything that exists, then if there's anything that exists, there must be a universe. In fact, even if we don't grant that your sensoria correspond to external objects, there's still a universe, since by Decartes reasoning, at least I exist, so something exists whether or not my senses are reliable. The fact that we can't experience the entire universe merely means that our knowledge of it is incomplete, not that it isn't present.

As I walk through a large expanse of trees, I am struck by the fact that I cannot see the forest, only part of it at a time, yet I still see the forest.

I cannot step back and see the whole of the universe, but I see what is around me. That is evidence prima facie that the universe exists. We may not know the extent of it, or many othre things about it, but its existence in front of my face is enough to settle its existence for me.

Or were you infering that it only exists in your mind?

The universe exists as a vertual model in your mind but it is real in the sense that if you stop eating or drinking you WILL die, or if your house burns down you might get burnt.

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Nicely said, Enzp.

Ah! It must be spring!

The swallows have returned to Capistrano, the buzzards to Hinkley, the monarch butterflies are on their way back, and Richard J. Hanak is back to tell us why the Universe does not exist.

By the way, I think the weak point of his first post is this:

I think you are wrong in saying that "the universe does not seem to produce effects, ..." . Those who espouse Machianism hold that the very inertial masses that we experience are caused by the universe as a whole. They have yet to give a complete exposition of how this arises, however. My own research indicates a possible influence of the cosmological expansion upon the expectation value of the field that gives masses to the quarks, leptons and weak gauge bosons, which might qualify as an indirect effect of the whole universe upon the objects within it. Unfortunately publication is a long way off.

It is also worth noting that the value of the infamous Pioneer anomaly acceleration is approximately equal to H0*c, which may be another indirect effect, if this explanation for it pans out.

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Microsoft is over if you want it.

The bar has been lowered for the promotion of ATM ideas; the bar for the acceptance of ATM ideas must remain high.

I'll just refer to the same answer I always give when asked "how do you know this is real?"

See my signature. 8)

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"Reality is that which, when you stop believing in it, doesn't go away."
Philip K. Dick, Do Androids Dream of Electric Sheep?
"A lie can travel half way around the world while the truth is putting on its shoes."
Mark Twain

Avatar courtesy of Bunny.

Grey wrote:In my opening paragraph above I defined my intended meanings for direct and indirect observation in this thread. As for your claim that nothing is directly observed, consider the following.

Recognition of the self is a prerequisite and reference of comparison for recognition of the external. All animals possess a sense of self no matter at how rudimentary a level. It is a requirement of survival to know what is one’s self in order protect oneself from inadvertent destruction by oneself or by others. Anything sensed as being not of the self is recognized as being external to the self without the need for inference. The sea snail, for example, has a very small number of neurons, many orders of magnitude smaller that what is required to support the logic necessary to engage in inference. The presence (existence) of external objects detected by its sensors is directly interpreted by its neurons without any need for inference. Similarly the newborn human infant knows the difference between self and not self, between self and others, and between internal and external.

Enzp wrote:The second and fourth clauses of that sentence contradict each other, rendering the sentence meaningless. If all you see at any time is a part of the forest (i.e., some trees), then all you have seen is parts of the forest, not the forest itself. To see the forest itself (or to know that there is such a thing as a forest) you have to move to one or more positions that let you see where the forest begins and where it ends. Since that can’t be done for the universe, a different method is needed to know that there is such a thing as the universe and to justify the universe idea.

Enzp also wrote:The things you see around you give evidence only that they exist. As I wrote above:Is there a line of reasoning that connects knowing that certain things exist with knowing that the universe exists?

Frog march wrote:If the universe exists only as a mental model, then it is not a physical thing to which properties and histories can be attributed. You, too, are taking the ATM side. The realities of death and danger do not justify the universe idea. Neither do the realities of birth and security.

Celestial Mechanic wrote:Hi Celestial Mechanic. Yes, the sap has risen!
Celestial Mechanic also wrote:When Mach blamed the inertia of masses on the universe it was not yet known that there were things beyond the local galaxy. In his time the universe seemed to be finite and could be conceived of as an entity in its own right. In those days the expression “the universe as a whole” made sense.

However, when Hubble discovered that the other galaxies were not parts of the local galaxy, the finiteness of the universe became questionable, especially as observed cosmic distances and the number of observed things quickly escalated. There has been no hard proof for either a finite or infinite universe. At one time Einstein wrote that the universe could not be infinite because that would lead to an infinite number of gravitational lines of force at any mass object. I don’t think that could be right because we know that the sum of an infinite series of addends can be finite. Sort of reminds one of the Olber’s paradox. If the universe is infinite then it cannot be considered as a whole or as a thing to which physical properties and histories can be attributed.

The Machiains don’t really need a universe as a whole to produce local inertia. They should be willing to settle for some great number of distant masses. No one will deny them that. But there is not even a hypothetical mechanism suggested for how the distant masses could produce an effect on local masses.

If, as Mach suggested, the inertia of a local mass arises from the presence of very distant masses, wouldn’t the presence of very close masses strongly affect the inertia of a local mass? But I don’t think that has been observed. My own theory of inertia is that the inertia of a mass is a reaction to its own gravitational field. Work is required to distort the field. I have not been able to formulate the equations. I think it is premature to say whether or not the universe produces local effects. Using Mach’s hypothesis to justify the universe idea seems to be grasping at straws.

P.S. I notice that you wrote “Those who espouse Machianism….” Rather than ‘We who espouse Machianism.’:

Kesh wrote:Thank you. That is another way of expressing what I wrote in the opening paragraph of this thread.

I didn't mean that the model of the universe inside the mind is the only universe but we have no real way to tell whether or not it is in the same way as the people in the matrix(The Matrix) could tell what was real or not.
All you really have is sensory input from which the mind creates a working model.
If the universe was only the model then you could stop eating and it wouldn't matter.

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I fail to see what one has to do with the other. There have been mistakes made in the past, and there will also be mistakes made in the future...SO WHAT. Just how does that equate with your "idea" that the Universe may not be "real"? You posted (the quoted paragraph) as if there is some kind of connection between the 2...there is not.

"The universe" is not a theory. It's basically just defined to be "everything," whether we can see it or not. It's not a hypothetical thing. It's a postulate thing. We don't know what exists or if anything exists outside our light horizon. Whether there is something or suddenly nothing beyond our light horizon, that doesn't mean the universe is "hypothetical". It still "is".

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Everyone is entitled to his own opinion, but not his own facts.

Hanak: "Recognition of the self is a prerequisite and reference of comparison for recognition of the external. All animals possess a sense of self no matter at how rudimentary a level."

You may infer that, but obviously you do not know it from direct experience. (You have never experienced being a rove beetle, or experienced snailhood.) Therefore by your own criteria your statement does not refer to anything 'real.'

Hanak: "It is a requirement of survival to know what is one’s self in order protect oneself from inadvertent destruction by oneself or by others. Anything sensed as being not of the self is recognized as being external to the self without the need for inference."

Again, this is speculation. It's not observable, objective fact, eh? How do you know that a sea snail does not perceive it's wat'ry home as simply an extension of its own being? Perfectly possible, my good man, perfectly possible: one may design algorithms for sensory detection and response in completely unalive machines.

One can do it with springs, weights, and levers without even bothering to write a computer program. Such a system is inanimate -- yet it can act to preserve a condition or set of conditions just as a sea snail or bacterium seeks to preserve its living conditions, say, by avoiding excessive heat.

Point being, what you suppose about sea snails is not necessarily 'real.' In the sense that your first posts insist