General, Introductory Physics

[Cole]

I'm interested in learning about physics. Since I have very little knowledge on the subject currently, I'd like to find a good general, introductory explaination. I would want for this source to be rational (doesn't contradict Objectivist metaphysics).

Does anybody know about specifics to Leonard Peikoff and/or David Harriman's take on the subject? Do they hold any beliefs that contradict commonly-accepted views among physicists?

I understand that most (if not all) physicists hold it to be undeniably true that the universe is expanding. This seems to contradict Objectivist metaphysics, and the idea that the universe is eternal. Also, Ayn Rand denied that "infinity" is a metaphysically possible scenario. However, I can't comprehend there being a limit to physical space in the universe. I also can't comprehend physical space being infinite and therefore unmeasurable. Can anybody help clear up my confusion on this issue?

[HaloNoble6]

I think these questions have been dealt with before here and in a better way than I think I can contribute, but I'll tell you what my own understanding is anyway.

As I understand it, "universe" denotes "all existents" as well as the "empty space" between them, although sometimes I think some people make the mistake of thinking it denotes "all empty space," which implies that empty space is finite: since empty space denotes the absence of something, it is not an entity, and as such is not "finite," for it isn't something. That being said, I think when scientists say "the universe is expanding," it may seem as though they are being a bit ambiguous, because though it is true that entities which are subject to gravitational fields are moving away from the origin of a very large "explosion" ("the big bang"), empty space ("the lack of something") cannot expand (it is not an entity), so it might seem as though scientists are presuming that 1) "empty space" is finite and 2) that this empty space is expanding.

That being said, the "big bang" does not contradict the eternal nature of the universe: the eternal nature of the universe does not preclude the existence or occurrence of explosions capable of causing what we're seeing today.

So, to essentialize: "empty space" or "nothing" is not an entity as such, thus it makes no sense to talk about its qualities or quantities: "nothing" has no identity; further, the eternal nature of the universe does not preclude the existence or occurrence of explosions; finally, one way to think of the universe is that it is finite in entities, but eternal in existence. This is, at least, my understanding of the answer to your questions.

[Cole]

I don't understand what "empty space" is.

I'm having a hard time comprehending the notion that physical space is finite. Wouldn't this mean that if I moved in one direction long enough that I would reach some sort of end? I can't imagine how this is possible. It's absurd to think that something can exist beyond reality, but I don't understand how this applies to physical space. Still, there must be a limit to how much space exists in the universe, right?

[HaloNoble6]

"Empty space" is the absence of "something." It is not an entity with an idenity. If you're using "physical space" to mean the same as "empty space," which I think you are, it might be making the matter more difficult for you. "Empty space" is the absence of something, it is not a something, it is not physical, it is absence, non-being. It doesn't make sense to talk about "the limit" of "nothing."

[punk]

I'm interested in learning about physics. Since I have very little knowledge on the subject currently, I'd like to find a good general, introductory explaination. I would want for this source to be rational (doesn't contradict Objectivist metaphysics).

Does anybody know about specifics to Leonard Peikoff and/or David Harriman's take on the subject? Do they hold any beliefs that contradict commonly-accepted views among physicists?

I understand that most (if not all) physicists hold it to be undeniably true that the universe is expanding. This seems to contradict Objectivist metaphysics, and the idea that the universe is eternal. Also, Ayn Rand denied that "infinity" is a metaphysically possible scenario. However, I can't comprehend there being a limit to physical space in the universe. I also can't comprehend physical space being infinite and therefore unmeasurable. Can anybody help clear up my confusion on this issue?

None of this is "introductory physics".

All issues involving the finiteness/infiniteness of the universe, and the expansion of the universe are ADVANCED issues. I wouldn't bother analyzing the physics of these issues without a solid grounding in advanced mathematics (including tensor analysis).

Introductory physics is about throwing balls and collisions and spinning things and such.

[HaloNoble6]

All issues involving the finiteness/infiniteness of the universe, and the expansion of the universe are ADVANCED issues.  I wouldn't bother analyzing the physics of these issues without a solid grounding in advanced mathematics (including tensor analysis).

I disagree, you don't need to understand advanced mathematics to understand that "nothing" is not an entity, that only entities can move and/or expand, or that the universe does not have a beginning. These are actually philosophical questions. In fact, the concept of "nothing" is given special attention in Introduction to Objectivist Epistemology.

[Cole]

"Empty space" is the absence of "something."  It is not an entity with an idenity.  If you're using "physical space" to mean the same as "empty space," which I think you are, it might be making the matter more difficult for you.

I'm not talking about empty space, and I don't know what got you caught on that. I am talking about space.

It doesn't make sense to talk about "the limit" of "nothing."

For the record; you brought up "empty space," not me. My questions weren't in reference to it, beyond asking you what it was. I am not talking about the limits of nothing. I am talking about the limits of space. It must be finite, right?

[Cole]

None of this is "introductory physics". 

All issues involving the finiteness/infiniteness of the universe, and the expansion of the universe are ADVANCED issues.  I wouldn't bother analyzing the physics of these issues without a solid grounding in advanced mathematics (including tensor analysis).

Introductory physics is about throwing balls and collisions and spinning things and such.

They were two seperate questions. I asked for a rational introduction to general physics. I also asked for clarification on something that seems to be a given in physics conflicting with Objectivist metaphysics (or, at least, conflicting definitions of "universe").

[Cole]

I disagree, you don't need to understand advanced mathematics to understand that "nothing" is not an entity, that only entities can move and/or expand, or that the universe does not have a beginning.  These are actually philosophical questions.  In fact, the concept of "nothing" is given special attention in Introduction to Objectivist Epistemology.

Felipe, I understand that "nothing" is not an entity. I understand that the universe is eternal. I've read ITOE. I never said anything that would imply otherwise.

My questions were; If the universe is all that exists, then how can it possibly expand? If space is necessarily finite, then what happens at the limits of space?

[punk]

I disagree, you don't need to understand advanced mathematics to understand that "nothing" is not an entity, that only entities can move and/or expand, or that the universe does not have a beginning.  These are actually philosophical questions.  In fact, the concept of "nothing" is given special attention in Introduction to Objectivist Epistemology.

Don't pretend you are doing talking about "physics" while you are doing all this.

[punk]

They were two seperate questions.  I asked for a rational introduction to general physics.  I also asked for clarification on something that seems to be a given in physics conflicting with Objectivist metaphysics (or, at least, conflicting definitions of "universe").

Personally I'll take something that appeals to empirical data over "metaphysics" any day.

You know this is all getting strangely reminiscent of medieval "angels dancing on the head of a pin" argumentation. People could come up with all sorts of rational reasons why heavy things fall faster than light things based on this or that metaphysics. Unfortunately a simple appeal to experiment proved all the aristotelian rationalistic argumentation wrong.

[Cole]

I looked into it a bit more and discovered that the theory of spatial infinity is not accepted among all physicists- as I had previously thought. Although infinite space is difficult to comprehend, I find finite, limited space to be equally difficult to comprehend.

And I've concluded that physicists who declare that the "universe is expanding" are using a flawed definition of the word "universe."

[HaloNoble6]

Cole, please precisely define what you mean by "space," and please try to compare and contrast it with what I call "empty space." It seems clear to me that I've already stated what you've concluded, namely that scientists might be using an ambiguous definition of "universe." Also, if by "physical space" you mean something like the vacuum between the earth and the moon, then "empty space" is synonymous with what you call "physical space," therefore, all my previous comments apply and I'm not off on some wild tangent.

Punk, your belief in the chance that there may exist a contradiction between the Objectivist metaphysics and physics as understood through experimental data reveals an incomplete understanding of the relationship between metaphysics and science. Namely, there can be no valid theory supported by scientific data which contradicts existence exists. Since the Objectivist metaphysics consists of the step-by-step unraveling of the corollaries of existence exists, which is the core of man's understanding of reality, nothing in the sciences can ever contradict the Objectivist metaphysics. The Objectivist metaphysics is not, as you imply, derived via "rationalization;" rather, it is derived by using reason to systematically ascertain all the implications of existence exists.

[jrs]

I get the impression that most Objectivists disagree with Quantum Mechanics and both Special and General Theories of Relativity. I think that they are over-interpreting their philosophy to draw unjustified conclusions. Basically they are reading the common prejudices which obstruct understanding of these theories into their "Axioms".

The expansion of the Universe means that the distances between clusters of galaxies are steadily increasing.

So called "empty space" contains various force-fields including the electromagnetic and gravitational fields.

Space does not have an end.

Although it is not certain, the best available indications are that space is infinite in extent and contains an infinite amount of matter.

[HaloNoble6]

I wish some of you noobs would take the time to try and understand Objectivism prior to making erroneous assertions about it. Why don't you take the time to read, or just ask, about axiomatic concepts, before putting quotation marks around axiom.

Do not make pronouncements about Objectivists when, based on your post above, you haven't the slightest understanding of the foundations of Objectivism.

Edit: added last sentence. --Felipe

Edited April 13, 2005 by Felipe

[jrs]

Felipe:

On the subject of Objectivism's axioms:

In the "Can God Exist?, Why or why not?" thread of the "Metaphysics and Epistemology" subforum, TomL said (Apr 11 2005, 09:37 PM) "'Existence exists' doesn't mean what you think it means. It means existence has always existed and always will. It was never created; there has never been a time of non-existence, from which it must have been created. Ever. The universe is eternal, in both directions of time.".

That the universe is eternal (towards the past in particular) may very well be true.

But I would contend that if "Existence exists." meant what TomL said it meant (which it does not), then it would not an axiom as defined by Objectivism.

On page 7 of OPAR, Rand is quoted as saying "[An axiomatic concept is] the identification of a primary fact of reality, which cannot be analyzed, i.e. reduced to other facts or broken into component parts. It is implicit in all facts and in all knowledge. It is the fundamentally given and directly perceived or experienced, which requires no proof or explanation, but on which all proofs and explanations rest.".

Correct me if I am wrong, but I take this to mean that a two part test is required for a proposition to be an axiom:

1. It must be known to be true by direct perception.

2. It must be a proposition which is explicitly or implicitly assumed in any proof.

These would apply to "Some entities exist, including those entities which I perceive.". This is my understanding of "Existence exists.".

It seems clear to me that neither of these properties is possessed by TomL's version. We cannot directly perceive what happened before the Big Bang, so we cannot know that the universe is eternal towards the past. And we certainly do not need to assume that to prove facts about every-day life.

This is an example of how some Objectivists read too much into the axioms.

[HaloNoble6]

Great, you've got a copy of OPAR on you. At present I'm finishing up a pset for class that's due today, so I can't address your point with as much thoroughness as I'd like. Nevertheless, it seems like you're making things more complicated than they need to be. The simplest way to think of it is: "axiomatic concept" if and only if "perceptual self-evidency." Also, the validity of an axiomatic concept does not depend on my or your ability to grasp it, nor does its scope of applicability depend on the number of entities I can directly perceive.

I'm sure someone can help you out here before the day's done.

[Cole]

Felipe, I'm still familiarizing myself with the vocabulary.

What I meant when I used the term "space" was the spatial relationship between objects in which no other objects exist. (I'm unsatisfied with that definition, but I can't figure out a better one. I hope you can understand what I mean). My confusion with your description of "empty space" is how something synonymous with "nothing" can be measured (i.e; you describe the empty space between the Earth and the Moon). I'm also confused by the fact that I've always understood "takes up space" to be an essential attribute of matter.

[HaloNoble6]

Something synonymous with "nothing" can be measured only with reference to the "something" which could fit into that "nothing." But to speak of "space" or "nothing" as apart from "something" takes you outside the realm of measurability because you are no longer anchored to the concept of something. I know, I think I sound vague, let me give this one more whirl.

"Space" must always presuppose "the something that could fit into that space." Without this referent, one no longer is capable of measuring as such because it is entities that have finite qualities and quantities; and "space" does not qualify as an entity. So, "space" itself is not "measurable" without reference to existents. I hope this is clearer.

[Cole]

Yes, it is very clear now. Thank you for your help.

[punk]

Cole, please precisely define what you mean by "space," and please try to compare and contrast it with what I call "empty space."  It seems clear to me that I've already stated what you've concluded, namely that scientists might be using an ambiguous definition of "universe."  Also, if by "physical space" you mean something like the vacuum between the earth and the moon, then "empty space" is synonymous with what you call "physical space," therefore, all my previous comments apply and I'm not off on some wild tangent. 

Punk, your belief in the chance that there may exist a contradiction between the Objectivist metaphysics and physics as understood through experimental data reveals an incomplete understanding of the relationship between metaphysics and science.  Namely, there can be no valid theory supported by scientific data which contradicts existence exists.  Since the Objectivist metaphysics consists of the step-by-step unraveling of the corollaries of existence exists, which is the core of man's understanding of reality, nothing in the sciences can ever contradict the Objectivist metaphysics.  The Objectivist metaphysics is not, as you imply, derived via "rationalization;" rather, it is derived by using reason to systematically ascertain all the implications of existence exists.

Please give me an argument from "existence exists" to some sort of conclusion on whether the universe is expanding.

Personally I'll go with the simple observation of the red shifts of distant galaxies to reach the conclusion on this, but please give me the a priori rational argument here. Please include detailed steps, as I seem to be confused.

[punk]

I wish some of you noobs would take the time to try and understand Objectivism prior to making erroneous assertions about it.  Why don't you take the time to read, or just ask, about axiomatic concepts, before putting quotation marks around axiom.

Do not make pronouncements about Objectivists when, based on your post above, you haven't the slightest understanding of the foundations of Objectivism.

Edit: added last sentence. --Felipe

Why dont you give a detailed application of the objectivist "axioms" to this topic.

I've read enough here to notice that the objectivists here never actually make a detailed demonstration of their philosophy. They just tell people to go read some book. This leads me to believe that they are *unable* to make a detailed objectivist analysis of the topic (whether because nobody here really understands objectivism or objectivism is incapable of such an analysis I do not know).

Prove that you know what you are talking about. Make the argument here, dont appeal to outside sources.

[pi-r8]

/me ignores the debate on the axiom of existance and returns to the original question.

I'd suggest The Feynman Lectures on Physics for a good, rational introduction. They're very tough, but if you read slowly and carefully you'll learn a lot.

http://www.aynrand.org/site/News2?page=NewsArticle&id=7868

That article explains David Harriman's view on modern physics- he seems to be saying that nothing valid has been discovered since Einstein came along (!). Kind of a rediculous view, in my opinion, since there's solid evidence for a lot of modern physics which contradicts classical physics. I'm not aware of anything by Leonard Peikoff on the subject, but I would assume he holds similar views to Harriman.

[jrs]

Cole:

The gravitational field is everywhere, even in space devoid of matter.

The gravitational field is the same as the metric (distance or duration) property of space. This is explained in detail in "Gravitation" by Misner, Thorne, and Wheeler, published by W.H.Freeman and Company of San Francisco.

The distance from the Earth to the Moon can be measured by triangulation -- using the change in its apparent position as seen simultaneously from two separate points on Earth and trigonometry. Or it could be measured by sending a radio pulse or flash of light to the Moon and measuring how long it takes until you see the reflection.

What do you mean by "... I've always understood 'takes up space' to be an essential attribute of matter."?

Matter exists in space and it has extension (size). The Pauli exclusion principle prevents two electrons with the same spin from occupying the same space at the same time. Also atomic nuclei repel each other. This limits the extent to which atoms can share the same space.

Felipe:

You said "... it is entities that have finite qualities and quantities; and 'space' does not qualify as an entity. So, 'space' itself is not 'measurable' without reference to existents.".

False. Space also has measurable properties including size. But one must use objects to help delimit the interval to be measured and to either span the interval or send out the radiation which spans the interval. The difficulty is not that space lacks measure without objects, but rather that it has no distinguishable markings without objects in it.

pi-r8:

I agree with you that The Feynman Lectures on Physics are very good.

[HaloNoble6]

Space also has measurable properties including size.  But one must use objects to help delimit the interval to be measured and to either span the interval or send out the radiation which spans the interval.  The difficulty is not that space lacks measure without objects, but rather that it has no distinguishable markings without objects in it.

You're missing my point yet using it to call it false. "Space" has no quality or quantity as such. The only way the concept "space" or "nothing" makes any sense is with reference to "something." "Nothing" or "space" is strictly a relative concept, pertaining to the absence of some kind of concrete. This fact is true regardless of the unnecessary details you are discussing about radiation.

Let me just say that "existence exists" and its corollaries (such as the law of causality) do not specify the nature of existents as such, but it does specify constraints on the identities of "things that can exist." So, "existence exists" cannot be used to "prove" that the universe is expanding or shrinking or whatever, but it can tell you that a hypothesis such as "the universe contains singularities such as black holes" are false.