Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I may be totally off with this quite abstract (?) question(s).

But still, here are some closely related sub-questions:

  • Is there a list of currently "known" intrinsic properties of nature?
  • How exactly is an intrinsic property of nature defined? Is it defined as "it is so, because it is so" or "it is so, because it cannot be otherwise (in our Universe)"?

For example, Wikipedia about mass as intrinsic property:

An intrinsic property is a property that an object or a thing has of itself, independently of other things, including its context. An extrinsic (or relational) property is a property that depends on a thing's relationship with other things. For example, mass is an intrinsic property of any physical object.

Is this a correct explanation of an intrinsic property?

share|cite|improve this question

closed as off-topic by Ben Crowell, Emilio Pisanty, Chris White, Waffle's Crazy Peanut, Manishearth Sep 14 '13 at 19:33

  • This question does not appear to be about physics within the scope defined in the help center.
If this question can be reworded to fit the rules in the help center, please edit the question.

I think this question would better suited to philosophy.SE. Applying this definition to nature itself would mean discussing whether or not nature's properties exist in relation to things that are outside of nature, e.g., the soul or Platonic ideals. – Ben Crowell Sep 12 '13 at 19:24
This question appears to be off-topic because it is about philosophy, belongs on philosophy.SE. – Ben Crowell Sep 12 '13 at 19:26
@BenCrowell I am wondering. It seems a good opportunity to explain that invariance is not just a collection of mathematical tricks to build beautiful theories, but that it is actually the central concept that makes science meaningful. It is probably most visible in physics. However I do not think I would equate invariant and intrinsic. – babou Sep 12 '13 at 21:07

The idea is correct.

From my point of view, a more precise definition of intrinsic physical reality, is a physical quantity which does not depend on the observer.

For instance, different observers can observe the same particle, and they will find the same mass for this particle. This is not true, of course, for the momentum/energy of the particle. The mass does not depend on the observer, this is an intrinsic characteristic of the particle.

So, intrinsic physical quantities are observer-invariants.

share|cite|improve this answer

Your second question may be answered so, from the anthropic principle. Things are the way they are because if it would've been any different, we wouldn't have been here to ask this question. This is only a principle and tries to explain the seeming compatibility of intrinsic properties to facilitate life and consciousness. So, the argument is, if the mass of the proton, neutron or the electron (or indeed even subatomic particles) was any different than what it is now, they wouldn't have formed atoms which formed molecules which later formed the building blocks of life all the way to the organism.

share|cite|improve this answer
You might like to point out that the anthropic principle is often questioned or confined to very sparing use, because it tends to make a theory unfalsifiable if you just hang all the loose ends on "oh well, we wouldn't be here if it weren't like this". I'm not saying that this is not valid sometimes: some things may be like this, but the principle tends to shut down enquiry beyond the limit it marks, so many workers - Roger Penrose for one- think of it as an absolutely last resort. But +1 for a great concise description for the OP: it will help them if they've not come across this idea before. – WetSavannaAnimal aka Rod Vance Sep 13 '13 at 2:24

I don't think my answer is appropriate for this site because I have to begin by saying "in my opinion"... :)

Physics is a mathematical science and mathematics is relational. By that I mean a quantity does not have meaning by itself, there is no Kantian thing-in-itself in mathematics. If I say $A$ and $B$ that is, by itself, meaningless, but if I say $A=B$ then I have established some mathematical relation which has meaning in the mathematical sense. This type of understanding, together with logic, forms mathematics. Physics, similarly, establishes relations between quantities with the addition that those quantities are physically measurable. They also acquire meaning through experimental observation. As physics progresses we see some quantities are deeper than others, also relations are found which render entire sets of quantities redundant (i.e., they may be viewed as following from one quantity). This is reductionism and it is a philosophical approach which served physics well.

In other words, there are no intrinsic properties in nature, only deeper and less deep quantities. One day it is likely we will find one deep property from which everything will follow (maybe vibrational modes of a string, I don't know).

share|cite|improve this answer

If nature is supposed to encompass the whole universe, there can be no extrinsic property of nature.

Now, regarding whether physics explains (intrinsic) properties of nature, I think one has to be careful about the meaning of words. Science is not supposed to explain: that is the role of religion or possibly philosophy. Science is supposed to describe nature, and relations between aspects of nature that are measurable in some way, and that remain invariant in ways to be established.

This invariance is what makes the scientific description valuable, as the knowledge of the relations can be used to predict future evolution of natural phenomena from initial data (more precisely from boundary data).

As we integrate these descriptions in our thought processes, we tend to perceive the more accepted ones as natural truth from which other truth can be explained by the relations that were identified. But this is a dangerous bias, that can also prevent us from making deeper observation that would contradict it.

Science organizes knowledge of nature, it does not explain it. That is true of physics, but also or other sciences.

Of course, we commonly say that this law of physics explains such and such phenomenon. But that is colloquial language to indicate the existence of a relation that given some observed hypothesis will lead to the observed conclusion. Because of the invariance.

Now, what is a property of nature? What exists? I am not sure the question has meaning. Probably anything that can be observed, preferably measured, and put in relation with other such things. Since they are in relation, it may be that given the density of relations (say "equations") some of these concepts/things/properties (say variables) are redundant, as they can be deduced from others. But we do not have to agree on which are. It is often in the eyes of the beholder, or the instruments of the scientist. And it is also often a matter of scale, or of precision, or a matter of simplicity. Some views may be simpler in some cases, and more complex in others.

People dismiss old physical theories too easily. Geocentricity of the universe is a perfectly good theory when you know its domain of application, such as running the ocean. It certainly does not work as well to explain peculiarities of Mercury. So, what is nature ?

However, if physics does not explain, mathematics can provide some explanation. Mathematics is often considered as outside, beyond nature, though that may also be questionned in some precise sense. Physical phenomena are describable by mathematical relations, that have to obey the laws of the corresponding mathematical theories, if the description is supposed to be adequate. Then the consistency of mathematics may impose other relations that must be observable, if the theory is not to be questionned. So some natural phenomena, or some properties of natural elements (as much as make sense, as said above) may be explained by mathematical consistency, assuming that other phenomena are considered part of reality as described.

share|cite|improve this answer

Not the answer you're looking for? Browse other questions tagged or ask your own question.