User talk:StuTheSheep

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Hi, you can call me StuTheSheep, or Stu for short. My interests are wide-ranging, but are mostly focused on science, particularly physics, and history. I've been using Wikipedia as a resource since about November 2004, and began adding and editing in February 2005.

Contents 1 Wikipedia:Category 2 Principle of relativity 3 AfD aka VfD on Philosophical interpretation of classical physics 4 Total re-write of the main Physics page is in progess

[edit] Wikipedia:Category

See Category talk:Physics#How to add categories to the physics articles:

You are free to restore the notice on the category:physics page if the additions did not address your concern. I merely commented out the notice. Ancheta Wis 11:50, 23 Mar 2005 (UTC)

[edit] Principle of relativity

Since you wrote the article on the subject, I have a question I want to ask you. My understanding of the principle of relativity is that (among other things) it requires the laws of physics to be the same in all frames of reference. I want to be sure that this is absolutely true, or if it is only true for inertial frames. The reason I ask is because I linked the frames of reference page to the principle of relativity page. StuTheSheep 16:55, Mar 1, 2005 (UTC)

Hi Stu,

It is important to appreciate the distinction between properties of the way laws are formulated and properties of physics itself. The two are closely connected, but they are not exactly the same.

In terms of pure properties of physics: it's only in inertial frames that the physics is the same everywhere. When a force is accelerating an object (for example an accelerometer) then there is acceleration with respect to inertial motion. Without going into symmetry and non-symmetry now, suffce it to say that velocity is fundamentally relative, but acceleration is absolute with respect to the inertial reference frames.

A 'frame of reference' is of course a human abstract thought, it is not a physics phenomenon. Very often people find it easier to formulate ideas in terms of properties of 'frames of reference'. What has crept in, I think. is that sometimes people assign a status of being a physics thing, to a frame of reference. I think it is a good exercise (and a measure of physics understanding) to try and phrase a dynamics phenomenon in such a way that the expression 'frame of reference' is not used.

Using a high level of mathematical abstraction, it is possible to formulate for example Newton's laws of motion in such a way that the formulation is the same in all reference frames including rotating and otherwise accelerating frames. That would be a unnecessarily tedious formulation to use, but it is possible. This is called 'covariance'. However, covariance is a property of the formulation of the law(s) of physics, this property doesn't necessarily describe a property of nature. --Cleon Teunissen 21:36, 1 Mar 2005 (UTC)

The measurements that an observer makes about a system generally depend on the observer's velocity relative to that system. Every relative velocity corresponds with a particular set of measurements. Each set of measurements can be used as input for calculations, and each set of measurements shows that the same laws of motion hold. Only the group of measurement sets done by observers that are in inertial motion with respect to the system that is being measured share this property.

An observer in circular motion needs to adjust for that when performing calcultations. This adjustment always refers to an inertial reference frame, for the laws of motion only hold good in inertial reference frames. --Cleon Teunissen 22:26, 1 Mar 2005 (UTC)

Thank you for clearing that up for me. StuTheSheep 05:40, Mar 3, 2005 (UTC)

I cannot resist adding some remarks. As I write in the current 'principle of relativity' article: in general relativity the description of gravity and of inertia are unified into a theory of geometro-dynamics. In geometro-dynamics, inertia is not described as a property of objects, but as a property of the interaction of matter with space-time geometry. I think the following interpretation is very interesting: by flying apart, the matter in the universe is creating the volume of space-time. Chunks of matter are interacting with their local space-time. With space-time acting as mediator across vast stretches of time, chunks of matter are interacting with all of the matter in the universe, and thus they have the inertia they have. (Mind you, that is an interpretation of what the mathematics of general relativity might mean.)

Spinning gyroscopes maintain their alignment, if they are suspended sufficiently frictionless. Effectively, spinning gyroscopes take an astronomical measurement. As they are being spun up, they 'lock on' to the orientation they happen to point to at that particular moment. Shifting the orientation of this 'locking on' requires a force. For an observer in a module who is confined to local measurement there is very little possibility of detecting a difference between being accelerated by a force in a straight line or gravity being opposed by a force. But rotation of the module can be measured locally in a number of ways, among them monitoring a frictionfree suspended spinning gyroscope. See also Gravity Probe B and frame dragging --Cleon Teunissen 10:26, 3 Mar 2005 (UTC)

[edit] AfD aka VfD on Philosophical interpretation of classical physics

We could use your opinion on this article at Wikipedia:Articles for deletion/Philosophical interpretation of classical physics

I have nominated as original research but feel that it is important to solicit additional opinions on the matter before an administrator is forced to make a decision. As I mention in the discussion on the [[AfD page - I think the underlying idea - to discuss the impact of classical Newtonian physics has had on other discpiplines and the impact that QM should (but in many cases has not fully) had on those same disciplines - is an interesting one; however, I need help in determining if existing article should be the starting point for such a discussion (or if this topic is covered elsewhere). Thx in adv -Trödel|talk 10:30, 2 November 2005 (UTC)

[edit] Total re-write of the main Physics page is in progess

You might like to join us at Physics/wip where a total re-write of the main Physics page is in progess. At present we're discussing the lead paragraphs for the new version, and how Physics should be defined. I've posted here because you are on the Physics Project participant list. --MichaelMaggs 08:04, 11 October 2006 (UTC)