6 posts tagged “physics”
This book is a useful introductory conceptual explanation of major principles/theories/laws in physics. It also expounds on physics' relationship to other sciences, which is very interesting. The amazing hallmark of this book is its clarity in concepts.
For example, even though I had taken AP Biology I had very little understanding of what an enzyme actually is [ie. how one substance is an "enzyme" and another is not]. All I could glean from the rather obtuse descriptions/explanations/examples of them that I was given, is that an enzyme is a large molecule which is involved someway in most organic reactions. How they were involved specifically eluded me. While not terribly important, it was still a bit of a puzzle until Feynman clarified that an enzyme is molecule which catalyzes, but doesn't react in, organic reactions by physically manipulating the reactants into reactable positions. And he does so by starting from physics and the nature of atoms.
In short, if you're starting a study in most any scientific field, this is a good and quick [only took me 2 days to read casually] place to establish a context and clarify some of the concepts you will use.
My biggest misunderstanding of physics:
If a photon and a graviton have no mass or charge [and by the way what does it mean for a particle to have no mass?] then what is the philosophical difference between either one of those "particles" carrying electromagnetic/gravitational force and nothing carrying it [ie. action at a distance]? If nothing can be detected to occur between particles interacting, then why is it necessary to say that there is something? What makes physicists think there is anything there?
I just accidentally discovered the strangest phenomenon, and I don't know what it is!
So here's the set-up: go into a completely dark place [a bathroom, midnight with no lights on] then peel apart the two sheets of paper that contains a band-aid or a Breathright strip. Notice that where the two papers meet there is a flash of bluish light! My tentative guess is that it is a high amount of friction produced evenly and quickly which makes the light, but band-aids litter my apartment and I must know what it is! Internet, ho!
If anyone has any ideas please share.
The problem with that is that if this were entirely accurate, a single lipid should move randomly at a certain speed. After tagging a single lipid with a photoluminescer and watching its progress, they find it moves at about a fifth of the speed expected. Also, in such a model, the cell wouldn't be able to efficiently localize information. He gave the example of nerve cells that have definite outgoing and ingoing regions, if the lipids and proteins move freely/randomly about one another, then the cell could not have the specified regions of receptor proteins (they would be mixed randomly).
This is what professor Ritchie says, the cytoskeletal filaments are right below the membrane and proteins are anchored to the structure. These proteins stick up inside (sometimes through) the membrane and cause what he calls "fences". A lipid is free to move within any of these little areas, but it takes some time for it to get through/around the fence. I didn't ask if all proteins are anchored to the actin, but knowing generally how a cell works, I'd say that the proteins which are advantageous to be localized are anchored and the ones that need to move aren't. Which explains how a nerve cell can partition one branch for ingoing and another for outgoing proteins.
While taking physics classes I learn quite a few derivations and formulas, but curiously little in the big-picture-conceptual sense . Lately I've been trying to answer this basic question: what are electric/magnetic fields, what in the actual world does this concept represent? This is my current understanding.
Matter interacts with other matter in various ways. One way in which it does so is by charge, charge being an attribute of matter analogous to mass. There are two types of charge which produce opposite effects. They are therefore said to be 'opposite' charges and assigned the arbitrary value of positive and negative. Matter that interacts by virtue of its charge is said to do so electrically, and when charged matter is moving it also interacts magnetically.
In these interactions the charged matter applies equal and opposite force on one another. An electric field is a map of predictions of how this force will be applied to any other charge given a certain degree of charge of a particle; a magnetic field is this set of predictions for moving particles.
Particles only interact magnetically when all the concerned particles have a magnetic field, ie. are charged and moving. One particle will not act magnetically while the another acts electrically, or not at all, or in any other manner. To illustrate this point, consider a static charged particle and a passing charged particle. The static particle has an electric field, the passing particle has both an electric field and a magnetic field. The particles will interact equal and oppositely depending upon charge (attraction or repulsion), causing the static particle to move (thus a magnetic field) and the passing particle to shift in it's motion. They will then begin to act magnetically.
An important thing to note is that since the magnetic interaction of particles is dependant on their velocities, and velocity is relative to the reference frame of observation, magnetic fields are relative. This means that how one observes the interaction is dependent upon the context in which one views it; it does not look the same from every point of view.
I have been trying to figure out what exactly is meant by the term electric field. This is what I think so far:
A net/matrix of predictions over distance of the force exerted on a hypothetical particle, P2, by a particle, P1.
This is how my textbook (Matter and Interactions v.2 e.1.5 by Chabay) defines an electric field: Force2 (vector) = charge2 * electric field1 (vector)
Any thoughts; what is an electric field?
Comments Posted to Original Blog
- Amanda Carlson said...
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There's only one more thing I don't quite like about my definition. It assumes that charges as such interact, when in fact the matter is interacting by virtue of it's attribute charge. It also, isn't completely clear in it's genus
So, the revised definition is:
A map of predictions depicting how an object of any charge will interact with an object of a given charge.
~Amanda
I've refined and clarified my definition of an electric field:
A map predicting how any charge will interact with a given charge.~Amanda
Monday, February 20, 2006 2:11:00 AM