I Am So Confused...

jnorman

hello all - i have spent 25 years or so as a layperson very interested in many aspects of physics, and have done considerable reading of both professional and lay-level materials about quantum reality (from QED to in search of schroedinger's cat, from the nature of space and time (hawking was completely unintelligible) to gravitation (MTW)). a few years ago, i got so confused and disheartened about my inability to understand ANYTHING at all about reailty, i just turned to other subjects for a while. but the nature of reality is a siren whose song is hard to resist.

for example, considering that an electron is a point particle and occupies no volume, and the same for quarks, does this imply that everything we think of as "real" (matter) is not a real thing at all? ie, when you get right down to it, there is not any "thing" there.

or, particle interaction vs fields - i have never read or heard any kind of an explanation of what a "field" actually is (other than equations, or some non-intuitive definition like "a domain wherein...") - what the hell is a field? how does a field communicate its existence? are particles manifestations of fields? virtual particles? who thought that little nightmare up?

or gravity - geez! or time, or light, or magnetism - what are these things? i feel like i really dont understand anything at all...

OTOH, one of my favorite quotes has always been, "if you are not confused, you are probably wrong."

so, you ask, what was the question? can anyone suggest some good reading for me a this point? maybe penrose's new book? thanks.

Bjørn Bæverfjord

In the book Road to Reality Penrose tries to give some ideas on how to go about to solve your problem. Roger Penrose is a very good writer and I am sure that some of the book will make sense to you and might even be enjoyable but most of the 1000 pages will probably be very difficult for you to digest since it contains some very advanced math and theories.

The theories you mention are attempts to make sense of what we observe, it is done by using math since it is the only tool that seems to give a reliable result. None of them relates directly to reality, they only try to mimic reality as closely as possible while at the same time be mathematically consistent.

Since these are mathematical theories then there is usually several possible ways of explaining the same thing and sometimes several ways to imagine how this works in reality.

There are also many philosophical problems to come to grips with. For example it is doubtful that your perception of reality relates very accurately to reality itself.

I think that some of your confusion comes from trying to understand something that no one understands and some from your lack of detailed knowledge. Try focusing on one particular area and learn enough about it for you to see that there is no direct link to reality.

pmb_phy

jnorman - Hey dude! Long time no hear! How's it going?

Pete

marlon

very good question. Scroll down to the 'why do we need field' entry of my journal on this link : http://www.physicsforums.com/journal...page=10&page=6

regards
marlon

ps : browse through my journal. there are many texts on virtual particles too

caribou

Murray Gell-Mann's book The Quark and the Jaguar gives lots of great little explanations of fundamental physics around the middle of the book.

Gell-Mann was a dominant force in particle physics for a couple of decades. Quarks, Quantum Chromodynamics, The Eightfold Way, etc. have those names because that's the names he gave them.

You can be sure he knows what he's talking about.

marlon

That is not really accurate. A quantumfield can be interpreted as a mattress that is built out of many interconnected springs. If you put an object on that mattress, it will start to vibrate. These vibrations each have a certain energy and momentum. Well, in QFT, it are these vibrations that represent a particle of certain energy and certain momentum.

When you put two massive lumps on the mattress, it will start to vibrate. This vibration really represents a particle that moves from one lump to the other. When you calculate the energy, you will find that it corresponds to an attractive force. The revelation really is that forces can be represented by the exchange of particles (ie the vibrations of the quantumfield (or the mattress, if you will)).

regards
marlon

James R

jnorman:

The "thing" has measurable effects on things around it, so there must be something there, even if it has no measureable size.

A field is really just a collection of values of some quantity for the whole of space. For example, you might talk about the "temperature field" in your lounge room. At every point in your lounge room, you could measure the temperature. The collection of results would be the temperature field. Another way to say this is that the value of the temperature field at some particular point in your lounge room is the value of the temperature you would measure there.

More abstract things such as electric fields are the same. At every point in your lounge room, you could, in principle, measure the strength of the electric field (e.g. by putting a charged object at that point and seeing how it moved). The only slight difference between an electric field and the temperature field I talked about before is that the electric field also has a direction at every point in your loungeroom, whereas the temperature at any point is just a number. In technical terms, we say the electric field is a vector field, and the temperature field is a scalar field.

It doesn't, unless you allow it to act on something which you can measure. The electric field in your room, for example, is doing all kinds of things. If you get a radio receiver, you can pick up some of the fluctuations in the electric field (e.g. by tuning in to a radio station). But most of the time, you're completely oblivious to the field.

In quantum field theory, particles are described as disturbances in special quantum fields.

This is really a philosophical question. From one point of view, something like an electric field is just a convenient fiction which is invented to explain how one measureable thing acts on another measureable thing. But other people will tell you that fields have a kind of reality of their own (again, because they have visible effects).

jnorman

thanks for all the comments. i will give penrose's new book a try.

pmb - nice to see you are still around. hope you are well. i still miss the halcyon days of dr neutrino...

dx

You might also want to read some of Einstein's essays on fields, you can find them in 'Ideas and Opinions'.

taurus_gtm

i want to learn about 4 dimensional world
can anyone suggest me plz?

marlon

go study differential geometry and general relativity.

marlon

caribou

I guess you mean special relativity's spacetime?

Here's a free introductory book by Albert Einstein:

http://www.bartleby.com/173/

Some more information and links here:

http://en.wikipedia.org/wiki/Special_relativity