This may be a silly question displaying only my ignorance on the subject. My question has to do with point-particles and spatiality. Physicists say that point particles have causal powers, i.e. photons striking someone’s eyes at certain wavelengths cause them to see. Perhaps photons are only contributory causes to one’s seeing. Physicists also say point particles are objects that are both concrete and physical. That is, they can be located in space which entails they are spatial objects too. However, by definition a point-particle lacks width, length, and depth, the three spatial dimensions. My question is how can this be? Is this a conceptual incoherence, or am I missing something? Does spatiality entail physicality or conversely, does physicality entail spatiality? Alternatively, is it that these two concepts have no intimate connection? Please explain. Thanks.

Is the universe infinite? And if it isn't, what is outside it? Are there lots of universes, or is it all just fractals? And what about other dimensions? Is it possible that time and laws of physics work differently in other universes? Helen from Worcester, age 12

If having two dimensions, height and width, means that a diagonal line is just a tiny line up connected to a tiny line across, repeated on a level so small we don't notice and the line appears diagonal, does that mean that everything in our 3D world is almost 'pixelated' at a really microscopic level? Sorry, I'm having problems describing what I mean but see if you can make any sense of that. =) Thanks.

Hello, I wonder how laws of physics, mathematics and logic influence each other. What I mean is the following: In Quantum Mechanics (probably even in general physics), only very few non-linear problems can be explicitly solved. The most important ones are 1.the harmonic oscillator (potential r^2) and 2. the Hydrogen atom (potential 1/r). This is the reason why almost any other non-linear problem is first reduced to a r^2 or 1/r-potential problem. This seems like lucky coincidence or a divine act or whatever you might call it: 2 very basic physical problems can be expressed and solved in a very basic mathematical way. Now I keep on wondering: If our mathematics was based on some different algebra than the one it actually is, say, elliptic functions (=objects that are reasonably hard to express in "our" mathematics), would our understanding of physics be different? (For example: would we better understand physical facts that are now "too complicated" (because of their mathematical complexity), and ...

I read all the questions and responses related to determinism, quantum mechanics and chaos theory that you have posted, but I am still unclear exactly how they relate. Supposedly, quantum mechanics and chaos theory refute any hard case for determinism, but I am still unclear as to how. Could anyone add to this or suggest some reading on the subject?

Could a newly discovered law of physics ever change/affect a law of logic?

Did Einstein ever engage the "scientific method" of empirical investigation in the course of his work on special and general relativity; and if not, wasn't he more a philosopher of science (albeit an exceptionally productive and influential one) than a scientist? If Einstein simply engaged in a priori reasoning and conceptual analysis (using his famous thought-experiments) then I don't see why the physics community has any more claim to him than the philosophical community. After all, it seems that his methodolgy bore a much stronger resemblance to that of contemporary philosophical efforts than it does to anything going on in or commonly associated with physics departments. -Will Leonard

Do computers defy the law of conservation of mass? Because, if a computer can copy a program there is twice the amount of space taken up. But how can you just duplicate an amount of space (MB, KB, GB,etc.) if you add nothing to it?

Quantum behaviour says that before a phenomenon is observed there may be a number of possible outcomes. Once observed, the number of possible outcomes becomes one; what actually happened? Surely the present moment consists of an infinity of phenomena which, with the benefit of Quantum hindsight, may be seen to have *actually* been certainties. Uncertainty exists only in the mind of an imperfect observer; there’s no such thing as foresight outside of a limited, dry mathematical framework. This leads me to think the following; i) That everything is as it is because it could not possibly have been any other way. ii) All the things in the universe whose extremely improbable existence we marvel at and things which everything else depend on who, if they were any other way, lots of other things wouldn’t work either, were actually (in retrospect), absolute certainties. Is this a gross misunderstanding of Quantum theory, an obvious conclusion, or a line of thinking with some mileage? I can see it leading...

Is it possible to determine whether the laws of Physics as they are currently perceived will last indefinitely? Is there anything to prevent the nature of the universe changing so much tomorrow that reality as we know it breaks down?