Nature Definition and 730 Threads

Are principal strains necessarily tensile/compressive or can they be shear strains also? And are the principal strain planes parallel to principal stress planes at a point?

I didn't get the concept of dual or hybrid nature of nabla? I-e vector differential operator .. Is it means that nabla can produce a vector from scalar field (gradient) and scalar from vector field(divergence) ? What's the concept of Nabla's Dual nature ? Please explain..

Hi all, I am from electronics background, yet I have studied quantum mechanics. Lately I have been reading Prigogine I., "From being to becoming". (If I am correct) the book deals with the one directional nature of time as it flows from past to present and onwards to future. But I did not get...

The world seems to me to be rather arbitrary. I don 't know if people feel the way I do. Scientists apply for government grants to gather data, and conduct experiments. Some scientists look at the data, and write down equations. If those equations are sufficiently fundamental, then some...

Hello forum, I'm new here. Please bear in mind I'm not a physicist, I'm sure you hear this a lot but anyway. I've recently taken an interest into quantum chemistry. So my question is the following: I understand electronic and nucleic wave functions are complex. When they are multiplied by...

Homework Statement Hi, I have been given a set of functions for which I need to find the stationary points , and determine whether the points are saddle, or max/min. I think I may have solved it correctly but I end up with all the points being saddle, surely this can't be right.. I may...

I've really never understood it. What's the logic behind having a journal/magazine having expert articles across all fields of science? Any person from a given field is only going to benefit from like 1 maybe 2 articles an issue and be completely clueless for all the other articles. How did...

I devised this using a setup that I found easiest to imagine, while trying to be clear on how modern physics considers space to expand. We have a nifty device that can cause spatial distortion (no, you cannot has one!). Before we use it, we lay down two meter rulers, end to end. They both...

In the documentary the Fabric of the Cosmos Leonard Susskind remarks how confused he is that a photon could be both a wave and a particle, he says a rock is a rock, and a wave is a wave (a picture of an ocean wave crashing). How could a rock be a wave? To me the answer is obvious, a wave is...

is it necessary that all crystalline solids are hydrated or hygroscopic. could anyone explain me the case of NACl and NA2CO3.10H2O?

why is light called an electromagnetic wave??what does it have to do with electricity and magnetism?

Hello all! In the past few months I've stumbled upon an issue that has played games with my mind. I feel I need some help to solve this, as I've tried various other sources and remain without answers. Firstly, I was confronted with a mathematical proof which states that 0.9~ (to infinity)...

Hi, fellow curious minds, I believe that human neuro structures are microscopic and thus within the realm of QM.From my basic physics knowledge, it seems to me that QM's probability interpretation of micro-phenomena is related to human volition. Every moment our consciousness are choosing...

Its my favourite function. \Large{\frac{sin(x)}{x}} I first saw it 1 year ago, when we studied limits. I don't know why, but I really like this function. Can anybody tell me an example, in nature where we have behaviour that has sinc function characteristics. Why am I asking this? Fourier...

Everyone seems preoccupied with the Big Bang and there are believers and non believers. I choose to look outside the box and understand The Nature Of The Universe... Are there any articles available on this subject?

Homework Statement What is the primary evidence that the Earth's outer core is fluid in nature? (2 marks) The Attempt at a Solution The Earth has a magnetic field which is created by molten iron that is moving. If there were a solid outer core, there would be no moving iron and no...

Hi all, My Physics tutor's reasoning for no well-defined energies existing in nature for a system in time was that if a system had a well defined energy in time, such that |psi> = |E0> then, evidently, the energy cannot vary. And, his logic goes on to say that if an energy cannot vary, you...

Nature of "Real" Applications Quantum Mechanics I've heard of several applications of quantum mechanics such as atomic clocks, transistors, lasers, etc. I understand how we need quantum mechanics to understand what's going on, but how exactly is quantum mechanics used in any sort of "real...

Homework Statement The equation kx2 - 3x + (k+2) = 0 has two distinct real roots. Find the set of possible values of k. Homework Equations Since the equation has two distinct real roots, b2 - 4ac > 0 The Attempt at a Solution b2-4ac>0 9-4(k+2)(k)>0 9-4(k2+2k) >0 9-4k2-8k>0 =...

I am having trouble understanding how special relativity reconciles the concept of causality. In one frame of reference event A may be followed by event B, but in another frame of reference event B may occur before event A. In the first frame of reference an observer may claim that event A...

I have recently learned about the double slit experiments using electrons and photons. This has completely blown my mind and I want to learn more. With this aim I have a question that I hope somebody on here can answer. For this question I want to consider the use of electrons in the double...

if there is dark matter every where, why it is noticed near galaxies? why can't we do some very sensitive lab experiments of gravity to find the effect of dark matter?

Finding the critical point and its nature. With solid attempt! Homework Statement Find all critical points of the function f(x, y) = xy2 - 2xy - 2x2 - 3x +7 and determine their nature. Homework Equations none The Attempt at a Solution I know that to find the critical points you must...

1.) does a stationary charge in a gravitational field radiate (as per the principle of equivalence)? 2.) why have we been advancing from seemingly less intelligent species to a more intelligent one? what is its physical significance (besides intelligence corresponding to complexity) ? why do...

Are springs manufactured to obey Hooke's law, or do all springs just naturally obey this property?

The other day, as I was struggling through my quantum mechanics text, I realized that the only physical laws presented in the text were the four postulates of QM, the last of which is Schrodinger's equation. These are presented around page 150. The first 150 pages establish the background needed...

why do fundamental forces of nature exist? Is it to attain a state of equilibrium? For e.g. is a positive charge is attracted to a negative charge to attain a state of equilibrium? Then why do forces like gravity, strong force, weak force exist?

I have a question of sorts. I was taught that the universe formed from the Big Bang, which was a unique event. Much later I learned about the hypothesis of a multiverse, and the prospect that the Big Bang and our universe might not be as unique. This has off course has yet to be proven. Later...

Physicist Benjamin Crowell has released several open-source textbooks on physics and mathematics; one of them being http://lightandmatter.com/area1sn.html" . I have decided to study physics on my own in my spare time and Simple Nature seems to be quite sufficient; at least as an introductory...

With the last year or so I came across a great discussion in these forums about the different types of infinity. It had never occurred to me there would necessarily be different types with different "values". How about zero? Are there different mathematical concepts regarding it or are all...

Alright, I have an LC circuit. Using conservation of energy, I get \frac{dI}{dt}= \frac{-q}{CL} which gives \frac{d^2q}{dt^2}= \frac{-q}{CL}, therefore, q=q_o sin(\omega t +\phi), where \omega= \frac{1}{\sqrt {LC}}, giving q=q_o cos(\omega t) which implies I= -q_o \omega sin(\omega t). Now...

Let’ say; “A” can see and measure a stone falls to the Earth let’s say 10 meter per 1 Earth-second. “B” lives at Mercury and can see the same thing. But “B” would do not see the exactly the same, because seen from “B’s” viewpoint time / distance is not the same as for “A”. Let us say...

Hi all - I have a few questions. Well, one, actually. So I have about 10 years (2000-2010) worth of hardcopy Science, Nature, and Nature Medicine journals, each. I was thinking of selling these, but I'm not sure if there is a market for them. I have been checking ebay for a while and I don't...

Has anybody seen http://www.nature.com/nature/journal/v477/n7362/full/477005b.html"? I can't believe that a journal like nature is condoning the idea that unreasonable working hours for researchers are ok because that's just how things are going. What are some others' opinions on this article?

Hi, I am trying to understand whether quantum theory provides any sort of physical interpretation of matter waves. So far, I have been attempting to work my through some of the developments, but possibly failing to grasp what appear to be some fairly fundamental issues. Therefore, I was hoping...

Hello, was wondering a couple of details on the wave nature of electrons and the state of the art in this field. In particular: Is it practical and possible (easily) to create a cm sized electron interference pattern (fringes are in the cm size magnitude). I have so far seen Low Energy...

Homework Statement Light propagates as waves, but exchanges energy as particles Homework Equations I don't understand the second part, i.e., light exchanges energy as particle. I need the help of members in this regard The Attempt at a Solution

There's a saying that nature abhors a straight line. It's not totally true because crystals have straight lines. One thing I don't recall seeing in nature is a knot. Is there an example of a knot in nature? Does nature abhor a knot?

Hi, Wate ripples closely resemble sinusoidal waves which means sine waves exist in nature. Do square, sawtooth and triangular waves exist in nature, or, have they been invented for their special characteristics? Help me, please. Thanks Cheers,

Hi, I am studying for my Analysis final and came across this problem I just can't get my head around: Homework Statement Find the critical points of f(x,y) = (x^2+y^2-4)(x+y) and their nature. Homework Equations \vec{\nabla} f(x,y) = \vec{0} The Attempt at a Solution \frac{\partial...

It seems to me that there is a difference between, say, the law of conservation of linear momentum or energy and the law of conservation of angular momentum. The first two are valid in any frame of reference and their invariance is a direct consequence of the relativity principle, whereas...

Homework Statement I had the following question in my chemistry book... A mass spectrum of Br2 has three peaks, with the mass numbers 158, 160, and 162. Use this information to determine which isotopes of Bromine occur in nature. Homework Equations The Attempt at a Solution...

Hi, Does anybody know where I could download a latex template for the magazine Nature Physics? or Nature ? Thank you all.

by undefined do we mean 1 or 2 below? 1. we don't know the polarization (but it must be having some value of the spin) or 2. the photon does not have a definite spin yet mixed polarization means: a mixture of defined spins? (up or down, right or left etc) once a polarizer has defined a spin...

There have been a number of very interesting posts lately around the nature of light. So I devised a simple thought experiment to try and understand it a bit more. Say John and I are next to each other in rocket ships, at rest wrt to Jane, who is 1 light minute away in her rocket ship. All...

While studying the Doppler effect at school, it struck me as strange that the following two problems have different solutions: a) you are moving at 40 m/s toward a source that is making a sound with a frequency of 1000 Hz. What frequency do you hear? (speed of sound= 340 m/s) b) The...

I was thinking a bit about gravity. As is known, Physicists have yet been unable to unify the Theory of Relativity (describing gravity) and Quantum Theory (decribing the other three fundamental forces). As mass is a measure of a system's energy, the force of gravity (presumably carried by...

What drives particle decay? Is it an elementary, irreducible observation or can we model it based on a set of observable variables? Do all particle decay modes involve the weak force? Does one even need the intervention of a given force to have particle decay? Does string theory explain...

I've recently read a paper which suggested some properties of vortex's, which I could not confirm in my elementary physics textbooks or during a quick google search. I hope to find some evidence that: All vortex phenomena are actually composed of two vortex's: 1 - An outer vortex which...

I've recently been researching Argentinian Electroneurobiology. It seems to be an old tradition, based on clinical research. Now I posted specific questions related to the physics used to underpin this view in the quantum subforum, but regrettably the thread was locked (probably because this is...