Nature Definition and 712 Threads

Sharks are extremely sensitive to magnetic fields, attracted by low end frequencies and repelled or overstimulated by higher/stronger fields. I want to map the spectrum in between using and electromagnetic coil in the water with sharks. I have sharks and a boat but need help building the coil...

Does the nature of radiation emitted by dense bodies like black holes differ in frequency from radiation emitted by regular stars like our Sun ? I believe that the former radiates more x-rays and high frequencies rather than the latter which radiates mainly uv, visible and infrared ranges. Is...

So having considered the classical depiction of a black hole resembling a whirlpool, my thought process is that a black hole must be a 3-d phenomenon. Therefore I can not see how a event horizon/swirlpool model could be plausible unless the centre of a black hole was spinning and literally was...

Dr. Achim Rosch, a theoretical physicist at the University of Cologne in Germany, who proposed the technique used by Dr. Ulrich Schneider and his team to create in laboratory negative absolute temperature, have calculated that whereas clouds of atoms would normally be pulled downwards by...

Hi everyone. I'm not sure if this should fall under Biology and Medical, or under some other science category, but I found the following news link from the Santa Fe Institute (SFI) website, about analysis by physicist and complex systems researcher David Wolpert, which suggest that imprecise...

Is it right to say that 'modern physics has no deep explanation of the nature of charge' in electrons and protons?

It's mentioned in my book that blackbody radiation can verify the particle nature of electron could anyone explain this to me,please?

Does randomness exist in nature? We say every event must abide by the laws of nature, including QM probability/uncertainty. QM says outcomes are uncertain. Does uncertainty imply both randomness and probability? It seems that randomness is superfluous to the uncertainty principle, and it makes...

I learned that the moment a wavefunction collapse takes place is a matter of interpretation. So, I suppose the phenomenon 'wavefuntion collapse' is something that has to be witnessed by observation at some point to be able to establish it at all! So my question is: if collapse doesn't actually...

Hello. Modern Physics explains Gravitation in two general ways: In accordance to the General Theory of Relativity, Gravitation is thought of as an effect of the curvature of space-time continuum. This results in the formation of the recently and famously detected Gravitational Waves. Quantum...

The following question/thought experiment is based on the dual nature (particle/wave) of electromagnetic radiation. Consider the emisson of a single photon on a 3D grid along the x-axis with its origin at (0,0,0). The only matter in this experiment consists of “electrons” found only in...

I have a problem with understanding the nature of collisions and their outcomes. From my understanding, I come to think that when a mass collides with another, both of them should always have equal velocities post-collision. For example, when a mass moving at v1, m1, collides with a mass at...

Conserved quantities in GR deal with ##p_\mu## not ##p^\mu## and while in Minkowski spacetime its easy to see what each of the components mean (since the metric is so simple) in general relativity I think its not and its starting to confuse me. Why exactly is ##-p_0## the energy in general...

When a "layman" hears of the cosmic microwave background, and this layman also has a passing knowledge of big bang theory, it can be difficult for said layman to wrap his head around what the CMB really is. That layman might ask, wouldn't this primordial radiation have "passed" us by now, and...

I'm wondering if time is just a way we have to "measure" how things change its characteristics in space. Is that correct?

Hi, I'm trying to conceptualize the life of a particle as it travels through free space. I wish to start simple and then build from there. Speaking about the wave-particle duality that we observe in fundamental particles. Let's start with electromagnetic radiation (then move on to...

I understand that we can create entangled particles in the lab. But how many (non-locally) entangled particles (such as photons/polarisation or electrons/spin) exist in free nature?

what is electric current...a scaler or vector?? ...well I personally believe that it is somewhere in between the two extremes (what is not 0,need not be an 1 either :oldbiggrin: ) ...particularly because of the strange similarity we see in vector addition and phasor addition)...some people...

What happens to a mechanical force's real original direction i.e. when we divide it into components of basis vectors, which in turn change as per problem at hand (like gravity components at inclined plane ), how we arrive at correct physics by taking two/three arbitrary directions of our choice...

Dear Friends! I am learning Tensors so my question may look simple to you. "All observers in all reference frames agree not on the basis vectors not on the components but on the combination of components and basis vectors" Q Why this happens? Please guide me where I can study it in brief and in...

Hey everyone, I am currently in the middle of research for a science fiction /fantasy novel where the magic system is based on the ability of a group of people to manipulate the four fundamental forces of physics. Of these four, coming up with ways that individuals could manipulate gravity and...

Homework Statement A gas in equilibrium has distribution function: f(p,r) = C0*(1+y*x)(2*pi*m*k*T)-3/2*exp(-p2/(2*m*k*T)) where x is the distance along an axis with fixed origin, and y is a constant. What's the nature of the force acting on this gas? Homework Equations Maxwell bolztmann...

My simple description of gravitational waves is that they are due to the relativistic principle of locality, i.e. the fact that the action of gravity is not instantaneous, something that you can’t see from the tidal effects in Newtonian physics. Is it correct? I've also found a comment...

If $f(x)$ is a differentiable real valued function satisfying $f''(x)-3f'(x)>3\;\forall x \geq 0$and $f'''(x)>0\;\forall x\geq 0$ and $f'(0)=-1\;,$ Then $f(x)+x\;\forall x>0$ is $\bf{Options}:$ $(a)\;$ decreasing function $(b)\;$ Increasing function $(b)\;$ Constant function $(d)\;\;$...

My question is about how new ideas come into being. Are all new ideas based on some form of predictive analysis or can they arrive without direct connection to other known events? This is a bit of a hard question for me to get across...lol For example, I know the values of events A, B, C...

I red that photon has wave properties so it can go through both slits simultaneously in the double slit experimen. What about photons that hit our eyes and construct our vision? How do we know which path they traveled and what they reflected, or to say it better how would you describe the...

If I show you three face down cards (normal playing cards, so can be either a red or black suit), and tell you that no matter which two you pick, they would be different colors, I have no doubt you'll say I'm being weird (to put it mildly). Well, nature does pretty much the same thing. This is...

Stuck on the last 3 systems on my worksheet, if someone could give me more than just the answer but also teach me how, it would be much appreciated! "Determine the nature of the intersection if it exists) between the following sets of planes. If it is a line, find the equation of it. If it is a...

When you close your eyes and visualize E=mc2 in nature without math, what images do you see? I always saw the Hiroshima mushroom cloud, but after reading your posts, I agree bombs are not the right image when introducing concept to kids. 1. I now see star core nuclear fusion of hydrogen into...

So I saw that claims are being made that LIGO may have detected gravitational waves. http://www.nature.com/news/has-giant-ligo-experiment-seen-gravitational-waves-1.18449 My question is, if the universe were in fact multidimensional as string theory predicts, would gravitational waves propagate...

When we say that elementary particles are wave-like in nature does that encompass, lead to and necessarily imply the fact that they travel in wave-like trajectories or is wave-like displacement a separate, distinct notion from their wave-like intrinsic natures? IH

Homework Statement A particle with mass m and electric charge e is confined to move in one dimension along the x -axis. It experiences the following potential: ##V(x) = {\infty}## for ## x{\lt0}## ##V(x) = -e^2/4\pi\epsilon_0x## for ## x \geq 0 ## (Note: the way the question is written down...

In page 77 of Peskin and Schroeder, it's mentioned that for a ##\phi^{3}## interaction, the energy is not positive-definite unless we add a higher even power of ##\phi##. Can someone please prove this statement?

Why is Quantum mechanics probabilistic? what prevents it from being deterministic, like classical mechanics ?(is it the lack of information about the processes and the forces applied at this scale?)

Hello everyone I recently read a publication (attached) in Nature which talks about microwave-to-optical conversion. The setup consists of resonator depicted by a circle. It is mentioned that this resonator has non-linear electromagnetic response. Up-conversion takes place by three-wave mixing...

why is gravitational force always attractive in nature?

Considering the multiple universe view, if a measurement (or something else) makes visible which universe we are in, is it then also possible we find ourselves in one with (slightly) different laws of nature?

Hi I have started studying Quantum Mechanics on my own and I had a question that I am stuck on. I apologize if it's too basic or if someone else asked it I understand what Pair Production is, but the source I am learning it from is saying that Pair production, is another way to prove the Quantum...

Is it a particle, or not? My Chemistry teacher has been saying both and I am not sure which it is. Sometimes he says that energy is a particle, while sometimes, it is just a wave moving through particles. Thanks very much.

Hi all :) I am about to finish the chapter of electromagnetic induction in my class. And I taught my students that the electric field induced due to changing magnetic flux is different that the electrostatic field due to stationary charges(Now I am wondering would it be wrong if I used the...

What does the standard model have to say about the relationship between the total mass-energy of the universe and the characteristics of forces and force-carrier particles? That is, if the total mass-energy were different, would the nature, strength, … of the forces and force-carrier particles...

I was recently taught in school about the propagation of light as a combination of changing electric and magnetic fields. I had read somewhere that a magnetic field was basically an electric field in a moving frame of reference. So,I wanted to know if in some frame the propagation of light could...

Homework Statement A student enters Best Buy prepared to buy a pair of speakers. Before he does so, he conducts an experiment with them. He places the speakers4.0 m apart and connects a signal generator to both speakers that produces a single and consistent tone. (constant wavelength and...

what is the nature of singularity of the function f(x)=exp(-1/z) where z is a complex number? now i arrive at two different results by progressing in two different ways. 1) if we expand the series f(z)=1-1/z+1/2!(z^2)-... then i can say that z=0 is an essential singularity. 2) now again if i...

1.Is electric current a microscopic or macroscopic quantity?I think it is macroscopic as we can feel it,but when I asked my friend he said it is microscopic as it deals with electrons.I'm a bit confused... 2.What is the speed of electricity?Is it equal to the drift velocity of electrons or the...

Dear PF Forum, After all these post'. I want to know that my understanding of twins paradox is close enough. So, Green travels, Blue stays. Blue keeps sending signal, Green bounces the signal. Doppler factor = 1/4, so ##\frac{1}{4} = \frac{1-v}{1+v}; v = 0.6## And at event T0 (from B), Green...

I've often wondered, but have never found a solid explanation for, why the chemical elements are found together in nature? Why aren't atoms all in a somewhat homogenous mix? Why are X atoms found with other X atoms? And why are isotopes found together, such as Uranium 235 and the far more...

I'm having difficulty gauging what the accepted interpretation of the quantum nature of matter is. On the one hand I have been taught that properties of a particle are always definite, but due to the quantum nature of existence we cannot measure several properties to 100% accuracy at once. On...

Hello! Please help: A world line is given to us. It is known that it is a geodesic. The metric, however, is not known. Since we don't know the metric, it should not be possible to tell whether the geodesic is spacelike/timelike/null (Right?) But since the geodesic is known (x,y,z,t), we can find...

How can the fact that ##\hat x## and ##\hat p## are Hermitian be used to prove that ##\hat x - \frac{i}{m \omega} \hat p## and ##\hat x + \frac{i}{m \omega} \hat p## are adjoints of each other?