1
vote
1answer
127 views

Is it pure luck to observe a gravitational wave?

I actually have two questions: Since only a gravitational wave that is strong enough can be detected and the GW passes by the earth at light speed, can I say that we are lucky to detect one this ...
0
votes
1answer
32 views

Why is Kirchoff's Voltage Rule not satisfied when the circuit is shorted?

For example if I have a simple circuit with a battery and a resistor, and then the resistor is shorted, Kirchoff's Rule is no longer satisfied. Since the current through the resistor is 0, the voltage ...
0
votes
2answers
23 views

The image of a wall clock is to be obtained on the opposite wall 2m away by the means of a convex lens. What is the minimum focal length required?

I'm in 10th grade and this question came in my physics test. Nobody was able to answer this question correctly except my physics teacher who says that the answer is 2m. My answer is that there should ...
0
votes
0answers
14 views

Best frequency for Underwater Transmission

What is the best frequency of transmission of under the water for communication with good data rate? I have read that the threshold of hearing underwater is around 170 to 180 db. Can this be useful in ...
0
votes
1answer
30 views

What does the presence of gravity waves show? [duplicate]

Is the essence of the discovery of gravity waves that we now know that gravity propagates through space at the speed of light and not instantly?
0
votes
1answer
27 views

Temperature of heat and body

Today I was having a cup of tea. I put it on the table, then held it for a while, then drank some tea, than put the cup on the table, and repeated this cycle several times. I noticed that when I was ...
5
votes
0answers
27 views

What is the structure of an event horizon for colliding black holes?

I would suspect that two black holes within close vicinity of one another would warp each other's event horizons such that the Schwarzchild's radius would no longer apply. Do the event horizons ...
4
votes
3answers
82 views

How are the 4 km arms of LIGO measured so accurately?

The arms of the LIGO interferometer are 4 km long. Now, LIGO functions by measuring phase difference between two beams of light comming (as in Michaelson's Interferometer) to a sensitivity of ...
0
votes
1answer
20 views

Will a charge attract or repel bar magnet?

I read in many answers that magnetic fields are basically electrostatic fields arose due to motion of charges usually. It gave me a question, Let there is a charge of 1C in vicinity, and a bar ...
2
votes
1answer
33 views

why does the chemical potential vanish for Bose Einstein condensate

the reasoning in a Bose Einstein condensate is to try to account for all the particles in the excited continuum states by tuning the chemical potential. However at a critical temperature $T_c$ the ...
0
votes
0answers
13 views

If magnetic force (hence torque) does no work, how does a dipole placed in a magnetic field have a potential energy associated with it?

If potential energy equals negative of work done and magnetic force does no work what force does the work?
8
votes
1answer
287 views

Is there a “CGBR”?

The recent discovery by the LIGO made me wonder about this. We know that there exists a CMBR, Cosmic Microwave Background Radiation, a blanket of electromagnetic energy covering the universe, made by ...
1
vote
0answers
21 views

What are some of the best Physics resources online? [duplicate]

Are there any sites similar to (in terms of function and quality) Paul's Online Math Notes, 17Calculus.com, or PatrickJMT.com, for Physics (besides Khan Academy)? I've googled this, but the sites ...
0
votes
0answers
34 views

How did he find the “lambda” value in this question?

There is a pdf i found when searching about Lagrangian Multpliers, but i was not able to understand how he derived lambda from two differential equations. If anyone can walk me through it, i would be ...
0
votes
0answers
16 views

Car wheel's “slip ratio” equation for game

Some of you may know about slip ratio. It is specific ratio that kind of depends on wheel rotation speed, radius etc. and affects friction. Car has the most friction at around 0.05-0.1 slip ratio ...
-1
votes
0answers
14 views

IB Physics Internal Assessment [on hold]

What can be good topics for physics internal assessment that can be done in lab especially in electricity or waves portion?
0
votes
0answers
18 views

How do I start studying astrophysics and it's relations with relativity?

I am a high school student who's very interested in astrophysics and the whole idea that space time is infact a fabric rather than nothing. Unfortunately, my school teaches no where near to any of ...
0
votes
0answers
33 views

In a $\phi^4$ theory, does the single vertex Feynman diagram (with no internal propagators) contribute to the scattering amplitudes?

If I have an interaction term in the Lagrangian of the form: $$ L_{int}=g\frac{1}{4}\phi^4 + g'\phi^3\chi +... $$ How does the trivial diagram (i.e. just a cross with a vertex at the center) ...
3
votes
0answers
16 views

Cepheid light curves

I've got the light curve of a Cepheid variable. How can I derive (mathematically, not by eye) its period and its average apparent magnitude? i.e., in what form should the best fit curve be? I've read ...
0
votes
1answer
18 views

Why are fringes displaced when a thin film is introduced (Michelson interferometer)?

I'm reading everywhere that when you place a thin film in one arm of an interferometer, fringes are displaced. No-one seems to explicitly say why; maybe because it's meant to be obvious. I know ...
-7
votes
2answers
73 views

Can Newton's law of gravitation and Einstein's GR be considered true and complete laws of gravitation? [on hold]

Newton's law of gravitation and Einstein's general relativity (GR) are empirical laws of gravitation that are strong on description and prediction but lack deterministic and/or causal rigor, which ...
1
vote
0answers
10 views

Period-Luminosity relationship in Cepheid variables

I'm investigating the period-luminosity relationship in Cepheid variables. I know such a relationship has already been discovered; however, I'm trying to figure it out by myself as part of a school ...
-2
votes
1answer
29 views

Phase differences due to reflection etc [on hold]

http://www.physicsgalaxy.com/lectures/1/30/1749/Solved-Example-15#42 see this link(only question) and see 1:21. Phase difference is given as $2\mu t$ but shouldn't it be $2\mu ...
2
votes
2answers
87 views

Gravitational Wave Impact

What would we see and feel if the waves were powerful enough? Do the waves influence whatever they pass through like a pressure wave would? Or would they be more transparent to the subject there ...
0
votes
0answers
28 views

How would I go about making a rough estimate of the capacitance of an isolated human body?

I have been asked to make a rough estimate of the capacitance of an isolated human body. The question has also stated that it must lie somewhere between that of an inscribed sphere and that of a ...
0
votes
1answer
19 views

Black hole expiration dates

According to a comment on this site: Very "light" black holes have a life expectancy in the range of $10^{18}$ years while very "heavy" black holes have a life expectancy between $10^{12}$ or so ...
4
votes
2answers
55 views

Two naive questions about gravitational waves

My understanding of GW is that they ripple the fabric of the space-time just as accelerating charged particle emits electromagnetic radiation, accelerating massive objects produce gravitational ...
0
votes
1answer
47 views

How to get $a(t)$ and $v(t)$ from $a(x)$ without knowing $x(t)$?

Suppose to know, for a one dimensional motion of a particle, the acceleration as a function of the position $a(x)$. Using $\frac{dv}{dx} v=a(x)$ I can get $v(x)$ as a function of the position. Is ...
0
votes
0answers
11 views

AdS3/CFT2 duality for free bulk scalar

I am looking at lecture notes by Kaplan. http://www.pha.jhu.edu/~jaredk/AdSCFTCourseNotesPublic.pdf Through chapters 4, 5, and 6 he takes the free field in AdS3 to the boundary to create a CFT2 ...
0
votes
1answer
20 views

Mechanics of Rotational Motion [on hold]

Well, I faced a problem in my Physics Examination Problem: A Circular Disc of Mass $M$ and radius $R$ is set rolling on a table. If $\omega$is angular velocity, ST total energy ...
0
votes
0answers
20 views

Advection Operator shift in scalar product

Can someone help me with advection operator shifts? I can't figure out the rule for the shift inside of a scalar product. The terms $(u,(v\cdot \nabla)\delta v)_\Omega$ and $(u,(\delta v\cdot ...
0
votes
1answer
22 views

Is there a way to move a black hole?

Is it possible to move or transport a black hole? What about a white hole?
4
votes
1answer
42 views

Gravitational waves in other dimensions

I know this question is purely speculative, as we don't know if more dimensions do exist and also we do not know if gravity is indeed stronger in other dimensions (if they were to exist). But, one of ...
0
votes
1answer
29 views

Gravitational imaging

As the most recent discovery in physics suggested the gravitational waves are now scientific fact. My question is: If that's the case so is it possible in principle to make perfect 3d imaging of an ...
0
votes
2answers
25 views

Can electron capture occur with an external electron?

Can electron capture proceed with an electron not bound to the nucleus which decays (that is one that is bound to a neighboring atom, bound in a collective state like a conduction band, or free)?
2
votes
0answers
13 views

Will the Polarity of magnet be reversed or will it rotate? Will the ferromagnet melt in varying strong magnetic field Or will the domain strct collaps

According to the domain theory, Ferromagnetic substance when kept in the external strong magnetic field, it undergoes magnetisation by Rotation and becomes a permanent magnet thereby even after ...
0
votes
0answers
37 views

Energy Conversion from Mass to Gravitational Wave

How is mass converted to gravitational wave energy by inspiralling binary black holes? Is the gravitational wave energy coming purely from the kinetic energy/gravitational potential of the two black ...
0
votes
1answer
45 views

Can photons undergo quantum tunneling?

Most leptons can do this so I'm curious to see if photons or any bosons at all can.
0
votes
1answer
24 views

Why does the co-efficent of friction between plane and body does change depending on the angle of the plane?

First of all I know there is a similar question to this one. However, it didn't help me resolve my problem. Let's say there is a body on a angled plane and the system is in equilibrium (the body ...
1
vote
0answers
25 views

Local temperature equation for a planet

After seeing in science fiction too many planets with two suns that look too much like a geocentric system, I'm trying for my own amusement to understand if it's really possible to have a planet with ...
1
vote
0answers
12 views

How to include temperature effect in optical bloch equations (optical pumping)?

My problem is about the optical pumping of Alkali atoms by circularly polarized pump light. Consider a circular polarized light ($\Delta m=+1$) $$\vec{E}(z,t)= \vec{E}^{(+)}_0 e^{-i\nu t}+c.c. $$ ...
0
votes
1answer
51 views

Why does vector addition work in physics?

How do we know for sure that vector addition works while working in 2D?Is there a mathematical proof for this?
0
votes
1answer
39 views

What effect would GW150914 have had over a much shorter distance? [duplicate]

In the wake of the recent news of the confirmation of the existence on gravity waves, I was discussing gravitational waves with a friend, and he asked whether this could potentially lead to some kind ...
0
votes
0answers
18 views

Light from the big bang [duplicate]

Considering that the Big Bang all started from a single point in space time, and the light emitted from it has been spreading outwards in all directions ever since, how do we, from earth, see the ...
0
votes
0answers
25 views

How to find the position of a particle in a vector (force) field? [on hold]

Let's say that we have two dimensional space and in it a particle. This space has a vector field which is defined as: $$F = x^2$$ For every 1 unit of displacement in the x direction, the force vector ...
4
votes
2answers
74 views

Why are magnets not in form of hollow spheres

If magnets were in form of follow spheres, outer surface and inner surface being either north or south pole, then I cannot imagine what would be the field be like. But in that case, every magnet would ...
2
votes
0answers
44 views

How LIGO is calibrated?

I think I have understood properly the principle of LIGO, however the sensitivty is around $10^{-18}m$ of accuracy of distorion. That looks pretty small... just starting with simpler phenomena, for ...
-4
votes
2answers
143 views

LIGO may have inadvertently detected the helioseismic burst from the Sun on 14 September 2015

Here is a quote from an online article: "A gust is on the way. NOAA forecasters expect a stream of high-speed solar wind to reach Earth on Sept. 14th-15th, sparking renewed displays of high-latitude ...
-1
votes
2answers
52 views

Is dark matter really there?

Dark matter has been proposed to explain two phenomena - Uniform velocity curve of spiral galaxies Observed gravitational lensing. If something explains these two, would we still need dark ...
2
votes
1answer
107 views

How did the scientists know two black holes collided 1.3 billion years ago?

I saw a TEDx talk the previous day about the LIGO experiment and in that video he said they are waiting for the day Jan 1st 2017 for the Ripple in Gravity caused by two black holes colliding each ...

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