Precession Definition and 248 Threads

Homework Statement Homework Equations I didn't get what this actually means. The Attempt at a Solution I'm not sure whether it is correct. Could you take a look? Regards!

Homework Statement Consider the Godel Metric in spherical coordinates as on page 6 here; ds^2=4a^2\left[-dt^2+dr^2+dz^2-(\sinh^{4}(r)-\sinh^{2}(r))d\phi^2+2\sqrt{2}\sinh^{2}(r)dt d\phi)\right] This is a solution to Einstein's Equations if we have ##a=\frac{1}{2\sqrt{2\pi\rho}}## and ##\Lambda...

Homework Statement Hi I'm having trouble with a question that's asking me to calculate the precession rate for a spinning top. The trouble that I'm having is that I don't understand how the angular momentum points along the axis of the spinning top (picture attached). When I use the formula...

The period of the lunar apsidal precession is about 8.8506 years measured against fixed starts. How can I accurately convert this to the period between alignments with spring equinox? Thanks.

Hi guys, while going through rotational energy levels of molecules, I found myself struggling with a very basic concept. The concept of precession, in terms of a torque induced rotation of the rotational axis of a spinning rigid body. Take a glance at the Wikipedia figure...

Is calculating the Euler angles analitically possible? I am trying to obtain the angles to transform the body-fixed reference frame to the inertial reference frame. I can get them without problems with numerical methods. But I would to validate them analitically, if possible. I followed the...

Hello I was watching some videos about gyroscopes and inertial guidance. In one of the videos lecturer said that rotating gyroscope set in one direction on gimbal will be pointing one direction and stay like this virtually forever, so we can use it for guidance system. However I read more...

(This is not about the motion of the planets.) If one takes a body in space (not outer space, necessarily) with only central forces, it may exhibit one of two types of precession: direct or retrograde. If the body is flat, the precession is retrograde: the spin and precession rates have...

Homework Statement A) Use Euler's equations to solve for the precession rate of a rapidly spinning gyroscope precessing uniformly (no nutation). Use I3 for the moment along the z axis along the axle. Beginning with Euler's equations, derive the coupled equations: ## \dot ω_1 + Ω ω_2 = \frac...

First time caller, I'm a newb so go easy on me. So I was trying to work through a calculation to figure out the precession rate variation in terms of the Precession of the Equinox. I came across the following formula from...

In his book Gravitation and cosmology, Weinberg derives the perihelion precession of Mercury in the Robertson expansion. The final formula is \Delta\phi =\frac{6\pi M G}{L} \frac{2+2\gamma-\beta}{3} The second term is one for GR (β=γ=1). I have two questions regarding this formula: 1. The...

Hi. I'm interested in how physicists in the mid-19th century such as Urbain Le Verrier were able to compute the gravitational influences of the other planets on the apsidal precession of Mercury's orbit, finding that they can only explain about 531" (per century!), not the observed 574". This...

Hi all. I ended up to this section in K&K (2nd edition, but with 1st is the same) when they derive the wobbling motion of a simple body in torque-free precession. [see the attached file] Equations 8.23 and 8.24 are integrated into 8.25[a|b], but I think signs are wrong. Shouldn't be negative...

This is the experiment I am a bit confused about this part: There is a torque on the wheel from its own weight. That's the τ on the picture. In this perspective, τ points at the bottom of the page. I understand that that torque changes angular momentum of the wheel and the wheel starts...

Hi, I've been learning about gyroscopic precession recently and I feel like I get it. I understand that when the flywheel of a gyroscope is spinning its angular moment plus the angular moment created by the torque from the force of gravity makes it turn. But I were thinking about the forces in a...

I have some trouble understanding the concept of spin precession in an external field from a quantum mechanics viewpoint. Hopefully someone will be willing to enlighten me. Consider a single spin ½ particle. In the absence of an external field, the projection of the spin angular momentum on...

I was watching this and I get it that when you rotate the wheel, the torque due to its weight will cause it to revolve parallel to the ground instead of perpendicular to the ground. I know that the faster you spin the wheel, the less likely the lever from the wheel to the pivot will be slanted...

I have a student who thinks he is smarter than me. When we calculate the precession the classical way we also account for the supposed oblate sun. If we model sun's oblateness by splitting the mass of the Sun into 2 masses and separate them by distance s, then the acceleration we get on point...

Question The Hubble Space Telescope is stabilized to within an angle of about 2 millionths of a degree by means of a series of gyroscopes that spin at 1.92×104 rpm . Although the structure of these gyroscopes is actually quite complex, we can model each of the gyroscopes as a thin-walled...

Hi, In the Larmor precession, we tend to define the magnetic moment as the current multiplied by the surface (for an electron rotating around a nucleus), sometimes this moment is defined (generally) as the sum of the vectoriel products of half of the position vector and the charge times the...

I have been doing a lot of exercises out of Griffiths lately, and one thing I spent a lot of time thinking about was Larmor precession. It's a fun thing to work out, but where does it actually happen? I'm having a hard time to see where it would apply. The first condition for Larmor precession...

Bill_K submitted a new PF Insights post Orbital Precession in the Schwarzschild and Kerr Metrics Continue reading the Original PF Insights Post.

Im curious what is it about space-time or Einsteins field equations which explains Mercurys precession correct while Newton's formula doesn't? So exactly what difference causes GR to explain it that Newton could not?

Bill_K submitted a new PF Insights post https://www.physicsforums.com/insights/precession-special-general-relativity/ https://www.physicsforums.com/insights/precession-special-general-relativity/

The main question is in the title. 1.I have wondered if a regular pencil would precess and rotate stable for multiple seconds if spun fast enough. [Coins, plates, bowls and similarly shaped objects can rotate in a stable way for extended periods of time. And a lot of other household objects...

I'm interested how was measured the famous Mercury's precession: 43'' / cy. How it has been measured? where is the angle 43'' - in this image: http://en.wikibooks.org/wiki/Astrodynamics/Classical_Orbit_Elements The preccesion is about the periapse, so it's defined wrt the node: therefore...

I do not get some points of this proof about the time derivative of a unit vector $\hat{u}$ (costant magnitude) which is following a precession motion. The picture is the following. I want to prove that $$\frac{d\hat{u}}{dt}=\vec{\Omega}\wedge \hat{u}.$$ I'm ok with almost all the proof except...

I haven't a textbook where I can study Earth Precession and I'm not sure to have correctly understood... Could you tell me if I do mistakes? I consider two points P and Q on the equatorial bulge. The torques of the gravitation forces between P-sun and Q-sun (calculated wrt the Earth center) are...

I'm trying to figure out the effect of a force applied to a rotating body in 4+1 dimensions. A good place to start would be deriving the effect of forces in 3+1 dimensions. I have been looking around the Internet and even went to the local community college and checked out texts in the library...

Many of you might have seen veritasium's video on the "Anti-gravity wheel". Through one of the comments, I was introduced to the idea that the reason the apparatus is so easy to lift is because the energy to do so comes from the spin of the wheel, i.e. its rotation slows down as it is lifted and...

Hi. I'm trying to take a purely translational approach to precession (i.e. not using angular momentum and torque). I'm looking at a gyroscope that consists of four point masses on a cross and at a moment in time when one mass is at the topmost point (see sketch). I'm assuming a virtual...

Over the last year or so I've been doing quite a bit of reading trying to find out what is actually causing lunar nodal precession. There seems to be a lot of handwaving but no definitive answer, which I find rather odd. Maybe I've just not found the right source. Google seems obsessed with...

Hi, If we apply a torque to a spinning wheel such that the torque vector lies in the plane of the wheel, it will precede around the axis perpendicular to the angular momentum and the torque. What happens if the wheel is mounted such that rotation around this axis is absolutely impossible and...

I would think that precession of the equinoxes occurs only if the planet is at least partially rigid. Since Jupiter is gas and liquid, it would not experience precession of the equinoxes. Is this right?

Here is a derivation of the Coriolus effect on an imaginary 4+1D planet. http://hi.gher.space/forum/viewtopic.php?f=27&t=2106 It seems wrong to me. I think that the planet is rigid, so the latitude of a point on the surface, ϑ, is a constant. It's derivative will always be zero. The first...

Homework Statement A beam of spin 1/2 particles with speed v passes through a series of SGz devices. The first SGz device transmits particles with Sz = ħ/2 and filters out particles with Sz=-ħ/2. The second SGz device transmits particles with Sz=-ħ/2 and filters out particles of Sz=ħ/2...

I watched a program that said that some of Earth's past climate change was due to variations in Earth's orbit and precession due to the the gravitational perturbations caused by Venus and Jupiter. Why would that be so? I know that the orbits of the planets are eliiptical generally and they...

Hi folks!First of all, English is not my native language so I hope there is not much misleading spelling mistakes, discrepancies and inaccuracy. I’m currently working with a hobby-project of a flying drone/UAV with two adjustable angled rotors. I’m able to make it fly more or less in a way it...

Hey everyone, I just made an account because I have a problem concerning angular momentum and precession. In the picture below you see the vectors l1 and l2 that make up total orbital angular momentum L precess around L. I can get my head around why that is the case. The same for s1 and s2...

Homework Statement When we speak about Larmor precession we refer to atomic magnetic moments precessing in a magnetic field. In ordered magnets, such as ferromagnets, I never hear about larmor precession anymore. Are the magnetic moments frozen due to interactions with the surrounding crystal...

Once the gyroscope starts to spin about the pivot it acquires an upward angular momentum. But since it did not have any angular momentum in this direction before, and the only torque is due to the gravitational force, how does this new angular momentum suddenly arise. Isn't this a violation of...

Homework Statement A top spins at 33 rev/s about an axis that makes an angle of 26° with the vertical. The mass of the top is 0.47 kg, its rotational inertia about its central axis is 5.0 x 10-4 kg·m2, and its center of mass is 3.1 cm from the pivot point. The spin is clockwise from an overhead...

This is the kind of gyroscope that I am talking about: Where did the kinetic energy of precession come from? The gyroscope's spinning angular inertia? If so, how does it transfer into the precession? Is a torque applied horizontally (along the x-y plane) when the system is under the effect of...

Hello! I have recently been looking into the phenomenon of gyroscopic precession in my free time, and there is a scenario which I am not sure I have fully understood. Here it is: Imagine a bicycle wheel with a shaft running through it's center. The shaft is attached to a rope at one of it's...

I watched an interesting video on YouTube by veratisirm where he had a meter long metal rod with a huge metal fly wheel on the end of it. Long story short he could barely lift the thing but under full spin he could just about swing the thing like a sword. the only thing was the precession wanted...

To motivate the question, Andy Strominger recently put out a paper on calculating the Sagnac shift of counterrotating beams due to the angular momentum flux of a passing gravitational wave. See here: http://arxiv.org/abs/1502.06120. But consider now two nearby freely falling gyroscopes...

Hello, I am doing a project on a Gyroscopic Briefcase. What i want to know is that, if i add some additional mass to the rotating gyroscope ( which is in preceession ) what would be the result in the precession of gyroscope? Is there any numerical way to find the final result (i.e. speed...

Unlike firearm projectiles, air rifle pellets have evolved to a generally typical diabolo configuration. For reference, see: http://www.photosbykev.com/wordpress/2009/01/20/air-rifle-pellet-database/ The initial shape was described as like that of a badminton shuttlecock, and "skirt" at the...

This is the Anti gravity wheel video from Veritassium. I have a similar problem to calculate the forces on arm. How can I calculate the precession force pushing the arm vertically ? Lets assume that the angles between shaft and arm is 90° the angles between shaft and wheel is 90° The wheel...

Hi, If the axis of a spinning top isn't vertical, it starts to precess. I'm perfectly familiar with the explanation using torque, angular velocity and momentum vectors, then the direction of the precession comes out just by taking a vector product. However, to me it's absolutely not intuitive...