# Questions tagged [rotation]

Questions regarding the action of or an object rotating along an axis.

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### Calculating field rotation between two times

I have the formulae to calculate the rate of field rotation at any given time, and using a python script with Skyfield I can generate a a value incrementing every 10th of a second based on the live ...
1 vote
4k views

### How are East and West defined on other bodies of our solar system?

I noticed that East and West appear swapped on maps of the Sun, even though the Sun rotates around its polar axis in the same sense as Earth. See for example below Sun disk with a Venus transit ...
10k views

### How did the ancient cultures determine that the year was actually a fraction of an extra day beyond 365 days?

Google says the year is exactly 365.2422 days, and so they make a leap year every 4th year, but that ends up being 365.25 days per year on average. So every 100th year they don't have a leap year, but ...
21 views

### What direction do Herbig Haro outflows go from?

After doing some research about Herbig Haro objects, I found that the outflows are formed perpendicular to the circumstellar disk. Is that the same direction as the star's rotation, or is it the ...
3k views

### Earth is Tilted, but in reference to What Object / relative to what?

I am asking basic question on trying to understand on tilt. I know if I (as a human) tilt when standing on feet, my tilt will be in relation to gravity. For Earth, I am not able to understand, what is ...
3k views

### If the Earth is rotating counter clockwise, how does the sun rise from east?

I was very confused when I watched this video from 2:18 till 2:45. And it seems very clear that if the Earth is really rotating from west to east, shouldn't be the Sun rising from west and setting in ...
1k views

### Are galaxies growing, shrinking or stable?

When I look at spiral galaxies they look a bit like the whirlpool of water going down a sink and I wonder if eventually they shrink to a small point (or a giant black hole?). On the other hand they ...
6k views

### Is it coincidence that the earth's rotation and revolution are in the same direction?

In a reference system where the sun is static, the rotation and revolution of the earth are, when viewed from above the north pole, both counterclockwise. Is it a coincidence that they agree? Or does ...
170 views

### How can Jupiter rotate faster at the equator than at the poles (in degrees per second)?

Jupiter rotates slightly faster at the equator. If inertia is conserved as average angular momentum, what is the physical mechanism that creates a gas which is ~1% faster angular momentum at the ...
425 views

### Does the rotation of galaxies precess?

Does the axis of a galaxy as a whole "wobble" the same way that the Earth does? If so do we have any idea how much or how fast the Milky Way is doing so?
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### What are the effects of mass concentration along a planet's axis of rotation?

Reading about geological history of Mars and coming across the Martian dichotomy, which is about having the two hemispheres' geography differ in elevation by 1 to 3 km. Does this mean that Mars' ...
1 vote
70 views

### is there anything that might cause a planet to stop getting sunlight permanently, or to only have light infrequently? (on the whole planet or part)?

(writing a story) Is there anything that might cause all or part of a planet to stop getting sunlight, or to have a permanent/ridiculously long-lasting perpetual twilight? nuclear winter? volcanic ...
1 vote
176 views

### What does the earth's (a planet's) orbit cause?

I know that the earth's rotation causes day and night. It seems/feels so natural to think that the earth's orbit around the sun causes the seasons, but no it's the tilt of the earth's axis that causes ...
1k views

### What is meant by sun's path through zodiac

I read somewhere that sun's daily course and complete cycle is visible in the ecliptic belt by zodiac constellations. I didn't understand what that means closest I could find online is: https://www....
194 views

### Are there any bodies in the solar system whose rotation is almost tidally locked or barely tidally locked?

The Moon's rotation is firmly tidally locked to the Earth and the Earth's rotation is firmly tidally unlocked with respect to the Moon. I gather that Mercury's rotation is tidally locked in a 3:2 ...
1 vote
98 views

### Reference point for the directions

Are directions [North, South, West, East] derived from Earth's rotation around its axis? What makes north north and the south south? Is it arbitrary or is there some specific reference point?
109 views

### Does rotation on their axis cause winds in gaseous planets?

As far as I know, as planets rotate around their axis, they can influence winds but not cause them (like the Coriolis effect) However, does this apply only for rocky planets? Do rotation alone in ...
818 views

### Which of the exoplanets are having retrograde rotation?

By exoplanet, I mean planets outside of our solar system(i.e., planets in other solar systems). If we talk about our solar system, then Venus, Uranus, and Pluto have retrograde rotation. Most of the ...
151 views

### What should be the "poles" for irregular shaped bodies?

Continuation of: What is the definition of a "pole" of a celestial body? uhoh's answer says that distinct bodies should have a center of mass. If the body is spherical, then the COM will be ...
597 views

### Why do the Sun and gas planets rotate faster at equator than at poles?

From this site, it states that: The Sun spins faster at its equator than at its poles. I have also read somewhere that the gas giants (gaseous planets like Jupiter, Saturn, Uranus, and Neptune) also ...
1 vote
53 views

### Determining the rotation curve of a galaxy via given spectroscopic data

Here is the data analysis question from IOAA-2011, 1. Weighing a galaxy: The image 8.2 shows a photograph of the spiral galaxy NGC 7083, which lies at a distance of 40 Mpc, and image 8.3 a fragment of ...
372 views

### How does the gravitational wave strain from a rotating binary depend on the chirp mass, frequency and distance & what a short derivation looks like?

Our most familiar experience with wave propagation either from firsthand experience or in school comes from the phenomena of sound and light and radio electromagnetic propagation. In air, we know that ...
1 vote
81 views

### Moonrise and Moonset time in Sydney vs Perth

I'm very confused with multiple moonrise and moonset times across Australia. For Example (According to https://timeanddate.com) Moonrise in Sydney on 22 Mar 2023 is at AEST 7:09AM which is going to ...
529 views

### Can a tidally locked planet sustain a magnetic field

The vast majority of stars in the Galaxy, and probably the universe, are red dwarfs. The habitable zones of these stars are very close to the stars themselves, often within what would be Mercury’s ...
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### Convert from magnetic coordinates to true coordinates

I am working with the IGRF (International Geomagnetic Reference Field) model and from a journal article found here, I am able to compute the earth's magnetic field at any point in spherical ...
10k views

### Will Earth rotate backwards in the future?

Hello recently I heave heard the earth will eventually start rotating in the opposite direction (ie sunrise from the west) . I am not sure if this is true, but a lot of sites are claiming it to be ...
3k views

### How scientists find the direction of rotation of planets?

How do we know that Mercury, Earth, Mars, Jupiter, Saturn, and Neptune rotate counterclockwise and Venus, Uranus, and Pluto rotate clockwise? How do scientists determine the direction of rotation of ...
421 views

### What is the v sin i parameter?

In the August 2021 preprint by WeiJia Sun et al. Exploring the stellar rotation of early-type stars in the LAMOST Medium-Resolution Survey. II. Statistics there is histogram plot with the caption: v ...
2k views

### Why is the sunset at different times at the same longitude at equinox?

I happen to live in two places that are literally at the same longitude but several thousand kilometers apart from each other (~47°N and ~68°N). It's just a few days until equinox - and I assumed that ...
1 vote
481 views

### What was this "light" that looked like a star moving repeating from point A to B for about 5 mins [duplicate]

I was looking in the sky one night about 9:45. There was what looked to be a shooting star but much slower and brighter more like a satellite. It was moving (from standing on earth) it looked like a ...
2k views

### Motion of rogue planets

Two Questions: 1) Are rogue planets in motion, i.e. are they just wandering freely in space or stationary? 1) Do rogue planets have defined path or a one which can be anticipated? I understand that ...
1k views

### What is the rotational speed of Sagittarius A*?

Sagittarius A* is the Milky Way's own supermassive black hole. Up till recently, I used to think that Sagittarius A* was a static black hole, i.e. It had no rotational speed at all. But after doing a ...
529 views

### As the Moon and the Earth are predicted to get into tidal lock, how slow would the Earth rotate?

This answer to Will the Earth ever be tidally locked to the Moon? supports the widely held thinking that during the Sun's red giant phase or later the Earth and the Moon should be tidally locked to ...
57 views

### Calculation of intersection point Q of planetary equator with ICRF equator for other planets

I'm converting the W for each planet in this IAU report into Celestia's MeridianAngle, which is converted like this: $$\textrm{MeridianAngle}=W-Q$$ Where Q is the point where the planet's equator ...
81 views

### Can the pebbles growth model be applied to the rotations of planetary systems? [duplicate]

I've just read the University of Amsterdam 2019 News item Pebbles determine the direction in which planets rotate (which links to R.G.Visser et al (2020) Spinning up planetary bodies by pebble ...
8k views

### Do planets lose energy while rotating?

When a planet rotates/spins, is it true that the planet loses energy? If this is true, then where does this energy lost by the planet go? My confusion may be in the basic understanding of the ...
68 views

### How long would it take for a planet captured by a red dwarf to become tidally-locked if it started out rotating retrograde?

So say for the sake of argument that we have a red dwarf orbiting a G of K-class star. An Earth-sized planet forms, maybe at one of the dwarf star's Lagrange points to its primary, and eventually ...
1k views

Prograde means rotating in the same direction in which most of the planets in our solar system rotate, which is counterclockwise, and retrograde rotation means the opposite, i.e., clockwise rotation. ...
162 views

### How much would you weigh at the equator of the fastest spinning pulsar?

Assuming you have a mass of 70 kg, what would your weight be on the equator of PSR J1748−2446ad?
1 vote
60 views

### What can we learn from the rotation data of a star?

Knowing the speed of a star's surface rotation gives us what data and information. For example, if it is a big star, is it possible to measure distance using the doppler effect? Or can we calculate ...
1 vote
91 views

### How to model galactic rotation curves?

I have R (kpc)- distance from galactic center and v(km/s) rotational speed at that distance. I was thinking of creating a simple model comprising of 3 terms 1 for Keplerian component another for rigid ...
62 views

### Where can I find galaxy rotational data?

I want to do a small project of generating rotational curves for different galaxies, and need data for some prominent stars in other galaxies (data needed: distance from center, rotational velocity) ...
1k views

### Rotation direction of Pulsars

Pulsars are rotating neutron stars observed to have pulses of radiation at very regular intervals that typically range from milliseconds to seconds. It has a very strong magnetic fields which funnel ...
1 vote
84 views

### Do relativistically measured rotation speeds (Special Relativity) change planetary mass slightly through Lorentz transformation?

Thanks @ConnorGarcia for your Answer. Avoiding 'Tidal Locking' for now - the rotational angular momentum Lrot is 10,000,000 times smaller, so negligible, but could it still be a factor in eccentricity?...
1 vote
252 views

### What else can we learn from a Foucault pendulum? Have they ever been used to determine anything more than that the Earth rotates on its axis?

Background Each semester we have to make up projects for each course. This semester I took Cosmology and Astrophysics and we covered a vast amount of topics, from luminosity of stars to Einstein's ...
249 views

### Earth’s rotation speed vs rate of lunar cycle

Hypothetical Question If the earth’s rotation slowed down to align to the lunar cycle so that the orbital period began and ended at the same lunar phase, what other things would result? For example, ...
198 views

### Does Earth's rotation cause any structural changes in the Earth? [closed]

I tried searching for this and while all results talks about changes of day and night, impact on direction of wind, cyclones, etc, they do not say whether it causes any structural changes in the long ...
124 views

### Why would a freezing liquid layer accelerate a rocky body's rotation?

Titan, whose orbital period is 382 hours, is tidally locked, like all round moons in the Solar System. But Jonathan I. Lunine said of Titan: One thing that Titan could not have done during its ...
We know that each ellipsoid has 3 diameters named $2a$, $2b$, and $2c$. The Earth and all planets, in general, are ellipsoids (Saturn is the best example because it's the most oblate planet in the ...