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Questions tagged [rotation]

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

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19 votes
8 answers
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 ...
Lance's user avatar
  • 431
1 vote
1 answer
45 views

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 ...
Tanenthor's user avatar
  • 623
0 votes
0 answers
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 ...
Astrovis's user avatar
  • 733
14 votes
1 answer
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 ...
puzzled's user avatar
  • 607
13 votes
1 answer
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 ...
KDP's user avatar
  • 373
25 votes
4 answers
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 ...
Marc Vaisband's user avatar
3 votes
0 answers
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 ...
Wolfgang Weber's user avatar
5 votes
1 answer
76 views

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' ...
user avatar
1 vote
0 answers
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 ...
Zeantra's user avatar
  • 11
1 vote
1 answer
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 ...
Hudjefa's user avatar
  • 353
1 vote
0 answers
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?
Bill Thompson's user avatar
4 votes
2 answers
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 ...
vengaq's user avatar
  • 1,017
1 vote
0 answers
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 ...
samuraiwarrior's user avatar
5 votes
3 answers
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 ...
uhoh's user avatar
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1 vote
1 answer
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 ...
Hunter Q's user avatar
4 votes
2 answers
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 ...
user98816's user avatar
  • 469
0 votes
0 answers
53 views

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 ...
mwoods's user avatar
  • 1
4 votes
1 answer
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 ...
Alastor's user avatar
  • 2,668
2 votes
0 answers
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 ...
ILikeSaturn's user avatar
4 votes
2 answers
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 ...
Elena Greg's user avatar
1 vote
0 answers
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 ...
DJ7420's user avatar
  • 27
10 votes
1 answer
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 ...
apk's user avatar
  • 949
18 votes
4 answers
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 ...
apk's user avatar
  • 949
3 votes
0 answers
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 ...
PrincipledStarfish's user avatar
11 votes
2 answers
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 ...
apk's user avatar
  • 949
3 votes
1 answer
1k views

Does the Sun shift periodically between prograde and retrograde rotation about its axis?

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. ...
apk's user avatar
  • 949
8 votes
1 answer
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 ...
apk's user avatar
  • 949
0 votes
0 answers
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?
A.J Perez's user avatar
1 vote
1 answer
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 ...
Aegean's user avatar
  • 109
1 vote
0 answers
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 ...
Hardek A.'s user avatar
2 votes
0 answers
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) ...
Hardek A.'s user avatar
8 votes
1 answer
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 ...
Autodidact's user avatar
1 vote
1 answer
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 ...
Parmeet Singh EP 066's user avatar
2 votes
2 answers
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, ...
Peter Heffner's user avatar
2 votes
1 answer
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 ...
user96551's user avatar
  • 121
6 votes
1 answer
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 ...
J.G.'s user avatar
  • 325
2 votes
2 answers
533 views

Could a magnetosphere be created for Venus by recreated by spinning-up the planet to a 24 hour day?

If Venus in it is current state, started rotating at the same rate as Earths 24hrs rotation, would it develop a magnetic field of roughly the same strength as Earth's? If so, would that help in any ...
eBookworm's user avatar
  • 145
17 votes
3 answers
5k views

If planets are ellipsoids why don't we have 3 diameters?

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 ...
Snack Exchange's user avatar
4 votes
1 answer
171 views

The orbital period of Jupiter and Europa billions of years later

We know that the Sun gets so big billions of years later and the Earth will get destroyed. What will the orbital period of Jupiter (Sun-Jupiter system) and its moon Europa (Jupiter-Europa system) be ...
Snack Exchange's user avatar
10 votes
3 answers
3k views

Why does a timelapse video of a stationary Milky Way make the horizon appear to move from horizontal to vertical?

In this video, with a rotating camera keeping the Milky Way 'stationary,' the horizon appears to transition form horizontal to nearly vertical. I understand the Earth ...
99Gretzky99's user avatar
12 votes
1 answer
2k views

What rotational speed would Mercury need to have to achieve a temperature comfortable for humans

I wondered what rotational speed would Mercury need to have to achieve a temperature comfortable to humans, let's say 20 °C. EDIT: My idea was that if Mercury is so cold on the night side and so hot ...
Piotr Golacki's user avatar
9 votes
4 answers
2k views

Is there any difference between tidal locking and synchronous rotation?

I'm trying to understand more about orbital mechanics, and I'm encountering a few terms which I'm not sure if they are exactly the same. The two terms are Tidal Locking and Synchronous Rotation. To my ...
ValientProcess's user avatar
2 votes
6 answers
679 views

Am I looking at the moon upside down here in the US?

This may be a very basic question, but I just learned that the moon orbits around the earth counterclockwise. I always thought the earth and the moon shared the rotation and orbit direction. Since the ...
Joe DiNottra's user avatar
3 votes
0 answers
52 views

Would tidally locked Earth-like exoplanets necessarily have hot pole/cold pole atmospheric circulation?

A tidally locked planet orbiting a red dwarf star in its habitable zone would have a rotational period equal to its orbital period, on the order of days or weeks. Given a thick enough atmosphere ...
RobertF's user avatar
  • 183
1 vote
1 answer
407 views

Has Altair flung off its planets by rotation?

This might be a dumb question, but would it be possible that during the star Altair's formation, the centrifugal forces became so large that its planets were flung away into space? Or could a passing ...
AlgebraicsAnonymous's user avatar
9 votes
2 answers
2k views

What is the exact reason for the Sun's differential rotation to occur?

The following is an excerpt from the Wikipedia article for "Differential Rotation": Differential rotation is seen when different parts of a rotating object move with different angular ...
user avatar
1 vote
1 answer
127 views

Solar Rotation Varies with Latitude. Effects?

From the Wikipedia article of "Solar Rotation": Solar rotation varies with latitude. The Sun is not a solid body, but is composed of a gaseous plasma. Different latitudes rotate at ...
user avatar
1 vote
3 answers
188 views

Axial Tilt One or Two Angles

Why is the axial tilt of a planet expressed as a single angle when two angles are necessary to specify a point on a sphere? Imagine if the Earth’s axial tilt were 90 degrees, then the axis of rotation ...
tomek dobrzynski's user avatar
1 vote
1 answer
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?...
Rob Clennell's user avatar
3 votes
1 answer
344 views

Is the 'spin' of Earth and the 'spin' of Mars a significant contribution to their angular momentum?

Is the 'spin' of Earth and the 'spin' of Mars taken into account as a contribution to the conservation of angular momentum? (and a contribution to the increasing/decreasing eccentricity?) Or - is the ...
Rob Clennell's user avatar

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