Questions tagged [rotation]

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

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82
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6answers
6k views

Does the Sun rotate?

The planets rotate as an after effect of their creation, the dust clouds that compressed span as they did so and the inertia has kept it rotating ever since. It's fairly easy to prove that planetary ...
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1answer
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Why does the Sun have different day lengths, but not the gas giants?

The Sun's rotation period varies from about 25 days at the equator to about 38 days at the poles. As I understand it, this is because the Sun is not solid, and because of the way centripetal force ...
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Why do (most of) the planets rotate counterclockwise, i.e. the same way the Sun does?

Referring to the mechanisms explaining the solar system formation and to the initial rotation of the gaseous cloud that collapsed, I understand easily why the planets orbit the Sun the same way this ...
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2answers
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What is the current accepted theory as to why Venus has a slow retrograde rotation?

According to this NASA overview, the planet Venus is unique (amongst the major planets), Venus has a slow retrograde axial rotation, taking 243 Earth days to make one rotation (which is longer than ...
23
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2answers
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Why does the Earth have a tilt of ~23°?

Is there a reason that the Earth has the tilt that it does (~23°)? How do we know which way is supposed to be 0°? Does this tilt have major consequences on the planet? Has it changed and will it ...
22
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1answer
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What is the accepted theory as to why Uranus' axis is tilted so severely?

The planet Uranus is another solar system anomaly, where according to the NASA profile has an axial tilt of 97.8 degrees, also considered to be retrograde. This NASA summary "Uranus" suggests the ...
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2answers
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How did Mars come to have a 24 hour 39 minute day?

Mercury rotates three times for every two revolutions around the Sun, apparently due to a gravitational resonance with the Sun.Venus takes about 225 days to rotate, and rotates in the opposite ...
20
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1answer
837 views

Is Earth's orbital eccentricity enough to cause even minor seasons, without axial tilt?

I was reading the answers to this question about an exoplanet having seasons without axial tilt, and several responders mention that orbital eccentricity could cause a similar effect, but that the ...
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3answers
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Why does a planet rotate and revolve?

Why do planets rotate and revolve in the universe?
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Official degrees of earth’s rotation per day

What is the official degree to one decimal point please, of the earth’s rotation in one single day. Can it be confirmed that it is exactly 360.0 degrees using official data? Thank you in advance.
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Why don’t we feel the Earth rotating beneath us?

I’m not sure all of the details in the experiment but basically it went as follows. Someone marked their location of take off in a hot air balloon and went straight up in the air. They stayed ...
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Shape of neutron stars

I've heard that the more an object spins, the less of a true sphere it is. Using this logic most of neutron stars would be far from spherical,in general what shape are most neutron stars?
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What is the evidence that galaxies rotate?

Do all galaxies rotate? If so, do they rotate in the same direction? What observations have been made of galaxy rotation?
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Would an exoplanet without axial tilt have no seasons?

Would an Earth analog exoplanet which rotates around a solar analog, but without axial tilt, have no seasons? Would it be similar to how Los Angeles does not have very noticeable seasons compared to ...
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How can we avoid needing a leap year/second?

Given the Earth's current speed around the sun and current rate & axis of rotation, what is the best way to keep time to avoid a leap year? How many hours should we have in the day and days in a ...
12
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3answers
177 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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Why isn't Earth a perfect sphere? [closed]

In general, almost everyone describes Earth as an perfect sphere, but in reality it isn't a perfect sphere. Is there any specific reason why Earth is not perfect sphere ?
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Why is twilight longer in summer than winter and shortest at the equinox

I recently decided to set my alarm clock to wake me up when it is "dark" out. In the end, I decided to set my clock to the earliest time that nautical sunrise is in my state (Illinois) and stick with ...
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How can the Earth's rotation speed up? [closed]

It is known as a fact that Earth's rotation is slowing every year, that's why we sometimes have 61 seconds long minutes. In the Java documentation of Time : http://docs.oracle.com/javase/7/docs/api/...
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2answers
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How do we know that an exoplanet is tidally locked to the parent star?

Often in discussing exoplanets we hear that they are close to the parent star (usually a red dwarf) but then there's a caveat that the planet is tidally locked to that star and that that fact severely ...
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2answers
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If Earth didn't rotate, would we feel heavier? [closed]

Suppose the Earth's rotation slowed for some reason. Would the lack of centrifugal force cause us to feel heavier than normal? Likewise, if Earth's rotation increased, would we feel lighter as ...
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1answer
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How would Earth's climate differ if it's axis were tilted around 90 degrees like Uranus? [closed]

As the title states, what would the effect on Earth's climate be if it's axis were tilted approximately 90 degrees like Uranus? I'm specifically wondering about the effects on seasons, temperature, ...
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Do solstices and equinoxes shift over time?

Right now, I think the winter solstice is around December 21. Has it always been around this date constantly? Since the earth's axis's 23.45° tilt will be on the exact opposite side in 13000 years (...
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2answers
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Cancelling out earth rotation speed, Altazimuth mount

I have a Dobsonian telescope. It is using Altazimuth mount. Basic idea of using it is to target the object by moving telescope vertical axis perpendicular to the ground, and an elevation axis that ...
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550 views

Why do planets tend to rotate in the same direction although they have formed from tumbling asteroids?

The axial tilts of asteroids seem to vary randomly (let me know if this premise is wrong), while the planets have a strong tendency to rotate in the same way. If planets were formed by colliding ...
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Why do certain moons have their rotational period equal to their orbital period?

Our moon and Saturn's moon, Titan, have this feature. Because of this we only observe one side (hemispere) of our moon. Why is this? What is the Newtonian or astrophysics that would explain this? ...
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1answer
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How a star's rotation affects a star in the main sequence?

I searched and have found that the questions mainly focus on neutron stars, white dwarves and black holes. This was not what I looked for. Basically, the bigger the star's mass is, the more intense ...
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Did we ever actually see the earth revolving around the sun? Is the geocentric model completely disproved?

Did we ever actually see the Earth revolving around the Sun? Also, is the geocentric model completely disproved or was it sidelined because the heliocentric model made things easier to understand? (...
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2answers
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Decreasing rate of Earth's rotation: where does the power go?

I understand from Wikipedia that, "The length of the day, which has increased over the long term of Earth's history due to tidal effects, ...". If the angular velocity of the earth is decreasing then ...
8
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1answer
685 views

Can one detect from earth that angular momenta of its axial rotation and its orbital rotation are “almost parallel”?

I mean that the angle between these angular momenta is acute as opposed to obtuse (23.5 and not 180-23.5), so that the rotations are "roughly in the same direction". Related but distinct question -- ...
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What is the fastest spinning rotation of a Neutron star?

What is the fastest spinning rotation of a Neutron star? I have heard that Neutron stars have a specially fast spinning rotation. What is the fastest?
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1answer
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What is the difference between the Yarkovsky effect and YORP effect?

As far as I understand, both the Yarkovsky effect and the Yarkovsky–O'Keefe–Radzievskii–Paddack (YORP) effect exert forces upon bodies as a result of thermal photon radiation. How do both effects ...
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1answer
272 views

Which celestial object in the solar system has the fastest tangential velocity at its surface?

Consider all of the naturally-occurring objects in the solar system : in the reference frame of the object's center (ie, ignoring the orbital velocity around the sun or, in the case of satellites, ...
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Are there any known planets whose axis is oriented such that one pole always faces its star?

Earth rotates around the sun and around its axis (A North, South axis) giving us days, nights and seasons. Are there any known planets that rotate with an axis pointing toward its sun so that one ...
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2answers
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Why do Uranus' and Pluto's moons orbit the equator? What makes a moons' inclination tilt with the rotational axis of their planet?

Uranus and Pluto have their axes of rotation almost 90 degrees towards the ecliptic. But why do their moons tilt the same way? Does it mean that their tilts were caused by passing near some external ...
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2answers
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Could the merger of two rotating black holes create another that breaks the rotational speed limit?

The black hole GRS 1915+105 was observed to be spinning at near the theoretical maximum spin rate. Assuming you had two such black holes spinning clockwise, and also orbiting each other clockwise, ...
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Is the Sun prograde or retrograde with respect to the rotation of the Milky Way?

I recently learned about the terms prograde and retrograde. I've seen these terms used to describe the rotations and orbits of moons with respect to their planet, and planets with respect to their ...
6
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1answer
358 views

Earth and ferromagnetism [closed]

Earth's core is a giant liquid iron ball actually. If I know well, the magnetic field of our planet (that protects the surface from some particles comes from the Sun) can exist because as Earth ...
6
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2answers
547 views

Is axial tilt critical for life?

According to this explanation at the Georgia State University website, Axis Tilt is Critical for Life . . . The Earth's spin axis is tilted 23.5° with respect to the ecliptic, giving ...
6
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2answers
342 views

Does rotation affect gravitational lines of force

I was reading about rotating pulsars and other more-massive objects spinning at absurd speeds (hundreds of revolutions per second), and there was one point of which I was not clear. Does a rotation ...
6
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1answer
174 views

Are there collected data about the direction of rotation of black holes and the direction of the magnetic field?

Is there a relation between the direction of rotation of black holes or neutron stars and the magnetic dipole moment of BH or neutron stars? BTW, are there different directions of this two parameters ...
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3answers
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How is a day measured on a gas giant?

After watching this JPL video of a Cassini time lapse of Saturn, I wondered since being mostly gases, how do we know how long a day—one rotation period—is? Is there a usable relation between how fast ...
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2answers
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Why do our clocks not go out of sync with the day over a year?

Ok, so our clocks time 24 hours, our planet takes 24 hours to rotate completely and our planet revolves around the sun in 365 days. Imagine at the start of the year, the side of Earth facing Sol is '...
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1answer
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Why is Earth's rotation considered fast?

I'm currently reading Atom (Krauss book), and in chapter 11 there is this text: This collision can explain many things, including the high rate of spin of the Earth (the grazing collision would ...
5
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1answer
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How can a rotation period of a planet's satellite/moon be “chaotic” (like Hyperion around Saturn)?

According to wikipedia (see info below image) Hyperion's rotation period around Saturn is "chaotic". What does that mean? The period (in days/hours) is different every rotation without any law ...
5
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2answers
710 views

Why most planets don't spin retrograde? [duplicate]

Edit: just found duplicate Since orbital velocity is greater on small orbits, and smaller on large orbits, why don't planets spin retrograde around their own axis? One portion of planet's mass is ...
5
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2answers
608 views

How does the dense atmosphere of Venus affect the planet's rotation?

Reading through questions about my favourite planet, Venus, I came across this answer to the question What is the current accepted theory as to why Venus has a slow retrograde rotation?, specifically ...
4
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1answer
119 views

What is a black hole's “shadow” and the best angle to view it to measure the spin?

This excellent answer mentions several ways to try to observationally measure the spin of a rotating black hole. The third one is intriguing, but I don't understand how this works: The spin of a ...
4
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2answers
687 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 ...
4
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1answer
4k views

What causes objects to become tidally locked?

I'm trying to write a gravity simulation (suns planets etc), and was hoping tidal locking could be one feature demonstrated. Using a simple equation for gravity has produced some interesting results, ...