Pinning a gyroscope will resist change in orientation

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Discussion Overview

The discussion revolves around the behavior of gyroscopes in relation to orientation and the effects of Earth's rotation and gravity. Participants explore whether a gyroscope maintains its orientation in an absolute sense or relative to Earth's center of gravity, and how this relates to practical applications like navigation.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions whether a gyroscope's orientation is absolute or relative to Earth's center of gravity, considering scenarios of moving to different locations on Earth.
  • Another participant asserts that the gyroscope maintains an "absolute direction," implying it points in the same direction regardless of location.
  • A participant raises the question of how gyroscopes used for navigation compensate for Earth's rotation and orbit.
  • It is suggested that gyroscopes are designed to remain unaffected by Earth's motion, allowing devices like gyrocompasses to maintain alignment with Earth's axis.
  • Concerns are expressed about the limitations of gyroscopes over longer time scales, noting that they tend to drift and require correction using other instruments.
  • One participant discusses the ideal conditions for a gyroscope's performance, emphasizing that real-world imperfections, such as friction, can introduce torque that alters its orientation.
  • Another participant mentions that a compass, which is free to float, can still function effectively even if not perfectly aligned with the Earth's axis.

Areas of Agreement / Disagreement

Participants express differing views on whether a gyroscope's orientation is absolute or relative, and while some agree on the principles of gyroscope functionality, there is no consensus on the implications of Earth's motion on gyroscope behavior.

Contextual Notes

Participants note that real-world conditions, such as friction and torque, affect the ideal behavior of gyroscopes, indicating that practical applications may deviate from theoretical expectations.

Who May Find This Useful

This discussion may be of interest to those studying physics, engineering, or navigation technologies, particularly in understanding the principles and limitations of gyroscopic systems.

Gelsamel Epsilon
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I know when spinning a gyroscope will resist change in orientation so that the rotor is still pointing in the same direction.

But, is that direction with respect to Earth's center of gravity or is it an "absolute direction".

So, if I point a gyroscope upwards and spin the rotor and I go directly to the otherside of the Earth would the rotor be pointing downwards or will it be pointing upwards still?

Also, if I spun a gyroscope for a day, would I see it change direction (with respect to my reference frame) with Earth's rotation?

And if I spun it for a year would I see it change direction (again with respect to my reference frame) along with Earth's rotation and orbit?

Considering these questions my guess is it stays in the same direction with respect to Earth's Center of Gravity.
 
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It's an "absolute direction" kind of thing.
 
So assuming the rotor is spinning forever regardless of where I take it in the universe it will always point in the exact direction that I started spinning it at?

If that is the case then how do things which use gyroscopes to determine direction compensate for the Earth's spin and orbit?
 
That is how they compensate. That's the whole point of the gyroscope - that it isn't affected by the Earth's spin and motion. For example, a gyrocompass on a ship has its axis aligned to the Earth's axis and it stays that way, regardless of which way the ship is pointed or the Earth moves (the Earth's axis doesn't move either, for the same reason), enabling the ship to know its direction.
 
Ah, I see how that works.

Though if it isn't aligned with the Earth's axis it would not work well as a compass?
 
You normally use gyroscopes for short time scale things, like acrobatic maneuvers. Over longer time-scales, most gyroscopes tend to slowly "drift" and need correcting anyway (say using accelerometers, or compasses perhaps.. in which case the slow daily rotation may be removed then).
 
Is that simply because real world is not a "perfect world" situation?
 
Gelsamel Epsilon said:
Is that simply because real world is not a "perfect world" situation?

It is because the "gyroscope pointing in the same direction" is only correct if no torque is applied to the gyroscope (that is, a perfect gyroscope is an axially symmetric rigid body that has a fixed point, lying on its axis of symmetry, and is totally free to rotate about that axis, without undergoing any external torque wrt to that fixed point). The suspension of a gyroscope always includes some form of friction or so, which induces a very small torque on the gyroscope, and can slowly alter the direction in which it points.
 
Thanks for the info guys. :-)
 
  • #10
Gelsamel Epsilon said:
Ah, I see how that works.

Though if it isn't aligned with the Earth's axis it would not work well as a compass?
The compass is free to float (IIRC, it is suspended magnetically), so it still works if it isn't aligned quite perfectly. Ships keep logs of their compass error and check it daily against the sun.
 
  • #11
'How It Is Made' on Discovery had a segment on the construction of a marine gyroscope a while back. It's quite amazing how complex it is.
 

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