Why objects turn around only one axis?
407938
It is a factor in their formation. As matter gravitationally comes in proximity with other matter, the "pieces" start orbiting one another. As other pieces join the group, they influence all the other pieces in the group simultaneously, so the whole set of objects tends to change it's axis of rotation as a group. In the end, there is a cluster of objects that all tend to rotate within the same general plane or around the same axis of rotation.\n\nFor example, most of the planets in the solar system rotate on an axis that is very similar to their axis of revolution around the sun. This is because the "pieces" of mater that formed the solar system started rotating around (orbiting) one another in a single plane. As some of the pieces crashed into one another and combined into planets, stars, etc. some of the orbital energy was transformed into rotational energy, but with angular momentum in the same direction as the rotational energy. Thus revolution and rotation are generally in the same direction with similar axes.
87418
Any object which you can turn upside down and it looks exactly the same as before you turned it has point symmetry. The order of point symmetry deends on how many different types of simultaneous rotations result in an identical figure. For example, any figure that can be turned about a point 180 degrees and land on an image of itself is said to have point symmetry and rotational symmetry of order 2. A 2 dimensional image of a soccer ball has point symmetry for example.
61467
The moon spins about an axis. The axis  is almost perpendicular to the plane of the moons orbit around the earth. The period of spin (time to complete one rotation about the spin axis) is equal to the period of one revolution around the earth.\n  The result is we see one side of the moon.\nFor many people this answer is not suffice to understand.\nImagine a cubical building in a plain ground. The four vertical walls are marked A,B,C,D.  Imagine the building to be the moon and we are standing infront of the wall marked A. Let us go round the building to see the other walls in the order of ABCD. When we have finished quarter round we can have the full view of the wall B. But imagine  that the building rotates itself such that when we finished quarter round it also has rotated quarter round about itself. We will see only the wall A. If the things continue like this we can never see the other walls.When we complete one round the building completes one round so always we see only the wall A.\n Due to librations actually we can see 59% of the moon instead of 50%
819927
All objects react as if there were only a single force acting upon them. Let's say an object on your desk had a force of ten newtons pushing it to the east. Let's call that force positive 10 newtons. According to Newton's second law, it would accelerate (pick up speed) moving in an eastward direction. It had a single force acting upon it and since there was no opposing force we say that it was an unbalanced force. Now say the same object had another force of 10 newtons acting on it in a westward direction. Lets call that force negative 10 newtons. Now we have two forces and since they are equal but have opposite signs the algebraic sum is zero ([+10N] + [-10N] = 0). We now have balanced forces - equal but opposite. Remember I said that all objects react as if there were only one force acting upon them? Even though there are two forces acting in opposite directions on the object on your desk, that object reacts as if there were only one force acting upon it - a force of zero newtons. BTW, that sum force is called the resultant. So according to Newton's first law since a zero force is applied to the object it will remain at rest. In short, unbalanced forces result in movement, balanced forces don't.
753244
Think of the wheels as spinning masses or revolving weights, in fact gyroscopes. \nEach wants to turn left or right while spinning but is constrained by it's axis,\nHowever both drift overtime.\nNow add another pair further back and wider apart, and this pair are not on the same line of travel.\nWith four wheels all wanting to drift the resultant direction becomes a straighter line.
108530
Not all the planets do rotate on their axes with constant angular velocity (see reference) and even two rotate in the opposite direction to earth (counter clockwise when viewed from the celestial north pole); venus and uranus (called retrograde motion). \n\nThe rough alignment of all the angular momentum vectors in the solar system, including orbital and rotational angular momenta of all the planets, moons and the sun is presumably a left over relic from the angular momentum when the system was formed from a rotating gaseous collection of material.
1017458
symetric properety...\n\n\nok heres why.....\n\n(pretend the equal signs are parallel line segments)\n\n===========================\n\n\ndo you see how you can split them dont the middle, thats called the symetric property
636329
I like to use GraphCalc, as it also includes live rotation of 3-D graphs. See http://www.graphcalc.com/ .
771669
Cause squares would look weird
59556
It's due to the formation of the planets themselves.  the gases and the dust spun around the sun as the star formed itself, and congealed into the planets we know.  And since they spun as they formed, they started the spinning on their axis as well.  \n\nBesides, we'd be either cooked or frozen if the Earth didn't revolve!\n\nHarley's wrong.  The moon DOES spin on an axis.  However, its spinning is on par with the Earth's spinning, thus you only see the one side of the moon.
1107490
Depends which axis you're talking about.  If the letters were three dimensional objects instead of written on a page, there would be three axes that you could rotate about.  \n\nExtend your index finger straight out, extend your thumb straight up, and extend your middle finger perpendicular to the index and thumb.  That gives you three 'axes', all perpendicular to each other.  Your index finger could be the x, your middle finger the y, and the thumb the z (that would be pretty standard orientation for a coordinate system).\n\nIf the x-axis comes straight out the front of the letter, then the z-axis would come straight out the top, and the y-axis straight out the side.\n\n'A' does not have symmetry when rotated about the X-axis; it would be upside down.  The other three do have symmetry.\n\n'A' and 'N' do not have symmetry when rotated about the Y-axis; they would be upside down. The other two do have symmetry.\n\n'N' does not have symmetry when rotated about the Z-axis; it would be backwards.  The other three do have symmetry.\n\n'X' and 'O' are the only two letters with symmetry about all three axes.
1054447
I had this happen once (thanks to my two year old playing with the computer).  The way I fixed it was to right click on the desktop and choose Graphics Options.  Then chose Rotation and set it back to Normal.  I am using Windows XP Home Edition.  I hope this helps!
805080
Feymann saw particles (ex. electrons) as traveling forward in time,  thus the arrow goes from left to right, and positrons or other antiparticles to be "like a particle traveling back in time," thus it goes right to left. \n\nIf axis is defined as y = time and x = position, particles would have an arrow pointing upwards, and antiparticles would have an arrow pointing downwards.
1070746
It has something to do with a mysterious underlying mathematical principle. Generally, functions are curved. Laws of nature obey simple mathematical formulas. When averaged together, round shapes are formed.
837255
its the point which you are rotating the object around
123394
It's called the axis.
452210
Egads.  It's been quite awhile.  I remember some papers at SIGGRAPH a decade or so ago on this topic.\n\nAlright, here's a stab at the explanation.\n\nWith Euler mechanics or Euler angles, there are three reference angles: yaw, pitch, and roll. It is possible to rotate an object using these three reference angles such that two line up causing the inability to do an arbitrary rotation.  Say you roll to the right 90 degrees and this lines up the yaw axis with your pitch axis -- gimble lock results.\n\nWith quaternions, you don't have three reference angles.  You have only one plane and an arbitrary axis of rotation.  Each move creates a new plane and axis of rotation.  As such, there are no additional axes of rotation with which to collide because there is only one axis of rotation and it's position is arbitrary where as with Euler angles, the reference angles are fixed.\n\nI don't know if I've done it justice, but maybe this explanation and the references below will help you stitch together an understanding.