What is the Z axis? What are they talking about here?

Question

Quote: Simply [digitally] flipping a picture horizontally won't produce the same image that you [visually in reality] see in a mirror. "Edit/flip horizontally" will reverse the X axis, yes, but a mirror preserves the X axis and inverts the Z axis. I've heard people ask, "When I hold up my right arm, why does the person in the mirror hold up their left arm?" The truth is that they don't. When you hold up your right arm, the person in the mirror holds up their Z-inverted right arm, which looks like a left arm. -Unquote (a post by somebody)

What does this mean?

Answer 1

This is a bit of stab but. I'll give it a try.



As you look at a mirror in 2D the X axis is left to right and the Y axis would be top to bottom. Neither of those would change in the mirror image. i.e If your right arm is 2 feet right of center in reality, it is also 2 feet to the right in the image. The same could be said for the Y axis (up and down of center).



The Z axis refers to the 3rd dimension. i.e If you are standing 6ft from the mirror, the image will appear to be 6 feet inside the mirror (12 ft apart) and therefore would be an inverted image of the reality.



Another way of explaining would be to draw a dot in the center of the mirror. Everything to the right of the dot would be a positive X (your right arm in both the reality an image are both positives). The same would be for the Y axis (everything up would be positive).



For the Z axis. The reality (you) would be positive 6 from the dot, while the image would appear to be on the other side of the dot and be negative 6.

Answer 2

Before I answer your question here is a little background info. Euclidean geometry deals with the x and y axis. The x axis refers to a line parralel (running the same direction) to the ground as though you put a level on it. The y axis then refers to a line perpendicular(90 degrees) to the x axis (like if you made a capital "L"and put one side on the x axis) while the other goes "straight up and down".

Now to answer your question. The "z" axis then is the direction away from and toward and is also perpendicular to both the y and z axis.

The quote about the picture isnt entirely acurate (as I see it anyway). The word inversion to means to change one axis with another (ussually x and y) but I would think that a z inversion would actually refer to making something appear to move backward rather than forward or vise versa.

Answer 3

The way this seems to me is that the mirror is the x,y plane and the z axis is protruding out of the mirror



when you see yourself in the mirror you are not flipping the image on the x,y plane you are instead flipping the image in the z plane



i.e image a horizontal beam floating in mid air and stretching away from you into the distance. You are flipping the beam end over end (like in a caber toss). The beam once flipped over once is the image you would see of the beam in a mirror. By flipping the beam over in this manner is the same motion as flipping an image in the z axis.



I may be wrong but this seems to me to be the only explaination.

Answer 4

It means that the reason we never like photos of ourselves is because the photo shows the way we really look! When we look in the mirror we are not seeing ouselves the way others see us. In three dimensional math, the x axis is horizontal, the z axis is vertical and the y axis is coming forward through the page. So if you reflect over the z axis, 3 becomes more like E.

Answer 5

Let's suppose you're looking into the mirror, and you're facing north.



Holding up your right arm, it's pointed east.



The y axis is up and down, The x axis is left (west) and right (east).



The z axis for you is toward the mirror (north) or away (south).



Up for you is still up for your reflection.

Pointing east for you is still pointing east for your reflection.

However, moving one step forward for you is moving north, while your reflection moving one step toward the mirror is moving south.

Answer 6

It's the third axis in the three-dimensional coordinate system.

Answer 7

yea what the guy above me said