there is no mistake about it,
it was a ghost!! Maybe you spilled something on the floor that has turned out to be luminous. Try covering the area with something lightproof for a couple of days, then remove the cover after turning the light off and see if it still glows. If it does, you may indeed have a ghost (but probably not).
No. It would be impossible to see the moon every night from her bedroom window. That's because the Moon moves every night.
An Apollonian circle is a diagram of two families of circles such that every circle in the first family intersects every circle in the second family orthogonally.
Every diameter of the circle.
a circle within a circle within a circle decrealsing in size every time
... center of the circle.
It is the center of the circle
If one is, they all are!
Every meridian of longitude on Earth crosses the Antarctic Circle, the Arctic Circle, and every other parallel of latitude on Earth.
Yes; the circle is a special case of an ellipse.
No, because the value of pi remains the same for any circle.
Pi is the circumference of the circle divided by the diameter of the circle. Every circle, that ever was, is, or ever will be.
That point is known as the "center of the circle". Every circle has one.