1) The term "bull market" refers to a period of rising stock prices, while a "bear market" refers to a period of falling stock prices.

2) The Northern Lights, also known as the Aurora Borealis, are natural light displays that occur in the polar regions due to interactions between the Earth's magnetic field and solar particles.

3) The first computer mouse was invented by Douglas Engelbart in 1964 and consisted of a wooden shell and two metal wheels.

4) The word "country" contains three vowels: O, U, and Y.