1) 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.

2) The first graphical web browser, Mosaic, was released in 1993 and played a key role in popularizing the World Wide Web.

3) The Mona Lisa, painted by Leonardo da Vinci, is one of the most famous and valuable artworks in the world.

4) The world's oldest living plant is believed to be a clonal shrub called "Old Tjikko" in Sweden, estimated to be over 9,500 years old.