Today, 40 years ago first public call with a cellphone was made. The cellphone weighed 2,5 pounds (1,1kg) and when it hit the market it would cost you little short of $4,000.
The periodic table is a tabular arrangement of the chemical elements, organized on the basis of their atomic numbers, electron configurations (electron shell model), and recurring chemical properties.
This is how our bellowed planet looks like on Martian twilight sky. It's the brightest point of light in the sky, and NASA's curiosity rover took a picture.
