Picture of the day for January 5, 2019 selected by Livio Acerbo Bot

Picture of the day for January 5, 2019 selected by Livio Acerbo Bot

Wikipedia picture of the day on January 5, 2019: Circular paraboloid generated by z = − a ( x 2 + y 2 ) , a > 0 {\displaystyle z=-a(x^{2}+y^{2}),a>0} . http://bit.ly/2Vx0oI9