Egyptian policemen look-out from a police vehicle parked during the arrival of the body of nobel prize-winning Egyptian-American chemist Ahmed Zewail, at Cairo airport on August 6, 2016. Zewail, who served as a science and technology advisor to US President Barack Obama, died on August 6, 2016 in the United States. He was 70. / AFP PHOTO / KHALED DESOUKIKHALED DESOUKI/AFP/Getty Images

Dema Faham (C), the wife of nobel prize-winning Egyptian-American chemist Ahmed Zewail, arrives at Cairo airport to receive her husband's body after it arrived in Egypt on August 6, 2016 for his funeral. Zewail, who served as a science and technology advisor to US President Barack Obama, died on August 2, 2016 in the United States. He was 70. / AFP PHOTO / KHALED DESOUKIKHALED DESOUKI/AFP/Getty Images

Dema Faham (C), the wife of nobel prize-winning Egyptian-American chemist Ahmed Zewail, arrives at Cairo airport to receive her husband's body after it arrived in Egypt on August 6, 2016 for his funeral. Zewail, who served as a science and technology advisor to US President Barack Obama, died on August 2, 2016 in the United States. He was 70. / AFP PHOTO / KHALED DESOUKIKHALED DESOUKI/AFP/Getty Images

An ambulance transporting the body of nobel prize-winning Egyptian-American chemist Ahmed Zewail, leaves Cairo airport after his corpse arrived in Egypt on August 6, 2016 for his funeral. Zewail, who served as a science and technology advisor to US President Barack Obama, died on August 2, 2016 in the United States. He was 70. / AFP PHOTO / KHALED DESOUKIKHALED DESOUKI/AFP/Getty Images

An ambulance carrying the body of nobel prize-winning Egyptian-American chemist Ahmed Zewail, leaves Cairo airport after his corpse arrived in Egypt on August 6, 2016 for his funeral. Zewail, who served as a science and technology advisor to US President Barack Obama, died on August 2, 2016 in the United States. He was 70. / AFP PHOTO / KHALED DESOUKIKHALED DESOUKI/AFP/Getty Images

Garden of Light, an animation by Hexogon Solution of Singapore, is projected on the ArtScience Museum during a media preview of the i Light Marina Bay sustainable light art festival in Singapore March 7, 2012. REUTERS/Edgar Su/File Photo

DOLGARROG, WALES - AUGUST 05: Surfers ride a wave at Surf Snowdonia on August 5, 2016 in Dolgarrog, Wales. Surf Snowdonia is the world's first inland surf lagoon featuring pioneering technology which has made an Olympic dream a reality for British surfers. The International Olympic Committee (IOC) has announced its decision to include surfing in the Tokyo 2020 Olympics. The lagoon creates a perfect wave for surfers and was central to the inclusion of surfing in the Olympic Games. Surf Snowdonia will be crucial training facility for first ever surfing Team GB. (Photo by Christopher Furlong/Getty Images) *** BESTPIX ***

LONDON, ENGLAND - AUGUST 03: The Uber logo is displayed on computer screen on August 3, 2016 in London, England. (Photo by Carl Court/Getty Images)