The day is promoted by the AIDS Healthcare Foundation (AHF) in an effort to reduce the spread of HIV through safe sex practices.
Unlike regular clocks, atomic clocks are highly accurate, enabling scientists to use them to measure gravity.
The Mandela Effect describes false memories - mistakenly recalling events or experiences that have not occurred, or distortion of existing memories.
Palaeontologists believe the ancient trackway represents footprints of "adult, juvenile and infant mammoths".
From an outpost on the moon and build flying cars to funding cut for the international space station and earth science missions, the budget covers a lot of things
The moon is believed to have slowly distanced itself from the Earth at a time when the Sun shone around 30 percent less brightly than today.
Japan's KiKai Caldera was formed 7,300 years ago after a supereruption created a giant depression in the land.
The projected consequences of the rapid increase could lead to critical problems for major coastal cities around the globe.
Heartwarming image of Pikin the gorilla resting in the arms of her human companion Appolinaire in the back of a car wins Wildlife Photographer of the Year People's Choice Award.
Twenty Thelazia gulosa worms extracted from Mary's eyes over 20 days. Experts think cattle parasite picked up from Oregon ranch.
A panorama photograph of motorbikes in a World War Two shipwreck in the Red Sea has won Underwater Photographer of the Year 2018.
A team of researchers led by British Antarctic Survey is set to investigate a mysterious marine ecosystem hidden under an iceberg that's four times the size of London.
A man believed to be a poacher was attacked and eaten by a pride of lions close to Kruger National Park in South Africa.
Model Gigi Hadid has spoken out about how Hashimoto's disease has changed her body.
Met Office issues weather warnings for Scotland, Wales and the Midlands as cold spell is set to continue.
The ISS could be handed over to the private sector like a piece of real estate.
It will eventually stop tumbling, but that is not likely to happen for millions of years.
The clip is part of the second season of National Geographic's documentary series "Mars" scheduled to air in spring.
The craft will switch to software-based stellar navigation to conserve power and extend service life.
The launch, in which a Falcon 9 rocket will carry a 1350 kg Paz satellite and two 400 kg Starlink demo satellites into to a 514km Sun-Synchronous Orbit, is set for 17 February.