91色情片

Sprinters running on the athletics Track in sunset light. Shadows on the track, Sprint, Track and Field photo, original wallpaper for games in Japan, Tokyo. Athletics meeting on blue track; Shutterstock ID 2000844656; purchase_order: -; job: -; client: -; other: -

Did the running skills of our species help us outcompete Neanderthals?

Homo sapiens may have evolved good distance-running abilities, but Neanderthals were probably stronger and faster over short distances, which suited their hunting style, says one reader

Male nose close up bottom view - hair in the nostrils; Shutterstock ID 1895123341; purchase_order: -; job: -; client: -; other: -

This week鈥檚 new questions

BD5TB8 Alien and Older People, Cowes, Isle of Wight, England, UK, GB.

Could alien life forms live for hundreds or thousands of years?

H3NTB2 Woman by giant trees in snow-covered forest, Sequoia National Park, California, USA

Why don鈥檛 trees rot in the ground, while wooden structures do? Part 2

Last Word

What is this shape with three axes of symmetry called? Part 2

PE5P96 Close up of two purple socks with yellow lemon detail, pegged to a washing line with two yellow clothes pegs, shot from below against a clear blue sky

This week鈥檚 new questions

The events surrounding the Big Bang were so cataclysmic that they left an indelible imprint on the fabric of the cosmos. We can detect these scars today by observing the oldest light in the Universe. As it was created nearly 14 billion years ago, this light ???????? which exists now as weak microwave radiation and is thus named the cosmic microwave background (CMB) ???????? has now expanded to permeate the entire cosmos, filling it with detectable photons. The CMB can be used to probe the cosmos via something known as the Sunyaev-Zel????????dovich (SZ) effect, which was first observed over 30 years ago. We detect the CMB here on Earth when its constituent microwave photons travel to us through space. On their journey to us, they can pass through galaxy clusters that contain high-energy electrons. These electrons give the photons a tiny boost of energy. Detecting these boosted photons through our telescopes is challenging but important ???????? they can help astronomers to understand some of the fundamental properties of the Universe, such as the location and distribution of dense galaxy clusters. The NASA/ESA Hubble Space Telescope observed one of most massive known galaxy clusters, RX J1347.5????????1145, seen in this Picture of the Week, as part of the Cluster Lensing And Supernova survey with Hubble (CLASH). This observation of the cluster, 5 billion light-years from Earth, helped the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile to study the cosmic microwave background using the thermal Sunyaev-Zel????????dovich effect. The observations made with ALMA are visible as the blue-purple hues. Links ESO Picture of the Week RX J1347.5????????1145 seen by Hubble only

We know how matter took shape, but how was space formed?

Mass Product of Beer Bottles, Rows of glass production alcohol on industrial conveyor belt, top view.; Shutterstock ID 2416496749; purchase_order: -; job: -; client: -; other: -

Is the volume of gas at top of a beer bottle the same for all beers?

P2H56B Weasel standing upright, Mustela nivalis, Germany

This week鈥檚 new questions

Close-up of construction bubble level.

What does the angle of a spirit level mean relative to Earth?

Our readers explain that spirit (or bubble) levels indicate the direction of Earth's gravitational pull, though local variations are unlikely to make a practical difference for putting up shelves

Would a powerful solar storm knock out electronics in planes?

Is it possible to have a high-tech society without iron? Part 2

This week鈥檚 new questions

Does life require Earth鈥檚 rate of rotation to lie in a certain range?