女生小视频

DDPTRF Hot air balloons at Balloon Fiesta in balloon fiesta Albuquerque, New Mexico, U.S.

Is it true that fresh air heats up faster than stale air? If so, why?

Readers weigh in on this one, debating everything from the meaning of 鈥渟tale air鈥� to its heat capacity

D73X1R An colorful adult midnight snapper swims over the reef

How do fish recognise others of their own species? Part 2

PF9N2P Honeybee stick on a window

Are flies following a strategy when they keep hitting a window? Part 2

This week鈥檚 new questions

D73X1R An colorful adult midnight snapper swims over the reef

How do fish recognise others of their own species?

Two scientists use a massive, illuminated periodic table of elements as they discuss the element holmium in the Lawrence Hall of Science at the University of California, Berkeley. (Photo by ?? Ted Streshinsky/CORBIS/Corbis via Getty Images)

How many known elements could we delete without ill effect? Part 2

H99WWH Low Angled portrait of a German Shorthaired Pointer dog.

This week鈥檚 new questions

What sized planet would make space travel impossible due to gravity?

W447EF hand is holding ice cream cone in front of a beach in Brittany, France

Why is ice cream so delicious?

A 3D illustration of the now debunked competing conspiracy theory that the Earth is flat, as it appears from land, rather than spherical. Earth texture maps courtesy of NASA.gov; Shutterstock ID 1240127368; purchase_order: -; job: -; client: -; other:

What would the horizon look like on a disc-shaped planet? Part 4

A reader has an important addendum to previous ponderings on this matter

This week鈥檚 new questions

Are there plants that could survive as a food source on the moon?

Are flies following a strategy when they keep hitting into a window?

When the sun engulfs Earth, will the remnants form new planets? Part 2