News

  1. Physics

    Clocking gravity

    The first attempt to measure the speed of gravity finds it roughly equal to that of light, as expected, though not everyone agrees that the method used can actually measure gravity's speed.

    By Peter Weiss
  2. Earth

    Contraceptive ring could pose risks after its disposal

    Discarded vaginal contraceptive rings could interfere with fishes' reproduction by releasing estrogen into streams.

    By Janet Raloff
  3. Earth

    Snow alga may be sizable carbon sink

    A common microorganism that adds a reddish tinge to some patches of snow may be a significant consumer of planet-warming carbon dioxide.

    By Sid Perkins
  4. Health & Medicine

    Do liver stem cells come from bone marrow?

    Tests of liver tissue from people who've received liver or blood-marrow transplants show that stem cells in bone marrow can populate the liver as liver cells.