October 15, 2024
3 minimum read
Lucy turns 50 and dark energy becomes even more mysterious
What works to improve health equity? And it may be time to end leap seconds
Something strange is happening with dark energy. It’s strange enough that we know so little about it. “Dark energy” is the name of an unknown force that is constantly expanding the universe at a faster rate. No one has been able to directly detect dark energy. We can only measure its effectiveness. And one of those measurements is a little off. The Hubble constant represents how fast the universe is expanding. By measuring the distance to a supernova, physicists estimate its value in the nearby universe.
The problem is that these estimates of the Hubble constant don’t match what the Standard Model of cosmology predicts, based on patterns in the cosmic microwave background radiation, the glow left over from the early universe. This discrepancy has become more pronounced in recent years as observations from the Hubble Space Telescope have been based on more accurate observations from the James Webb Space Telescope (and measurement errors less likely).
So did dark energy change over the course of the universe? Did an additional “initial dark energy” force give the universe more vitality shortly after the Big Bang? Theoretical physicist Mark Kamionkowski and celestial bodies Physicist Adam G. Reese has been working on this “Hubble tension” problem since the beginning. They explain the problem and possible solutions more clearly and interestingly than I’ve ever seen them (aided, as always, by great graphics).
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of Australopithecus afarensis This fossil, affectionately known as Lucy, is one of the most important discoveries in the study of human origins. She was discovered 50 years ago and immediately changed our understanding of how we became humans. Her discoverer, Donald C. Johansson, and paleoanthropologist Johannes Haile-Selassie, who has discovered many other important human ancestors, are studying these precious fossils to learn more about the human brain, locomotion, Share what you’ve learned about habitat, diet evolution.
The Earth’s daily rotation has slowed down over time. When dinosaurs roamed the Earth, a day was only 23.5 hours long. This consistent reduction in velocity is primarily due to friction. The moon’s gravitational pull causes ocean tides, and the friction of the ocean sliding across the ocean floor slows the entire system. Inside the planet, the rotational speed increases slightly due to the flow of the liquid outer core. And global warming is also changing the dynamics of the Earth’s rotation, as ice melts and water moves from the poles toward the equator. It’s a mess. We have been adding “leap seconds” over the years to synchronize our atomic clocks with changes in the Earth’s rotation. Senior editor Mark Fischetti, who works with infographic designer Matthew Twombly, asks whether it’s time to just leave clock time and planetary time alone.
Vaccines given through a bump in the nose or into the mouth may be even more effective than injections at protecting people from respiratory illnesses (and they don’t involve needles). Science journalist Stephanie Sutherland covers advances in nasal vaccines and why scientists are excited about them.
In this issue, we publish our third annual special health equity package focused on solutions. Here are some highlights: Vaccines are one of the most life-saving interventions in human history. People working in rural areas have devised innovations that improve health care for all. Breaking down improperly compiled data can save lives. Medical devices and algorithms are being corrected for historical biases. And we spoke to some global health experts about what gives them hope for the future. We hope you find this collection inspiring. scientific american.