Scientists are fairly certain that the universe is filled with dark matter, the invisible stuff that exerts a gravitational pull on normal matter like stars, but physicists have struggled for decades to pin down its precise location and composition. At this point, physicists have ruled out the easiest candidates other than massless particles called neutrinos—they could only account for about 1 percent of dark matter. Most current and planned experiments are looking for either weakly interacting massive particles (WIMPs) or quantum chromodynamics (QCD) axions, particles even lighter than neutrinos, write theoretical physicists Tracy R. Slatyer and Tim M. P. Tait. 

Why this matters: Many physicists hoped that big, expensive experiments, such as the Large Hadron Collider, would yield an answer to the dark matter question, but so far, no such luck. A group of optimistic physicists recently agreed that the best approach going forward in the search for dark matter is to cast a wide net, relying on many small experiments, each sensitive to a different candidate for dark matter.    

What the experts say: Despite the lack of truly satisfying results to date, it’s hard to write off the existence of dark matter. “Most sophisticated attempts to formulate self-consistent theories of modified gravity to explain away dark matter end up invoking a type of dark matter anyway, to match the ripples we observe in the cosmic microwave background, leftover light from the big bang,” Slatyer and Tait write. 

People are more judgmental in the shoulder seasons (fall and spring) than they are in the summer and winter, an analysis of more than 230,000 survey responses from people in the U.S., Canada and Australia. Participants were asked to make right-or-wrong calls on topics concerning loyalty to one’s own group, respect for leaders and rules, and cleanliness and piety. Anxiety during seasonal swings could be behind the finding, says psychologist and study co-author Brian O’Shea, reports Anvita Patwardhan.

Why it matters: Seasonal variations in our thoughts about morality could affect jury-duty behavior, whether we get vaccinated and our voting behavior in elections.  

What the experts say: “One thing that this article is showing is that we are very seasonal creatures,” says psychiatrist Norman Rosenthal, who specializes in seasonal affective disorder.