The Dark Energy Survey (DES) created a map of 26 million galaxies, the biggest map of the Universe to date, by charting the distribution of matter across the cosmos, per Nature's Davide Castelvecchi. The data from the map has since revealed that the Universe may have less clumps of matter than cosmologists previously thought.

Why it matters: "If confirmed, this gap could mean that mass has been clumping at a lower pace than predicted, potentially revealing new physics," writes Castelvecchi. "For example, it could point to unexpected interactions between dark matter and dark energy, or to new types of neutrinos."

Background: Castelvecchi explains that when the Universe was created roughly 14 billion years ago, matter was spread evenly across it, making it "extremely smooth." As time has passed, cosmologists have found that mass has been "clumping together" into galaxies, stars and other entities at a consistent rate — but now DES' latest data has led scientists to think the clumping may have happened more slowly.

Limitations: DES' findings were based on photos of the Universe produced by measuring "the cosmic microwave background" or as Castelvecchi calls it, "the afterglow of the Big Bang." Survey leaders note that the technique is still "within the margin of error" but add that their data has helped them become a major competitor in the cosmology research field. Note that the DES results have not yet been peer-reviewed, but were presented at a meeting Thursday with the American Physical Society at Fermilab.

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Biden releases 2019 tax returns ahead of debate

Photo: Alex Wong/Getty Images

Joe Biden's campaign released his 2019 tax returns on Tuesday, showing that he and his wife, Jill, paid nearly $300,000 in federal taxes last year.

Why it matters: The release, timed just hours before the first presidential debate, comes days after a bombshell New York Times report said that President Trump paid only $750 in federal taxes in 2016 and 2017. Biden's team is hoping to make the tax contrast a sticking point during their showdown.

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Coronavirus dashboard

Illustration: Sarah Grillo/Axios

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  4. States: NYC's coronavirus positivity rate spikes to highest since June.
  5. Sports: Tennessee Titans close facility amid NFL's first coronavirus outbreak.
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NYC's coronavirus positivity rate spikes to highest since June

New York Mayor Bill de Blasio. Photo: Noam Galai/Getty Images

New York City's coronavirus positivity rate has ticked up to 3.25%, its highest since June, Mayor Bill de Blasio said at a news conference on Tuesday.

Why it matters: The jump — from 1.93% on Monday — came on the first day that public elementary classrooms reopened in the city after months of closures, but guidelines state that all public schools will have to shut if the citywide seven-day positivity rate stays above 3%.