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Readers discuss dark energy, Ötzi's tattoos and sneaky plant invasions

Readers discuss dark energy, Ötzi’s tattoos and sneaky plant invasions

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Secrets of space

New data hint that dark energy’s density, commonly thought to remain constant, might vary over time, Emily Conover reported in “3-D map hints at dark energy’s secrets” (SN: 5/4/24 & 5/18/24, p. 6).

In the standard picture of the cosmos, the amount of dark energy is increasing as the universe expands. Reader Mark Granville wondered where new dark energy comes from.

Dark energy’s source is an enduring mystery. Quantum fluctuations in empty space, in which particles pop into existence for extremely brief moments, could be one explanation, Conover says. But these fluctuations yield even more questions. Some calculations predict that much more dark energy exists than researchers are observing in the universe, by 120 orders of magnitude, Conover says. Scientists still don’t know how to explain that discrepancy.

Feel the pain

Tattooing experiments suggest that the tattoos of Ötzi the Iceman, who lived 5,200 years ago, were hand poked, not sliced, into his skin, Bruce Bower reported in “How Ötzi the Iceman really got his tattoos” (SN: 5/4/24 & 5/18/24, p. 4).

Reader Amy Perry wondered whether the tattooing process was painful for Ötzi and whether pain relief measures were available.

Tattoos generally can be painful. The pain a person experiences depends on their pain tolerance, the tool and technique used, and tattoo size and placement on the body, says archaeologist Aaron Deter-Wolf of the Tennessee Division of Archaeology in Nashville.

Scientists can’t know for sure the level of pain Ötzi felt during the tattooing process. But the relatively small markings and his rugged lifestyle may mean that the tattoos did not cause him too much pain, Deter-Wolf speculates.

Whether Ötzi used pain relief for the tattoos is unknown. His mummified body was found with natural substances that have disinfecting and pain-relieving properties. Scientists think that the Iceman may have used these substances, which include bog mosses and a type of fungus called birch polypore, to dress wounds during his final days. It’s hard to say whether he applied the substances to his tattoos, which had long since healed, says Katharina Hersel, a spokesperson at South Tyrol Museum of Archaeology in Bolzano, Italy, where Ötzi is kept.

Sleeper species

Some invasive plants lurk for hundreds of years in a new location before choking out native species there, Susan Milius reported in “Plant invasions can take centuries” (SN: 5/4/24 & 5/18/24, p. 15).

Reader Christina Gullion asked if the lags are driven by genetic mutations that, over time, allow initially well-behaved invaders to thrive in a new environment.

This is one potential explanation, says invasion ecologist Shaun Coutts of the University of Lincoln in England. Previous studies have suggested that adaptations may arise and spread within an invasive population after it has arrived in its new home, Coutts says.

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