A ghostly ribbon of stars reveals hidden dark matter - Science Daily

A collision may have left these galaxies without dark matter. That spells trouble for alternative gravity theories. The lack of dark matter in galaxies DF2, DF9, and DF4 (clockwise from left) was a shock to scientists, who speculate that they formed after an ancient collision.

Here’s what you’ll learn when you read this story:While many people have experienced encounters with what they think might be a ghost, studies trying to make sense of this scientifically have never found an explanation. Researchers compared accounts from three very different groups, looking for overlap. Spiritualists, extreme athletes, and psychiatric patients described strikingly similar ghosts, but no definitive cause emerged. Ghosts haunt our subconscious every Halloween. The living often wonder whether a hazy apparition, a sudden chill out of nowhere, or the echo of a disembodied voice might be coming from the spirit realm. Paranormal investigation shows aside, there has been no scientific way to prove this so far. They could be vestiges of the dead—or maybe they only exist in our imaginations. Perceiving ghosts is a phenomenon known as felt presence. Psychologists, neurologists, and neuropsychologists have tried to explain why people sense someone who isn’t there. Results are usually inconclusive. Sometimes, felt presence could be a side effect of bereavement or a hypnagogic illusion, which is experienced on the edge of falling asleep.