In recent days, A news was rolling over mainstream media that physicist observed ‘negative mass.’ Afterward, in a day or two, I came across an another headline, ” No, physicist have not created negative mass.” Confusing situation, right? And this popped up a question, physicists have created negative mass or not?
well, let’s first read what actually happened.
Prof Peter Engels (Washington State University) and his colleagues created a condition, in the lab, what we call a Bose-Einstein condensate. In order to do so, they cooled rubidium atoms to just above the temperature of absolute zero (close to -273C). For further process, as explained by BBC,
“To create the conditions for negative mass, the researchers used lasers to trap the rubidium atoms and to kick them back and forth, changing the way they spin. When the atoms were released from the laser trap, they expanded, with some displaying negative mass.”
In this context, negative mass is something that accelerates opposite to the applied force. As described by co-author Michael Forbes, assistant professor of physics at WSU, “With negative mass, if you push something, it accelerates toward you.”
So the matter was, not only media but the original paper also used the term ‘negative mass.’
Media headlines made the topic exotic and the news went viral, meanwhile famous physics debunk-blogger Sabine Hossenfelder would have encountered the news. She found it misleading and wrote a blog “No, physicist have not created negative mass.”
In her blog, she explained, “this paper reports the results of an experiment in which the physicists created a condensate that behaves as if it has a negative effective mass.” In addition, an another writer Ryan F. Mandelbaum explained Sabine Hossenfelder’s blog and wrote,
“The reason this phenomenon has the name negative effective mass is because of the equation used to describe what’s going on, explains Hossenfelder. If you look at the energy of the system and do a little calculus on it using the regular laws of physics, the mass term would be negative—but also dependent on other terms. Negative effective mass is not an innate property of the atoms themselves.”
According to the author of the paper, they created the negative mass but according to Sabine Hossenfelder what physicists have created is a negative effective mass. She later suggested an accurate headline for news,
“Physicists observe fluid not running apart.”
So, here are some sources, read them, and come up with your own explainable answer:
However, in my opinion, this was more ‘effective negative mass’ because it is a mathematical quantity which might hold negative values and the paper seems to be around this tricky fact.