The legendary "Alcubierre drive" concept for faster than light travel relies on the existence of negative mass to work. Up until now, I have always read that it was generally assumed that negative mass could not exist, making the Alcubierre drive little more than a fanciful equation. But... I guess not.
Edit: although, it's not clear to me how significant a breakthrough this really is, compared with earlier attempts to create negative mass in a laboratory setting.
The term "negative mass" in the article does not mean the kind of stuff you would need to make an Alcubierre drive. That is a classical kind of "negative mass" (actually that term is somewhat misleading, the usual term is "exotic matter"). The "negative mass" in this article is a quantum kind of "negative mass", which is something different and does not have the properties of exotic matter. I've posted a link to the actual paper upthread.
The term 'exotic matter' means... exotic forms of matter. There are quite a few concepts which fall under the category, and the only thing they share is that they're all, well, exotic.
Negative-mass matter certainly fits in the category, but 'negative mass' is still a correct description.
> The term 'exotic matter' means... exotic forms of matter.
In General Relativity, it has a specific meaning: a substance that violates one of the energy conditions (usually the weak energy condition). That's how I was using the term, since that's what's required to make an Alcubierre Drive.
> Negative-mass matter
Meaning what? If you mean the Bose-Einstein condensate referred to in the article, no, it is not "exotic matter" by the GR definition.
General relativity isn't all there is to physics. If you check e.g. wikipedia (..I know, but eh), you'll find that the term has been used in cosmology (dark matter) and quantum mechanics as well. (Everything from strings to gravitons.)
Negative-mass matter is matter which could fit the 'exotic matter' definition you're using, though. Not the stuff in this article.
> General relativity isn't all there is to physics.
It's what's relevant to a discussion of the Alcubierre drive, which is what the post I originally responded to in this subthread was talking about. That's why I was using the GR definition of "exotic matter", as I've already explained.
> you'll find that the term has been used in cosmology (dark matter) and quantum mechanics as well. (Everything from strings to gravitons.)
Which term? "Exotic matter" or "negative-mass matter"?
I have not seen the term "exotic matter" used for any of these things in actual science textbooks or papers. Pop science sources might use the term colloquially to refer to all kinds of things, yes, but that just makes the term useless. Science tries to use precise definitions for a reason.
I have not seen the term "negative-mass matter" used at all in science textbooks or papers except when they explain why such a thing can't exist. So I don't know what you mean by this term if you're using it in any sense other than to refer to the Bose-Einstein condensate described in the WSU paper.
Edit: although, it's not clear to me how significant a breakthrough this really is, compared with earlier attempts to create negative mass in a laboratory setting.