Comment by gilgoomesh | Hacker News Reader

Comment by gilgoomesh | Hacker News Reader

The headline is deeply misleading.

This article is not about classical negative mass or exotic matter – which would be major breakthroughs.

https://en.wikipedia.org/wiki/Negative_mass

It is about "engineering" of the dispersion relation – wave-related phenomena that can have counter-intuitive effects at small scales where multiple waves interfere:

https://en.wikipedia.org/wiki/Dispersion_relation

In this case, the "counter-intuitive" effect is that the particles appear to move the wrong way when subjected to forces, resulting in an "effective mass" with a negative sign:

https://en.wikipedia.org/wiki/Effective_mass_(solid-state_ph...

The particles still have exactly the same (positive) mass, they're just moving the wrong way due to wave interference.

If you want to be super misleading... why not call it a "tractor beam"? They're applying a push force but the particle is moving towards the push.

As others have noted, the abstract for the paper correctly characterizes the phenomena as "negative effective mass". That word "effective" makes all the difference.

Even the first line of the article: "Washington State University physicists have created a fluid with negative mass, which is exactly what it sounds like."

"Exactly what it sounds like"?? Like...antigravity?? Reads further Ugh. Clickbait.

In classical physics there are 2 types of mass considered (and measured to be equal):

1. gravitational mass used in Newton's Law of Gravity

2. intertial mass used in Newton's Second Law

Measurements show that these two kinds of mass properties of an object are equal (are in linear proportion) to a very high precision. This was suspected and even Newton has considered and measured this, but the first really high precision measurements were done by baron Loránd Eötvös[1].

[1] https://en.wikipedia.org/wiki/E%C3%B6tv%C3%B6s_experiment

It's quite unfortunate that an official university news release seems to purposefully mislead its audience.

Or do they really just assume that no one cares about the difference? I find that hard to believe.

I suppose incompetence is also a potential explanation.

PhD comics really explains this pretty well:

http://phdcomics.com/comics.php?f=1174

I thought they did a video on the science/news cycle as well, but I can't seem to find it.

im sorry, but to me that comic doesn't explain it one bit. the university press in the comic doesn't (appear) to deliberately click-bait the headline, it seems to be a process in your example.

Washington State University appears to to have bypassed that process and gone straight for the misleading, click-bait title. This is disappointing because who better than the University Press themselves to try to provide as much clarity as possible. It's not like they don't have access to good sources...

The incentives of university's PR department aren't to provide accurate reporting on what's happening in said university to other scientists; it's to generate "buzz" around the university so that ultimately it gets more money. In this way, it's no better than regular news sources, and thus the quality is more-less the same.

But they also do have more of a reputation on the line. Universities are expected to be dignified institutions, moreso than your average news org I would think.

No model is 100% accurate. Especially when that model is a joke.

I don't claim to understand any of this, but it sure sounds like you are correct, looking at the terminology.

Someone had already added the paper to the "Negative mass" article, so I removed it:

https://en.wikipedia.org/w/index.php?title=Negative_mass&dif...

... And added it to the "Effective mass (solid-state physics)" article:

https://en.wikipedia.org/w/index.php?title=Effective_mass_(s...

The bit I removed from the "Negative mass" article said:

In April 2017, researchers at Washington State University claimed to have created a fluid with negative mass inside a Bose-Einstein Condensate.

I expanded it ever so slightly to read:

In April 2017, researchers at Washington State University claimed to have created a fluid with negative effective mass inside a Bose–Einstein condensate, by engineering the dispersion relation.

Slightly awkward, but hopefully at least a slight improvement.

PS: also added a "disambiguation" thingy at the top ("For negative mass in theoretical physics, see Negative mass."), now realizing it may be of dubious utility.

Thanks. Every time I see a university press release on HN I jump to the comments first, because there's always someone like you who's helpfully debunked the PR spin (no pun intended) to explain what's actually happening.

Thanks. Too bad it isn't real negative mass. How about imaginary number mass?

I thought you were joking, but I came across this:

https://en.wikipedia.org/wiki/Mass#Tachyonic_particles_and_i...

and was surprised that a plausible notion of imaginary mass exists.

Well being a layman, I had no idea if I was joking or not. :)

Actually the idea of negative mass made me wonder if this would open the possibility for FTL space travel...Ran into a comment on the internets somewhere that said "no, because the mass is squared in the relation with energy, but the existence of imaginary masses might"

Thanks for the link.

Many times people will see an asymptote and say "Hey, what would happen if I crossed that? What would the math and physics look like?"

Tachyons are actually a great example of this. Taking the relativistic mass equation and asking "What would happen if I allowed for speeds larger than the speed of light?" Science is more a process of elimination. What does the math say? Can we observe what the math says should happen? Repeat.

There should be some kind of voting mechanism on HN to automate what you did here (like a [hoax] flag) or something. I almost clicked on the bait but reading your comment clarified things. I was excited because this is a prerequisite of the Alcubierre (warp) drive: https://en.wikipedia.org/wiki/Alcubierre_drive

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