SOS, how is this possible? Scientists created a fluid with negative mass.

[BrianHG]

Scientists have created a fluid with negative mass? 

Scientists have created a fluid that exhibits the bizarre property of “negative mass” in an experiment that appears to defy the everyday laws of motion.

IE, you push on the fluid forward, said fluid accelerates toward you in reverse... 
How is this possible?

Article: https://www.theguardian.com/science/2017/apr/19/scientists-have-created-a-fluid-with-negative-mass-but-what-does-it-tell-us

Washington State University physicists have created a fluid with negative mass, which is exactly what it sounds like. Push it, and unlike every physical object in the world we know, it doesn't accelerate in the direction it was pushed. It accelerates backwards.

Article2: https://phys.org/news/2017-04-physicists-negative-mass.html

[Tomorokoshi]

First Kirchhoff's Laws, and now Newton's? What's next? Changing the Volt and the Kilogram?

[bd139]

https://www.cnet.com/news/scientists-are-about-to-redefine-how-much-a-kilogram-weighs/ 

[tpowell1830]

So, is this fluid trying to accelerate away from earth at a rate of 9.8m/s/s?

[tggzzz]

You have a helium balloon in a car moving forwards. The car decelerates.

Which way does the balloon move?

Ditto a balloon filled with carbon dioxide?

[BrianHG]

So, is this fluid trying to accelerate away from earth at a rate of 9.8m/s/s?

According to the end of the first article I listed, No.  Remember, gravity doesn't push or pull on objects, it's the objects just following the curvature of space-time itself.  Maybe in the case of artificial gravity due to acceleration, or rotation in spin gravity, having this fluid supported on a surface or platform which may be accelerating or rotating may cause a weird effect.

For instance, you might expect a ball with negative mass to be repelled from the Earth’s surface, but theory predicts that it would behave just like ordinary matter and fall downwards.

[tpowell1830]

So, is this fluid trying to accelerate away from earth at a rate of 9.8m/s/s?

According to the end of the first article I listed, No.  Remember, gravity doesn't push or pull on objects, it's the objects just following the curvature of space-time itself.  Maybe in the case of artificial gravity due to acceleration, or rotation in spin gravity, having this fluid supported on a surface or platform which may be accelerating or rotating may cause a weird effect.

Do you mean like the earth (rotating, moving through space)?

[BrianHG]

So, is this fluid trying to accelerate away from earth at a rate of 9.8m/s/s?

According to the end of the first article I listed, No.  Remember, gravity doesn't push or pull on objects, it's the objects just following the curvature of space-time itself.  Maybe in the case of artificial gravity due to acceleration, or rotation in spin gravity, having this fluid supported on a surface or platform which may be accelerating or rotating may cause a weird effect.

Do you mean like the earth (rotating, moving through space)?

No, like Babylon5 space station.  The internal gravity is artificial due to rotational centrifugal force even though there is no planet anywhere.  You feel gravity on that space station since you stand on the inside of a huge rotating cylinder where you are being pushed towards the outer edge as it rotates holding you to it's surface.  Hence, without a huge planet, you have artificial gravity.  (Yes, this is real physics though the TV show was fictional)

I'm saying a negative mass fluid siting on the internal surface of this space station would not behave the same way as all other matter.  My guess is that it either would be double weight, or, keep bouncing off, flowing in reverse to rotation from the surface in an ever growing accelerating fashion.

[BrianHG]

You have a helium balloon in a car moving forwards. The car decelerates.

Which way does the balloon move?

Ditto a balloon filled with carbon dioxide?

Looks like you've created a sort of equivilant effect with the helium balloon being lighter than the surrounding air.
Your example is such a simple explanation, I wonder why the physicists didn't use your analogy.
I'm having difficulty applying this to a push on the fluid in a vacuum where the push to the fluid is like: (Actual Quote) “It looks like the rubidium hits an invisible wall.”

[SiliconWizard]

https://www.cnet.com/news/scientists-are-about-to-redefine-how-much-a-kilogram-weighs/ 

Yes, spot on. This is a work currently in progress.

[T3sl4co1l]

It's not possible.  It's a lie to attract clicks.

A BEC is about as far removed from common experience as you can get.

Calling it a "fluid" in that sense, is precisely as disingenuous as any reporting on quantum physics inevitably is.

Basically they've created a system that exhibits negative group velocity, an unusual but not unheard of condition, say with electromagnetic fields.  It's just been done with condensed fermions, which pair up to form a bosonic state, where the same boundary conditions can be applied to give the same result.  (Extrapolating from my knowledge of these things, anyway.  Read the paper if you need the actual theory.)

Tim