‘Negative Mass’ Created at Washington State University

The headline is deeply misleading.<p>This article is <i>not</i> about classical negative mass or exotic matter – which would be major breakthroughs.<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Negative_mass" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Negative_mass</a><p>It is about &quot;engineering&quot; of the dispersion relation – wave-related phenomena that can have counter-intuitive effects at small scales where multiple waves interfere:<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Dispersion_relation" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Dispersion_relation</a><p>In this case, the &quot;counter-intuitive&quot; effect is that the particles appear to move the wrong way when subjected to forces, resulting in an &quot;effective mass&quot; with a negative sign:<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Effective_mass_(solid-state_physics)" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Effective_mass_(solid-state_ph...</a><p>The particles still have exactly the same (positive) mass, they&#x27;re just moving the wrong way due to wave interference.<p>If you want to be <i>super</i> misleading... why not call it a &quot;tractor beam&quot;? They&#x27;re applying a push force but the particle is moving towards the push.<p>As others have noted, the abstract for the paper correctly characterizes the phenomena as &quot;negative effective mass&quot;. That word &quot;effective&quot; makes all the difference.

First sentence of abstract: &quot;A negative effective mass ...&quot;<p>Maybe change the title from clickbait.

As usual with pop science reporting, they fail to give a link to the actual paper. Here it is:<p><a href="https:&#x2F;&#x2F;journals.aps.org&#x2F;prl&#x2F;abstract&#x2F;10.1103&#x2F;PhysRevLett.118.155301" rel="nofollow">https:&#x2F;&#x2F;journals.aps.org&#x2F;prl&#x2F;abstract&#x2F;10.1103&#x2F;PhysRevLett.11...</a><p>And here is the preprint on arxiv.org, for those who don&#x27;t have access to academia paywalls:<p><a href="https:&#x2F;&#x2F;arxiv.org&#x2F;pdf&#x2F;1612.04055.pdf" rel="nofollow">https:&#x2F;&#x2F;arxiv.org&#x2F;pdf&#x2F;1612.04055.pdf</a><p>TL&#x2F;DR: The substance in question is a Bose-Einstein condensate, which is not an ordinary &quot;fluid&quot; and should not be expected to be have like one. This is simply one of the counterintuitive effects of quantum mechanics showing up in an experimental setting.

The legendary &quot;Alcubierre drive&quot; 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.<p>Edit: although, it&#x27;s not clear to me how significant a breakthrough this really is, compared with earlier attempts to create negative mass in a laboratory setting.

This is true that the mass of the individual atoms in the BEC is a positive scalar and we only observe a collective behavior that acts like an object with negative mass. But, that engineered object (the wavepacket) is behaving like a negative mass. If we assume that everything that we measure in physics is collective (a subsystem of another - there is no such thing as an isolated system), we are not so wrong assigning that 1-D subsystem a negative mass. Let&#x27;s close with this question: How are we so sure that a &quot;positive&quot; mass of an object is not a collective interaction between the object itself and the rest of the universe?

I don&#x27;t understand the negativity here (pun intended). There&#x27;s an article and an abstract, both for different audiences. Every tech &#x2F; science article targeted towards layman people will have oversimplifications and here it seems good enough for me.

I&#x27;m looking at it from a lay scientist perspective with this. They&#x27;re blasting it with lasers, it&#x27;s internally unstable, things are flowing out of it, and evidence of negative mass is that it moved in direction different than expected. There&#x27;s a lot of variables here that might cause that movement that have to be eliminated. Maybe they have but experiments like this leave me uncertain about the outcome.<p>Note: Also, they should look for integer&#x2F;floating-point errors in the measurement code while they&#x27;re at it. ;)

Ok, no wormholes this time. But very cool anyway (literally too).

Yay we got a Mass Effect Drive and... oh, clickbait. Oh come on, this came from an university, we should expect better than that.

If there were really an object of negative mass, would its gravity (antigravity?) attract or repel objects with positive mass?

I&#x27;m guessing it doesn&#x27;t &#x27;fall&#x27; up instead of down?

Pics or it didn&#x27;t happen.