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Comment by lmkg | Hacker News Reader

Very interesting thought experiment, and it certainly seems to make some exciting postdictions. However, before accepting it, I would need to see what happens with negative inertial mass. Recall that, unlike electric charges, mass has a second role in physics beyond its interaction with one of the four primary forces. Specifically, it's the relation between force and acceleration. General relativity is founded on examining the connection between gravitational mass and inertial mass. If a body has negative gravitational mass, does that mean that it has negative inertial mass as well? Would this mean that if you apply a force on such a body, it accelerates in the opposite direction?

Also, regarding the astronomer that hung up: maybe he's gotten a lot of calls from pseudo-science cranks, and the author sounded like one on the phone. I can understand not wanting to waste your time on that.

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He specifically answers the concern about negative inertial mass!

He proposes that to make negative mass make sense with regard to inertia, the equation F = ma should actually have been F = |m|a.

He does not answer the concern, he just throws down absolute value bars to make all inertia work the same way.

Actually he did answer it. You just didn't like his answer.

Just to explain what might be a tricky point, an equation like F = ma isn't just pulled out of the aether. It's a representation of known and studied behavior.

There is no known and studied behavior of objects with negative mass. There isn't even a rationale for throwing down absolute-value bars beyond "symmetry".

His answer says that negative mass objects are just as hard to accelerate.

As per my response here: http://news.ycombinator.com/item?id=1205011

You have it backwards - you can justify throwing absolute value into the equation if you actually find find evidence that negative mass is just as hard to accelerate as positive mass.

Well look, no one has seen negative mass objects (as far as we know). All he's saying is that this is one way to fix the F = ma equation to deal with negative mass.

I agree that the burden of proof is on him or anyone who wants to run with the idea, but for now its just being proposed as neat, possible idea.

You're reading a speculative blog entry as if it were a rigorous scientific paper and then claiming that he hasn't done the science.

No, I'm pointing out that, contra phaedrus, the concern is not "answered", but instead handwaved.

And when someone starts telling stories about a "well-known astronomer" who has substantiated his hypothesis, he's taken his claim to a higher level than "a neat, possible idea".

Also, E=mc^2 needs to be considered.

I would see two solutions here. (IANAP).

1) Energy can be negative. Not sure what that would mean though.

2) You can do the same trick as he did and do E = abs(m)*c^2.

I would be interested to see what the ramifications of each are.

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