There are some things with an negative effective mass, for example some electrons inside a semiconductor. It's easier to think about them as holes with a positive effective mass. More details https://en.wikipedia.org/wiki/Effective_mass_(solid-state_ph...
Anyway, the part in the site about friction is wrong. For example, holes inside semiconductors slow down and follow the conservation of energy law (it's not friction, but it's close enough). They don't get faster and faster like in the simulation. The weird behavior of the simulation is not realistic.
How come when the negative-mass ball encounters the force of the red ball pushing against it, it moves towards the red ball, but when the negative-mass ball encounters the force of a wall pushing against it, it moves away from the wall? Shouldn’t it also move towards the wall, like it did with the ball?
Because this simulation is nonsense. I don’t mean that pejoratively, just that you can’t get consistent answers from an inconsistent or in this case, under-defined, premise.
If we are talking about negative mass, it may be that mass and inertia become more clearly different things. Something with "negative" mass might be "pushed" by gravity but still retain normal inertia when touching other types of matter. So the two balls would still bounce off each other as normal, but the gravity interaction between the two would become weird and result in a net gravitational force moving both in one direction.
Most of this can be understood with two observations: negative mass has negative kinetic energy and its momentum points opposite the direction of velocity. So if a system composed of negative mass ‘loses’ energy or momentum to the environment it actually gains (negative or absolute) momentum. It’s all very unintuitive of course because it is technically nonsense.
Why doesn't the negative-mass ball fly off the ground rather than experiencing friction against it? Why is the negative-mass planet attracted to the positive-mass sun?
Edit: Now I realized that while the gravitational force will act in the opposite direction, it will cause acceleration in the same direction because… negative mass. So these two things are not wrong.
There's a lot of issues with these kinds of examples. The theoretical math/physics examples like these make me laugh. Like you stated, why is the negative mass object affected by gravity at all? The concept of parallel universes just because the math works out, but only if you change something to a negative value. That's fun to talk about over a couple of beers while puff puff passing, but people start to take things seriously and then we get all sorts of problems.
The bit about the balloons in the first two pages no sense to me, so figured it wasn't worth continuing.
When they were filled with air they exterted an upward force on the spring? Why!? And then when the air was removed, the force was downward? By "air" did the author mean "helium" or something? Or are we underwater or on Venus or something?
Also the meaning of "release" was poorly defined. Like... just draw me a free body diagram so I can tell what you're trying to say.
Did someone confirm negative mass? I wouldn't hold your breath on trying to understand negative mass. It is akin to time travel. I'm not saying it isn't possible to understand it, there are probably better things to waste your time with.
When I was an undergraduate I tried to develop a coordinate system for mass, where the center of mass of the universe was the origin, and the axes where the three fundamental forces. Then I found out from a professor that John Wheeler, who was very much alive at that time, had attempted it and I kinda gave up after that.
Later, in graduate school I learned about Wheelers geometrodynamics ("mass without mass"). Talk about paradoxes. I don't know how you resolve all of those paradoxes. I'm guessing that is why he gave up.
If negative mass were confirmed it would be a seismic shift in physics. I'm getting old, and don't keep up anymore. Let me know if it was confirmed, or what other research has been done to substantiate the idea.
At least at the level of isolated gravitational systems (where one can define the so-called ADM mass of a spacetime), mass cannot be negative under pretty general assumptions:
It has never been confirmed or even really hinted at by either theory or experiment, but it is fun to do Newton's laws using negative mass and note that they all still work out (e.g. conservation of energy and momentum still hold) even when the macroscopic phenomena become very weird.
Fun website, but I’m not quite sure what their point is. Are they trying to say that negative mass can have a meaning sometimes? Or is it just « let’s run a simulation on those equations using a negative mass ans see what happens » ?
That approach is not totally unjustified though. As an example, consider the complex numbers. They were first used to solve cubic polynomials, and people basically said "Let's pretend the square root of a negative number is something I can calculate with, obeying the general rules of calculus", and they did. Then they used those successfully to calculate real roots of cubic polynomials.
Well... The website seems like it just messes with things. But I remember an article claiming that phonos of sound in atmosphere behave like they have negative mass. Cause the sound wave would travel faster in the denser layers of air from the bottom, making the sound wave to go a little upwards, like a refraction.
Phonons can have a negative effective mass - in other words, you can mostly ignore the effect of the background environment if you simply change the mass to be something else (which can be negative).
That’s very different than having a negative actual mass.
If mass turns negative enough to overcome friction, the collisions from Brownian motion would amplify and we would explode. If negative mass balls in this simulation are made from ordinary matter they should explode, or at least dissolve into atoms and disperse.
My understanding is that this is not really negative energy, rather only energy lower than the quantum background. There is still an absolute zero energy as a hard floor, akin to how negative temperatures just mean lower than an agreed norm and one cannot have true negative temperature.
Readit News
There are some things with an negative effective mass, for example some electrons inside a semiconductor. It's easier to think about them as holes with a positive effective mass. More details https://en.wikipedia.org/wiki/Effective_mass_(solid-state_ph...
Anyway, the part in the site about friction is wrong. For example, holes inside semiconductors slow down and follow the conservation of energy law (it's not friction, but it's close enough). They don't get faster and faster like in the simulation. The weird behavior of the simulation is not realistic.
Edit: Now I realized that while the gravitational force will act in the opposite direction, it will cause acceleration in the same direction because… negative mass. So these two things are not wrong.
Like what?
When they were filled with air they exterted an upward force on the spring? Why!? And then when the air was removed, the force was downward? By "air" did the author mean "helium" or something? Or are we underwater or on Venus or something?
Also the meaning of "release" was poorly defined. Like... just draw me a free body diagram so I can tell what you're trying to say.
And what's in the balloon, to explain the forces?
When I was an undergraduate I tried to develop a coordinate system for mass, where the center of mass of the universe was the origin, and the axes where the three fundamental forces. Then I found out from a professor that John Wheeler, who was very much alive at that time, had attempted it and I kinda gave up after that.
Later, in graduate school I learned about Wheelers geometrodynamics ("mass without mass"). Talk about paradoxes. I don't know how you resolve all of those paradoxes. I'm guessing that is why he gave up.
If negative mass were confirmed it would be a seismic shift in physics. I'm getting old, and don't keep up anymore. Let me know if it was confirmed, or what other research has been done to substantiate the idea.
https://en.m.wikipedia.org/wiki/Positive_energy_theorem
That’s very different than having a negative actual mass.
https://en.wikipedia.org/wiki/Casimir_effect
https://en.wikipedia.org/wiki/Laser
https://en.wikipedia.org/wiki/Population_inversion
https://en.wikipedia.org/wiki/Negative_temperature#Lasers
(Negative thermodynamic temperature has very unintuitive effects in general, so maybe read all of the last article to get an idea)