4 ms·

If you put a negative mass and positive mass side by side and release from rest, they will accelerate indefinitely and break conservation of energy. Of course s

If you put a negative mass and positive mass side by side and release from rest, they will accelerate indefinitely and break conservation of energy. Of course science should be open to any possibility, no matter how strange. But I feel the author understates its strangeness. And requiring negative mass to be continually created makes this theory not all that much "simpler" than the standard dark matter+dark energy.

snowwrestler 8y ago
I'm not sure I think infinite repulsion is any stranger than infinite attraction, which is how we think gravity works now.
YaxelPerez 8y ago
They would accelerate indefinitely, but it wouldn't break conservation of energy. Gravitational force is inversely proportional to distance^2, so potential energy (integral from 0 to infinity of Force dx) still converges to a finite number. Same with normal gravity, but backwards.
- walrus1066 8y ago
  I think the weirdness is, the distance between masses wouldn't change, they'd just accelerate together, in the same direction, indefinitely. Both mass would experience negative repulsive force: F=Gm(-m)/r^2 =-Gm^2/r^2 The positive mass accelerates away from the negative mass, because F=ma => ma=-Gm^2/r^2 => a=-Gm/r^2 Now here's the kicker. If inertial mass (the m in F=ma), is the same thing as gravitational mass. Then, the negative mass accelerates towards the positive mass. Because F=(-m)a => F=-ma => -ma=-Gm^2/r^2 => a=Gm/r^2 So accelerates in same direction as positive mass. Technically, conservation of energy & momentum is maintained, because the negative kinetic energy of negative mass would cancel out positive energy of positive mass. But I think the above can't be natural, because the magnitude of kinetic energy would grow to infinity, leading to even more impossibilities. So you'd need to 'hack' the theory of gravity and make inertial mass different to gravitational mass. So the particle has negative gravitational mass, but positive inertial mass, to make laws of physics stay sane :)
  - FabHK 8y ago
    From what I gather, the negative mass repels the positive mass (which is thus accelerated away), and the positive mass attracts the negative mass, which (because it has negative mass) is thus also accelerated away. Now, the kinetic energy of the positive mass grows, but the kinetic energy of the negative mass is negative and falls (because its mass is negative...), so energy is conserved. EDIT to add: I think I gathered wrong. Apparently, there is runaway motion (same direction), energy and momentum is still conserved (since one mass is negative), and since total mass is zero, the two particles reach speed of light. Intriguing. See paper.
delecti 8y ago
The kinetic energy of a negative mass would also be negative, cancelling out the increased speed of both objects. The same would be true of conservation of momentum. There's no "conservation of speed" to be violated.
tonmoy 8y ago
If you put two positive electrically charged particles side by side, they will accelerate in the same way
eutropia 8y ago
Reading the paper, the author addresses this: "Firstly, the theory of positive–negative mass particle pairs provides clear rules that govern such interactions. The mechanics of these interactions are governed by the usual physical laws: the conservation of energy and momentum remain fundamental, and hence it is unclear why we should object to this potentially physical law of nature on grounds of aversion alone. Secondly, and more importantly, observations provide evidence for significant numbers of ultra-high-energy cosmic rays which are known to be extragalactic in origin, although the mechanism of their production remains a mystery (Pierre Auger Collaboration 2017). From this perspective, runaway motion is not a challenge for negative mass models, but is rather a useful observational constraint. The idea that all negative masses in a universe should form gravitational dipoles and accelerate to high energies is not supported by the simulations presented here (which have a limited number of particles), in which no runaway particles can be identified. While runaway motion is a legitimate physical facet of negative mass particle interactions, the simulations indicate that this behaviour is only common for idealised particle pairs and occurs more rarely as a bulk behaviour within a negative mass fluid. This is likely as the particles in such a fluid are subject to numerous counteracting forces from the surrounding medium. One can assume that some amount of runaway particles must still exist, although these would likely be highly scattered by Brownian motion (e.g. Landis 1991)."

snowwrestler 8y ago

I'm not sure I think infinite repulsion is any stranger than infinite attraction, which is how we think gravity works now.

YaxelPerez 8y ago

They would accelerate indefinitely, but it wouldn't break conservation of energy. Gravitational force is inversely proportional to distance^2, so potential energy (integral from 0 to infinity of Force dx) still converges to a finite number. Same with normal gravity, but backwards.

walrus1066 8y ago
I think the weirdness is, the distance between masses wouldn't change, they'd just accelerate together, in the same direction, indefinitely. Both mass would experience negative repulsive force: F=Gm(-m)/r^2 =-Gm^2/r^2 The positive mass accelerates away from the negative mass, because F=ma => ma=-Gm^2/r^2 => a=-Gm/r^2 Now here's the kicker. If inertial mass (the m in F=ma), is the same thing as gravitational mass. Then, the negative mass accelerates towards the positive mass. Because F=(-m)a => F=-ma => -ma=-Gm^2/r^2 => a=Gm/r^2 So accelerates in same direction as positive mass. Technically, conservation of energy & momentum is maintained, because the negative kinetic energy of negative mass would cancel out positive energy of positive mass. But I think the above can't be natural, because the magnitude of kinetic energy would grow to infinity, leading to even more impossibilities. So you'd need to 'hack' the theory of gravity and make inertial mass different to gravitational mass. So the particle has negative gravitational mass, but positive inertial mass, to make laws of physics stay sane :)
- FabHK 8y ago
  From what I gather, the negative mass repels the positive mass (which is thus accelerated away), and the positive mass attracts the negative mass, which (because it has negative mass) is thus also accelerated away. Now, the kinetic energy of the positive mass grows, but the kinetic energy of the negative mass is negative and falls (because its mass is negative...), so energy is conserved. EDIT to add: I think I gathered wrong. Apparently, there is runaway motion (same direction), energy and momentum is still conserved (since one mass is negative), and since total mass is zero, the two particles reach speed of light. Intriguing. See paper.

delecti 8y ago

The kinetic energy of a negative mass would also be negative, cancelling out the increased speed of both objects. The same would be true of conservation of momentum. There's no "conservation of speed" to be violated.

tonmoy 8y ago

If you put two positive electrically charged particles side by side, they will accelerate in the same way

eutropia 8y ago

Reading the paper, the author addresses this: "Firstly, the theory of positive–negative mass particle pairs provides clear rules that govern such interactions. The mechanics of these interactions are governed by the usual physical laws: the conservation of energy and momentum remain fundamental, and hence it is unclear why we should object to this potentially physical law of nature on grounds of aversion alone. Secondly, and more importantly, observations provide evidence for significant numbers of ultra-high-energy cosmic rays which are known to be extragalactic in origin, although the mechanism of their production remains a mystery (Pierre Auger Collaboration 2017). From this perspective, runaway motion is not a challenge for negative mass models, but is rather a useful observational constraint. The idea that all negative masses in a universe should form gravitational dipoles and accelerate to high energies is not supported by the simulations presented here (which have a limited number of particles), in which no runaway particles can be identified. While runaway motion is a legitimate physical facet of negative mass particle interactions, the simulations indicate that this behaviour is only common for idealised particle pairs and occurs more rarely as a bulk behaviour within a negative mass fluid. This is likely as the particles in such a fluid are subject to numerous counteracting forces from the surrounding medium. One can assume that some amount of runaway particles must still exist, although these would likely be highly scattered by Brownian motion (e.g. Landis 1991)."