When originally conceiving of the character of Brigid Veila in close concert with her creator, KM Murray, we determined that Brigid should be capable of “bending” certain rules of physics. For the purpose of the novel, that “bending” has become a little bit more powerful than I suppose either of us envisioned it originally, though not without cost. That said, I have still endeavored to thoroughly consider the implications of how Brigid’s powers function in a practical sort of way, and to explain those implications in-text without devolving into a lecture on theoretical physics.
Not that I’m qualified to give such a lecture anyway, of course; I’m an actor, Jim, not a scientist.
Nevertheless, I thought that I might do my best to explain some of the principles at play here, both as a way of documenting my own creative process and of sharing some insight with any curious readers. There are many ramifications to Brigid’s physics bending abilities, and we may look into more of them in future installments, but for now we’re going to focus on the idea of mass, energy, and momentum, as they appear when Brigid first uses the power of Rasp. In particular, we’re going to look at the reasoning behind these ideas and how that reasoning accommodates the perversions of nature that are Brigid’s powers.
To begin with, let’s establish some basics. There are a few rules that are, for the most part, essentially inviolable in the universe as we know it, and the ones that bear the most direct consideration here are as follows:
1. The amount of mass in the universe is constant (except when it changes into energy, i.e. nuclear weaponry)
2. The amount of energy in the universe is constant (except when it changes into mass, i.e. mass excess in formation of TNT)
3. The amount of momentum in the universe is absolutely constant (no exceptions!)
These three rules are deeply connected to each other because momentum and energy are both inextricably bound up in the mass of the objects said to hold them. Momentum is defined as mv, the product of mass and velocity; for macroscopic considerations (which we will stick to for now), the kinetic energy of an object is 0.5mv^2, half the product of mass and velocity’s square. Mass affects both of these things, so if you change the mass of an object, you change both its momentum and its energy.
This is, in large part, due to the fact that the mass still exists, even if it is removed from the object; because of the first two rules, in our universe, we can only change the location/velocity of the mass or convert it into energy. It is impossible to reduce mass without converting it to energy, so either a) the mass stays the same, and so, accordingly, does the momentum and kinetic energy or b) the mass is changed to energy, which is used to accelerate the objects in question, thus conserving momentum and energy (though KE may be greater than before as mass-energy conversions are usually somewhat explosive).
However, in the universe of The Abadon Relic, Brigid is able to actually reduce the amount of mass in the universe without converting it to energy. This is, of course, a violation of rule number 1, but that is how Brigid’s powers work. Let’s explore the consequences of this.
To do so, it is important to explain how it is even theoretically possible to reduce the mass of an object without reducing the amount of matter in that object. An author I admire tremendously, Alistair Reynolds, wrote about this idea in his book Redemption Ark, wherein a secret technology was developed to alter the local field properties of inertia. As far as we know, inertia is a property of matter that can be thought of as its resistance to changes in its “frame of reference.” If you remember Newton’s first law of motion – objects in motion tend to stay in motion, objects at rest tend to stay at rest – then you know the most important thing about inertia already. Inertia is the property of matter that means you have to use force to move it, or stop it from moving if it’s already moving. The amount of force that you need to accelerate an object by a particular amount, however, is usually thought of as dependent on that object’s mass. Accordingly, there is an intricate link between the mass of an object and the inertia of an object.
In Reynold’s book, however, it is theorized that this property of matter is not dependent on mass, persay, but actually on a quantum particle interaction between matter and the background field (assuming I read the book correctly…Alistair and fans, please come for me if I’ve got this wrong). In essence, the theory states that objects don’t resist movement because they’re massive, but because they “stick” to a virtual field around them that is matching their current velocity, i.e. their frame of reference. If you make them less “sticky,” they will be easier to move. This, in essence, is what reducing the property of inertia amounts to in Reynold’s book, and I use a similar application in The Abadon Relic.
So, while Brigid says that she is reducing mass, she is not necessarily making matter disappear, but she is making it less “sticky” to its frame of reference – an infinitely extensive network including all things moving at the same velocity as the object, and all space in between those things. For all intents and purposes, making matter less sticky makes the matter in question weigh less (except where gravity is concerned, but that’s another subject entirely), despite there still being just as much matter as before.
Therefore, as far as the rules regarding energy and momentum are concerned, even though the amount of matter in the universe is the same, the amount of mass is not.
So then, what does this cause?
It turns out that it alters the entire universe instantaneously, or else winks it out all of existence due to simultaneity violations.
The reasoning for this apocalyptic forecast lies in the mathematics of relative motion. Although mass is a constant that does not depend on the frame of reference of the observer (usually – oh physics, you ludicrous bird), velocity is absolutely and entirely relative, which means that momentum and energy, which are both based off of velocity, are also relative. If two objects are travelling in the same direction at the same speed, they will have no apparent kinetic energy or momentum in relation to each other, even though they may have very high energies and momentums to an observer that is stationary. Think of being on a train, or an airplane: even though you are travelling very fast, the person next to you does not seem to be moving. Relative to the ground outside, your momentums are high; relative to each other, they are zero.
Focusing on momentum only, we know that an object’s momentum is dictated by mv, the product of mass and velocity. But if the velocity is 0, the momentum is 0, no matter what the mass. In other words, if you and a friend were travelling in a train together, and one of you suddenly had less mass, there would be no requirement for any consequent change in your friend’s velocity relative to you – their momentum was 0 before, and it is still 0 now. Momentum, from your perspective, is conserved no matter what happens to mass, without changing velocity.
However, if someone is observing your friend from a platform outside the train, we have a different story. From that person’s perspective, your friend has a non-zero momentum, and so to keep it at a fixed amount, if the mass decreases, the velocity must increase. To the person on the platform, your friend is now moving faster than before. But to you, they are still moving at exactly the same speed as before – 0, relative to you. From the observer’s perspective, your friend should be starting to move forward faster than the train, but from yours, they should remain seated exactly where they are.
This is a paradox, and the universe abhors a paradox. There cannot be two disparate perceptions of reality; either the universe would implode in on itself in an instant, winking out of existence, (or perhaps merely annihilating the offending object), or it would have to find another way to distribute the momentum conservation that does not violate causality.
To do so, it would have to change the momentum of every object in the universe in the same frame of reference as the object whose mass changed.
In other words, the reason your friend doesn’t appear to be moving faster to you is because you are also moving faster, now, and so is everyone on the train, the train itself, and everything else in the universe that was moving at the same velocity before. If you think back to the idea of inertia as being “stuck” to a frame of reference that extends to all objects in the universe with the same velocity, this idea almost seems to hold water: by reducing the “stickiness” of one piece of that frame of reference, the burden of conserving momentum is shifted onto every piece of that frame of reference. The good news here is that there would be an immeasurably large amount of matter moving at a particular velocity, so the change in velocity could be very subtle and, in fact, hardly noticeable.
So why did Brigid have to undo conservation of momentum to use her power to reduce Siri’s mass?
Two reasons: first of all, Brigid is absolutely brilliant, but she’d not a flawless supercomputer, and she actually didn’t have time to think through the cosmological implications of multiple frames of references and possible paradoxes; she was just concerned about accelerating Siri from her point of view, and therefore chucking her into space. It turns out that it would have been impossible for that to happen (either the change in velocity would be negligible or the universe would go ‘boom’) but she didn’t necessarily know that! Secondly, even if she did know that, how could she take the risk of exploding the entire universe due to causality violations?
There is another reason that is perhaps a bit more scientifically satisfying, however:
If mass is removed from the universe without being converted to energy, you can’t simultaneously conserve momentum and energy without absorbing energy in ways that just don’t make sense.
Consider a (relatively) moving object losing mass and therefore having to increase its velocity to conserve momentum. The loss of mass would lead to a loss of kinetic energy – this might be a good thing from a universal accounting, because mass and energy are tied, so it would make sense for there to be less energy if there is less mass. However, the increase in velocity would cause a much greater increase in kinetic energy, not only undoing the previous loss of energy as mass, but actually causing there to be more kinetic energy in the universe than there had been to begin with (this is because kinetic energy is based on the square of velocity, making it more vulnerable to changes when the velocity changes).
This could, perhaps, be ameliorated by reducing the amount of energy elsewhere in the universe without affecting the momentum. The most obvious way to do this would be by absorbing heat. But how? There is no obvious example of heat energy being absorbed as kinetic energy outside of fluid dynamics. Solids – and a good percentage of Siri Joranson is solid – just don’t work that way. Perhaps – perhaps – the kinetic energy could be absorbed as heat energy through the expansion of air in her lungs, but there’s still the problem of how exactly that energy transfer is accomplished, particularly since it would need to happen instantaneously, or else the energy in the universe will not be conserved. Heat flow is rigidly dependent on relative temperature, surface area, and material (none of which are being tampered with here so far) and is never instantaneous, so the only way it could even possibly work would be if Brigid could mess with the rules governing heat flow. Even if this were possible, it might cause serious harm to Siri as the heated, expanding gasses would be inside of her.
It was simpler to turn off conservation of momentum.
There would also be an issue in the amount of energy necessary. Let’s do some quick calculations here:
Siri is about 70kg and was travelling at about 1m/s before Brigid used her abilities, giving her a KE of 0.5*70*1 = 35J. In order to be lighter than air, she would need to reduce her mass tremendously; air has a density of 1.3kg per cubic meter, while water (the same approximate density as a human body) is closer to 1000kg per cubic meter. In other words we’re dividing mass by about 760, so, if we were conserving momentum, we’d be multiplying speed by 760, which would in turn mean multiplying the KE by close to 580,000 times.
Since we started with a KE of 35J, that means we need essentially 580,000 times 35J extra energy from the universe – or well over 20 mega Joules. A single cubic meter of room temperature air has about 150 kilojoules of thermal energy available in it; even if we give a very generous allotment for potential energy stored as phase changes, that’s still probably less than 500 kilojoules of energy, or one fortieth of the energy needed. Therefore, to obtain all the necessary energy, the surrounding 40+ cubic meters of air would need to be turned completely solid.
Again, simply turning off conservation of momentum was easier!
Even with momentum conservation turned off, there is still the matter of conserving energy; the less massive object has less kinetic energy, meaning the total amount of energy in the universe would be reduced. To make up for this reduction, reducing the mass would have to somehow cause an increase in some other form of energy. For the purposes of The Abadon Relic, I assumed that would be stored virtually – think of it as a highly abstract form of potential energy - to be returned to Siri in the form of missing kinetic energy when she regains her mass. The amount stored is relative to the frame of reference observing the problem; the amount returned is the same.
So, for now, we can conclude that Brigid’s approach was functional and valuable; however, there remain some frightening little dragons in the mathematics of it, considering what could have happened if she’d altered her approach even slightly. It will be interesting to see how that plays out in the future!
Reynolds, Alistair – Redemption Ark
General google searches for basic physical constants