Warning: Not every reader is interested in following the technical details of Mike's exposition on how lasers produce light. For those who don't care. Just skip this.
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“... But how is the light produced?” She asked hopefully.
Mike sighed. “Oh no.” He held up his hands. “The answer to that question lies in the domain of Quantum Physics. That's a whole new branch of physics. It’s much too large to get into tonight. Besides I'm tired, and I'm not really very knowledgeable in that subject area.”
Mike had been standing in the location where he had first entered the room. Now Twilight walked up to him and put one of her hooves on his thigh. It was the first time she had ever initiated any contact in an effort to motivate him. Mikes eyes widened slightly as she looked beseechingly up at his face.
“Please. Won't you try? Even if you don't know that much about it, this seems to be another area of fundamental physics which we don't have in Equestria. I would dearly like to know something about it.” Her eyes seemed to grow more luminous, as she gazed upwards at him. “Please.”
Mike couldn't resist those incredible eyes, he caved. “Oh, alright. But this is the last one for tonight.” He admonished sternly. “It's starting to get late, and I'm getting tired.” Twilight grinned up at him.
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Mike grinned back. “Okay, I'll start with atoms. Do you know the atomic theory of matter?”
“All matter is composed of tiny indivisible particles, called atoms. Yes, that's a confirmed scientific fact.” was Twilight's reply.
“That’s good. So, in the hopes of shortening this explanation, what do you know about the internal structure of atoms?”
“Nothing really,” Twilight confessed. “Some scholars have postulated that atoms must, in fact, have an internal structure. And that theory is generally well accepted by most scholars, including myself. But as for any specific knowledge of or evidence for the internal structure of atoms, we have none so far.” Her ears drooped sadly.
“Well then, let me start off by telling you that an atom is almost exclusively composed of empty space.” Twilight was surprised to hear that. Her ears perked forward attentively.
Mike continued. “An atom is something like 99.9999% empty space. Actually, I'm pretty sure there are a lot more nines to that number, but you get the idea. It turns out that almost all of the mass of an atom is concentrated in a tiny ball of particles at its center. We call this the Nucleus.
“A Nucleus is comprised of two types of particles, a positively charged Proton and a neutral particle called the Neutron. The number of Protons in the nucleus determines the atom’s 'element.' One proton makes a Hydrogen atom. Two protons make a Helium atom, three makes Lithium and so on.”
Twilight instantly grasped the concept and raced ahead. “What purpose do the 'newtrons' serve?”
“Well Twilight, I am not an expert in nuclear physics, but my understanding was that they play a major role in bringing all those positively charged protons together in the nucleus. Otherwise, the like charges of the protons would cause the nucleus to fly apart.” Twilight nodded her head in understanding.
“That's enough for the nucleus. Our main focus, for now, will be on the Electrons, those negatively charged particles which occupy all the rest of the atom's space.
“I should mention, however, that the proton and electron carry electric charges of equal size. So, for an electrically neutral atom, there are-”
“Equal numbers of protons and electrons.” Twilight finished his thought.
“See, so far it’s all very easy.” Mike congratulated her.
“But Mike, what keeps the electron from being attracted by the nucleus. Won't it end up being snuggled right up against the protons?”
“Ugh, I was hoping to avoid that question. You're too bright for my own good. You know that?”
Twilight smiled at Mike's veiled compliment.
“Well to answer that question I will need to digress somewhat, and introduce you a foundational concept of Quantum physics, the Heisenberg Uncertainty Principle. Abandon all hope ye who enter here.”
“What?” Mike’s strange comment caused her to feel uncertain.
“Sorry, just cribbing a quote from a famous piece of literature.
“The Uncertainty Principal states that there is a fundamental limit to how precisely one can determine the exact position and momentum of a particle. If you know its exact position, then you must accept increased uncertainty as to that particle's momentum. Conversely, if you know its exact momentum, then its position is uncertain.”
“But, that's so ridiculous! Of course, I know where something is. For example, you Mike are sitting in that chair, and you are not moving, so your momentum is zero.”
“Yes Twilight, at macroscopic scales, you know those two values as precisely as you need to. However, Plank's constant, a number which expresses the fundamental scale at which the uncertainty comes into play is an extremely small number. You only start to see noticeable effects when you operate at the scale of atoms and subatomic particles.”
“Okay, the effect only occurs at very small scales. But why can't I just measure both the position and momentum of an electron?” She insisted on her point of view.
“In concept, you imagine you can. However, all attempts to measure a particle will involve having it interact with other particles that you have sent in to probe it.”
Twilight considered his statement for a moment. “How about using rays of light to track the particle?”
“A good idea except for that fact that even light is composed of particles. We call them Photons. If you hit an electron with a photon, that will definitely affect the electron's momentum.”
“Light is composed of particles?” She asked incredulously. "A few minutes ago you were talking about the rays of light from the laser and their wave behaviors.”
“One of the most confusing things about Quantum Physics is the fact that it demands an acceptance of the fact that all particles are simultaneously both particles and waves.”
“But they can't be both. How is that even possible? The two concepts are mutually incompatible.”
Mike sighed. “I don't know Twilight. All I can do is repeat for you one school of thought. The Heisenberg Uncertainty Principle is more than just a statement about the limits of observability; it is a statement about the nature of the universe.
“Do not think that of the particle as having some 'true' position and momentum which you are simply unable to measure. Think instead, that the particle actually does simultaneously occupy all positions and possesses all possible momentums as defined by the limiting uncertainty.
“In effect, the particle lives a ghost-like smeared out existence, occupying all locations, and traveling all possible paths, that it is possible for it to have. The aggregate effect of the probability of all possible interactions with any other particle at some localized point can be characterized as a wave function.”
“But, but, this is simply too fantastical to believe.”
“Believe me Twilight, this is incredibly non-intuitive. I don't think our minds are built to comprehend it fully. And the math can be especially obtuse.
There are famous experiments, which always show the same results; A single particle, demonstrably alone, still manages to have interference patterns with itself, as though it were a wave.”
Twilight did not reply. She merely sat still, thinking furiously. “I want to see that experiment!” She practically hissed her demand at Mike.
“You've got it Twilight. But enough thinking about wave-particle dualities. Let’s return to your question about the electron.
“You see, between the protons in the nucleus trying to constrain the electron to an almost infinitesimal location, and the uncertainty principle, the electron ends up resonating between the confines of the nucleus and the relaxed freedom of the outer parts of the atom. It ends up in one of several, well, you could think of them as resonance zones, within the body of the atom. We call these resonance zones, orbitals; others might call them electron shells.”
Twilight nodded slowly, overwhelmed, trying to picture what such an atom would look like. “Why call them shells?”
“I'm not sure. But to my mind, it forms a simplified mental picture if you imagine the electrons being arranged on successively larger shells inside the atom, kind of like a Matryoshka doll.”
“A what now?”
“Uh, you know, like a doll within a doll within a doll. Um, maybe you don't have those...”
“Oh, now I know what you mean, Stalliongrad nesting dolls!” Twilight smiled as she recalled some fond memory.
“Right. Stalliongrad nesting dolls.” Mike shook his head as he briefly wondered at the confluence of names between their two universes.
“Anyway, the electrons and their positioning within the outermost electron shells are what determine the chemical characteristics of the atom.” Twilight's face lit up in pleasure at that revelation.
“Back to lasers. After a whole lot of research into the internal structure of atoms, our scientists realized that an electron could absorb a packet, or quanta, of energy and jump up to one of the higher energy electron shells. Conversely, the electron can release, or emit, the same size quanta of energy and drop back down to the lower electron shell. Such jumps are characterized by specific quantity of energy. No more and no less.”
Twilight frowned. “Assuming everything else you told me holds true. I can sort of see that.”
“Now, suppose you take a large population of atoms, and hit them with a sudden burst of energy, such as a very bright flash of white light or perhaps an electrical discharge. If done correctly, what you end up with is a substantial population of atoms which have just absorbed the required quanta of energy to jump an electron into a higher shell. Such atoms are said to be in an excited energy state. Very soon, some of those excited atoms will emit their absorbed quanta of energy. It will appear as a photon. One of those light particles I told you about."
Twilight nodded her understanding.
“Now here's another mystery of Quantum Physics. When a photon, which has the exact energy as that retained in an excited atom, strikes that excited atom, it stimulates the atom into releasing its absorbed quanta of energy as a second photon. The new photon emitted by the atom is in all measures exactly identical to the first one. It will have the same energy, the same phase, and will be traveling in exactly the same direction.
“Imagine those two photon's encountering more and ever more excited atoms. What started with a single photon has now swelled into a mighty tsunami, forming a bright burst of light with some decidedly unique properties.”
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Twilight's jaw dropped. “That's it? That's the deep dark secret? If a photon strikes an atom in an excited energy state, the atom will give up its excitation energy as an identical photon.”
“Well, you glossed over quite a few details, but that's basically it. That's the core concept of the laser.”
Twilight just sat there on the couch, reveling in the satisfaction and excitement of new knowledge learned. Slowly a smile crept onto her face as she considered the deeper mysteries of the universe that had always been there, lying at her hooves, simply waiting to be unlocked.
5152677 No, I used the words correctly. As that is what I ment to say.
The first level of achievement, would be to develop a machine that could reason. Sapience.
The next level of achievement, after the sapience, would be to give that machine intelligence the abiltiy to sense and feel. Sentience.
Perhaps I am too influencd by STNG. With the way Data was able to think, but unable to feel any emotions.
5152694 Perhaps they could do that.
But unless they had a true 'spring' in their distant past, as well as the scientific knowledge at that time, to realise what was the specific cause of the sap run, then who would ever have known what to do.
5152793 Heh, I always liked the headcanon where Discord, once he went mad, went from managing and maintaining chaotic physics, similar to ours, to, well, what he does now that irritated people enough to Petrify him. Once that happened,Chaos, or at least most of the macro-scale Chaotic based systems stopped working predictably, and as a result, Seasons, Weather, and most Life itself, stopped working, mostly. Effectively Sundering Reality, and requiring someone to manually control all that stuff.
5152785
• Emotion: discrete, consistent responses to stimuli of significance to that sentient.
• Feelings: subjective representation of emotions, private to the individual experiencing them.
• Moods: diffuse affective states generally longer lasting and less intense than emotions.
• Affect: umbrella term covering emotion, feelings, and moods together; commonly used interchangeably with “emotion.”
• Sensation: representation of stimuli.
• Perception: interpretation of sensation.
tl;dr: You’re still wrong, though less than I (or ssokolow) thought. Sapience requires sensation and perception, so any sapient being is already two‐thirds of the way to meeting the textbook definition of possessing sentience.
Sentience also requires subjectivity of experience and an AGI not specifically designed such theoretically cannot have this; in practice, even hardware made and code written to the most exacting standards will always differ from previous iterations. (It can still be said that any AI not specifically designed to have subjectivity of experience will almost lack emotion… so much so that you might need scientific instruments to locate any.)
5153612 I bow to your wisdom.
I was just working from my own understanding of those words.
I took sapience to be the level of AI where a computer can reason and think, in order to solve problems, but is not aware of its own existence except as a factoid.
To me Sentience was the point at which that AI became aware of 'self' and by corollary 'other'. That it might express/feel regret if faced with the end of 'self' or 'other'.
If I'm wrong, I'm wrong. I won't press the issue any further.
5152785
I don't have time to confirm, but my intuition is screaming at me that the nature of the type of reasoning described by "sapience" necessitates "sentience" as a prerequisite.
This fascinating piece by David Deutsch on the nature of artificial intelligence may be relevant but it's been too long since I last read it. However, given what I can infer about you, both from what you've said and from the focus the story has taken, I think you'd enjoy it either way.
Also, regarding data, emotions or not, he had subjective experiences. They're not purely limited to emotions. That's just the most obvious way to explain what qualia are to people.
5153763 The issue of the solar cells is debatable.
No, I did not do any calculations when I wrote the story, because Mike's comments were 'off the cuff' and the writing remained authentic to that.
However this is what I do know from my own experience.
Today's commercial solar panels represent an area of around 1 sq. Meter. And provide around (very roughly) 200 Watts.
Wally's, judging from his size in relation to the humans, is only about than 2 sq ft. I'd be surprised if he could get better than 30 Watts out of them in really bright sunlight.
Considering the amount of physical activity Wally has to do, compacting garbage, transporting himself and those loads up to the top of some really tall mountains of garbage... Then his battery must hold something like 50 Kwh of energy, maybe more.
Just how long do you think it might take to fill up a 50 Kwh battery at a maximum charge rate of 30 Watts?
Maybe 1500 hours if we are really optimistic. At 12 hours a day (also optimistic) that makes it about 140 days or 20 weeks.
If you quadupled the efficiency of Wally's solar cells (25% -> 100% but not theoretically possible), then you could shorten his charge time to 5 weeks.
This is the best fanfiction I have ever read everything about it is great please continue making more
5152785 This was the best damn lecture on physics I've ever listen to/read...and my best friend is a professor of Quantum Physics!
I've watched more complicated. Physics, man I love it. Nice to know that others do to. Isn't quantum theory grand?
huh, that's actually a clever way to put it. so all the photons in a laser are going the same direction because the first one makes the second pop out, which make the next two pop out, and so on, and all the energy going into this thing just creates those excited states, so all the energy going out is going to all be in the same direction as that first photon.
brain melting
It's chapters like this that are starting to really set apart with fic from the others in my mind. I'm not far along with my science, but heck, it's just lovely seeing some of the subjects touched upon in my chemistry and electricity/magnetism class come up again. Plus, there's a good bit of stuff I simply didn't know scattered about too. I just love it.
Anyways, awesome story so far; I love the setup, and every scientific back-and-forth has been an absolute pleasure to read.
I rather enjoy all the Technical discussions.
Twilight and Mythbusters.....think about it.
6164860
I shudder to think of it. Twilight should be very afraid!
Nope. Ain't happening. Not if Mike has anything to say about it.
i.ytimg.com/vi/I3dfRtHF0vM/maxresdefault.jpg
I was actually hoping it would turn out that while Twilight was completely mystified by credit cards and home heating furnaces, that because she uses magic her knowledge of quantum physics would be vastly superior to that of humans, and that she'd end up lecturing Mike on the subject. To his simultaneous confusion at not understanding, and great terror at the realization that she could casually answer some of physics' greatest mysteries.
"Oh, you still think of fundamental forces and elementary particles as separate phenomenon? That's comically antiquated. Why, any unicorn much past 12 months old can..."
I understood this better then when they taught this in class...
6188070 no a 20 megaton fission bomb would be a better. radiation is a good way of testing immortality
What about pilot wave theory?
Don't leave Louis and David out.
7840407 Truthfully, I have never heard of this theory before. So it's legitimate to say that Mike hasn't either. So - I just did a google search on it, and it does seem intriguing.
Now as to its impact on my story. Recent tests which seem to promote the theory were announced last year (2016). But Twilight's World takes place at the end of 2013. So Mike would likely not yet have encountered the theory.
Kind of sad he didn't bust out the periodic table. I guarantee that Twilight would be astounded by the sheer number of elements humanity has discovered, and would also lead into a whole tangent about radioactivity.
7841561
Oh boy; I can't help, after this chapter, help but imagine our adorkable purple bookhorse experimenting with magic, and its interaction with various laws of physics... Speaking of, does that make Thaumatism a fifth fundamental force, much like Electromagnetism and Gravity, to name a few...?
To the extent of my knowledge, that was a good explanation.
This is a really nice basic introduction into how lasers work, but I'm a bit miffed that Mike didn't hint at all the things left out of this explanation for simplicity.
Like for instance that a photon at the appropriate energy level could interact with either an excited atom - generating another photon, or an unexcited atom - being absorbed and exciting the atom (population inversion is required to actually produce laser light, and they ways this is achieved are fascinating), not hinting at spontaneous emission of photons from excited atoms (it's not a stable state, something Twilight could have figured out but it would be worth mentioning in an explanation).
I'm also a bit disappointed at a complete lack of mention of Pauli's exclusion principle a bit earlier, when talking about electron orbitals, or even hinting at it in some way, saying there's a limit to how many electrons there can be in a given orbital. The explanation is not complete without that - I felt that myself since I took chemistry in middle school, orbitals utterly confused me and the basic explanations could not satisfy me before I came across the full, proper, quantum explanation in university, describing the full quantum state of electrons within an atom. This is also fascinating and helpful for explaining other things, like ferro-, para-, and dia- magnetic materials.
I'm fine with not going deeper into wavefunctions but it was a bit disappointing after my university physics teacher personally drilled wavefunction calculations into me, including calculating wavefunctions for electrons in a hydrogen atom and wavefunctions for various problems involving electric potentials.
Hinting at the four fundamental forces would also be nice at this point but I feel it would cause a *massive* tangent explaining it to Twilight at this point specifically. At least explaining electromagnetic and strong forces in a very basic manner would help here instead of glossing over them like this explanation did.
Anyway, this is an amazing chapter and I wish people did more of this in fiction. I've only really seen this kind of thing in fiction that's explicitly meant to be educational, and often it goes a LOT less deeply into things than this here, so great job. Besides that I've only seen this depth of explanation in various fanfics... and the vast majority of the time it was eggheading with Twilight. (Like, why aren't there fics like this with Pokemon professors or something? This is an underexplored idea.)