One day, I might learn enough physics that my questions don’t sound like nonsense to physics graduates. Today is not that day — my working assumption is I sound like a freshman at best, and a homeopath at worst, and will remain so until I put numerical simulations of standard results in general relativity, quantum mechanics, and Navier-Stokes equations onto my GitHub page.
The baryon asymmetry problem is that matter and antimatter are always created and destroyed in equal quantity, yet the universe clearly has more of one than the other.
If you can make or destroy one without the other, in isolation, then you also get to violate charge conservation, which would mean that quantum field theory is wrong because something something Noether’s theorem. (Of course quantum field theory might be wrong; it’s known that general relativity and quantum physics can’t both be true because if they were both true the universe would’ve collapsed instantly at the very beginning).
The only way you can conserve charge but take antiparticles out of the system is if the process requires an equal number of antiprotons and positrons.
Both of these options — either violate charge conservation or take out multiple particles at once — have interesting consequences which can probably be tested, although not by me, given my degree is in a totally unrelated field.
If charge conservation is violated, then the universe should have a net electric charge. This charge should change over time, as there are still natural processes creating positron-electron pairs but not (at least to the same degree) proton-antiproton pairs. I don’t understand what this would do to the Einstein field equations (only that it would do something; given the effect on black holes I have to ask if it could be dark energy?), but I’m fairly sure lots of free electrons in the interstellar or intergalactic medium should be noticeable.
On the other hand, if antiprotons combine with positrons and that composite — possibly but not necessarily, given how conjectural this already is, an antineutron — either that composite is stable or it has a way of decaying into something other than an antiproton and a positron. The obvious question this raises is: could this be dark matter?
The obvious counter-point to the question “what if antineutrons are stable” is “surely someone would have noticed”, which is a fair question that I cannot answer — I genuinely do not know if anyone would have noticed yet, given how hard it is to make antimatter, how hard it is to trap antimatter, how hard it is to trap even normal neutrons, and the free-neutron half-life.
I can say other people have thought about neutron-antineutron oscillations, which might well solve the baryon asymmetry problem all by itself without any consequences for dark energy/dark matter: https://arxiv.org/abs/0902.0834
(Another thing I definitely don’t know, and which my physics MOOC won’t teach me, is how to separate legit ArXiv papers from the bogus ones; that reflects badly on me, not on the authors of that paper).
Let’s hypothesise sufficient brain scans. As far as I know, we don’t have better than either very low resolution full-brain imaging (millions of synapses per voxel), or very limited high resolution imaging (thousands of synapses total), at least not for living brains. Let’s just pretend for the sake of argument that we have synapse-resolution full-brain scans of living subjects.
What are the implications?
- Is a backup of your mind protected by the right to avoid self-incrimination? What about the minds of your pets?
- Does a backup need to be punished (e.g. prison) if the person it is made from is punished? What if the offence occurred after the backup was made?
- If the mind state is running rather than offline cold-storage, how many votes do all the copies get? What if they’re allowed to diverge? Which of them is allowed to access the bank accounts or other assets of the original? Is the original entitled to money earned by the copies?
- If you memorise something and then get backed up, is that copyright infringement?
- If a mind can run on silicon for less than the cost of food to keep a human healthy, can anyone other than the foremost mind in their respective field ever be employed?
- If someone is backed up then the original is killed by someone who knows the person was backed up, is that murder, or is it the equivalent of a serious assault that causes a small duration of amnesia?
Homeopathy: for those who have never learned the details, claims that the potency of a treatment can be increased by repeatedly diluting it. There are many scales — the C-scale is “how many times has this been diluted by a factor of 100”, the X-scale “…by a factor of 10”. I’d say “clearly nonsense”, but I fell for it when I was a teenager.
Fermi paradox: there are so many stars in the observable universe — tens of sextillions (short scale) — that even fairly pessimistic assumptions imply we should be surrounded by noisy aliens… so why can’t we see any?
One of the most common resolutions to the Fermi paradox is that there are one or more “great filters” which make it entirely unlikely that any of those stars have produced intergalactic expansionist civilisations. There are good reasons to expect direct intergalactic expansion rather than starting with ‘mere’ interstellar expansion, and (rather more surprisingly) good reasons to think we’re within spitting distance of the technology required, but that only makes the non-technological problems all the more severe. There are a lot of unknowns here, obviously we’ve only got ourselves as an example, so the space between “where we are now” and “owning the universe” is filled entirely with underpants gnomes, and that’s where homeopathy fits in, in two separate ways.
First, as a categorical example. Homeopathy represents an archaic way of thinking, yet it’s very popular. It’s simple, it’s friendly, it is a viral meme. There are many of these, some of them are quite destructive, and while it’s nice to think nature is in a balance — especially when we’re thinking of something we’re really proud of such as our own minds — the truth is nature (including humans) often goes off the deep end and only sometimes recovers. It’s very easy for me to believe that an anti-rational meme such as homeopathy can either destroy a civilisation entirely, or prevent it developing into a proper space-faring civilisation.
Second, as an analogy. Dilution. It’s not the first dilution of a homeopathic preparation which removes all atoms of active ingredients from the result, but the repeated dilution. If there are, say, twenty things which have an independent 50% chance of holding back or wiping out a civilisation out before it can set up a colony — AI; bioweapons; cyber-warfare; global climate change (doesn’t matter if artificial warming or natural ice age); cascade agricultural collapse; mineral resource exhaustion; grey goo; global thermonuclear war; cosmic threats collectively from noisy stars whose CMEs make electricity impractical to asteroids and gamma ray bursts; anti-intellectualism movements, whether deliberate or not; feedback between cheap genetic engineering and genetically-defined super-stimulus making all the citizens a biologically vulnerable monoculture … — twenty items each with a 50% chance adds up to million-to-one odds (million-ish, but if you care about the difference you’re taking the wrong lesson from this).
Yes, one-million-to-one is almost irrelevant compared to ten sextillion. Odds of (100e9)^2-to-one would require 73 such events, not 20, but this combines with the previous Fermi estimates, it doesn’t replace them. 20 such events reduces the overall problem by a factor of a million, no matter what your previous estimate was, and both 20 events and 50% chances are just round numbers, not a real ones. Unfortunately, we don’t know how many small-filters we might face: as the Great Recession was starting, someone said that no two recessions are the same because we learn from all our mistakes and so each mistake has to be a new one. Sadly it’s worse even than that, as humanity as a whole does repeat even its economic mistakes, so even if we weren’t re-rolling some of our previously-successful dice because we keep thinking “we’re too big to fail“, humans don’t know all the ways we can fail to survive.
The Great Filter doesn’t have to be something that civilisations encounter exactly once and in much the same way a sentence encounters a full stop — it can be the death of a thousand paper-cuts.
If we do finally reach the stars, we may find the universe is much more interesting than it currently seems. Instead of Vulcans and warp drive, we might find hippy space-elves communing with their trees via mind-warping drugs… and if we don’t, instead of wiping ourselves out, we might become the hippy space-elves that some sentient octopus discovers while going boldly where no sentient octopus has gone before.
I’m a fan of the Mathematical Universe idea. Or rather, I was. I think I came up with the idea independently of (and before) Max Tegmark, based on one of my old LiveJournal blog-post dated “2007-01-12” (from context, I think that’s YYYY-MM-DD, not YYYY-DD-MM).
Here’s what I wrote then, including typos and poor rhetorical choices:
Ouch, my mind hurts. I've been thinking about The Nature of Reality again. This time, what I have is the idea that from the point of view of current science, the universe can be described as a giant equation: each particle obeys the laws of physics, which are just mathematical formula. Add to this that an mathematical system can exist before anyone defines it (9*10 was still equal to 90 before anybody could count that high), and you get reality existing because its underlying definitions do not contradict each-other.
This would mean that there are a lot of very simple, for lack of a better word, "universes" along the lines of the one containing only Bob and Sarah, where Sarah is three times the age of Bob now, and will be twice his age in 5 years' time. But it would also mean that there are an infinite number of universes which are, from the point of view of an external observer looking at the behaviour of those within them, completely indistinguishable from this one; this would be caused by, amongst other things, the gravitational constant being represented by an irrational number, and the difference between the different universes' gravitational constants varies by all possible fractions (in the everyday sense) of one divided by Graham's number.
Our universe contains representations of many more simple ones (I've described a simple one just now, and you get hundreds of others "universes" of this type in the mathematics books you had at school); you cannot, as an outside observer, interfere with such universes, because all you end up with is another universe. The original still exists, and the example Sarah is still 15. In this sense of existence, the Stargate universe is real because it follows fundamental rules which do not contradict themselves. These rules are of course not the rules the characters within it talk about, but the rules of the Canadian TV industry. There may be another universe where the rules the characters talk about do apply, but I'm not enough of a Stargate nerd to know if they are consistent in that way.
The point of this last little diversion, is that there could be (and almost certainly is) a universe much more complex than this one, which contains us as a component. The question, which I am grossly unqualified to contemplate but tried anyway (hence my mind hurting), is what is the most complex equation possible? (Apart from "God" in certain senses of that word). All I feel certain of at the moment, is that it would "simultaneously" (if you can use that word for something outside of time but containing it) contain every possible afterlife for every possible subset of people.
Tomorrow I will be in Cambridge.
Since writing that, I found out about Boltzmann brains. Boltzmann brains are a problem, because if they exist at all then it is (probably) overwhelmingly likely that you are one, and if you are one then it’s overwhelmingly likely that the you’re wrong about everything leading up to the belief that they exist, so any belief in them has to be irrational even if it’s also correct.
Boltzmann brains appear spontaneously in systems which are in thermal equilibrium for long enough (“long enough” being 101050 years from quantum fluctuations), but if you have all possible universes then you have a universe, an infinite number of universes, where Boltzmann brains are the most common form of brain — Therefore, all the problems that apply to Boltzmann brains must also apply to the Mathematical Universe.
We naturally use something close to Bayesian logic when we learn and intuit. Bayesian logic doesn’t update when the prior is 0 or 1. Some people can’t shift their opinions, no matter what evidence they have. This is compatible with them having priors of 0 or 1.
It would be implausible for humans to store neural weights with ℝeal numbers. How many bits (base-2) do we use to store our implicit priors? My gut feeling says it’s a shockingly small number, perhaps 4.
How little evidence do we need to become trapped in certainty? Is it even constant (or close to) for all humans?
Every so often, someone tries to boast of human intelligence with the story of Shakuntala Devi — the stories vary, but they generally claim she beat the fastest supercomputer in the world in a feat of arithmetic, finding that the 23rd root of
916,748,676,920,039,158,098, 660,927,585,380,162,483,106, 680,144,308,622,407,126,516, 427,934,657,040,867,096,593, 279,205,767,480,806,790,022, 783,016,354,924,852,380,335, 745,316,935,111,903,596,577, 547,340,075,681,688,305,620, 821,016,129,132,845,564,805, 780, 158,806,771
was 546,372,891, and taking just 50 seconds to do so compared to the “over a minute” for her computer competitor.
Ignoring small details such as the “supercomputer” being named as a UNIVAC 1101, which wildly obsolete by the time of this event, this story dates to 1977 — and Moore’s Law over 41 years has made computers mind-defyingly powerful since then (if it was as simple as doubling in power every 18 months, it would 241/1.5 = 169,103,740 times faster, but Wikipedia shows even greater improvements on even shorter timescales going from the Cray X-MP in 1984 to standard consumer CPUs and GPUs in 2017, a factor of 1,472,333,333 improvement at fixed cost in only 33 years).
So, how fast are computers now? Well, here’s a small script to find out:
#!python from datetime import datetime before = datetime.now() q = 916748676920039158098660927585380162483106680144308622407126516427934657040867096593279205767480806790022783016354924852380335745316935111903596577547340075681688305620821016129132845564805780158806771 for x in range(0,int(3.45e6)): a = q**(1./23) after = datetime.now() print after-before
It calculates the 23rd root of that number. It times itself as it does the calculation three million four hundred and fifty thousand times, repeating the calculation just to slow it down enough to make the time reading accurate.
Let’s see what how long it takes…
MacBook-Air:python kitsune$ python 201-digit-23rd-root.py 0:00:01.140248 MacBook-Air:python kitsune$
1.14 seconds — to do the calculation 3,450,000 times.
My MacBook Air is an old model from mid-2013, and I’m already beating by more than a factor of 150 million someone who was (despite the oddities of the famous story) in the Guinness Book of Records for her mathematical abilities.
It gets worse, though. The next thing people often say is, paraphrased, “oh, but it’s cheating to program the numbers into the computer when the human had to read it”. Obviously the way to respond to that is to have the computer read for itself:
from sklearn import svm from sklearn import datasets import numpy as np import matplotlib.pyplot as plt import matplotlib.cm as cm # Find out how fast it learns from datetime import datetime # When did we start learning? before = datetime.now() clf = svm.SVC(gamma=0.001, C=100.) digits = datasets.load_digits() size = len(digits.data)/10 clf.fit(digits.data[:-size], digits.target[:-size]) # When did we stop learning? after = datetime.now() # Show user how long it took to learn print "Time spent learning:", after-before # When did we start reading? before = datetime.now() maxRepeats = 100 for repeats in range(0, maxRepeats): for x in range(0, size): data = digits.data[-x] prediction = clf.predict(digits.data[-x]) # When did we stop reading? after = datetime.now() print "Number of digits being read:", size*maxRepeats print "Time spent reading:", after-before # Show mistakes: for x in range(0, size): data = digits.data[-x] target = digits.target[-x] prediction = clf.predict(digits.data[-x]) if (target!=prediction): print "Target: "+str(target)+" prediction: "+str(prediction) grid = data.reshape(8, 8) plt.imshow(grid, cmap = cm.Greys_r) plt.show()
This learns to read using a standard dataset of hand-written digits, then reads all the digits in that set a hundred times over, then shows you what mistakes it’s made.
MacBook-Air:AI stuff kitsune$ python digits.py Time spent learning: 0:00:00.225301 Number of digits being read: 17900 Time spent reading: 0:00:02.700562 Target: 3 prediction:  Target: 3 prediction:  Target: 3 prediction:  Target: 3 prediction:  Target: 9 prediction:  Target: 9 prediction:  MacBook-Air:AI stuff kitsune$
0.225 seconds to learn to read, from scratch; then it reads just over 6,629 digits per second. This is comparable with both the speed of a human blink (0.1-0.4 seconds) and also with many of the claims* I’ve seen about human visual processing time, from retina to recognising text.
The A.I. is not reading perfectly, but looking at the mistakes it does make, several of them are forgivable even for a human. They are hand-written digits, and some of them look, even to me, more like the number the A.I. saw than the number that was supposed to be there — indeed, the human error rate for similar examples is 2.5%, while this particular A.I. has an error rate of 3.35%.
* I refuse to assert those claims are entirely correct, because I don’t have any formal qualification in that area, but I do have experience of people saying rubbish about my area of expertise — hence this blog post. I don’t intend to make the same mistake.
Matthew beheld not the mote of smartdust in his own eye, for it was hiding itself from his view with advanced magickal trickery.
His brother Luke beheld the mote, yet within his brother’s eye was a beam of laser light that blinded him just as surely.
Luke went to remove the mote of dust in Matthew’s eye, but judged not correctly, and became confused.
Mark looked upon the brothers, and decided it was good.
Idle thought at this stage.
The Kessler syndrome (also called the Kessler effect, collisional cascading or ablation cascade), proposed by the NASA scientist Donald J. Kessler in 1978, is a scenario in which the density of objects in low earth orbit (LEO) is high enough that collisions between objects could cause a cascade where each collision generates space debris that increases the likelihood of further collisions.
If all objects in Earth orbit were required to have an electrical charge (all negative, let’s say), how strong would that charge have to be to prevent collisions?
Also, how long would they remain charged, given the ionosphere, solar wind, Van Allen belts, etc?
Also, how do you apply charge to space junk already present? Rely on it picking up charge when it collides with new objects? Or is it possible to use an electron gun to charge them from a distance? And if so, what’s the trade-off between beam voltage, distance, and maximum charge (presumably shape dependent)?
And if you can apply charge remotely, is this even the best way to deal with them, rather than collecting them all in a large net and de-orbiting them?
It’s as fascinating as it is sad to watch a relative fall, piece by piece, to Alzheimer’s. I had always thought it was just anterograde- and progressive retrograde amnesia of episodic memory, but its worse. It’s affecting:
- Her skills (e.g. how to get dressed, or how much you need to chew in order to swallow).
- Her semantic knowledge (e.g. [it is dark outside] ⇒ [it is night], or what a bath is for).
- Her working memory (seems to be reduced to about 4 items: she can draw triangles and squares, but not higher polygons unless you walk her through it; and if you draw ◯◯▢◯▢▢ then ask her to count the circles, she says “one (pointing at the second circle), two (pointing at the third circle), that’s a square (pointing at the third square), three (pointing at the second circle again), four (pointing at the third circle again), that’s a pentagon (pointing at the pentagon I walked her through drawing); and if she is looking at a group of five cars, she’ll call it “lots of cars” rather than instantly seeing it’s five).
- The general concept of things existing on the left side as looked at. (I always thought this was an urban legend or a misunderstanding of hemianopsia, but she will look at a plate half-covered in food and declare it finished, and rotating that plate 180° will enable her to eat more; if I ask her to draw a picture of me, she’ll stop at the nose and miss my right side (her left); if we get her to draw a clock she’ll usually miss all the numbers, but if prompted to add them will only put them on the side that should be clockwise from 12 to 6).
- Connected-ness of objects, such as drawing the handle of a mug connected directly to the rim.
- Object permanence — if she can’t see a thing, sometimes she forgets the thing exists. Fortunately not all the time, but she has asserted non-existence separately to “I’ve lost $thing”.
- Vocabulary. I’m sure everyone has a fine example of word soup they can think of (I have examples, both of things I’ve said and also of frustratingly bad communications from a client), but this is high and increasing frequency — last night’s example was “this apple juice is much better than the apple juice”.
I know vision doesn’t work the way we subjectively feel it works. I hypothesise that it is roughly:
- Eyes →
- Object and feature detection, similar to current machine vision →
- Something that maps detected objects and features into a model of reality →
- “Awareness” is of that model
It fits with the way she’s losing her mind. Bit by bit, it seems like her vision is diminishing from a world full of objects, to a TV static with a few objects floating freely in that noise.