Arhiiv kuude lõikes: October 2018

Milleks sündimust või rahvastiku kasvu tahetakse

Eesti ja teiste arenenud ja kahaneva rahvastikuga riikide ajakirjanduses kaeveldakse aeg-ajalt madala sündimuse üle. Harva küsib keegi, miks negatiivne iive probleem on. Kokkuvõttes on Maa praegu ülerahvastatud ja ressursikasutus pole jätkusuutlik. Arenenud riigid kasutavad suurema osa Maa loodusvaradest ja ühe inimese kohta eriti palju.
Oletame, et riik hoolib ainult iseendast, mitte ülejäänud inimkonnast, rääkimata Maa keskkonnast. Miks peaks selline riik tahtma rahvastiku kasvu? Mõned võimalikud põhjused: praegustele inimestele pensioni maksmiseks, arvuka sõjaväe jaoks enda teiste riikide eest kaitsmiseks, eesmärgina iseeneses.
Kui rahva püsimine on eesmärk iseeneses, siis tuleks kõigepealt täpselt määratleda, mis on rahvas ja mida tähendab püsimajäämine. Näiteks kultuuri säilitamiseks piisaks maailma pagulaste piisavalt noorte laste vastuvõtust ja nende algse keele ja kultuuri asendamisest kohalikuga range haridussüsteemi abil, nagu diktatuurid teevad oma vallutatud alade assimileerimiseks. Samuti saab võtta vastu sisserändajaid tingimusel, et nad nõustuvad kohalikeks hakkama, kui seda kultuurivahetust riiklikult igati toetada, rangelt kontrollida ja kultuuri mittevahetajaid karistada, näiteks väljasaatmisega. Jällegi, selline strateegia on vabas ja demokraatlikus riigis pea võimatu, ning ma ei soovita seda, kuid see on üks teoreetiline lahendus rahvastiku kahanemisele.
Sisserände piiramine koos sündimuse soodustamisega viitab sellele, et eesmärk on praeguse rahvaga geneetiliselt sarnase rahvastiku kasv, mitte keele või kultuuri püsimine. Eriti kui kultuur üha üleilmse meelelahutustööstuse sarnasemaks muutub. Geneetiliselt sarnaste inimeste sigitamise poliitika kõige tuntum ajalooline järgija oli muidugi Natsi-Saksamaa.
Rahvastiku kahanemine on ainult viimase sajandi trend, nii et pikemas perspektiivis võib probleem ise laheneda. Siiski, lootus pole strateegia, nii et oleks vaja vähemalt teoreetilisi mehhanisme, mis tulevikus rahvastiku kasvule viia võivad. Demokraatlikus vaba ajakirjandusega riigis on propaganda iibe tõstmiseks ebaefektiivne, kuna teabeallikaid ja iibest erinevate elueesmärkide (tarbimine näiteks) propageerijaid on palju (turundajad, massimeelelahutus, välismaa uudistekanalid). Kultuuri muutus sündimust soosivaks on ebatõenäoline.
Teaduse areng pakub aga võimaliku lahenduse – kui kloonimine piisavalt odavaks muutub, siis piisab paarist inimesest, kes rahvastikku kasvatada tahavad ja selleks endast koopiaid teevad. Kui nad oma kloonidele enda väärtusi sisendavad, siis suurem osa neist kloonidest hakkab end samuti kloonima, jne. Millises ajaperspektiivis peaks selline hüppeline iibetõus keskmiselt rikastele kättesaadavaks muutuma, et rahva kadumist vältida? Kui rahvastik kahaneks kaks korda iga põlvkonna (30 a) jooksul, mis on ebarealistlikult kiire, siis 10 põlvkonnaga jõuaks see miljonist tuhandeni. Arvestades teaduse arengut viimase 300 aasta jooksul ja teaduse arengu kiirenemist viimasel poolsajandil, on inimeste võimalused 300 aasta pärast ulmefilmiski kujuteldamatud. Rahva täielik kadumine praeguse negatiivse iibetaseme tagajärjel on seega väga vähetõenäoline. Kui suremus näiteks tuumasõja tõttu radikaalselt suureneb, siis muidugi võib isegi kogu inimkond paari tunniga välja surra.
Kui rahvastiku kasvu eesmärk on praegustele töötajatele pensioni maksta, siis loeb mitte laste arv, vaid nende tulevane tootlikkus ja kohalikus riigis maksustatav sissetulek. Kui robotid inimestest tootlikumaks muutuvad, siis on pensionäride jaoks kasulikum soosida automatiseerimist kui sündimust. Isegi kui tehnoloogia areng millegipärast peatub, pole rahvaarvu kasv ise sotsiaalkindlustussüsteemi jätkusuutlikkuse tagatis. Oluline on riigi sisemajanduse kogutoodangu kasv ühe pensionäri kohta. Valimatu sündimuse soodustamine võib hoopis kahjulik olla, kui see harimatute, kuritegelike või lihtsalt laiskade inimeste osakaalu suurendab. Intelligentsus on umbes pooles ulatuses pärilik, nii et inimõigusi eirav riik, mille ainsaks eesmärgiks on rikkuse ja võimsuse kasv, peaks sigida lubama ainult teatud testid läbinud vanematel. Inimsõbralikum strateegia on aidata riskirühma lastel oma potentsiaali realiseerida – pakkuda juba enne sündi vaesematele ja muidu hädas vanematele rohkelt nõu ja abi, lastele tasuta head haridust võimalikult noorelt alustades jne. Sellist lähenemist soovitab näiteks Nobeli laureaat James Heckman, kes on näidanud, et varase lapseea mitmesugustel õppe-, tervise- ja abiprogrammidel on aastakümneid kestev positiivne mõju nende laste tulevasele haridusele, tulule, seaduskuulekusele, tervisele jne, mis (inflatsiooni ja juhuslikkust arvesse võttes) nende programmide kulu mitmekordselt ületab. Need programmid muudavad juba sündinud lapsed paremateks kodanikeks (parem kodanik tähendab siin ülejäänud ühiskonnale kasulikumat või vähem kulukat inimest), selle asemel et uusi toota. Enamik riike investeerib neisse programmidesse nende tulu arvestades äärmiselt vähe. Riigirahanduse olukorra parandamiseks peaks eesmärk olema mitte rahvastiku, vaid tootlikkuse kasv investeeritud euro kohta. Riik peaks esmajärjekorras ellu viima need haridus-, tervise-, seaduskuulekus- ja muud programmid, mille oodatav diskonteeritud tulu miinus kulu kõige suurem on.
Kohalikele pensionäridele pensioni maksmisel loevad kohalikule riigile laekuvad maksud, mitte praeguste laste kogupanus inimkonna heaks. Seega kui rahvastiku kasvu eesmärk on sotsiaalkindlustussüsteemi rahastamine, siis peaks takistama ajude pikaajalist väljavoolu (aastaks välismaal käimine ja tagasipöördumine on kasulik, püsiv emigratsioon mitte). Jällegi, väljarände piiramine on demokraatlikus riigis pea võimatu, olgu siis jõu või ajupesu abil, mis on taas vastuargument pensionite nimel rahvaarvu kasvatamisele.
Riigi kaitsevõime jaoks loeb mitte rahvaarv, vaid sõjaväe tugevus, mis tehnika arenguga järjest vähem sõdurite arvust sõltub. Teatud määral rahva arvukus muidugi loeb, aga arvestades iibeprotsesside aeglust võrreldes sõjaliste ohtude muutuse kiirusega, pole sündimusel kaitsevõimele peaaegu mingit mõju. Kaitseväe kiireks kasvuks peaks hoopis suurendama ajateenistusse võetavate inimeste osakaalu (praegu Eestis alla 30% noortest meestest, võrreldes Soome 80%, Singapuri peaaegu 100% ja Iisraeli nii meeste kui naiste ajateenistusega). Seega selles valdkonnas on arenguruumi kordades.
Tehnika areng sõltub praegu veel inimmõistusest, nii et riigi tugevdamise nimel peaks suurendama nii teadlaste arvu kui tarkust. Rahvastiku kasv üldiselt suurendab (pikas perspektiivis ja aeglaselt) ka teadlaskonda. Siiski, tehnika arendamiseks on palju kiiremaid ja täpsemalt suunatud meetmeid kui iibe tõstmine. Kui vaadata ainult ajavahemikku, mis on piisavalt pikk, et rahvastiku kasvul arvestatav mõju oleks, siis on jällegi kloonimine ja robotid kiirem, tõenäolisem ja efektiivsem lahendus kui loomuliku iibe tõstmine. Samuti oleks sisserändajate assimileerimine kiirem kui rahvaarvu kasvatamine isegi maailma suurima loomuliku sündimusega.
Kokkuvõttes, välja arvatud praeguse rahvaga geneetiliselt sarnaste inimeste arvu suurendamisele ei tundu iibe tõstmisel olevat sellist eesmärki, mille saavutamiseks poleks palju efektiivsemaid vahendeid.

Bad popular science books

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There is a class of books that is marketed as popular science, but have the profit from sales as their only goal, disregarding truth. Easily visible signs of these are titles that include clickbait keywords (sex, seduction, death, fear, apocalypse, diet), controversial or emotional topics (evolution, health, psychology theories, war, terrorism), radical statements about these topics (statements opposite to mainstream thinking, common sense or previous research), and big claims about the authors’ qualifications that are actually hollow (PhD from an obscure institution or not in the field of the book). The authors typically include a journalist (or writer, or some other professional marketer of narratives) and a person that seems to be qualified in the field of the book. Of course these signs are an imperfect signal, but their usefulness is that they are visible from the covers.
Inside such a book, the authors cherry-pick pieces of science and non-science that support the claim that the book makes, and ignore contradicting evidence, even if that evidence is present in the same research articles that the book cites as supporting it. Most pages promise that soon the book will prove the claims that are made on that page, but somehow the book never gets to the proof. It just presents more unfounded claims.
A book of this class does not define its central concepts or claims precisely, so it can flexibly interpret previous research as supporting its claims. The book does not make precise what would constitute evidence refuting its claim, but sets up “straw-man” counterarguments to its claim and refutes them (mischaracterising the actual counterarguments to make them look ridiculous).
Examples of these books that I have read to some extent before becoming exasperated by their demagoguery: Sex at dawn, Games people play.

Recovering faster from a sprint by jogging than by walking

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It seems that the panting and muscle weakness right after a sprint passes faster when I jog than when I walk or stand (the recovery I am talking about here is the minutes it takes to get back to normal breathing, not the days it takes for muscle soreness to disappear). I did not find empirical research on whether jogging actually speeds recovery from a sprint – it could be just my false perception. For this blog post, I will assume my perception is correct and speculate about why.
Faster recovery of breath when jogging seems counterintuitive, because jogging takes more power (energy per unit of time) than walking, so consumes the body’s cardiovascular output and nutrient reserves faster. The increased consumption should delay the short-term recovery. However, the perception of recovery need not be positively correlated with the whole body’s oxygen and glucose consumption, only with the CO2 reaching the chemoreceptors (either central in the brain’s respiratory centre, or peripheral in the carotid arteries and the aorta).
If the blood vessels in the legs expand during a sprint, and the blood pressure falls after a sprint faster than the blood vessels contract, then blood may pool in the legs and less of it may reach the chemoreceptors. Blood is forced up from the legs by the contractions of the leg muscles, which are more intense and frequent during jogging than walking. Therefore jogging may increase the venous return, leading to a better blood supply to the torso and the brain, which the latter perceives as faster recovery from exercise.
Even if the contractions of the leg muscles during jogging and walking had the same intensity and frequency, the group of muscles activated during jogging does not completely overlap with those working during walking. One muscle group may surround the major veins in the legs more closely, thus pump blood up more effectively.
There may be evolutionary reasons why the jogging muscles are better at stimulating venous return – faster overall circulation is needed during more intense exercise, for example when jogging compared to walking. Better venous return speeds up the circulation.
A mechanical reason why jogging may improve recovery from a sprint better than walking is that the jogging muscles overlap with the sprinting muscles more than the walking muscles do. If blood pools in the sprinting muscles and needs to be returned to the core, then contracting the jogging muscles forces blood out of the sprinting muscles better than contracting the walking muscles does.

Kui tugev peaks olema sõjavägi

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Sõjavägi ei pea suutma võita – piisab, kui see suudab sõja ära hoida vastast heidutades. Demokraatlike riikide vahel piisab heidutuseks sellest, et sõjavägi suudab vastasele tekitada suuremat kahju kui vallutusest saadav kasu. Diktatuuris kannab sõja kahju rahvas, aga kasu saab valitsev klass, sest enamik vallutatud alalt röövitud saagist läheb juhtkonnale ja nendega seotud eliidile. Seetõttu ei piisa diktatuuri heidutamiseks sellest, et sõja kulu on suurem kui tulu.
Isegi diktatuur ei ründa alati, sest kui rünnak on rahvale piisavalt kulukas, eelistab rahvas ründekäsu saamisel valitsusele vastu hakata, selle asemel et vallutusretkele minna. Suremistõenäosus teist riiki rünnates pole sõja alguses selge, eriti kui propaganda on rahvale kiiret võitu lubanud, nii et revolutsioon sõja tagajärjel võib aega võtta. Siiski, diktatuuri rünnaku alla sattunud riik ei pea ainult lootma, et rünnaku peatab kodusõda diktatuuris, sest diktatuuri juhtkond teab, et kui nende sõdurite suremistõenäosus vallutuses on suurem kui mässus juhtkonna vastu, siis eelistab rahvas mingil hetkel vastuhakku valitsusele. See kodusõja hirm hoiab diktaatorit liiga kaotusterohket välissõda jätkamast. Seega diktatuuri rünnakut saab vältida, tehes oma sõjaväe tugevamaks kui diktatuuri sisemise repressioonijõu. Lihtsustatult öeldes, diktatuuri naabri sõjavägi peab olema võimeline tapma ründajaid kiiremini kui diktatuuri salapolitsei suudab maha lasta siseriiklikke vastuhakkajaid.

Rigid skirt to prevent falls

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Falls are a major cause of hospitalisation in the elderly and people with impaired balance or strength. A fall may cause a vicious cycle: the bad experience leads to a fear of falling, which makes people avoid exercise. Not exercising leads to worse balance and muscle condition. Weakness and a lack of balance cause more falls.
To prevent falls, people should train their sense of balance and their stabilising muscles, but in a way that does not risk injury via falls during training. One device that would allow practising balance while preventing falling over is a rigid wide-flared skirt attached above a person’s centre of gravity (the attachment could be almost under the armpits). The hem of the skirt would be above the ground when the body is upright, but its edge would touch the ground if the body tilts too much in any direction. Support from the rigid skirt would then prevent further tipping in that direction. The lack of support in a central position (and for slight tilts around it) allows practising balance, for example by standing on one leg and trying to stay upright. The principle is the same as for helper wheels (training wheels) on childrens’ bicycles, which are off the ground while the bike is in a central position, but touch the road and stop too great a tilt to the side once the bike tips away from the centre. Other analogies to the rigid skirt are hands-free crutches pointing in all directions simultaneously, or a walking frame that surrounds the body, as opposed to being pushed in front.
The advantage of the skirt for fall prevention over crutches or a walking frame is that the skirt is hands-free. The advantage over a fixed training frame, or somewhat slack ropes tied to the upper body that also prevent a fall, is that the skirt moves with the person. This makes training easier by allowing walking and jogging.
The skirt can be home-made from many materials, such as tent poles or bamboo sticks tied or duct taped to a belt at the top and a hula hoop at the bottom. Using modern materials such as carbon fiber ski poles can make the skirt light, yet strong and rigid.
Of course the rigid skirt looks strange and attracts notice if not too many people are using it. On the one hand, the skirt does not have to be used in public if in-home training is enough. On the other hand, the first walking frame or the first crutches must also have looked strange to bystanders, but are now accepted mobility aids that almost nobody reacts negatively or even curiously to.
For using the skirt on the street, one problem is the wide-flared base (about 2m in diameter) that makes it difficult to pass other pedestrians. One (expensive) solution is to make the skirt out of sticks that can be moved independently and add a robotic controller that keeps the skirt narrow if the body is upright, but when the tilt angle becomes large enough, flares the skirt out in the direction of the tilt to stop the fall. Flaring the skirt means moving the sticks outward and lengthening them.

Miks on lauanõud ümmargused

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Ruudukujulisi asju mahub lauale rohkem kui sama kogupindalaga ümmargusi, samuti on ruudukujulisi objekte lihtsam kastidesse pakkida jne. Üks põhjus ümmargusteks nõudeks võib olla ajalooline – potikedraga on lihtne teha ümmargusi nõusid, aga mitte kandilisi. Potikeder ise on kasulik leiutis, sest sellega saab toota sümmeetrilisi ja siledaid nõusid. Sümmeetria võib olla lihtsalt ilu pärast, aga nõu siledusel on lisaks esteetilisele ka praktiline väärtus – siledalt pinnalt on lihtne toidujäänuseid kätte saada. Efektiivne nõudepesu polnud inimkonna ajaloo jooksul enamasti peamine eesmärk. Kuna enamik inimkonnast elas enamasti nälja piiril, oli toit väärtuslik, nii et iga raasuke tuli toidunõust kätte saada. Seda oli lihtsam teha siledate kausside ja taldrikutega, mille sai leivatükiga põhjalikult jäänustest puhtaks pühkida või lihtsalt läikima lakkuda. Samal põhjusel on ümmargused nõud paremad kui kandilised – näiteks karbi sisenurgast on keeruline sinna kleepunud toitu välja urgitseda, ükskõik kas lusika, sõrme või keelega.
Ka tänapäevaste nõudepesumasinate olemasolul tehakse isegi üldplaanilt kandilised toidunõud (hotellipannid, kaasavõtulõunakarbid) pesu lihtsustamiseks ümarate sisenurkadega, sest 90-kraadisest nurgast on isegi masinal raske kleepuvat materjali eemaldada.

Bodyweight exercise list

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Abdominals
Plank Ups: Start in high plank. Bend one arm to bring your elbow and your forearm to the floor. Bring the other arm down so you are in a forearm plank. Push back up to the start position, placing each hand where your elbows were.
Plank Taps: Start in high plank with your feet hip-distance apart. Then tap your left hand to your right shoulder while engaging your core and glutes to keep your hips as still as possible.
Lateral Plank Walks: Start in high plank. Step your right foot and your right hand to right side immediately following with your left foot and your left hand.
Plank Star Jumps: Start in high plank. Keeping your core engaged, jump your feet out wide and back in (like star jumps).
Plank with lifting right arm and left leg, then lifting left arm and right leg.
Plank with arm lifts to the side (90 degrees with the body) without turning torso.
Plank high knee run: in plank, alternately bring one knee to chest, then the other.
Plank knee to same shoulder: in plank, alternately bring left knee to left shoulder, return to plank, bring right knee to right shoulder.
Crocodile walk: from plank, step left foot close to left hand, left knee is close to left shoulder. Step right hand forward. Then step left hand and right foot forward, so the right knee is close to right shoulder. Repeat with right hand and left knee. Stay low, with bent elbows and one knee bent.
Plank knee to opposite elbow or shoulder: in plank, alternately bring one knee under the body to the opposite armpit, return to start, then the other knee to the opposite armpit. Intensification: straighten the leg that crosses under the body, without touching the leg to the ground.
Plank or tabletop side leg lifts: similar to plank knee to shoulder, but straight leg lifted to the side.
Bear pose: from tabletop pose (hands and knees on the ground), lift knees slightly off the ground, so you are standing on hands and toes, with hips and knees bent at 90 degrees.
Crunches: lying on your back, knees and hips bent, feet on the ground, lift torso toward knees, return.
Leg lifts on your back: lying on your back, lift both straight legs without arching the back (lower back stays on the ground). Then lower the legs back down. Repeat.
Supine leg rotations: lying on your back, lift straight legs 30 degrees off the ground, make circles with the legs, keeping the legs together and straight. Lower back stays on the ground, no arching of the back.
Jackknife: lying on your back, arms overhead, bend at the hips to lift both straight arms and straight legs, touch fingers to toes.
Windshield wiper: lying on your back, hips bent 90 degrees, feet touching, keep both shoulders on the ground and rotate from the waist to move both feet to one side to touch the ground, then lift back up. Repeat on the other side.

Chest/pectorals
Push-Ups or clapping push-ups.
One-arm push-ups.
Handstand push-ups.
Push-up into side plank, then back to push-up, then side plank on the other side.
Staggered push-ups: push-ups with one arm placed more forward than the other.
Burpees/ squat thrusts: do a push-up, then jump legs close to hands, then jump up, return to low squat, put hands on the floor, jump legs back to plank. Repeat.

Calves
Calf raises: Stand on one leg, rise up on your toes, return down.

Hamstrings
Low plank or chaturanga leg lifts. Start with hands (or elbows) and feet on the ground, body straight, elbows bent 90 degrees. Lift one leg toward the sky. The leg may be straight or bent. Do not rotate the foot outward, but keep pointing the toes in and up. Keep abdomen tense to lessen the use of the back muscles, focus on lifting with the hamstring instead.
Isometric heel press: stand on one foot, bend the other knee 90 degrees and press the heel up against the hand, keeping the hips straight. Tense the abdominals to discourage using the lower back muscles. Use the hamstring instead.

Quads, glutes, sides of hips
Squats or squat jumps, or one-legged squats.
Forward-backward squat jumps: from a squat, jump forward into a squat, then back to starting position.
Wide-legged squats or wide-legged squat jumps.
Lunges, perhaps adding a front kick after standing up from each lunge.
Lunge jumps: start on left foot and right toes, with the left hip, knee and ankle bent 90 degrees, the right hip straight and the right knee and ankle bent 90 degrees. Jump into the same position on the opposite side: right hip, knee and ankle bent 90 degrees, left hip straight, the left knee and ankle bent 90 degrees.
Lateral lunges: from standing, step wide to the left, bending the left knee, keeping the right leg straight. Step back to standing. May add a leg raise to the side after each lunge.
Curtsy Lunges: from standing, cross one leg in front of the other and do a squat.

Back
Superman: lying on your belly, straight arms pointing above head, lift both arms and straight legs. Keep the legs together.
Locust: lying on your belly, straight arms behind back, fingers interlocked, lift torso and straight legs.
Airplane: lying on your belly, straight arms in a T position to body, lift both arms and both legs. Keep the legs together and straight.
Prone snow angel: lying on your stomach, lift both arms, move straight arms from pointing toward feet to pointing above head, then back toward feet (from locust to airplane to superman pose, then back to airplane and to locust).
Forward bend/ good morning: from standing, bend forward at the hips with a straight back and straight legs, fingers interlocked behind the head. Then stand tall again. Intensification: keep straight arms overhead (in one line with the back) the whole time.
Bridge/ hip raise, or one-legged bridge. In one-legged bridge, the other leg can be straight or bent, parallel to ground or pointing to the sky.
Upward plank: facing the sky, support your weight on hands and heels. Keep arms, legs and body straight, with legs and body forming one line.
Upward plank leg raises: from upward plank, raise one leg from the hip, keeping the knee straight. The other leg and the body still form a straight line.
Ant walk/ crab walk: facing the sky, walk on your hands and feet, knees bent about 90 degrees, elbows almost straight. Keep your hips and back straight.

Obliques/side muscles
Side bend: stand straight, arms straight overhead, elbows straight, fingers interlocked, biceps squeezing the ears. Bend to one side, then stand tall again. To focus on the side muscles, not lower back or abdomen, bend exactly to the side, not forward or back.
Side Plank. Intensification: lift upper leg, perhaps grab toe of upper leg.

Shoulders
Dive bomber/ Hindu push-up/ Downdog-to-chaturanga and return to downdog. Start with hands and toes on the ground, hips bent 90 degrees, legs and arms straight, arms in one line with the back. Bend elbows and move chest between hands until the hips are straight (body and legs form one line) and chest hovers a few cm above ground. Then return to start.
Downdog push-ups/ inverted shoulder press/ pike press. Start with hands and toes on the ground, hips bent 90 degrees, legs and arms straight, arms in one line with the back. Bend elbows so head approaches floor between the hands. Keep hips at 90 degrees, back and neck in one line. Push back to starting position.
Arm circles: standing, straight arms in T position (straight line through both arms), make as small and fast circles with the arms as possible.

Triceps
Narrow push-up: hands close to each other on the ground, elbows brushing sides of torso.
Diamond Push-Up: thumbs and forefingers form a triangle.
Triceps Dip, or one-arm triceps dip: Sit on the ground with your legs in front and your back close to a chair, box or step. Place your palms on the box behind you, fingers facing toward your body. Straighten your arms to lift your legs and butt off the ground, then bend your elbows to lower back down (without letting your butt touch the ground). Keep your heels on the ground, elbows directly behind your body.
Reverse push-up: face the sky, hands and heels on the ground, body and legs in one straight line. Bend the elbows, then push back up until the elbows are straight again. Keep the body and legs straight while doing this.
Back-to-wall push-aways: stand with your back against a wall, feet away from the wall, body and legs in one straight line. Push away from the wall using your elbows or hands.

Warm-ups
Knee lift run on the spot.
Butt kick run, hips straight.
Forward kicks/ can-can, or forward kicks with jumps.
Scissor stepping to the side: from standing, cross left leg in front of the right, then step right leg to the right so the legs are not crossed any more. Then cross the left leg behind the right, then step the right leg to the right. Repeat. Then switch sides.
Forward sprint.
Backward run.
Gallop to the side: one leg steps wide to the side, then the other hops to meet it. Repeat. Then switch sides
Hop on one foot, forward and backward.

The motivation for this list was my inability to find a good ad-free list of bodyweight exercises online. By bodyweight I mean exercises that do not require rubber bands, a chin-up bar, weights or other equipment. Preferably the exercises would only require a floor, not even a wall or a chair, but I included some exercises above that do require these.

Jahust pole lihtne putru keeta

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Teoreetiliselt võib tunduda et jahust on lihtne putru teha, kuna jahuosakesel on suur pindala/ruumala suhe, seega peaks see võrreldes suurema kruubi või täisteraga kiiresti vett imama ja pehmeks keema. Empiiriliselt aga läheb tatrajahu klimpi ja kõrbeb põhja (muid jahusid pole ma pudruks keeta proovinud), segades kleepub lusika külge. Peale poti põhja kleepunud jahukile ära kraapimist taastekib see kile kiiresti, isegi madalaimal pliidikuumusel, ja hakkab jälle kõrbema.
Isegi üleöö vees seistes ei ima jahu korralikult vett – klimpide keskmed on kuivad. Nii et ka leotamine ei aita jahust putru teha. Suuremad tatraterad, mille vahele vesi lihtsasti pääseb, on pudruks palju paremad, sest ei moodusta klimpe ega kleepu nii lihtsasti poti ega lusika külge.
Amarant on väikseteraline (1mm läbimõõduga) ja selle keetmisel on osaliselt sarnased probleemid kui jahuga.

Heating my apartment with a gas stove

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There is no built-in heating system in my Australian-standard un-insulated apartment, and the plug-in electric radiators do not have enough power to raise the temperature by a degree. In the past two winters, I used the gas stove as a heater. It is generally unwise to heat an enclosed space without purpose-built ventilation (such as a chimney) by burning something, because of the risk of CO poisoning. Even before CO becomes a problem, suffocation may occur because the CO2 concentration rises and oxygen concentration falls. Therefore, before deciding to heat with a gas stove, I looked up the research, made thorough calculations and checked them several times. I also bought a CO detector, tested it and placed it next to the gas stove. The ceiling has a smoke alarm permanently attached, but this only detects soot in the air, not gases like CO.
For the calculations, I looked up how much heat is produced by burning a cubic metre or kilogram of CH4 (natural gas), how much the temperature of the air in the apartment should rise as a result, how much CO2 the burning produces, and what the safe limits of long-term CO2 exposure are.
The energy content of CH4 is 37.2 MJ/m3, equivalently 50-55.5 MJ/kg. A pilot light of a water heater is estimated to produce 5.3 kWh/day = 20 MJ/day of heat, but a gas stove’s biggest burner turned fully on is estimated to produce 5-15 MJ/h, depending on the stove and the data source.
The chemical reaction of burning natural gas when oxygen is not a limiting factor is CH4 +2*O2 =CO2 +2*H2O. The molar masses of these gases are CH4=16 g/mol, O2=32 g/mol, CO2=44 g/mol, H2O=18 g/mol, air 29 g/mol. One stove burner on full for 1 hour uses about 0.182 kg =0.255 m3 of CH4 and 0.364 kg of O2, which depletes 1.82 kg = 1.52 m3 of air. The burning produces 2.75*0.182 = 0.5 kg = 0.41 m3 of CO2. The CO2 is denser than air, which is why it may remain in the apartment and displace air when the cracks around the windows are relatively high up. On the other hand, the CO2 also mixes with the air, so may escape at the same rate. Or alternatively, the CO2 is hot, so may rise and escape faster than air. For safety calculations, I want to use a conservative estimate, so assume that the CO2 remains in the apartment.
The volume of the apartment is 6x5x2.5 m =75 m^3. The density of air at room temperature is 1.2 kg/m^3, thus the mass of air in the apartment is 90 kg. The specific heat of air is 1005 kJ/(kg*K) at 20C. The walls and ceiling leak heat, thus more energy is actually needed to heat the apartment by a given amount than the calculation using only air shows. It takes 900 kJ of heat to raise the temperature of the air, not the walls, by 10C (from 12C to 22C). This requires 9/555 kg = 9/(16*555) kmol of CH4 with estimated energy density 55500 kJ/kg. Burning that CH4 also takes 9/(8*555) kmol of O2 and produces 9*11/(4*555) kmol = 9/200 kg of CO2.
The normal concentration of CO2 in outside air is 350-450 ppm. Estimate the baseline concentration in inside air to be 1/2000 ppm because of breathing and poor ventilation. Adding 1/2000 ppm from heating, the CO2 concentration reaches 1/1000 ppm. This is below the legal limit for long-term exposure.
CO is produced in low-oxygen burning. As long as the CO2 concentration in the air is low and the oxygen concentration high, the risk of CO poisoning is small.
For the actual heating, I first tested running the smallest burner all day while I was at home, and paid attention to whether I felt sleepy and whether the air in the apartment smelled more stale than outside or in the corridor. There seemed to be no problems. For nighttime heating, I started with the smallest burner in the lowest setting, similarly paying attention to whether the air in the morning smelled staler than usual and whether I felt any different. Because there were no problems, I gradually increased the heating from week to week. The maximum I reached was to turn on the largest burner to less than half power, and one or two smaller burners fully. Together, these burners produced much less heat than the largest burner on full, as could be easily checked by feel when standing next to the stove. At night, the stove prevented the temperature in the apartment from dropping by the usual 2C, but did not increase it. The CO2 produced was probably far less than the bound I calculated above by assuming a 10C increase in temperature. Empirically, I’m still alive after two winters of letting the gas stove run overnight.

Charge electric cars fast by changing the battery

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An electric car drives into a charging station. The driver pushes a button to unlock the battery compartment hatch on the rear bumper. The hatch springs open, which is detected by a camera of the station. A robotic arm swings into motion and, guided by cameras, radar or ultrasound, latches on to well-marked standardised handles on the rear of the battery. The arm pulls out the 300kg, 1×2 metre battery from underneath the floor of the car and slides it onto a conveyor belt. The belt moves the battery to one side and brings up a new battery, which the robotic arm picks up and slides back into the car’s battery compartment. The driver pushes a button to close and lock the battery compartment and drives off. The whole charging process takes less than a minute – significantly faster than filling up a gasoline-powered car.
Due to the weight and size of an electric car’s battery, a robotic arm is probably necessary. It is also faster and more precise than a human.
The usage history of the battery should be recorded securely, in order to make users pay for its depreciation, not just the electricity they used. Blockchain may be useful for keeping track of usage, which is needed to deter the moral hazard of using the battery inappropriately and not paying for the damage, or swapping it for a cheaper alternative before having it changed back to a standard one in a charging station.
The compartment in which the battery is has to be water-tight and locked (like the trunk or hood of a car) to prevent theft. The compartment should also be unlockable remotely by the owner or other authorised person, in case the car is self-driving and has no humans in it.