Tag Archives: lifehack

Silly sunglasses

Most sunglasses do not cover the eye fully. For example, any design where the lenses are close to flat (aviator, retro) or small does not protect the eye from rays coming from above or the side. Sunlight commonly comes from above, so these sunglass designs do not block a significant part of it. If the lenses are tinted (not clear), then they worsen the outcome for the eyes, because the dark glass in the centre of the visual field makes the pupils expand. When that happens, the pupils let in more light from any direction, including sunlight from the unprotected top and side directions.
In comparison, the polycarbonate safety glasses that currently cost 2 AUD in a construction shop have a wrap-around design and large lenses that leave only a small gap between the forehead and the glasses. Light from the side and nearly all other directions has to pass through the glasses before reaching the eye. The material for the safety glasses is polycarbonate, which block 99.9% of UV light. In order for sunglasses to provide better UV protection than the safety glasses, they have to block a larger percentage of UV light or cover more ray paths into the eye.
Suppose that sunglasses were made from a material that blocks 100% of UV. Then to improve on the safety glasses, the sunglasses would have to cover at least 99.9% of the ray paths into the eye that safety glasses cover. In other words, the sunglasses would have to have the same wrap-around design and as large or larger lenses.
An improved design for both safety glasses and sunglasses would take the wrap-around design one step further: cover the eyes from top to bottom as well as from side to side. One way to achieve such cover is a half-dome over each eye that touches the forehead above the eye and the cheek below, as well as the bridge of the nose and the temple.
A brimmed hat that blocks light coming from above compensates to some extent for flat-lensed or small sunglasses. The hat does not protect the eyes from light coming from the side and below the brim, so the classic sunglass designs are still inferior to wrap-arounds even combined with a hat.

Taking your own fingerprints

Some jobs, visas, etc, require a criminal record check from the FBI, which requires sending the FBI your fingerprints. Where you live, it may be difficult to find a professional who will take your fingerprints on an FBI-approved fingerprint card. But no problem, it is quite feasible to take your own fingerprints.
Supplies needed:
1. Scrap paper to practice on
2. Printouts of the FBI fingerprint card on standard office paper (5-10 copies, because you will make mistakes)
3. Ink pad from a stamp (with some black or blue ink in it). For most brands of stamps, the internet has instructions on how to slide the ink pad out.
4. Piece of smooth rubber a little larger than a fingertip, e.g. a piece of bicycle inner tube, a piece of unlubricated condom, or a rubber ball about 5 cm in diameter
5. Paper towels or tissues for wiping ink from fingertips
6. Stick of glue for gluing paper
7. Small sharp straight scissors, or a razorblade and a smooth cutting board, for cutting paper
8. Large envelope for mailing the fingerprint card to the FBI without folding it. Postage stamp(s).

The piece of smooth rubber is for painting the ink of the stamp pad onto the ridges of the fingerprints. Just dipping the fingers in ink or touching them to the stamp pad will put ink in the troughs of the fingerprints as well. Too inky fingers will create a uniform splotch on the paper, not the lines and whorls of a fingerprint. Also, if the stamp pad holds the impression of the writing on the stamp, then the fingers will get that writing on them as inkless areas.
The ink should not be quick-drying, e.g. alcohol-based from a marker pen. This will dry on warm fingertips before the finger reaches the paper. The ink must be liquid, not the paste from a ballpoint pen, because the paste sticks to the fingertip in small chunks. These will create uniform dark splotches on the paper, with the adjacent areas blank white. The ink used in stamp pads is good.
With inky fingers, it is easy to get ink stains on the table or anything else within reach, so the paper towels or tissues should be held ready to clean the ink up while it is still wet.
Procedure:
1. Read the FBI’s online instructions for taking legible fingerprints (https://www.fbi.gov/services/cjis/fingerprints-and-other-biometrics/recording-legible-fingerprints), the Guidelines for Preparation of Fingerprint Cards (https://ucr.fbi.gov/fingerprints_biometrics/guidelines-for-preparation-of-fingerprint-cards-and-association-criminal-history-information) and the Capturing Legible Fingerprints poster (https://www.fbi.gov/file-repository/capturing-legible-fingerprints.pdf).
2. Lightly rub the bulging side of the piece of rubber on the stamp pad to coat it with an even thin layer of ink. Then lightly paint the ink on one fingertip, the first priority being to coat all the ridges from the crease of the first joint to the nail and from one side of the nail to the other. The second priority is to avoid coating the troughs of the fingerprint. Some ink in the troughs is unavoidable, but minimising it will make the print clearer.
3. Roll the fingertip on the scrap paper from nail to nail, like the FBI instructions say. Compare the result to the Capturing Legible Fingerprints poster. The goal is to get a roughly rectangular imprint with the ridges and troughs of the fingerprint visible. Empty spots on the fingerprint indicate too little ink, inky splotches indicate too much. Lightly pressing the second joint of the finger down with the thumb and forefinger of the other hand may help, or alternatively holding the tip of the nail down with the thumb and forefinger of the other hand. Practicing repeatedly with the same finger helps. The ink on the fingertip needs renewing from time to time. If there is too much ink on the fingertip, rolling it on the scrap paper will reduce the amount.
4. Estimate how much ink on the fingertip leaves the best print. If the first roll after inking a finger always creates splotch, estimate how many rolls on the scrap paper are needed (without renewing the ink) to make the fingerprint legible.
5. Once the fingerprints on the scrap paper are looking good, use the same amount of ink and pre-rolls to put the same finger’s print on all the FBI fingerprint cards.
6. Wipe this finger clean of ink.
7. Repeat points 2-6 with each finger. When reaching the thumbs, also put their flat impressions on the fingerprint card (flat thumb impressions require less practice). Doing one finger at a time minimises ink stains on the fingerprint card and the furniture, and gives practice for each finger just before that finger’s print is taken.
8. Ink the four fingers of one hand and practice taking the four-finger flat impression a couple of times. Then put the four-finger impression on all the fingerprint cards. Clean the fingers. Repeat with the other hand.
9. Choose the fingerprint card with the largest number of clear fingerprints. It doesn’t matter how bad the unclear prints on the card are – these will be covered in the next step.
10. For each unclear print on the chosen card, pick the clearest print of the same finger from the remaining cards. Cut out that fingerprint, following the edges of the box it is in. Glue the cutout over the unclear print on the chosen card, making sure all four corners of the cutout are glued down. Hopefully you only need to cut and glue at most 3 prints.
11. Fill out the form at the top of the fingerprint card with black or blue pen, as the instructions say. The required codes for hair and eye colour, etc, can be found in the Guidelines for Preparation of Fingerprint Cards.
12. Without folding the fingerprint card, put it in the envelope together with the printout of the email confirmation of paying the appropriate fee on the FBI website. Address the envelope correctly and mail it. From Australia, sending the A4 envelope to the FBI using regular mail cost under 3 AUD in 2018. In my case, the pdf of the criminal record check was accessible from the FBI’s website less than two weeks after mailing my fingerprint card.

Urination technique 101

Many urinals are shaped so that if your centreline is aligned with the urinal’s centreline, then no matter where you aim, the spray splashes right back to your centre.

The solution is to stand slightly to one side, not directly in front of the urinal, but still aim straight ahead (perpendicular to the wall when viewed from above, not necessarily when viewed from the side). The urine starts flowing or splashing forward almost parallel to the wall of the urinal. This is the principle in a squash game – the more bounces off the wall, the slower the ball moves. If the energy for backward reflection is dissipated, then the ball falls down under gravity. The same applies to a urine stream – the more forward splashes off the wall of the urinal, the more energy dissipated and the more the urine flows downward.