21

Physics, Astronomy & Cosmology / Re: Why do people science-people insist that Venus has the hottest surface?

« on: 28/08/2022 18:35:40 »

And as you go deeper this superfluid reaches pressures where it starts to exhibit properties like a massive crystal, yet it is still not a solid, as the atoms do still flow around.

22

Cells, Microbes & Viruses / Re: How can we test new vaccines quickly?

« on: 25/08/2022 14:46:43 »

I was lucky, zero side effects, from both the 2 initial shots and the booster. Guess that I already had it before then, even if the test did have a negative result. Worst case of flu I ever did have in March....

23

Geek Speak / Re: Why different computers/devices may show different times (at seconds precision)?

« on: 17/08/2022 06:20:10 »

Yes a bug in the firmware, but simple to solve by simply turning it off then on again, as it will then sync to the time from your phone, as a 24 hour clock adjustment is disregarded as implausible in the majority of cases for correction. Yes the software is part of the OS these days, normally running as part of the kernel functions, as an accurate clock is needed for many processes in the computer file system, and thus got pulled out of user space.

24

Geek Speak / Re: Why different computers/devices may show different times (at seconds precision)?

« on: 16/08/2022 17:21:00 »

Most modern computer OS's will set time automatically, along with pretty every mobile phone as well, relying on accurate atomic clocks that are used to give an accurate clock. No need for any software these days, as the PC clock and phone will be slaved to an accurate reference regularly.

25

Marine Science / Re: Can whales eat when they are in fresh water ?

« on: 10/08/2022 12:00:52 »

Update, the whale died during this operation.

26

Radio Show & Podcast Feedback / Food waste, from The Naked Scientists 2 August 2022

« on: 05/08/2022 17:18:29 »

Listening to this Tuesday's The Naked Scientist, on Friday 5 August, and am certainly doing my little bit to combat food waste. Just got in from the "last day" sale at my local branch of a large retailer, where I picked up a good chunk of vegetables in prepack, that are on the "Sell By" date. Very much reduced in price, and thus about to be tossed, but still good to eat for a while more.

So the mushrooms, chopped cabbage and stir fry vegetables are all in the freezer, because they do freeze well, and I can eat them later on, and use in stew or stir fry, with almost no difference in taste. The fridge is also full now, a pocket of oranges, grapefruit, onions, peppers, tomatoes and eggs, all of them reduced in price, from full price to 25p per pack. Well worth it, the fresh stuff will be used this weekend and during the week, the eggs are going to last a week or more in the fridge, and do taste nicer than the regular ones. Doing the best I can to eat healthier, so lots of vegetables, chicken and such, and cutting down on junk foods. Total was around 15 pounds, including some other items that I have been watching drop in price, so got some of them as well.

I decided not to give in to my sweet tooth, so did not buy any of those yummy cakes and puddings on sale as well. Will have to eat a grapefruit or orange instead, which I do really like, though the grapefruit outside is not showing any signs of bearing fruit this year, it makes sour grapefruit, which are really nice and tart. Even saved more money, walking to the shop and back.

27

Just Chat! / Re: Do British pubs typically serve restaurant quality food?

« on: 04/08/2022 12:04:32 »

Pub food can be wildly variable, from some just doing stuff that is basically a reheated commercial pie and instant gravy with microwave chips, to some being near chef level cooking with quality ingredients.

28

Physiology & Medicine / Re: Why has no Warp Speed Pill been invented to Stop Periods?

« on: 04/08/2022 11:59:16 »

Look up trump as a verb or adjective, not a proper noun.  Synonyms are outshine, outclass, upstage, put in the shade, eclipse, surpass, outdo, outperform. beat, be better than, do better than, better, top, cap. informal be a cut above, be head and shoulders above, leave standing, walk away from.

NPC Non Playing Character in a game, a cardboard cutout that is used to fill a space.

29

Physiology & Medicine / Re: Why has no Warp Speed Pill been invented to Stop Periods?

« on: 04/08/2022 11:10:15 »

which makes them do sexual assault

You're kidding, right?

Plenty of men seem to think that listening to the small brain is a right, that trumps all others. They also tend to think all other people are NPC actors in their own personal drama.

30

General Science / Re: Science Photo of the Week

« on: 25/07/2022 09:39:42 »

Would say that is the ISS, blurred from an exposure that is long, simply because of the motion of the station during the exposure. Well done Sheepie to actually get such a good image, with what looks like a regular phone camera.

31

Question of the Week / Re: QotW - 21.03.02 - Difference between rechargeable and normal batteries?

« on: 25/07/2022 09:31:21 »

There is a triangle between current capacity, lifetime before discharge, and cost. A cheap AA or AAA cell has a low capacity, but it will in general last for 5 years in a remote control, with a very low average current draw, equal to the self discharge current in the most case, and it only has to supply brief pulses of current a few times a day to operate the IR LED used to communicate to the TV set. A poor candidate for rechargeable cells, as they typically are optimised for high cycle count for charging, and low internal impedance, so self discharge on them means they will go flat in under 6 months, unless designed to minimise this, which adversely affects cycle life and discharge current. Thus a primary cell is best here, low cost and good enough.

Contrast this with say a toy, or camera, where there is a heavy load, and a rechargeable cell wins out, low impedance, decent enough capacity, and charge cycles are enough to last a few years in use. Primary cells do not last long here.

Also you do get rechargeable alkaline cells, which swap capacity for charge  ability, in that they have much thicker cases, so as to handle the high pressure evolved inside, and also have thicker electrodes, so that the reaction can be reversed without causing the thin casing to erode away. The reversal is possible on regular cells, but they can only be partly recharged, as the optimised construction for highest capacity at a cost point means there is no extra electrolyte available to be consumed in the end of charge reactions, when hydrogen is being produced internally in the electrolyte, as there is little dissolved active material left. You can get partial recovery, provided you have not used around 30% of the capacity, and each cycle you only get around 80% back, though you have to put in 200% of the energy to reverse the reactions internally, as opposed to the rechargeable NiCd or NimH which is overall able to go to zero charge per cell. But absolutely no reverse charge, which destroys both primary and rechargeable cells. There you get around 75% of the charge in coulombs back, though there you need to charge slowly, so as to allow the chemistry to complete without heating up, otherwise fast charging (anything short of 12 hours per cell, at a current of 10% of the rated capacity in mAh) will generate a lot of heat, which reduces cell life by degrading separators, growing dendrites of the active metals and also generating hydrogen and oxygen gas, which can vent from the cell, removing electrolyte from the cell.

This applies to the common cell types, Zinc carbon and alkaline primary cells, and Nickel cadmium or nickel metal hydride secondary cells. You also get lithium based cells, also available commonly as a primary coin cell, like CR2032, or as lithium rechargeable cells in various chemistries, like pouch cells commonly seen inside equipment and ecigs, cells like the 18650 cell so common in torches, and also prismatic cells like used in mobile phone removeable batteries. Those are definitely all different, and need special care taken with them, so are not really a consumer useable product without understanding the safety and handling required.

32

Technology / Re: What's the different between CR2 and RCR2 batteries?

« on: 21/07/2022 06:21:21 »

No, they just are marked that because they meet the dimensions set out by the IEC for the battery, which has a set of dimensions with a tolerance, and a very broad range of capacities, though they should meet the "typical" capacity spec, but that is not guaranteed.

33

Physiology & Medicine / Re: How often do multiple fertilization's result in only one birth

« on: 19/07/2022 09:25:57 »

Probably common, but the one egg is implanted before the other, which then, because the uterus now changes to prepare for the fertilised egg to be priority, now simply does not implant, as it was simply too late.  Close enough together implanting and you get twins or more, so there likely are many occasions multiple eggs get released from different sites on the ovaries, due to varying hormone concentrations and sensitivity of the cells.

34

Physics, Astronomy & Cosmology / Re: Star distance appearences

« on: 14/07/2022 07:22:08 »

Retsina was probably invented by the first person to make wine, using a pine wood vessel to hold the crushed grapes to ferment, likely originally by accident in collecting lots of grapes to make raising, and them finding the crushed ones at the base, and leaving the liquid for a few days, then trying the liquid.

35

Technology / Re: rechargeable recycle time

« on: 14/07/2022 07:08:46 »

Reliable the only ones that are around at a reasonable price are Eneloop cells, much more expensive than the others, but at least the better made cells. You want the Japanese made cells in any case. Get a few packs, and preferably use a charger that will not fast charge them. If you need multiple packs for a lot of use, best to use an external power pack instead, with much larger capacity cells in it to handle the high current and fast charge cycles. Then you can go for Lithium packs, which are light for the power density, and also will survive multiple charge cycles better.

36

Chemistry / Re: Why does austenitic stainless steel fail to burn?

« on: 12/07/2022 13:56:26 »

The oxide layer is the protection, it adheres well, and prevents the further oxidising of the iron in the alloy, so providing protection. Just like aluminium, which is incredibly reactive ( the good old gallium trick, or for more show the mercury blob and a scratch to penetrate the oxide, growing oxide flowers), the oxide keeps the metal non reactive, at least till you remove the oxide by some method. Simplest is to wear it off, which then allows a short period for oxide regrowth, or expose to a chloride atmosphere, which slowly reacts with the oxides to form metal chlorides, which are soluble in water, and thus the metal slowly erodes away as it reacts.

Or you can create an electrochemical cell, most common when welding stainless steel, which changes the composition of the alloy, allowing electrochemical cells to form. You prevent that in welding by both the choice for the filler material, using a rod that has higher amounts of nickel and chromium, amongst other additives, to allow the cooled puddle to be the same electrochemically as the parent metal, and also by annealing the whole item, so that the stress from the rapid cooling that takes place, as the puddle leaves the joined area, is relieved, as the tress is also a source of electrochemical cell.

Take a piece of annealed stainless steel, and either drill a hole in it, or simply crease it, and expose in an environmental chamber, and you will see the preferential corrosion taking place slowly at the hole and the bend, plus at the cut edges, if they were not there at annealing time.

37

General Science / Re: Can a white LED be powered by the same size of it collecting radiation energy?

« on: 10/07/2022 13:52:33 »

I have driven a red LED, using a green LED as power source, very inefficient, and you need either another green or blue LED as excitation for the green LED, and preferably using clear packaged units as well. Efficiency takes a big hit, the LED is not really optimised for use as a photodiode, but does work sort of. You can use this though with a microcontroller to sense ambient light, using a pin configurable as both input and output to swap rapidly between driving the LED, and switching it to an input to the internal ADC, to provide a very poor ambient light source sensor, that can easily be used to control the brightness of a display backlight.

38

Chemistry / Re: Why does austenitic stainless steel fail to burn?

« on: 10/07/2022 13:48:33 »

Plasma cutter works on all grades of stainless steels, using the available oxygen in the compressed air, and the electric arc, to cut it with ease. Lot faster than the grinder, and cheaper to run than the gas axe as well, just needs a lot of compressed air, and power for the arc. even works on other metals, including things like titanium and aluminium, and even copper, though the cut and finish can vary, it depends a lot on flow rates, cutting speeds and arc power.  Laser cutting simply provides the energy input using a laser of some form, generally IR to provide the energy to melt the material, and the air jet does the rest.

39

Question of the Week / Re: QotW - 22.07.04 - Why can't I open a fridge door immediately after closing it?

« on: 04/07/2022 21:04:06 »

Normally when you open the door, all the cold air inside the fridge flows out, and then is replaced by warm air. Then when you close the door the warm air now has to radiate heat to the cold interior, and in doing so cools down and becomes slightly smaller in volume, needing to be equalised in pressure by outside air that slowly bleeds in via the vent tube for the condensate water. Thus the inside pressure is lower, and the force on the door from the difference makes it harder to open till the pressure inside equalises. For chest freezers the same, just there is a small vent instead in the seal, lots of small holes punched in the seal at places.

40

Technology / Re: What Question Could You Ask To Determine Sentience Of An AI ?

« on: 01/07/2022 18:01:51 »

Today I encountered an x-ray machine exhibiting boredom and possible suicidal ideation. Halfway through a clinical exposure, it decided it had had enough and switched off. Rebooted, it cut off even earlier each time. Clearly fed up with studying human anatomy. Next week I'll pack a dead rat in my toolbox and see if a change of subject might perk it up a bit.

I think you will find out that the tube has decided that it is dejected, and is no longer interested in emitting electrons any more, and the high voltage generator is also tired of being dunked in oil as well. It wants a head transplant.