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Question of the Week / Re: QotW - 18.09.24 - Why do I feel the pressure of wellies in water?

« on: Today at 17:11:07 »

The sensory system adapts quite quickly to even, constant stimuli. That is how we manage to work in a noisy environment or acclimatise to warm or cold weather. The dominant sensation of standing in a pool or bath is the temperature difference between air and water, but this sensation disappears after a few seconds. The even pressure distribution of water produces a weak sensation that is noticeable at the air/water junction but is quickly accommodated as it carries no threat or useful information.

Wellies tend to collapse unevenly producing isolated, moving,  small areas of pressure on the skin, which could be threatening (rapid current, or a snake) or otherwise important, so the system recognises the changes in pressure distribution

The same considerations apply to wearing a stocking which suddenly develops a hole.

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New Theories / Re: Are there any facts that the Earth's gravity reaches the Sun?

« on: Today at 16:54:56 »

Every astronomical observation and every laboratory experiment to date has shown that

F = G Mm/r²

applies for all values of r from a centimeter to about 45,000,000,000 light years.

If you have any observations to the contrary, please share them with us. If you have any unobserved hypotheses to the contrary, please share them with your psychiatrist.

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Plant Sciences, Zoology & Evolution / Re: Why do crabs move sideways?

« on: Today at 14:00:15 »

'cos if they moved forwards, they'd be lobsters.

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Physics, Astronomy & Cosmology / Re: Is the universe expanding faster than the speed of light?

« on: Today at 09:44:20 »

I am sorry you lost me. Why can't U be much greater than dark energy which can be X?

Because U and X are volumes of space, not quantities of energy, and X is arbitrarily the bit of space we can see.

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Physics, Astronomy & Cosmology / Re: Is the universe expanding faster than the speed of light?

« on: Today at 08:22:32 »

The beauty of U >>X is that you don't need to postulate stuff you can't see (dark energy) within the sphere that you can see (X), only that there is nothing special about X.

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Technology / Re: What is the optimal battlefield attack aircraft?

« on: Yesterday at 23:58:13 »

The mechanical engineer's dream: pre-machined pieces of unobtanium, held together with gossamer and powered by fairydust.

The pilot's nightmare: any approximation to the above. Especially if required to fly.

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Physics, Astronomy & Cosmology / Re: Is the universe expanding faster than the speed of light?

« on: Yesterday at 23:40:49 »

Is there any reason why it shouldn't?

Here's a thought experiment. Assume that the universe U is an infinite array of roughly isotropically distributed bits of stuff. Assume that for whatever reason (and Schwarzchild gives us a perfectly good one) we can only observe a finite sphere X within that array. And assume that "gravity sucks". Now since U >> X, there is more stuff outside X than inside it, so X will expand due to the "suction" of (U - X) - i.e.the stuff outside - so the density of X will decrease, and the rate of expansion will increase.

Suppose we have reached the stage  at which points on the boundary of X are receding from us at 0.55c. Nothing in that statement to contradict relativity. But diametrically opposite points, say to the north and south of us, are moving at 1.1c relative to each other. All this means, relativisitically, is that an observer at N will not have any information about S, which is fine, but the diameter of the observable universe is increasing faster than c.

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General Science / Re: If I wear ANY battery watch, in by a weeks time, the battery is dead. Why?

« on: Yesterday at 23:15:58 »

The only common chemicals that attack gold at body temperature are "aqua regia", a mixture of concentrated hydrochloric and nitric acids, and mercury, which forms an amalgam used in mining and metal recycling.

If your sweat rots a gold watch, you would be wise not to travel by air - it is illegal to import aqua regia or mercury into the passenger compartment.

If anything other than aqua regia or mercury attacks your gold watch, ask the Fraud Squad or the local Trading Standards Office to visit your jeweller.

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Technology / Re: What is the optimal battlefield attack aircraft?

« on: Yesterday at 18:07:15 »

τBulletproof, eh? So the fuel tanks and engine cowlings are made from at least 10 cm steel...we are back to the flying brick.

There were some tank-carrying gliders around in WWII, which caused the enemy some concern when the convoy was attacked from behind, but I think you need to play around a bit with your slide rule before cutting metal on  this project.

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Technology / Re: What is the optimal battlefield attack aircraft?

« on: Yesterday at 11:55:12 »

I've dealt with the undesirability of maintaining complex aircraft close to the front line, mindful of the fact that 10 miles is a day's fight for an army and a minute's flight for a jet. Close support does not mean having to defend the machine on the ground.

Harriers proved very useful for close naval defence and attack, but VTOL limits your bomb load which is why the (now scrapped, of course) Buccaneer was favored for ship-to-shore attack, and high level recon needs endurance, hence the old Gannet which could keep pace with the convoy for hours and provide primary radar with a 200 mile horizon.

Coastguard is all about low-level surveillance, the occasional depth charge, and SAR. Low and slow means a very different configuration from hi-g dogfights, at least two crew (looking downwards!) even for fishery protection, and lots of endurance (ideally two complete crews and 18 hour endurance). Your fighter-bomber carries weapons under its wings, so not a good idea to add floats and salt spray.

Given a mile of concrete and a clean hangar, you can fly a very sophisticated air superiority fighter that could not survive a deck landing or a desert takeoff. High altitude defence is another game, with different pieces.

Anyway it's all pie not in the sky. Noting that the UK is building aircraft carriers with no budget for aircraft, that well-known military authority Sandi Toksvig pointed out that it's a lot safer than having planes with nowhere to land.

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Technology / Re: What is the optimal battlefield attack aircraft?

« on: Yesterday at 09:08:11 »

 

I definitely meant laying back , not on stomach .  This would require small , at hand , controls & visor-mounted video display of forward/ down .  Unnatural , but deadly ...P.

The word is semisupine. Standard position in gliders where we need to minimise cross-sectional area and provide maximum comfort with minimum upholstery: the seat is an integral part of the fuselage structure. Problem is that your view downward  is restricted (poor choice for ground attack) and such matters as ejection seats (not fitted in gliders, and bailing out from a spin is extremely difficult) get complicated if you recline by more than a comfortable car seat - about 15 degrees. To say nothing of the vomit-inducing properties of a head-down vertical climb or a low-level passage under autopilot.

HUDs already contain a whole lot of unreliable distractions from the business of fighting. If you are going to remove the pilot's eyes from the front line, you may as well remove the pilot and use a remote control drone.

Everything in an aircraft is a compromise, which is why there are so many different types. 16g agility is best left to missiles, and an intercept and 6g dogfight at 40,000 ft is a very different matter from strafing, precision bombing, intel, paradrop or medevac. Horses for courses. By the time you have taught your carthorse and jockey to run, jump, play polo, cross country  and pirouette, you have invested a lot of time and money in a single asset....and now you want to park it close to the enemy!

Don't confuse static thrust with power. If you fit a big enough gearbox, you can use a jet engine to tow a barge, but slowly. Power = thrust x speed and is fixed for any engine. You also have a tip speed limit of Mach 1 on any fan, so beware of using the same fan for lift (large, slow) and thrust (small, fast)

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Technology / Re: What is the optimal battlefield attack aircraft?

« on: Yesterday at 01:42:28 »

Prone position in a custom-molded G-Couch should easily withstand 16G for short periods ,

But my question was whether you have tried flying prone for an hour. The RAF, USAF and Luftwaffe have built prone prototypes

A much modified Gloster Meteor F8 fighter, the "prone position/prone pilot" Meteor, was used to evaluate the effects of acceleration/inertia-induced forces while flying in a prone position. Along with the Reid and Sigrist R.S.4 "Bobsleigh", the Gloster Meteor was engaged in a proof-of-concept experimental programme that proved in practice that the difficulties of operating the controls of the aircraft outweighed the advantages of sustaining higher "g" effects.

Now available at a scrapyard near you.

After millions of years, we have evolved with a visual field of more than a hemisphere. Sitting up, this gives us a lot of useful information about the terrain, threats and targets below, ahead and above us. Lying prone, all we can see is the (necessarily friendly) terrain we have already passed over, which, to a pilot, is as useful as the fuel you left in the  bowser and yesterday's newspaper. Prone hang gliders are fun and even a novice civilian can pull the wings off without losing consciousness, but you still stand up for takeoff and landing, and in combat at 600 mph you need to see where you are going, not where you have been.

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Technology / Re: What is the optimal battlefield attack aircraft?

« on: 22/09/2018 15:51:41 »

  A fuel truck could be an enabler

The last thing you want on the front line. At best a hugely visible explosive  target, at worst an asset for the enemy to capture

...think of the plane as a Huey combined w/a tank .

Like a Chinook, perhaps? Very handy, but always based well behind the action. And I think there is a reason why tanks have tracks, not wings. Something to do with very big guns, hiding in terrain, and providing armour that moves at the same rate as the infantry.

Troops would beg t o have that nearby

I doubt it. The front line is for fighting, not for refuelling and repairing machines, or for feeding and defending the umpteen very expensive blokes (including offduty aircrew) who do that. If you want medevac, you want to go to a hospital away from the enemy, so that is where you keep fuel (and fast-refuelling kit) and ammunition.

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Radio Show & Podcast Feedback / Re: Feedback on "Are we ready for the next Chernobyl?"

« on: 22/09/2018 12:56:24 »

My hypothesis is that, as the background radiation there is mostly alpha, it may be comparable with the UK childhood leukemia clusters  reported in the 1980s which were uniquely associated with those sites handling bare plutonium

Spoiler alert; they weren't.

Sellafield, Dounreay and Burghfield were the prime "nuclear" hotspots, with another at Capper Pass (polonium emissions from lead smelting).  If you can identify others, I'd be very interested.

There was some misleading fog at Sellafield due to an apparent correlation between paternal gamma dose and childhood leukemia, which led to an indecently quick cash settlement between management and unions, but private chats with a union officer revealed that a more probable factor  was "dirty workers" - the guys in any organisation who always have accidents and ignore safety procedures - taking home hot particles. Metallic Pu is a reactive bone-seeker in biological systems but very difficult to detect against natural (unreactive) radon.

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Physiology & Medicine / Re: Could we bring back Neanderthals?

« on: 22/09/2018 11:06:48 »

Could we bring back Neanderthals? Yes, if you have a vote for any elected office in the USA.

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Technology / Re: What is the optimal battlefield attack aircraft?

« on: 22/09/2018 11:01:11 »

Try flying prone for more than an hour.

I have to believe that the boots on the ground would love having a super-plane hidden amongst them , right at the throat of the enemy .

Not if they have to build and defend a runway, hangar, ammunition store, fuel dump, workshop and canteen for the 10 technicians and 2 pilots needed to keep the aircraft working. The object of tank and infantry warfare is to advance as quickly as possible and occupy territory as thinly as necessary to control it, not to drag an air force around the planet. VTOL simplifies the requirement but 600 mph means that you can call up as much weaponry as you need from a properly equipped and self-defended base 10 miles behind the front line, and have it delivered in one minute.

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Technology / Re: Are we able to make sustainable implants?

« on: 22/09/2018 00:09:39 »

The problem with any implant is the fact that humans live a long time, change shape, adapt to exercise and diet, and repair themselves. Even passive implants have problems: bones weaken if they are not stressed, so several hip replacements have worked loose because they unloaded the femur, which gradually softened.

Longevity raises an interesting ethical problem Early cochlear implants used four electrodes and a fairly crude coding system compared with modern 16 or more electrode units. AFAIK no complex electronic device has ever been manufactured or stocked in its original form for 70 years (OK, you can still buy vacuum tubes designed in 1940, but they aren't used for digital signal processing). So if we implant a profoundly deaf small child (the procedure is much more effective if done before the age of 5) we have  recruited him to the hearing world and effectively excluded him from the deaf community, so he won't become proficient in signing and lipreading. But at some point we will be unable to support the implant: replacement is more complicated and risky than the initial surgery, and rehabilitation can be distressing or even fail completely because the new unit "sounds" nothing like the old one. So with the best of intentions, we are condemning our patient to an unpredictable and  major lifechanging event in mid-career, mid-family, peak expectation. If we could find some way of replicating the function with an external device we could instead smoothly upgrade the software and hardware and reprogram the brain incrementally as new versions arose.

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Physiology & Medicine / Re: Is blue light bad for our eyes?

« on: 21/09/2018 23:45:44 »

There are established safety levels for exposure to intense blue light. Early symptom of damage is temporary color blindness which may become permanent. We use spectrophotometry and a published "action spectrum" to design and test high-brightness workshops, operating theaters and cockpits - the noon sky above cloud is not always a safe workplace!

Blue light has some actinic effect on skin and is used to treat acne and neonatal jaundice, but most of the "science" put out by cosmetic companies is carefully worded bullshit.

UV-protective lenses will not absorb actinic blue light unless thay are visibly tinted.

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Technology / Re: What is the optimal battlefield attack aircraft?

« on: 21/09/2018 23:25:28 »

The Harrier did pretty well in this role but was difficult to fly compared with the more conventional A10. The use of two engines on the A10 was deliberate - you can recover with one dead. Leaning back improves the pilot's g-tolerance for dogfighting and air defence but you need to look down for ground attack. If you are going for net recovery, better to do away  with the human pilot altogether: some version of a loitering drone plus A-G  missiles is a lot more economical and can perform several functions (recon, intel, comms and attack) simultaneously by having several people "crewing" a machine no bigger than a single-seater, in ground-based comfort.

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General Science / Re: If I wear ANY battery watch, in by a weeks time, the battery is dead. Why?

« on: 21/09/2018 23:04:34 »

If  the  cellphone charge duration is normal, then the problem lies with your wrist environment. Sweaty wrists, or failure to remove a cheap watch before washing the dishes, bathing the dog, working on a trawler, or scrubbing up, can corrode the battery contacts. Judging from your extensive  career and life experience, I find it unlikely that your grandfather had many  battery-operated watches as they did not exist before 1960.

In a spirit of scientific enquiry, you could invest in a solar-recharged watch. Accurist  and Citizen make reasonably-priced "eco-drive" watches that are well sealed against the usual insults (mine regularly cycles up to 15,000 ft and I will admit to some sweaty moments) and never need to be opened - the one I am wearing now has run continuously for over 10 years. As a control, you could wear a self-winding mechanical watch on the other wrist, and see which one fails first.