That you get out of a shower wetter than when you get out of a bath.

That you’re never fully in contact with anything you touch.

That all of Earth’s systems/cycles are finely in perfect balance to allow life.

I have just started a degree course in Physics so I can study quantum mechanics – I find it fascinating as it’s so counter intuitive as we experience a Newtonian universe on a day to day basis.

@olddog, not sure where you are but this Friday

https://www.npl.co.uk/open-day

Quantum mechanics, classical physics and engineering, and people pissing about with LN2 too.

CountZeroO

h, and by the way; Bumblebees – magic can be the only explanation for how something so fat with such tiny little wings actually fly?

Lovely little creatures, always bring a smile to my face as they, well, just bumble past.😁 

They like a bit of football too.

It doesn’t make the boats any lighter.
Except, it does.  You’ve got things which are much denser/heavier than water (steel) and things which are much less dense/heavy than water (air).  Add them together and you’ll float or sink depending on whether you’re at a net gain or not.

These are concrete, so how do these work, then? 😝

I’m still amazed that superglue in a bottle doesn’t dry up

I’m not because I saw someone explaining how it sets.  A lot of things don’t set because they dry out, they undergo a chemical reaction which makes them solid – concrete, for example.  The cement dissolves in the water then a chemical reaction happens to make a solid.  If you let the water dry out before this reaction occurs it stays soft and crumbly.  Cyanoacrylate needs water molecules to cause a chain reaction that polymerises it – that’s why it sets so quickly and especially on your skin.  That’s why if you want to keep it fresh in the bottle or tube, squeeze all the air out – or get one of the squeezy sided bottles, as they do that.

Re boats, it’s the entire volume of the boat below the surface that is the same weight as the equivalent volume of water.  So it’s the metal AND the air inside it that counts.  If you push down on it, more of it is below the surface so it displaces more water than its volume – so when you let go it bobs back up to the point where the volume and weight are the same.

Think about it this way – when you put a boat in the sea, the sea level rises a little bit as your boat goes down – like a see-saw.

I find it fascinating as it’s so counter intuitive as we experience a Newtonian universe on a day to day basis

When I studied it there was no intuition involved. This is the equation, this is what it says about the relationship between those values.  Intuition is based on your lived experiences of the macroscopic world, the quantum world is something else entirely.  It’s nothing to do with what you consider ‘the world’ to be.

I know it’s probably quite a well known meme now, but this still blows my tiny mind a bit.

It deosn’t mttaer in waht oredr the ltteers in a wrod are, the olny iprmoetnt tihng is taht the frist and lsat ltteer be at the rghit pclae. The rset can be a toatl mses and you can sitll raed it wouthit porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe

Don’t think of it as the universe expanding, think of it as the amount of nothing getting smaller

I’m writing this down, it might come in handy someday!

still haven’t explained the induction hob.

Magnets.  When in doubt, it’s always magnets, aliens or DNS.

And I’m a bit smarter now than i was 15 mins ago……

No you’re not.  You’re more knowledgeable, your smartness hasn’t changed.

These are concrete, so how do these work, then?

But your photos suggest  that they don’t work.

Whose smart-arsed idea was it to build concrete boats?

Step-down transformers.

yeah, right.

On the boats thing, take a glass bowl and float it in a sink of water. Now melt it into a big marble and try and float in the sink again.

Seismic exploration – voodoo and etch-a-sketch mixed up. I used to tow several km of hydrophones* and the echoes were fainter than the noise of the waves. Add them all together and out pops some squiggles. Geologist gets the colouring pencils out and next thing half a billion dollars of oil rig has a gyser of black gold shooting out the top. And it was less than £1 a litre when I learnt to drive!

*Don’t get me started on piezoelectricity

Resin 3D printers.

Boy1 has one. He models anitem in CAD software, transfers it to a machine that uses UV absorbing resin, fires UV light at it and a small 3D copy of the thing he created on his computer pops out.

I kind of understand it’s all about UV light, exposure time and intensity, movement and speed of the build plate. But it’s still witchcraft.

Time? Why does it fly when you’re having fun?

Vinyl records.

No idea how a series of bumps in some plastic can recreate the sound of a full philharmonic orchestra

the acceleration of a piston from top dead center…….is accelerating at 15,000 ms^-2,

The acceleration is the easy bit, it’s making sure they decelerate at TDC that’s important 😉 Have watched a 4.2 litre V8 fail to decelerate a number of pistons… at 8000 rpm/full load.

And FWIW, the forces are high enough that the flex/clearances in the conrod/gudgeon pin/crank/block/frame of the engine are large enough to make a measurable difference in the peak loads. Even though the flex/clearances are minuscule.

That’s the simplest sound reproduction method available. That sound of the orchestra – that IS just a series of vibrations, so that’s what’s on the record.

That you get out of a shower wetter than when you get out of a bath.

Ooooooooooooh, i know this one!

The surface tension of the water in the bath is stronger than the adhesion of the water to your body.

So the bath sucks the liquid off. Don’t get that effect in a shower.

(May not apply to those of us who are very hairy.)

And Rolls Royce Aerospace used to send their apprentices on a sailing trip as part of their training.

On a concrete sailing boat.

That sound of the orchestra – that IS just a series of vibrations, so that’s what’s on the record.

Yes I get that. But you could grab any fraction of a second of the recording and have dozens and dozens of instruments playing (on any record not just an orchestra) and a tiny series of bumps allows you to differentiate between the cellos, the violins, the tubs, the french horns, the cymbals,

Hair growth.

If you shave your head hair, it will grow then carry on growing and get longer and longer and longer.

If you shave your hair from anywhere else on the body it will grow to a fixed length then stop. No-one has 30cm long pubes (not even Hairy Helen from Stevenage who I was introduced to as a teenager)

How does body hair know when to stop growing?

How does body hair know when to stop growing?

My eyebrows beg to differ.

My eyebrows beg to differ.

As does my nose hair

But you could grab any fraction of a second of the recording and have dozens and dozens of instruments playing (on any record not just an orchestra) and a tiny series of bumps allows you to differentiate between the cellos, the violins, the tubs, the french horns, the cymbals,

All those sounds add together into a single wave.  The clever bit is that your brain can recognise them all separately out of that single wave.

How does body hair know when to stop growing?

These are all the kinds of questions I’ve thought about and/or looked up since I was a child so I have plenty of answers (accuracy not guaranteed).  Body hairs grow at a certain rate, and each follicle grows for a certain amount of time before ejecting its hair and starting again.  That alone will result in a fixed length, but what also happens (especially for body hair) is that it rubs on your clothes and furniture etc so it gradually gets eroded. If you have a close look at an arm hair it tapers to the end – so the length is determined by the wear it gets, its toughness, how fast it grows and how long the follicle goes on for.  With long head hair the ends fray, split and break up as well, which is why if you want to grow longer hair you need to trim these bits off or somehow stick the ends back together.  They grow until they fall out and start again.

That you get out of a shower wetter than when you get out of a bath.

I think this is because at least 1/3 of your body is not in the water when you take a bath.

Bluetooth.

Tides.

Anything about the earths crust, rock formation, volcanism etc.

the forces are high enough that the flex/clearances in the conrod/gudgeon pin/crank/block/frame of the engine are large enough to make a measurable difference in the peak loads. Even though the flex/clearances are minuscule.

And yet metal-metal contact in the rods and crank are prevented by just pumping some oil between them.

I think this is because at least 1/3 of your body is not in the water when you take a bath.

What sort of weird-ass baths are you taking?

take a glass bowl and float it in a sink of water. Now melt it into a big marble and try and float in the sink again.

Now drop it in a bowl of mercury.

Relative density can be counter-intuitive.  If you have a loose helium balloon in a car and accelerate sharply, it will fly forwards.

Mercury – that it is a liquid at room temperature.  Watching a lump of mercury melt looks like magic.

The internet.

Try and explain what it is now that it exists. Difficult isn’t it?

Now pretend you are Tim Berners-Lee trying to explain what you have invented 30 years ago…….

And yet metal-metal contact in the rods and crank are prevented by just pumping some oil between them.

Yup, that’s a whole new pile of complicated maths and “science”. (Tribology, that i nearly did a degree in…)

Standard ones where my knees stick out and my torso from about sternum upwards – and my head obviously.  I once rented a flat with a huge wide bath and one time I plugged the overflow and filled it right to the brim.  My legs and arms floated, it was actually quite weird. How I didn’t go through the floor Money Pit style I don’t know because it was upstairs in a shonky old house.

The internet.

Try and explain what it is now that it exists. Difficult isn’t it?

Not at all. It’s a network of computers connected across different geographical locations via IP routing.

Now pretend you are Tim Berners-Lee trying to explain what you have invented 30 years ago

As above, it’s easy, but he didn’t invent the internet he invented the world wide web, which is (or was when he invented it) a specific protocol and a markup language that embodies the concept of hyper linking.  Pretty straightforward.

Next question.

Everything is mostly made of empty space.

@gecko76
Mirrors. A room with a mirror in it is fractionally colder than it would be without one. Measure it if you don’t believe me.

What else do they steal, apart from heat?

Your soul……..

I want to know what happens to the other me in the mirror when I’m not there – where does he go?, what does he do?

If you have a loose helium balloon in a car and accelerate sharply, it will fly forwards.

How do you know that?

How do you know that?

Errrr, personally speaking i’ve actually tried it…

And under braking (that was more noticeable in my 60bhp shitbox).

its not that the balloon with fly forwards, but all the more dense air in the car will “slosh” backwards, displacing it.

how your smart watch “sees” your pulse.

And anything Tom Stanton has created. his swashless helicopter is fantastic.

Another one for me, the fact that you can see through some materials and not others.

Errrr, personally speaking i’ve actually tried it…

Now there’s dedication to expanding your scientific knowledge!