1

Chemistry / Re: what is this molecule please?

« on: Today at 18:49:56 »

Well, most of it is tetracycline.
https://en.wikipedia.org/wiki/Tetracycline
But there's a strange oxime derivative bit at the bottom left.

2

Physics, Astronomy & Cosmology / Re: What causes nuclear power plant meltdowns?

« on: 04/04/2021 11:55:04 »

Chernobyl surely should have had an off button

All power reactors have an "off" button, which stops the nuclear chain reaction.

However, the residual heat continues to produce around 6-7% of the reactor's output power, even after the fuel rods are fully inserted. This drops below 1% after a day or so.

Chernobyl off button was what killed it, the quick insertion of  the control rods blew it up, because they had a moderator at the end. Steam pockets ensued and not a good outcome!

If I (being very careful of the language I use, nuclear reactors and explosions I'm sure flag up at gchq) rendered a reactor incapable of being controlled by consoles, could I cut a rope to drop the control rods? If one control rod jammed could I drop the rest? Would the reactor have passive cooling capability? A clever design in  pipework(s) to a radiator(s) radiator on the roof(s) would be good. Nuclear reactors seem not to have the aarospace standard of duplicates and triplicate.

They had triplicate systems.
They failed to take account of "common mode failure".

All three cooling systems were washed out at once by a single common cause.
It would also have washed the radiators off the roof..

So a quadruplicate system may not have worked any better.

3

Physics, Astronomy & Cosmology / Re: What causes nuclear power plant meltdowns?

« on: 04/04/2021 11:52:03 »

"Fission" involves the artificial and unnatural splitting of atoms of heavy elements such as Uranium. 

Why do you think it is unnatural?
https://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor

4

Physics, Astronomy & Cosmology / Re: What causes nuclear power plant meltdowns?

« on: 02/04/2021 13:00:58 »

The exercise was executed as planned, so this was not a matter of "pilot error" but must be seen as deliberate sabotage.

No.
Because sabotage has some sort of point to it- financial, political whatever.
They just screwed up. But there is a reason for that.

The German military command told their troops that Enigma was uncrackable. The troops believed them and got "sloppy"- which is how Enigma was cracked.

The Designers said the Titanic was unsinkable, so the captain didn't prioritise the lookouts.
So nobody saw the iceberg until it was too late.

The managers of the space shuttle project thought that the risk of failure was "One in a million"- and they still thought that after the first failure...


The guys running Chernobyl had been told "RBMK reactors are relatively simple and generally problem-free ". or as they put it "safe as a samovar".

We know what happened next...

5

Technology / Re: Microwave side door gap, is it safe?

« on: 01/04/2021 21:55:47 »

So far, I haven't seen any convincing answers.

It is not the answers' fault that you are not convinced.

6

Question of the Week / Re: QotW - 21.03.29 - Why does chilli stay on your hands so long after cooking?

« on: 01/04/2021 20:20:05 »

Beans were farty long before Blazing saddles was filmed.
https://en.wikipedia.org/wiki/Pythagoreanism#Vegetarianism

These days, we even know why they are windy.
https://en.wikipedia.org/wiki/Baked_beans#Flatulence

7

Physics, Astronomy & Cosmology / Re: What causes nuclear power plant meltdowns?

« on: 01/04/2021 10:29:14 »

"What usually causes nucular power plant meltdowns?"
Nothing.
That's why they don't "usually" happen.
They are actually very rare.
Wiki records just 3 major ones and another score of minor ones.
Since 8 of those were in Russian subs, you can draw your own conclusion about "what causes meltdowns".

https://en.wikipedia.org/wiki/Nuclear_and_radiation_accidents_and_incidents#Nuclear_meltdown

8

The Environment / Re: What would happen if all of humanity vanishes in one second?

« on: 29/03/2021 19:50:15 »

With conservation of matter, everything we have ever dug up out of the earth still exists somewhere in one form or another. 

But with the exception of gold- which we dig up in many places, but then bury again at the national banks, we dig up concentrated deposits of minerals, and then distribute them all over the place.

It's going to be a challenge to find shallow coal for a long time.

9

The Environment / Re: What would happen if all of humanity vanishes in one second?

« on: 29/03/2021 19:41:27 »

A lot of cars would crash quite quickly. The planes that were in the air at the time would take rather longer to fall out of the sky.
Some ships might sail on for days or weeks before they hit something, or ran out of fuel.

10

New Theories / Re: Any theories in physics you don't agree with?

« on: 29/03/2021 11:14:23 »

A theory can still be shown to be false

At that point, it stops being a scientific theory.

11

Chemistry / Re: How to work out the paraffin retention properties of microscope slides?

« on: 27/03/2021 12:53:45 »

You could "glue" two slides together with the wax and see how easy it is to pull them apart.

12

Physics, Astronomy & Cosmology / Re: Centre of the universe?

« on: 26/03/2021 23:08:52 »

I mean, if the Universe really did originate from a single point, why shouldn't we able to find where that point was?

Which kind of makes this little planet of ours the very centre of the observable universe doesn't it?
Thoughts?

Yes, but everywhere is the centre of the universe.

Imagine drawing dots on a balloon, and then inflating it.
All the dots move away from each other so all of them "see" themselves as the centre.

Now imagine it starting from  a very small balloon.

It's not an explosion "in space" but an expansion "of space".

13

Physics, Astronomy & Cosmology / Re: Centre of the universe?

« on: 23/03/2021 18:27:05 »

Which kind of makes this little planet of ours the very centre of the observable universe doesn't it?
Thoughts?

Yes, but everywhere is the centre of the universe.

Imagine drawing dots on a balloon, and then inflating it.
All the dots move away from each other so all of them "see" themselves as the centre.

14

New Theories / Re: Water and Life

« on: 23/03/2021 11:12:19 »

Are You complaining that the Artists are drawing a Dolphin but not the Sea that it lives in?

That seems to sum up the problem nicely.

15

General Science / Re: Does pressure in a thermos flask affect the temperature of the water inside?

« on: 23/03/2021 08:41:20 »

n is number of moles

Where?

It's an interesting fact that (assuming ideal gas laws) heating a rom doesn't increase the energy in the air in the room.
The increase (per mole) is exactly compensated by the expansion forcing some air out of the room.

Due to ono ideal behaviour the gas in the thermos will cool slightly.
But the big (in energy terms) effect is likely to be the evaporation of from the drink to make up for that lost .
Whether that's the dominant effect in terms ot temperature might depend on how much liquid is present etc.

Nope, gas cylinders are the same temperature no matter what the pressure,

Except on a hot day (or a cold one).

I think you were aiming for this, and missing.
https://en.wikipedia.org/wiki/Joule%E2%80%93Thomson_effect
An ideal gas won't cool as it expands, but a real gas will.
Water vapour is a real gas.

16

Physiology & Medicine / Re: Could this save millions of people from premature death and help w/ weight loss

« on: 22/03/2021 11:13:32 »

Yes, I know, but it doesn't work well with all types of solid foods, like fries, for instance. They get stuck in the pipe/tube.

I don't know about you, but given the choice between minor surgery and learning to chew my food properly, I know which I would go for.

The point remains, without the pipe to remove some of the food you eat, that food will be digested and absorbed and, in essence, make you fat.

17

Physiology & Medicine / Re: Can measles erase the body's antibody memory?

« on: 21/03/2021 10:59:04 »

(and I find it unlikely that measles would erase other antibody responses)

I also thought it unlikely but...

https://science.sciencemag.org/content/366/6465/599

18

Just Chat! / Re: What physical sports are gender equal?

« on: 19/03/2021 08:44:50 »

But British troops are not so well renowned in the attack role

The implication of this is that we sat here and built the biggest empire in the world.
That's an "interesting" idea.

19

That CAN'T be true! / Re: Can this microwave boiler heat your home?

« on: 18/03/2021 19:30:09 »

Don't forget "As used in NASA's space program." which also applies to damned near anything.
And it probably "Works with android or iPhone".

20

That CAN'T be true! / Re: Can this microwave boiler heat your home?

« on: 17/03/2021 18:51:48 »

Just a thought.
If I put a resistor in a tank of water, I could make the case that, at least some of, the heat transfer would be via microwaves being emitted from the resistor and (without having to travel very far) being absorbed by the water.

In which case, I could sell an ordinary immersion heater as "works via microwaves".
Presumably I could then stick an extra zero or two on the price tag and still undercut the supplier in the OP.

(even if I bought my immersion heaters from RS.)
https://uk.rs-online.com/web/p/heating-elements/0273034/?cm_mmc=UK-PLA-DS3A-_-google-_-PLA_UK_EN_Automation_%26_Control_Gear_Whoop-_-Water%20Heater%20Elements_Whoop-_-273034&gclid=Cj0KCQjw0caCBhCIARIsAGAfuMxPY265L9n3KJHLhI7EbvUXRwBbWEMy0mfvarWiGM-b4qXHJ8bQ02MaAg6TEALw_wcB&gclsrc=aw.ds&matchtype=&pla-296206105570