1

New Theories / Re: Can we draw a geometrical representation of gravity?

« on: Yesterday at 15:37:34 »

Can we draw a geometrical representation of gravity?
Yes.
↓

2

General Science / Re: How much of me is original?

« on: 30/06/2022 18:30:24 »

(not teeth - they all fell out and were replaced when you were a child!)

The replacements may have already been in place, but it's probably beside the point.

I'm not saying this is an accurate mechanism to answer the question but it does give some indication.
In a typical year you can expect to eat something like 1000 Kg of food. That's about 7 times your weight.
The stuff food is made from isn't very different from the stuff you are made from.
So each year your body takes in 7 times its mass in "stuff".

If that were properly mixed then only 1/7 of you would be still there at the end of the first year.
So it's 1 in 49 after 2 years and by the time you are 65 it's pretty close to bugger all.

Obviously some bits are better mixed than others.
The chip in my front tooth that I have been carrying round since school is still there- more like 45 years than 65, but the point remains.
Most of that stuff is pretty much fixed. Skeletal bone is turned over much faster than that, but still pretty slowly.
My skeleton is something like 10Kg
It contains something like 1400 grams of Calcium
"The calcium content of bone at maturity is approximately 1,200 g in women and 1,400 g in men"
from
https://www.ncbi.nlm.nih.gov/books/NBK56060/
and it turns over about 0.5 grams per day
https://www.medscape.com/answers/241893-20078/how-much-calcium-turnover-occurs-normally-each-day
so that's about 180 grams per year or (very roughly) the whole lot gets rebuilt every 7 or 8 years.
Some bits deep in the middle might date back to when I was a teenager.
At best, very little of it will be original.
"At full-term birth, the human infant has accrued about 26 to 30 g of calcium, most of which is in the skeleton."

Just a thought; if we are what we eat, why are we not "new and improved"?

3

New Theories / Re: Molecular chain that would end all life? Causality Firewall of life/ CFL?

« on: 30/06/2022 13:43:51 »

If the hydrogen bond between water molecules suddenly disappeared all life (as we know it) would die.
Also the oceans here would boil.
But, on a scale bigger than planets, the weird properties of water probably don't matter much.

This has nothing to do with causality or firewalls.
It's a fantasy.

4

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

« on: 28/06/2022 18:32:05 »

What Question Could You Ask To Determine Sentience Of A Human?

5

New Theories / Re: Can conscious thought act on matter?

« on: 28/06/2022 09:35:50 »

" Can conscious thought act on matter?"
If it didn't, we wouldn't know it existed (other than our own).

6

Physiology & Medicine / Re: The crucial ingredients of CBD:

« on: 21/06/2022 17:36:21 »

I'm just waiting for the spam advertising.

7

Physics, Astronomy & Cosmology / Re: Is there a net heat exchange between water and ice at 0 degree C?

« on: 16/06/2022 21:06:14 »

I'm going to say no, not reliably or meaningfully.

Others may differ
http://users.mrl.illinois.edu/cahill/intel08.pdf

But if you asked about a nanometre cubed, it would be tricky.

8

Technology / Re: What Is The Benefit Of Cryogenically Treating Cables ?

« on: 16/06/2022 13:53:48 »

You have to get copper down to 35K before it becomes superconducting

I'm fairly sure that copper doesn't superconduct  even at much lower temperatures than that.

9

That CAN'T be true! / Re: hydrinos!

« on: 10/06/2022 21:39:07 »

Randall mills claims he can lower the ground state 1s electron of a hydrogen atom to a lower level producing energy in the process

Maybe.
But he hasn't shown anyone else that he can do it, not has he shown anyone else how to do it.
So his claim looks a lot like saying there are fairies at the bottom of the garden.

10

Physics, Astronomy & Cosmology / Re: Is there a net heat exchange between water and ice at 0 degree C?

« on: 08/06/2022 21:39:20 »

It's not how well tested the laws of thermodynamics are that matters here.
Again, it's Galileo dropping things off a tower.
He did not need to do the experiment.
He knew that the light thing and the heavy thing had to fall at the same speed- because he had considered what would happen if you tied a heavy ball to a light ball and dropped both.
The combined "thing" consisting of the two balls would obviously weigh more than the constituents.
So, if Aristotle had been right, the combination would fall faster than the heavy ball.
And the light ball would fall more slowly.
But how could the combined thing fall faster then the heavy ball when the light ball was trying to fall slower?

It's impossible.
Galileo knew that.

He only did the experiment for the benefit of the local dignitaries who were not clever enough to understand the logic.

Now we are looking at the laws of thermodynamics, rather than falling objects.
But, like Galileo, we have the advantage of a deep understanding.
We have known for a hundred years or so that momentum, angular momentum and energy are conserved.
We don't rely on experiments to know this.
We have a mathematical proof.
https://en.wikipedia.org/wiki/Noether%27s_theorem

And yet, we still have hamdani yusuf saying that, because he can't do a proper experiment, he doesn't believe it.
He refuses to learn, or even accept the science.

You can lead a horse to water, but you can't make it drink.

He is even less well informed that those local busybodies for whom Galilei had to climb the tower and drop stuff.

11

Chemistry / Re: Why is Armstrong's mixture so sensitive?

« on: 07/06/2022 18:46:34 »

I read that part of the reason why mixtures of  sulphur and chlorates are so unstable is something like this:
 the sulphur is attacked, even at room temperature, by oxygen.
That produces sulphur dioxide and that, together with water in the air is acidic.
That acid reacts with the chlorate releasing oxides of chlorine.
Those react with the sulphur to produce more acid(s).

The reaction is "autocatalytic".
The heat generated also speeds up all of the reactions.

I suspect something similar happens with phosphorus.

12

Plant Sciences, Zoology & Evolution / Re: Do Spiders Cooperate ?

« on: 28/05/2022 17:23:27 »

Do Spiders Cooperate ?
They mate.

13

General Science / Re: Are Black Holes The Blackest Things Ever ?

« on: 27/05/2022 15:55:29 »

They're not perfectly black, but they're blacker than a place in space with no stars in it.

The black sheep don't quite win, but close.

Why is the one in the middle winking at us?

14

Chemistry / Re: How can I find the optimum ΔH and ΔS for passive T control?

« on: 27/05/2022 09:00:21 »

While it's true that ΔS  ≈  ΔH / 300 is pretty much the criterion for optimal regulation at 300K, it is just restating the requirement that the melting point is near 300.

And tables of melting points are easier to find than tables of ΔS

It's also worth thinking about the "units".
As Alan didn't notice,  ΔH is typically given per mole or per unit mass.
On a practical basis you might want to look at the value per cubic metre.
And then you need to look at   ΔH per £.

 

15

Chemistry / Re: What colour is paint before the colour is added?

« on: 18/05/2022 18:32:01 »

It seems unlikely that the OP is going to return to a decade-old post.
Just in case they do- until you add the pigment, you don't have paint. So the question makes no sense.

16

Chemistry / Re: How well understood is the Chemistry of the trans-uranic elements?

« on: 17/05/2022 21:38:22 »

For a given definition of "industrial", Californium  (98) also has uses- as a neutron source.
Perhaps  more relevantly, the colours of some of its compounds have been observed.

17

Chemistry / Re: How well understood is the Chemistry of the trans-uranic elements?

« on: 16/05/2022 21:29:28 »

adding a handful of singly (or doubly) positively charged ligands at a radius of 150 picometers

How would you get them to stay (either near to your centre atom or even to each other)?

Essentially, in order to change the rate of a nuclear reaction you have to change the energies involved by an amount comparable with the decay energy.
And the problem is that chemical energies- like ligands are about a million times smaller than typical nuclear energies.

18

Chemistry / Re: Another light scattering question; colour of an alien sky?

« on: 16/05/2022 10:21:44 »

Blue- unless it's cloudy.

19

New Theories / Re: what is temperature?

« on: 09/05/2022 13:00:33 »

Why don't polyatomic gases rotate nor vibrate at low temperature?

Because the energy available to them is less than that required to get them  to rotate or vibrate.

Is vibrational energy also quantized?

Yes.

QM is not important. 

Yes it is.

What's the minimum non-zero quantity of of rotational energy?

It depends on the molecule.
For N2 I think it's about 10^-4 eV.

20

Technology / Re: Are electric cars responsible for natural gas demand?

« on: 30/04/2022 12:29:39 »

I'm all for the electrification of transport. Underground railways and trolleybuses are great, and electric cars are terrific fun to drive.But we don't have (and can't have) enough electricity from non-fossil sources to abandon gasoline, diesel, and gas-generated electricity to meet current and predicted demand. 

And when the oil runs out, we won't have gasoline and diesel.
So we had better start planning to decarbonise the economy now, while we still can.