1

General Science / Re: Bitcoin

« on: Yesterday at 08:05:46 »

Bitcoin uses the SHA-256 hash algorithm to map ("Hash") from the user's private key to the public identifier on the blockchain.
- If you lose the private key, you have to guess a 256-bit number, which will take about 10⁷⁷ hashes, far beyond the capability of today's computers.
- But if you could do that, you could steal anyone's Bitcoins.
- Wikipedia gives a few examples of people losing their private key.
https://en.wikipedia.org/wiki/Bitcoin#Addresses_and_transactions

The world workforce of Bitcoin miners is currently increasing the rate of hashes, at an exponential rate. Back in 2017, they were doing 10¹⁹ hashes per second. Now it looks like 10²¹, see graph here:
https://www.blockchain.com/explorer/charts/hash-rate

2

Physics, Astronomy & Cosmology / Re: What Is The Final Parsec Problem ?

« on: 19/01/2025 10:55:18 »

Unfortunately, the length of current gravitational wave detectors does not allow us to detect the very low frequencies/long wavelengths of merging supermassive black holes. So we can't directly measure the rate of such events*.

There is an indirect indication that such mergers might occur, in the form of "X-shaped" radio galaxies; one theory suggests that a supermassive black hole was emitting a jet of matter from the poles of the accretion disk - and then it suddenly gets hit by another massive impactor, which changes the axis of rotation, and the direction of the polar jet.

In the images I have seen of these objects, there does not seem to be a large gap in the polar jets, suggesting no final parsec pause.
https://en.wikipedia.org/wiki/X-shaped_radio_galaxy

PS: This next paper suggests that the X-shaped radio galaxies might occur due to interactions between the jet and the accretion disk, which does not turn off the jet:
https://www.space.com/black-hole-feeding-x-shaped-galaxies

*Perhaps the proposed LISA space-based gravitational wave observatory will give a better idea of how common these are
https://en.wikipedia.org/wiki/Laser_Interferometer_Space_Antenna

3

Technology / Re: Does cold weather damage the batteries used in an EV?

« on: 13/01/2025 05:21:15 »

I ran across this comment from Blair Korchinski on Qora, comparing petrol and electric cars in the Canadian cold... (he obviously likes EVs)
https://www.quora.com/If-electric-cars-are-not-good-in-extreme-cold-then-why-do-people-keep-buying-Teslas-in-Canada


Q: If electric cars are not good in extreme cold, then why do people keep buying Teslas in Canada?
A: As the owner of two gasoline-powered pick-ups and the driver of a diesel at work, questions like this always make me laugh.
In the cold an EV (Electric Vehicle) loses 40% of its capacity. In the best conditions, the very best ICE vehicle reaches 40% efficiency [loses 60%].
When it?s cold here in Canada we plug in our ICE vehicles so they will start. Double block heaters, like in my 2004 Chevrolet Silverado, suck about as much electricity as the average commute uses in an EV.
Gas mileage goes way down in the winter in ICE vehicles. Most of us warm up our cars for 10?15 minutes twice a day. The engines don?t run as efficiently, so even warmed up fuel mileage suffers. Then there are problems with fuel lines freezing, cars not starting. Then there?s extra wear and tear caused by thick oil not lubricating properly until the oil warms up. Catalytic converters don?t get hot enough to do their jobs, so we pollute even more.
Diesels, well diesels suck in the cold. The fuel doesn?t atomize properly, the batteries get so weak they won?t run the glow plugs or engine heater, and in the bad cold, the fuel gels up. DEF (Diesel Exhaust Fluid) tanks freeze solid and the little heater in there can?t keep up, so you get emissions alarms. The heaters don?t put out enough heat, you have to leave them idling for extended periods. Stop for fuel and the damned pumps freeze up so it takes forever to fill the tanks.
Go to an area where there are lots of diesels when it?s -30 ?C and you can smell the half-burnt diesel in the air. That?s how inefficient they become in the cold.
All of that is just an average winter day for guys like me. We?re so used to it, we barely think about it as we stand out there in the cold with our booster cables.
So the question shouldn?t be why we buy EVs, but why we don?t buy more of them. The modern technology makes way more sense here than ICE vehicles do.

4

General Science / Re: Can Human Consciousness Be Uploaded?

« on: 06/01/2025 08:43:26 »

It must ... be working now in order for a copy of it (to work)

Our conscious minds are able to reboot after anesthetic.
- That includes some subconscious functions like breathing, which are suppressed during heavy sedation

Is it possible that our brains could reboot after being copied?

5

Physics, Astronomy & Cosmology / Re: Am I safer on Mars?

« on: 06/01/2025 08:37:48 »

At present, there are estimates about the quantity of meteors hitting the Earth's atmosphere, but only a small fraction of them (larger than 1 kg) actually survive to hit the ground.
- Smaller ones are more frequent than more massive ones, but we don't have good statistics on them

The LUMIO space probe (planned launch in 2027 or 2028) will study meteorite impacts on the far side of the Moon (but only while it is also the dark side of the Moon).
- It will look for flashes as meteorites strike the Moon, vaporising the lunar rock
- They expect to detect meteorites as small as 1 gram
- This will give a better idea of the size distribution of meteorites - even a 1g meteorite could destroy an above-ground lunar habitat.

https://www.sciencedirect.com/science/article/pii/S0094576522001424

6

Geology, Palaeontology & Archaeology / Re: Why does Earth have tectonic plates?

« on: 04/01/2025 10:04:52 »

To add to the comment by Diverjohn...
During the expected glancing blow between Thea and Earth, it was mostly lighter crustal material that was thrown out to make the Moon.
- This meant that the floating crustal material no longer covered the whole Earth in a solid thick skin
- So the remaining crustal material was thin enough to be pushed around by convection currents in the mantle beneath, forming continents where convection cells converged, and splitting them apart where convection cells diverged.

Perhaps the lack of a large, low-density moon may explain why neither Mars nor Venus have plate tectonics?

https://en.wikipedia.org/wiki/Origin_of_the_Moon

7

Physics, Astronomy & Cosmology / Re: What are the physics of brakes?

« on: 04/01/2025 09:48:13 »

Regenerative braking is another form of dynamic brakes, used by say electric locomotives and cars

During braking, my hybrid car puts the car's kinetic energy into the battery (with some losses).
- As Halc noted, this can't bring you to a complete stop - but it works down to quite low speeds
- When you know that you will have to stop (eg because the traffic lights are red), you can take your foot off the accelerator, and "coast" (slowed by air resistance, any uphill slope and gentle regenerative braking), until it is time to pick up the speed again.*
- Fuel efficiency is "gamified" in my car: The car has a little report card at the end of every trip - hard acceleration and hard braking yield a lower score.

This raises a question I had for Chris:
- In one podcast it was mentioned that full-electric cars would cause more wear on brake pads (and particulate pollution) because the battery made the car heavier.
- However, regenerative braking means that the mechanical brakes should be used only rarely, and this should produce less particulate pollution?
- The tyres would still produce particulate pollution for both electric and petrol cars (more for a heavier car)...

*Note that coasting in an electric vehicle is not the same as putting a petrol car into Neutral and coasting; in the electric car, the engine is still engaged with the wheels.

8

Plant Sciences, Zoology & Evolution / Re: Could we eat wood?

« on: 04/01/2025 09:24:35 »

termites have bacteria in their guts that digest the normally indigestible cellulose

Many herbivores have microbes in their guts which digest cellulose.
- But the cellulose must first be crushed very thoroughly to give the microbes free access to the cellulose, which is why cows and sheep spend so much of the day chewing

The cellulose breakdown process is very slow, which is why herbivores have physically large guts, and long transit time
- The energy extracted is relatively low
- Humans have small relatively guts and medium transit time, which is possible because the food is "pre-digested" by external processes like grinding, fermenting and cooking.
- And cooked meat (protein+fat) forms a portion of the diet for many humans.
- So the conditions in our guts are probably not ideal to host cellulose-digesting bacteria
- And the anaerobic conditions in out guts are not suitable for nitrogen fixation.

Maybe we could genetically engineer bacteria that can quickly digest cellulose, and are at home in the human gut?
- But humans prefer to do things externally - in the environment or in domesticated animals
- It means we carry around less "baggage".

9

Plant Sciences, Zoology & Evolution / Re: Could we eat wood?

« on: 04/01/2025 09:11:26 »

a  fungus which fixed nitrogen and produced protein

I see mixed responses on whether this is true.
- In digesting wood, fungi free the protein that was originally in the wood. They incorportae the released protein into the growing fungi.
- Some discussions say that fungi themselves can't fix atmospheric nitrogen - this is only done by prokaryotes
- Some fungi have a symbiotic relationship with bacteria that can fix atmospheric nitrogen.

This paper tested a theory that a particular fungus could fix atmospheric nitrogen by itself - they found that fungus growth was best when the symbiotic bacteria were present; they conclude it is the bacteria which fix nitrogen.
https://pubmed.ncbi.nlm.nih.gov/15381850/

10

Just Chat! / Re: What is the best way to crash land a plane?

« on: 29/12/2024 21:15:48 »

Avoidance - don't fly into a flock of ducks.

11

General Science / Re: What would the kinetic energy of a bullet falling from 2Km be?

« on: 26/12/2024 21:35:14 »

Another quote related to firing bullets into the air, from a satirical song by Tom Lehrer about Werner Von Braun...

Don't say that he's hypocritical,
Say rather that he's apolitical.
"Once the rockets are up, who cares where they come down?
That's not my department, " says Werner von Braun.

https://tomlehrersongs.com/wp-content/uploads/2018/12/wernher-von-braun.pdf

12

General Science / Re: What would the kinetic energy of a bullet falling from 2Km be?

« on: 26/12/2024 05:32:40 »

What would the kinetic energy of a bullet falling from 2Km be?

I know someone who grew up in Iraq; on hot nights they often slept on the roof.
- Her sister woke up one night and found a bad bruise on her leg.
- It didn't improve over the next few days, so they took her to the doctor, and he discovered a bullet embedded in her leg.

I shot an arrow into the air, it fell to Earth I knew not where.

I ran out of regular 60/40 solder and I needed to order a fresh supply..."ONLY FOR PROFESSIONAL USERS"

For many years in my industry, tenders for electronic products always required "RoHS compliance": EU Restriction of Hazardous Substances
- This bans a number of substances in electronic equipment, including lead.
- So your 60/40 lead/tin solder is now 40% illegal in the EU.
https://en.wikipedia.org/wiki/RoHS#Details

Other solder alternatives include alloys of Tin, Gold & Copper, but they have a higher melting point, and perhaps more toxic flux, so avoid breathing the fumes.
https://en.wikipedia.org/wiki/Solder#Lead-free

13

General Science / Re: How does ChatGPT work?

« on: 26/12/2024 05:09:10 »

some of the learning was human supervised

I (mostly) retired recently; since then I have seen several job offers to help with human supervision of AI training.
- There is apparently some training of the humans involved before supervising the AI
- Given my background, one of the offers specifically mentioned reviewing and improving results in mathematics
- I haven't investigated any of these job offers, so I don't know any details (and probably could not reveal anything if I did take one up!)

It is incapable of learning

"Conversational" AI can consider additional input from users during a conversation, but ignores previous input when you start a new conversation.
- Inputs from users don't affect the structure of the current AI, but can be used to train the next version of the AI
- I imagine that scanning through conversation logs for users saying "that's wrong" or the AI saying "I'm sorry" would be a good guide for areas to include in the training data for the next version.

Why do They not provide IT with Sensors?

Self-driving cars are AI systems with multiple sensors.
- The relatively simple "driver assist" function on my car (3 years old) takes input from a camera in the windscreen and radar on the front grille, and uses it to nudge the throttle and steering.

14

General Science / Re: Can Human Consciousness Be Uploaded?

« on: 26/12/2024 04:36:44 »

If you define consciousness as "the pattern of activity in a person's brain"...

...then uploading it would imply copying the function of all the biological circuits in that person's brain
- That means copying the connectivity of neurons and synapses and weights which control the activity of that brain
- Current technology was in 2023 able to map the 135,000 neurons and 50 million synapses in a fly brain
- which took several years of work by researchers
- This study identified 4500 cell types in the brain, of which 1500 were new to science (and so their function has not yet been studied)
- In my simple understanding, this study could identify physical synapse connections (the connectome), but could not identify whether individual synapses were excitory or inhibitory, or how strong the weights are: could you call that the "logical" connections?
- So great progress has been made on analysing a fly brain, but a computer is not yet capable of "executing" the program built into a fly brain, which requires the weights
https://en.wikipedia.org/wiki/Drosophila_connectome

The human brain has around 100 billion neurons and 100 trillion synapses (plus weights) which control the activity of that brain
- So it is an advanced research project to map even a cubic millimeter of a human brain (which would not be very useful, since many of the connections would be with areas outside that cubic millimeter).
 
Even if the brain "program" could be executed on a computer, it still needs to have inputs from real or simulated eyes, ears, small, taste and touch and control outputs like muscles and glands to produce the same reactions as a real human
- Otherwise we will have recreated someone with "completely locked-in" syndrome: conscious, able to think, but in total isolation would quickly go mad.
https://en.wikipedia.org/wiki/Locked-in_syndrome

15

Question of the Week / Re: QotW - 25.01.06 - During the time of Pangea, what was on Earth's other side?

« on: 15/12/2024 04:28:40 »

This article suggests that a concentration of land meant relatively little sea coast in tropical waters, which restricted coral reef growth in this period.
- Ocean currents and Monsoon patterns would be very different from today
https://en.wikipedia.org/wiki/Pangaea

I have also heard a suggestion that there may have been large deserts in the interior of this large landmass.

16

Question of the Week / Re: QotW - 24.12.12 - Is there any way to harness nuclear energy other than steam?

« on: 15/12/2024 04:22:07 »

The NS episode broadcast with this QOTW answer described an intriguing Diamond/Carbon 14 battery with no moving parts (similar to Alan's description above).

I infer from this description:
- an artificial diamond is grown (using Chemical Vapour Deposition, CVD?), containing a layer of carbon-14 mere micrometers thick
- Beta particles are emitted by the C-14, with average energy 156 keV
- These Beta particles (very high-energy electrons) tear electrons off thousands of nearby atoms
- Surrounding the C14 are doped regions forming a semiconductor diode, which corral the liberated electrons into a DC electronic circuit
- The doped regions produce a DC voltage of around 2V, at low current  (the voltage would be below 5.5V, which is native diamond's band-gap)
- 2 to 5V DC is compatible with low-power electronics
- The surrounding diamond keeps the beta particles away from nearby sensitive electronics or living cells
- It doesn't need a vacuum chamber
https://www.thenakedscientists.com/articles/interviews/radioactive-diamond-battery-will-last-thousands-years

There is an environmental angle to this:
- The UK has a lot of graphite blocks from decommissioned nuclear reactors, which they want to dispose of safely
- The neutron radiation in the reactor turns normal C12 into C13 and C14, mostly on the side nearest the nuclear fuel.
- The C14 makes the blocks radioactive, and thus harder to manage
- By shaving off the C14-contaminated parts of the blocks, the blocks are easier to handle
- This demonstration diamond battery is a possible use of the recovered C14 (after enrichment)
- An earlier prototype used radioactive Nickel-63
https://www.bristol.ac.uk/cabot/what-we-do/diamond-batteries/

17

Question of the Week / Re: QotW - 24.12.12 - Is there any way to harness nuclear energy other than steam?

« on: 11/12/2024 01:38:21 »

Pioneer (Thermoelectric)... why it is still going strong?

The Voyager 1 & 2 spacecraft had 3 Thermoelectric generators each, powered by Plutonium-238 (half-life 88 years).

Each generator:
- Produces 2400W of heat (halving every 88 years)
- Generates 157W of electricity (halving every 88 years)
- It was launched in 1977, so it hasn't reached its half-life yet
- but NASA has had to power down some instruments in order to keep others operating at full power.
https://en.wikipedia.org/wiki/MHW-RTG

The more modern device on the Mars Curiosity rover supplies both:
- electricity (to power the electronics)
- and heat (to keep the electronics warm during the cold Martian night).
https://en.wikipedia.org/wiki/Multi-mission_radioisotope_thermoelectric_generator

18

Question of the Week / Re: QotW - 24.12.12 - Is there any way to harness nuclear energy other than steam?

« on: 09/12/2024 20:31:45 »

Many nuclear reactors use water for cooling, but other designs have been used:
- Gas-cooled reactors https://en.wikipedia.org/wiki/Gas-cooled_reactor
- Liquid-metal cooled reactors (eg using liquid sodium or liquid lead as a coolant) https://en.wikipedia.org/wiki/Liquid_metal_cooled_reactor

One proposed design for a helium gas-cooled reactor would use the Helium gas to directly turn a gas turbine, potentially achieving high efficiency. https://en.wikipedia.org/wiki/Gas_turbine_modular_helium_reactor
- But as far as I know, most reactors separate the nuclear cooling circuit from the power generation circuit with a heat exchanger; this assists maintenance of the turbines since they should not become radioactive. Normally, water/steam is the working fluid feeding the power-generating turbines.

19

Question of the Week / Re: QotW - 24.12.12 - Is there any way to harness nuclear energy other than steam?

« on: 09/12/2024 20:21:43 »

Researchers investigated nuclear-powered propulsion, where:
- In the atmosphere, the nuclear reactor heats the air, which expands and propels the airplane
- In space, the nuclear reactor heats a propellant, which expands and propels the spaceship
       - Water would not make a good propellant, as it's latent heat is too high

Nuclear-powered airplanes were not put into production, as an airline crash would spread nuclear waste across a wide area.
- A nuclear-powered spacecraft would be less of a problem, provided the reactor was not fired up before reaching orbit (ie only low-radioactive materials present), and they were very confident it would never return to Earth.

See: https://en.wikipedia.org/wiki/Nuclear_thermal_rocket

20

Question of the Week / Re: QotW - 24.12.12 - Is there any way to harness nuclear energy other than steam?

« on: 07/12/2024 08:48:10 »

beta emitters ... to power ultra low power equipment

For maximum power output, the ideal operating voltage for a typical beta emitter is around 500,000 Volts,
- which is a bit high for low-power electronics (which typically operate at < 1V)

See a typical beta particle energy spectrum here: https://en.wikipedia.org/wiki/Beta_decay#Description