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Physics, Astronomy & Cosmology / Re: What is a black hole made of?

« on: Yesterday at 20:54:30 »

The literature says that there is a wave effect that excludes things from the event horizon- particles bounce off. Think of it a bit like super charged refraction, or unmatched transmission line terminations causing reflections.

If you think of it in terms of Feynman quantum particles, summing over all the possible paths, a path that crosses the event horizon will basically not return so doesn't contribute to the wavefunction just outside the event horizon, whereas ones that stay outside can reinforce the ones outside heading away from the event horizon.

The argument that the event horizon is not special is a purely classical argument, and pays no attention to QM. But nature seems to primarily follow QM.

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Technology / Re: Are solar panels worthwhile?

« on: Yesterday at 04:05:59 »

Nah, not even in the UK.

https://www.carbonbrief.org/solar-wind-nuclear-amazingly-low-carbon-footprints/

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Technology / Re: Are solar panels worthwhile?

« on: 04/07/2022 23:18:36 »

answer is Yes.
Ref: https://www.thenakedscientists.com/forum/index.php?topic=84600.0

To produce enough solar panels to generate the electricity for the uks current usage would require somewhere in the region of 1 billion tonnes of co2, for all our usage that figure is at 10 billion . 

And it would break even in a few years at the absolute most.

Meanwhile the price of coal and natural gas is soaring. Some places subsidize their local power with low-cost petrochemicals. The UK used to do that, British natural gas was sold within the UK at cut-price costs, but they're running out in the North Sea. And so the price is now rebounding to the world price-nearer what it probably should have been all along, and suddenly solar and wind actually makes loads of sense.

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Physics, Astronomy & Cosmology / Re: What is a black hole made of?

« on: 04/07/2022 22:31:10 »

...the 'Firewall model' of black holes where all the mass of a black hole is concentrated at the event horizon

Let's take the scenario where a neutron star draws more and more material from an orbiting star onto its surface - until it collapses into a black hole perhaps 10miles across.

Within that 5 mile radius of the event horizon, there would already have been a considerable amount of matter while it was still a neutron star. So that can't really still be stuck on the event horizon.

If it were possible to observe the formation of the black hole (eg with a neutrino telescope), the core of the neutron star might be creeping inwards, just a micrometer from the event horizon - but the event horizon would be bounding outwards by yards and miles. So that material would no longer be stuck on the event horizon (from the viewpoint of a distant observer).
https://en.wikipedia.org/wiki/Neutron_star#X-ray_binaries

That bothered me for quite a while, but I think there's a snow plow effect. As the event horizon tries to form in the first place any matter inside gets expelled.

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Physics, Astronomy & Cosmology / Re: What is a black hole made of?

« on: 28/06/2022 05:49:58 »

I personally don't think there's anything in a Black Hole. I favour the 'Firewall model' of black holes where all the mass of a black hole is concentrated at the event horizon. My logic is that quantum mechanics means that everything moves as a wave, but the wave function should be effectively zero at an event horizon, so everything will bounce off and hang around just outside, and in fact I think that the horizon can't completely form, but it can get arbitrarily close to forming, there's very, very little mass within where the classical event horizon would be. But I freely admit this is just my opinion.

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Technology / Re: Are solar panels worthwhile?

« on: 26/06/2022 04:13:04 »

Everyone talks about cost, they never talk about the profit. If you install solar panels you're virtually guaranteed to save money, they typically pay for themselves in 5-10 years. The best angles to place them in the UK are usually about 30-40 degrees to the horizontal, facing south east and/or south west. That gives you electricity in the mornings and evenings when you need it (mainly in spring, summer and autumn). The solar electricity costs about 6p/kWh, and it saves you spending ~27p/kWh on electricity.

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General Science / Re: So how big a nuclear bomb would it take to cover the UK with a tsunami anyway

« on: 04/05/2022 20:05:24 »

I mean it's basically a tsunami bomb:

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

Which does raise the question: What, exactly, has the "nuclear deterrent" deterred? The Soviet Union was an ally of the western powers until they acquired nuclear weapons, since when there have been wars all over the world, mostly with little point and no desirable outcome.

I know what it didn't deter. It didn't deter Russia from invading Ukraine. There was no deterrent, after Ukraine agreed to give up the nuclear weapons they actually had to Russia, shortly after the USSR fell.

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General Science / So how big a nuclear bomb would it take to cover the UK with a tsunami anyway

« on: 04/05/2022 00:21:12 »

Apparently in Russian state media they're threatening to do this. Is this even remotely practical? I'm doubting they've got a big enough bomb to do that, but I'm prepared to accept a worked example proving otherwise.

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Question of the Week / Re: Can the Earth be used as a dynamo?

« on: 29/04/2022 02:36:55 »

Linda asks: Can the spinning of the Earth be used as a source of electricity, similar to the spinning of wind turbines?

The spinning of the Earth itself can't be the source of electricity, since the Earth has to conform with conservation of angular momentum. Unless something left the Earth or joined the Earth or another external body changed speed, or the Earth radically changed shape, no closed cycle can result in the Earth simply slowing down and electricity being generated, as it will always have the same angular momentum.

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

« on: 25/04/2022 23:32:26 »

I'm afraid money rules, if renewable where economically superior we would have converted to them already.

It will in a few years, and the progress is exponential.

Exponential,

At this point I'm assuming you're just here to troll all of us.

While an exponential decay is indeed an exponential, this is what the worldwide solar power looks like on a semilog graph:

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Technology / Re: Are solar panels worthwhile?

« on: 25/04/2022 21:29:54 »

Conspiracy theories can be fun

12

Technology / Re: Are solar panels worthwhile?

« on: 25/04/2022 21:01:35 »

Solar panels aren't scrapped after 25 years, they have about 0.5% loss of output per year, so they're still outputting nearly 90% of their original output after that. That's just the suggested lifespan, but they're clearly going to go a lot longer.

Whilst this is somewhat  true of current panels, many older panels are significantly worse, plus there is the lifespan of associated equipment/faults/ servicing.

https://news.energysage.com/how-long-do-solar-panels-last/#:~:text=The%20industry%20standard%20for%20a,below%20what%20the%20manufacturer%20projected.

But given this degradation that is reported widely at 1% a year and the lack of cloudy sky generation, I have to think this is being rushed into. When cloudy sky generation  is improved  most solar in the uk will be replaced.

No.

And because there's been little installation so far, most panels that will be installed will be new panels, and they give 0.5% a year:

https://www.nrel.gov/state-local-tribal/blog/posts/stat-faqs-part2-lifetime-of-pv-panels.html

Note that the UK may well be a lot less even than that, a lot of the degradation is due to stuff like high temperatures and damage from sunlight. The UK has less sunlight than many places (like Hawaii!) and is not a particularly hot country, so the calendar degradation should be much less.

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Cells, Microbes & Viruses / Re: Can some one here explain the biology of aging?

« on: 25/04/2022 03:23:33 »

There's almost certainly not any one thing. Ageing is caused by the build up of damage of one kind or another; and is in turn related to how well protected the organism is. Animals that are very well protected age much more slowly.

For example a tortoise has a hard shell, so can live for centuries, so has evolved genes for ageing very slowly. Humans are very good at looking after themselves so have evolved to live quite a long time. Birds can fly away, so live decades. Mice and bats are both mammals, but mice have short lives usually ending in crunchy squeaks when they get predated, whereas bats are a similar size but fly extremely well, and thus can largely avoid danger; again they can live for decades.

Ageing slowly is thought to require extra genes. If an organism is going to die anyway before those genes make much difference, those genes will not be selected for, and they will disappear from the organisms genome.

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

« on: 25/04/2022 01:46:39 »

This must be an odd definition of 'subsidy', both natural gas and coal power are uneconomic compared to the unsubsidized price of solar and wind power in the UK. At the moment at least, increased use of solar and wind reduce the cost of electricity.

That certainly wasn't historically true not even a few years ago, but it is right now.

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

« on: 24/04/2022 20:35:06 »

Problem with solar is that all the sources go off line at the same time, and windmills may not work at all for several days at a time - the primary sources are not independent.

But you know it's doing that before it happens, because of something called a 'weather forecast'.

This wouldn't be a problem if renewable generators were backed up with adequate storage, but that would not be profitable, so grid integrity relies on fossil fuels to maintain the profitability of renewables.

Thing is, backup generators are relatively cheap, and the grid already has them anyway. It costs fuel, but hydrogen and perhaps other things like ammonia is looking promising for that.

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

« on: 24/04/2022 17:57:39 »

Solar panels are made using electricity that comes from whatever is on that factories' grid.

These days significant fractions of that electricity in China are made using solar panels and wind, and whatever is on that grid is what's used to make solar panels.

ALL grids, everywhere are powered by UNRELIABLE sources: ANY power plant can fail or get disconnected at ANY time.

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Technology / Re: Why are solar panels not curved?

« on: 24/04/2022 01:37:53 »

The best angles to have your solar panels at is complex. Since about 2014 the cost of the panels are low enough that having more solar panel capacity than inverter capacity became cost effective. I believe I'm correct in saying that you would ideally want your panels facing north-east and north-west in your case; the cost of the extra panels is a small proportion of the cost of the system. When I ran the numbers on a system I was planning here, it was something like the cost went up by 15% and the productivity went up by 20%.

East-west systems approximate solar tracker outputs and may be optimal near the equator, and if you're not on net metering where the feed in tariff is small compared to the normal usage tariff if you're doing any significant self usage of the electricity.

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That CAN'T be true! / Re: Does the IVO thruster violate Newton's third law?

« on: 23/04/2022 04:32:20 »

There are classes of propulsion that don't require fuel, for example, interacting with the Earth's magnetic field. But I don't know what this is supposed to be, many of these things are bullshit.

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Technology / Re: Are solar panels worthwhile?

« on: 23/04/2022 04:22:12 »

The retail cost of electricity is the renewables subsidy. The retailer gets a profitable 27p per unit  whether the wind is blowing or not, so there is no incentive for the wholesaler to build the storage system needed for a fully renewable supply.

If the retailer is getting 27p/kWh then it's still in their interest to get the electricity for the lowest possible average cost. Note that wind power is usually sold on Contract For Difference, which is essentially a fixed price of 7p/kWh or whatever.

In practice, retailers are in competition with each other for customers, so they try to hold their price down- the 27p is not a given.

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General Science / Re: Do rockets violate conservation of energy?

« on: 22/04/2022 21:26:00 »

coe

hi again. other people on different fora have been debating the question. member "uatu" on the german allmystery.de forum has provided what I consider the definitive solution with a graph illustrating the key parameters. my primitive derivation indicated an initial parabolic rise in ke, followed by an asymptote at around 3/4 fuel consumption. the rigorous expression provided by "uatu" does the same followed by a sharp downturn. this derivation seems to be rock-solid, in my limited mathematical abilities. bottom line: the coe is safe and emmy noether can rest peacefully.

FWIW this is somewhat subtle stuff. There was actually some disagreement about the relationships between rockets and energy but it was laid to rest by Hermann Oberth.

He reported that at one point in his investigations of rocketry he believed he had completely disproven conservation of energy too, but he later was able to show that he hadn't.

See:

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

This links to 'Ways to spaceflight' which describes his mathematics which covers this and other topics.