DiscussMormonism.com

canpakes wrote: ↑

Mon Oct 25, 2021 8:38 am

Gunnar wrote: ↑

Mon Oct 25, 2021 7:37 am

I wouldn't go so far as to say "shocked."

I’ll bet that even though Doc may not be current on his electrical knowledge, he’ll show no resistance or reluctance to getting up to speed. It never hertz to be more grounded on watt to know.

Chap wrote: ↑

Mon Oct 25, 2021 10:30 am

Well, at least Moore is honest enough to lie when he is paid to lie! If he told the truth he would be cheating his employers.

Physics Guy wrote: ↑

Mon Oct 25, 2021 12:10 pm

Once you've got [electrons] up to high voltage, though, they can coast along at a pretty even potential. They're not feeling any big forces or hitting anything hard. They're drifting quietly along in that high-potential power line like a bunch of rich kids riding a bus with thousands of bucks in their pockets, acting like any other bus full of kids—until they get off at the mall and start shopping.

My top 3 impressions up-front:

The sea level projections for the year 2100 have been adjusted upwards again.

The IPCC has introduced a new high-end risk scenario, stating that a global rise “approaching 2 m by 2100 and 5 m by 2150 under a very high greenhouse gas emissions scenario cannot be ruled out due to deep uncertainty in ice sheet processes.”

The IPCC gives more consideration to the large long-term sea-level rise beyond the year 2100.

Since 1900 the rise has greatly accelerated. During the most recent period analyzed, 2006-2018, it’s been rising at a rate of 3.7 mm/year – nearly three times as fast as during 1901-1971 (1.3 mm/year). The IPCC calls this a “robust acceleration (high confidence) of global mean sea level rise over the 20th century”, as did the SROCC in 2019.

The finding of sea-level acceleration is not new. The AR4 already concluded in 2007: “There is high confidence that the rate of sea level rise has increased between the mid-19th and the mid-20th centuries.” And the AR5 found in 2013 that “there is high confidence that the rate of sea level rise has increased during the last two centuries, and it is likely that global mean sea level has accelerated since the early 1900’s.” (Which has not stopped “climate skeptics” from repeatedly claiming a lack of acceleration.)



Source: IPCC AR6 Fig. 2.28c
The reason for earlier hedged wording by the IPCC was the possibility of natural decadal variability affecting the trend estimates, but the AR6 now concludes “that the main driver of the observed global mean sea-level rise since at least 1970 is very likely anthropogenic forcing”. That is the result of so-called “attribution studies” – attempts to differentiate with the help of a combination of data, models, pattern detection and statistics between all possible human-caused and natural factors in the observed changes. However, on the level of basic physical reasoning, it is of course a no-brainer that warming will cause land-ice to melt (and melt faster as it gets hotter) and ocean waters to expand, so sea-level rise is the inevitable result.

Physics Guy wrote: ↑

Mon Oct 25, 2021 12:10 pm

Chap is correct about high-voltage power transmission being quite efficient. The loss in transmission itself is typically only a couple of percent even for transmission over hundreds of miles. Pretty much every other stage of the process of generating and distributing electricity is much less efficient than long-distance transmission. That's why we accept the danger of enormous voltages running in power lines.

Voltage is also known (somewhat archaically) as electrical tension, or as electric potential. Electric potential is a property that every point in space simply has, in the same way that it has a gravitational potential. The gravitational and electrical potentials are separate things but in many ways they are similar. If the potential is higher here and lower over there, then in between there is a gradient in the potential—a downhill slope. That downhill slope in potential is a force, either gravitational or electrostatic. The force is what you can feel, but the potential is kind of the back story behind the force.

The potential at each point in space is a variable property that can change over time. In the case of the gravitational potential, for example, it changes over the course of the day as the Earth rotates under the moon, and the changing gradients in gravitational potential around the surface of the Earth are the gravitational forces that cause tides. A big difference between the gravitational and electrical potentials is that we can't do much to control the gravitational potential. It's only significantly affected by things at least as big as a moon, and we lack the technology to push moons around. So the gravitational potential affects us but we pretty much have to just take the gravitational potential field that Nature gives us. The electrical potential, in contrast, is something we can control. You can mess around with the electrical potential, at least within a small region of space, by rubbing a balloon in your hair. With big generators we can raise the electrical potential up to tens of thousands of volts within a power line running hundreds of miles.

It takes force to push electrons up to high voltage, because that means pushing them uphill in the potential gradient. Once you've got them up to high voltage, though, they can coast along at a pretty even potential. They're not feeling any big forces or hitting anything hard. They're drifting quietly along in that high-potential power line like a bunch of rich kids riding a bus with thousands of bucks in their pockets, acting like any other bus full of kids—until they get off at the mall and start shopping. When those electrons eventually come out of the power line and flow into some place where the potential is lower, the potential gradient is a force that can push the electrons hard and do a lot of work with them. So pushing fewer electrons through the power line, but cranking the power line up to high electrical potential, is a fundamentally efficient way to transfer power over long distances.

The electric potential is a funny thing, all right. As far as we know it's not an analogy for anything else, but just the literal truth of how the universe really is. As far as we know it's not made out of anything else; other things are made out of it. It's one of the basic aspects of reality.

And explaining what it is is actually one of the things I'm supposed to be doing today, so for once I'm not just distracting myself from tedious work by posting on this board. This time I'm thinking about my upcoming lecture. Hooray!

Chap wrote: ↑

Mon Oct 25, 2021 4:56 am

Doctor CamNC4Me wrote: ↑

Sun Oct 24, 2021 11:49 pm

I literally didn’t understand any of that. Do I feel ashamed? Yes. Am I going to pretend that sending electricity over long distances isn’t a problem based off your post? Yes. Am I confused by your statement regarding DC and transmission? Yes. But that’s only because I read this cartoon by the Oatmeal:

https://theoatmeal.com/comics/tesla

Could I google DC vs AC and something something power grids to be less ignorant? Yes. Am I going to do it? I dunno. Maybe.

- Doc

DrC seems to be an energetic, intelligent, and capable person (also a rather honest person, to judge from his admission above). But it appears that his education and experience have not fitted him to understand statements that express elementary and important facts about the way electric currents through wires can act as a means of transferring energy, a physical phenomenon on which major parts of 21st century life is based.

Can I just do a quick straw poll here, and ask posters who feel that they DO understand my post to indicate briefly?