Getting an EKG seems very prudent. I had one done for a non-heart related procedure, and afterwards was basically asked: - Ever have any heart events? Heart racing, palpitations, that kind of thing? - Yes, a few times a year I've noticed events like that. Resolves in a few minutes, though. - Well, your EKG shows a slurred delta wave. Sign of Wolff-Parkinson-White syndrome. Might want to get that checked out.

I did, and it was. Fixed with ablation. No issues since. Other types of supraventricular tachycardia can also be cured with ablation.

Minute I read the chain above I was looking for someone to point out WPW. It’s relatively easy to manage or cure once you catch it.

If you do both (use flipped parentheses around the operators), it makes even more sense, and makes the parsing trivial to boot: just surround the entire expression with parentheses and parse normally. For instance: 1 + 2 )( 3 Becomes (1 + 2 )( 3) Which is actually just what the author wants. You might even want multiple, or an arbitrary numbers of external parentheses. Say we want to give the divide the least precedence, the multiply the middle, and the add the most. We could do that like: 1 + 2 )/( 3 ))(( 4 Surround it with two sets of parens and you have: ((1 + 2 )/( 3 ))(( 4)) I haven't just proved to myself this always does what you expect, though...

Many people think of driving in time rather than distance. I'd say it's actually more common to say a city is 3 hours away rather than 200 miles.

What makes kW less useful is really just that most EVs don't advertise their capacity very prominently. But if you knew you had an 80 kWh battery and the car uses 20 kW at freeway speeds, then it's easy to see that it'll drive for 4 hours.

The problem with this is that destinations are a fixed distance away, whereas their time distance is not fixed. In most journeys people want to reach a specific place rather than drive for a given amount of time.

I understand all this but the most important question for me is definitely still "how much distance can I cover on a charge"? That's why I prefer kWh/100km.

We know the upper bound for most of those numbers. SpaceX already achieves internal marginal launch costs of ~$1000/kg, for instance. We know their rough costs per satellite. In contrast, we know little to nothing about the inputs to the Drake equation.

The numbers don't quite work out in favor of orbital datacenters at the current values. But we can tell from analyses like this what has to change to get there.

You use of the word "quite" is highly "innovative".

OP here. Thanks SyzygyRhythm

I wouldn't downplay the opportunity cost of that much human capital. It really is quite a lot, given the obvious talents of the physicists.

I'm not saying I fully agree with the position, but one way of looking at it is that thousands of incredibly smart people got nerd-sniped into working on a problem that actually has no solution. I sometimes wonder if there will ever be a point where people give up on it, as opposed to pursuing a field that bears some mathematical fruit, always with some future promise, but contributes nothing to physics.

There is almost no opportunity cost: The academic pyramid swaps out the lower parts of the hierarchy at a high pace. You might lose a few smart people who become professors but the average sting theory phd goes to finance or whatever field requires absurd amounts of math at the moment.

You do get people who are happy for a few years since they can live their childhood dream of being a physicist before the turn to actual jobs.

Having people work on things that are at the limit of human understanding is an essential part of a modern educational system.

For every professional string theorist, you get hundreds of people who were brought up in an academic system that values rigor and depth of scientific thinking.

That's literally what a modern technological economy is built on.

Getting useful novel results out of this is almost a lucky side effect.

Indeed.

Aluminum is actually a (far) superior conductor to copper per unit mass. It would be used on transmission lines even if it was the same price as copper, because the towers can be cheaper and farther apart. It's in increasing use in EVs due to the lower mass.

Copper is still used when the conductive density matters, like the windings of an electric motor. But if copper prices increase further, manufacturers will make sacrifices to efficiency and power density in order to save cost. And they'll figure out how to better balance the use of Al vs. Cu, perhaps using Cu only for the conductors closest to the core.

We also use copper for transformers, which are fairy "dumb" in their usual design. Solid-state transformers exist, which use much less copper, but are currently more expensive. They will no longer be more expensive if the price of copper goes up too much. And they'll probably get cheaper in the long run anyway, regardless of copper price, in the same way that switch mode power supplies have totally replaced linear supplies in the consumer space.

I've seen increasing use of copper in fairly mundane uses, like computer heat sinks, that used to be aluminum. The performance is a little better, but it won't be worthwhile if copper gets way more expensive. They'll just go back to aluminum, or use some other innovation (carbon heat spreaders, etc.) if price becomes an issue.

We even use aluminium on "dumb" transformers for power transmission. Dry-type transformers tend to be physically larger because they use air and resin (rather than a tank of oil) to insulate, and so the major downside to aluminium conductors (needing a larger cross-section to carry the same current for the same loss) is no longer a limiting factor performance-wise. In most substations, and extra 20-30% physical size of the transformer is a fine trade-off for cheaper construction.

There has been substantial development in a replacement for all copper wires in the form of CCA - copper clad aluminum conductors.

This product combines the advantages of both materials - low price and mass, stable connection, can be soldered etc. while using a small fraction of copper. It's making inroads into aviation and motor vehicle harnesses, and will probably be the default low cost option for new homes in a few decades.

> I've seen increasing use of copper in fairly mundane uses, like computer heat sinks, that used to be aluminum.

Copper heatsinks go in and out of style... Copper heat pipes have stayed en vogue, but typically embedded in aluminum blocks.

I'd suppose the fashion goes somewhat with the price of copper, though I haven't tracked it. The heatsinks themselves have gotten far larger as CPUs and GPUs have gotten more power hungry, not to mention RAM and SSDs. A material that's a good tradeoff at one scale isn't necessarily one at a different scale.

At any rate, one should expect many of these trades to go the way of Al if Cu gets more expensive (which it might not). Not all of them, but we'll probably see a bias towards physically larger systems in cases where space isn't at a premium. And also a bias towards active systems over passive, liquid cooling over air, and so on.

I've found that quite a lot of cheap keyboards cannot register a T when shift-R are being pressed. If I always used the standard QWERTY finger positioning, this wouldn't be a problem, because my index finger could not be on both R and T at the same time. But when typing a word like (all-caps) SMART, I tend to use middle-index to quickly type the RT, and R is still depressed when I hit the T. So the T does not register.

Most decent keyboards don't do this, but even there I've seen exceptions. Very annoying.

This is important. The mechanism doesn't really work the way you want most of the time. I occasionally see a claim that you can power a carousel with this method, but it doesn't work. You would have to have the cable go out and around the carousel structure, and then into the top. And the cable would still move relative to the ground and the carousel.

You could, in principle, have a totally internal system, but with arms that grab and release the cable at intervals so that the looped portion can pass by them. You could arrange the timing so that electrical contact is never lost. But you are still making/breaking contact and it starts to lose some apparent advantages compared to a slip ring.

That's not to say it isn't still useful for some purposes, like maybe a radio antenna that isn't too impacted by a cable moving in front on occasion. But it doesn't eliminate all uses for a slip ring.

I can't go into detail, but that's essentially my use case. I have a geodesic dome with a cable running up externally, and would like to run it through a hollow shaft coming in through the top which rotates like a carousel. I'm fairly certain this is precisely what I need.

Even with the visualization, I found the minimal solution hard to visualize. I came up with this instead:

Suppose you start with two separated intervals. The left one starts sliding rightward. At what point do they contact? That's easy, it's just when (end1 > start2).

As it continues sliding, at what point do they lose contact? Again, easy: it's where (start1 >= end2).

So the solution is the first condition and the negation of the second, i.e.: (end1 > start2) && (start1 < end2)

The article mentions that some flights produce a net cooling effect. I wonder if it could be cost effective to divert flights toward contrail formation when it's predicted that they'll produce cooling (I also wonder what the actual circumstances are when they produce cooling--low surface temperatures, maybe?).

Perhaps also early morning flights where most of the contrail's lifespan will be in sun.