SyzygyRhythm (u/SyzygyRhythm)

SyzygyRhythm commented on Inverse Parentheses kellett.im/a/inverse-pare... · Posted by u/mighty-fine

I think surrounding the operand would make slightly more sense, as in 1 + 2 (*) 3 as if it's a "delayed form" of the operation that it represents.

SyzygyRhythm · 18 hours ago

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...

SyzygyRhythm commented on CO2 batteries that store grid energy take off globally spectrum.ieee.org/co2-bat... · Posted by u/rbanffy

ekr · a day ago

What people care about when talking about EVs and consumption is generally how much distance they can cover. If you take away the distance factor and just report power, it becomes meaningless/almost useless.

SyzygyRhythm · 21 hours ago

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.

SyzygyRhythm commented on Economics of Orbital vs. Terrestrial Data Centers andrewmccalip.com/space-d... · Posted by u/flinner

zokier · 7 days ago

tbh this feels lot like people throwing Drake equation around. You put in whatever random numbers together and you can get any result you want.

SyzygyRhythm · 7 days ago

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.

SyzygyRhythm commented on String theory inspires a brilliant, baffling new math proof quantamagazine.org/string... · Posted by u/ArmageddonIt

glenstein · 10 days ago

Neil DeGrasse Tyson made an amazing point some years back that string theory costs practically nothing to develop. It takes some human capital to be sure, but in terms of infrastructure investments, it's pencils and paper and some computers. There's no high stakes mega project requiring massive infrastructure investments for questionable returns; no super colliders or gravitational wave detectors.

For a field repeatedly challenged for not bringing testable predictions to bear, the fact that so much of its rich theoretical framework has been able to be worked out with minimal infrastructure investment is a welcome blessing which, I would hope, critics and supporters alike can celebrate.

SyzygyRhythm · 10 days ago

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.

SyzygyRhythm commented on Running on Empty: Copper thehonestsorcerer.substac... · Posted by u/the-needful

toast0 · 14 days ago

> 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.

SyzygyRhythm · 14 days ago

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.

SyzygyRhythm commented on Running on Empty: Copper thehonestsorcerer.substac... · Posted by u/the-needful

chemotaxis · 14 days ago

I think the author is speaking authoritatively about things they may be less familiar with, or where they really want to push a particular doomsday / degrowth agenda (the only prescription at the end the article is that we need to stop technological progress). This paragraph in particular caught my eye:

> Bah! Who needs copper anyway, when we have so much aluminum?! > Have you thought about how aluminum is made? Well, by driving immense electric currents through carbon anodes made from petroleum coke (or coal-tar pitch) to turn molten alumina into pure metal via electrolysis. Two things to notice here. First, the necessary electricity (and the anodes) are usually made with fossil fuels, as “renewables” cannot provide the stable current and carbon atoms needed to make the process possible. Second, all that electricity, even if you generate it with nuclear reactors, have to be delivered via copper wires.

This seems to be trying to say that we can't make aluminum without copper, but that seems nonsensical. First, power can be delivered by wires made out of aluminum and indeed, it often is - I don't think that much of the transmission grid is copper. Second, the comparatively tiny amount of material needed for electrodes is a completely wacky argument. And renewables not being able to provide "the stable current" needed for smelting?

I'm not cherrypicking here, there's a lot of assertions of this type in the article. Essentially, everything is doomed and there's nothing we can do, because we're going to run out of copper. And fossil fuels. And there's absolutely nothing that can replace them, ever. And therefore, we shouldn't build AI datacenters? That's what it says...

SyzygyRhythm · 14 days ago

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.

SyzygyRhythm commented on Max Number of Simultaneous Key-Press (N-Key Rollover, NKRO, Ghosting) (2010) xahlee.info/kbd/keyboard_... · Posted by u/behnamoh

SyzygyRhythm · a month ago

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.

SyzygyRhythm commented on Mathematicians have found a hidden 'reset button' for undoing rotation newscientist.com/article/... · Posted by u/mikhael

meindnoch · 2 months ago

There's a bit of a caveat with the anti-twister mechanism, namely, that the wiring must be loose enough to pass around the supplied rotating part.

SyzygyRhythm · 2 months ago

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.

SyzygyRhythm commented on How to check for overlapping intervals zayenz.se/blog/post/how-t... · Posted by u/birdculture

SyzygyRhythm · 2 months ago

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)

SyzygyRhythm commented on Eliminating contrails from flying could be cheap sustainabilitybynumbers.c... · Posted by u/K2L8M11N2

SyzygyRhythm · 3 months ago

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?).