karl-j

The site also fails to track on mobile Safari with ”Prevent Cross-Site Tracking” turned on.

Fascinating. That’s a lot like Passive Coherent Location (PCL), if normal echolocation is like radar.

English has the exact same problems as you’re mentioning, and an explanation using the English words would be much more relatable to readers of HN.

I might have agreed with you if Apple was a good gardener. That would involve weeding out the scams in the app store, giving developers feedback on radars, and being more communicative and reasonable in app review.

The placement of punctuation is the reason I believe Dvorak is better than most other optimized layouts. They may be optimal for their metrics, but their metrics are bad.

I have been thinking about trying a one-handed layout lately, the one you link is intriguing!

It is appreciated, but we all have to choose our battles.

From the article the difference doesn’t seem that huge:

Stockholm - 0.8 unicorns per 100,000

Silicon Valley - 1.4 unicorns per 100,000

I think I'm almost as uninformed as you, but I believe it comes down to the difference between perfect solutions and close enough solutions. Consider the classic NP problem of the traveling salesman problem.

"[Modern heuristic and approximation algorithms] can find solutions for extremely large problems (millions of cities) within a reasonable time which are with a high probability just 2–3% away from the optimal solution." [0]

When close enough is enough, NP problems can often be solved in P time, and I suspect this is one of those cases. For crypto however, close enough is not enough.

[0] https://en.wikipedia.org/wiki/Travelling_salesman_problem#He...

I believe the other commenter is referring to a distortion of mental perspective, not geometry, and honestly I’m buying it. It’s so strange to look at a globe upside down, even though there’s nothing unnatural about it.

So let’s say I’ve got step 2. figured out with vacuum decay or similar, how do I check if the list is sorted in O(1) to determine if I destroy the universe or not?

And given that the list being sorted is a one in n! chance, often enormously less likely than than hardware malfunction, wouldn’t the algorithm mostly produce malfunctions rather than sorted lists?

(Genuinely curious if I’ve got the right understanding of the CS and potential physics.)

I did not participate in the project, and I agree the seed is almost worthless to the world but I don't think the project was a waste of anything.

The minute inherent value of the answer is not why it was done. Finding the answer became personally valuable to people for a few reasons:

The unavailability made it seem more valuable. The idea of making something seemingly unknowable known is enticing. Making headway on a problem makes the solution personally valuable. The production, rhetoric, and appeals to nostalgia in Sal's first video about the project made it seem more valuable to many. Being part of a group who share an objective that matter to them is inherently valuable to humans.

I believe the project added value to the lives of everyone involved, and the experience gained and the connections made will add value to the rest of the world.

All of this could have been true for a project that actually matters, yes, but those projects tend to have high barriers to entry, consequences for failure, and distant horizons of success. I think this project replaced time and computing power that would have been spent on games and youtube, not on important problems.

I'd be interested to see your calculations, because I'm just doing it according to the book, blindly following Friis transmission equation. It sounds like you are applying more physics based thinking to the problem. I have no clue how many photons the antennas are spitting out or receiving, just the gains and losses associated with the antenna size and distance.

I'm writing out the basics of the solution below, but the physical reason for the non-impossibility is that the problem statement assumes the lowest possible amount of noise to overcome, long symbol durations, and high gain antennas.

For learning resources to recommend I'm lacking a little, since I mainly relied on lectures etc, but if you're interested in terrestrial wireless communications you could check out Stanford's class by Andrea Goldsmith. [1] There's very little about antennas, satellites, long distance communications and all that, but a draft of her book is available and all the lectures, so it's very comprehensive even though it's only tangentially related. You can also check out the link budget Wikipedia page [2] for an overview of things affecting these kinds of transmissions, as well as many links to interesting related topics, like the voyager program and their unique struggles (300+dB path loss and still hanging in there!)

The path loss is L = (4 * pi * d/lambda)^2, where lambda is wavelength. At 1.5GHz carrier frequency this results in L = 1.41e38 = 382dB, which definitely is a monstrous number, and with no antenna gain and terrestrial noise powers this would be practically impossible to overcome.

But with an equivalent receiver noise temperature of 5K (meaning the noise we are receiving is only the faint radio noise from space [3]) and a bandwidth of 100Hz the signal is only competing with noise with power N_0 = kBT = 6.90e-21W = -202dBW giving us some hope of establishing communications.

The gain of the 300m diameter antenna is G = 4 * pi * Area/lambda^2 = 2.2e7 = 74dB, and we have one transmitting and one receiving so we can double that dB gain.

Given the Eb/N0 = 10dB requirement and the rate of R = 48bps we can figure out the necessary received power after the antenna gain. Energy per bit is N_0 * 10, so the received power has to be Pr = N_0 * 10 * R = 3.3e-18W = -175dBW.

The transmit power plus gains minus loss has to be greater than the receive power limit, so it should be Pt >= Pr - 2G + L = -175dBW -(2 * 74)dB + 382dB = 59dBW = 800kW

I'm getting a different answer here because the exam had some additional pointing/polarization loss, which I apparently flipped the sign on in my solution. So the correct answer for my problem should be in the low MW, but still not outlandish. I have not received the corrected exam yet, so there might be other errors too.

[1] https://web.stanford.edu/class/ee359/courseinfo.html

[2] https://en.wikipedia.org/wiki/Link_budget

[3] I'm a little unclear on how this would be achieved, since the earth antenna is, well, earth based and at some 290K. This is however what the problem assumed, so maybe they're counting on cooled space based antennas.

Those are not my words, they're all from my professor and this [1] book, chapter 23. With remote control and immediate feedback I'm talking about closed loop control. Consider industrial automation with image processing done remotely, or immediate visual or tactile feedback to human operators of remote machinery and equipment.

[1] https://www.amazon.com/4G-LTE-Advanced-Pro-Road-5G/dp/012804...

Keep in mind you can increase the energy per bit by increasing symbol duration.

I had a problem like this on my wireless systems exam recently, where the setup was two Arecibo style antennas with a reasonable 20ly distance, a low 48bps, an Eb/N0 of at least 10dB, and a few other reasonable assumptions. The transmit power needed turned out to be less than 250kW.

5G is not mainly for consumers like you and me. We are not willing to pay significantly more for the faster speeds, most people are plenty happy with 4G. The big difference with the 4G to 5G transition compared to the previous transitions is not speed, but flexibility.

5G aims to allow for completely new applications that were not possible before, and hoping that's where the money will come from. Ultra-reliable and low latency, and massive machine type communications are two new areas 5G is pushing into. The first will allow applications like self driving cars, remote control with immediate feedback, and combined with the increased speeds, augmented and virtual reality. The second area is for the smart city/home type of applications.

This is all from my digital communications professor with ties to Ericsson, but on a personal note I'd be hype to explore distant places in real time by wearing a vr headset and controlling a drone with a 360° camera and <10ms latency. You could be anywhere in the world and actually interact with the environment with just a 5G enabled headset and a 5G-drone renting app. Racing through an abandoned mall! Drone laser tag in a redwood forest!

After the field of straw men and bad made up definitions the author does actually arrive at something resembling that conclusion.

> There is no single thing named "electricity." We must accept the fact that, while several different things do exist inside wires, people wrongly call all of them by a single name.

I took note of that part too, it reminds me of this article [1] posted on HN recently. It contrasts the fleeting and context dependent flows of posts on social media ("the stream") with enduring wiki style interlinking of posts where the context is embedded in the linking ("the garden"). It consider it in the context of personal note taking, and I feel what you mention is the garden approach to conversation, as opposed to the normal stream approach.

I wonder what the medium would have to be like to be useful for instant messaging, since not all things being said need to endure or benefit from linking. Maybe the ink fades unless new things are written nearby, proving its relevance?

[1] https://hapgood.us/2015/10/17/the-garden-and-the-stream-a-te...

> All this to say, the test is simple and pretty quick.

Just to curb peoples expectations a bit, I started the process of getting diagnosed about two years ago, got the diagnosis less than a year ago, and I'm having the first meeting with a doctor who can actually prescribe meds next week. No part of it has been simple or quick. So I guess YMMV.

Two simultaneous out of phase sound waves do cancel each other out, there's not some 'silent sound pressure' left.