Hacker News 上看到 Starlink 打算跟 T-Mobile 合作，直接用衛星提供 5G 訊號讓地面手機使用：「SpaceX, T-Mobile to connect satellites to cellphones in remote areas (wsj.com)」，原報導在 WSJ 的「SpaceX, T-Mobile to Connect Satellites to Cellphones in Remote Areas」這邊，另外因為 paywall 的關係，可以在這邊讀。

Mr. Musk said the service would use second-generation Starlink satellites that would be outfitted with large antennas that cover swaths of land that have no service. SpaceX has a pending application before the FCC to launch around 30,000 of the second-generation satellites over time.

The service won’t require mobile users to get a new phone. Musk said in or after a natural disaster, even if all the cell towers are taken out, the planned service should work.

Mr. Musk said that the bandwidth would be limited and that the new satellite service wouldn’t supplant existing ground-based cellular services. “This is meant to provide basic coverage to areas that are completely dead,” he said.

Hacker News 上有蠻多人在算技術上的可行性，除了訊號強度外，衛星與地面相對速度比目前地面上的交通工具都快，都卜勒效應 (Doppler effect) 看起來也是個會影響很多的主題...

## 白宮宣佈由政府資助的研究，都必須馬上公開

In a memorandum to federal departments and agencies, Dr. Alondra Nelson, the head of OSTP, delivered guidance for agencies to update their public access policies as soon as possible to make publications and research funded by taxpayers publicly accessible, without an embargo or cost.

In the short-term, agencies will work with OSTP to update their public access and data sharing plans by mid-2023. OSTP expects all agencies to have updated public access policies fully implemented by the end of 2025.

## Banner blindness

Banner blindness is a phenomenon in web usability where visitors to a website consciously or unconsciously ignore banner-like information. A broader term covering all forms of advertising is ad blindness, and the mass of banners that people ignore is called banner noise.

The first banner ad appeared in 1994. The average click-through rate (CTR) dropped from 2% in 1995 to 0.5% in 1998. After a relatively stable period with a 0.6% click-through rate in 2003, CTR rebounded to 1% by 2013.

## 美國汽車的兒童安全座椅法律，影響生育的意願

Hacker News Daily 上看到的，原文標題比較漂亮：「Car Seats as Contraception」，在 Hacker News 上也有討論：「Car seats as contraception (ssrn.com)」，重點是作者之一 (David H. Solomon) 也有跑上去回應。

Abstract 的部份把重點都講出來了，1977 年美國通過汽車的兒童安全座椅法律，但大多數的汽車無法放下第三張座椅，這反而使得生第三胎的成本大幅提高 (需要買空間更大的車)，然後另外拉出資料分析因為法律而制止的車禍數量：

Since 1977, U.S. states have passed laws steadily raising the age for which a child must ride in a car safety seat. These laws significantly raise the cost of having a third child, as many regular-sized cars cannot fit three child seats in the back. Using census data and state-year variation in laws, we estimate that when women have two children of ages requiring mandated car seats, they have a lower annual probability of giving birth by 0.73 percentage points. Consistent with a causal channel, this effect is limited to third child births, is concentrated in households with access to a car, and is larger when a male is present (when both front seats are likely to be occupied). We estimate that these laws prevented only 57 car crash fatalities of children nationwide in 2017. Simultaneously, they led to a permanent reduction of approximately 8,000 births in the same year, and 145,000 fewer births since 1980, with 90% of this decline being since 2000.

## 證明圓周率 π 是無理數

$\frac{d}{dx} sin(x) = cos(x)\newline\newline\frac{d}{dx} cos(x) = -sin(x)$

$\frac{d}{dx} f(x)g(x) = f'(x)g(x) + f(x)g'(x)$

## MIT 終止與 Elsevier 的合約

In Taiwan more than 75% of universities, including the region's top 11 institutions, have joined a collective boycott against Elsevier. On 7 December 2016, the Taiwanese consortium, CONCERT, which represents more than 140 institutions, announced it would not renew its contract with Elsevier.

## 原來 Fully Homomorphic Encryption 已經被解啦...

Hacker News Daily 上看到「IBM Releases Fully Homomorphic Encryption Toolkit for MacOS and iOS; Linux and Android Coming Soon」這個消息，主要是 IBM Research 要放出一些跟 Fully Homomorphic Encryption (FHE) 的 library。

Homomorphic encryption 講的是直接對密文操作：(這邊的 $\cdot$ 是操作，可能是加法，也可能是乘法，或是其他類型)

$C_1 = enc(P_1)$
$C_2 = enc(P_2)$

$enc(P_1 \cdot P_2) = enc(P_1) \cdot enc(P_2) = C_1 \cdot C_2$

(雖然只用了十頁主要還是因為 STOC 篇幅的關係，但扣掉 circuit privacy 的部份，前面在說明建構與證明的過程只用了九頁也是很驚人)

## SETI@home 計畫將在月底停止

SETI@home hibernation
On March 31, the volunteer computing part of SETI@home will stop distributing work and will go into hibernation.

## 四個機率問題

• 每一次有 $\frac{1}{N}$ 成功的機率，跑 $N$ 次後最少成功一次的機率。
• $N$ 個球隨機丟到 $N$ 個籃子後有空籃子的機率。
• $N$ 個數字在隨機排序後有數字不改變位置的機率。
• $N$ 種 coupon 平均隨機出現，要抽中一套 $N$ 種都有的 coupon 需要抽幾次的期望值。