Peter Todd's hash collision puzzles Updated 2025-07-16
As mentioned at the prize was claimed at 8d31992805518fd62daa3bdd2a5c4fd2cd3054c9b3dca1d78055e9528cff6adc (2017-02-23) which spends several inputs with the same unlock script that presents two different constantants that have the same SHA-1:both givingIt was claimed on the same day that Google disclosed the collision: security.googleblog.com/2017/02/announcing-first-sha1-collision.html
printf 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 | xxd -r -p | sha1sum
printf 255044462d312e330a25e2e3cfd30a0a0a312030206f626a0a3c3c2f57696474682032203020522f4865696768742033203020522f547970652034203020522f537562747970652035203020522f46696c7465722036203020522f436f6c6f7253706163652037203020522f4c656e6774682038203020522f42697473506572436f6d706f6e656e7420383e3e0a73747265616d0affd8fffe00245348412d3120697320646561642121212121852fec092339759c39b1a1c63c4c97e1fffe017346dc9166b67e118f029ab621b2560ff9ca67cca8c7f85ba84c79030c2b3de218f86db3a90901d5df45c14f26fedfb3dc38e96ac22fe7bd728f0e45bce046d23c570feb141398bb552ef5a0a82be331fea48037b8b5d71f0e332edf93ac3500eb4ddc0decc1a864790c782c76215660dd309791d06bd0af3f98cda4bc4629b1 | xxd -r -p | sha1sumf92d74e3874587aaf443d1db961d4e26dde13e9cBoth of these are PDF prefixes, so they start with the PDF file signature, but are not fully viewable PDFs on their own.
Polytechnic Institute of Paris Updated 2025-07-16
Penalty kick left right Nash equilibrium Updated 2025-07-16
And before he kicks, the goalkeeper must also decide left or right, because there is no time to see where the ball is going.
Because the kicker is right footed however, he kicker kicks better to one side than the other. So we have four probabilities:
- goal kick left keeper jumps left
- goal kick right keeper jumps right
- goal kick left keeper jumps right. Note that it is possible that this won't be a goal, even though the keeper is nowhere near the ball, as the ball might just miss the goal by a bit.
- kick right and keeper jumps left. Analogous to above
PC game Updated 2025-07-16
Paulo Freire Updated 2025-07-16
en.wikipedia.org/wiki/Paulo_Freire:OMG so nice.
During his childhood and adolescence, Freire ended up four grades behind, and his social life revolved around playing pick-up football with other poor children, from whom he claims to have learned a great deal. These experiences would shape his concerns for the poor and would help to construct his particular educational viewpoint. Freire stated that poverty and hunger severely affected his ability to learn. These experiences influenced his decision to dedicate his life to improving the lives of the poor: "I didn't understand anything because of my hunger. I wasn't dumb. It wasn't lack of interest. My social condition didn't allow me to have an education. Experience showed me once again the relationship between social class and knowledge"
Pauli-X gate Updated 2025-07-16
The quantum NOT gate swaps the state of and , i.e. it maps:As a result, this gate also inverts the probability of measuring 0 or 1, e.g.
- if the old probability of 0 was 0, then it becomes 1
- if the old probability of 0 was 0.2, then it becomes 0.8
Paul Allen Updated 2025-07-16
Particle creation and annihilation Updated 2025-07-16
Predicted by the Dirac equation.
We've likely known since forever that photons are created: just turn on a light and see gazillion of them come out!
Photon creation is easy because photons are massless, so there is not minimum energy to create them.
The creation of other particles is much rarer however, and took longer to be discovered, one notable milestone being the discovery of the positron.
Partial index partial derivative notation Updated 2025-07-16
This notation is not so common in basic mathematics, but it is so incredibly convenient, especially with Einstein notation as shown at Section "Einstein notation for partial derivatives":
This notation is similar to partial label partial derivative notation, but it uses indices instead of labels such as , , etc.
Parity violation Updated 2025-09-17
This is quite mind blowing. The laws of physics actually differentiate between particles and antiparticles moving in opposite directions!!!
Only the weak interaction however does it of the fundamental interactions.
Some historical remarks on Surely You're Joking, Mr. Feynman section "The 7 Percent Solution".
It gets worse of course with CP Violation.
Paris Updated 2025-12-13
Ciro Santilli lived in Paris for a few years between 2013 and 2016, and he can confirm the uncontroversial fact that "Paris is Magic".
Not just one type of magic though. Every quarter in Paris has its own unique personality that sets it apart and gives it a different mood.
Ciro knows Paris not from its historical facts, but from the raw feeling of endless walks through its streets in different times of the year. Ciro is a walker.
Maybe one day Ciro will expand this section to try and convey into words his feelings of love for the city, but maybe the effort would be pointless. Maybe such feelings can only be felt by other free-roaming walker souls living in the city, and that is both beautiful and a shame.
Ciro had written the following in the past before he lived in smaller cities, started cycling and joined the Street reclamation movement he thought:Perhaps compared to São Paulo City, which is what he knew before that was true. But no, his standards have improved since. Paris has way too many cars. The noise of internal combustion engine vehicles is extremely annoying. And because there are too many personal vehicles, cars have to horn a lot to fight for space. Fuck cars. Paris has been making a big cycling push in the early 2020's, and that is great. But it is still far, far from good.
Paris is a friendly city to walkers, as it is not too large, and does not have too many extremely busy roads, you can basically cross all of it on foot.
Polyprotein Updated 2025-07-16
Parallel light Updated 2025-07-16
Often just called collimated light due to the collimator being the main procedure to obtain it.
However, you move very far away from the source, e.g. the Sun, you also get essentially parallel light.
Painted Skin (1992 film) Updated 2025-07-16
Paco de Lucía Updated 2025-07-16
Watching www.youtube.com/watch?v=-SbZZPX-y9g in 2022, who was one of his inspirations, made Ciro miss his guitar so much... one day, maybe, one day.
Oxford Quantum Circuits Updated 2025-07-16
Their main innovation seems to be their 3D design which they call "Coaxmon".
Funding:
- 2023: $1m (869,000 pounds) for Japan expansion: www.uktech.news/deep-tech/oqc-funding-japan-20230203
- 2022: $47m (38M pounds) techcrunch.com/2022/07/04/uks-oxford-quantum-circuits-snaps-up-47m-for-quantum-computing-as-a-service/
- 2017: $2.7m globalventuring.com/university/oxford-quantum-calculates-2-7m/
The Coaxmon by Oxford Quantum Circuits (2022)
Source. Oxford Physics student course notes Updated 2025-07-16
- liziyan1117.com/page/:All question PDFs are uploaded to that site. Solutions are scanned from paper notebooks.
These are my own solutions to selected problem sets and past papers of the Oxford MPhys course (Years 1-3) and the MMathPhys course from the years 2014 to 2018
From LinkedIn: - pjcc.physics.ox.ac.uk/resources/notes | www.scribd.com/document/654784089/CP3-Notes-Toby-Adkins# are lectures by Toby Adkins is pointed to from Oxford Physics Joint Consultative Committee. But they are closed, i.e. require you to be in the oxford network, though not necessarily with an Oxford login. As of 2023, he was doing a postdoc: www.physics.ox.ac.uk/our-people/adkins in fusion energy.
Oxford physics course handbook Updated 2025-07-16
The normal navigation to them was paywalled, but the static files are served without login checks if you know their URL. One way to go about it is to search by prefix on the Wayback Machine: web.archive.org/web/*/https://www2.physics.ox.ac.uk/sites/default/files/contentblock/2011/06/03/*
The last handbooks we can find are 2020/2021, they might have move to a new more properly paywalled location after that year.
- 2020/2021:
- Year 1: www2.physics.ox.ac.uk/sites/default/files/contentblock/2011/06/03/y1-ug-handbook-2020-2021-final-47501.pdf
- Year 2: www2.physics.ox.ac.uk/sites/default/files/contentblock/2011/06/03/y2-ug-handbook-2020-2021-final-47495.pdf
- Year 3: www2.physics.ox.ac.uk/sites/default/files/contentblock/2011/06/03/y3-ug-handbook-2020-2021-final-47496.pdf
- Year 4: www2.physics.ox.ac.uk/sites/default/files/contentblock/2011/06/03/y4-ug-handbook-2020-2021-final-47497.pdf
- Physics and Philosophy: www2.physics.ox.ac.uk/sites/default/files/contentblock/2011/06/03/pphandbook-47524.pdf
- 2019/2020. They seem to have split the handbook up per year after some point.
- Year 1: www2.physics.ox.ac.uk/sites/default/files/contentblock/2011/06/03/y1-ug-handbook-2019-2020-final-8october2019-45541.pdf
- Year 2: www2.physics.ox.ac.uk/sites/default/files/contentblock/2011/06/03/y2-ug-handbook-2019-2020-final-8-october2019-45542.pdf
- Year 3: www2.physics.ox.ac.uk/sites/default/files/contentblock/2011/06/03/y3-ug-handbook-2019-2020-updated-21november2019-45955.pdf
- Year 4: www2.physics.ox.ac.uk/sites/default/files/contentblock/2011/06/03/y4-ug-handbook-2019-2020-final-8october2019-45544.pdf
At the time of the experiment, Illumina equipment was cheaper per base pair and dominates the human genome sequencing market, but it required a much higher initial investment for the equipment (TODO how much).
The reusable Nanopore device costs just about 500 dollars, and about 500 dollars (50 unit volume) for the single usage flow cell which can decode up to 30 billion base pairs, which is about 10 human genomes 1x! Note that 1x is basically useless for one of the most important of all applications of sequencing: detection of single-nucleotide polymorphisms, since the error rate would be too high to base clinical decisions on.
Compare that to Illumina which is currently doing about an 1000 dollar human genome at 30x, and a bit less errors per base pair (TODO how much).
Other advantages of the MinION over Illumina which didn't really matter to this particular experiment are:
- portability for e.g. to do analysis on the field near infections outbreaks. Compare that to the smallest Illumina sequencer currently available in 2019, the iSeq 100: Figure 1. "Illumina iSeq 100 DNA sequencer".
- long reads which can be necessary for long repetitive regions, see also: Section "Sequence alignment"
There are unlisted articles, also show them or only show them.