Peter Todd's hash collision puzzles Updated +Created
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:
printf 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 | xxd -r -p | sha1sum
printf 255044462d312e330a25e2e3cfd30a0a0a312030206f626a0a3c3c2f57696474682032203020522f4865696768742033203020522f547970652034203020522f537562747970652035203020522f46696c7465722036203020522f436f6c6f7253706163652037203020522f4c656e6774682038203020522f42697473506572436f6d706f6e656e7420383e3e0a73747265616d0affd8fffe00245348412d3120697320646561642121212121852fec092339759c39b1a1c63c4c97e1fffe017346dc9166b67e118f029ab621b2560ff9ca67cca8c7f85ba84c79030c2b3de218f86db3a90901d5df45c14f26fedfb3dc38e96ac22fe7bd728f0e45bce046d23c570feb141398bb552ef5a0a82be331fea48037b8b5d71f0e332edf93ac3500eb4ddc0decc1a864790c782c76215660dd309791d06bd0af3f98cda4bc4629b1 | xxd -r -p | sha1sum
both giving
f92d74e3874587aaf443d1db961d4e26dde13e9c
It was claimed on the same day that Google disclosed the collision: security.googleblog.com/2017/02/announcing-first-sha1-collision.html
Both of these are PDF prefixes, so they start with the PDF file signature, but are not fully viewable PDFs on their own.
The Oxford Scientist Updated +Created
Omics Updated +Created
Each of the omics studies a subset of molecular biology with a data intensive and broad point of view that tries to understand global function or organisms, trying to understand what every biologically relevant molecule does as part of the hole metabolism.
Omics might be stamp collecting, but maybe it is a bit more like Trading card game/Magic: The Gathering collecting, in which the cards that you are collecting actually have specific uses and interactions, especially considering that most metabolic pathways are analogous across many species.
Figure 1.
Hierarchical diagram of the major omics
.
Photon field Updated +Created
Anonymity Updated +Created
Protocols are the biologist term for "recipe".
I found that a lot of biology comes down to this: get the right recipe, follow it well even though you don't understand all the proprietary details, and pray.
Oxford Physics student course notes Updated +Created
Photon polarization Updated +Created
The knowledge that light is polarized precedes the knowledge of the existence of the photon, see polarization of light for the classical point of view.
The polarization state and how it can be decomposed into different modes can be well visualized with the Poincaré sphere.
One key idea about photon polarization is that it carries angular momentum. Therefore, when an electron changes orbitals in the Schrödinger equation solution for the hydrogen atom, the angular momentum (as well as energy) change is carried out by the polarization of the photon!
Video 1.
Quantum Mechanics 9b - Photon Spin and Schrodinger's Cat II by ViaScience (2013)
Source.
Physics course of the University of Oxford Updated +Created
From the 2020/2021 Oxford physics course handbooks we can determine the following structure:
Trinity term, the third and final term of each year, contains mostly revision from the previous two terms, after which students take their final exams, which basically account for their entire grade. Trinity is therefore a very tense part of the year for the students. After that they have summer holidays, until coming back for the next year of madness.
The official external course landing page: www.ox.ac.uk/admissions/undergraduate/courses/course-listing/physics. 2021 archive: web.archive.org/web/20221208212856/https://www.ox.ac.uk/admissions/undergraduate/courses/course-listing/physics) In those pages we see the rough structure, except that it does not have the course codes "A1" etc., and some courses are missing.
At web.archive.org/web/20221229021312/https://www2.physics.ox.ac.uk/sites/default/files/2011-06-03/course_v3_pdf_80151.pdf page 11 we can see the global course structure giving the two options, 3 year BA or 4 year Oxford physics masters:
Year 1
(Prelims)
|
|
v
Year 2
(Part A)
|
+-----------+
|           |
v           v
Year 3 BA   Year 3 (MPhys)
(Part B)    (Part B)
|           |
|           |
v           v
BA          Year 4
            (Part C)
            |
            |
            v
            MPhys
Practical courses notes: www-teaching.physics.ox.ac.uk/
Physics from Symmetry by Jakob Schwichtenberg (2015) Updated +Created
This is a good book. It is rather short, very direct, which is a good thing. At some points it is slightly too direct, but to a large extent it gets it right.
The main goal of the book is to basically to build the Standard Model Lagrangian from only initial symmetry considerations, notably the Poincaré group + internal symmetries.
The book doesn't really show how to extract numbers from that Lagrangian, but perhaps that can be pardoned, do one thing and do it well.
Pin header Updated +Created
These often come pre-soldered on devboards, e.g. and allow for easy access to GPIO pins. E.g. they're present on the Raspberry Pi 2.
Why would someone ever sell a devboard without them pre-soldered!
Figure 2.
Underside of a Raspberry Pi 2
. Source. At the top of this image we can clearly see how the usually pre-soldered pin header connectors go through the PCB and are soldered on both sides.
Enrico Fermi Updated +Created
Died of cancer at age 53. Ciro Santilli just can't help but speculate that it is linked to radioactivity exposure.
Paleolithic Updated +Created
This period is similar to the Quaternary, but it also includes tool usage by close relatives of humans which were not humans yet.
It ends together with the pleistocene.
Parameters of the Standard Model Updated +Created
The growing number of parameters of the Standard Model is one big source of worry for early 21st century physics, much like the growing number of particles was a worry in the beginning of the 20th (but that one was solved by 2020).
If it ain't broke, don't fix it Updated +Created
b-money Updated +Created
Penalty kick left right Nash equilibrium Updated +Created
When taking a penalty kick in soccer, the kicker must chose left or right.
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
Personal finance Updated +Created
  • the American stock market gives 10% / year, which is about 2x over 10 years. It has been the sure-fire best investment on a 10 year horizon for many decades, and should serve as your benchmark.
  • risky diversified investments (e.g. ETFs that track a market index) are basically the best investment if you can keep your money in them in the long term (10 years)
  • risky investments can gown down for a while, and you cannot take your money out then. This effectively means risk is a form of illiquidity
  • investment funds have taxes, which eat into your profit. The best investments are dumb index tracking investments (like an ETF that tracks the stock market) that are simply brainless to manage, and therefore have lowest taxes. No fund has managed to beat the market long term essentially.
  • when you are young, ideally you should invest everything into riskier higher yielding assets like stock. And as you get older, you should move part of it to less risky (and therefore more liquid, but lower yielding) assets like bonds
    The desire to buy a house however complicates this for many people.
Planned obsolescence Updated +Created
The first time Ciro Santilli Googled this was when trying to repair his cell phone.
2019 cell phones are glued together with adhesive, which makes them impossible to repair them unless you have a heat gun, spend hours and hours learning and planning, and accept the risk of breaking the screen
If you take a phone less than 300 dollars to a repair shop in the first world, they will say: I've never repaired this crap, and likely for the price of the repair you should just buy a new one, and so to the trash goes the old one, polluting the planet, and in comes a new one, enriching the manufacturer further.

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