Stop codon Updated 2025-07-16
Twin paradox Updated 2025-07-16
The key question is: why is this not symmetrical?
One answer is: because one of the twin accelerates, and therefore changes inertial frames.
But the better answer is: understand what happens when the stationary twin sends light signals at constant time intervals to each other. When does the travelling twin receives them?
Another way of understanding it is: you have to make all calculations on a single inertial frame for the entire trip.
Supposing the sibling quickly accelerates out (or magically starts moving at constant speed), travels at constant speed, and quickly accelerates back, and travels at constant speed setup, there are three frames that seem reasonable:
- the frame of the non-accelerating sibling
- the outgoing trip of the accelerating sibling
- the return trip of the accelerating sibling
If you do that, all three calculations give the exact same result, which is reassuring.
Another way to understand it is to do explicit integrations of the acceleration: physics.stackexchange.com/questions/242043/what-is-the-proper-way-to-explain-the-twin-paradox/242044#242044 This is the least insightful however :-)
Bibliography:
Twin prime conjecture Updated 2025-07-16
Let's show them how it's done with primes + awk. Edit. They have a gives us the list of all twin primes up to 100:Tested on Ubuntu 22.10.
-d option which also shows gaps!!! Too strong:sudo apt install bsdgames
primes -d 1 100 | awk '/\(2\)/{print $1 - 2, $1 }'0 2
3 5
5 7
11 13
17 19
29 31
41 43
59 61
71 73 TwinsUK Updated 2025-07-16
Blood cell Updated 2025-07-16
CC BY-NC-ND Updated 2025-07-16
CC BY-SA 4.0 Updated 2025-07-16
CC BY version Updated 2025-07-16
Chinese semiconductor industry Updated 2025-07-16
Ciro Santilli's hardware Seagate ST1000LM035-1RK1 1TB hard disk Updated 2025-07-16
1TB.
www.disctech.com/Seagate-ST1000LM035-1TB-SATA-Hard-Drive 80 USD | web.archive.org/web/20181224201408/https://www.disctech.com/Seagate-ST1000LM035-1TB-SATA-Hard-Drive
www.seagate.com/www-content/datasheets/pdfs/mobile-hddDS1861-2-1603-en_US.pdf | web.archive.org/web/20181225095438/https://www.seagate.com/www-content/datasheets/pdfs/mobile-hddDS1861-2-1603-en_US.pdf
sudo hdparm -Tt /dev/sda3 on Ubuntu 20.04: Nature (journal) Updated 2025-07-16
Two photon interference experiment Updated 2025-07-16
Can be achieved in two ways it seems:
- macroscopic beam splitter and optical table
- photolithography
Animation of Hong-Ou-Mandel Effect on a silicon like structure by Quantum Light University of Sheffield (2014): www.youtube.com/watch?v=ld2r2IMt4vg No maths, but gives the result clear: the photons are always on the same side.
- quantum dot source. TODO how do you produce identical photons from two separate quantum dots? See also: quantum dot single photon source.
- superconducting nanowire detector. So the device has to be cooled then? Video "Jeremy O'Brien: "Quantum Technologies" by GoogleTechTalks (2014)" youtube.com/watch?v=7wCBkAQYBZA&t=2497 however says that semiconducting devices can also be used
Typeface Updated 2025-07-16
Fairchild Semiconductor Updated 2025-07-16
Some nice insights at: Robert Noyce: The Man Behind the Microchip by Leslie Berlin (2006).
GNU Core Utils Updated 2025-07-16
Imperative programming Updated 2025-07-16
List of command line utilities Updated 2025-07-16
Ouroboros (protocol) Updated 2025-07-16
POSIX command line utility Updated 2025-07-16
There are unlisted articles, also show them or only show them.