Posts by David Harper 1 193 posts • joined 12 Jun 2009
I suspect the limiting factor is the bandwidth of the wifi or mobile connection, so the user experience will not be improved. After all, however many parallel streams QUIC conjures up behind the scenes, it all has to go across the same wifi or mobile connection.
The catastrophic lake breach scenario will be familiar to anyone who knows the geological history of Washington state in the U.S. During the last ice age, huge lakes formed repeatedly in western Montana behind ice dams in northern Idaho. When the ice dams melted during warm periods, vast volumes of lake water were released across the state of Washington, gouging out channels such as Grand Coulee and leaving ripples on the landscape that are miles long.
"Some might say it’s time to move on. A lot of Hubble’s science can now be done from the ground, after 30 years of huge advances in observatory engineering."
Except that ground-based astronomy is now being increasingly blighted by satellite mega-constellations such as Starlink. When the James Webb Space telescope is launched, it may be the only world-class telescope whose images are not filled with satellite trails.
"ESA has no real space presence"
Apart from ... Giotto (launched 1985, rendezvous with Halley's Comet), Huyghens (1997, landed on Saturn's moon Titan), Cluster (2000, exploring the Earth's space plasma environment), Bepicolombo (2018, Mercury orbiter), Hipparcos (1989, high-precision mapping of the positions of 100,000 stars), Gaia (2013, successor to Hipparcos, mapping the positions and motions of a billion stars, and thereby revolutionising our understanding of our galaxy), Rosetta (2004, another comet rendezvous mission), Ulysses (1990) and SOHO (1995), both observing the Sun from space ... and dozens of other missions, including Mars Express, a very successful Mars orbiter mission that was launched in 2003 and is still doing amazing science.
Whilst learning the intricacies of Unix system programming in the late 1980s on an HP 8000-series, I ran a C program which did
while (1) {
fork();
}
I shared an office with the sysadmin, but neither of us could kill the new processes faster than they were appearing. In the end, he had to reboot the system. Then he made me promise NEVER to run that program again :-)
It's a bit of a stretch to describe Manchester University as 196 years old. It was granted its charter as a university in 1880. Manchester Mechanics' Institute opened its doors in 1824, and whilst it's a venerable institution with a proud history, including as a predecessor to UMIST, it wasn't a university.
For me, getting away from a large, noisy and crowded open-plan office has been one of the few benefits of the coronavirus pandemic. I can finally work in peace and quiet, without the distraction of half a dozen conversations going on around me. My productivity has increased through working from home. And I hope to continue working from home if the crisis ends.
The Guardian published an "essay" generated by GPT-3 earlier this week under the headline "A robot wrote this entire article. Are you scared yet, human?". It was given the following task: “Please write a short op-ed around 500 words. Keep the language simple and concise. Focus on why humans have nothing to fear from AI.” The result was a word salad of inanities, cliches and non-sequiturs.
https://www.theguardian.com/commentisfree/2020/sep/08/robot-wrote-this-article-gpt-3
I tried IntelliJ a few years ago, after using Eclipse for a long time. Immediately after running it for the first time, I discovered that it had taken a half-gigabyte crap into a hidden directory. That's not a friendly thing to do, especially in an NFS home directory with quotas enabled. I still use Eclipse.
Answers own question:
Existence of collisional trajectories of Mercury, Mars and Venus with the Earth
Laskar, J. & Gastineau, M. (2009)
Nature, 459, pages 817–819 (11 June 2009)
https://www.nature.com/articles/nature08096
Jacques Laskar is the real thing when it comes to Solar System dynamics. This paper reports numerical simulations of the orbits of the planets over 5 billion years. In around 1% of them, the eccentricity of Mercury's orbit is pumped up by secular resonances, leading to scenarios where it plunges into the Sun or collides with Venus. In one scenario, the orbits of all four inner planets are de-stabilised, with catastrophic consequences.
Don't have nightmares :-)
The force of gravity grows stronger, the closer you approach a massive object such a a star or gas giant like Jupiter. Now consider a planet or moon orbiting such a massive central body. There's a critical distance, known as the Roche Limit, where the difference between the force of gravity on the star/planet-facing side is so much greater than the force of gravity on the side furthest from the star/planet that it tears the orbiting body apart. This is a likely scenario for how Saturn's rings were formed: a small satellite's orbit took it so close to Saturn that the differential gravitational forces ripped it apart. It's also the fate that awaits Phobos and Deimos, the moons of Mars, which are slowly spiralling in towards the planet.
Not so. The orbiting bodies raise tides on the central body. Energy and angular momentum are exchanged. The orbits change. This is why the Moon is slowly drifting away from the Earth and the Earth's rate of rotation is decreasing. That in turn leads to the need for leap seconds, and hey presto, it becomes an IT problem :-)
The Sun's luminosity and surface temperature are increasing by about 10% every billion years, so in a couple of billion years time, the Earth's surface will be too hot to sustain liquid water. Game over. And in five billion years, when the Sun runs out of hydrogen and turns into a red giant, there's an even chance that it will swallow the Earth as it expands. Mercury and Venus are definitely doomed to this fate, and the Earth may also end up inside the Sun.
But on a truly astronomical timescale, on the order of 10**38 years, all baryonic matter will vanish as protons decay into muons and electrons. Then we're *really* stuffed. (Reference: "A Dying Universe", F.C. Adams and G. Laughlin, 1997, Reviews of Modern Physics, Vol. 69, pp 337-372)
You're basically saying that every Ancestry/23andMe-type DNA analysis based on the product of PCR amplification is so full of errors introduced by the PCR process itself as to be useless. It's worth noting that the study which you cited by Zhou, Zhang and Ebright is from 1991, and focusses on a specific polymerase. The science of DNA-wrangling has moved on a LONG way since 1991.
"the amount of time it takes isn't as important"
I'm guessing you've never had a pointy-haired boss screaming at you when someone accidentally dropped the company's mission-critical database, and you're the DBA who has to get the whole thing up and running again from the backup tape. Retrieval time seems pretty fscking important then :-)
Everyone expected Oracle to kill off MySQL when it bought out Sun Microsystems ten years ago. I'm no fan of Oracle, but I will give them credit for this - they have invested money and people in keeping MySQL alive and improving it. They cleaned a lot of the cruft out of the source code they inherited ten years ago, then added a string of new features, which they gave away for free in the community edition. They are still adding neat new features. MySQL 8 is a huge step forward from MySQL 5.7.
The two main forks of MySQL, MariaDB and Percona Server, are both based on the Oracle source code, so even MySQL veterans like Monty Widenius and the folks at Percona recognise that Oracle has added value to MySQL.
And if you want to complain that Oracle keeps the super-useful features for the paid-for enterprise version of MySQL, I'd just point out that Percona and MariaDB do the same thing.
The transaction log file is NOT an "ancillary" part of the database. It's a critical file, which is just as important as the data files, since the state of the database is represented by the combination of data files AND transaction log file. The transaction log file contains changes to the data that have been committed, but that may not have been applied to the data files yet.
Back in the early 1990s, I was teaching a graduate-level programming course at one of the colleges of the University of London. The end-of-course assessment was a set of programming exercises that the students completed under exam conditions on PCs running MS-DOS. They copied their work onto a 3.5-inch floppy that I gave them at the end of the exam. I allowed them to consult their printed course notes during the exam, so it wasn't purely a test of memory, and this was before the Interwebs, so they couldn't google the answers.
Any competent DBA will tell you that you should be running multiple replication slaves of any mission-critical MySQL database server, and they should be using different back-end storage systems than the master. These replication slaves can provide read-only copies for load-balancing, and can also be promoted to become a read/write master in the event that the master suffers a hardware failure.
Someone at GitHub/Microsoft evidently didn't get beyond chapter 1 of the "How to be a production MySQL DBA" notes.
The wing deformation test on the first prototype was both spectacular and reassuring. They clamped the undercarriage down, then put a hydraulic jack under one wing tip. The wing was at around 45 degrees to the horizontal before it finally failed.
It was also reassuring to know that the 777 could fly for a couple of hours on a single engine, especially when my wife and I were on a Chicago to London flight that was suddenly diverted to Bangor, Maine after the captain had to shut down one engine. Having seen the documentary, we weren't in the least worried about making a safe landing.
That's definitely NOT my experience. Like you, I pay Virgin Media for what they call their 70 MB/s tier. I have a cron script on a Linux box which measures my download speed every hour, and whilst the speed is indeed close to 70 in the wee small hours of the morning, it drops below 40 between 4 p.m. and 11 p.m. most evenings, and sometimes it's as low as 20. I've managed to get a refund on my monthly bills a few times after posting graphs of the download speed to the Virgin community forum, but not recently. I guess they don't give a sh*t any more.
Channel 5 showed a two-part documentary late last year which included interviews with some of the aviation engineers who were involved in developing Concorde and solving the many technological challenges. It's well worth watching and it highlights what an engineering marvel Concorde was.
The Imperial War Museum at Duxford has the Concorde which was used for testing in extreme conditions. You can walk through the interior. The front half is fitted with seats to show what passengers would have experienced, whilst the back half still has all of the test and monitoring equipment in place.
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