^^Interesting. Seems pretty ambitious, but then again if you asked people in 1970 about that I'd imagine they would say we'd easily have that stuff by 2020.

The smallest gravitational force yet has been measured!

https://www.nature.com/articles/s41586-021-03250-7

Love this type of article and what it means for the odd's of life on other planets that we might have considered in hospitable simply because the conditions for our earth ecosystem to thrive are not present.

The Horta could indeed be a thing on some planet.



The Bizarre Beasts living in Romania's Poison Cave

Movile Cave has been cut off for millions of years. Its air is thick with harmful gases, yet it is home to an array of strange animals.


...a cave that has remained isolated for 5.5 million years. While our ape-like ancestors were coming down from the trees and evolving into modern humans, the inhabitants of this cave were cut off from the rest of the planet.

Despite a complete absence of light and a poisonous atmosphere, the cave is crawling with life. There are unique spiders, scorpions, woodlice and centipedes, many never before seen by humans, and all of them owe their lives to a strange floating mat of bacteria...

..."The pool of warm, sulphidic water stinks of rotting eggs or burnt rubber when you disturb it as hydrogen sulphide is given off."

In the lake room, the atmosphere is heavy with harmful gases, principally carbon dioxide as well as the hydrogen sulphide from the water. What's more, the air is low in oxygen: it contains just 10% oxygen rather than the usual 20%...

Despite the dark and the dangerous gases, Movile Cave is crawling with life. So far 48 species have been identified, including 33 found nowhere else in the world.

There are all sorts of scuttling and slithering things. Snails and shrimps try to avoid the spiders and waterscorpions. In the air bells, leeches swim across the water and prey on earthworms.

Strangely, the worse the air gets the more animals there are. It's not at all obvious why that should be, or how the animals survive at all.

On the surface, plants use sunlight to extract carbon dioxide from the air and turn it into organic compounds. They can then use these chemicals to grow leaves, roots and bulbs. Animals then feed on these plant tissues.

Without sunlight, the animals in Movile Cave seem to be without a source of food.

In most caves, animals get their food from the water dripping down from the surface. This water can often be seen in the form of stalactites and stalagmites.

However, Movile Cave has a thick layer of clay above it, which is impermeable to water. When Lascu first visited, he could not find any stalactites or stalagmites, or any other sign of water coming from the surface.

The mystery deepened when scientists analysed the water in the cave for radioactive caesium and strontium. The 1986 nuclear accident at Chernobyl had released lots of these metals, which had found their way into the soils and lakes surrounding Movile Cave. However, a 1996 study found no traces of them inside the cave.

That means the water isn't coming from above, so it must be coming from below. It now seems that the water in Movile Cave comes from spongy sandstones where it has lain for 25,000 years.

However, this still doesn't explain how the animals in the cave survive. Tests have shown that the water flowing in does not contain any food particles.

Instead, the food comes from the strange frothy foam sitting on top of the water.

This floating film, which looks like wet tissue paper and can even be torn like paper, contains millions upon millions of bacteria known as "autotrophs".

"These bacteria get their carbon from carbon dioxide just like plants do," says Boden. "The carbon dioxide level in the cave is about 100 times higher than normal air. But unlike plants, they obviously can't use photosynthesis as there is no light."

Rather than using light as an energy source, the Movile bacteria use a process known as chemosynthesis.

"They get the energy needed… from chemical reactions: the key ones being the oxidation of sulphide and similar sulphur ions into sulphuric acid, or the oxidation of ammonium found in the groundwaters to nitrate," says Boden.

These chemosynthetic bacteria help explain why the cave is so large and the air is so thick with carbon dioxide.

"Sulphuric acid actually erodes the limestone, which is gradually making the cave bigger," says Boden. "The process releases carbon dioxide, which is why levels are so high."

Another major group of bacteria get their energy and carbon from the methane gas that bubbles up through the waters of the cave. They are called methanotrophs.

Boden describes methanotrophs as "messy eaters" that "constantly leak metabolic intermediates like methanol and formate" into the surrounding water. In turn, these chemicals are food for other species of bacteria.

This may all sound very peculiar, and in some ways it is. Movile is the only cave whose ecosystem is known to be supported in this way, and the only such ecosystem on land.

...The same cannot be said for the animals of the cave. Millions of years of isolation has transformed them.

Many are born without eyes, which would be useless in the dark. Almost all are translucent as they have lost pigment in their skin. Many also have extra-long appendages such as antennae to help them feel their way around in the darkness.

There are no flies in Movile Cave, but the spiders still spin webs. Small insects called springtails bounce into the air and get caught in the webs.

In 1996, researchers categorised the animals in the cave. They included 3 species of spider, a centipede, 4 species of isopod (the group that includes woodlice), a leech never seen anywhere else in the world, and an unusual-looking insect called a waterscorpion...

...The conditions in both places may well be similar to the primordial Earth. In our world's early years, the Sun's light was obscured by an atmosphere thick with carbon dioxide, methane and ammonia. It could be that the first living cells were similar to those found in Movile Cave.

Almost 30 years after its discovery, Movile Cave remains perhaps the most isolated ecosystem on the planet. It surely has many more secrets to give up. There are plenty more organisms buried in the cave's sediments, waiting to be identified, and they could help us understand some of our deepest questions about the nature of life.

Awesome story. I love reading about extremophiles in general. So many assumptions about life have been challenged in recent years because of extremophile discoveries.

How Godel's Incompleteness Theorems Work

Pretty good explanation. Uses a slightly simplified version of Godel numbering a little different from what Godel himself did, which makes it easier to follow without sacrificing too much.

IMO the main issue with explaining Godel's theorems to the unfamiliar is that it seems completely unremarkable/obvious in a high level natural language like English. That English allows for statements that have no proof like

is hardly surprising because English allows allows you to talk about a town in which a barber only shaves everybody who doesn't shave themselves or even how many angels fit on a pin head.

So to really get it's significance in more formal settings you have to understand Godel's Completeness Theorem. Which, off the bat, causes confusion because it sounds like it contradicts the incompleteness theorems. But that's simply somewhat poor terminology, complete in the completeness theorem refers to something different than complete in the incompleteness theorems.

The article somewhat sidesteps this, but just sort of stating the conclusion of the completeness theorem, that any proof can be expressed formally as a string of mathematical symbols. But does better than most popular level discussions in that it at least touches on Godel numbering. It's sometimes hard to tell a good popular level intro for something you already understand, but I think the article is pretty decent.

Take that Trumpkins!

Particle physics types have been waiting for a while for data from Fermilabs muon g-2 experiments. There are some hints of beyond the standard model physics, but probably just a need to do better calculations within the standard model and get more data.

A good popular level write up

https://www.quantamagazine.org/muon-...cles-20210407/

Interesting, perhaps the standard model will become the phlogiston of our time.

I had to look up phlogiston.... but perhaps? The standard model is in many ways one of a kind though. It was never meant to last this long. I believe Weinberg coined the term in the late 60s as a temporary place holder for the gauge theory plus Higgs mechanism techniques they were using for electroweak theory. I think he said later that he would have picked a much better name if he knew it was going to be the gold standard theory for 50+ years.

Bill Gates supports project to cool Earth with 'chalk dust'


A large balloon will be launched shortly in Sweden that will spew particles of calcium carbonate, which is essentially "chalk dust" in order to dim the sunlight.


The “ Controlled Stratospheric Perturbation Experiment ” (SCoPEx) wants to prove that the release of this dust into the stratosphere could eventually divert some of the sun's energy and lower the temperatures of our planet.

The balloon will be launched near the Arctic city of Kiruna, and it would be the first serious attempt to test whether global warming can be kept under control by dimming the sunlight...

..."SCoPEx is a scientific experiment to advance the understanding of stratospheric aerosols that could be relevant for solar geoengineering,"...

...Scientific opponents of this project believe that solar geoengineering could bring imperative risks and extreme changes in weather patterns that would be no different than current warming trends.


On the other hand, environmentalists fear that a "dramatic" change in mitigation strategy will become a "green light" for greenhouse gases to continue to be emitted without any variation in current consumption patterns.

Looking at Bill I suspect an ulterior motive.



Edit. Cite. Some experts who think this is a bad, bad idea. Big budget apocalypse movie bad.

Just a basic logic puzzle for anybody bored.

List all the binary truth functions

I'll give you 3 obvious ones to start, and as examples in case it's not clear what "binary truth function" means.

P AND Q: (True if both P and Q are True, False otherwise)
P OR Q: (False if both P and Q are False, True otherwise)
P--> Q: (False if P is True and Q is false, True otherwise)

Hint in spoiler

IIRC everything in boolean logic can be implemented with NAND or NOR gates, so I guess the answer is 1?

It's true that all binary truth functions can be built with just NAND (or NOR) gates, but that's not the same thing has saying NAND is the only binary truth function. If I just gave you just 1 NAND gate, all you can do is express NAND (or NAND and AND if ~ is allowed). But you have expanded the list to 5 now

Answer in spoilers

Good Job!

I've actually asked this in interviews before.

In SQL server, you have a number of basic aggregation functions - COUNT, SUM, MIN, MAX, AVG, STDEV. These operate on columns - so much like an aggregation function in a "Total" row in Excel. You obviously also have access to the full complement of standard mathematical operations at row level, i.e. operations that have access to the values on the current row.

With that in mind, how would you construct a "PRODUCT" aggregator, i.e. an aggregate function which computes the product of the column on which it is operating?

In other words, if you needed a product in a "Total" row in Excel but no "PRODUCT" function, how would you make one? You are allowed to create extra "helper" columns on each row.

Hint:

Bang on I've asked that when interviewing for fairly senior positions at least three times, and not a single candidate came close.

Not to rain on the uber nerdgasm going on now but to add a little bit more fun...


Boba Fett eat your heart out.



Jet pack flight for the adventuresome at heart in about about 1 more years worth refining. For the masses within 3 years??

Awesome!

Yeah, if you hadn't mentioned excel I probably wouldn't have even thought about it and just assumed you needed to know SQL to answer.

Just in case you missed it.



NASA’s Ingenuity helicopter lifts off of Mars




It was not your average remote-controlled drone flight. A few hours ago, in the middle of martian daytime, Ingenuity, NASA’s $80 million small helicopter, furiously spun its rotors, rose in the air and hovered. It rotated and took a picture before alighting once again on the surface. The modest flight, lasting less than 1 minute, represents a major milestone: the first controlled flight of a powered aircraft on another planet...

...Although the photos will be a nice perk, the goal of the helicopter test is to obtain engineering data that will be used to build larger, more ambitious helicopters for operation on Mars, Aung said in a briefing before the test. Ingenuity has four more flights left before Perseverance departs on its primary scientific mission to collect rock samples for return to Earth. Four days from now, the second flight should rise to 5 meters, and the one after that will be longer in time. The final two flights will be more ambitious, with the last one likely traveling outside the flat, safe “airfield” the team has mapped out, Aung said. “We will really want to push our vehicle to the limit.”

But even if it was modest, Ingenuity’s first flight will be one for the record books, Aung added. “Each world,” she said, “only gets one first flight.”