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The empirical fact of short winter days and long winter nights has been known essentially forever, and has driven enormous amounts of human activity including the construction of monuments like the passage tomb at Newgrange that I keep banging on about in previous posts about timekeeping. The correct explanation of the phenomenon has only been understood for around 400 years, dating back to Johannes Kepler’s description of the orbits of the planets.

The change in the relative length of days and nights is due to a combination of the motion of the Earth about the Sun, and the rotation of the Earth on its axis. Specifically, it happens because the Earth’s axis is tilted by about 23 degrees relative to the axis of its orbit. And because angular momentum is conserved, that axis stays pointing in the same direction through the whole orbit, in the same way that a gyroscope on a gimbal mount will remain pointed in the same direction in space as it’s moved around.

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The bus that takes my 10-year-old to school picks him up at around 7:23 am, but he usually starts fidgeting loudly a good ten minutes before that, so he and I will go outside to wait. In recent weeks, between grumbles about particular classes or the recess monitor who won’t let him go outside in shorts and a T-shirt in 40-degree (F) weather, he’s been asking “Why is it so dark?” The answer, of course, is “astrophysics,” but with a side order of theology and politics.

This Tuesday, December 21, is the winter solstice in the Northern Hemisphere, meaning it’s the shortest day of the year. It’s not the earliest sunset (that was a couple of weeks ago) or the latest sunrise (that’s in early January), but it’s the day with the fewest hours between sunrise and sunset.

The end of the year is a time not just for predictions of top trends but also to watch for the biggest hype and most misleading recommendations that get dished out to business leaders. There’s no scarcity of these in the artificial intelligence (AI) space.

As AI evolves, its influence on humanity continues to rise. People often focus on AI’s ability to automate and amplify tasks but underestimate its more profound impact on society. “Very few human creations have had the kind of impact as AI,” says Loomis. He compares it with the invention of language—a “tool” that has changed the trajectory of humans and helped birth civilizations. Today, we are still taking baby steps with AI. However, unlike early humans, we are waking up to the fact that AI is not just a tool but will weave deeper into our society.

“I hope 2022 will be the start of this realization, where we don’t just create new technical practices for AI but also understand how it shapes us. This should alert us to the fact that this is the time to lay the guardrails—the checks and balances needed to guide this change into something greater and not dystopian,” concludes Loomis.

Here’s what you need to know.


The James Webb Space Telescope (JWST, or Webb for short) is scheduled to launch on December 24, 2021, at 7:20 Eastern Standard Time.

It will blast off from French Guiana aboard an Ariane 5 ECA rocket, headed for an orbit around the second Lagrange point, or L2, where the gravitational pull of Earth is equal to the gravitational pull of the Sun.

Webb’s launch has to be carefully timed to put the telescope on the right path. It needs to leave Earth when our planet’s axis is tilted in the right direction, and when the launch site is pointed toward the right area of space. In other words, the James Webb Space Telescope launch has to happen during the right season and at the right time of day. On launch day, those requirements allow just a 30-minute window in which Webb will have to launch — or it will have to wait for another day.

The James Webb Space Telescope is confirmed for the target launch date of December 24, at 7:20 a.m. EST.

Late on December 17, teams at the launch site successfully completed encapsulation of the observatory inside the Ariane 5 rocket that will launch it to space. Webb’s final launch readiness review will be held on Tuesday, December 21 and, if successful, roll-out is planned for Wednesday, December 22.

We suggest an interpretation of quantum mechanics, inspired by the ideas of Aharonov et al. of a time-symmetric description of quantum theory. We show that a special final boundary condition for the Universe, may be consistently defined as to determine single classical-like measurement outcomes, thus solving the “measurement problem”. No other deviation is made from standard quantum mechanics, and the resulting theory is deterministic (in a two-time sense) and local. Quantum mechanical probabilities are recovered in general, but are eliminated from the description of any single measurement. We call this the Two-time interpretation of quantum mechanics. We analyze ideal measurements, showing how the quantum superposition is, in effect, dynamically reduced to a single classical state via a “two-time decoherence” process.

It’s often said Earth’s resources are finite. This is true enough. But shift your gaze skyward for a moment. Up there, amid the stars, lurks an invisible bonanza of epic proportions.

Many of the materials upon which modern civilization is built exist in far greater amounts throughout the rest of the solar system. Earth, after all, was formed from the same cosmic cloud as all the other planets, comets, and asteroids—and it hardly cornered the market when it comes to the valuable materials we use to make smartphone batteries or raise skyscrapers.

A recent study puts it in perspective.


Earth’s resources are finite, but shift your gaze skyward for a moment. Up there, amid the stars, lurks an invisible bonanza of epic proportions.