LillyPip

Excess oxygen is actually harmful to humans, ~~but all the climate warnings are about losing oxygen, not nitrogen~~ edit: but when we look for habitable planets, our focus is ‘oxygen rich atmosphere’, not ‘nitrogen rich’, and in medical settings, we’re always concerned about low oxygen, not nitrogen.

Deep sea divers also use a nitrogen mix (nitrox) to stay alive and help prevent the bends, so nitrogen seems pretty important.

It seems weird that our main focus is oxygen when our main air intake is nitrogen. What am I missing?

edit: my climate example was poor and I think misleading. Added a better example instead.

In the movies, time travelers typically step inside a machine and—poof—disappear. They then reappear instantaneously among cowboys, knights or dinosaurs. What these films show is basically time teleportation.

Scientists don’t think this conception is likely in the real world, but they also don’t relegate time travel to the crackpot realm. In fact, the laws of physics might allow chronological hopping, but the devil is in the details.

[…]

If a person were to hang out near the edge of a black hole, where gravity is prodigious, Goldberg says, only a few hours might pass for them while 1,000 years went by for someone on Earth. If the person who was near the black hole returned to this planet, they would have effectively traveled to the future. “That is a real effect,” he says. “That is completely uncontroversial.”

Going backward in time gets thorny, though (thornier than getting ripped to shreds inside a black hole). Scientists have come up with a few ways it might be possible, and they have been aware of time travel paradoxes in general relativity for decades. Fabio Costa, a physicist at the Nordic Institute for Theoretical Physics, notes that an early solution with time travel began with a scenario written in the 1920s. That idea involved massive long cylinder that spun fast in the manner of straw rolled between your palms and that twisted spacetime along with it. The understanding that this object could act as a time machine allowing one to travel to the past only happened in the 1970s, a few decades after scientists had discovered a phenomenon called “closed timelike curves.”

“A closed timelike curve describes the trajectory of a hypothetical observer that, while always traveling forward in time from their own perspective, at some point finds themselves at the same place and time where they started, creating a loop,” Costa says. “This is possible in a region of spacetime that, warped by gravity, loops into itself.”

“Einstein read about closed timelike curves and was very disturbed by this idea,” he adds. The phenomenon nevertheless spurred later research.

Science began to take time travel seriously in the 1980s. In 1990, for instance, Russian physicist Igor Novikov and American physicist Kip Thorne collaborated on a research paper about closed time-like curves. “They started to study not only how one could try to build a time machine but also how it would work,” Costa says.

[Article continues…]

This is very strange and I’m sorry for multiple issues in one day, but I just switched to my inbox and it’s all someone else’s account.

I’m @lillypip but my inbox currently shows someone else’s account. I won’t post it here, but I have screenshots if a Voyager Dev wants to see them.

I think I can reply to people from there (the buttons seem to work, but I won’t do it for obvious reasons).

Not sure if this is a Voyager or Lemmy issue, but it’s very seriously weirding me out.

e: it’s not even the same server. My account is on lemmy.ca and my inbox is someoneelse@kbin.social (not the actual account, obviously).

e2: my inbox isn’t that person’s inbox, it’s their outbox. All the content is from them, not to them. I’ve never interacted with this person to my knowledge.

e3: I was wrong: I HAVE interacted with them. A few hours ago, I messaged them to say a link they commented was broken. I didn’t recognise the name until I tried to message them as recommended in the comments here. I can’t message them now; it just hangs.

e4: restarting the app didn’t help, but rebooting my phone fixed it. Maybe it was a caching issue? Like I said, it was showing what was in their public profile (comments and posts), perhaps my inbox was stuck showing that? Anyway, it’s fixed now, so it seems like a caching issue, probably?

I’ve only noticed this in the past few days. Not sure if it’s a new issue, but I feel I wasn’t getting this before last week. (Eta: I’m on the latest update) Most Lemmy image links in comments are doing this now.

Sorry if it’s been posted already; I tried searching and didn’t see anything.

Thank you for all your hard work – I LOVE Voyager! ❤️

Becoming an astronaut is a fairly romanticized career path, but there are a lot of less-than-romantic aspects to working 50 miles or more above the Earth’s surface. Case in point: just being in zero G makes the human body do all sorts of embarrassing things.

A new story from the New York Times exhaustedly points out that living in space comes with all sorts of “bodily indignities” which should give even the most eager potential space explorer pause. It turns out, it’s not just deadly radiation or muscle loss due to weightlessness astronauts traveling to spots in our own solar system will have to put with:

In microgravity, however, the blood volume above your neck will most likely still be too high, at least for a while. This can affect the eyes and optic nerves, sometimes causing permanent vision problems for astronauts who stay in space for months, a condition called spaceflight-associated neuro-ocular syndrome. It also causes fluid to accumulate in nearby tissues, giving you a puffy face and congested sinuses. As with a bad cold, the process inhibits nerve endings in the nasal passages, meaning you can’t smell or taste very well. (The nose plays an important role in taste.) The I.S.S. galley is often stocked with wasabi and hot sauce.

These sensory deficits can be helpful in some respects, though, because the I.S.S. tends to smell like body odor or farts. You can’t shower, and microgravity prevents digestive gases from rising out of the stew of other juices in your stomach and intestines, making it hard to belch without barfing. Because the gas must exit somehow, the frequency and volume (metric and decibel) of flatulence increases.

Other metabolic processes are similarly disturbed. Urine adheres to the bladder wall rather than collecting at the base, where the growing pressure of liquid above the urethra usually alerts us when the organ is two-thirds full. “Thus, the bladder may reach maximum capacity before an urge is felt, at which point urination may happen suddenly and spontaneously,” according to “A Review of Challenges & Opportunities: Variable and Partial Gravity for Human Habitats in L.E.O.,” or low Earth orbit. This is a report that came out last year from the authors Ronke Olabisi, an associate professor of biomedical engineering at the University of California, Irvine, and Mae Jemison, a retired NASA astronaut. Sometimes the bladder fills but doesn’t empty, and astronauts need to catheterize themselves.

Link to NYT article (paywalled)

Link to study paper: Nonclassical Advantage in Metrology Established via Quantum Simulations of Hypothetical Closed Timelike Curves

Abstract:

We construct a metrology experiment in which the metrologist can sometimes amend the input state by simulating a closed timelike curve, a worldline that travels backward in time. The existence of closed timelike curves is hypothetical. Nevertheless, they can be simulated probabilistically by quantum-teleportation circuits. We leverage such simulations to pinpoint a counterintuitive nonclassical advantage achievable with entanglement. Our experiment echoes a common information-processing task: A metrologist must prepare probes to input into an unknown quantum interaction. The goal is to infer as much information per probe as possible. If the input is optimal, the information gained per probe can exceed any value achievable classically. The problem is that, only after the interaction does the metrologist learn which input would have been optimal. The metrologist can attempt to change the input by effectively teleporting the optimal input back in time, via entanglement manipulation. The effective time travel sometimes fails but ensures that, summed over trials, the metrologist’s winnings are positive. Our Gedankenexperiment demonstrates that entanglement can generate operational advantages forbidden in classical chronology-respecting theories.

Physicists have shown that simulating models of hypothetical time travel can solve experimental problems that appear impossible to solve using standard physics.

We are not proposing a time travel machine, but rather a deep dive into the fundamentals of quantum mechanics. – David Arvidsson-Shukur

Link with more horsestaches.

I’ve searched every way I can think of and can’t find anything.

I remember it played a nursery rhyme like a music box when both armrests were gripped.

That’s my sister and I visiting my great-grandmother in her infirmary in *1975. The chair wasn’t meant for visitors, but for children housed in the infirmary.

The chair had metal armrests that acted like actuators, and a metal box under the seat that played nursery rhyme songs like a music box when both armrests were gripped and the chair rocked.

Was this a common thing, perhaps mass-produced, or just something jerry-rigged by some guy?

Have you seen anything like this? Thanks!

(Sorry for reposting; my post went wrong last time.)