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For how long must light be emitted for a human eye to perceive it?

• Would a person notice a flash of light that lasted 10 ms?
• Does the intensity of the light matter?
• How much light is a photon, anyway? Does is take thousands or trillions of photons interacting with the eye to register as light?

1am where I live and I'm wondering

I think Category Theory is really interesting in the way it frames the human endeavor of trying to understand and map phenomena out and then reason about it, but it is a super abstract thing by design... but the thought came to me that the deluge of modern board game designs with many that are carefully designed to have complex interactions and mechanics might be a place that the utility of Category Theory could be explained in an approachable way (at least to board game nerds...) that also demonstrated the basic utility of it as a way to examine different complex systems and compare them in some logically precise way.

https://en.wikipedia.org/wiki/Category_theory

To put it succinctly, could we look at Dominion and examine whether other Deckbuilding games are Isomorphic or are in some sense fundamentally similar or dissimilar in some way that isn't just qualitative? Certainly we can say that a "Bag builder" like Orléans or Quacks Of Quedlinburg can be equivalent mechanically to a Deckbuilder but what about more nuanced less obvious questions of similarity?

https://boardgamegeek.com/boardgame/36218/dominion

https://boardgamegeek.com/boardgamemechanic/2664/deck-bag-and-pool-building

It seems to me it would give a language to talking analytically about game design, it could express things like whether you could tweak a Dominion game with certain market cards to approximate the same mechanics as another Deckbuilding game or whether there are fundamental differences between Dominion and the other Deckbuilder that preclude that and if so how precisely so does that manifest?

I realize Category Theory isn't quite Science... but it certainly represents a scientific approach to representing how we categorize and analyze the universe so in that sense... I don't know it felt right to ask it here... but I can re-post on a math community if it doesn't fit here if wanted?

https://www.math3ma.com/blog/what-is-category-theory-anyway

Don't know if this is the correct community to ask this question but here goes.

I am a physics/math major and I am fascinated by computers. I want to work on a field that deals with cutting edge computer hardware (sort of like how ssd was in the age of hdd). But most of the research seems to be on stuff that will be used by corporations (not affordable for common people).

Does anyone have any idea what field is closest to what I'm looking for?

I would also like us [email protected] to be a partner community with you guys and gals. I was told to message Sabbah but no answer so would put it to the community

I was looking at the reply to this survey map:

complainig humans don't live in the ocean. Which lead me to the question of how large of a radius around every person you would have to color, tracing all their movements for their entire life, to color in the entire earth.

Naturally, this radius would have to be set such that the most remote point across time is just barely covered. So what would that point be, and how far away has every human been from it for all of time?

I assume this would be somewhere in antarctica, or maybe in the pacific? With a radius of surely not more than a few tens of kilometers, right? Maybe even less?

I would say let's, since we obviously wanna count ships, also count planes and subs. But let's not count astronauts.

Some clarifications:

• This is all on a map, height does not matter. Walking somewhere or flying over it is the same.
• We are talking absolutely noone has been closer than an absolute distance. If a single person has travelled there, the location is out.

In 'The Three Body Problem', we see a prominent scholar and professor being publicly beaten by the communist party for not denying God's existence. He goes on to say that 'Science hasn't provided any definitive answer'. So I'm curious, .

So, if you research the history of space exploration, you'll find one result keeps happening over and over and over and over.

They keep exploding.

It's not surprising. Their basic foundation is that they are rockets. Even from their original designs, rockets have always been built with the purpose of exploding. They're weapons. But, before they were weapons, the ORIGINAL idea, was to use the propulsion to exit Earths atmosphere and into space. The only problem is that when this was being designed, I forget the guys name, but he was a scientist that the nazis had captured. He designed the rockets for space craft. Hitler then took the designs and thought "Let's blow up London!"

So, once the war was over, the United States came over, and recruited him into NASA. His designs were how NASA got started. Modified versions of his original designs are what Apollo 11 used to get to the moon. So, the design CAN work. However, there were 10 Apollo missions before that didn't reach the moon. The first one ended disastrously.

The Challenger shuttle ended in disaster.

Even though they aren't NASA, recently in the past month Elon Musk's SpaceX had an explosion. Jeff Bezos also had a rocket explode. So this is still an issue.

And I always wondered, what would happen if you just took a commercial jet, and flew above the clouds? Well, they DO fly above the clouds. So what would happen if you just kept going "up"?

And I'm sure you can't just grab a stock Delta Airlines 747 and fly into orbit, but why not design a space craft, which more resembles the take-off of an airplane? Drives forward really fast, and then lifts? Except it's not flying NYC to LA. It just keeps lifting and lifting, until it's in orbit.

You could put thrusters on it to go forward in space. And then for landings, you wouldn't drop off into the ocean. You'd just land at an airport. The crazy thing is, the people of NASA are so talented, that they could route the whole thing, in a way that they land at whichever airport they want. So they'd know ahead of time NOT to schedule any landings or takeoffs for this 3 hour period of time when the space craft lands.

And I bet with enough time, they could get the experience to reduce that 3 hours, into 15 minutes. Knowing exactly when they'll arrive. Also no more of this breakaway pods that fall back to earth after detatching, or the other ones which just float out in space forever.

But I'm sure I can't be the only one with this idea, so I figure the most likely is that it's a scientific restriction. Where they can't do it, because......and this is where the explanation would be.

Anyone know the explanation?

heat death of the universe

do you believe in it? more importantly, if yes/no, what's the reason why / why not?

i have had a great number of very enjoyable discussions with people about this topic. some say that it is unknowable what the eventual fate of the universe will be, because we can never have experimental confirmation that things will keep on moving forever, unless we wait for the end of the universe, which will never come (or at which point the knowledge would be useless).

however, i keep thinking that cosmic expansion will lift things out of a gravitational potential over time. i'm assuming that we're all inside a big black hole (the whole universe is a black hole as an object with the mass of the entire observable universe just so happens to have a schwarzschild diameter of about the diameter of the entire observable universe). as the universe expands, its density decreases, therefore its schwarzschild radius decreases and we will eventually leave the black hole without doing anything for it; this obviously adds energy to the system.

or, in case cosmic expansion does not continue exponentially (but slows down over time), then the laws of physics would change over time; then, according to noether's theorem, we could extract useful energy out of that change of laws over time. also black holes could grow to infinite size simply feeding on cosmic microwave background radiation continuously in this case¹. which we could use as an energy source.

[1]: do the differential equation, you get dM/dt ∝ M²·u₀/a(t) where M is the mass of the black hole, M² is proportional to the surface area, a(t) is the scale factor, and u₀ is the CMB density at current time. If a(t) is less than exponential, i.e. less than exp(Ht), then M(t) diverges in finite time for any black hole with big enough start mass.

sorry for such a verbose post :)

Also since a Black Hole sucks 90% of it's surroundings into it, what about time distillation? Does time cease to exist inside a black hole or does black hole pull time apart too?

Occasionally you read in the news that parasite x, plant y or animal z has been found in country abc which shouldn't be the case and causes problems.

This is often a result of the ongoing climate change, increasing travel and global trade that allows many species to enter into new regions.

Because of the lack of natural predators or competitors, these new species can become locally dominant and replace established species.

My questions: what is the end game?

Will global biodiversity decline significantly to a few "core" species that are flexible in multiple climate zones or environment?

Or will the native species adapt or evolve further?

cross-posted from: https://lemmy.blahaj.zone/post/43972162

I'm guessing;

• space flight so cheap that a normal person could buy and use a space vehicle for less than the cost of a house
• space freight

Does each "buzz" give a different effect? How does the brain know which part to let the serotonin into to get a specific high? Like is there the same "buzz" between lets say alcohol, coke, heroin, gambling, cigarettes, weed or painkillers? How does your brain know how to let loose the "high" part? How does a alcoholic different from a alcoholic or gambling addict? Is there like a thin line that runs through all addictions? And this is why so many fall under the very vague umbrella of just addicts?? Can explain more if need be.

I am trying to mathematical model a passive Magnetorheological damper. Broadly speaking, this would work by having a magnet sit on the damper shaft near the damper body. As the shaft moves, it would induce an eddy current in the damper body, creating a magnetic field. Not only would this magnetic field oppose the magnet's motion, but it would increase the viscosity of the magnetorheological fluid inside the damper body. On paper, this would rapidly increase the damping forces with increasing shaft speeds, allowing for more controlled shaft speed.

Fortunately, I found a paper discussing a damper similar to my ideas. Unfortunately, I don't really understand the math, and I need the damping force equation in terms of velocity to validate the application I have in mind. Linked is the paper I am referring to.

For my purposes, I would also want to model separate traditional high and low speed compression and rebound circuits moving through traditional mechanical damping circuits, along with some other damping features. However, that's a problem for future FedX, right now I really just care about the broad differences in damping characteristics as a function of shaft velocity.

If needed I will try to explain further.