My brain very often likes to ask questions in the dumbest way possible so I'm sorry if this question doesn't make sense. And I'll try to explain what I mean by existence. I'm talking about existence as a thing having form. Even if it's shape is subject to change it still maintains a form. So to go back to the question, do black holes have a form like a solid, liquid, or gas. Or, is it the absence of form. Like the concept of non-existence manifesting and deleting the idea of form? Sorry if most of this reads like gibberish.

Don't get my question wrong, I have a lot of respect for science and the enormous work it has put into exploring our reality.

However, I see that the further we go, the more difficulties we encounter, and these difficulties seem not just ones for which we lack certain means, but logically insurmountable. It seems that we will never understand the very moment of the beginning of the universe, and even more so what happened before it, if there was anything before it at all. We are unlikely to see what is inside black holes, because to do this we must literally go there and leave the entire universe in the past, providing ourselves with only one future - movement towards its center; besides, you most likely will not exist. We are unlikely to know exactly what the size and shape of the universe is, especially if it is infinite, simply because we cannot and will not be able to leave the limits of the observable one, and the list goes on.

I certainly understand that people have said the same thing many times before, and it is quite fair to object by saying that, for example, we used to have no idea why lightning strikes or that the earth is round; however, human, like nature itself, has some limits. We are at a certain level due to our size, intelligence, physical abilities and so on, and from this level we will not be able to look at scales that are too small or too large anyway, because they may be unattainable from our level; the same is probably true even for AI, because it has similar limits, even though in many ways it is better than us. Yes, so far we have managed to cope with many things, but this is only for the reason and in those things where nature allows us to do so, and I don't think that it is a puzzle specially made for human to solve it.

What is your opinion on this?

Say I want a satellite that's 24x365 right over a specific city. Directly above the city, just at 400 km height.

Can it do that? Stay at the same spot and just move along earth's rotation speed, keeping it in the same small area it needs to be in?

Electromagnetic launchers (coilguns or railguns) use extremely high amperages and voltages, but I was wondering if are there very high voltage very low amperage electromagnetic/electrostatic launchers.

The only thing I could find was electrostatic linear motors, but they are very simple science demonstrators and nothing that powerful.

The only reason I find the idea interesting is because of the downsides of conventional electromagnetic launchers, they heat too much due to the insane amperage and in the case of a railgun, they self-destroy easily.
While very high voltage very low amperage currents can travel through materials with very high conductivity with almost no loss.

Older scientists sometimes recount using unconventional methods that seem bizarre by today's standards. For example, smoking in the lab to detect trace cyanide gas. Does anyone have other quirky anecdotes to share about outdated scientific practices from back in the day? Curious to hear these fascinating stories!

If it were possible, would it make sense to re-start construction on the Super-Conducting Super-Collider given a theoretical maximum of 20TeV and the LHCs max of 14?

I’m genuinely curious why there is people who can catch HIV easily and others can be with many many people and never get the virus? Is it just by luck, or is their immune systems strong? Is it possible more people may be immune to HIV than we think?

What is the shortest plausible incubation period for any kind of pathogen (viral, bacterial, fungal ect) between exposure and becoming symptomatic? In other words how long would it realistically take for someone to get sick after being exposed if said pathogen made one sick as quickly as biologically possible.

I'm writing a science fiction setting that takes place on earth 1000 years in the future. In this future climate, earth has warmed enough that the poles are temperate/tropical and most of the rest of the planet is simply too hot for humans to survive in.
There's several new civilizations clustered around the northern latitudes. I realized that during those 1000 years of heat, possibly ALL the permafrost under those regions would melt away. Wikipedia tells me that:
"This base depth of permafrost can vary wildly – it is less than a meter (3 ft) in the areas where it is shallowest, yet reaches 1,493 m (4,898 ft) in the northern Lena and Yana River basins in Siberia."
and that permafrost thaw can create new wetlands and drain old ones. I know about toxic plumes and ground instability, but what I want to try to imagine is what would a region with very deep permafrost (like 500m+ deep) look like if ALL that permafrost melted? would the region become gigantic inland lakes? Extensive wetlands? What do you think?
BONUS QUESTION:
I found this nice make of where the permafrost is in the northern hemisphere, but I wish I could find a map of the Base Depth of the all the permafrost. Does this kind of data even exist?

I recently watched the latest Kurzgesagt video about the mass extinction which wiped out the dinosaurs on Youtube and it briefly mentions that holes in the ozone layer contributed to the break down of ecosystems directly exposed to the suns rays due to the lose of the ozone layers protection.

Then I started wondering how this would affect a modern human village, town, etc. So my question is:

If I’m in a room (with and without window) in my house and I’m in an area which is in the target range of high doses of the suns radiation waves due to a hole in the ozone layer how long would it take for it to affect me and what damage would it do to me/my house/garden?

I recently saw a post on “plastivores”, but I’m a little confused about what that actually means beyond the usual titles saying they’re a possible solution for micro plastics (so I’m trying to find more information for myself). According to some articles I’ve read, the organisms that are able to break down plastics are compared to “starved” organisms, and do not lose weight, but do not gain it. Does this mean they only ingest plastic when no other food is available? Are these “plastivores” actually gaining energy from plastics, or does this mean their bodies are just further breaking down the plastics and they can survive off them if no other food source is available? I’m just a layperson who wants to know more from actual scientific sources and appreciate any and all of your responses! Also if I should post this elsewhere, please let me know and I’ll do so!

I asked this question in a comment on a related post, but decided to expand on it.

I'm not a physicist, and I'm not aware of the exact formulae used to explain the behavior of black holes (nor would I likely understand them), so forgive me if this comes off as naive.

We know that "nothing" escapes from inside a black hole, including information. We also know that when something "falls" into a black hole, from our frame of reference it seems it just gets stuck near the event horizon, ever slowlier fading out and becoming redshifted.

What doesn't make sense to me is the very creation of a singularity. How does the matter needed for the singularity to be created ever reach the point of to-be singularity?

For practical purposes, lets say that for something to "exist" in a frame of reference, it means that information about its existence can reach the observer in that frame, specifically us, i.e. the space outside of black hole. I know that gravity doesn't have to escape a black hole for it to affect surrounding matter, as it is an effect of curved space-time, but AFAIK the *change* of space-time curvature does travel at the speed of causality, and is affected by a black hole just like any other information. Hypothetically, if a true singularity spontaneously appeared somewhere with non-zero mass, information about its existence couldn't reach the surrounding space-time, and it would effectively erase itself from existence. However, in the real world, things don't magically appear with existing properties, but they grow/form over time. Since the time dilation slows down the events happening near the event horizon, we would at best forever receive information about the "core" of a black hole just before the black hole actually forms, and space-time would never "adjust" to a singularity, but just a really dense "similar" object. Theoretically, the object would eternally be becoming more and more similar to a black hole as it becomes denser, but for both the space-time and an observer, they would never see an actual black hole.

The way I imagine this, as the matter becomes dense enough in some point, the event horizon grows from that point into a bigger and bigger sphere, as it swallows more and more matter that was close by.

*However*, As an unfinished event horizon forms between two particles that are coming closer and closer, it should also cause a time dilation effect that would prevent the particles from ever reaching the event horizon that they are themselves creating. The same applies to all other matter that is "supposed" to form a black hole. In other words, it would take infinite time for a "true" black hole to form. However, I assume that due to tidal forces, the matter that is "trying" to form the black hole would start evaporating (in the form of photons I guess), and since the photons never actually crossed the event horizon, they would over finite time escape. Since the energy escapes the point of creation of singularity, the event horizon would eventually start shrinking down, and energy could escape faster and faster. In fact, all matter that "fell" towards the to-be "singularity" would escape in the form of very redshifted photons over possibly crazy long time.

We do have theories saying that black holes radiate energy and drain over really long time. Would this mean black holes are something akin to supernovae, just with a temporary time dilation bubble slowing the explosion down for a period of time?

I know this is very much against the general views on black holes in the scientific community, so could someone say what I got wrong? I probably did, but I can't see how the very idea of a singularity forming isn't paradoxical.

The original thread on which I asked the question: https://www.reddit.com/r/AskScienceDiscussion/comments/1boe0hb/comment/kwoni3y/

If I'm typing a familiar sentence on a keyboard via implicit memory , how much of my attention span, even if small, does this take up ?

There's been a lot of discussion about the ethics of climbing Mount Everest. I say we go scorched earth, and just get rid of it. It's an eyesore anyway.

But what would this take, and would it be possible? I'll separate it into the following scenarios

1. Level it down to the point where it matches the surrounding area (base camp)
2. Level it down to sea level

Also, would such an act permanently damage Nepal and the surrounding area?

I am outlining a book right now where the main characters are going to space in order to speed up the Earth's rotation after it has inexplicably slowed. I have read up a bit on moving the Moon as an option, or even using a pseudo conveyor belt with the Sun as the engine attached to the equator. I'm just wondering if there is any feasible way to speed Earth's rotation back to a 24 hour day without killing everyone or decimating the planet itself.

Would video be moving in slow motion?

That stuff has to go somewhere right? We wear tires down everyday so some of those little bits of rubber must go airborne and into our lungs.

So I understand that under our criteria for what is alive, viruses aren't included, but we didn't get this criteria from stone plates buried in the sand, we made them. It just seems so weird to me that the definition we created for what life is doesn't include viruses. surely an easier definition would just be something like (and I'm not an expert this is just an example) encased genetic material that has the ability to replicate itself either autonomously or via a host.

How foco pendulum is connected with the concept of coriolis force? Even though I get the fact that the earth rotates faster at equator as compare to poles but i don't get how all this connected with the pendulum...and also... Since we imagine foco pendulum as a system that's free to oscillate in any direction...how come it's a different system as compare to an aeroplane flying? Aeroplane flying is a relative motion... What is a relative motion and how it's different from motion like an object moving freely in the space?

It seems to me that it would be possible, yet I never hear about it so I suspect it is not.

Select eggs from partner A and partner B, and take a sperm from a sperm bank. Remove all chromosomes except for the Y chromosome from the sperm, and replace them with chromosomes from partner A's egg. Inject the resulting sperm cell into partner B's egg. Then proceed as though with a normal IVF procedure.

Could this be done with modern technology, and would it actually produce viable offspring? If not, why not?

Hey guys I am close to completing my PhD in optics / photonics in the UK (less than 6 months).

I am seeking some advice, specifically about career paths I could take, what career progression might look like, advice on how you got where you were and what you wish you knew when climbing the ladder...

Ideally I would like a job with good salary since I never really came from money. By this I mean simply going out for dinner or going to the shops to by some snacks and not have to think about the impact of my bank account.

I'm not entirely sure what I want to do after my PhD. Really I decided to do this PhD since I got an offer for a cool project after my undergraduate degree.

So any advice would be appreciated.

Hello, I have a concern that I'm hoping to resolve. There is a lot of debate in the aquarium hobby about nitrate and its toxicity to fish. I believe the core of the issue is that scientific research measures nitrate in the form of NO3-N (nitrate-nitrogen), whereas test kits available to hobbyists measure NO3 (nitrate). The problem lies in the fact that hobbyists may not be aware that they need to convert NO3-N to NO3 by multiplying it by 4.4.

More too this, many studies measure toxicity using potassium nitrate. However, I've heard that most freshwater aquariums contain mostly sodium nitrate, which is supposedly less toxic. So, are hobbyists potentially overestimating the toxicity of nitrate in their aquariums because the scientific studies are using different measurement forms and substances?

Here is a link to a recent study for reference: https://www.researchgate.net/publication/370823598\_A\_critical\_review\_on\_the\_effect\_of\_nitrate\_pollution\_in\_aquatic\_invertebrates\_and\_fish

Thank you for any input you can provide!

Hygroscopic particles are used in cloud seeding usually with the aim of provoking rainfall (https://en.wikipedia.org/wiki/Cloud_seeding)

Are the particles used for this all heavier than air? Or are there some that are very light, even lighter than the gases of the atmosphere, so they would float like water vapour clouds indefinitely?

So I'm meaning like speed of sound and/higher. From my understanding objects going really fast form at least partial pockets of air so dense it gets superheated to plasma. Say it's shaped like a missile and maintains a jacket on at least the front facing surfaces. You have two aim straight for each other. Unless exactly hitting dead center would the jacket deflect them away without physically touching? Ignoring the stresses of deflection because yea at that speed mjolnr would prolly crack too

Hello everyone, I'm currently in the last semester of my B.Sc (Zoology Honours). I'm planning to apply for a Masters program and one of them includes MSc in Freshwater Ecology. This field is quite new to me as I've only heard of Marine Biology. I wanted to know what job opportunities and research fields I can get into if I continue my Masters in this particular field. I would like to pursue a PhD Degree/Program in the future so I want to know if it will be a good idea to take up Freshwater as a masters program and if it will be easy to get into a PhD program in this field. I'm really clueless and would appreciate any advice you may give. I'm also open to doing research work overseas so you are doing any work in this field please do let me know.

(I apologize for any grammatical errors since English isn't my first language)

Hey everyone,

So, very ignorant question here. In the models for Black Holes that are prevalent, the models seem to show the accretion disks being a "ring" around the Black Holes, not as a "Sphere" around the Black Hole.

Are these illustrations of Black Holes having a "ring" around them how theyre meant to be interpreted?

Or are they simplifying it to show the concept of the accretion disk, but the "disk" is actually a Sphere of Energy and Mass that actually encompasses the Black Hole?

Very ignorant question, I know... but its been something Ive been curious about for awhile... and if it is just a "Ring" around the Black Hole.. Why is that? Shouldnt the gravitational pull of the Black Hole go in 360 degrees around it?

Why the focus of mass and energy into a Ring pattern, as opposed to a sphere of fire and energy around the Event Horizon?

Thank you for your time and for reading my super ignorant question! Cheers