Hello everyone!

I've recently got an idea for a Database as a Service I'd like to create. The only issue is - I don't know how to create or host a database!

I've only ever used Mongoose/mLab with Javascript, and a minimal amount of Postgres with Python.

If I'm looking to create a database that will, eventually, be able to store images, songs, and videos, where should I start my homework?

I can create the backend and the frontend with no issue - just stuck on this part here. If it's of any relevance, I most frequently use the MERN stack.

Technically I'm late again, but it's still Friday somewhere right?

How do?

Since we're currently lacking native spoiler tags, I'd ask all of you to follow this scheme:
Post a top level comment with the title and episode number of the anime you want to talk about like this
**JoJo's Bizarre Adventure: Vento Aureo - Episode 1**
Then reply to those top level comments with your thoughts. This way people who haven't seen something yet or plan on binge watching once all the episodes are out can simply collapase the top level comment to not get spoiled ^.^

What do?

Simply post, discuss or joke about any currently airing anime you want. For Anime you've been watching that aren't currently airing refer to Cleb's weekly thread.

When do?

But what if the anime I want to talk about hasn't aired yet?

No problem, just post a comment here once the episode has aired, these threads aren't meant to last one single day.

Archive

Archives of these threads can be found at the unofficial wiki

I might soon be part of an internet startup. We're talking with a relative about setting up a consultancy & business news service on a certain sector, and I've generated a part of the idea and accepted to take on the technical/editorial side for a while (I've almost a year til when I start my master's, and will probably work up until when I start my thesis; so almost two years). If things work out, this might be a dream job (except academia) for me, and even very lucrative. But I'm fairly n00b in this space, both business and professional work, though I have the technical skills. Thus I'm seeking general advice on

• how to organise this thing: how to make sure we communicate well on dates and plans and how to make educated guesses when setting up an agenda

• how much will it cost: we'll start with making a database and running a sector-specific blog/news site as publicity (though I'll make sure the content is quite decent, not just a showpiece), but then later we'll introduce a tangential online service and a mobile app leveraging that crowd

• working with non-techies: I'll be the only techie in this startup and I need to help people with gathering, storing, organising and utilising historical data with certain variables, ensuring they keep an accurate record and can make quality queries easily; the 3 people apart from me will be non technical

I think quite a bit of you here have been involved in this sort of scenario, so maybe you could have some advice for me. I'd appreciate anything, examples of approaches, links to tools, what not, anything you think could be useful. Thanks a lot in advance!

Hey Tildes, I got a job directly supervising a small team of 4 software developers. I'm very excited at the prospect and would like to put my best foot forward. To that end, I would like to have a discussion around a few topics. Feel free to expand the scope if you believe the conversation would be beneficial. I'm sure I won't be the last person to be in this position. I've done research, read, and watched videos regarding several of these questions; however, since Tilde prioritizes high-quality discussion, I thought it would be a fun opportunity to chat with others about these topics.

• As a member of a software development team, what are things that your supervisor has done that has had the greatest (a) positive and (b) negative impact?
• Supervisors, when you joined your new team, what was your methodology for reviewing the team, projects, and processes? What was the scenarios behind your review and the outcome? What would you do differently?

I'd really like to have a DNA test done to know my family history beyond 2 generations (adopted relatives)

I've heard numerous times that 23andme will abuse the information they obtain and either target you with ads or sell your DNA to marketing agencies, are there any non invasive DNA tests available online or elsewhere?

I am super happy right now.

For the past few years, I've taken on so many futile projects, dead ends, I've ripped things to shreds because I stopped liking them. Finally though, I am content with one of my creations and hit 100 pages, already reworked and refined! :)

Sorry, but I'm super happy at the moment.

I recently got into lock picking as a hobby. It's really fun and the community is very kind and open and supportive.

But it's a hobby I'm hesitant to share with others. There's a huge stigma with lockpicking and I feel I have to be careful who I tell. Do any of you have hobbies that you don't share with others?

For those who've not heard of it, the scp wiki is a community-based collaborative writing effort based around "anomalous" objects/beings and the efforts of the SCP Foundation to contain them and protect the general public. Users can submit and vote on articles about SCPs, written in the style of research/containment notes. Some popular entries are SCP-173, SCP-87 and SCP-682, alongside a few more abstract and lighter entries.

Anyone want to share some SCP entries they've enjoyed reading? SCP-3515 is the most recent I've read and I'd definitely recommend it.

Last week I didn't realize I hadn't made the weekly post until it was a couple days too late, so I decided to just rollover to this week. Sorry, folks. Might have to get someone else to post sometimes.

Anyway, what have you been watching/reading this week?

Feel free to talk about something you saw that was cool, something that was bad, ask for recommendations, or anything else you can think of.

If you want to, feel free to find the thing you're talking about and link to its Anilist, MAL, or any other anime/manga database you use!

EDIT: With the help of @ducks the post now has illustrations to clear up the experimental set-up.

Introduction

I want to give an introduction on several physics topics at a level understandable to laypeople (high school level physics background). Making physics accessible to laypeople is a much discussed topic at universities. It can be very hard to translate the professional terms into a language understandable by people outside the field. So I will take this opportunity to challenge myself to (hopefully) create an understandable introduction to interesting topics in modern physics. To this end, I will take liberties in explaining things, and not always go for full scientific accuracy, while hopefully still getting the core concepts across. If a more in-depth explanation is wanted, please ask in the comments and I will do my best to answer.

Previous topics

Spintronics
Quantum Oscillations
Quantisation and spin, part 1

Today's topic

Today's topic will be a continuation of the topics discussed in my last post. So if you haven't, please read part 1 first (see link above). We will be sending particles through two Stern-Gerlach apparatuses and then we'll put the particles through three of them. We will discuss our observations and draw some very interesting conclusions from it on the quantum nature of our universe. Not bad for a single experiment that can be performed easily!

Rotating the Stern-Gerlach apparatus

We will start simple and rotate the set-up of the last post 90 degrees so that the magnets face left and right instead of up and down. Now let's think for a moment what we expect would happen if we sent silver atoms through this setup. Logically, there should not be in any difference in outcome if we rotate our experiment 90 degrees (neglecting gravity, whose strength is very low compared to the strength of the magnets). This is a core concept of physics, there are no "privileged" frames of reference in which the results would be more correct. So it is reasonable to assume that the atoms would split left and right in the same way they split up and down last time. This is indeed what happens when we perform the experiment. Great!

Two Stern-Gerlach apparatuses

Let's continue our discussion by chaining two Stern-Gerlach apparatuses together. The first apparatus will be oriented up-down, the second one left-right. We will be sending silver atoms with unknown spin through the first apparatus. As we learned in the previous post, this will cause them to separate into spin-up and spin-down states. Now we take only the spin-up silver atoms and send them into the second apparatus, which is rotated 90 degrees compared to the first one. Let's think for a moment what we expect would happen. It would be reasonable to assume that spin-left and spin-right would both appear 50% of the time, even if the silver atoms all have spin-up too. We don't really have a reason to assume a particle cannot both have spin up and spin right, or spin up and spin left. And indeed, once again we find a 50% split between spin-left and spin-right at the end of our second apparatus. Illustration here.

Three Stern-Gerlach apparatuses and a massive violation of common sense

So it would seem silver atoms have spin up or down as a property, and spin left or spin right as another property. Makes sense to me. To be sure, we take all the silver atoms that went up at the end of the first apparatus and right at the end of the second apparatus and send them through a third apparatus which is oriented up-down (so the same way as the first). Surely, all these atoms are spin-up so they will all come out up top again. We test this and find... a 50-50 split between up and down. Wait, what?

Remember that in the previous post I briefly mentioned that if you take two apparatuses who are both up-down oriented and send only the spin-up atoms through the second one they all come out up top again. So why now suddenly do they decide to split 50-50 again? We have to conclude that being forced to choose spin-left or spin-right causes the atoms to forget if they were spin-up or spin-down.

This result forces us to fundamentally reconsider how we describe the universe. We have to introduce the concepts of superposition and wave function collapse to be able to explain these results.

Superpositions, collapse and the meaning of observing in quantum physics

The way physicists make sense of the kind of behaviour described above is by saying the particles start out in a superposition; before the first experiment they are 50% in the up-state and 50% in the down-state at the same time. We can write this as 50%[spin up]+50%[spin down], and we call this a wave function. Once we send the particles through the first Stern-Gerlach apparatus each one will be forced to choose to exhibit spin-up or spin-down behaviour. At this point they are said to undergo (wave function) collapse; they are now in either the 100%[spin up] or 100%[spin down] state. This is the meaning of observing in quantum mechanics, once we interact with a property of an atom (or any particle, or even a cat) that is in a superposition this superposition is forced to collapse into a single definite state, in this case the property spin is in a superposition and upon observing is forced to collapse to spin up or spin down.

However, once we send our particles through the second apparatus, they are forced to collapse into 100%[spin left] or 100%[spin right]. As we saw above, this somehow also makes them go back into the 50%[spin up]+50%[spin down] state. The particles cannot collapse into both a definite [spin up] or [spin down] state and a definite [spin left] or [spin right] state. Knowing one precludes knowing the other. An illustration can be seen here.

This has far reaching consequences for how knowable our universe it. Even if we can perfectly describe the universe and everything in it, we still cannot know such simple things as whether a silver atom will go left or right in a magnetic field - if we know it would go up or down. It's not just that we aren't good enough at measuring, it's fundamentally unknowable. Our universe is inherently random.

Conclusion

In these two posts we have broken the laws of classical physics and were forced to create a whole new theory to describe how our universe works. We found out our universe is unknowable and inherently random. Even if we could know all the information of the state our universe is in right now, we still would not be able to track perfectly how our universe would evolve, due to the inherent chance that is baked into it.

Next time

Well that was quite mind-blowing. Next time I might discuss fermions vs bosons, two types of particles that classify all (normal) matter in the universe and that have wildly different properties. But first @ducks will take over this series for a few posts and talk about classical physics and engineering.

Feedback

As always, please feel free to ask for clarification and give me feedback on which parts of the post could me made clearer. Feel free to discuss the implications for humanity to exist in a universe that is inherently random and unknowable.

Addendum

Observant readers might argue that in this particular case we could just as well have described spin as a simple property that will align itself to the magnets. However, we find the same type of behaviour happens with angles other than 90 degrees. Say the second apparatus is at an angle phi to the first apparatus, then the chance of the particles deflecting one way is cos^2(phi/2)[up] and sin^2(phi/2)[down]. So even if there's only a 1 degree difference between the two apparatuses, there's still a chance that the spin will come out 89 degrees rotated rather than 1 degree rotated.