🎓 Dr. Freemo 🇳🇱 @freemo@social.cleverlibre.org

@noellabo I guess im the only one on qoto following you? shame, i need to sing your praises more clearly.

@khird yea to me the n-k term is just a sort of expansion and not really a relevant part of the steps.. in fact I find the formula itself to be more verbose than it really needs to be and my own approach is just one logical step to expanding to the formula, and a step that isnt really even needed IMO... In short my formula just skips the first math step you need when using the real formula, but once you understand my formula the original is fairly trivial to recall IMO

@khird @khird ahh in that case ill explain. I find my method much simpler than yours but i think we tend to find our own personal methods easiest so that may not mean much... but maybe you will do and int he future it will be easier to recall if so...

So lets take a simplified version of the above "how many combinations of 6 numbers can I pick from 99"...

First I ask myself "How many permutations of 6 can I pick from 99 numbers". This is easy to remember since the first number there are 99 ways, second 98 etc.. so it is 99 * 98 * 97 * 96 * 95 * 94.. I can simplify this as 99!/93!

Next I reason that a combination doesnt care about order, so if i have any particular set of 6 numbers (being a set they are naturally unique) how many permuations can i make out of those 6 numbers... for that we have simple 6!.

Finally I know that out of all the permutations from my earlier selection of 99!/93! numbers any one unique set of 6 numbers has 6! possible variations it can exist as within those permutations. so I like wise know that I can divide 99!/93! by 6! and arrive at the number of combinations...

So (99!/93!)/6! = 99!/(6! * 93!)

Q.E.D. Solution derived.

@khird its interesting to read by the way because its kinda the exact same logic I use but almost the exact opposite. I think of it in terms of permutations and all the combinations of permutations possible... similar idea as yours but from the other end.

@khird excellent contribution thank you. I agree this is very helpful to anyone reading.

@math

In case anyone is curious as to how to do some elementary statistics, in this case combinatorics, here is a quick little write up I did to explain the "n choose k" paradigm.

Here is the is the question (from my cousin):

> Math people
Can you help me ??
Let's say
Hypothetically
You have 7 numbers
Between 1-99
The first 6 cant repeat but the 7th can
How many outcomes are possible?
This isnt a riddle or anything I just dont know how to do the math on something I'm trying to figure out

Here is my answer:

http://mathb.in/47715

#Statistics #Math #mathematics #Stats #Science #Learning

@ravenclaw

hhehehe :) your a nicer person than I am. I might catch a case of diabeetus if this keeps up :)

You are most welcome.

@arxiv_physics

@ravenclaw

Honestly, i'd imagine quite a few people at spacex would use the term "light" to specifically and exclusively mean visible light, at least in casual conversation.

Typically one needs to infer if they use light to mean visible light or all light.

So its really not a hard mistake to make and can just as easily say its my own fault for not being more explicit, even if the technical definition of light is not just the visible spectrum.

@Science

@ravenclaw

He is one of our only bots (other than the users bot). so he wont reply. He only posts once a day at this time when new papers are released on arxiv :)

@arxiv_physics

@ravenclaw

No problem, it is a common mistake. Its just it if we take light to mean only visible light (as is sometimes the case) the entire logic breaks down, as you already pointed out :) So glad we could set that back on track.

@Science

@ravenclaw

In physics light refers to electromagnetic radiation of any wavelength. While it is typical for people to think of light as just the part we see the truth is infrared, down to near-dc and ultraviolet on up to gamma rays and beyond is all light.

Heat , or in this case since its radiated heat we really mean "heat transfer" takes three forms, well technically 4 but the fourth one is kinda obvious and i wouldnt say really counts.. those are

Convection : the flow of a gas or fluid, such as hot air rising, that causes the heat to move along with the medium that is moving that contains it.

Conduction: The movement of heat through direct physical contact. For example if you hold onto a metal rod and heat one end eventually the end your holding will also get too hot to hold.

Advection: this one is a cheat, lets ignore it, but its where you pick up something hot and put it somewhere else.

Radiation: This this is where an object gives off its heat as Infrared light. If you sit in front of a camp fire on a cold day and feel its warmth, the vast majority of that warmth is from the IR light of the fire.

Now we are ignoring advection for the obvious reasons. As for convection, well the inside of a lightbulb is a vacuum, so there is no air to allow for convection of heat off of the filament (where the heat is being generated). Conduction makes a little bit of sense as there is a physical path from the filimat to the base of the light bulb. But because it is a very thin long metal wire that has very little contact with the filament the effects of this are negligable.

That leaves us with just radiation... Therefore when we talk about a light bulb then any heat it produces, is heat in the form of light. So saying most of the energy goes to heat and not light isnt correct, heat **is** light. but you would be correct if you said that the portion of light given off as heat is not **visible** light :)

@Science

@ravenclaw Absolutely understandable.. sometimes another persons perspective, particularly when describing their internal mental state, can seem quite alien.

@ravenclaw

Well no, but depends what you mean by that... the question is "What percentage of light ... is visible"

While normally luminosity is all radiated energy and thus inclusive of non visible light it would not be correct to say "The luminosity of the visible light portion of the radiation is 100%", it is not and it is significantly less than that In fact the way the question is worded the answer in percentage of luminosity of the visible light would be the same as the correct answer. Luminosity is, in fact, inferred by the wording of the question.

@Science

@ravenclaw

well to be fair LED based lights, while still not anywhere near 100%, are many many orders of magnitude more efficient.

@Science

@ravenclaw Not everyone is the same, or even similar of course. Nor is the nature of ones "episode".. I suppose there is a different sort of unhealthy that i could potentially get into from time to time, where I enjoy silence just a bit too much. This would be the sort of mentality where my productivity is very low... it is rare for me though.

@2ck To me the isolation isnt a bad thing, I condense all my people time into a few days here and there and teh rest I am more than happy to be alone. Aside from a small number of people I generally dont find being around people as enjoyable as the activities I can do alone.

Then again that me be in part because of the somewhat obscure interests I have. It would be hard to find someone who shares my interests and as such it is rare I can do anything with a group I find as exciting as the things I would do alone.

@Science

What percentage of the light given off by a 50W incandescent light bulb is in the visible range?

#Science #physics

@Demosthenes Ive been on adderall a few months now, usually i dont need it as my ADHD tends to be more of a strength than a weakness. However I went on it in part to help with weight loss and a few other things. It helps me with things that arent really typical ADHD problems or what you would expect (for example I have a sleep problem and it helps a lot with that).

With that said while most of the effects of the medication are good it does have some negative side effects too. One of which is that its hard to turn my mind off, and be at ease with the silence. Without medication I probably go too far the other direction, I'll take a little extra time sitting around doing nothing just enjoying the silence than I should, but now I dont feel I can do that very easily.