/sqt/ - stupid questions thread

One of my friends is one of those 'flat earthers', and we often debate about it. His latest quarrel is that
1. a spaceships hull should be turn to shreds in space (vacuum)
2. the sun's radiation is wavelengths and since space has no atoms, the wavelengths should not be able to travel.

How do I debate this? I was reading up on photons but I don't really understand it.

>1. a spaceships hull should be turn to shreds in space (vacuum)
Why?

>2. the sun's radiation is wavelengths and since space has no atoms, the wavelengths should not be able to travel.
That is not how photons work. This confusion was a major topic in the physics research of the early 1900s, and it's kinda complicated, but the upshot is that photons are NOT like waves in a pond that rely on a carrier material (in this case, water).

Does mommy know your on the PC?

>your
Does you're mummy know?

1. Vacuum = extremely low density. As such he argues that matter in outerspace should be ripped apart and spread evenly, just as it would on earth. If part of earth's lower atmosphere becomes lower or higher, it corrects itself (that's what wind is from). Ever tried to suck air out of a bottle?

2. Radiation travels through vibrating atoms/molecules at certain frequencies and amplitudes. How does it travel through space?

NASA has a vacuum chamber and it isn't ripped apart

I have a penis that is 100 inches long. If you give me a couple billion dollars I could prove it to you with photos and a cheap video

So I'm taking general relativity next semester.

What am I in for? How difficult can it be?

>Vacuum = extremely low density. As such he argues that matter in outerspace should be ripped apart and spread evenly, just as it would on earth.
A strong rigid container can sustain different pressures on the inside and the outside. A typical submarine, which has a very strong hull, keeps its internal pressure at 1 bar, and can dive to a depth with an outside pressure of some 50 bar; if it goes deeper than that, the pressure difference will crush the sub. A spaceship would have an inside pressure of 1 bar, and an outside pressure of 0 bar (vacuum), which is very tame in comparison with the sub (only 1 bar of pressure difference instead of 50 bar). Even aircraft at cruising heights have only 0.25 bar of outside pressure (air pressure is substantially lower at that height) and 1 bar inside pressure, meaning they could almost-if-not-quite sustain the pressure difference of a spaceship.

If you shake a coke bottle, it will build up an internal pressure of over 3 bar (which is why it will spray in your face if you open it carelessly). You'll note that the coke bottle does not explode, with an internal pressure of 3 bar and an outside pressure of 1 bar (sea level atmospheric pressure), and thus 2 bar of pressure difference. The spaceship in the vacuum of space has only 1 bar of pressure difference, meaning it could sustain it even when built to the strength of a coke bottle.

>Radiation travels through vibrating atoms/molecules at certain frequencies and amplitudes.
Not really. Radiation travels through space; when it hits an atom, it gets absorbed, and then possibly-but-not-necessarily re-emitted. That's what causes phenomena like refraction.

but 0 bar is infinitely less pressure then 1, to the point where it would utterly consume and tear about any matter that enters it. And pressure and density IS what determines temperature. Apart from completely decompressing and pulling apart a spaceship, it should evaporate it too while it distributes the pressure (and density) among space.

2. Radiation doesn't get absorbed by an atom. Radiation IS wavelengths, It isn't a physical entity, it is the MOVEMENT of atoms.

What is the best basic math teacher online outside of khanacademy?

>but 0 bar is infinitely less pressure then 1, to the point where it would utterly consume and tear about any matter that enters it.
No, it isn't.

A fluid (gas or liquid) at a certain pressure in an enclose applies a certain force to the enclosure. This force is proportional to the amount of pressure. When there are pressures on two sides of an enclosure, the inverse forces on the enclosure cancel out, and what's left over is the force of the difference between the pressures.

This is a *difference*, not a ratio or something. If there is 20 bar of pressure outside a coke bottle and 21 bar inside it, that's just the same as 10 bar outside and 11 bar inside, or 0 bar (vacuum) outside and 1 bar inside. In all cases, the pressure difference on the bottle is 1 bar, and if the container can sustain a 1 bar force without breaking in some way (exploding or rupturing when the inside pressure is greater than the outside pressure; imploding or rupturing when the outside pressure is greater), it's a situation that can sustain itself.

Where the vacuum part DOES matter is what happens when the enclosure DOES break. If a gas container has 21 bar internal pressure and 20 bar outside pressure, and the container ruptures, the resulting reaction will be far less violent than when the same thing happens to container with 1 bar internal pressure and 0 bar outside pressure. But this difference only comes into play when the enclosure breaks; as long as the enclosure is intact, 21:20 versus 1:0 are identical, in that the container has to sustain a 1 bar pressure difference.

>Radiation IS wavelengths, It isn't a physical entity, it is the MOVEMENT of atoms.
No. That is NOT what radiation is.

How do you get rid of social awkwardness, low self esteem, depression...

when I lay on my ear for a longer time(sleep) and then when i get up it's aching like hell. It doesnt hurt if i don't move, otherwise it's unbearable. I feel the pain only from outside the ear, like the cartilage in the ear is hurting. Why? Just stupidly grown nerves?

Has anyone ever used "Master the Content"? It's a website you pay for and it has resources to study for all board exams like MCAT, OAT, etc. It has full lectures, labs, and questions. I want to get t because I'm preparing for the MCAT and I'm not really liking the Kaplan books because they are too condensed Anyone have resources that are good for someone with a weak base in physics and chem? If anyone has any or gives me their reviews on master the content thank you. I appreciate it

This will not be a stupid question, but a stupid series of two posts about the stupid math in the stupid-but-fun movie "Cube".

The number of primes less than or equal to 999 (or, equivalently, less than or equal to 1,000) is 168. This is given by the prime counting function π(1000) = 168.

In the film "Cube", three-digit base-10 numbers give information on (in addition to being a coordinate system) whether given cubic rooms are equipped with a deadly booby trap. Every room has three three-digit base-10 numbers, ranging from 000 through 999. If any one of a room's three-digit numbers is a /prime/ number, or more strongly if any of these three-digit numbers is a /power/ of a prime (which of course includes the primes themselves), then that room contains a booby trap which must be avoided. The trouble is that the characters only have their brains, and the clothes on their backs to work with, to do calculations.

So the question becomes, how many of the numbers from 000 through 999 are powers of primes?

First of all, since we are fortunately not trapped in the cube and have access to a computer, and since π(1000) = π(999) = 168, there are exactly 168 prime numbers less than or equal to 999 - of course, each prime is also a "prime power" in that the exponent is simply 1. We must therefore simply add to these 168 prime numbers, all of the composite natural powers of primes which remain less than or equal to 999.

1/2

What is the realistic maximum temperature the Earth would peak at due to uncontrolled global warming?

Are there any good guides to doing a good final year Physics research project?
Or maybe the blog of someone who did one and got a good grade.

The amount of trial and error involved is /obviously/ minimal, and we have merely to compile a small table of numbers. A sensible approach is to establish an upper bound for which no natural power higher than 1 of a prime will produce a number less than 1000, and work backwards. Consider that the square root of 1000 is in the low thirties somewhere (we don't care exactly where). Furthermore, 37^2 = 1369, while 31^2 = 961. We therefore easily establish that 31, is the largest prime for which a power greater than 1 is yet less than 1000. The problem reduces to raising the first 11 primes to powers until they exceed 1000, and discarding those last results. Furthermore 2, the smallest prime, when raised to the tenth power produces 1024, which just exceeds 1000 - the point being that 9 is the largest exponent that we need consider, in any event. We establish another upper bound to make our work easier.

The practical upshot is that there are exactly 25 composite numbers which are integer powers of primes being less than 1000. Therfore, the final answer to our original question is 168+25 = 193.

Now, about the movie: the female math student Leaven has no trouble determining whether a given three-digit number is itself prime or composite. And yet toward the end when it is realized that powers of primes are also entailed along the above lines, she throws a hissy fit claiming that the work entailed is "astronomical". But as we've just seen, a few elementary observations cut the work down to size in very short order, and in fact the number of composite powers of primes is much smaller than the number of primes. For some reason, the autistic savant Kazan is needed to discover these numbers. The point being that it is absurd that Leaven, who is competent with a fairly complex mental task, is yet unable to make simple observations to attack what turns out to be, in a sense, a much simpler mental task.

It turns out that Leaven is the one who really "sucks at math".

>'flat earthers'
I don't know how this has anything to do with the questions you asked, but I'll give a qualitative answer to what you asked anyway.

>1. a spaceships hull should be turn to shreds in space (vacuum)
HY-80 is a high-tensile strength alloy steel, which has a yield (effective maximum) strength of 80,000 psi (550 MPa) (see: Wikipedia article)
The deepest that a submarine has ever dived is about 10.9 Km down, at that depth the pressure is about
101325(atmospheric pressure)+[seawaterdensity][grav accel][depth] = 110MPa
That's about 1082 Times the pressure that you and I feel at sea level!
Qualitatively, you can probably see that your friends proposal is ludicrous, seeing as we can build vessels that can survive 1082X atmospheric pressure. So we can definitely craft one that can survive 1X atmosphere. (Note that the vessel in space would only have to survive against the pressure difference inside the cab (atmospheric, since humans must be inside), and the zero pressure outside of the vessel (space)).

>2. The sun's radiation is wavelengths and since space has no atoms, the wavelengths should not be able to travel.
One of the properties of electromagnetic waves is that they need no medium in which to travel, as a matter of fact, mediums generally take energy away from the wave that travels through them. Lets think about it, suppose that we need a medium for light to travel, then wouldn't that mean that any vacuum space should appear totally dark? Taking a few minutes to look up vacuum chambers, we know that this in not the case, therefor your friend is certainly wrong.

I can take the time to explain some more, but I think this will do. If your friend tries to refute you, just tell him to read a book on the history of physics, perform some of the experiments related to these topics, and see if he can prove himself right. (he can't)

Mates, why does combining for ex. two linear equations (y=kx+l) solve for their intersect? I understand if you have y=3x+2 and y=4x-2, two equations with two unknowns, and you can solve for their combined x and y and get their intersect point coords,

I just don't understand why it works. The point's coordinates would have to agree with both equations independently, but I just don't understand why it works when I combine them both. Could someone clearly explain it in a simple way?

I have OCD and if I don't understand every nuance of math, it kills me slowly from the inside.

If you have a linear equation, or more generally a functional equation (some equation of the form y = f(x)), it describes a curve consisting of all the points (x, y) satisfying the equation -- that is, all points (x, y) such that y = f(x).

If you have two curves, their intersection is the set of points that are on both curves. So for two curves defined by functions y = f(x) and y = g(x), their intersection is the set of points for which both equation holds; that is, the set of points (x, y) such that y = f(x) and y = g(x).

For linear equations, the intersection consists either of the full function (if f and g are identical), is empty (if f and g differ by a constant), or consists of a single point (in all other cases). For functions in general, the intersection can consist of arbitrary number of points. For example, if f(x) = 3 and g(x) = x^2, the intersection between the curves y = f(x) and y = g(x) consists of all the points (x, y) such that y = f(x) and y = g(x), that is, all points (x, y) such that y = x^2 = 3.

Okay, I've been a lazy cünt during hs, and after it ended, I took a gap year to learn hs math so that I can do engineering or physics in the end on uni.

Now, I've been studying all grades of HS math for a duration of 6 or so months, and I've gone through all of it. I watched YT vids of a professor solve and explain HS math without really practising each topic too extensively (basically he would explain the concepts needed and lay down the formulae, then proceed to solve around 10 problems for each topic).

Now that I have a math test in a month (Matura) I wish to refresh everything I've gone through, how would I go best about it, of course without rewatching all the videos again? I now have a much more concrete understanding of math, and of course from all the vids that I've watched, I have retained the general understanding of all topics and can even derive most of the formulae. I just need to quickly go over everything once again, without consuming too much time. I've got a month to do so.

Thanks, dude.

Type IV hypersensitivity reaction.

is there a list of topics on the test? post them here

it equals f(x) = x+1 if x is not 1, and is undefined otherwise (piecewise!)

Will I see this become safely implementable in my lifetime?

foregen.org/

I read this somewhere (don't be a faggots about it if you find out where)

"You'll eventually understand WHAT math is. It's not just calculating and shit. It's the language of recognition of patterns in EVERYTHING that we do as humans and everything around us.
It's how we as humans interpret the universe. It's all we have! So just keep that in mind. It's the persistence of mankind's thirst for knowledge.
If you think of it like that, and want to understand the world and question everything around you beyond I believe in what everyone else tells me."

Could anyone elaborate on what he means? I'm kind of struggling with math, I mean I'm doing my best to learn it, but I'm not fond of it nor have a natural aptitude imo. I love what physics stands for, explaining anything and everything, why is the sky blue, why does the sun shine, what photons are etc. I love it. But I'm bad at math (currently, still trying to get better at it) and unfortunately due to past experiences, scared of it.

How do I overcome this?

How to I make LaTeX give me flat blocks of color, cell-by-cell, completely shading a given cell or entry, in a matrix-like or tabular environment?

I don't care what the table-environment is, exactly (as long as it can render a very large table). What I care about is that I can point to any one cell, or entry, and simply plug-and-chug the color of my choise in that cell, totally filling the "whitespace" of the cell.

cursory searching on this topic has already brought up the color and xcolor packages, and there are even options ot color different /rows/ to improve readability. I need to drill down to cell-by-cell.

Well, there isn't really a list of topics as it is a general high school maths knowledge test, so basically all grades of high school math in one test.

I'm doing Honors Chem in high school next year. What should I expect?

Also, my friends were all surprised that I got a higher grade in my Biology class than my English class. I don't understand why it's that surprising.

Mathematics is the sum of knowledge that can be gained without observing the world. For example, in physics you HAVE to do experiments and studies and collect evidence, otherwise there's no correlation between your thoughts and the real world. However in math none of that matters. In math whatever you come up with is true no matter where in the universe you are, and even if the universe were different. For example you can imagine a universe where gravity follows an inverse cube law instead, or where elephants don't exist. All of math is still true there, but not all of physics is. Math holds true in any universe.

Moreover, math is the study of abstracting complexity. For example, a coin flip is pretty complex. There's all this physics and chemistry of nickel and other metals, interacting with the atmosphere and various particles in the air, and so on. Math lets us abstract this away into a probability of 1/2 on each side. Now that we've done this, we can use the same math for a coin flip to talk about the probability of getting an even number on a die, because we took the time to do abstraction.

Mathematics is not discovered. It is invented by humans, and it turns out humans want to learn about the universe, so the math they invent usually helps understand the universe. Everything is math.

None of this will help you with your math studies, other than motivation. If you want more advice you'll need to expand on your current knowledge and what you want to learn and why.

does this go up to algebra 2? That might be only a US-thing though

what's the highest level of math you learned? factoring quadratics? graphing inverse trig functions? proof by induction? calculus?

Holy shit I think you're right.Thanks!

What happens if you stick a negative time value into an n-body equation?

Suppose I have some E. Coli...

Can they remain dormant at 14 degrees Fahrenheit? I want to start growing my own at my crib, I just need time to get the materials together (petri dishes, gelatin, beef powder, etc). Speaking of, where the hell can I find Agar powder? I'll use Gelatin otherwise. Oh, and I need a poor mans incubator. I was thinking a rice cooker, one where you can set the temperature.

Answers/suggestions/info much appreciated, help me become the E. Coli whisperer. I'll keep you guys posted if this pans out.

Nothing spectacular. I haven't taken graduate level mechanics yet which is typically when you encounter such issues, but it's not like a negative time value is going to break many equations unless standard mathematical bullshit makes it (e.g. if the equation contains sqrt(t)), then you get a nonsensical answer. Typically we aren't concerned with negative time values. We usually just call the beginning of observation of system 0, but it can be shifted to suit convenience.

>Does you're mummy know?
=
>Does you are mummy know?
Learn to speak english

why dont i have wisdom teeth but alot of other people i know do?

14 F you might get lucky, but it's not a sure fire thing. As for growing them, E. Coli will grow on pretty much anything, so you should be fine without agar. For your incubator, your oven would be decent, or just a cooler with a hot water bottle in it.

I was thinking more about gravitational things.
e.g. T=-5 in a three body equation. Would it cause things to fly apart?

Limits and derivatives come last, and then something more after it, not all that interesting.

I suck at table environments, but I think this might work. tex.stackexchange.com/questions/50349/color-only-a-cell-of-a-table

Is mathematics actually invented? So are you saying that [math]1 + 1 = 2[/math] isn't an intrinsic truth (if you are talking about the abstract notion of putting one and one together)?

Why are prime numbers considered the 'building blocks' of natural numbers?

Mathematics exists only in our heads. 1 + 1 = 2 for no reason other than because thats how we define them. Generally we try to base our math in axioms that reflect the real world, but not always and even when we do theres no way to prove those axioms are correct

What if 'one' is not 'equal to' 'one'?

Sweet. I think the E. Coli I have may have spores in them, so they should be good to stay in my freezer for the time being. Thanks user

Every natural number can be written as the product of prime numbers.

This is a very important fact in number theory and wildly used in encryption.

That would violate certain axioms.
If you are constructing the natural numbers you usually base it on set theory.
"One" is defined as the "set of the empty set" which by the Axiom of extensionality means that it is equal to the "set of the empty set" which was defined to be 1.
So "one" is always equal to "one".

But if you could provide a true proof that "one" does not equal "one" the concept of set theory and most mathematics would break down together with it.

Thank you very much for the link, I appreciate it.

Not only what this guy has already said, but even more importantly, every natural number has a /unique/ representation as a product of primes. There's a bijection from the one representation of numbers to the other - a bijection is a fancy way of saying that everything in one set has exactly one buddy that it pairs off with in the other set, and everyone has a buddy in the other set, with nothing left over or doubled up in either set.

I want you know that this solved my problem. Stupidly, I spent two days trying to figure out how to color in a fucking box in LaTeX and I just wasn't getting the right link (and not for lack of trying on my part), cheers.

Is there any legit reason to care about [math]L^p[/math] spaces with 0

My PhD advisor is dropping hints that he's planning to start a spin-off company soon and would like me to join him.

Thoughts on these sorts of arrangements?

Does anyone know where to find a pdf of this book?

Is arccotangent ever used for anything? Have you ever used this function for anything other than textbook exercises that teach inverse trig functions?

We use positive and negative to refer to numbers larger and smaller than zero.

Is there a similar term for ratios or fractions larger or smaller than one? Like if you had a workplace and were measuring the male to female employee gender ratio, is there a word like "a positive ratio"?

larger ratio and smaller ratio?

Remember, rigorously defined, probability ratios (odds) are not the same as fractions.

How vital is "working memory" within a university?

I feel this question doesn't deserve its own thread since I'm guessing it's been discussed before. Here goes:

I recently watched Ex Machina with a friend. Afterwards, we discussed AI and I said I didn't believe 'true' AI (i.e., machine capable of producing original ideas rather than simulating them) was possible. My friend fiercely opposed this (he's a compsci faggot) but used shitty arguments.

What do y'all think? Personally, I can't foresee it since we don't even understand the complexity of the brain, much less how to create a computer that behaves as a brain.

Why is this wrong?

I totally agree with you. No machine can do something is isn't programmed to do, never will it develop its own ideas (they don't even have ideas they're not rational, they're machines) , unless in some way they are programmed to say/do that thing. Claiming a machine can have free will is bullshit

It's not. I suppose you could go even further and divide the second factor by two, if it's a website giving you trouble.

You in HS, or just trying to learn basic algebra?

If it exists in nature, it can be replicated in a lab (eventually)
Saying it's not is defeatism.

An object in uniform circular motion has its acceleration vectors always pointing to the center of a circle.

What about an ellipse? The planets are in elliptical orbits around the sun and their acceleration vector is principally towards one of their foci, the one at the sun. But the generic ellipse defined by the parametric equation c(t) = (acost , bsint) has an acceleration vector that points towards the origin of the plane, not one of its foci (unless a=b=1 in which case its a circle).

What gives? Also is there a path parameritization for planetary orbits or ellipses with acceleration vector always pointing to one foci?

Aren't plenty of people allergic to aluminum? I always hear about it in deodorants with insane itching and redness.

I think if you do what mentions, you get 3y-5 twice and so could write that expression squared to further simplify it (maybe that's what your electronic homework is trying to get you to do).

I'm 14 and I would like to know how to get better at math.

I feel like the reason I can't concentrate on it is because I have ADD but in order subjects such as English and science I can zone out and do my work.

What should I major in if I want to do something with studying sound? More specifically, audio quality. Electrical engineering?

Why do radioactive particles damage living things?

I tried asking my teacher and the response I got was "they have a lot of energy and that's bad"

that's pretty much it. gamma ray emission is bad because the photons are energetic enough to penetrate into your essential cell components and break up their chemical bonds. The particle emissions, like neutrons, are bad because it can bombard your cells--fucking up the nuclear structure in things like your DNA. The body has adapted to handle low-energy, atomic foreign invaders or visible light with some UV exposure from the sun. It doesn't have effective methods to shield vital cell reproductive components against the emissions from radioactive particles.

Ah, cool. Do the particle radiations also penetrate due to energy or quantum tunnelling? I know they're not as energetic as gamma.

can you prove a theorem is impossible to prove?

You should look into Gödel for more on this type of thing.

EXTREME CAUTION: Due to the abstract nature and the historical significance of his most important statements, Gödel has apparently been misrepresented on a constant basis by internet debaters since the 1990s. Extreme care, willingness to research primary and secondary documents, and critical thought are required when actually discussing the content of Gödel's ideas.

Directly to your point, I state that Gödel's incompleteness theorem can be fairly represented as saying that /there exist/ theorems which are unprovable, whereas your language suggests a specific theorem. I am of little help in discerning between the two situations. You should check wiki and look around for other views on same.

while here, there is also a "completeness theorem" which people like to cite, to feel rounded-out:

en.wikipedia.org/wiki/Gödel's_completeness_theorem

What's so special about the quantity
[math]\int R\sqrt{-g}d^{n}x[/math]

where the integral is taken over an n-dimensional Riemannian manifold, R is the Ricci scalar, and g is the determinate of the metric?

I know this is (proportional to) the Einstein-Hilbert Action in the vacuum and invariance of this action results in the field equations, but I'm trying to understand why the quantity is important enough to differential geometry to suppose that it be invariant in the first place.

Can nothing be proven?

How the hell do you get from the starting equation to the next part? I understand the sequence is being used as a regular function but where did 1/x on the bottom come from?

The first n.

1/(1/x) = x

given function f strictly increasing in R for which it holds that f(x)

But the exponent should change as well, if you make the simple substitution x := 1/n.

things have been proven, so somethings can

[math]\exists M: {\rm I\!N} \precnsim M \precnsim {\rm I\!R}[/math]

Which very roughly means that a set exists that is smaller then the real numbers and bigger then the natural numbers.

Gödel proved in 1938 that this claim cant be disproven and Paul Cohen in 1963 that a proof is also impossible.

But keep in Mind that the things Gödel did is mathematics beyond the level of what we ordinary humans can understand.

For some theorems, you can. For some it is provable that you can't know whether a proof exists or not.

In the "real" world nothing can be 100% proven. In math, whether explicitly or implicitly you ALWAYS make statements like "If [conditions] are true then [statement] is true." You always start from axioms. Whether the axioms are true or not in reality is undecidable but that doesn't change the correctness of the statement "if... then ...".

I don't get the second equal sign. Where did the sum go.

So ( 1 - e^-1/x ) / (1/x) = -1/x * ( 1 - e^-1/x ) / (-1/x2) = ( 1/x * e^-1/x - 1/x ) / (-1/x2) and then what?

> 1. a spaceships hull should be turn to shreds in space (vacuum)

Maybe this helps: A space ship is basically a closed metal box, with high pressurized air inside and less pressure outside. We have similar situations on earth, e.g. a bottle of helium for baloons. Because the metal likes to stick together, the bottle doesn't explode, although the helium inside is under pressure. Same for the space ship, plain and simple. Gas would disperse, because the atoms have velocity in random directions. But since they collide, with the stable wall, they can't. The force of impact on the bottles' surface is the pressure.

>2. the sun's radiation is wavelengths and since space has no atoms, the wavelengths should not be able to travel. If he believes in helium bottles, the believes in spaceships.

> 2. Radiation travels through vibrating atoms/molecules at certain frequencies and amplitudes. How does it travel through space?

Propagation of radiation is a fundamental property of space itself. Space IS the medium and it DOES get distorted like water by a water wave. Every type of energy density (e.g. em-radiation, black holes, stars, planets, single atoms, his ignorant ass) can propagate and distort space. This has been proven again and again since Einstein and GPS, mobile phones and much more wouldn't work if it wasn't so. Radiation does not need atoms to travel.

BUMB!!

What good is knowledge for beside from employment rate and better pay?

proton guns.That is all.