The h Bar

Anonymous

6:01 PM

@Abcd 1. Read about multi-threading. 2. Read String, StringBuffer, and StringBuilder.

Abcd

@Blue Oh Thanks. Threads are explained there.

Sir Cumference

@MartianCactus It seems interstellar travel may never happen, let alone in just 70-80 years

Anonymous

> PhD.History of relativity. Foundations of Einstein's theory

Anonymous

It's rare to find people working on the history of relativity. :)

Terry Bollinger

6:17 PM

Hi @Blue, I forgot to return your greeting the other day!

@Slereah, are you here?

Slereah

Maybe

Anonymous

@TerryBollinger Haha, no probs. There were too many simultaneous conversations going on. ;)

enumaris

@SirCumference but that doesn't take into account either sending out drones to populate the galaxy or some sort of stasis allowing for much longer trips

Terry Bollinger

:)

enumaris

or heavy shielding

Terry Bollinger

6:19 PM

I looked up ADM and don't see how I can do anything but lead to singularities... Which I guess is part of the problem?

Sir Cumference

@enumaris Drones could be destroyed from this too :P

enumaris

@SirCumference no I mean drones that live effectively forever so you could have them on v<0.5c spaceships

within a matter of a few tens of millions of years, we could populate the whole galaxy that way

Sir Cumference

@enumaris I think drones that live forever would have to be an even greater engineering miracle

Terry Bollinger

ADM appears to rely on the first approximation set of assumptions on how to integrate space with momentum in a time frame work. I'm a bit astonished but that's the only way anyone has approached it, since the relationship inherently must be a bit more complex than that. But then I've only begun looking, so I may have misunderstood the intent.

enumaris

@SirCumference well forever in the sense of a few hundred/thousand years

if they can self replicate or self repair then ez

Sir Cumference

6:22 PM

Well we could try, although I'm not sure the resources it'd entail. Perhaps I'm just being pessimistic about it tho

Terry Bollinger

@Slereah no need to reply, but I was just fascinated to see that what I always assumed was a very deep set of relationships in quantum gravity was instead a fairly straightforward hamiltonian approximation

enumaris

think long term :D

in as few as a 10-20 million years, we could have colonized the whole galaxy

Slereah

@TerryBollinger I mean it's still fairly complicated

Sir Cumference

The quora post does mainly focus on sending humans, so I wouldn't know about drones

@enumaris yeah but by "colonize" do you just mean "sent drones everywhere", or "sent colonies of humans everywhere"?

enumaris

drones

they can carry human DNA if spreading human DNA is what's more important

Anonymous

6:24 PM

@enumaris The AI takeover will probably happen way before that. ;P

Sir Cumference

Well in that case we don't need to worry about colonizing mars, already done :P

enumaris

@Blue fo sho

Sir Cumference

@enumaris I think building a human from within a robot would be yet another feat

Eh who knows

enumaris

@SirCumference probably not too bad, just do in-vitro fertilization to get fertile eggs...the only other piece is to create a machine-based incubator rather than using a surrogate

Terry Bollinger

A bit more intensive algorithmic expiration likely is needed. but then I'm from a computer science background, so we tend to think in terms of the space algorithms possible. Our survival focused version of biological intelligence (AI is my real expertise) tends to make us assume too quickly what "obviously must" be right.

enumaris

6:26 PM

breed some humans, have a nice orientation video for when they grow to about 5 or 6 and then let them loose

Sir Cumference

I'm no biologist, but wouldn't the dna suffer from similar biological damage as mentioned in the post?

enumaris

you can shield it

if there's only a small compartment to shield, it'll be much easier than shielding the whole ship

but the post assumes v~c travel

you can just do v<<c travel

freeze the DNA

Terry Bollinger

Heh! I'm doing nothing more than typing notes out loud, literally since I'm using my voice interface. This needs to go into a paper... @Slereah, thanks again for the simple pointer.Time for me to deep dig into the original papers...

Sir Cumference

Idk, i'm a bit skeptical. Seems like a massive time scale

enumaris

10 million years is peanuts

barely the life-time of a supermassive star

Sir Cumference

6:30 PM

or we could just wait $10^{10^{50}}$ years for Boltzmann brains to form. Then boom, galaxies are colonized :P

enumaris

that'

s way longer

10^100 years or so is heat death of the universe so

can't really wait $10^{48}$ orders of magnitude longer

uhhh...

Sir Cumference

@enumaris High estimate for heat death is $10^{10^{120}}$, so who knows lol

Shoot linked to the wrong part of the page

enumaris

"$1.7×10^{106}$ Estimated time until a supermassive black hole with a mass of 20 trillion solar masses decays by the Hawking process.[114] This marks the end of the Black Hole Era. Beyond this time, if protons do decay, the Universe enters the Dark Era, in which all physical objects have decayed to subatomic particles, gradually winding down to their final energy state in the heat death of the universe.[3][4]"

"1 million Estimated shortest time by which humanity could colonize our Milky Way galaxy and become capable of harnessing all the energy of the galaxy, assuming a velocity of 10% the speed of light.[125]"

EZ

Sir Cumference

7:01 PM

All right, imma try to make an h bar ad. Any ideas?

enumaris

recruit people to your initiative to colonize the galaxy

Sir Cumference

Ah, advertise a grander purpose

enumaris

Sounds good to me

Sir Cumference

what's a good catch phrase for the room? or maybe a pic that symbolizes us?

enumaris

Random Thoughts Part Deux

Anonymous

7:11 PM

@SirCumference Insert "asynchronous communication protocol" somewhere, maybe? ;)

Sir Cumference

@Blue I see

perhaps we need to rebrand ourselves as "exciting". ever see those movie posters where there are tons of explosions? those are attention grabbing

Anonymous

@SirCumference Also add few tiny symbols representing music, food, physics, math etc. ?

Sir Cumference

here's my idea

3

perfect

Anonymous

Loool

Sir Cumference

ok i'm just bored rn lol

Anonymous

7:15 PM

Well, that wouldn't really be suitable for display on the main page. XD

Anonymous

That image is going down in history BTW. Downloaded and saved for future use. ;)

Anonymous

Gosh, the Hulk.

Sir Cumference

poor 0celo

enumaris

hey...hey where's my icon

Sir Cumference

you don't have a pic :P

Anonymous

7:19 PM

Just put in a green dot somewhere. :P

Anonymous

@enumaris Oh, you're the Hulk's body.

Sir Cumference

@Blue y-yes, all part of my plan

Anonymous

@SirCumference Loong is the set of the building's windows?

Sir Cumference

why of course, glad someone noticed

enumaris

XD

Anonymous

7:22 PM

Definitely. Genius level art.

Loong

!

Anonymous

@Loong Oops, I guess SirC didn't get time to paint the windows. ;P

Sir Cumference

not big enough budget for that

Novalium Company

Hello brains with complicated neural connections forming the 'reality' and perceptions each of us has.

What the duck is this

where is my face ;(

It's weird how this is considered a community despite the fact that we haven't met each other in the 'real world'.

Of course the term real world has a quite complicated and abstract philosophical reasoning behind it so I'm not going to go into details...

Anonymous

@NovaliumCompany Your face is represented by the greyish clouds and clear sky bordered by those clouds. ;)

Novalium Company

7:33 PM

@Blue <3

I think I'm finally grasping the concept of calculus but I don't know where to use it.
I'm currently exploring the realms of philosophy and non-mathematical areas.

My classical physics 'knowledge' is mediocre. Any chance I can apply my even more mediocre 'knowledge' of calculus there?

Anonymous

Why not learn calculus the proper way?

Novalium Company

@Blue Proper way?

Anonymous

Pick up a high school calculus textbook and solve all the problems. That's the only way to gain real understanding.

Anonymous

You've been complaining about your difficulties in calculus for a long time now!

Anonymous

It's not a difficult subject. But you need to solve problems instead of just reading about it.

Novalium Company

7:37 PM

Are there problems on the WWW?

Anonymous

@NovaliumCompany Yep! Paul's notes is one of the best resources you'll find on the WWW.

Novalium Company

I don't want to just apply the 'Calculus Rules' and solve the 'problems'.

Anonymous

@NovaliumCompany That's the only way to understand mathematics.

Novalium Company

This is not 'understanding' mathematics. It's basically applying rules (something which I don't like) to the problems.

Anonymous

> Young man, in mathematics you don't understand things. You just get used to them.

Anonymous

7:40 PM

Oh, the controversial quote. :P

Novalium Company

I'm not intereted in solving calculus problems. I'm interested in applying calculus to physics.

Anonymous

It's like trying to read Shakespeare without learning A,B,C first.

Anonymous

Understanding comes later. First you pick up the rules and axioms (of course, not blindly!). You'll develop the understanding over time, when you start revisiting things.

ACuriousMind

@NovaliumCompany Almost all physics beyond high school level involves calculus in one way or the other, so don't worry - if you just continue learning physics you'll need calculus sooner or later :P

Sir Cumference

@NovaliumCompany our prototype ad lol

Novalium Company

7:44 PM

mathsisfun.com/calculus/derivatives-rules.html So 'solving' calculus problems involves just applying those rules and getting an answer?

@SirCumference plz add my face, I wanna be famous

Sir Cumference

you don't have a face :P

besides i'm just memeing

Anonymous

@NovaliumCompany Yes. The rules of calculus are all very logical.

Anonymous

If you can't understand where a rule comes from, by all means ask for the proof!

Novalium Company

The question is, do I need to understand where the rule comes from?

I just wanna make sense of calculus, not solve calculus.

Anonymous

That's a dangerous path to choose. You'll only develop a superficial understanding that way.

ACuriousMind

7:47 PM

@NovaliumCompany What you "need" to do always depends on what you're trying to achieve.

Novalium Company

What's the problem to just look at the rules whenever I need to solve a calculus problem?

Sir Cumference

@NovaliumCompany Integration is intuitively like multiplication, except where one quantity changes as the other does. So as a random example, let's say I had a rope whose density changes with distance from the top, as a function $\lambda(r)$. Trying to get the entire mass via multiplication wouldn't be too accurate since I can only multiply a single point. Instead, I would integrate

Integration breaks the rope into tiny pieces, multiplies each density with $r$, and adds them up. So it's by definition a sum of multiplications, where each term differs slightly from the others

Novalium Company

@SirCumference Why are you telling me this?

Sir Cumference

@NovaliumCompany You asked for an idea of when this stuff is useful :P

ACuriousMind

And what the "rules of calculus" are likewise depends on what you're doing. For many applications, you could get away with only knowing how to differentiate polynomials by role application of simple rules. For others, you'd need to know more. To "understand" the rules of calculus, you might learn proper analysis. But then you might think you don't "understand" these argument before you "understand" set theory...

Novalium Company

7:50 PM

@ACuriousMind I'm glad you put "understand" in "".

$I = C\frac{dV}{dt}$ The complexity of the rules I'll have to use in order to solve a problem with this equation depends on the $V(t)$ function?

ACuriousMind

Like most knowledge and understanding, mathematical knowledge exists on a gradual scale from "I have no idea what this is" to "I could derive all of this from scratch from memory", and for most topics, your understanding will end up somewhere in the middle.

Anonymous

I guess by rules Novalium means things like $\frac{d}{dx} (x^n)=nx^{n-1}$. For these things proofs are easily accessible at a high school level.

Novalium Company

^

ACuriousMind

@NovaliumCompany Yes. But I would suggest you're thinking the wrong way about approaching physical problems. Physicists don't learn some bit of math and go looking for physical problems to apply it to. They also don't dream up equations and then try to model as many problems as possible with it. Instead, they usually find a physical problem and then figure out the math required to deal with it.

Novalium Company

@ACuriousMind I totally agree to this.

ACuriousMind

7:55 PM

@Blue Eh, it's all relative and depend on both your notion of "high school level" and "proof" :P I doubt many high schools do the things that are required for a proper definition of the real numbers and limits.

Sir Cumference

...why

Novalium Company

Sooo... why do apples fall. I can apply derivatives to this problem?

@SirCumference Delete your browser history.

Anonymous

Yes, of course. I'm not talking about the rigorous versions of the proofs. :)

Sir Cumference

@NovaliumCompany Uh what?

Novalium Company

@SirCumference Just jokin'.

ACuriousMind

7:56 PM

@NovaliumCompany "Why" is a dangerously ill-defined question. If I answered "Because it is in their inherent nature", does that answer it?

Aristotle thought so.

Novalium Company

@ACuriousMind lol

@ACuriousMind Then I'm smart as Aristotle.

Anonymous

@NovaliumCompany Uh, this is exactly what ACM is telling you to avoid. Don't imagine random problems to apply your newly-learnt math to. You're wasting a lot of time this way.

Sir Cumference

@NovaliumCompany Perhaps "because spacetime is curved" might serve as an answer. And too precisely understand that, you do in fact need calculus :P

Novalium Company

Ok. I just learned a part of calculus. I feel unstatisfied with the fact that I'm not using it to do anything useful. I'm learning calculus to understand the world better. Solving calculus problems is not going to do it.

ACuriousMind

A more precise and most importantly quantitative question related to gravity you could ask yourself is: "How long does an object take to hit the surface of the Earth if it starts motionless at a distance $r_0$?"

Sir Cumference

7:59 PM

@NovaliumCompany I mean just pick up an undergrad classical mechanics book if you immediately want to start applying it

ACuriousMind

But answering this question would already involve having to solve an ordinary differential equation, after having derived said equation from Newton's laws and Newtonian gravity.

Sir Cumference

it'll expect you to be pretty comfortable with calculus tho

ACuriousMind

Finding problems for which one is not under- or over-equipped at random is basically not a successful strategy, which is why the best sources of suitable problems are textbooks that specifically choose their problems such that they can be solved by what they just taught you

Anonymous

The problem is: Novalium wants to jump to physics problems without getting acquainted with the formalism of calculus first. There's a sequential way to learn everything...just jumping around doesn't help!

Novalium Company

Ahh... I wanna meet you guys in the real world and have a conversation there. I feel socially unsatisfied with this method of communication. It's like a deception. I'm still learning tho, which is the main reason I'm here.

Sir Cumference

8:02 PM

@NovaliumCompany If you want to apply calculus, then understand the theory well enough to realize when it's applicable. That's pretty much the deal with any type of higher level math.

Novalium Company

I learned derivatives. I wanna apply them somewhere.

Sir Cumference

@NovaliumCompany Pretty sure very few people here have met :P But we still have a community over a chat

@NovaliumCompany Again, I'm sorry to say but you won't really have learned derivatives until you have an intuition for them. That's done in a math course. Simply knowing how to compute derivatives won't help you better understand the universe.

Novalium Company

What do you mean by "intuition for them"?

Sir Cumference

Getting a feeling for what differentiation and integration are doing, and realizing why they would be applicable. A good site for this stuff is this

But in general, an idea of how to motivate differentiation/integration and why we'd want to define them the way we do.

When you know that, you quickly see when they're applicable

Novalium Company

@SirCumference The website is quite interesting. Thanks.

Sir Cumference

8:09 PM

I found calculus to be the first transition from solely memorizing ideas in high school, to understanding why they should intuitively make sense in college

@NovaliumCompany No problem. Easily the best supplementary resource I used when learning calculus

For clarity, the calculus section is here from the bottom upwards

Novalium Company

Alright then. I'll continue learning calculus, the rules, and digging deep into the small holes. Hopefully patterns will start to appear and I'll understand where in physics I can apply the knowledge. :P

Anonymous

If you want to "apply" derivatives it's best to start with kinematics first. For instance, Resnick Halliday covers calculus briefly in the first couple chapters and then proceeds with the physics i.e. kinematics. You'll find a lot of real life physics problems there (where you can apply calculus). The PDF is easily available online.

Novalium Company

Okay. I'll go to bed, tommorow I'll continue my calculus learnings. Thanks everybody for your time.

Anonymous

Bbye!

Novalium Company

8:30 PM

One last thing. I'm reading this article: real-world-physics-problems.com/curvilinear-motion.html and I was wondering why the magnitude of the velocity of particle P is given by summing the individual x, y, z squared, and then taking the square root of that?

Mo_

8:42 PM

@enumaris congrats! I got my first admission too

enumaris

@Mo_ admission? Like to college or grad school?

Sir Cumference

9:04 PM

@enumaris PhD program iirc

enumaris

nice nice

Anonymous

@Mo_ Congrats! Which place is it?

Physics Meta

1

Q: I am having trouble improving how my questions are received

Is there a way I can improve how my current questions are received because no matter what I do they get received worse? They don't even tell me what needs improvement.

M.N.Raia

9:20 PM

Good evening/night/morning/afternoon for everyone!

I would like to ask you something about the nature of computers.
Well, consider for instance the algebric structure called Magma as exposed here: https://en.wikipedia.org/wiki/Magma_(algebra)
So, if you ask "what is the most fundamental algebric structure?" then probably your answer would be "magma".

Following this analogy, what is the fundamental notion of a computer? I mean, our PCs are just a physical implementation of physics and mathematics, that we can interact. To constrain in some sense my doubts, consider then Thermodynamics,Clas…

ACuriousMind

@M.N.Raia 1. I would never call a "Magma" the most fundamental algebraic structure. 2. The standard abstract computer is a Turing machine.

M.N.Raia

@ACuriousMind Ok, why not? (about the 1) )

ACuriousMind

Because it's useless :P

I've never needed "magma theory" for anything. Group theory, on the other hand...

M.N.Raia

Yes, of course and a totally agree with you. But what generate the notion of a group? A magma with more structure.

@ACuriousMind

ACuriousMind

Most of mathematics is just "sets with structure".

M.N.Raia

9:27 PM

Indeed

Slereah

9:42 PM

@ACuriousMind such set theory chauvinism

you can build mathematics from many things!

M.N.Raia

Just for the record: I know some of your from the time I spended here, since 2015 I guess. Like @ACuriousMind @Slereah @Qmechanic @JohnRennie
Well, I'm the Jack Clerk, I just changed my name.

Slereah

Woo

M.N.Raia

some of you*

Just for the record: I know some of you from the time I spend here, since 2015 I guess. Like @ACuriousMind @Slereah @Qmechanic @JohnRennie
Well, I'm the Jack Clerk, I just changed my name. **

Anonymous

What's up with everyone changing their names these days... :P

M.N.Raia

That's my real name Mário Raia Neto and that's me,for real, in the photo.

Anyway, I don't know why I said that.

Anonymous

9:48 PM

Ah. Nevertheless, welcome back. ;)

enumaris

I actually answered a question on Chinese SE

LOL my Chinese is so bad

Mo_

@Blue creol.ucf.edu

I don't know how to reply though (as I'm waiting for other applications)

Anonymous

@Mo_ Awesome!

Mo_

@AC still not interested in a PhD?

@Blue :)

finally switching to physics

enumaris

10:03 PM

They generally give you a good amount of time to decide

Anonymous

Ha-ha, yesssh...finally! :D

enumaris

unlike in the business world where they want you to accept/deny an offer within 24 hours or sometimes on the spot...

Anonymous

@Mo_ So when does the session start generally?

Anonymous

Around October?

enumaris

Aug/Sep/Oct is generally when most colleges start

more Aug/Sep than Oct in my experience

Mo_

10:04 PM

Yeah should be in September

Anonymous

Oh, it's nearly same here.

Anonymous

> Welcome to CREOL, The College of Optics and Photonics, a world leader in education, research, and industrial partnership. Optics and photonics is the science and technology of light: lasers, LEDs, LCDs, optical fibers, and imaging systems for applications in industry and medicine. Learn more by exploring this website, and visit us to see our facilities and meet our faculty, staff, and students.

Anonymous

Still sounds a bit like engineering. ;)

Sir Cumference

@Blue Huh good point. Obe, skullpatrol, etc.

enumaris

woah woah woah

Mo_

10:06 PM

@ACuriousMind a phd here awaits you mpp.mpg.de/en/research/structure-of-matter/string-theory

enumaris

why's Chinese Beta have questions 3 years old...

how long can you remain a beta site...

ACuriousMind

@Mo_ ?

Anonymous

@Mo_ ACM has already been fully corrupted by the software world; can't go back! ;P

Mo_

@enumaris as long as the stats show the website can graduate

enumaris

He's saying if you go to that address, they will have a PhD waiting for you to claim.

Mo_

10:08 PM

@enumaris exactly (admission guaranteed :)

enumaris

no no, not just admission guaranteed, but they have a physical PhD ready for him to claim

Mo_

6.5 years in beta

Anonymous

@enumaris The longest is ~8 years I think (till now).

ACuriousMind

@enumaris Indefinitely

enumaris

That's a long beta

Anonymous

10:11 PM

They're changing things though. The graduation process is going to be revamped in the near future, from what I've heard.

Anonymous

There's also this "design-independent graduation" thing these days.

Anonymous

96

Q: Design-Independent Graduation is on for early September!

This is a follow-up to an earlier discussion Feedback Requested: Design-Independent Graduation. Like the title says, design-independent graduation will go into effect and become our new regular practice the second week of September! All sites which have been waiting in the backlog to graduate w...

discussion election beta-sites graduating-sites

ACuriousMind

Robert essentially said they're not really currently graduating anything and redesigning the process here two days ago.

Anonymous

Since beta sites are no longer closed except in the extreme cases (say when the site moderation is dysfunctional and flags are not being handled regularly), the difference between graduated sites and beta sites has become narrower. Now it's mostly just a issue of removing beta labels and setting up additional migration paths (apart from re-setting the reputation levels required for accessing site privileges).

Anonymous

> I am in the process of writing up a comprehensive site life cycle workflow which (among solving many other issues) would include breaking apart "graduation", and enabling each feature as soon as a community can reasonably support it. It's roughly based on the premise I outlined here — But what happened to Graduation?.

Anonymous

10:19 PM

That's good news!

enumaris

SE weird

Anonymous

@enumaris They have been pretty inconsistent about this graduation thing, yes.

enumaris

oh man, the VP that hired me won't even be in the office when I join lol, he'll be back in Germany until the grand opening in March...hmmm...

I guess I'll just have to see how things are managed when I get there

Mo_

@enumaris Is this (your) office in San Francisco?