The h Bar

Novalium Company

5:22 AM

Mood gorning biological organisms

John Rennie

5:34 AM

@NovaliumCompany Mood gorning sounds like a town in some third rate fantasy novel :-)

Slereah

6:58 AM

hey

Novalium Company

7:46 AM

I just watched Synchronicity. Movie is nice but I feel like they didn't end it properly. I still don't have a clear explanation for the ending.

A question for dreamy beings: Do you think we'll ever be able to open up an artificial wormhole and travel through it?

John Rennie

@NovaliumCompany no

Novalium Company

@JohnRennie optimism at it's finest

John Rennie

Wormholes (probably) require exotic matter and that (probably) doesn't exist.

Novalium Company

I say, maybe the universe doesn't work the way we think it does. Maybe it's possible.

I feel like quantum mechanics is either too complicated for us to make proper sense of, or the universe is weird. (or maybe something else)

John Rennie

The thing is that QM works i.e. when we use it to predict the results of experiments we get the correct results.

You can suggest that there is some special case we haven't discovered yet where QM does something screwy ...

Novalium Company

7:52 AM

Yep, that makes it even stranger. Something so counter-intuitive works. Why? Go figure...

I feel like there's something we're missing. Something that will explain this weirdness.

If someone thinks we have figured everything there is to figure in physics, go read some history.

PM 2Ring

@NovaliumCompany "I have no doubt that in reality the future will be vastly more surprising than anything I can imagine. Now my own suspicion is that the Universe is not only queerer than we suppose, but queerer than we can suppose." – J. B. S. Haldane

@NovaliumCompany Oh, we know that current physics has problems. Primarily, we don't know how to unify quantum physics with general relativity. Part of that problem is that most of the time you can ignore quantum physics when doing stuff that needs GR, and conversely, you can generally ignore GR (and indeed gravity) when doing quantum physics. You only need the combination in really extreme situations, and those situations are really hard (or downright impossible) to observe or reproduce in the lab.

Secret

8:12 AM

Random thought about omnipotence:

Trying to understand what happens when two omnipotents interact is very similar to how an entangled system behave wrt to an unentangled one

The analogy is as follows:

Recall that the major difference between an entangled state vs an unentangled state is that it has correlations that can exceed a certain bound prescribed by local hidden random variables

In QM, we have a model for the explanation of this phenomenon as superposition and hilbert spaces allows a richer algebraic structure that can allow such correlations, such as for some entangled state, you can have 1:3:3:1 for the outcomes of 00, 01, 10, 11

Now, in omnipotent interactions, we knew that because the two participants are omnipotent, it means regardless of what happens in that interaction, there is a resolution

thus they can produce something that is otherwise not possible in an non omninpotent system

However, unlike QM, because of the very nature of omnipotence necessarily violates classical or even modal logic, we do not have an explanation on how that resolution is made possible, other than the fact it is possible

Two interacting omnipotents also make me think of how many QFT interactions not in a strongly coupled system behave:

We usually start with fock states from infinity, and then they came together, interact in some unknown way, and then produce new fock states. We can then use these initial and final conditions to construct the S matrix that describe this interaction, even though we actually knew nothing in general what happens in the interaction regime

This is very similar to how when two omnipotents interact with each other, except we do not even have the luxury of producing a S matrix to model the interaction itself, it is fundementally incomprehensible

I guess, if at any time one felt stumped in QFT, go indulge in heaps of philosophy literature on omnipotence, and then you might just suddenly find the solution because compared to comprehending omnipotence, QFT is an easy piece of pie

PM 2Ring

8:30 AM

@Secret This concept may not be easy to digest for people raised in cultures dominated by Abrahamic faiths. In those faiths, there can only be a single omnipotent god. But it would be interesting to discuss it with someone from a polytheistic faith, like Hinduism. But even there, although Vishnu and Shiva may be considered omnipotent they never manifest their full potency outside their private abodes.

Secret

yeah, from what I read, it appears most omnipotent gods are often reluctant to display their full power and are humble. Meanwhile God in abrahamic religions is the one and only, thus God has no trouble of running into conflict with omnipotence

Beta Decay

9:28 AM

Quick question: If the solar system were to be ejected from the galaxy, that wouldn't really change anything for life on Earth, right (assuming the Solar System isn't disrupted in any way)

The Galactic Habitable Zone is about star and planet formation from what I recall

ACuriousMind

Navigation by stars would certainly become more difficult :P

Beta Decay

9:42 AM

But at least we'd get a lovely view of the Milky Way

Physics Meta

-1

Q: Divergence of Discountinuous Electric Field

$E = E_{o}$ x < a E=0 x > a Now try to guess which charge distribution could give rise to this field without further calculation. Now use the equation ∇ · E = ρ/ϵo (which this time will require the derivative of a step function discontinuity) to figure out ρ

discussion

PM 2Ring

9:58 AM

@BetaDecay It could reduce the inner Solar system being bombarded by comets from the Oort cloud. But that probably depends on the exact mechanism that propelled the Solar system out of the galaxy.

@BetaDecay We can currently see the Magellanic Clouds, which are nearby dwarf galaxies. (At least, those of us in the southern hemisphere can). They aren't very bright to the naked eye.

Beta Decay

@PM2Ring So in fact it may be beneficial to us? i.e. no more extinction-level events?

PM 2Ring

10:32 AM

@BetaDecay Potentially, yes. But I don't see any way to eject the Solar system from the Milky Way that doesn't cause all sorts of chaos.

Beta Decay

Ah I see

I was considering the Andromeda-Milky Way merger

Novalium Company

11:32 AM

123

PM 2Ring

12:23 PM

@BetaDecay Ok. That's in about 4.5 billion years, not long before the Sun expands into a red giant, causing plenty of chaos, especially in the inner Solar system. The Earth will be uninhabitable in about a billion years because the Sun is gradually getting hotter as it ages. On Earth, the temperature increase will cause a runaway greenhouse effect, and the ocean will boil away.

Beta Decay

@PM2Ring Yes, but I wanted to know whether habitable life could survive an ejection

PM 2Ring

@BetaDecay I believe that it could, if the ejection happened slowly. But I don't know a way to make that happen naturally. With sufficiently advanced technology, I guess it's possible to move a star, and drag the planets & other system stuff along.

Stellar engine

Stellar engines are a class of hypothetical megastructures which use a star's radiation to create usable energy. Some variants use this energy to produce thrust, and thus accelerate a star, and anything orbiting it, in a given direction. The creation of such a system would make its builders a Type-II civilization on the Kardashev scale. == Classes == There are three variant classes of this idea. === Class A (Shkadov thruster) === One of the simplest examples of stellar engine is the Shkadov thruster (named after Dr. Leonid Shkadov who first proposed it), or a Class A stellar engine. Suc...

John Rennie

3:16 PM

If anyone is interested there is an interesting article about Atiyah on the AMS web site (12 page PDF). It mentions his interests in physics, though not in great detail.

yuvraj singh

@JohnRennie hi

There is an technical error in my phone can you help me

John Rennie

@yuvrajsingh what's the error?

yuvraj singh

Sir actually my phone sound and mic both stop suddenly, although I went to techcian he said both speaker and mic is OK, both nice, and speaker are currently working, after I switch on my phone, but after 5 to 10min a sound comes and voice stop @JohnRennie

Ryan Unger

Rennie the IT guy

John Rennie

@RyanUnger :-)

@yuvrajsingh does the sound stop for everything i.e. all the apps you try won't produce any sound?

yuvraj singh

3:31 PM

Nothing, sir even the keypad sound, voice everything drop @JohnRennie

John Rennie

Have you tried factory resetting it?

yuvraj singh

You mean deleting all data @JohnRennie

John Rennie

Yes. In the settings there is a factory reset option that completely wipes everything on the phone and returns it to the state it was in when it left the factory.

This is a last resort as you lose all data on the phone that isn't backed up somewhere, but it can fix stubborn problems.

yuvraj singh

I recently format my phone, but the issue is Same @JohnRennie

John Rennie

Are there any software updates available for the phone? What model phone is it?

yuvraj singh

3:35 PM

Yes phone says, me to update it version but I haven't, t done it yet, I have redmi note 3 @JohnRennie

John Rennie

It might be worth installing the latest update.

yuvraj singh

Finger cross, I am doing it, it take minutes only @JohnRennie

John Rennie

@yuvrajsingh good luck! :-)

yuvraj singh

I am going to buy a new laptop, can you suggest me @JohnRennie

John Rennie

@yuvrajsingh how much do you have to spend?

yuvraj singh

3:41 PM

You mean in euro or rs @JohnRennie

John Rennie

Either

yuvraj singh

maximum 60 thousand @JohnRennie

John Rennie

You should be able to get a great laptop for that sort of money.

yuvraj singh

Current I have hp @JohnRennie

John Rennie

For example look at this one for 44k

yuvraj singh

3:46 PM

Look good, but I am not much sure about the brand @JohnRennie

John Rennie

Asus is a trustworthy brand. But I'm not specifically recommending that laptop - it was just the first I found on Flipkart.

Lenovo also have lots of good laptops in your price range.

yuvraj singh

You have apple I think @JohnRennie

John Rennie

The problem is likely to be that there are so many good laptops in your price range that you won't know which of them to choose.

yuvraj singh

True @JohnRennie

John Rennie

@yuvrajsingh I tend to use Dell computers because the company I used to work for uses them and I know Dell's range well. But I think Dell laptops tend to be expensive in India for some reason so they wouldn't be a great choice.

Ryan Unger

3:50 PM

@JohnRennie uh whats the conversion rate

yuvraj singh

I think hp and Dell have the same range, when I went to shop, 5 years ago, he shows me the Dell laptop first

John Rennie

The number one recommendation I have is to buy a laptop with a solid state disk - often called an SSD. These are more expensive than regular disks but they are so much faster than regular disks that they are worth the extra.

@RyanUnger last I looked it was about 85 rupees to the pound, and a pound is about $1.20.

user8718165

hii @JohnRennie

John Rennie

But the Indian customs have steep tariffs on imports of computers so they are relatively more expensive in India.

yuvraj singh

Which one @JohnRennie

John Rennie

3:52 PM

@yuvrajsingh do you mean which laptop with an SSD ?

yuvraj singh

Yes @JohnRennie

John Rennie

All the manufacturers do laptops with SSDs. That Asus VivoBook I linked has a 512GB SSD.

@user8718165 hi :-)

@yuvrajsingh what I'm saying is, regardless of which manufacturer you prefer, Dell, HP, Lenovo, Asus, Acer, Samsung, etc, you should choose one of their models that has an SSD. It is the most important thing to have in a laptop.

yuvraj singh

Ok @JohnRennie I think I will download update tommorow only, if the problem what should I do.

John Rennie

@yuvrajsingh I would guess that there is a hardware fault in your phone, and that the update will make no difference. Sorry :-( But the update is worth trying just in case.

The update shouldn't delete any data, so it should be safe to install whenever you want.

Have you tried plugging in headphones to see if the sound works on headphones?

yuvraj singh

Right now, when I am talking to you phone sound is there, but I think it can go any time, no tried the headphone but there was no sound. @JohnRennie

John Rennie

4:00 PM

Hmm, no sound on the headphones either? Oh well, try the update and see if it works.

yuvraj singh

I think if doesn't, t work I am going to buy a new phone, @JohnRennie

With my b udget of laptop can be low @JohnRennie

Can you prefer @JohnRennie

John Rennie

You can get good phones surprisingly cheaply these days, though I don't know a lot about the phones available in India. The Chinese brands like Xiaomi and Huawei are probably the best value.

yuvraj singh

I think biggest festival of India Diwali is coming up, so there are so much of discount on products

John Rennie

How much would you spend on the phone? For example the Xiaomi Redmi Note 7S is around ₹10K and it's well regarded.

yuvraj singh

If I buy the laptop of 44 let say then 16 @JohnRennie

John Rennie

4:09 PM

I would guess you'd get a good phone for ₹16K

@yuvrajsingh there are some amazing Diwali deals on Flipkart! :-)

It's almost a shame I don't need a new phone :-)

yuvraj singh

Good night sir @JohnRennie

John Rennie

@yuvrajsingh bye :-)

Novalium Company

4:44 PM

Why is Earth flat?

PM 2Ring

5:14 PM

@NovaliumCompany Because it isn't. Curvature is inversely proportional to radius, so if a sphere has a large radius then it has a small curvature, and it will appear flat when you look at it from up close.

Novalium Company

5:37 PM

@PM2Ring The Earth is flat dude. The government is lying to us. NASA is trying to fool us.

I'm a proud member of the Flat Earthers Society.

user8718165

hii :) @PM2Ring

Novalium Company

If Earth is a sphere, then why are maps flat?

I'd suggest you learn some geography. Get a textbook but those which say Earth is a sphere or a geoid are fakes spread by the government.

Semiclassical

6:45 PM

@PM2Ring I can't tell when people are being srs about flat earth vs trolling

Naveen Balaji

7:08 PM

Hello all. A GR question: It is known that in 2-d, any (regular) metric solves einstein's equations. Is it possible to construct an asymptotically flat metric, that is regular at the origin (take periodic euclidean time) but with the correct discontinuity, if we put a shell with arbitrary stress tensor on it? Would starting with and trying this for a constant stress tensor get somewhere?

PM 2Ring

7:57 PM

@Semiclassical Me neither. But I don't care, because I know that in either case any form of rational discussion is futile. OTOH, sometimes I'm tempted to engage in hyper-trolling: the Flat Earth movement was started by the government to reveal people who are gullible enough to believe in ludicrous conspiracy theories. And now that the government has that info, it can feed those people anything it wants.

Sha Vuklia

8:47 PM

guys, what exactly do they mean by an exterior solution?

ACuriousMind

@ShaVuklia the part of the wavefunction that's outside the barrier

Sha Vuklia

say we have V(x)=0 for 0<x<a, V(x)=C>0 for a<x<b, and $V(x)=\infty$ otherwise

@ACuriousMind yea, there lies my problem

given the potential I just gave

because we also have a vertical wall within the barrier

is griffiths still making a claim on such a finite vertical wall within the barrier?

because it seems that he is saying, as soon as we have vertical walls, we are free to patch together WKB solutions

while when the walls aren't vertical, we have to resort to a more elaborate patching technique

ACuriousMind

Yes, that's right. Where's the problem?

Sha Vuklia

wait wait

so I didn't see why the WKB approximation doesn't break down, but I have to check the assumption

maybe that will clarify things

right, so the assumption in WKB is that the amplitude varies slowly

more precisely, $A''/A$ is very small compared to $(\phi')^2$ and $p^2/\hbar^2$

so my question is

how does it follow from this that at a vertical wall, WKB doesn't break down?

oh hm

I think I kind of intuitively see it

in the case of a tilted potential, you can say that WKB breaks down in the vicinity of the turning point

so the whole WKB solution near the vicinity doesn't make sense

while in the case of a vertical wall (finite or not), we know that WKB holds arbitrarily close to the turning point

so there is no point in patching solutions in vicinities of the wall. all we have to do is patch them together at the exact turning point

okay sry, this was actually a bit easier than I expected

but I felt extremely confused for a second

Sha Vuklia

9:14 PM

okay, so final question: What we want is that $A''/A$ is much smaller than $(\phi')^2-p^2/\hbar^2$ for WKB to work. In the vicinity of a turning point (which is not a vertical wall), we have $p(x)=\sqrt{2m(E-V(x))}\approx 0$, so obviously $A''/A$ can't be much smaller than $p^2/\hbar^2$.

However, what if $(\phi')^2$ is still relatively large? It seems that WKB would still hold then. So I'm guessing my question is how $\phi'$ relates to the potential (or the difference between $V(x)$ and $E$), and if we are safe to assume that $\phi'$ will also be relatively small at a turning point?

Sir Cumference

10:15 PM

@skullpetrol I think this tag will become increasingly plausible if SE keeps making posts like this

Scientist Smith YT

11:30 PM

@PM2Ring I will be free in maybe less than an hour from now. If you can talk to me about what we were talking about a while ago in about an hour or less from now please let me know. I really want to continue our conversation. If you can't talk in an hour or less from now also let me know. I'm terribly sorry for all of the interruptions stopping us from being able to talk.

Transcript for