The h Bar

« first day (2907 days earlier) ← previous day next day → last day (2013 days later) »

12:22 AM

(Another one from *today* in this vein
https://slate.com/news-and-politics/2018/10/trump-lies-kavanaugh-khashoggi.html )

I feel like you don't know physics until you know every subalgebra of the semi-simple lie algebras :(

4 hours later…

Secret

3:59 AM

science.sciencemag.org/lookup/doi/10.1126/science.aar3106

I might dig into the article later to see where in complexity space the quantum computing domain lies at. It will be surprising if such scale independence on computational efficiency cannot enter the NP space territory

Secret

4:18 AM

nature.com/articles/s41565-018-0255-3

And so, we can pack more skyrmions per unit area

user280247

if Im not mistaken @Semiclassical has answer this question today

Akash. B

5:14 AM

@JohnRennie sir, are you there?

John Rennie

@Akash.B morning :-)

Akash. B

@JohnRennie how will be the time for an observer who experiences no gravity ?

John Rennie

@Akash.B you mean someone floating in space far from any planets, stars, black holes or whatever?

Akash. B

@JohnRennie yeah

John Rennie

5:33 AM

@Akash.B the time for someone floating in space is basically the same as the time we experience here on Earth. Time goes very slightly faster in space because Earth's gravity slows time by a very small amount. But since Earth's gravity isn't very strong the difference between time in space and time on Earth is very small.

5 hours later…

Avantgarde

10:18 AM

Enjoy Saturday

Secret

10:57 AM

What are the Strings in String Theory? | Space Time

►

Ok so the best test on whether our universe is a simulation, is to simulate black holes and found we can never simulate the actual one

If our universe is not a simulation, then we should be able to simulate a black hole with hardware smaller than the size of the universe

(NB: The context of the above comment is based on at the end of this video where questions on the previous episode is answered)

But I guess, on second thoughts, is it possible to know that we can never simulate a black hole perfectly. Just the experimental data compared with the simulation is not enough to establish there is an upper limit to the resolution of the simulation

It's the same idea we cannot prove there exists infinity from induction from the natural numbers

3 hours later…

Secret

1:40 PM

in Mathematics, 5 mins ago, by Holo

hmm... @Secret if I can teleport without restrains, i.e. I can teleport without "cooldown". Then I teleport without stopping, at a given point of time, where am I?

We have a... very curious case which is basically saying that a given a region of space, the probabilty of finding a particle at any specific location is zero, but the probability of finding the particle in that region is one. Is that even possible at all?

Anonymous

2:07 PM

@Loong I didn't notice that message earlier. The view outside is absolutely wonderful! Which place is that? :)

Anonymous

Oh, and is that your book? :P

Corvo Attano

2:23 PM

Hi, I worked for a while on a kind of cool question but then realized it was off-topic for Physics, here it is:

Indestructible Earth-sized and weighted sphere

Hello, Physics. This is a weird question I've always had.

So, imagine you are on an earth-sized, indestructible sphere made of the same weight of material throughout, weighing in total the same as the Earth, and somehow make a hole through the middle of it.

After doing this, you drop a rock down into it. What happens with gravity? Does it fall onto the sides? Does it fall down to the center? Does it just float over the hole? Does something completely different happen?

[![enter image description here][1]][1]

vzn

in theory salon, 24 secs ago, by vzn

Artificial intelligence better than physicists at designing quantum science experiments / ABC news

↑ interesting parallels to (newer) stellarator control systems! vzn1.wordpress.com/2018/10/03/collatz-fusion

Secret

Q: Would you be weightless at the center of the Earth?

If you could travel to the center of the Earth (or any planet), would you be weightless there?

Corvo Attano

But if a human were at the center, wouldn't their limbs be pulled in different directions due to being closer to other parts and get pulled off by all the gravity around?

Secret

newton shell theorem will cancel out all the gravity, leaving with a net gravity of zero

a hole is basically a cylinder, by symmetry, all forces will cancel out

John Rennie

@CorvoAttano If you are in a hole centred on the centre of the Earth then the gravitational acceleration everywhere in that hole is zero.

This is called the shell theorem

2 hours later…

Secret

5:00 PM

Q: Have fractional order differential models been explored as an alternative to standard gravitational field theory?

Since Einstein introduced his field equations and general theory of relativity, experimental evidence, at least on the cosmic scale has repeatedly supported the theory. Nevertheless, many seeking to extend the theory (Grand theories that combine relativity and quantum mechanics) or to explain gap...

general-relativity mathematical-physics models modified-gravity

hmm...

stochastic GR anyone

arxiv.org/abs/0802.0658

2 hours later…

amanuel2

7:19 PM

Hello! I got a simple physics question

In a review at class it asked me "Which of the following is the condition for static equilibrium? Select all apply."
A) Position = 0
B) Velocity = 0
C) Net Force = 0
D) Net Torque = 0

I said Velocity = 0, Netforce = 0, and Net torque =0. But i got that wrong. Does it mean position =0 ? If so why?

danielunderwood

8:01 PM

Well position being zero doesn't really make sense since you're free to choose how you define your position. I'd probably normally say velocity is zero for equilibrium, but you have a similar choice of inertial frame so you can just choose a frame where the velocity is zero provided that forces balance

amanuel2

8:45 PM

@danielunderwood Nvm, it was only Netforce =0 and Net torque = 0. Thankfully i got it! Thanks for the help! :)

danielunderwood

9:03 PM

Actually you couldn't choose a rest frame if you had more two or more bodies with different velocity. Two blocks moving away from each other at constant velocity would have no torque or force, but I doubt anyone would call that static equilibrium

3 hours later…

Avantgarde

11:37 PM

velocity = 0 can't be an equilibrium, eg. pendulum at its highest point