The h Bar

@SirCumference zeldredge's comment contains the answer: Your idea that the time of the sun goes faster from your perspective is simply wrong. Time dilation is symmetrical: If two things move relative to each other, both see the time of the other go by slower.

If you think this is confusing, you're not alone - search this site for endless variations on the twin paradox, for instance.

Sir Cumference

Ah, I get it now

3:08 AM

@vzn But I thought chaotic systems are still predictable at least at the time interval very early in the evolution of the system?

because the uncertainty in the prediction only diverges exponentially

@SirCumference Awwwwww, I made really cool plots to illustrate this!

And then the post was deleted. Booooo!

I think I am looking for a type of dynamics so extreme that no matter how large or small the window one pick (temporal or spatial), no matter which stage of the evolution of the system and which point you pick, you cannot predict the evolution of the system based on all the information at that point and its history?

is this actually a non deterministic system the one I am seeking?

@Secret Sure sounds like it.

@SirCumference I'm sad that your post was deleted. Here are my plots:

Awwww, is there a way to paste images into chat?

@DanielSank Click "upload"

try upload them one by one

I always did that

3:13 AM

Yay!

Ok check it out: The green lines are the left and right edges of Earth.

The black line is your world line as you move across the Earth.

The Black dot is when you cross the right edge of Earth, and the Green dot is when you cross the left edge.

What is this discussion about? Time dilation?

yup

The red dot is when the sun explodes and the red line is the "shockwave of death" from the sun's explosion.

@SirCumference Are you following?

Note that you cross the shockwave of death when you're 1/2 of the way across the Earth.

Now here's the same thing from your point of view:

Exactly what about time dilation?

Here the sun explodes way earlier.

3:16 AM

I see world lines! First time seeing them used as an application apart from in my GR textbook that I am reading

However, look at this zoom-in on the interesting part:

@DanielSank whose perspective?

It's the frame of the moving person, i.e. the black line.

Who is accelerating? What are the inertial frame?

That's why the black line is now vertical, i.e. stationary.

@TanMath The first frame is co-moving with the sun and Earth (assuming sun and Earth are not moving relative to each other).

The second frame is co-moving with the person whose world line is black.

@SirCumference The death ray still hits you when you're 1/2 of the way across the Earth. This has to be true because events which occur at the same time and same position are always the same time and position regardless of frame.

3:18 AM

@DanielSank how is that possible? The sun is not moving and the Earth is!

@TanMath Dude, it's an approxmiation.

Fine...

I cannot follow this discussion...

@TanMath Also, to say that the sun is not moving and the Earth is moving is not true. Which one is moving depends on your frame. Motion is relative in relativity.

Anyway, @SirCumference, I hope this clears things up for you. If you study the diagrams you'll understand everything.

@DanielSank true...I cannot imagine a frame where they are both moving at the same speed

@TanMath Well, there's definitely a frame where they're moving at the same speed but in opposite directions.

3:21 AM

Really?

@TanMath Well, yeah. At least, in a 1D world...

" This has to be true because events which occur at the same time and same position are always the same time and position regardless of frame.
"

Now that's kinda new (unless my memory fails me again), I thought only the squared interval between two events is invariant for all frames and not the events themselves

@TanMath Of course - the frame of something orbiting the sun (in the sun's rest frame) at exactly half the radius of the earth orbit with such a velocity that sun-thing-earth is always a straight line In the thing's rest frame, sun and earth are orbiting it at the same speed.

@Secret Yeah, so if the squared interval is zero in one frame it's zero in all frames :-)

no I mean, i am not sure if a single event themselves are invariant to all observers, because that seemed to be what you are implying?

3:32 AM

Hey @ACuriousMind, I made a broke-ass program to plot space time diagrams.

@Secret Of course not, and I don't think I said that.

Here's a clearer way to say it: "Two events A and B, if they are coincident in one frame, are coincident in all frames."

"The death ray still hits you when you're 1/2 of the way across the Earth. This has to be true because **events which occur at the same time and same position are always the same time** and position regardless of frame.
"

ok this one "Two events A and B, if they are coincident in one frame, are coincident in all frames."
" makes a lot more sense

(unrelated) Sometimes I am glad that we live in a minkowski spacetime and not an alien spacetime based on p adic numbers en.wikipedia.org/wiki/P-adic_number else I don't think we will have nice aids such as spacetime diagrams to guide us and we will have to deal with the whole business fully algebraically

4:19 AM

If any of you guys close those cryogenics questions for being "off topic" I will likely go insane.

4:31 AM

@DanielSank can I have this program, or is it closed source?

Martin - マーチン

5:03 AM

Would the following be on regarded a good fit for your site? Do you maybe have already a question adressing that phenomenon? chemistry.stackexchange.com/questions/43338/the-color-black

user54412

5:36 AM

@Martin-マーチン Cross posted: physics.stackexchange.com/questions/227794/black-and-reflection

user54412

Whatever we do, we're not going to migrate to chemistry, so feel free to close that one.

Mikhail

@Martin-マーチン I just made a shitty reply. I hope your happy.

Martin - マーチン

@Mikhail ;)

@ChrisWhite I am going to do exactly that.

Thanks for helping me out.

6:52 AM

Dammit Ubisoft, Assassin's Creed: Indian Simulator is not fun

been running around for 3 hours and still haven't gotten Assassin gameplay

11:06 AM

Hi everyone!

I just earned the chat privilege!

Anyone active here?

12:09 PM

hmmm

Q: How do proteins perform their function

12:47 PM

@Sidarth depends on time of day

4

Let's, for example, take a ribosome. It is an enzyme that is in turn just a molecule that must follow the laws of physics. Correct me if I'm wrong, but it can be looked upon as a molecular machine made up of several pieces. What exactly makes those pieces work together? Why does the ribosome bi...

quantum-mechanics biophysics molecules interactions

It's been proposed that this sort of thing should be on topic for us. Thoughts? For people who think it's off topic, how far off? In other words, how much would need to be changed (regardless of whether it would actually be a valid edit) to make this on topic?

1:09 PM

@DanielSank That would be a useful thing to have - do you have it on github or something? I bet @JohnRennie and other frequent relativity answerers could use that.

Bass

@DavidZ IMHO this is more a chemistry or biophysics question than one about biology. These proteins are known as molecular motors, the most widely known class are myosins which are responsible for muscle contraction. AFAIK their mechanic force comes mostly from covalent bonds, so the chemistry SE seems like a good place for this question.

Well, the question is not really where is the best place for it, but whether it's on topic here

or rather, whether it should be on topic here

@DavidZ Voted to reopen. The physical explanation of biological mechanisms is the physics part of biophysics, and hence on-topic here.

Bass

@DavidZ At least with the edit it's not off-topic: What forces would move it along this strand? Is it electromagnetism?

@DavidZ ok

wassup?

can I ask a doubt on COMSOL Multiphysics FEA software?

1:24 PM

Sure, anything goes here in the chat (subject to some basic rules about civility and such)

Cool.....how can I give an Induced current equation in 3D analysis ?

ie.e, I want to write the "velocity, lorentz term " en for 3d analysis

knzhou

@DavidZ IMO it's on topic, even though it is more biology than physics, because there are aspects of the question only a physics approach can answer. In any case, it's a much more interesting question than the 10th entanglement / twin paradox question of the day.

1:43 PM

@ACuriousMind @DanielSank I'd certainly be interested to see the app ...

3:06 PM

ヽ༼ຈل͜ຈ༽ノ

huh

apparently you can have that as a YouTube username

0537

3:34 PM

lol

Qmechanic

4:29 PM

@DavidZ : This question (v3) is (besides being off-topic) too broad. It currently contains around 10 sub-questions.

user54412

@DavidZ I can appreciate the call to not exclude biophysics, but at the same time the question is rather meandering and unfocused, so I hesitate to say it's focused on (bio)physics.

user54412

What really confuses me is why some people insist only physicists are equipped to handle these sorts of questions.

user54412

If I were asking how to calculate the probability of DNA linkages breaking due to thermal collisions with solvent molecules, given that I know the structure of DNA and don't know stat mech, then sure, I might go to a physicist.

user54412

But asking how enzymes/DNA/organelles work in general is exactly what biologists do.

5:01 PM

@ChrisWhite Pretty sure biology is just carbon electron shell physics

5:18 PM

@JohnRennie I'll put it on github later today if I remember. It's pretty simple. You give worldlines in one frame and then it plots them in other frames.

0537

5:32 PM

@0celo7 I think that's organic chemistry.

@0537 And biology is just applied chemistry.

Dear person annoying me,

Please, please, please! Just stop %&^!@~# guessing and throwing mud against the wall in the hope of a pity vote or two. This site is for grownups or those who can do a good job of imitating one.

Sincerely, me.

I'd take a bright child willing to learn over some of the grownups every day, though :P

@ACuriousMind Fair enough. I would too.

5:49 PM

where is the puppet person

is he gone

@0celo7 puppet person?

@JohnRennie the one who accused us of being puppets

and DS being the master

@0celo7 ah. I assume he/she/it eventually grew up.

That they grew bored is more likely, though...

As it happens they stopped the silly posts immediately after I told them to seriously consider growing up :-)

@dmckee naming no names, but does their username rhyme with Kylo Ren?

@DavidZ If the question was along the lines of what determines the force between two molecules then it would be on topic here.

As it is, you need to know a lot of biology first to understand what the (bio)molecules are doing before you can start trying to explain their behaviour using physical principles.

6:13 PM

Mentioning Kylo Ren, is the spoiler ban

Dec 16 '15 at 5:47, by DanielSank

Please do not spoil Star Wars in this chat over the next couple weeks.

still in effect?

6:23 PM

@ACuriousMind It's been about three weeks since the opening, no? I'm supposing that we can allow vague statements like "It doesn't suck and someone dies." (my first pass non-spoiler review).

6:38 PM

Someone does die

Name rhymes with Anderson Cooper

6:52 PM

@JohnRennie Generally speaking, I think there are many good questions that will require some background information about a specific topic, and I don't think that itself should make them off topic.

Could be just a difference of opinion

Emilio Pisanty

7:07 PM

@ACuriousMind Not sure, but given loweringthebar.net/2015/12/… you might want to take it easy in case anyone takes it hard.

(Obviously not implying Daniel would do any of that, in case it needs saying.)

Mike Miller

@ACuriousMind: Gimme two weeks.

bolbteppa

"The lumped circuit approximation enables one to get around the problem of finding the actual fields in the vicinity of a circuit. The key idea is to regard the circuit as made of elements-resistors, capacitors, inductors, sources of emf" Any idea what the (vague jist of the) logic is to get from the EM Lagrangian to this statement?

In other words, understanding Kircchoff and other stuff from basic EM books using microscopic EM coming from a Lagrangian

Emilio Pisanty

@MikeMiller ↑