Physicists can't even reverse calculate the diffusion of a drop of ink in a glass of water but they think they know...

physics offers beautiful accounts of nature
don't be hatin

You were saying?

this one always blows my mind, like I still expect a different ending every time.

It's not the same lmfaooooooo

Is this real? After this thread it made me laugh because I was like "oh they're just gonna reverse the video-- wait did they reverse it?"

Explain this shit

I dont see the significance in this. Physics have found multiple boundries within the existing knowledge, its why phycists keep studying the unknown.

What is Stochastic Calculus

^

bigu bangu is simple , all the brownian bullshit happening when ink diffuses in water is not .
u can make simulations and shit of it .

they didnt reverse it .also notice the before and the after isnt exactly the same .
my thermodynamics professor showed this to us when discussing why some processes are 'theoretically reversible' and some are not . the reason this wouldnt work in water is that the brownian motion mixes shit .
if you had some theoretical viscous fluid in near 0 temp with nearly no brownian motion you would be able to reverse any mixing you did by precisely retracing your steps in reverse .

that's not diffusion

>can't even reverse calculate the diffusion of a drop of ink in a glass of water
Sigh.
Even if the universe were deterministic (and it;s not), you still couldn't necessarily "reverse calculate" anything.
For example, a computer program is completely deterministic, and far simpler than you example, but there are functions (like hashes, len(), etc) where you can't determine the input parameters by examining the returned output.

But when you get really close to the big bang their understanding falls apart.
When you reach the electroweak scale, does the Higgs mechanism just stop working? If so there should be singularities is spacetime from when the symmetry was broken. If you think of it like a magnet going from random spins at high temperature to magnetised at low temperature, you don't necessarily have all the spins pointing in the same direction, you might have all the atoms on the left pointing up and on the right pointing down, with this domain wall between them. The same thing should happen as the universe cools and the electroweak symmetry is broken, but nobody has ever seen a cosmic string or domain wall. You then have the same problem again if there's also grand unification, and at very high energy you need quantum gravity, and we don't even know what that is in theory. The best bet is string theory, but Veeky Forums is well aware of the problems there.
I think the furtherest one can say we've pushed time back is something like 10^-18 seconds after the big bang, but I don't know where I got that figure from.

>and the same reasons you cant predictively model the reversed history of the universe in a theory
You're throwing out the baby with the bath water.
Even if we knew the position and momentum of every particle in the universe, you still couldn't trace everything backwards, collision by collision even one second.
(never mind that these particles don't have an exact position and momentum)
But that doesn't mean you can't produce a general description of what the universe was like yesterday, last year, or 13.x billion years ago.

>But when you get really close to the big bang their understanding falls apart.
You've defined "really close" as where ever their understanding finally breaks down.
Which is bound to happen, because the closer you get, the more bizarre shit gets.
You didn't just move the goalposts, you built them around the spot you wanted in the first place.
Also calling OP out as a troll.
Nobody could actually have this kind of high expectation of extreme accuracy of understanding, atom by atom right back to zero.

>hashes

are you retarded ? of course you can, why do you think we update hash functions every once in a while ?

>You've defined "really close" as where ever their understanding finally breaks down.
The universe is billions of years old and we can trace back the history of the universe back to 10^-18 seconds after the big bang. The ratio of the age of the universe this number is like 5*10^35, which is objectively massive; there are few other dimensionless ratios in physics that are so large, it's comparable to the ratio of the strength of the strong force to that of gravity. Every physicist would say that gravity is incredibly weak compared to the other forces, so much so that its explanation is one of the most major unsolved problems in physics, so it's fair to say that another ratio of a similar scale qualifies as "very large", so it makes sense to say we are theoretically "really close" to the big bang.

Another option would be to look at the ratio of the size of the universe at 10^-18 seconds to its size today, or temperature then and temperature now. Any measure of (things now)/(things at the smallest time we understand) is going to be massive (or tiny, depending on what it is you are comparing) when compared to other physical ratios, like the electron mass to the proton mass, or the mass of an atom to that of a lump of coal.

>are you retarded ?
Are you?

Hashes contain less bits than their input, ther's a loss of data.
Just like len(), there's more than one possible input for each possible output.
len('cat') is 3, len('dog') is 3
Sure, you can always find an input value that produces 3, but you'll never know if your input value matches the actual input value.

>The universe is billions of years old and we can trace back the history of the universe back to 10^-18 seconds after the big bang.
>it makes sense to say we are theoretically "really close" to the big bang.
It would also make sense to call 5 minutes "real close".
You chose 10^-18 seconds because that's where our understanding breaks down, not because 10^-17 doesn't qualify as "real close".

how do you know there isn't some memory effect of particles in spacetime ?

if such a phenomenon exists, you could know which imput matches your output by simply observing the memory left on the device which produced the output

it's not because you can't do it that it's impossible

>Even if the universe were deterministic (and it;s not)
wew

>It would also make sense to call 5 minutes "real close".
Indeed it might, what's your point? If 10^-18 seconds is the closest we can currently understand (and I don't think that's the case, I don't remember the details but I think that's the furthest we can actually confirm experimentally), whether or not that point can be considered "really close" to the big bang is independent. 5 minutes after the big bang the universe was a very different place, so I'd agree that we could also call that "close", but not as close as 10^-18 secs.

that's just rotating and stretching 3 drops at different radii. they never touch let alone mix

Those times are matched to observed energy density and current inflation rates of the Universe. Its not that we traced back the distribution of matter to right after the big bang, but that we can work out that after a certain amount of time, there is a qualitative change in the behavior of the fields that exist.

Lrn2cosmology

>how do you know there isn't some memory effect of particles in spacetime ?

>sounds like a teapot argument to me.

...

>fucking CS majors

its because of the time evolution of density of states, you dipshit, convoluted as well with uncertainty and chaos. you cant work the solution backwards simply by knowing the final state and the underlying laws.

Bohm and his implicate order. He was a genius imo

>how do you know there isn't some memory effect of particles in spacetime ?
1) My whole point was to show OP can't assume a system is time reversible just because it's deterministic.
2) The universe isn't deterministic anyway.
3) Your conjecture is unfounded.

On a computer you could look at the status of the registers at the end of the len() calculation, and work back from there.

Why do you think that the universe loses information? It seems intuitive to me that information, like energy, would be conserved.

>>sounds like a teapot argument to me.
>3) Your conjecture is unfounded.

everything is made of mass or energy

if you have the stress-energy tensor of the entire universe right now, as well as the gravitationnal field of every single point in the universe, you could theoretically reverse calculate everything to t=0

this is because mass and energy do have a memory in spacetime which is called "gravitaionnal waves"

of course, this would require an infinite power of calculation, but it is theoretically possible

>2) The universe isn't deterministic anyway.

according to your interpretation of QM.

>On a computer you could look at the status of the registers at the end of the len() calculation, and work back from there.
That's just generally wrong because that's not how shit works.
But here's a simple proof: What if the input string was long enough to have more bits of information than the registers contain?

>Why do you think that the universe loses information?
You can start with eggs and make an omelette, but you can't start with an omelette and make eggs.
google.com/#q=arrow of time
google.com/#q=gas in a box
en.wikipedia.org/wiki/Entropy_in_thermodynamics_and_information_theory
en.wikipedia.org/wiki/Entropy_(information_theory)
en.wikipedia.org/wiki/Landauer's_principle

>if you have the stress-energy tensor of the entire universe right now
You can't put all that information in one place.
It's just not physically possible.
google.com/#q=light cone

I'm pretty sure you'd still be wrong anyway, see: ) The universe isn't deterministic anyway.
>according to your interpretation of QM.
According to QM without the "interpretations", any collision between 2 particles is NOT time reversible.
QM is a huge problem for Veeky Forums types.
Anybody who wants to seek out the answers to the big questions is bound to be upset when we get to the chapter in the book where there are some unanswerable questions.
Never mind experimental evidence, "I refuse to believe God plays dice with the Universe".

>big bang
How dare you to doubt. It is TRUTH. You hear, TRUTH

Nice try, but Genesis and the Big Bang aren't comparable, since only one has supporting evidence.

bump

>bumping a shitty, dying thread

>big bang
>evidence
pick one

>pick one
I know christians love to cherry pick

thanks for bumping

Who tell you that i'm crhistian. I'm an atheist who not worship the church of sciene, the most cancerous religion in the world.

Ok, but don't come knocking on our door for the chemo then.

ok one, arent these religion vs. science posts not allowed in Veeky Forums and two, you can't cherry pick two problems and compare them, those deal with two entirely separate problems

brainlet detected

> physicists can measure the biggest single event ever but they can't "reverse calculate" minute occurrences such as a drop of ink in a glass of water

>>physicists can't even reverse calculate the diffusion of a drop of ink in a glass of water but they think they know what happened right after the big bang

Of course they can.

"Well, we're pretty sure that at some point there was a drop of ink not mixed in with the water."

This is approximately the same level of detail on which we "think we know what happened right after the Big Bang"