/sci/ - Science & Math

>>11401118
Do you notice this two subscripts? Einstein famous equation for general relativity is basically an equation for 4x4 matrices. If you happen to know that these are not just matrices but tensors, well, change of basis in vector spaces is one of the fundamental notions in tensor definition. Source: Spacetime and Geometry, Sean M. Carroll.

Here's a question for the real, non pop-sci anons.

In General Relativity, what is the relation between pressure and energy density? When is it useful to express pressure and when is it useful to express energy density? Are they interchangeable? I assume it's something to do with what you place as the components in the stress-energy tensor, but beyond that I don't know.

>>8402110
but then the LHS should be dE/dc and it's not really useful; i know you wanted to make a joke, idc.
>>8402085
can't really decide on my favorite equation. i really like the einsteinian field equations or the field-strength tensor formulation of the maxwell equations

>>8192324
Then you don't know anything about GR or dark energy. The cosmological constant was part of GR from the very beginning. It is a single parameter. It is consistent with all the data on dark energy to date.

>phys.org/news/2014-12-alternative-explanation-dark-energy.html

>An alternate Lorentz transformation, Absolute Lorentz Transformation (ALT), has similar kinematics to special relativity yet maintains absolute simultaneity in the context of a preferred reference frame. In this study, it is shown that ALT is compatible with current experiments to test Lorentz invariance only if the proposed preferred reference frame is locally equivalent to the Earth-centere non-rotating
inertial reference frame

Advocating geocentrism in 2016 is quite a stretch. But also note he's fitting a single observational test. He ignores BAO, flatness, the ISW effect... This is not a model of equal explanatory power, it hasn't even been tested against most of the probes of dark energy.

what's the point of the so-called 'law of everything', the ultimate physical theory? the unifying theory of the universe?

Imho it's just a delusion; from a philosophical viewpoint, wouldn't it be inferred from a set of axioms given for granted? how can that be 'the end'?
Physics is an open field per se. How can it become a closed theory i.e. how can every physical truth be derived from the axioms?

Am I missing something?

I just came back from visiting a tribe in the heart of Africa. One look at these scribbles and I knew that they couldn't even fucking count. Anyone solve that problem with the half-square yet?

>>7373865
They are connected like this.

>this single equation is actually 10 equations

What are those 10 equations, /sci/?

Gravity, by Albert Einstein.
One of the most beautiful formulas out there, which explains the behaviour of spacetime when you put a mass on it.