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2. ## studiot

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4. ## Markus Hanke

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## Popular Content

Showing content with the highest reputation on 01/12/21 in all areas

1. 2 points

2. 1 point

## I need some help figuring out if this study is flawed

No, it's not really proof of anything. Tight trousers are associated with reduced fertility. Stuffing a phone into your pocket would tighten them. It's possible that it's something altogether different. If shirts with pockets are more expensive and fertility is related to good foo0d (and thus, to wealth) the correlation may be nothing to do with phones.
3. 1 point

## Blow to US Democracy -Split from: U.S. presidential election modelling

I would argue this describes fully 95% of the species, and virtually everyone here. It's why I look at these personal preferences as tools to apply to specific situations rather than hats to wear. The right tool for the right job, as opposed to wearing my hammer on my head to declare I'm going to use it for EVERYTHING. This is the power of bias. For years I've avoided direct criticism of the whole group in favor of defining exact behavior I disapprove of, yet you think I regularly use a "wide brush" in generalizing. Very instructional.
4. 1 point

## Nothing can come from nothing so something always existed!

Maybe one of the more knowledgeable folks can say if there are any theories on that.
5. 1 point

## Time, Space & the Aether

Yes, but that is only because you are in a non-inertial frame. The important point here isn't the table itself, but the fact that its presence prevents the test particle from remaining in its natural state of motion, being free fall. To put it differently, gravity "acts" on freely falling test particles (by determining their trajectories) even though a co-moving accelerometer reads exactly zero everywhere and at all times - meaning gravity isn't a force in the Newtonian sense. There are four main ways to look at this: 1. Kinematics. An accelerometer in free fall reads zero everywhere, so the equation of free fall motion is simply: $a^{\mu}=0$ If we set up a local coordinate system, we can denote the position vector of our test particle as $$x^{\mu}(\tau)$$, and the above then becomes $x{^{\mu }}{_{||\tau \tau }} =0$ wherein the || denotes covariant differentiation, since we are in a curved spacetime. The solutions of this equation of motion are geodesics of spacetime, being free fall world lines. No need to reference the concept of "force" anywhere here - which would be difficult, since a=0 implies F=0. 2. Geometry. Rewrite the above equation as $\nabla _{u}\vec{u} =0$ This is the same equation as above, just written in terms of 4-velocity instead of acceleration. The geometric meaning of this is that free fall world lines are curves in spacetime that parallel-transport their own tangent vectors. Again, the concept of "force" does not come into this at all, it is purely geometric. 3. Pseudo-forces. Start with the equation in (1), and write out the covariant derivative fully in component form: $\frac{d^{2} x^{\mu }}{d\tau ^{2}} =-\Gamma ^{\mu }_{\alpha \beta }\frac{dx^{\alpha }}{d\tau }\frac{dx^{\beta }}{d\tau }$ Again, this is the same equation, only written out fully. The left hand side is a Newtonian acceleration, the right hand side can be interpreted as pseudo-forces, which originate from the fact that the background spacetime is not flat. This is a valid way to look at this for massive particles; however, the right hand side of the equation taken on its own is not covariant, so it depends on the observer, and one can always locally eliminate the Christoffel symbol by going into the rest frame of the falling particle. Of course, this interpretation actually fails in the case of photons, since the very concept of Newtonian "pseudo-forces" is meaningless for massless particles. 4. Least action. Free fall world lines are those for which total proper time is an extremum, i.e. they are the longest (or shortest, depending on sign convention) possible world lines between two given events: $\tau =\int _{C} ds=\int ^{B}_{A}\sqrt{-g_{\mu \nu } dx^{\mu } dx^{\nu }} =\text{extremum}$ This again does not require any notion of force. If you look at all of the above ways to consider the geodesic equation (which is what this is), then you will find that the common factor in all of them is not force, but geometry. I have parametrised the test particle's world line by proper time here, but everything remains valid if you replace this by a more general affine parameter, in order to include massless test particles as well. Do note though that the "pseudo-forces" way to look at it is highly problematic in the case of massless particles. The point I am trying to make is that it is best to look at gravity as a geometric property of spacetime, since that is the most general description that works for any test particle, and any observer, and does not require any extra concepts.
6. 1 point

## Converting Copper sulfate

CuCl is easy. Add sodiumchloride or hydrochloric acid and a strong reducer like dithionite or Ascorbinic acid to the coppersulfate. You will get a white precipitate. Manganesechloride : Add sodiumhydroxide first to manganese sulfate , you will get a sludge of manganese hydroxide. Filter it and wash it. Then neutralize with hydrochloric acid.
7. 1 point

## NCBI database and Covid-19

Well, I am certain you are wrong. I have looked at the sequence days after it was published mid-January (well, and the rest of the community even earlier). I suspect you might have looked at the revision dates rather than the original posting date (I remember that there were a few bases being corrected after more sequencing, but I might be misremembering). There are also many more sequences out there and perhaps updates to RefSeqs. But either way, your premise is clearly wrong. Edit: I quickly checked the entry: the date in the header of Genbank entries signifies the date of last modification, not the date of submission and I think that is what you looked at. It is the right sequence, though, but you can look at the history and see where it was originally posted. IIRC it was originally submitted early January and I think it was available about a week after. Double edit: apparently lack of sleep significantly reduces my already poor spelling abilities. I should call it a day at some point.
8. 1 point

## Political Humor

Not funny at all; kind of sad, actually. During lock-down, I've been watching the final season of that new show … The United States of America.
9. 1 point

## Tech Giants Shutting Down Violent Social Media Cesspools

I think popular entertainment and the distorted representations of "reality" it provides - probably contributes; people spend a lot of time in the fantasy land of media news, entertainment and advertising - and the lines between those are increasingly blurred. They are also more and more tailored and targeted, to engage the hopes and fears and beliefs various sectional groups of people hold, such that any editorial balance is not within the 'feeds', but with the diversity of different 'feeds'; increasingly our preferred views get reinforced unless we make an effort to sample other sources of information. I think our societies have always run in step with and promoted rather fanciful and self serving and self congratulatory stories of "how things work"; heroes rising up, taking matters into their own hand, saving the innocent, the day, the nation, and exacting revenge, is a popular theme anytime. But with partisan media - who was it predicted the political parties of the future will be media companies? - other media telling it differently to a different audience are portrayed as enemies and untrustworthy, preventing, not enabling an informed, balanced view, let alone treating differences as legitimately different opinion. The supposed Constitutional "right" to take up arms against their own government may add to willingness of fired up citizens to engage in direct action in the USA, in ways other nations with elected governments and rule of law do not - I say "supposed right" because it would only be a right ever upheld if the revolution succeeds... making the USA no different to any other nation, where insurrection is always criminal, with the notable exception of where it succeeds.
10. 1 point

## Nuclear Saltwater rocket!

This short video details the idea of a nuclear saltwater rocket. This rocket is pretty much a continuous nuclear explosion propelling the space craft. The vid is short and informative not to mention wild! Should development of such an engine be pursued?
11. 1 point

## Random Mutations and Biological Evolution

They are not. Most mutations are neutral and not selected against. That is the definition of neutral. They keep them. This is clearly not the case, a huge chunk of our DNA are areas that are duplicated, contain viral insertions and/or have otherwise accumulated bits and pieces. Typically there is no strong selection for eukaryotes to maintain a small genome size. The eukaryotic amoeboid Polychaos dubium has a genome size of 670 Gigabases (compared to 2.9 of the human genome), for example. In prokaryotes there is some benefit of keeping genome sizes compact, in part because it allows faster replication time.
12. 1 point

## Mystery Carbohydrates??

The term 'Carbohydrates' is strictly (c.H2O)2 in Chemistry. However this creates carbohydrate 'units' which form the basis or backbone of many bio-molecules. These are therefore part pure carbohydrate, part something else. Sugars and so forth are pure carbohydrates, but the bio-molecules are not. So the preparers of the food are giving you the % in terms of bio-molecules and in terms of those parts which are pure carbohydrate.
13. 1 point

## Metal and iron dissolving

That's a heftly 7 inch lump of 1 inch rebar you have shown. It doesn't look stainless, which would offer good resistance to hydrochloric or sulphuric acids. But stainless rebar can look dull like that. It is not higly polished like cutlery. It looks more like standard high tenisle steel with the normal black oxide coating. The black oxide is what give cast iron its high corrosion resistance. You would have to expose clean metal to get the solution going. Even then, if it is a high silicon steel it might still be resistant. Why do you need to dissolve such a large amount ? Would some shavings not do ?
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