1. ## md65536

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3. ## elfmotat

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## Popular Content

Showing content with the highest reputation on 09/03/19 in all areas

1. 3 points

## Math v physics (split from Direction of time)

Physical laws have certain properties, and you can have maths that have the same properties, but you can also have other maths that don't, including abstract mathematics that aren't based on physical things. For example, you can mathematically take apart an orange and rearrange it into two oranges identical to the original. https://en.wikipedia.org/wiki/Banach–Tarski_paradox The maths aren't restricted by the physical law of conservation of mass.
2. 1 point

## American Cheese

A bit pricey yet intriguing. Hmm and there is one for coffee too. God, I am going to die fat and with heart palpitations. But then I have rather bad experience with mail (managed to lose clinical samples long enough for them to thaw....). Also, why am I hungry?
3. 1 point

## The Official "Introduce Yourself" Thread

Unless they’ve already been banned as a sock puppet 😉
4. 1 point

## Math v physics (split from Direction of time)

Math requires that it be internally consistent. It does not require that it be compared to nature's behavior. That's why math can prove things.
5. 1 point

There are different meanings of 'belief': - postponing certainty, as one was not yet in the position to find out if something is true, but it is knowledgeable: e.g. 'I believe somebody is eavesdropping behind the door.' I can check it by opening the door and look. - metaphysical believes: things that are principally not accessible for our knowledge Today most (reasonable) people consider belief in God as belonging to the second category. That already doesn't follow then. At this moment I would say we do not know to which category of belief the origin of the universe belongs too. We know the big bang is not the final answer, but if we ever can 'look' before the big bang I have no idea. But I think it is perfectly ok to leave the question as a question, and just see and wait if science can come with a further answer. Just posing a 'belief' in the second sense seems unnecessary to me. I would say that questions that cannot be answered should not be answered, accept with 'we do not know' and maybe we will never'. Not at all. The question should arise in everybody, if he believes in God or not. Dogmatic belief in God mostly includes an unreflected answer to the question of the meaning of life. Hmmm. I would say that inconsistent beliefs about God (or gods), together with 'belief' in the second sense above, makes it more probable that none of these beliefs really say something about our universe and therefore of God (gods).
6. 1 point

## Why can't we just suck out carbon from the atmosphere?

Here is how to suck co2 out of the air. Transport huge amounts of sea water to deserts near the ocean. Fill thousands of concrete ponds to a few feet deep. Cover the ponds with transparent, convexly-lensed glass that you make from desert sand. These magnify the sunlight to create water vapor that condenses into fresh water to be transported by individual hoses to trees. No water is wasted. The trees grow and capture the co2 for hundreds or thousands of years. These oases can spring up anywhere in the world, and can grow larger over time. Making more and more fresh water, and planting more and more trees.
7. 1 point

## Trump Using Nukes Against Hurricanes ?

They must spend a fortune on custom-made hand puppets for this type of briefing.
8. 1 point

## Trump Using Nukes Against Hurricanes ?

Hopefully, one of them will explain to him that this is a dumb idea.
9. 1 point

## What is "falsifiability" exactly?

For someone banging on about clarity etc, I’m rather surprised you haven’t provided a reference. I agree that the first bit of text you quote appears pretty bad. But as I don’t know where it is from, I can’t say much more. That is a hypothesis not a theory. It is falsifiable because we can specify ways of testing it. As it happens, these show that the hypothesis is false. Which it is why it is not a theory. You seem to confusing “falsified” with “falsifiable” The idea here is that you only need one example to disprove something (eg your room without a green unicorn) but it is much harder to prove something. Let’s say you have looked in every room in your house and, yes, there is a green unicorn there (obviously, this is just to explain the point). Then you check every room in every building in your town. Yep, the hypothesis still holds. You check every room in your country and then on the planet. Still no rooms without green unicorns. But by now, thousands of new buildings have gone up; they all need to be checked. And can you be certain that there weren’t some secret or hidden rooms you missed. And what about buildings on other planets (if they exist). It is usually impossible or impractical to test something exhaustively. So science more often relies on finding a counter-example, rather than trying to confirm every possible case. Good. I think you need to go and chill out
10. 1 point

## What is "falsifiability" exactly?

It's pretty simple, really. Can you think of a way to show something is false? Then it's falsifiable. But that's a great example. Finding a three-eyed swan is EXACTLY what would show "all swans have two eyes" to be a false statement. As a counter example, arguing that the Christian God exists is NOT falsifiable. Being unobservable, there's no way to perform adequate tests. There's no way to form a prediction based on observed behavior. Almost by definition, this god isn't going to show itself because that would destroy the reason behind the faith of its followers. Why is it nonsense? A single black swan is enough to disprove a statement like "all swans are white". But if I say "all swans are black or white", I can't prove that, not even if I check every living swan. I'd have to check every swan there ever was, or ever will be, and I'd have to be sure swans didn't live on any other planet in the universe as well. This is the basis for theory, the idea that we can only accumulate evidence in support rather than "proving" an idea. It's what keeps us searching for the most supported explanations, rather than answers we decide on and never go back to check.
11. 1 point

## Why is Newtonian Gravity so accurate?

Your intuitions are good. Newtonian gravity can be derived from GR with the assumptions that: 1) gravity is weak, and 2) matter is non-relativistic. In particular you assume that the metric is nearly flat, different only by a small amount $|h|\ll 1$: $g_{\mu \nu} = \eta_{\mu \nu} + h_{\mu \nu}$ You plug this into the Einstein Field Equations (making use of the fact that matter is non-relativistic so all but the 00-component of the Stress-Energy Tensor will be zero), and you're left with the differential equation: $\nabla^2 h_{00} = -8 \pi G \frac{\rho_E}{c^2} = -8 \pi G \rho_M$ where $\rho_E$ is energy density, which we can replace with mass density $\rho_M$ because matter is non-relativistic. Note the similarity to the Poisson Equation for Newtonian gravity: $\nabla^2 \Phi = 4 \pi G \rho_M$ for gravitational potential $\Phi$. Indeed we can simply identify $h_{00} = -2 \Phi$ and they are equivalent. So using only the assumptions that gravity is weak and matter does not move fast, we obtain the fundamental equation of Newtonian gravity from GR. (The inverse-square law can be derived from Poisson's equation.) AFAIK your suggestion to replace the denominator of the inverse-square law with the interval (proper distance perhaps?) does not really have any meaningful interpretation.
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