Okay. Imagine a sound. A simple 'ting' from your phone. Sound travels in waves, you do know what waves look like, right? They're like recurring crests and troughs; up and down respectively. So, for the sake of this example, let's assume that the wave the sound 'ting' makes is one crest and one trough. One up and one down. What noise cancelling earphones do is create the opposite waves of that sound that just entered into them from your environment; which is 'ting' in this case. The earphones will recognize that the wave signature of this sound is one crest and one trough, so what it will do is create one trough and one crest (in that exact order), which are opposites of the 'ting' sound. Then it's going to place this newly created sound over the one that's coming from your phone. When you superimpose both of them together, you get a resultant zero and like that, you end up with noise cancellation.

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Edit: This explanation may seem a little vague, or I should say 'impractical'. If you're free, have some time, do watch this video to truly see this happening in real time.

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Thank you sm for taking out the time to reply!!

>Wait, so you're saying things in orbit are just endlessly falling?

That's exactly right.

Fun fact: If you want to go into space, the key problem isn't going high enough, it's going fast enough. If you don't go fast enough, you'll fall down and hit the earth. But if you go fast enough, you'll miss the earth and you'll be in orbit.

https://what-if.xkcd.com/58/

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Thanks for the answer!

Well, the reason and logic behind it are in the proofs for it, of which there are several. I like this one:

https://upload.wikimedia.org/wikipedia/commons/thumb/7/7c/Thales%27_Theorem.svg/180px-Thales%27_Theorem.svg.png

Since OA = OB = OC, ∆OBA and ∆OBC are isosceles triangles, and by the equality of the base angles of an isosceles triangle, ∠OBC = ∠OCB and ∠OBA = ∠OAB.

Let α = ∠BAO and β = ∠OBC. The three internal angles of the ∆ABC triangle are α, (α + β), and β. Since the sum of the angles of a triangle is equal to 180°, we have:

a + (a + B) + B = 180

2a + 2B = 180

2(a + B) = 180

a + B = 90

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That was my immediate takeaway, too! Everyone else is giving real answers and I'm like r/holup

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Muslims believe messiah is yet to come and messiah is Jesus himself.

The proof is the "reason and logic" behind it. I understand what you're asking, but that's just not how math works. You want some pretty, intuitive reason for why it is true, but not every proof in math is elegant like that. Plenty of things just work becuase you show they do, and it's not always pretty, clear, or obvious. Sometimes you make a bunch of reductions and inferences, most of them seemingly completely unrelated, until you go from what you know to be true, to what you want to prove to be true. And it's not pretty, and it's hard to follow, and it challenges some people's notion of math being this elygant, aesthetically pleasing set of rules that are somehow hidden in the universe, and we have to discover them.

That's not how math works. It wasn't hidden in the world by God. Humans made it up, and sometimes, even if we start from something simple and pretty, and we end at something simple and pretty, the journey may be complicated and ugly. And we just have to deal with it.

So yeah, you can look up the proofs online, no need for someone to transcribe them here, but there's no guarantee you will like them. They are not meant to be elegant, they are just meant to be correct.

It does not assume that. Maybe it doesn't work for you, but I can see from this thought experiment, without needing the standard proof, that it can only be a rectangle.

If you need some interim steps between looking at the image and concluding that it is a rectangle (getting nearer to the proof that OP specifically said he didn't want) you can imagine trying to deform the quadrilateral to vary the angles while still maintaining the vertices on the circle, you can see that this is impossible. The quadrilateral is fixed. Looking at the symmetry again shows that all the angles are right angles.

Since the starting triangle was a random angle in a semi-circle, the visualisation applies to all such triangles.

Can you not see this without needing an algebraic or verbal proof?

No, razors go dull because the hairs will wear down the sharp edge, making it more blunt. Most razors use stainless steel, so if they're rusting on you (rust will be visible), then you're doing something wrong (e.g. using the same disposable blade for too long, not properly drying, etc.)

You should never, ever shave with a rusty blade.

There are two forms of noise cancellation. Active and passive. Passive essentially means just blocking sounds from getting by such as how over the ear hearing protection works. Active uses electronics and math. The active method is fairly simple to explain though may be more ELI 17 due to geometry and sinusoidal waves. A microphone picks up the ambient noise, and reproduces it in the speaker 180° out of phase which in turn nulls the sum of the noise’s amplitude. The out of phase thing, just means there is an ever so slight delay (which is dependent on the frequency).

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I served in Iraq during the ‘00’s and on particularly hot days, after patrols and convoys, we’d go to the medics for a bag of IV fluid they’d keep slightly chilled. Holy holy! The relief of cool fluid directly into the veins and feeling it move from my arm throughout my whole body was awesome!

Then the sun has negligible gravity over you.

The only half decent answer so far... Some more points that seem important.

Judaism, Christianity and Islam are all monotheistic religions. That means they insist people worship only one god - in fact, they deny the existence of any others (though this wasn't always the case for Judaism).

Islam, Christianity and Buddhism are "universal" religions - believers believe that the religion is for everyone, and that they have a duty to spread the religion. This is not the case for Judaism.

Jews follows a (complex) set of laws and rules (although how strictly they follow them varies a lot). Muslims follow five key rules, like charity and regular prayer, though they have some of the same taboos as Jews, like not eating pork. Christians don't place this same emphasis on specific rules or even on behaviour. Generally what's most important is belief - belief in God and in Jesus as saviour.

If you do or believe the right things, when you die your soul will go to heaven (though you might have to go through purgatory first).

Buddhists believe that the world we perceive is an illusion and that the goal of life is to free ourselves from this illusion - what they call "enlightenment". They believe souls are reincarnated over and over until they become free.

Buddhists generally believe in a range of gods, demigods and mystical beings, who can help or hinder people on earth or in achieving enlightenment. Buddhism is very "syncretic" meaning it mixes easily with other religions, like Hinduism, Taoism and Shintoism.

Yes, calculated to get just the right angle and speed to be missing. I don't think thats endless though. As in, most satellites will eventually crash down anyway. Even the international space station has to fire up its boosters sometimes to stay in the right orbit angle.

Ah, late night minor error. Higher Frequency, Shorter Wavelength.

Because simply "Northwest" was already in use, historically, to refer to the Northwest Territory of the USA or, even today, the Northwest Territories of Canada.