What's the point of language?

Generally speaking, we use language to communicate ideas and instructions to other humans. That's why language exists - because we can't read each other's thoughts, we use words to communicate the ideas contained within our brains.

So if we are thinking of something, at some point we need to communicate that information to someone else. In order to do that, we need to use words. And what is faster:

To have an abstract brain state and then try to convert that into words on the fly while talking to someone?

Or to format your thoughts in language to begin with so that when you need to communicate them to someone else, you already know how to?

They don't.

Every single piece of food is unique. So no one knows exactly how much of anything is in anything.

They're pretty close though. They can control down to the gram level how much of anything is in any of their products, and they can usually be more accurate than that.

From there, they can look up the caloric contents of their ingredients and calculate roughly what the values are. And as with their food items, the exact caloric content of a particular ingredient isn't known, but we have a very good approximation for these things. It's not NASA accurate (you won't do the equivalent of hitting a small piece of moving rock with an even smaller chunk of metal from 23 million miles away), but it's accurate enough for you to figure out if you can have that third cookie and still hit your weight loss goals (you can't).

This is a tricky one, but I'll try to keep it simpler. I'm not certain that what I'm about to say is 100% consistent with the math of relativity, but it's reasonably close enought to at least understand why time dilation occurs.

With that out of the way:

First, the speed of light is not really about light. The fact that light travels at that speed is a consequence of the nature of photons. The speed of light is the ultimate speed limit of the universe - you could call it the speed of causality more accurately. In fact, in a sense everything travels at the speed of light - that might not seem accurate, but I'll explain more in a little bit.

Second, what is speed? It's how fast something is moving in a particular direction. All movement is directional - you don't just arbitrarily go fast. You travel along a path. Typically, we think of this path as three-dimensional. If you're flying in an airplane, for example, then relative to a stationary object, you're moving upwards at a certain speed, to the left or right at a certain speed, and forward at a certain speed. Add those together according to some relatively basic math, and you have your overall speed and direction of travel.

Third - what I just explained isn't actually correct, because it ignores something rather huge that all of us take for granted - time. You see, we don't travel a three-dimensional path. We travel a four-dimensional path. And that fourth dimension is time. For most objects traveling at the speeds most humans deal with, time is actually the largest part of our velocity. That's why time seems to pass at the same rate at the scales that you're used to dealing with - the differences between your time velocity and something traveling at 60 mph is so miniscule that it's impossible for a human to notice it.

Fourth - remember how I said everything travels at the speed of light? Well, that's why time dilation is a thing. Your total velocity through four dimensions must remain constant. So if you are traveling through space faster, then the only way for you to do that is to travel through time slower. So as you speed up, your experience of time slows down. However, because you have mass, you can never actually reach the speed of light. What happens instead is that as you get faster, the extra energy actually makes you more massive.

Incidentally, because photons travel at the speed of light, they don't experience the flow of time. From the point of view of the photon, its entire lifespan (from the moment it's emitted until it's absorbed by another particle) passes instantaneously and simultaneously. This happens because photons don't have mass, and so their velocity in the "time" dimension is 0.

Because things get in the way.

Mountains, rivers, hills, buildings, ravines, forests and more are just some of the things that get in the way of roads just being straight. Most of the time, it's much cheaper to build around something instead of going straight through it. Other times, you have no choice but to curve around it; it doesn't matter how much you'd like to make the road straight, you're not going to get permission to tunnel through Notre Dame cathedral.

Bridges are orders of magnitude more expensive to build than regular roads, so if you can avoid building a bridge over something, you will. Tunnels are even more expensive to build. Both tunnels and bridges are more prone to collapse in the event of natural disasters, and both of them introduce areas of natural bottleneck in traffic flow; if it turns out that you didn't make the tunnel wide enough for the amount of traffic you need to accommodate, it's much more expensive to widen the tunnel later on, and you'll likely have to shut down the tunnel while you're widening it.

Of course they do. Anything containing carbohydrates will burn. For that matter, almost anything organic will burn.

Grapes have a very high water content, so they may require a little bit longer to ignite than something dryer, like wood. But given sufficient heat and/or time, they absolutely will burn. Once the water has evaporated out, the sugars in them will burn quickly and energetically.

In fact, if you pop some grapes in the microwave, you can make them burn spectacularly - they'll spontaneously create visible plasma.