How does diet soda have 0 calories?

There are several different types of artificial sweeteners. But generally they are much sweeter than regular sugar, and some cannot be broken down by the body.

For example, Diet Coke is sweetened with aspartame. Aspartame is a protein which tastes 200 times sweeter than sugar. Aspartame has 4 calories per gram, just the same as regular sugar. But because it's much sweeter, you require much less aspartame (1/200th) to make a drink that has the equivalent sweetness. If 1 can of regular Coke has say 150 calories, then 1 can of Diet Coke would have less than one calorie. So labeling laws allow Coke to label it as having 0 calories.

Another artificial sweetener is Splenda. It also tastes much sweeter than sugar, so you need to use less of it. But also, Splenda cannot be digested by the body so it effectively has 0 calories.

What is Multiple Sclerosis, also known as MS?

Around the nerves in the brain, there is a covering called myelin. This substance acts as a sheath in the same way wires have sheaths. It helps to keep each 'wire' isolated so signals don't get crossed.

With MS, for some reason, the body's immune system sees the myelin sheath as a foreign entity, so the immune system starts attacking it just as they would with a virus or bacteria.

The "sclerosis" portion of the MS name deals with scarring. Over time, as the mylein sheath surrounding the nerves is attacked and healed over time, over and over again, scarring in the sheath starts to form which can end up getting so thick that it slows or completely blocks signals trying to go through that particular nerve. Many people with MS over time end up losing the ability to feel certain parts of their body, or lose control of those parts of their body entirely.

There is no known cure, and scientists aren't completely sure what causes it to begin with. There are of course medications available for people suffering from MS, but the focus is more on slowing the progression of the disease, not stopping it.

What are numbers and why do they do such a good job of explaining the universe?

Great question. For starters numbers are an abstraction. In reality, things just are. There is no number, because there are no category of things that can be repeated. No apple is truly the same as another and therefore a person cannot have more than one of anything. The real world is infinite in its complexity.

However, the human mind is not. The human mind is simple and must make assumptions and estimations to get along. The human mind considers an apple and another apple and doesn't see their infinitely distinct reality. The mind sees an abstract simplified token - just an apple and another apple. Two apples.

This is a kind of magic. Representing several things as though it was a modified version of one thing, frees up the mind to do so much. It allows us to store large amounts of information outside of our bodies.

The simple human mind can only really conceive of about 3-6 things at once. If a person without counting is asked which group is larger and is shown two groups, one with 33 apples, and another with 31, is extremely difficult to tell. But with numbers a person can count. They can set aside the reality of the apples and use several kinds of abstract representation to tell how many there are. They can arrange the apples into groups of three - which can be easily identified - and use their fingers outstretched to represent their place in counting each group. This is storing information outside of oneself.

This is a profound transformation. It can be shown that numbers are a kind of representative logic. Adding the ability to store information outside the human body transforms humans from just an animal into turing complete. Turing machines can solve any problem that is computable given enough time.

To the extent that we are right that one thing is like another thing, abstraction and counting save us a lot of brainpower. It's a kind of compression. When we use numbers to represent things, we discover that there are certain logical properties that can rearrange these groups (numbers) in ways that are more understandable without affecting their accuracy or changing the number at all. For instance, three groups of 10 apples is the same as 30 apples. Multiplying doesn't do anything to the groups but it does make a simpler token to represent it in our memory (30 as opposed to 3 sets of 10).

These conceptual simplifications let us represent other relationships we discover. Like the fact that planets (from the Greek for wanderer) seem to look like stars that moves throughout the sky. By putting numbers on how much they move we can compare this that are hard to directly observe - just like the large groups of apples. And we can store that information outside of our minds so we can compare it over long periods of time.

Comparing these numbers lets us discover patterns that describe how the planets behave like Newton's equations of motion and gravitation. What's more, they let us predict how they will behave.

The most interesting and readable author on the subject is Bertrand Russell in his book Introduction to Mathematical Philosophy.

Why do Americans celebrate Columbus Day despite Columbus never setting foot in their country?

Columbus is often credited with establishing European contact with the Americas as a whole, even though he didn't discover the region or set foot in what is now the USA.

Columbus Day was largely pushed on Americans by Catholics (and some protestants) who recognize Columbus as a key figure in the worldwide spread of Christianity.  He is also celebrated by Italian-Americans of which there are many.

Generally, Americans "celebrating Columbus Day" just means they take the day off.  People don't really celebrate Columbus outside of specific communities which are largely Catholic and/or Italian.  Some states don't even officially recognize Columbus day.

If human civilization ended tomorrow, how long would it take for all evidence of our existence to disappear?

The longest lived structures would be large stone megaprojects like the Pyramids, the Great Wall of China and Mount Rushmore. These would outlast any other kind of composite structure no matter how robust, with the possible exceptions of nuclear waste sarcophaguses and some specialized bunkers, like the Svalbard Global Seed Vault. These could last easily centuries without maintenance and still be recognizable, but not more than a few thousand years. Common made things like teapots, cellphones, cars, bridges and skyscrapers would all be equivalent to trash in their longevity, due to being made of thin, refined parts and limited design lifespans.

The longest lived human-made structure would likely be the leftovers from the Apollo missions on the moon. These could remain in a recognizable state for about 50 000 years, because the Moon is so geologically inert. There's a chance it could be accelerated by a random asteroid or two, but it's a slim chance.

Much archaeological evidence would continue to suggest our existence for many thousands of years, under a few meters or few dozen meters of dirt: building foundations, glass, landfills and collapsed tunnels could be around until they broke down into the crust and did something interesting like fossilize (or whatever  CRT TVs and daipers do when left buried for ten thousand years). This kind of evidence, if it could be found by a future civilization, would still be around until our continents shifted about so much that the landmasses we know and love were gone completely and sunk into the Earth's interior. That could take many millions of years.

All satelites and space missions would either get covered in dirt or be perturbed and crash within a century, with the notable exceptions of the Voyager probes, New Horizons, and possibly a blastplate from Operation Plumbob.

Why do we feel like throwing up when we see someone else vomit?

There is no definite answer to this one; but here's an evolution based theory that might explain this.

It goes back to the days when an entire tribe would hunt and eat the same thing. So if one person vomited, then you would want to vomit too because you ate the same thing.

Even though we all eat on our own now, the impulse remains to vomit when you see someone else do it.

Why do athletes take ice baths?

The benefits of ice baths have become more ambiguous since first introduced. At its primary level, it's pretty self-evident. Cold things will help reduce swelling and possibly inflammation. It desensitizes us to a certain feeling of pain and soreness from repetitive or intense exercise.

However, for athletes looking to increase adaptation/strength, inflammation is actually helpful for muscle repair. In a study conducted where people did a 3 month strength training course, the participants that used an ice bath (over gradual cool down) for repair noted reduced swelling and overall soreness but also made smaller gain in muscle mass.

Overall, for athletes at their prime, ice baths may be useful for quick recovery between events (i.e. back to back games) but probably not if they want to get stronger long term.