ELI5: How does a computer know how long a second is?

Your computer has a slice of rock in it that moves back and forth when you run electricity through it. It counts the number of times it moves back and forth, and it knows how many times it moves back and forth in one second. When it has moved back and forth the correct number of times, it knows one second has passed.

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To answer the single most asked question: When the power is off, there is a small battery on the motherboard that provides enough power to run the quartz timer, which is known as the CMOS battery. When that battery dies or is removed, the time will reset to a default value every time the computer loses power.

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ELI5: Why does multiplying two negatives give you a positive?

I give you three $20 notes +3 * +20 = +60 for you
I give you three $20 debts +3 * -20 = -60 for you
I take three $20 notes from you -3 * +20 = -60 for you
I take three $20 debts from you -3 * -20 = +60 for you

and quick note - the result is the gain or loss from where you started.

ANOTHER GREAT EXPLANATION BELOW

Think about it like this: If you film someone running forwards
(positive) and then play the film forward (positive) he is still running
forward (positive).

If you play the film backward (negative) he appears
to be running backwards (negative) so the result of multiplying a
positive and a negative is negative.

Same goes for if you film a guy
running backwards (negative) and play it normally (positive) he appears
to be still running backwards (negative).

Now, if you film a guy running
backwards (negative) and play it backwards (negative) he appears to be
running forward (positive). Even if you speed up the rewind (-3x or -4x)
these results hold true. Backward x backward = forward. Negative times
negative = positive.

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ELI5: What happened to needing "www" in front of an address?

Explaining like If you were 5:

You know when you send a package in the mail, you write the address and maybe, If the package is “Fragile” you’ll stamp “FRAGILE” all over it.
Why don’t you also stamp “NOT FRAGILE” on the packages that are not fragile? Because It’s implicit. If you don’t say anything the mailman knows It’s not fragile.

Same thing goes for the WWW. Since you can have multiple services on your domain (ex: ftp .address. com which means you want to share files; or mail. address. com which means you want to access the mail server on that domain) in the beginning you’d also write “WWW. address. com” to state that you wanted to access the HTML of the server.

As the web evolved and 99% of the average user wants to access the HTML version of the website, website owners no longer require you to type “WWW. address. com” instead, If you type “address. com” they assume you want to access the HTML version.

Just like you don’t need to stamp “NON FRAGILE” on your package, you don’t need to type “WWW”. Everyone assumes that’s what you want If you say nothing otherwise.

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ELI5: When my cat sits on my touch lamp, i can use his nose as an on/off button. How does this work?

With a touch lamp you can make a daisy chain / train of people. As far as it goes all the people will act as the touch surface. So if 10 people are connected to the lamp the 11th person will be able to use any part of the 10th person as a button ;). Similarly, if the first person is electrocuted so will all the rest. Just saying.

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ELI5: Why are the words "eleven" and "twelve," so different from the pattern of thirteen, fourteen, fifteen, etc?

This is one of those complicated etymology studies without an altogether clear answer.

Eleven and twelve are structures which show up in other northern-European languages, but the divide between using those forms and using the -teen form after twelve likely comes from the utility of twelve for trades-people.

Dozens and gross (144 or a dozen dozen) were preferred over tens for many trades for quite a long time due to their more convenient divisibility–evenly divisible by 2, 3, and 4–and this is the likely reason that the more continental European form survived in English. However, the evidence for any of it is very poor with conflicting theories even of the origins of the words.

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ELI5: Do dogs recognize that their name is their identity or do they simply know to respond when a certain sound is made?

Dogs are capable of recognizing their names, and discerning it from other sounds. Recent animal behavior studies have found that dog’s brains behave in much the same way our brains do when someone says our name. It appears that they are able to recognize that their name is not just another sound that someone is making, but is meant to specifically identify them.

Fun fact – cats have been shown to do this as well. The research suggests that cats can also tell when you’re using their specific name. The reason they often don’t react? They don’t care.

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ELI5: Why does light travel? Why does it not just stay in place? What causes it to move, let alone at so fast a rate?

Since this is ELI5, here is the really simple version without bringing spacetime into it.

The speed of anything is basically determined by it’s weight and the amount energy that is pushing it. You can push your toy cars really fast but if you try to push a real car it’s a lot harder. That’s because it weighs more. Light weighs nothing, so it moves at full speed all the time with no push at all.

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