We use the big sloppy category "fish" to describe all kinds of creatures under the sea. It's like if we bundled together all the chimps and certain kinds of birds and maybe one mushroom and decided those were all called arbs because they like to live in trees. It's a useful word in the real world, but the category doesn't map cleanly to any evolutionary branch

5. The moon. It has significant gravity and has historically attracted much of the debris headed our way, and thus has more craters to be visible.

I didn't see rules against it, and the post was an attempt to rectify a different post by another user who posted a "loaded question" by making the question more clearly worded, in order to express a question with goals of receiving a factual response. Refer to this post for more clarity.

It would be a shame for people to miss out on information because of a misworded prompt or question.

I’m having trouble reconciling some of these facts, you had such a great explanation maybe you can help me understand.

If time slows down the closer you are to a black hole, the light is reaching you slower (red shifted), but I remember reading that light travels the same speed regardless of the point of view. How can light redshift but still travel the same speed?

It's a pretty fun thought experiment to make up a value and pretend that this value is d(sign(x))/dx at 0, then try to run through some normal calculus with this new constant.

Why are you answering your own question?

Please elaborate

Mudskippers have more rigid gill plates that don't collapse, and do the whole "breathe through my skin" thing that frogs do too.

Bettas have an organ called the "labyrinth" behind the gills that they suck air into like a false lung and then bubble out later.

Corydoras Catfish eat the air and absorb oxygen in their digestive system.

And of course lungfish are close relatives of our own ancient ancestors and straight up have lungs, but decided against the whole land thing.

Leave it to Americans to reinvent trains in a super complicated way.

If the car in front of you starts getting the air moving by driving through it, it takes less energy for you to have to push the air so that little extra energy turns into a little extra speed. If you watch motorcycle racing or car racing they do it all the time. Sometime 5-15 mph difference..

Less resistance means less work you car has to do. The physics are the same on racetracks or roses and the distances between cars where a slip stream works are greater the faster you go so it usually isn’t worth the risk at high way or normal road speeds..

Lets say your a freshman (car) in highschool. When the bell rings you've got 5 minutes to get to your class on the other side of the building. But since the bell rings for everyone the hallways are immediately packed with other students (air) and your little scrawny self has to push through everyone else (air resistance). You make it to class but your exhausted having to push through everyone to make it.

Now the next day you realize that one of the lineman (the truck) on the football team gets out of class right next-door and he's heading in the same direction. As he walks, the other students (air) move or get pushed out of his way and then eventually fill back in after a couple feet. You realize you can let him do the hard work of clearing out the other students and then your just follow him close enough that the other kids havent had a chance to fill back in behind him. Congrats! Your using his slip stream! You get to class using less energy!

Now as to why you dont want to do this. Lets say one day he stops to tie his shoe, you dont react fast enough and run into the back of him. He's big enough that he may not even realize you did, but for you? You just ran into a human wall, broke your nose, dropped all your books and split your drink.

Now picture that doing 75 MPH running into a semi. Most of the times you do it, nothing will go wrong and youll save a couple cents of gas. But the one time it does your going to spending 10s of thousands to fix the mistake. The risk verse reward is just not worth it.

Spoken like someone who hasn't driven in poor visibility conditions or dark enough to not see anything other than a single glowing light...

When it is dark and you driving towards them and cannot see anything other than the one glowing light, how do you know if it is the top or bottom light that is lit if you are red/green colourblind?

> As a result of events that occurred during the early history of mammals, eutherian mammals retain only two of the four cone opsin gene families found in many other vertebrates. Very likely during this same time frame, the elaborate system of coloured oil droplets characteristic of photoreceptors in many vertebrates were also abandoned, as was a portion of the specific retinal circuitry dedicated to processing colour information (Jacobs & Rowe 2004). These changes left most eutherian mammals with a single dimension of colour vision. Primates subsequently escaped this restriction by evolving a series of visual system alterations that provided opportunities for expanded colour vision.

From Evolution of colour vision in mammals

This means that mammals generally have poor color vision, primates like us being an exception. No need for flashy displays, they couldn't see them.

As for birds (aka avian dinosaurs), a lot of them have four color receptors, one more than our three, and their plumage is in fact more complex and dazzling than what we humans can even see. (Similar to flowers who sport designs only visible in the ultraviolet, meant for insect eyes.)

Fishes generally have good color vision, even into the ultraviolet, but as light decreases with depth those living deep down can be left only with rods in their retinas, i. e. be color blind.

In both cases, fishes and birds, the display of colors is used to attract mates, sometimes to scare rivals away.

Fantastic shapes (which can be found in mammals too, in the form of weird, cumbersome horns, for example) are thought to be the result of sexual selection, the females (generally) "preferring" these as a sign of health and thus good genes and lack of parasites. (A bird with a ridiculously oversized tail has to be good at survival to make it to the mating season.)

A last point about fishes: water drag increases with temperature. So while the big ones like sharks, tuna, &c., are always streamlined, it makes no sense for small tropical ones, and they can indulge in attractive body forms instead. But you don't see that in cold waters.

I mean, yes, the great firewall is sophisticated. That example though is probably the most basic feature of the most trivial firewall possible, your home modem could probably do it.

More interesting examples would be some of the clever packet analysis they do on encrypted connections.

But again, even this isn't enough to prevent all undesired traffic, especially given that there's legitimate uses for VPNs, overseas file sharing sites, etc.

For instance, if they blocked external access to every server in China they'd be knee capping their entire economy, so they have to work out which ones. That's not easy or cheap to do accurately at scale.

There's research being done to automate the process for large trucks so that they move together as a 'platoon', communicating with each other for semi-autonomous braking and accelerating. It would save a whole lot of fuel on long-haul drives.

https://highways.dot.gov/research/laboratories/saxton-transportation-operations-laboratory/Truck-Platooning

oh, they just use mathematical models like regresion analysis

I appreciate the explanation, this was really helpful.

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In a nutshell, when your computer sends a "message" over the internet, that message goes to a computer at your ISP. The message has a "header" that says, "I'm this address, I'm trying to send it to that address." The ISP computer tries to find that address or, if it can't, it tries to find one it knows that's a little closer, and the process repeats. Every computer that gets this message has a chance to read it, store it, etc.

Proxy: a tiny bit of security against snooping

A "proxy" is a machine you tell your computer to ALWAYS send the message to first. This changes the way the "header" works a little bit. You send to the proxy "I'm this address, I want to send to that address". But when the proxy get it, it changes it to "I'm <the proxy address>, I want to send to that address". The message goes to other computers, and when it comes back to the proxy, the proxy rejiggers the message so it goes to you. This adds a bit of privacy, as everything past the proxy only knows the proxy sent the message. Note that your ISP is still between you and the Proxy, so there are still some computers that get a chance to see the message and/or record it.

VPN: a lot of things, but also more security against snooping

A VPN can be a lot of things, but right now we're interested in how it's sort of like a proxy. Normally for computers to talk directly to each other they need to be (oversimplified) connected to the same network, and "same network" here is a very restrictive concept. A VPN is a way to break the rules and treat a lot of "not connected" computers as if they were on the same network.

But in the context I'm smelling, you're also interested in "VPN tunnels". Oversimplified, a VPN using this feature ALWAYS demands that the traffic between you and the VPN is encrypted. So while you're still using your ISP's computers to transfer data, now all the ISP sees is "Oh, this is an encrypted message to a VPN. Think of it kind of like if you don't want people to know who you send a message to, you put the "real" envelope inside another envelope and mail it to someone else you trust. So it's LIKE a proxy, only now it hides the part BEFORE the proxy from anyone who can intercept it there. (Whether it's encrypted AFTER the VPN is up to whoever you're connecting to.)

Torrents: a file sharing protocol that's a completely different topic

One problem with downloading big files from a server is those servers might be unreliable. If it goes down, the download stops, and generally it's not easy to find another server or convince that other server to resume where you left off. This is especially true when doing "peer to peer" downloads, where the "server" is other peoples' machines which can be frequently losing connections or slow.

Torrents split files into lots of small "chunks" and everybody who has a complete chunk might be a "server" when you are downloading. If 100 people have the "chunk" you need, you can get it from the fastest one and keep doing that over and over. If 50 people lose their connection, you might not even notice and at worst you only lose 50 "chunks" of progress. This tends to lead to faster, more reliable downloads as long as people don't intentionally cut off uploads.

Probably what you meant to ask:

Torrents are amoral. They can be used to distribute legitimate files AND they can be used to distribute files that could get you in trouble whether or not we agree they should get you in trouble.

If you use a proxy to download torrents, your ISP could still potentially know you're downloading a file and, if they do some digging, what files you're downloading from who. That is bad news if you're doing things that could get you in trouble, and in some cases the ISP is obligated to report you or else they will get in trouble.

If you use a VPN, the ISP only knows you're receiving a lot of data through a VPN. Maybe they're suspicious it's something that could get you in trouble, but it could ALSO be something legitimate and they have no way to tell. The VPN company could, perhaps, do some snooping. But it's very bad for their business to do that, so many VPNs base themselves in countries where they are not obligated to do this snooping and promise they'll never do it.

This tech is, again, amoral. You can use it to hurt people while remaining anonymous. That's why a lot of people want to make it illegal. But that line of thinking is flawed, because sometimes there are very good reasons to want to be anonymous even when you aren't hurting people. I highly doubt people who say "I have nothing to hide" would be excited about a law that requires they shout their name and address while using a public restroom. "That's not the same", they'd say, but I don't find they can usually provide a good explanation why it's different. Please don't do things that hurt people with this knowledge and make those people feel more right.

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Came here to mention this as well. From what I remember it barely helped at all too. Plus with all the adjusting you'd likely have to do with the gas pedal it's probably almost equal to just set the cruise control and not tailgate.

Yeah for sure, I guess I drew a line between the "slipstream" and drafting.

The first vehicle is "breaking" the air, so there's less resistance to the following vehicles. This is also why cyclists and birds tend to flock.

I was thinking of this as two different things and addressed one part, but really it's all a combination of factors.

Also, why are domestic cats all pretty much the same size?

I think women are more more susceptible for any urethra infections and bladder infection that could possibly lead to urinary incontinence because their urethra simply shorter. Men have their urethra go through their penis while for women it’s only a few centimeters, this makes it easier for bacteria to be able to infect.

I’m no doctor and i don’t know if this is the (only) reason, it’s just what i know