> launched from Earth. It has been traveling for over 45 years and has made it 0.06% of the way to Alpha Proxima

This is not a great example because the point of the probe wasn't to exit the solar system quickly, it was to do science within the solar system. It gets brought up as an example but it really isn't valid because even with the technology of the time we could have sent something out at a higher velocity, but it would have defeated the purpose.

[removed]

Where one sex (usually males) competes physically for the other sex, there is selection pressure for large size, musculature, weaponry like antlers and horns, territoriality, and aggression. The winners of these contests reap huge rewards in terms of mating (Bateman's principle), which is why sexual dimorphism is associated with polygyny. In monogamous species, there is much less incentive to invest energy into intrasexual competition.

That article is about “body composition in relation to lean, fat and bone masses”, not necessarily the phenotypic differences between the sexes. Meaning, how muscle, fat, and bone are distributed on the body differentially between the sexes and over time. You can’t pretend like a 6’5” 300lb dude is only that big because of hormones. Genetics has a lot to do with it.

[removed]

/u/Weed_O_Whirler has covered the relationship between the cardinal directions and the magnetic field of the Earth, but another aspect of your question is basically asking why do we use a coordinate system that (when viewed on a projected map) is a Cartesian coordinate system. At the simplest level, to define a location in an x-y plane, you need two coordinates. You could theoretically define two coordinate axes which are not at right angles to each other, but it would make defining coordinates way more complicated. The simplest solution is to have two orthogonal coordinate axes (and in reality, to have three orthogonal coordinate axes, i.e., elevation) to uniquely define locations. The same logic can be applied to spherical coordinate systems, i.e., why do we define locations with respect to intersections of sets of orthogonal planes with a sphere? Cause it's easier than defining coordinates with a non-orthogonal set of planes and their intersections with a sphere.

It's also worth noting that in most locations, it's actually rare that the sun rises/sets truly due east/west with respect to true north (and the location where the sun set/rises moves because of the inclination of the rotational axis with respect to Earth's orbital plane). Thus, east and west are not defined as such because of the sun, but rather because they specifically are directions along the equator which is orthogonal to the rotational axis. Even if we were on a planet that had a very high inclination (i.e., the orientation of the rotational axis was much closer to being parallel with the orbital plane) it would still make the most sense to define a set of coordinate axes that parallel the equator (and thus are perpendicular to the coordinate axis that parallels the rotational axis).

Getting back to the relation between our coordinate axes and the magnetic field, it would be interesting to consider a hypothetical of early navigation developing on a planet that had a setup like Uranus, which has a rotational axis nearly parallel to the orbital plane but also a magnetic field that is oriented at a high angle with respect to the rotational axis. We define coordinates on Uranus like we do on Earth, i.e., with respect to the rotational axis, but it's hard to know what kind of coordinate system one would develop if you were living on (a habitable rocky planet) that had a similar setup.

[removed]

[removed]

I think you asked the equivalent of “If a tree falls in the forest, and no one is around to hear it, does it make a sound?”

There are vibrations propagating through the medium of the tuning fork. Thus, sound is being propagated. In space it doesn’t have a medium to transfer that wave to, and thus it cannot be perceived by the human ear. That doesn’t mean the vibrations aren’t functionally the same as if we hit the tuning fork in a place with some sort of atmosphere. Sound doesn’t need to be perceived to be functionally the same thing as sound that is perceived. Technically any vibration through a medium is considered sound, whether you can hear it or not.

You're point about testing methods is a great one, and I was going to make that point myself. I work as a chemist refining the next generation of testing methods, and when we use a new method we need to do large numbers of cohort studies, to document the normal ranges with the new methodology. A new methodology may make the averages go down, and it doesn't mean that everyone magically got healthier, it just means this new test is different.

I do have to be my naturally pedantic self and point out that there are not two kind of cholesterol. What you are referring to are actually called lipoproteins, for the life of my I don't know why we call them cholesterol but it's of course not just you. Cholesterol levels are an entirely different test, and there is only a single kind of cholesterol, called cholesterol. Lipoproteins are responsible for collecting, depositing, and moving around all of your lipids (triacylglycerides and cholesterol) throughout your body. HDL lipoprotein tend to play a role in the deposition of fats, especially arterial cholesterol, (which is why we call them "bad") while LDL lipoproteins tend to help to remove such deposits (why they are the "good" cholesterol). Importantly though, neither is actually a kind of cholesterol, of which there is only one (okay one natural cholesterol, I actually used to work in a synthesis lab where we specialized in making unusual forms of cholesterol).

I wouldn't be thanking someone for such a bad reply lol, I don't know how they twisted this into you being against vaccines, and while they're right that infection won't improve your immunity to all illnesses, they clearly have absolutely no knowledge of how infections improve immunity to similar illnesses (i.e. an influenza strain that is similarly but not identical to a previous infection).

https://www.thelancet.com/journals/lanmic/article/PIIS2666-5247(21)00180-4/fulltext

To add an extra level to the rabbit hole, there are actually three norths. True north, magnetic dip north, and geomagnetic north. True north has been covered, but magnetic dip north is the location where the magnetic field is oriented vertically (so if you had a magnetic inclinometer, where it would point vertically) whereas geomagnetic north is the intersection of the surface of the Earth with the best fit dipole field. In detail, if the Earth's magnetic field was a true dipole (like a bar magnet) then the north and south dip poles (1) would be antipodal with respect to each other and (2) they would be equivalent to the geomagnetic poles (which are by definition antipodal), but neither of those tend to be true as the location of the dip poles migrate as part of secular variation.

[removed]

The reason sugar won't wash away as easily is it will already be sticking to other things in the pipe.

Sugar has hydrogen bonds so any small amount that does dissolve in the alcohol will readily stick to other things.

Sugar will also easily dissolve with any water already in the pipe.

Once sugar has stuck to other things it may technically no longer be sugar but it will still be there.

Salt might react but generally the NaCl bond is pretty common because neither readily reacts with much else.

Flourine from any fluorides around maybe and heavier earth metals but generally, and water and the ions will just stay pretty close to each other in solution.

Hydrogen bonds like other hydrogen bonds and lots of stuff has hydrogen bonds.

I have been made aware that my calculation was off by a factor of 1000.

sorry, my mistake. (US and Europe use "." and "," in different ways")

So it's 622,000x as far away and would take 28m years. (or 1000x as long)

Same argument though. Anything exceeding the life-time of a few generations on earth is currently unfeasible.

The nearest black hole to us isn't 1.6 lightyears away, it's 1600 lightyears away.

Humans live in social groups. Humans are also great at fighting. On top of this, humans (like other animals) have an instinct to protect and care for their young. So, given this level of protection, if a baby has a need (food, hot/cold, needs care) it is much better for a baby to loudly communicate this to nearby adults so it survives infancy, because the adults can almost always handle external threats that might arise.

Wonderfully thorough answer.

I decided to check some math, and yeah, our fastest ever spacecraft, rounding up, goes 700,000 kmh. At that speed, it would take 156,000 years to reach the nearest black hole.

I didn't even consider the transmission problem, but yeah, conventional communications are a non-option at a fraction of the distance.

[removed]

I mean, i get what your saying, but this requires funding. And like other commenters have said, it wouldn't be able to transmit anything back to us, not only that, I don't think the information gained would even seem that useful, to justify an operation that would be 60,000 years into the future, when it's unclear if we'll be around for another 100 or so

First, some terms. There is "true north" and "magnetic north." True north is perpendicular to east. Magnetic north is close to perpendicular to east, but not quite.

True north is defined as the point that Earth's rotation axis points through. To visualize, look at this globe. The "true north" pole is where the pole sticks through the globe, the place the Earth is rotating about. This is what is perpendicular to east. Which, when you think about it as a rotation, makes sense. As the Earth rotates, the Sun is going to appear to rise in the direction the Earth is spinning. This globe photo may help illustrate that if it's not clear as of why.

Now, magnetic north is based on the magnetic field of the Earth, and it is close to truth north, but the true north pole is about 1200 miles away from the magnetic north pole. In the latitude bands most people live in, that distance doesn't matter much- if you point true north of magnetic north, you're basically pointing in the same direction- but as you move really far north (or really far south), that distance matters more.

So, is it a coincidence that magnetic north and true north are close to aligned? No, it's also due to rotation. The Earth's magnetic field is caused by spinning liquid metal in the outer core, and that core's direction of spin is highly influenced by the direction of the Earth's rotation. So, most of the the time, the Earth's magnetic field is close to aligned with the Earth's rotation axis. Since the Earth's magnetic North pole was discovered, it has moved by 600 miles. The Earth's magnetic field will also flip-flop at some point in the future (Magnetic north pole will go to the geographic south pole) and has flip-flopped in the past. During this flip-flopping time, the magnetic north pole will have to wander all the way down the globe, and thus magnetic north and true north will be no where close to each other (and at some point, magnetic north will lie due east!). But most of the time, the Earth's magnetic field stays relatively aligned to the Earth's rotation.

(This is sort of going down a rabbit hole, but you can watch this video about why Canada labels their runways using true north, while most of the rest of the world uses magnetic north, but it comes down to how those little variations in where magnetic north is don't impact much, unless you're really far north or south)

[removed]

[removed]

I'm willing to take that chance for future generations... I mean its comforting knowing that's where the closest black hole is

E- yh I was naive there I'm learning as I read