Recent comments in /f/askscience

Weed_O_Whirler t1_j3x4b2n wrote

Reply to Is the uncertainty principle a general law, or just subjective to our own experience? by Turokr

To the best of our understand, particles are fundamentally wavelike in nature. For example, if you shoot electrons through closely spaces slits, they will form interference patterns just like light does (There are lots of other experiments you can do to demonstrate this as well, but this is perhaps the most straightforward one). So, if the wavelike nature of particles is fundamental (which we believe to be true), then the Uncertainty Principle is also fundamentally true. In fact, the Uncertainty Principle can be derived, without any reference to “measurement” at all.

There are actually many different uncertainty relations- the Heisenberg Uncertainty Principle being the most famous one- that there is an uncertainty between the position and momentum of a particle. But really, any two observables (observable being a quantum mechanics word for “something you can measure”) which do not commute will have an uncertainty relation. What does this mean? So, when something commutes, it means order of operations doesn’t matter. For instance, A + B = B + A. Addition commutes. Multiplication sometimes commutes. For instance, if x and y are just numbers, then xy = yx. But, if x and y are matrices, then x*y ~= y*x. In Quantum Mechanics, operators (or functions which operate on the wavefunction) sometimes commute and sometimes don’t. Ones that don’t (like position and momentum), will always have an associated uncertainty principle.

Position and Momentum are part of the canonical commutation relation. This means if the position operator (P) operates on the wavefunction (W) first, and then the momentum operator (M), you get a different answer than if the momentum operator operates first, and then the position. Or in math: [XP – PX]*W = i*h_bar, where i is the imaginary number, and h_bar is Plank’s constant divided by 2*pi. Another common pairing that shares this relationship is Energy and Time, thus they also have an uncertainty principle.

While perhaps this got pretty far into the weeds, the Wikipedia article summarizes it nicely:

> Historically, the uncertainty principle has been confused with a related effect in physics, called the observer effect, which notes that measurements of certain systems cannot be made without affecting the system, that is, without changing something in a system. Heisenberg utilized such an observer effect at the quantum level (see below) as a physical "explanation" of quantum uncertainty. It has since become clearer, however, that the uncertainty principle is inherent in the properties of all wave-like systems, and that it arises in quantum mechanics simply due to the matter wave nature of all quantum objects. Thus, the uncertainty principle actually states a fundamental property of quantum systems and is not a statement about the observational success of current technology. Indeed the uncertainty principle has its roots in how we apply calculus to write the basic equations of mechanics. It must be emphasized that measurement does not mean only a process in which a physicist-observer takes part, but rather any interaction between classical and quantum objects regardless of any observer.

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Bob_Skywalker t1_j3x05qd wrote

Reply to Why are coastlines crinkly near the poles but smooth in the tropics? by emsot

Jagged coastlines near the poles are caused by glaciation cutting through the landmass and isostatic rebound.

Smooth coastlines in the tropics and as you near the equator are due to heavier weathering from rain and liquid water.

Ice cuts, water erodes.

This is just the simple explanation from what I remember. Credentials- B Sc. Geology.

Edit: Additionally, I'd also like to point out that there are exceptions to this. Abundance of "jagged" toward the poles and "smooth" near the equator is just describing prevalence. Citing a smooth coast near a pole or a jagged pole near the equator doesn't discredit prevalence. For example, Hawaii, being relatively recently created by magma plumes it will take lots of time due to the mineral composition and youth of the islands for them to either smooth out or erode away. Another example is the tectonic uplift along the US west coast.

Edit 2: There are some top level comments that are more descriptive than mine with some good additional information. Don't just read mine because its higher and forget to scroll down for the more in depth comments.

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CrustalTrudger t1_j3wh3gc wrote

Reply to Can a major volcanic eruption save us from global warming? by gaddubhai

The main thrust of this question is covered in an existing FAQ, but the short version is that; (1) Yes, volcanic eruptions can cause global cooling, but (2) many details of the volcanic eruption (e.g., how large is it, where did it occur, what time of year did it occur, where in the ENSO cycle did it occur, etc.) all have substantial impacts on the degree of cooling that will result from a specific eruption, and (3) modelling of the competition between volcanic driven cooling and anthropogenic driven warming suggests given the right details, a large volcanic eruption could pause warming for ~20 years but this would then be followed by ~20 years of accelerated warming (e.g., this paper).

For a deeper dive on all of the above, see the linked FAQ, but it's also worth noting that if we're looking for mitigation strategies for warming, there are probably better ways than hoping for a large volcanic eruption (or other similarly drastic means, like purposefully inducing a nuclear winter). For example, many solar geoengineering proposals, specifically stratopsheric aerosol injection, seek to effectively mimic some of the atmospheric effects of a large volcanic eruption without the eruption.

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DoubleDad-xtc t1_j3wayse wrote

Reply to Does the immune system have a limit on memory for vaccines? Can we vaccinate against any and all microorganisms if we wanted to? by AdiSoldier245

The immune system does have a limit on the number of different pathogens it can remember and respond to at any one time, this concept is known as "immunological memory." However, the precise limit of how many pathogens the immune system can "remember" is not well understood and may vary from person to person. The immune system can handle a large number of different pathogens, but it's not unlimited.

When a person is vaccinated, the immune system is exposed to a small piece of the pathogen, such as a protein, rather than the actual pathogen itself. This allows the immune system to "learn" how to recognize and respond to that pathogen without causing an infection.

As a result, the immune system can develop "memory" of that pathogen, allowing it to respond more quickly and effectively if the person is exposed to the actual pathogen in the future.

It's worth noting that vaccines are developed for specific pathogens and it is not practical or necessary to make a vaccine for every pathogen that exists, as some of them are not dangerous to human health and many would not be able to be contracted by humans in the first place. Also, some pathogens are much harder to make vaccines for, for example, vaccines for viruses that frequently mutate like the flu.

The focus for vaccines development is usually on the pathogens that pose the greatest risk to public health, and the efforts are targeted on those that are most likely to cause severe illness or death, or that have the potential to spread easily in communities.

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