Hk-Neowizard

Hk-Neowizard t1_jbujg5u wrote

Here's an intuitive approach.

Consider the source of the vibrations in the middle of the medium. It's a combination of the inertia of the particle and the forces applied by neighboring particles.

When a particle at the boundary vibrates, the properties of the particle at the different medium applies a different force to the boundary particle. This changes the oscillation period of the boundary particle, which in turn applies a different force to the other particles in the original medium.

Essentially, the boundary particle goes out of sync, which reads as a reflection when scaled up to the entire boundary

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Hk-Neowizard t1_ixetrw6 wrote

Forces aren't getting weaker, exactly. They're just made to act across a larger gap.

One way to thing about it, is to imagine that every point in space "splits" into multiple points all around it (if space is a 3D grid, then every point "splits" into 3X3X3 points centered around the original point). This of course is wrong since space isn't a "thing" that can split, but it's a way to help our limited brains internalize the concept and develop an intuition around it.

Another way to think about it, is to consider force carriers. The photon, for instance, is the carrier for the electromagnetic force. The gluon is the carrier for the strong force, etc. If you're comfortable with the notion of force carriers, you can imagine these carriers are "slowing down". This is a bit more wrong than the previous analogy, because an expanding space mean that not only do "forces take longer to reach" from one particle to another, it also means the force a particle exerts on another is weaker. The analogy, however, helps give a new perspective on the concept of expanding space, so it's worth playing with.

It's important to note that the expanding space isn't really measurable on small scales yet, and won't be for MANY MANY years. The rate at which space is added between two points is proportional to the distance between those two points (again, consider the "splitting space" analogy, the more space, the more "splits" per unit of time), and anything smaller than intergalactic scales is so slow, that the standard-model forces (strong, weak, EM and gravity) all counteract it completely. Only in the vast nothingness of intergalactic space is there enough space and little-enough of anything else for this expansion to be the dominating affect. For now... (if the expansion of space is indeed accelerating)

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Hk-Neowizard t1_ixeooww wrote

The expansion of space is not the inertia from the big bang. If that were the case it would be slowing down, which evidence doesn't seem to support.

In fact, the expansion is likely accelerating and at a far distant future even the space between protons will expand faster than the strong force can pull them back in.

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Hk-Neowizard t1_ixediux wrote

  1. Space is expanding in the sense that the volume between every two particles (or more reasonably astronomical bodies) is growing. Imagine a grid on a paper. Every intersection is a particle. Now, "zoom in" on one "particle" - look at the distances between all particles compared to before, that's how space is expanding
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Hk-Neowizard t1_ixed4xs wrote

Space might be finite, we don't know, and can't know, since the observable space is all we can talk about in any certain matter (i.e the region of space that we can see or interact with, given the limitation of the speed of light). The observable space is finite.

However infinite space could exist, without there being something "outside" space. It doesn't have to have an edge. That's easy if you consider curved in a higher dimension.

Take the 2D case for simplicity. A 2D creature living on a sheet of A4 paper can't see height, only width and depth. If you roll that sheet into a cylinder, "space" is still finite, but has no edge. You could travel along the circumference forever.

So finite space with no edge is easy, and in fact likely given some observations we made (which are a bit over my head, TBH)

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Hk-Neowizard t1_iv09d39 wrote

That's true, but also meaningless. Any atom has moving electrons in it (except some H^+ and He^+2, if we're being pedantic). So under your definition literally everything produces a magnetic field.

The magnetic field from a few molecules however, is negligible, and only when compounded by aligning together many such fields do you get anything substantial enough to mean anything.

Tying this back to the original question, OP is clearly talking about macroscopic fields, as considered in biology, and not infinitesimal fields like those produced by a single hemoglobin molecule

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Hk-Neowizard t1_iuzs8e0 wrote

Humans don't produce any measurable magnetic fields. At most you could describe it as magnetic "noise", and even that would be a stretch.

The human body has a lot of small "circuits" that run a tiny amounts of current, but these have no order to them. Just like the difference between a random iron block and a magnet, without some dominant order, these tiny magnetic fields don't amount to anything measurable.

On top of that, the human body represents a rather significant reluctance to magnetic fields. Lots of free flowing iron around, ions and air. A measurable, yet still small, magnetic field won't get far enough to leave the body before weakening into nothing

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