A Website I Like: "Science Questions with Surprising Answers" answered by Dr. Christopher S. Baird [Something Interesting #55]

A nightly ritual in our house is to quell the chattering of the "shower squirrels," as my spouse calls them. These squirrels aren't literal but rather are all the intrusive thoughts that should be left behind at work but somehow can't help but creep into our home life after we log off. A good way to keep these squirrels happy, though, is through distraction. Specifically distraction through questions about physics. We first tried just riffing on general principles and then quizzes online but neither of those were satisfying.

Picture by Dan Cristian Pădureț (Unsplash)

Luckily, I hit upon a blog from a professor at West Texas A&M University that's been entertaining the squirrels pretty well. What's been the most fun is having my spouse disagree with Dr. Baird's opinions on some of these subjects and expanding on the why behind their reason for doing so. We're still working through these since he's been writing about this since the very early 2010s, so he's got a lot of questions with even more answers. Even though we've been focused on his physics ones, he has several sections dedicated to numerous other topics of interest. I'm posting some of the ones we've gone through already (along with their first paragraphs - these posts can be lengthy...) as a taster so you can check out this site for yourself:

Can a fire have a shadow?

Yes, you can form the shadow of a fire, but perhaps not for the reason that you are thinking. A shadow is formed any time part of a light beam is blocked or redirected. The shadow region is the region in the light beam where there is less light than in the rest of the beam. This dimmer region tends to take on the shape of the object that is blocking or redirecting some of the light, so we tend to think of a shadow as something that is cast or created by the intercepting object. With this concept in mind, in order for a fire to have a shadow, the fire needs to somehow block or redirect part of another beam of light.

Does a source of electricity ever run out of electrons?

The answer to this question depends on the situation. We can roughly classify all electrical systems into two categories: static electricity systems and circuit electricity systems. Note that all electrical effects are actually part of one unified set of physical laws. This classification is therefore ultimately arbitrary and over-simplified. However, this classification is sufficient for our current purpose of understanding electric current.

How can glass produce glare without reflecting light?

Glass does indeed reflect light. In fact, glass always reflects some of the incident light (except in special situations that are rare). The process of glass reflecting light is not caused by impurities in the glass or by surface defects. Even the purest, smoothest, most transparent piece of glass reflects some of the light that shines on it. It's a fundamental effect involving the electromagnetic field of the light wave interacting with the electrons, atoms, and molecules that make up the glass. And it's not just glass that does this. All transparent materials always reflect some of the light that hits their surfaces (except in the rare cases where there is refractive index matching or V-polarized light encountering the surface at Brewster's angle). Sometimes transparent materials reflect a large amount of light and sometimes they reflect only a small amount. There may not be enough reflected light for you to notice it, but it's there.

Is there any difference between antimatter, dark matter, dark energy, and degenerate matter?

Yes. Although the names sound vague and almost fictional, the types of matter called antimatter, dark matter, dark energy, and degenerate matter are all different, specific entities that really exist in our universe.

Why is gravity not a real force?

Gravity is indeed a real force, but not in the traditional sense. In other words, gravity is not a direct, classical, action-at-a-distance force between two objects. However, in the broader sense, gravity is indeed a force because it describes the resulting interaction between two masses. Gravitational effects are fundamentally caused by the warping of spacetime and the motion of objects through the warped spacetime. However, the end result is as if a force was applied. Therefore, the most accurate approach would be to call gravity an "emergent force," meaning that what looks like a direct force is actually emerging from more fundamental effects (the warping of spacetime). With this in mind, it is perfectly reasonable to call gravity a real force.