Recent content by iantresman

On this graph on the Y-axis just above the origin is a "zigzag" mark (highlighted with the red circle) which represents a discontinuity as the value of Y jumps from 0 to 130. Does this mark have a formal name?

Thank for that, the article "Intro to Big Bang and Infinity Concepts" is useful.

The Big Bang is sometimes described as started from a singularity, which I have interpreted as meaning that its characteristics are undefineḍ. If that is the case, can we not even say that the Universe as a singularity was still infinite? Otherwise we are implying that the singularity was...

I didn't know where to start, whether drawing a tetrahedron and 2D circles is relevant.

If I consider a tetrahedron of four densely packed spheres of unit radius, what it the radius of the largest sized sphere that can fit in the space in between?

Thanks for that. So the Kerr Effect induces birefringence in the direction of the field, and the Pockels Effect induces birefringence perpendicular the field. I wonder whether either effect is used in an astrophysics context? I note that there is "A novel technique for remote sensing of...

The Faraday effect is a magneto-optical phenomenon caused by the interaction between light and a magnetic field. Is there a corresponding electrical-optical phenomenon, caused by the interaction between light and an electric field?

As I understand it, light is an electromagnetic wave consisting of an oscillating electric and magnetic fields perpendicular to each other. Are there experiments that will demonstrate (a) there is an electric field present? Stark effect? (b) a magnetic field, (c) that they are perpendicular to...

The Earth is moving around the Sun at around 30km/s, a change of 60km/s over the course of the year. Presumably, measurements of the speed of light would show a redshift up to ±30km/s? Are redshift measurements this accurate? Likewise, the speed of the Solar System around the Milky Way, is...

Although scientists once thought that radioactivity violated the law of conservation of energy, then new understanding of nuclear decay helped demonstrate that the law was fact. So why do we continue to call the Conservation of Energy a law, and not a fact. Why not a principle? Is there a...

I think that most people would describe a lightning bolt as a plasma because of the ionised air it produces. There are several parameters that may define a plasma. Interestingly, a gas may be ionized to only a fraction of a percent, and fulful the requirements that define it as a plasma:

It is not as clear cut as that. Fire may be a plasma. See https://www.physicsforums.com/showthread.php?t=203289#10"

Plasmas are usually "typed", or classified, in other ways. For example: Cold, warm and hot plasmas Fully/partially ionized plasma Collisional/Non-collisional plasma Neutral/Non-neutral plasma High/medium/low density plasma Magnetic /Non-magnetic plasma Dusty/grain plasmas...

A plasma is generally described as a collection of charged particles, but the species of ions does make for different kinds of plasma. More usually, the (positive) ions are mixed with equal numbers of negative ions: electrons. Ionizing any element will produce its corresponding plasma. So yes, a...

Have a look at some of the links at the beginning of this thread. In summary, fire is sometimes a plasma, and sometimes not. It all depends on your definitions, and how you define a plasma.