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Physics Forums Featured Threads
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Neutron star collisions as a heavy element source
There was a lot of discussion after the recent observation of the merger of two neutron stars about whether or not these events are the source of the heavier elements. See this thread, for example. This recent paper has some new analysis. Especially interesting is Figure 10, that I've reproduced below. The paper's estimate of the abundance of the heavy elements is good match to the measured abundance of those elements here on Earth... -
Stephen Hawking has Died- 14/03/2018
"Stephen Hawking, the British theoretical physicist who overcame a devastating neurological disease to probe the greatest mysteries of the cosmos and become a globally celebrated symbol of the power of the human mind, has died. He was 76." -
What should be the rules to write excellent code?
I know few rules that lets me write great code: 1. "don't pollute the global namespace" when I sit down to write JavaScript code. 2. SOLID 3. KISS 4. Liskov's Open-Closed principle
Can someone help me complete the list of such rules? -
Television Engineering History
I was surfing the net to get some ideas involving the Kerr electro-optic effect and noticed this Wikipedia external link. It's page two from Television History - The First 75 Years. It has some cool old articles and pictures like these (images can be made larger in your browser): Just thought I share. -
Observation of Alfvén waves heating the Sun's corona
The corona is much hotter than the surface of the Sun, contrary what you would naively expect from the heat flow. While plasma waves were long suspected as cause, the mechanism was not well understood. How are these waves produced, and how is their energy converted to heat? Scientists now observed the second part directly, and conclude that the conversion to heat is quite efficient. -
Are charged batteries heavier?
Since you can add energy to a battery then extract it later, considering mass energy equivalence, it should be more massive, no? -
Germ Protect a Straw - New Product Idea and Book Giveaway
I would like to propose that your product ideas are posted in two categories: Professional and Amateur: If you are a professional in ME or Aero or a related field, please post using the Spoiler tags, so that the Amateur participants won't see the answers too soon If you are an Amateur/hobbyist, go ahead and post your thoughts on the design (no peaking at the spoilers please). The design challenge is to incorporate germ protection into a straw... -
How close is Earth to the closest black hole?
Is it astronomically known what the closest distance is between Earth and a black hole? The article... says
The Milky Way teems with black holes — about 100 million of them.Based on this estimate, and taking into account the relative density of matter based the distance from the center of the Milky Way, what would be a reasonably accurate estimate of the distance between Earth and the closest black hole? -
Science and math books with nice covers
Serious books on math, physics and related sciences usually have covers which are quite boring and visually not very attractive. (Books that have something to do with Universe are a common exception, but when you see a few of them you have seen them all.) But sometimes, covers are really interesting and/or beautiful. Here you are encouraged to present examples... -
B Level Explanation of Conduction and Resistance
Students seeking “deeper” understanding of basic electricity, frequently come with one of the following misconceptions. 1.Electrons are like balls, they start with potential energy and gain kinetic energy. They deliver their energy to the far end of the wire by filling a bucket. 2. Electrons are like pods filled with energy. The pods burst as they go through a resistor, and they are all used up by the time the wire reaches ground.
I am seeking a B level explanation of conduction and resistance that is not based on analogies... -
Psychology: How will we react to discovery of alien life
The pilot study analyzed news scientific reports (with software), and gave questionnaires to study subjects after reading some specially chosen reports as well. You are best advised to read the phys.org link first before generating conclusions. Limited study. -
The Forgotten Anniversary: 100 Years since Emmy Noether's Theorems
We shouldn't have forgotten this: On January, 25th it has been 100 years, a complete century, since Emmy Noether published her paper "Invarianten bestimmter Differentialausdrücke" (Invariants of Certain Differential Expressions, Göttingen 1918). It is still the basic concept of so many physical models, from classical mechanics to the standard model of particle physics... -
Can indistinguishable particles obey Boltzmann statistics
Many text books claim that particles that obey Boltzmann statistics have to be indistinguishable in order to ensure an extensive expression for entropy. However, a first principle derivation using combinatorics gives the Boltzmann only for distinguishable and the Bose Einstein distribution for indistinguishable particles (see Beiser, Atkins or my own text on Research Gate). Is there any direct evidence... -
Warm air goes up... reason on a microscopic scale?
I was wondering about the microscopic reason warm air rises up, while cold air comes down. I am aware of the macroscopic reason - density changes. But what happens microscopically? Decrease in density means that the gas molecules are widely spaced out, but their mass remains the same. Then why does warm air go up? -
Why did you start learning physics?
Why did you decided to learn physics? What was your motivation? What is your personal physics story?
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