Entries by Greg Bernhardt

Spatial Curvature in Cosmological Models

Standard cosmological models are classified by spatial curvature into three broad types: open, flat, and closed universes. These correspond to negative, zero, and positive spatial curvature respectively, and each case has distinct implications for the geometry and global volume of space. Open, Flat, and Closed Universes In the simplest Robertson–Walker models the three cases can…

All About the Einstein Field Equations

Definition/Summary The Einstein Field Equations (EFE) are a set of ten interrelated differential equations that form the core of Einstein’s general theory of relativity. These equations describe how matter and energy determine the curvature of spacetime, providing a mathematical framework to relate spacetime geometry to its energy-matter content. Mathematically, the EFE relate the Ricci curvature…

Interview with Engineer jrmichler

Today we get to know a little more about Engineering Mentor jrmichler! Tell us a bit about your education and academic years Two years college (UW-Madison) in electrical engineering. Burned out (two semesters of 21 credits, tired of poverty, needed to think some things through), dropped out, joined US Air Force. Four years later, had…

Revolutionary Technologies and Discoveries in 20 Years

Experts weigh in: Most revolutionary technologies and discoveries in the next 20 years We asked our Physics Forums science advisors, “What technology or scientific discovery will be the most revolutionary within the next 20 years?” Below are their responses, edited for clarity and readability while preserving each contributor’s original voice. Demystifier “Machine learning will be…

Michio Kaku Interview — Physics, String Theory & Future

We are happy to present this archived interview with Dr. Michio Kaku, conducted in 2004. Michio Kaku is an American theoretical physicist, futurist, and popularizer of science. He is a professor of theoretical physics at the City College of New York and the CUNY Graduate Center. Kaku has written several books about physics and related…

Interview with Engineer Mentor anorlunda

Tell us about your school years? Part of my story is sad but common. I was a poor student. I didn’t pay attention, and I never did homework even once; until one day when it all flipped. That was the day I first learned about differential equations. Diffy-Q was so much fun, that it completely…

Interview with Physics Mentor bhobba

Give us an executive summary on bhobba I was born in Toowong Brisbane Australia 17/11/1955, and was raised in suburbs around Toowong – Toowong itself, Taringa and Indooroopilly. I went to 3 schools Taringa State School,. Toowong High and Indooroopilly High. I now live in Redland Bay Queensland Australia. It is about halfway between Brisbane…

Clifford V. Johnson: The Dialogues & Science Outreach

Clifford V. Johnson is a professor in the Physics and Astronomy Department at USC. He says, “I mainly work on (super)string theory, gravity, gauge theory and M-theory right now, which lead me to think about things like space-time, quantum mechanics, black holes, the big bang, extra dimensions, quarks, gluons, and so forth.” Clifford V. Johnson…

Sabine Hossenfelder: Dark Matter, Gravity & LIGO Interview

We are pleased to introduce Sabine Hossenfelder. Sabine is a theoretical physicist at the Frankfurt Institute for Advanced Studies. She also authors the popular physics blog Backreaction. Interview: Sabine Hossenfelder Reading your blog over the past 6 months or so, one gets a feeling that your views about (particle) dark matter versus modified gravity have…

PF Insight Scavenger Hunt 2

We have an amazing count of over 320 Insights published at Physics Forums. Now we test to see how much you remember from some of them. If you need a hint feel free to read the corresponding Insight which is linked at the end of the question. Good Luck and remember to read future Insights…

NASA Quiz and Trivia: Test Your NASA Knowledge

Since the mid 20th century NASA has been a force in aerospace research and programs. Let’s find out just how much you know about it’s history, programs and research.  Don’t forget to post your score in the forum thread. No prizes, so don’t Google it. :) Ready for your next quiz? How well do you know…

Interview with Physics Mentor: Stevendaryl

Give us a brief history on stevendaryl I was born and raised in the American South, mostly living in Georgia. It’s a Southern tradition, for some reason, for kids to be called by their middle name, so my friends call me “Daryl” even though my first name is “Steven”. I grew up in a family…

Interview with Science Advisor DrChinese

We are pleased to share with you an interview with PF Science Advisor and one of our founding members: DrChinese Who is DrChinese and share some early experience that got you interested in science. I am a Dallas, Texas, USA boy, now married with grown kids. I got very interested in science at a private…

Interview with a Physics Mentor: Nugatory

Give us a little background on yourself? I was born in Washington DC, grew up in Texas, bachelor’s in physics from Harvard in 1978 but found a career in system software instead. Son of two law professors and grandson of a third, raised a Quaker although it didn’t stick, keep a small fleet of well-rusted…

Sean Carroll Interview: Cosmology, Books & Insights

We are pleased to introduce Sean Carroll. Sean Carroll is a theoretical physicist at Caltech specializing in cosmology and quantum mechanics. He has a new book, The Big Picture, which addresses “On the Origins of Life, Meaning, and the Universe Itself.” Key Points Sean Carroll grew up near Philadelphia and studied at Villanova University. His…

Peter Krautzberger on MathJax — Accessibility & Future

We are pleased to introduce Peter Krautzberger. Peter is a manager for MathJax, the technology behind the display of equations on Physics Forums. “The core of the MathJax project is the development of its state-of-the-art, open source, JavaScript platform for display of mathematics.” Please give us a bit of background on yourself I was born…

Interview with Chemical Physicist: DrClaude

DrClaude is a mentor at Physics Forums!   What brought you to Sweden from Canada? Life, the Universe, and Everything. While in Canada, I was offered the opportunity to do part of my studies in France. After my Ph.D., I stayed in France for postdoctoral work. I tried getting an academic position in France, but…

PeterDonis Interview – Physics Mentor on Science & Tech

PeterDonis is a Physics Mentor at Physics Forums. About PeterDonis I have been interested in science since childhood. I hold two degrees in Nuclear Engineering (focused on fusion rather than fission), which are effectively degrees in plasma physics. I was also Navy ROTC and served six years in the U.S. Navy after graduation. After that…

PF Insights Scavenger Hunt

Have you been keeping up with reading each PF Insight? Let’s find out! Every question’s answer can be found in a PF Insight. Hint links are included if you need help.  Be sure to post your score in the comment area.

Interview with a Chemist: Borek

Give us a brief history of Borek Note: text below is of a negative pedagogical value, don’t read it if you are younger than 20, attending school or still naïvely hoping for the best. I was born half a century ago, in a galaxy far, far away. So far away our laws were all shifted…

Interview with a Physicist: ZapperZ

This is a new Interview category for Insights. While I line up some great new interviews I’ll be migrating some previous mentor interviews. ZapperZ is a staff emeritus at Physics Forums   Can you give us a brief history of ZapperZ? Without reveal things that are answers to a few of the security questions to my accounts, I would say…

Which Scientist Said What Quiz

Think you know your famous science quotes? Let’s find out in this 12 question quiz. There are no prizes, so it doesn’t pay to Google. Try your best on your own. Report your score in the comment area at the bottom. Good luck!

Interview with a Biophysicist: Andy Resnick

Let me introduce you to Andy Resnick, a long time Science Advisor at Physics Forums.   Tell us a little bit about how you developed an interest in biophysics That’s a good question, and I’m not sure how to answer. I’ve worked in the ‘in-between space’ for many years- for example, optics is in-between physics…

Interview with a Physicist: Doc Al

This is a new Interview category for Insights. While I line up some great new interviews I’ll be migrating some previous mentor interviews. Doc Al is a physics mentor for Physics Forums Can you give us a brief bio? Okay. It was never easy for me. I was born a poor black child. I remember the days,…

Russ Watters: Astrophotography & HVAC Engineer Mentor

This is a new Interview category for Insights. While I line up some great new interviews, I’ll be migrating some previous mentor interviews. About Russ Watters Russ Watters is an engineering mentor for Physics Forums. Brief bio I’m 37, I live outside of Philadelphia and I have a BS in Mechanical Engineering from Drexel University….

Ice Quiz: All About Ice Trivia

Winter is coming. First day of Winter is December 22nd. Time to learn a bit about a substance that the northern regions will encounter. Don’t forget to share your score in the comment section. Ready for your next quiz? How well do you know about the ice planet Pluto? 1. What is Ice? Ice is…

Pluto Quiz: Think You Know Pluto?

Pluto has been in the news quite a bit these past several months. Let’s see if you’ve been paying attention. Feel free to share your score in the comments section. When finished head over to our Pluto Flyby forum thread for the latest news. Ready for your next quiz? How well do you know ice?

What Is Evolution? How It Works — Mechanisms & Evidence

What is evolution? In every field of scientific endeavor there sometimes comes a quantum shift in knowledge, a grand denouement that changes how we see the world. In physics we have Newton’s laws, Einstein’s Relativity and Quantum Mechanics; in biology we have the discovery of DNA and Darwinian evolution. Why evolution matters It’s hard to…

Apollo Program: Moon Missions & Last Moonwalk 1972

Eugene Cernan: Last to Walk on the Moon On December 11, 1972, astronaut Eugene Cernan became the last person to walk on the lunar surface, marking the conclusion of NASA’s Apollo missions. This pivotal chapter in space exploration saw humanity push the boundaries of science and engineering to unprecedented levels. The Apollo program remains a…

LHC Quiz: Think You Know about the LHC?

News of the LHC progress has dazzled scientists and hobbyists alike. It’s now time to show just how much you know about the operation. Please share your results Ready for your next quiz? How well do you know about the Periodic Table of Elements? 1. What is the Large Hadron Collider (LHC)? The Large Hadron…

Physics Blogs You Need to Be Reading

These are some of the best physics blogs, updated regularly, written by some of the top minds. The feeds are updated on page refresh, so bookmark this page and you’ll have a quick overview of all the blog’s latest entries each time you visit here. We also asked our community advisors which physics blogs they recommended….

It’s Elemental! The Periodic Table Quiz

The periodic table is something we all are made aware of early in schooling, but have you really looked at it closely and learned about it’s lessor known facts? Let’s find out! Ready for your next quiz? How well do you know about the LHC? 1. What is the Periodic Table? The Periodic Table is…

Bioethics & Genetic Engineering: Ethics and Policy

Bioethics Key Points Worrying about the future now means recognizing advances in technology, such as genetic engineering, that have already arisen. The standard of health is not fixed; it will fluctuate depending on perceptions of different biological variations that may emerge in the human species. We must be careful using new technologies and understand their…

The Science Crackpot Index and Bingo Game

Discussing science online can be a frustrating experience when no quality controls are in place—which is often the case. As part useful reference and part entertainment, PF has put together a list of common attributes associated with dubious scientific discussion. Next time you’re in a debate, check this list to see whether the participants are…

Hand-to-Hand Combat Physics — Force, Momentum, Speed

Physics of Hand-to-Hand Combat Hand-to-hand combat (often abbreviated H2H or HTH) refers to fighting at very close range, usually without weapons. It includes self-defense, sport, and military contexts where encounters happen inside arm’s reach. Effective techniques exploit basic physics: getting the right force to the right place at the right time through timing, balance, and…

Interview with Mentor Integral

Meet a Mentor is a biweekly (twice a week) series to help you get to know your wonderful Mentors better. Constructive questions and comments are welcome! Today we meet: Integral Can you give us a brief bio? I am a 2nd generation Oregonian born smack in the middle of the 20th century. My dad came to…

Interview with Astrophysicist D H

Meet a Mentor is a series to help you get to know your wonderful Mentors better. Constructive questions and comments are welcome! Today we meet: D H Give us a brief history of D H I spent my childhood in Minnesota, the first nine years in Minneapolis and the last nine on a farm. I…

Interview with Mentor Evo

Meet a Mentor is a biweekly (twice a week) series to help you get to know your wonderful Mentors better. Constructive questions and comments are welcome! Today we meet: Evo Can you give us a brief bio? I’ve been in love with science as long as I can remember. As soon as I began to read…

Interview with Mentor LisaB

Meet a Mentor is a fun series to help you get to know your wonderful Mentors better. Constructive questions and comments are welcome! Today we meet: Lisab Give us a brief history of lisab I didn’t follow the usual education route. I dropped out of school in about 8th grade to hang out with my hoodlum…

Interview with Biologist Ryan_m_b

Meet a Mentor is a fun series to help you get to know your wonderful Mentors better. Constructive questions and comments are welcome! Today we meet: @Ryan_m_b Give us a brief history of Ryan_m_b I’m in my mid-twenties, spent most of my life living in a small town on the border of the country side but…

Interview with Mathematician Mark44

Meet a Mentor is a series to help you get to know your wonderful Mentors better. Constructive questions and comments are welcome! Today we meet: Mark44 How did you become interested in mathematics? Along about 4th grade I came across an algebra textbook that really fascinated me, with all of its x’s and y’s, and symbols…

Interview with Physicist jtbell

Meet a Mentor is a weekly series to help you get to know your wonderful Mentors better. Constructive questions and comments are welcome! Meet the Mentor: jtbell Can you give us a brief history of jtbell? I went to a small, liberal-arts college in a Midwest village in the US. There were only three physics…

Meet Mentor DaleSpam — Biomedical Engineer & Mentor

Meet a Mentor: DaleSpam Meet a Mentor is a fun series to help you get to know your wonderful Mentors better. Constructive questions and comments are welcome! About DaleSpam Today we meet: DaleSpam. Give us a brief history of DaleSpam I have moved around a decent amount during my life: Arizona, Indiana, Colorado, Texas, Michigan,…

Evolution Explained: FAQs, Evidence & Common Misconceptions

Key Points Evolution is a scientific theory supported by multiple independent lines of evidence. In science, the term “theory” denotes a well-tested explanatory framework, not a mere guess. Evolution and religion do not necessarily conflict; many religious people accept evolution. The second law of thermodynamics does not rule out evolution because Earth is not a…

5 Pieces of Evidence that Support Theory of Evolution

Evidence for Evolution If you’re new to the topic, these primers provide helpful background: What is Evolution: A Beginner’s Guide, What Is Evolution and How Does It Happen?, Evolution FAQ Evolution Key Points The fossil record shows broad trends over time, including changing forms and increasing similarity to many modern lineages, consistent with common ancestry….

Studio in a Box: Learn About Digital Modeling Amplifiers

Digital Modeling Key Points Digital Signal Processing (DSP) emerged in the mid-1970s, enabling musicians to simulate acoustic spaces and reproduce many classic effects in digital form. For many years, guitar tone was largely limited by the physical gear you owned; chasing specific sounds often required expensive vintage equipment. Modern microprocessors and improved algorithms now allow…