Posts about physics

The Feynman Lectures on Physics Available Online

The Feynman Lectures on Physics are now available to read online. They are a great collection of lectures covering physics and touching on many areas including: the Mechanisms of Seeing, Semiconductors and Algebra. This is a fantastic resource for learning about physics.

You can also get a boxed set of The Feynman Lectures on Physics for those that like paper. It is fantastic but not cheap.

Bill Gates bought the rights to the rights to The Character of Physical Law, 7 lectures Feynman gave at Cornell University (these are separate from the lectures listed above) and made them available online, which is great. Unfortunately the website is based on Microsoft tools and therefore quite a bother for many (or maybe even impossible with Linux computers – I am not sure). I guess since he made all his money via Microsoft it isn’t that surprising but it would have been nice if he provide the content in a more easily accessible way (even if they didn’t do the fancy additions they did on the Microsoft site. These are great enough videos to probably be worth the bother of installing proprietary Microsoft software in order to view them.

Related: Video of Young Richard Feynman Talking About Scientific ThinkingFeynman “is a second Dirac, only this time human” (Oppenheimer) – Classic Feynman: All the Adventures of a Curious Character

Explaining the Higgs Boson Particle Again

comic illustration explaining the Higgs-boson particle

Excerpt from Piled Higher and Deeper by Jorge Cham – go see the entire illustration.

Related: 5% of the Universe is Normal Matter, What About the Other 95%?At the Heart of All MatterThe god of small thingsCERN Pressure Test FailureNinja ProfessorsFriday Fun, CERN Version

Science Explained: Momentum For String of Metal Beads

Fun video with an explanation of the physics behind what might seem like the surprising action shown in the video.

Related: The Science Behind Hummingbird FlightScience and Optical IllusionsGravity and the Scientific MethodHow do Plants Grow Into the Sunlight?

How Do You Lose Weight While You Sleep?

In this interesting webcast, Derek Muller, (a physics teacher in Perth, Australia) explores how much weight you lose while you sleep. As physics teacher he asks the sensible question: how do you lose weight while you sleep, what weight do you lose?

His conclusion is you lose weight through perspiration, water vapor in your breath and expelling carbon dioxide. Losing the water weight is pretty straight forward. The process of adding carbon to the breath we expel is not something I thought of. He calculates that we lose about 100 grams of carbon during a night of sleep. In his somewhat scientific experiment (measuring himself for several days) he lost about 150 more grams, which he attributes to water vapor and perspiration.

It seems to me the amount of carbon we lose during sleep is probably much more consistent than the amount of water weight we lose (both between people and variation between different days).

Related: Can You Effectively Burn Calories by Drinking Cold Water?CDC Urges Reducing the Amount of Salt We EatWhy is it Colder at Higher Elevations?How Caffeine Affects Your BodyWhy Does the Moon Appear Larger on the Horizon?

How to Walk on Ice

infographic explaining how to walk on ice - walk like a penguin

Infographic by Tablet. Falling on ice leads to many injuries and even 60 deaths a year in the USA (about the number that will die due to tornados). The graphic encourages thinking like a penguin. Penguins walk well on ice (in some ways) and they also fall well.

Seeking to keep your weight well supported (short strides) is wise (and sliding instead of picking up your feet can help). Falling well is also important. It is basic physics, you want to lower your center of gravity if you are start to slip and avoid any excessive force (so sliding is better than trying to stick out your hand and support all your weight). The elderly are especially susceptible to injuries – avoiding taking direct shocks to the wrist, knees or hips is wise). It does seem kind of silly to learn how to fall but it is very helpful in avoiding injuries.

On sidewalks if you are going to fall and there is snow piled up off the sidewalk, falling into the pile of snow may well be softer than falling directly onto the sidewalk.

On ice you have lower friction so strategies that require friction are not useful – quick moves often rely on very sturdy bases (which are based on the friction of our shoe on for example concrete [which normally is good - though business shoes are not very good] and on ice [where it is very poor - sliding and gradual moves are better]).

Related: Falling SafelyMinistry of Silly WalksMake Crosswalks More VisibleWhy Wasn’t the Earth Covered in Ice 4 Billion Years Ago – When the Sun was DimmerScience Toys You Can Make With Your Kids

Circumhorizontal Arcs – Fire Rainbows – Cloud Rainbows

photo of rainbow in a cloud

Fire Rainbow, Johor Bahru by John Hunter

Yesterday afternoon I spotted this odd, colorful, spectrum seemingly in a cloud in Johor Bahru, Malaysia. The colors are similar to a rainbow but the prism effect takes on a bit different form than a rainbow as I learned with a bit of searching online. I added a short post to this blog, about the phenomenon a few years ago.

photo of a large cloud over Johor Bahru

Johor Bahru under a large cloud which is topped with a fire rainbow.

A circumhorizontal arc is an optical phenomenon – an ice-halo formed by plate-shaped ice crystals in high level cirrus clouds. They are also known as “fire rainbows,” if the cloud is at the right angle to the sun, the crystals will refract the sunlight just as when rainbow is created.

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Physics Lesson

Related: Brian Cox Lecture on Science and Quantum MechanicsScientific Inquiry Process Finds More Evidence Supporting Einstein’s Theory of GravityFriday Fun: CERN Version

Why is the Sky Dark at Night?

The answer isn’t quite as simple as it seems. I find the wording in the video a bit confusing.

The point I believe, is that the sky is dark instead of light. But not that the brightness would be huge (so for example, you couldn’t necessarily read my book outside just by starlight). The light would be very faint, it is just that it would be lightish instead of blackish, due to the reasons explained (redshift etc.). At least that is my understanding.

Related: Why is it Colder at Higher Elevations?Why Does the Moon Appear Larger on the Horizon?Why is the Sky Blue?Why Wasn’t the Earth Covered in Ice 4 Billion Years Ago – When the Sun was Dimmer

The Science Behind Hummingbird Flight

Aerodynamics of the hovering hummingbird

Hummingbirds and insects have evolved for sustained hovering flight from vastly different ancestral directions, and their distinct phylogenies underlie the differences in their aerodynamic styles. In all other birds—and, presumably, hummingbird ancestors—the downstroke provides 100% of weight support during slow flight and hovering. Given that many birds possess the mass-specific power (using anaerobic metabolism) to hover for short periods, the selective pressure on hummingbird ancestors was probably for increased efficiency (resulting in stiff wings with greatly simplified
kinematics), and an upstroke muscle (the supracoracoideus) that makes the recovery stroke rapid, while contributing enough to the hovering power requirements to allow the downstroke muscle (the pectoralis) to operate within its aerobic limits.

In other words, this pseudosymmetrical wingbeat cycle is good enough, and although hummingbirds do not exhibit the elegant aerodynamic symmetry of insects, natural selection rewards ‘good enough’ as richly as it does our aesthetic ideals

Related: Praying Mantis Attacks HummingbirdFriday Fun: Crow Sledding, Flying Back Up and Sledding Down AgainBird Using Bait to Fish

New Physics Prize Gives 9 Physicists $3 million Each

A new physics prize created by Russian billionaire who started a PhD in physics before switching to an MBA and getting rich (investing in Facebook, Twitter, Zynga and Groupon) has announced the first 9 winners. The award includes awards worth $3 million; the Nobel prize paid $1.1 million last year.

Yuri Milner awards make nine fundamental physics pioneers rich

The nine will now form a committee to select a winner, or winners, for next year. The prize will be given in the first quarter of each year

According to Milner, the new prizes are not intended to compete with the Nobels, and differ in crucial ways. They can go to younger researchers because experimental verification of theoretical breakthroughs is not required. And, unlike a Nobel prize, which can be shared by three scientists at most, the Milner prize imposes no limit.

Alongside the main prize, Milner’s foundation will give two further awards, the first being an annual New Horizons in Physics prize for promising junior researchers, and a special ad-hoc fundamental physics prize that can be awarded at any time, forgoing the usual nomination process. Milner said the latter prize might, for example, recognise experimental results that are clearly and immediately groundbreaking.

Milner, 50, left Moscow State University in 1985 with an advanced degree in theoretical physics. He later abandoned a PhD at the Russian Academy of Sciences for an MBA at the Wharton School of Business at the University of Pennsylvania.

winners:
Nima Arkani-Hamed, Institute for Advanced Study, Princeton. For original approaches to outstanding problems in particle physics, including the proposal of large extra dimensions, new theories for the Higgs boson, novel realisations of supersymmetry, theories for dark matter, and the exploration of new mathematical structures in gauge theory scattering amplitudes.

Ashoke Sen, Harish-Chandra Research Institute, Allahabad. For uncovering striking evidence of strong-weak duality in certain supersymmetric string theories and gauge theories, opening the path to the realisation that all string theories are different limits of the same underlying theory.

7 of the 9 winners are currently working in the USA (1 in India and 1 in France). 4 are at Princeton and 1 each at MIT, Cal Tech and Stanford.

Related: 2011 Nobel Prize in PhysicsShaw Laureates 20082008 USA Medals of Science and National Medals of Technology and Innovation

Scientific Inquiry Process Finds More Evidence Supporting Einstein’s Theory

As scientists have been able to see farther and deeper into the universe, the laws that govern its expansion have been revealed to be under the influence of an unexplained force.

In a paper on the arXiv, Astrophysical Tests of Modified Gravity: Constraints from Distance Indicators in the Nearby Universe, are a vindication of Einstein’s theory of gravity. Having survived several decades of tests in the solar system, it has passed this new test in galaxies beyond our own as well.

In 1998, astrophysicists made an observation that turned gravity on its ear: the universe’s rate of expansion is speeding up. If gravity acts the same everywhere, stars and galaxies propelled outward by the Big Bang should continuously slow down, like objects thrown from an explosion do here on Earth.

This observation used distant supernovae to show that the expansion of the universe was speeding up rather than slowing down. This indicated that something was missing from physicists’ understanding of how the universe responds to gravity, which is described by Einstein’s theory of general relativity. Two branches of theories have sprung up, each trying to fill its gaps in a different way.

One branch — dark energy — suggests that the vacuum of space has an energy associated with it and that energy causes the observed acceleration. The other falls under the umbrella of “scalar-tensor” gravity theories, which effectively posits a fifth force (beyond gravity, electromagnetism and the strong and weak nuclear forces) that alters gravity on cosmologically large scales.

“These two possibilities are both radical in their own way,” University of Pennsylvania astrophysicist Bhuvnesh Jain said. “One is saying that general relativity is correct, but we have this strange new form of energy. The other is saying we don’t have a new form of energy, but gravity is not described by general relativity everywhere.”

Jain’s research is focused on the latter possibility; he is attempting to characterize the properties of this fifth force that disrupts the predictions general relativity makes outside our own galaxy, on cosmic length scales. Jain’s recent breakthrough came about when he and his colleagues realized they could use the troves of data on a special property of a common type of star as an exquisite test of gravity.

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