Tag: Science

Earth, Air, Water, and Ice.

In my attempts at Ice Storage Heat Source popularization I have been facing one big challenge: How can you – succinctly, using pictures – answer questions like: How much energy does the collector harvest? or What’s the contribution of ground? or Why do you need a collector if the monthly performance factor just drops a…
On Photovoltaic Generators and Scattering Cross Sections

Subtitle: Dimensional Analysis again. Our photovoltaic generator has about 5 kW rated ‘peak’ power – 18 panels with 265W each. Peak output power is obtained under so-called standard testing condition – 1 kWp (kilo Watt peak) is equivalent to: The last condition can be rephrased as: We get 1 kW output per kW/m2 input. 1 kWp…
Learning General Relativity

Math blogger Joseph Nebus does another A – Z series of posts, explaining technical terms in mathematics. He asked readers for their favorite pick of things to be covered in this series, and I came up with General Covariance. Which he laid out in this post – in his signature style, using neither equations nor…
Re-Visiting Carnot’s Theorem

The proof by contradiction used in physics textbooks is one of those arguments that appear surprising, then self-evident, then deceptive in its simplicity. You – or maybe only: I – cannot resist turning it over and over in your head again, viewing it from different angles. tl;dr: I just wanted to introduce the time-honored tradition…
Rowboats, Laser Pulses, and Heat Energy (Boring Title: Dimensional Analysis)

Dimensional analysis means to understand the essentials of a phenomenon in physics and to calculate characteristic numbers – without solving the underlying, often complex, differential equation. The theory of fluid dynamics is full of interesting dimensionless numbers – Reynolds Number is perhaps most famous. In the previous post on temperature waves I solved the Heat…
Temperature Waves and Geothermal Energy

Nearly all of renewable energy exploited today is, in a sense, solar energy. Photovoltaic cells convert solar radiation into electricity, solar thermal collectors heat hot water. Plants need solar power for photosynthesis, for ‘creating biomass’. The motion of water and air is influenced by the forces caused by the earth’s rotation, but by temperature gradients…
Lest We Forget the Pioneer: Ottokar Tumlirz and His Early Demo of the Coriolis Effect

Two years ago I wrote an article about The Myth of the Toilet Flush, comparing the angular rotation caused by the earth’s rotation to the typical rotation in experiments with garden hoses that make it easy to observe the Coriolis effect. There are several orders of magnitude in difference, and the effect can only be…
An Efficiency Greater Than 1?

No, my next project is not building a Perpetuum Mobile. Sometimes I mull upon definitions of performance indicators. It seems straight-forward that the efficiency of a wood log or oil burner is smaller than 1 – if combustion is not perfect you will never be able to turn the caloric value into heat, due to…
How to Evaluate a Heat Pump’s Performance?

The straight-forward way is to read off two energy values at the end of a period – day, month, or season: The Seasonal Performance Factor (SPF) is the ratio of these – the factor the input electrical energy is ‘multiplied with’ to yield heating energy. The difference between these two energies is supplied by the…
A Sublime Transition

Don’t expect anything philosophical or career-change-related. I am talking about water and its phase transition to ice because … …the fact that a process so common and important as water freezing is not fully resolved and understood, is astonishing. (Source) There are more spectacular ways of triggering this transition than just letting a tank of water…
Being Creative with What Is Available

This is a quote from Simon Dale’s website who has built several eco-friendly ‘Hobbit’ houses. It reminded me of the cave house built into lava bubbles by Lanzarote’s most famous artist César Manrique: Being creative with what is available has an appeal beyond economical necessities. As a teenage hobby astronomer I built a mounting for…
On Learning

Some years ago I was busy with projects that required a lot of travelling but I also needed to stay up-to-date with latest product features and technologies. When a new operating system was released a colleague asked how I could do that – without having time for attending trainings. Without giving that too much thought, and having my…
What Learning about Feynman’s Path Integrals Was Good for

I have gone to great lengths on this blog in order to explain how and why a degree in physics prepares you for seemingly different careers, or at least does not hurt. But it would have been so simple. I will now illustrate this – using just two incomprehensible images. Actually, I have a hidden…
Grim Reaper Does a Back-of-the-Envelope Calculation

I have a secondary super-villain identity. People on Google+ called me: Elke the Ripper or Master of the Scythe. [FAQ] No, I don’t lost a bet. We don’t have a lawn-mower by choice. Yes, we tried the alternatives including a reel lawn-mower. Yes, I really enjoy doing this. It is utterly exhausting – there is no…
Gödel, Escher, Bach, and Strange Loops: Nostalgia and Random Thoughts

I am curious – who read the book, too? Did you like it? I read it nearly 30 years ago and I would also tag it one of the most influential books I read as a teenager. [This might grow into a meandering and lengthy post with different (meta-)levels – given the subject of the post I…
Hacking the Biological Clock

I need to rant before I will borrow one hour of my life to some technocrats tomorrow – that will give it back to me in October. So the subtitle is: I hate Daylight Savings Time! Daylight Savings Time was inspired by a whimsical essay by Benjamin Franklin (probably not the first time that politics fell for something…
Carl Sagan’s Glorious Dawn: The Promise of Cosmos

This is a reblogged post:https://samirchopra.com/2014/03/24/carl-sagans-glorious-dawn-the-promise-of-cosmos/ Trying to catch up I am wading through social media streams and notifications. I am delighted to discover a post that echoes EXACTLY what I feel / have once felt as a teenager and high school student who had just decided to become a physicist. In his reflections on Carl…
How to Introduce Special Relativity (Historical Detour)

I am just reading the volume titled Waves in my favorite series of ancient textbooks on Theoretical Physics by German physics professor Wilhelm Macke. I tried to resist the urge to write about seemingly random fields of physics, and probably weird ways of presenting them – but I can’t resist any longer. There are different…