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Today we have some lovely bird pictures by reader Paul Handford. Paul’s captions and IDs are indented, and you can enlarge the photos by clicking on them.

A few words about me.  I am an evolutionary biologist, retired since 2010.  I grew up in UK, did my doctorate in E.B. Ford’s group, then to Rockefeller U, NYC, for post-doc (on possible genetic correlates of vocal dialects in the Rufous-collared sparrow, Zonotrichia capensis, in n.w. Argentina), then to Canada, home of my main career, on faculty at Western University Biology Dept, in London, Ontario.  After a decade or so post-retirement living in British Columbia, we moved definitively to Ireland.

This these are all passerine birds from Ireland, mostly from the general Dublin area, taken in the past 2-3 years.

Male Chaffinch, Fringilla coelebs.  Drumcondra, Dublin, Mar, 2023:

European Goldfinch, Carduelis carduelis. Kilmainham, Dublin.  Mar, 2022:

Grey Wagtail, Motacilla cinerea. River Tolka, Drumcondra.  Feb 2023:

European Robin, Erithacus rubecula. Castletown, Celbridge, Dec 2021:

Eurasian Blackbird, Turdus merula. Drumcondra, Feb, 2023:

Song Thrush, Turdus philomelos, River Dodder, Dublin. Jan, 2022:

These shots are essentially portrait shots, so little to say about behaviour etc. (except the singing robin!)

More shots from around Dublin. You might be surprised to see the humble and much-maligned starling here;  but though ubiquitous and pushy, close inspection shows them to be quite beautiful, and they are remarkable vocal mimics, with a highly complex song.

Eurasian Skylark, Alauda arvensis.  Bull Island, Dublin Bay. Mar 2022:

White-throated Dipper, Cinclus cinclus.  River Dodder.  Apr 2023:

Eurasian Blue Tit, Cyanistes caeruleus.  Drumcondra.  Feb 2022:

Great Tit, Parus major.  River Liffey, Kilmainham. Feb 2022:

European Starling, Sturnus vulgaris.  Bull Island.  Apr 2022:

Eurasian wren, Troglodytes troglodytes.  River Dodder.  Apr 2023:

Camera:  Canon  EOS 90D;  lens:  Canon EF 100-400mm 1:4.5-5.6 L IS II USM

Last time, I showed you that a simple quantum system, consisting of a single particle in a superposition of traveling from the left OR from the right, leads to a striking quantum interference effect. It can then produce the same kind of result as the famous double-slit experiment.

The pre-quantum version of this system, in which (like a 19th century scientist) I draw the particle as though it actually has a definite position and motion in each half of the superposition, looks like Fig. 1. The interference occurs when the particle in both halves of the superposition reaches the point at center, x=0.

Figure 1: A case where interference does occur.

Then I posed a puzzle. I put a system of two [distinguishable] particles into a superposition which, in pre-quantum language, looks like Fig. 2.

Figure 2: Two particles in a superposition of both particles moving right (starting from left of center) or both moving left (from right of center.) Their speeds are equal.

with all particles traveling at the same speed and passing each other without incident if they meet. And I pointed out three events that would happen in quick succession, shown in Figs. 2a-2c.

Figure 2.1: Event 1 at x=0. Figure 2.2: Event 2a at x=+1 and event 2b at x=-1. Figure 2.3: Event 3 at x=0.

And I asked the Big Question: in the quantum version of Fig. 2, when will we see quantum interference?

1. Will we see interference during events 1, 2a, 2b, and 3?
2. Will we see interference during events 1 and 3 only?
3. Will we see interference during events 2a and 2b only?
4. Will we see interference from the beginning of event 1 to the end of event 3?
5. Will we see interference during event 1 only?
6. Will we see no interference?
7. Will we see interference at some time other than events 1, 2a, 2b or 3?
8. Something else altogether?

So? Well? What’s the correct answer?

The correct answer is … 6. No interference occurs — not in any of the three events in Figs. 2.1-2.3, or at any other time.

• But wait. . . how can that make sense? How can it be that particle 1 interferes with itself in the case of Fig. 1 and does not interfere with itself in the case of Fig. 2?!

How, indeed?

Perhaps thinking of the particle as interfering with itself is . . . problematic.

Perhaps imagining individual particles interfering with themselves might not be sufficient to capture the range of quantum phenomena. Perhaps we will need to focus more on systems of particles, not individual particles — or more generally, to consider physical systems as a whole, and not necessarily in parts.

Intuition From Other Examples

To start to gain some intuition, consider some other examples. Some have interference, some do not. What distinguishes one class from the other?

For example, the case of Fig. 4 looks almost like Fig. 2, except that the two particles in the bottom part of the superposition are switched. Is there interference in this case?

Figure 4: Similar to Fig. 2, but with the twoparticles reversed in the bottom part of the superposition.

Yes.

How about Fig. 5. In this case, the orange particle is stationary in both parts of the superposition. Is there interference?

Figure 5: In this case, the blue particle is moving (horizontal arrow), but the orange one is stationary in both cases (vertical arrow).

Yes, there is.

And Fig. 6? Again the orange particle is stationary in either part of the superposition.

Figure 6: Similar to Fig. 5, in that the orange particle is again stationary.

No interference this time.

What about Fig. 7 and Fig. 8?

Figure 7: Now the particles in each part of the superposition move in opposite directions. Figure 8: As in Fig. 7, but with the two particles switched in the bottom part of the superposition.

Yes, interference in both cases. And Figs. 9 and 10?

Figure 9: The blue particle is stationary in both parts of the superposition. Figure 10: Similar to Fig. 9, except that now the orange particle is stationary in the bottom part of the superposition.

There is interference in the example of Fig. 10, but not that of Fig. 9.

To understand the twists and turns of the double-slit experiment and its many variants, one must be crystal clear about why the above examples do or do not generate interference. We’ll spend several posts exploring them.

What’s Happening (and Where)?

Let’s focus on the cases where interference does occur: Figs. 1, 4, 5, 7, 8, and 10. First, can you identify what they have in common that the cases without interference (Figs. 2, 6 and 9) lack? And second — bringing back the bonus question from last time, which now comes to the fore — in the cases that show interference, exactly when does it happen, and how can we observe it?

Next time we will start the process of going through the examples in Fig. 2 and Figs. 4-10, to see in each case

• How does the wave function actually behave?
• Why is there (or is there not) interference?
• If there is interference,
  • where does it occur?
  • how exactly can it be observed?

From what we learn, we will try to extract some deep lessons.

If you are truly motivated to understand our quantum world, I promise you that this tour of basic quantum phenomena will be well worth your time.

As of five minutes ago. But last night we had bad storms in Chicago and now it’s snowing. I hope the ducks are okay. Esther looks to have motherhood in her future.

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The post The use of placebo controls in clinical trials first appeared on Science-Based Medicine.

Having a tattoo has been linked to a higher risk of conditions like lymphoma and skin cancer, but the situation isn't clear-cut

As civilisations become more and more advanced, their power needs also increase. It’s likely that an advanced civilisation might need so much power that they enclose their host star in solar energy collecting satellites. These Dyson Swarms will trap heat so any planets within the sphere are likely to experience a temperature increase. A new paper explores this and concludes that a complete Dyson swarm outside the orbit of the Earth would raise our temperature by 140 K!

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Dark Energy is a mystery so daunting that it stretches and strains our most robust theories. The Universe is expanding, driven by the unknown force that we've named Dark Energy. Dark Energy is also accelerating the rate of expansion. If scientists could figure out why, it would open up a whole new avenue of understanding.

Our current best theories of the universe suggest that dark energy is making it expand faster and faster, but new observations from the Dark Energy Spectroscopic Instrument suggest this mysterious force is actually growing weaker

New magnetic nanoparticles in the shape of a cube sandwiched between two pyramids represent a breakthrough for treating ovarian tumors and possibly other types of cancer.

The ESA's Euclid Space Telescope has already wowed us with some fantastic images. After launching in July 2023, the telescope delivered some stunning first images of the Perseus Cluster, the Horsehead Nebula, and other astronomical objects. Now, the telescope has released its first images of its three Deep Fields.

On 19 March 2025, the European Space Agency's Euclid mission releases its first batch of survey data, including a preview of its deep fields. Here, hundreds of thousands of galaxies in different shapes and sizes take center stage and show a glimpse of their large-scale organization in the cosmic web.

Sensors attached to animals gather valuable data to track and mitigate the human influence on marine life. The review paper emphasizes the importance of integrating data from various sources and advocates for an 'Internet of Animals' based on open access and shared standards.

Researchers injected CO2 gas into seawater while applying an electrical current. The process transformed dissolved ions, minerals in seawater into clusters of solid particles. The clusters hold over half their weight in CO2 to become a carbon sink. Material could replace sand in concrete and be used in other construction materials while trapping CO2.

The ability to conduct heat is one of the most fundamental properties of matter, crucial for engineering applications. Scientists know well how conventional materials, such as metals and insulators, conduct heat. However, things are not as straightforward under extreme conditions such as temperatures close to absolute zero combined with strong magnetic fields, where strange quantum effects begin to dominate. This is particularly true in the realm of quantum materials.

The ability to conduct heat is one of the most fundamental properties of matter, crucial for engineering applications. Scientists know well how conventional materials, such as metals and insulators, conduct heat. However, things are not as straightforward under extreme conditions such as temperatures close to absolute zero combined with strong magnetic fields, where strange quantum effects begin to dominate. This is particularly true in the realm of quantum materials.

A recent study evaluating garnet-type solid electrolytes for lithium metal batteries finds that their expected energy density advantages may be overstated. The researchers posited that composite or quasi-solid-state electrolytes may be more viable alternatives.

An innovative platform replicates pancreatic functions, transforming diabetes therapy.

Dendritic structures that emerge during the growth of thin films are a major obstacle in large-area fabrication, a key step towards commercialization. However, current methods of studying dendrites involve crude visual inspection and subjective analysis. Moreover, growth optimization methods for controlling dendrite formation require extensive trial and error. Now, researchers have developed a new AI model that incorporates topology analysis and free energy to reveal the specific conditions and mechanisms that drive dendrite branching.