Of Schemes and Memes Blog

Light, enchanted

Guest blog by  Liesbeth Venema

What motivates scientists to devote their lives to the pursuit of scientific discovery? It must be, at least partly, the hope of finding true beauty. After all, what can be more beautiful than opening up a new window on the world or uncovering a hidden layer of complexity in the laws of nature?

Plenty of beautiful scientific experiments have delighted scientists and non-scientists alike over the centuries. Light, in

light

from pixabay

all its colours and manifestations, has played a starring role. The intricate nature of light has been a wonder in itself: imagine the surprise when it was first discovered that white light can be unfolded into all the colours of the rainbow. And the many ways in which light provides us with useful tools and applications, multiplied with the advent of lasers, is unparalleled.

The year 2015 was chosen by UNESCO to be the International Year of Light (link: http://www.light2015.org/Home.html) and we endeavoured to find out which 10 experiments with light are thought of as the most beautiful of them all. We opened a poll from 17 February to 17 April, where anyone could choose up to three of their favourite experiments with light from a candidate list of about 30. Brief introductions of all experiments were posted weekly here at nature.com blogs.

Below are the results (click on the individual experiments to read the blog posts where they are introduced) and there is a clear winner chosen by 374 voters.

Young’s double slit, which confirmed the wave character of light, is the fairest of them all. A close second is Newton’s prism, which first revealed the colourful splendour of light. In third place is the laser, the ubiquitous invention that has revolutionized so many technologies.

Does this exercise bring us closer to defining beauty in science?

Perhaps a little. Clearly, one hallmark of a beautiful experiment is the element of surprise, the kind that reveals a new perspective on the world and opens a new direction in scientific enquiry. A prime example is number 5, van Leeuwenhoek’s microscope. “It enabled us to see beautiful small worlds, which we didn’t even know existed”, one of our voters commented. And another “The first visual confirmation of a world within our world, paving the way for an understanding of the world of disease and nature.”

Beauty can also be found in the sheer inventiveness of the human mind. Eratosthenes’ experiment is an example of such intellectual prowess. As summed up by one of our voters “Given the era in which this experiment was performed, I would say the originality and boldness of Eratosthenes, together with his capacity to guess an experimental evidence (completely out of the date of his time) are totally remarkable and admirable”.

The invention of the laser, which was the result of hard work and clever engineering, is another example “A moment of magic, even if it was expected at the time. It went on to transform the way we live.”

Another category is the eye-opening insight, the kind that seems obvious in hindsight but does no less than change our view of the world: the finding that the Universe is expanding from Doppler shifts in light emitted by retreating stars, was such an awe-inspiring discovery. “The Universe is not static. It is ever expanding into the unknown; much like human knowledge and science”, one of our voters wrote philosophically.

Young’s double slit, from 1801, is the number 1 most beautiful experiment. With a simple piece of equipment — a thin plate with two closely spaced slits — it produces ripple-like patterns of light, crucially confirming that light behaves as a wave, which was in doubt at the time. At first sight it is mainly that, a clean and crisp confirmation of a theory. “Elegant, informative and simple.  Everything an experiment should be”, as one voter said.

But another wrote “It gave an answer (at least for some time) to one of the most interesting debates in physics history”.  Indeed, the outcome of the Young’s experiment was not the whole story, and later experiments showed that light can also behave as a particle; this dual nature of light was an important theme in the development of quantum mechanics.

Young’s double slit has played an enduring part in scientific experiments and later on was used to produce wave-like patterns even for individual light particles, or photons, as well as for other particles such as electrons and more recently even for molecules. It reveals a deep property of both light and matter: they are all both particle and wave. How can this be?

And perhaps that is the essence of beauty in science: a striking, deceptively simple observation that contains at its heart a mystery. One that promises a new world of possibilities, waiting to be discovered with the next milestone, beautiful experiment.

Top 10 Beautiful Experiments:

1 Young’s double slit experiment with light (1801)

2 Newton’s prism, splitting the rainbow (1665)                                                                       

3 Demonstration of the laser by Maiman (1960)                                                                     

4 Eratosthenes’ calculation of the Earth’s circumference, using a tower’s shadow (240 BC)

5 Van Leeuwenhoek’s microscope, making micro-organisms visible (1670)       

6 Hubble’s discovery of an expanding universe from Doppler shift (1929)                              

7 Roentgen’s first X-ray image (1895)                                                                            

8 Michelson-Morley interferometer experiment to detect motion relative to the ether (1887) 

9 Bell test experiments with photons (1972)       

10 General relativity put to the test: measuring light bending during a solar eclipse (1919)

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