The Life of Light – from Candlemas to Biophotonics
Revd Dr Donald MacEwan, 4 February 2018
Readings: Habakkuk 3:1-4; Luke 2:22-40
This is the Candlemas Semester – in St Andrews. In Oxford and Trinity College, Dublin, it’s the Hilary Term. In Cambridge it’s the Lent Term. In Durham it’s the Epiphany Term. And in Aberdeen, where I was an undergraduate, it’s the rather more prosaic Second Half-Session. Why Candlemas in St Andrews? Well, Candlemas is one of the four quarter-days in Scotland, four divisions of the legal year, and so the ancient Scottish Universities traditionally called their three terms after three of these quarter-days: Martinmas, Candlemas and Whitsun. We dispensed with the last in 1997 when moving to two semesters.
Candlemas is a Christian festival celebrated on 2 February. It remembers the story we heard earlier from Luke’s Gospel. The passage mentions no candles but the tradition developed of people bringing candles to church on this day, 40 days after Christmas, to have them blessed for the year ahead. There may be an echo of pre-Christian rites, when the beginning of February was called Imbolc, marking the mid-point between the winter solstice and spring equinox, a time marked by the lighting of fires.
The story Luke tells mixes up two Jewish rituals – for the purification of a mother following childbirth, and a ritual payment following the birth of a first-born son. This continues – a mature Jewish student I know told me he had to pay a certain sum of money along with saying prayers when his eldest son was born. In the story, there may be no candles, but light and sight are at the heart of it. The prophet Simeon would not see death before he had seen the Lord’s Messiah. The prophet Anna spoke about the child to all who were looking for the redemption of Israel. Simeon, with the infant Jesus in his arms, says that he has seen God’s salvation, that this child is a light for revelation to the Gentiles and for glory to your people Israel. Jesus will enable all people to see the truth, and find their way to God.
Light in this beautiful story is a metaphor, an image for God, for truth, for guidance, for salvation. But it may be interesting, in this University where people think about light not only as a metaphor but as a phenomenon of nature, to review some of the key scientific discoveries humankind has made about light.
In about 300 BC Euclid postulated that light travelled in straight lines, describing the laws of reflection.
In 55 BC Lucretius wrote that The light and heat of the sun; these are composed of minute atoms which, when they are shoved off, lose no time in shooting right across the interspace of air in the direction imparted by the shove.
In the 17th Century René Descartes held that light was a mechanical property of the luminous body, assuming that light behaved like a wave.
Isaac Newton stated in 1675 that light was composed of corpuscles (particles of matter) which were emitted in all directions from a source.
Wave theory about light then became prominent in the 18th Century.
In the 19th Century, building on Faraday, James Clerk Maxwell concluded that light was a form of electromagnetic radiation.
The work of Max Planck and Albert Einstein in the early 20th Century moved our understanding of light in a quantum direction until our current perception of light as both particle and wave – as something that can be described sometimes with mathematics appropriate to one type of macroscopic metaphor (particles), and sometimes another macroscopic metaphor (water waves), but is actually something that cannot be fully imagined. We seem to have come back to metaphor.
The speed of light was gradually measured more accurately through the 18th Century and beyond, until today’s understanding definitively achieved in 1975 –299,792,458 metres per second in a vacuum. Nothing can travel faster than light, despite this lovely limerick:
There was a young lady named Bright,
Whose speed was far faster than light;
She set out one day
In a relative way
And returned on the previous night.
Studying light surely deepens our appreciation, our wonder at this crucial phenomenon of creation, helping us in our encounter with light in scripture. The story in Luke is part of a rich engagement with light throughout the Bible.
For one thing, light comes from God:
Then God said, ‘Let there be light’; and there was light. [Gen 1:3] For me there is no contradiction in the scientific understanding of light and my faith that without God, there would be no light. And furthermore, when Genesis says that God saw that the light was good, I cannot help but agree. Light is not only good, but underpins all visual beauty from last week’s moon to evening sunshine across the dunes; from the stained glass in this chapel to a child’s first painting; from a ladybird to laser shows.
The Bible further sees light as a natural image for God. As we heard in our reading from the prophet Habakkuk:
God’s glory covered the heavens…
The brightness was like the sun;
rays came forth from his hand. [Hab. 3:3-4]
John’s first letter says this with admirable clarity:
God is light and in him there is no darkness at all. [1 John 1:5]
The psalmist envisages God as clothed with light [Ps. 104:1]; and depicts God’s word as a lamp to my feet, a light to my path. [Ps. 119:105].
For scripture, the properties of light, its goodness, beauty, purity, clarity, and especially its making the world visible, understandable, liveable – these are also the hallmarks of the divine. Light makes life better: as the Lebanese poet Kahlil Gibran wrote:
When you walk towards the light, the shadow of your burden falls behind you.
When Simeon took the 40 day old Jesus in his arms, and said the child was “ a light for revelation to the Gentiles,” this biblical association of light with God lies behind his words. This child is light, as God is light. This child is God. Jesus will help people see the truth, live in light, and lead them to glory.
And you may know that in John’s Gospel, Jesus says, I am the light of the world. [Jn. 8:12]
The final chapters of the Bible, in Revelation, offer a vision of the end, of heaven, a heavenly city. And the city has no need of sun or moon to shine on it, for the glory of God is its light, and its lamp is the Lamb. [Rev. 21:23] (The Lamb is an image of Jesus.) We almost move beyond metaphor here and say God is light, really the essence of light, as if the sun and the stars are a temporary measure before God becomes all the light we need.
One of the areas of research into light in which St Andrews excels is biophotonics, the interface of biology and physics. This has applications in medicine, surgery, agriculture, and energy. Just last week, there was a report in the media of new research on bioluminescence in plants which may lead to plants being used to light our rooms.
Researchers here in St Andrews are:
- developing wearable Organic Light Emitting Diode light sources for treating cancer
- developing organic vortex lasers
- developing wavelength modulated Raman spectroscopy for the automated label- and fluorescence-free classification of cells which may be cancerous
And in a related area, my favourite:
- observing how an optically excited system relaxes on very fast timescales – or ultrafast relaxation! (Could be handy if stressing about a deadline.)
For these scientists, life and light are intertwined: life gives forth light, and light can help us understand life, manipulate life, and even heal our lives. It is clearly wonderful work. Could I also suggest that biophotonics offers a lovely parallel for what I and other Christians understand by the gift of Jesus – life which gives forth light, and light which can heal our lives.
A final thought. One commentator on this passage gave it the heading, The Light and the Shadow. For the shadow-side, he had in mind Simeon’s words to Mary, “a sword will pierce your soul too.” Indeed, Jesus did enter dark times, of betrayal, arrest, crucifixion and death. Scripture sees darkness as a metaphor for ignorance and for evil. And of course there is far too much evidence for such darkness in our contemporary world – from hatred, violence and war, to poverty, hunger and illness; from loneliness to mental torment.
Our role, perhaps, is to let the light of life shine through us, dispelling darkness where we can. On Thursday, forty students joined members of the Chaplaincy team at the pier for a Holocaust Memorial Pier Walk. We walked towards the most beautiful moon, and we held lanterns lit by light emitting diodes. We walked through the darkness, bearing witness to the light of life shining in every victim of hatred, shining in every act of courage before tyranny, and shining in our dedication to banish the darkness of ignorance and evil. Biophotonics in a different way.
Today, you should have received a little candle as you came into chapel. It’s yours to keep and light – though not in University halls of residence, I’m afraid! It is time now for them to be blessed. Let us pray:
O Gracious God,
you created all things out of nothing,
and let the labour of bees be revealed in the perfection of wax.
Bless and sanctify these candles that their light may be for us a visible reminder
of the true light who enlightens everyone coming into the world.
As these candles, kindled with a visible flame, scatter the darkness of night,
so also may our hearts be enlightened by the invisible fire of the Holy Spirit
that we might avoid the darkness of ignorance and evil,
see your salvation,
and attain to the Light that never fades.
Amen.