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Astronomy, History of Science & Epistemology, Plastic arts

The Starry Nights of Vincent van Gogh (4) : The Starry Nigh at St-Rémy-de-Provence (2/2)

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Continuation of the previous post The Starry Night of Saint-Rémy-de-Provence (1/2)

In September 2016 I went to the Saint-Paul-de-Mausole monastery, a masterpiece of Provençal Romanesque art built in the vicinity of the Gallo-Roman city Glanum, south of Saint-Rémy de Provence. Part of the building remains today a psychiatric institution. Van Gogh stayed there from May 8, 1889 to May 16, 1890. On the second floor, the room where he was interned has been reconstructed.

Aerial view of the Saint-Paul-de-Mausole asylum and orientation of the window of Van Gogh’s room

Through the window, facing east, we can see the landscape that Van Gogh could contemplate. Even if this landscape has been transformed for a little more than a century, one does not see the hills represented in his painting. In reality, there is the wall of the asylum’s park that encloses a field of wheat, which extends between the asylum and the wall. And there are no large cypress trees in sight, and even less the village of Saint-Rémy.

In fact the small chain of Alpilles is in direction of the South. As for the village of Saint-Rémy and its church tower, which is quite far away in the northern direction, it is just as invisible from the window. We conclude that Van Gogh did not paint the terrestrial part of his Starry Night from what he saw from his window.

He must have gone outside. But when?

My friend Philippe André, a psychiatrist and art lover who studied Van Gogh’s correspondence in depth before publishing his novel Moi, Van Gogh, artiste peintre in 2018, wrote to me that in the first days after his internment on May 8: “At night, he is locked in his room and his equipment is under lock and key in another empty room that he was kindly allocated for this purpose. Moreover, he was very distressed and only managed to paint his own works (Sunflowers, Joseph Roulin…) or to paint very similar elements that were in the park of the asylum (Iris, Lilacs…). No strength, during those first weeks, to paint deep landscapes! “

In fact, when I was finally able to consult Van Gogh’s complete correspondence, I read that on May 9, the day after his arrival, he wrote to his sister-in-law “Jo” (Theo’s wife, therefore):

« Although there are a few people here who are seriously ill, the fear, the horror that I had of madness before has already been greatly softened.

And although one continually hears shouts and terrible howls as though of the animals in a menagerie, despite this the people here know each other very well, and help each other when they suffer crises. They all come to see when I’m working in the garden, and I can assure you are more discreet and more polite to leave me in peace than, for example, the good citizens of Arles.

It’s possible that I’ll stay here for quite a long time, never have I been so tranquil as here and at the hospital in Arles to be able to paint a little at last. Very near here there are some little grey or blue mountains, with very, very green wheatfields at their foot, and pines. » [Letter 772]

From the first sentence it is clear that his anxiety was perhaps not so great, and the rest of the letter confirms that he did begin to paint, but without being able to go beyond the confines of his room or the small garden.

On May 23, he wrote to his brother Theo:

« The landscape of St-Rémy is very beautiful, and little by little I’m probably going to make trips into it. But staying here as I am, the doctor has naturally been in a better position to see what was wrong, and will, I dare hope, be more reassured that he can let me paint.

[…] Through the iron-barred window I can make out a square of wheat in an enclosure, a perspective in the manner of Van Goyen, above which in the morning I see the sun rise in its glory. With this — as there are more than 30 empty rooms — I have another room in which to work. […] So this month I have 4 no. 30 canvases and two or three drawings. » [Letter 776]

This shows that Vincent plans to be able to walk in the countryside outside the monastery very soon. The four canvases he has in progress were painted in the garden.

Between May 31 and June 6 he wrote to Theo asking him to send him canvases, colors and brushes, his Arles supply being exhausted. He adds :

« This morning I saw the countryside from my window a long time before sunrise with nothing but the morning star, which looked very big. […] When I receive the new canvas and the colours I’ll go out a bit to see the countryside. » [Letter 777]

And finally, on June 9, after he had received the canvases and colors sent by Theo, whom he thanked warmly:

« I was very glad of it, for I was pining for work a little. Also, for a few days now I’ve been going outside to work in the neighbourhood. […]I have two landscapes on the go (no. 30 canvases) of views taken in the hills. […] Many things in the landscape here often recall Ruisdael » [Letter 779]

So we have the answer: it was not until the first week of June that Vincent was able to leave the monastery and start painting the landscapes seen from the surrounding countryside. Let’s start with the hills of the Alpilles. As mentioned above, they are invisible from his room, so they were necessarily painted outside. We find the same profile in other paintings of the period:

Wheat Field after the Storm (detail), June 1889.
The Reaper (detail), June 1889

The profile of the hills is quite faithfully rendered, as I was able to see when I found the approximate location where Van Gogh set up his easel (today a field of vines):

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Astronomy, History of Science & Epistemology, Plastic arts

The Starry Nights of Vincent van Gogh (3) : The Starry Nigh at St-Rémy-de-Provence

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Continuation of previous posts Café Terrace at night, in Arles and Starry Night over the Rhône

We left Vincent Van Gogh in September 1888, after he painted his Starry Night over the Rhône in Arles. On October 23rd, Paul Gauguin joined him in the “Yellow House” which he rented and where he stayed for two months. The cohabitation between these two geniuses of painting is not easy. Apart from quarrels of a domestic nature, things went badly wrong on 23 December 1888, after a discussion on painting during which Gauguin argued that one should work with imagination, and Van Gogh with nature. According to the classical thesis, Vincent threatens Paul with a knife; the latter, frightened, leaves the scene. Finding himself alone in a fit of madness, Vincent cuts off a piece of his left ear with a razor, wraps it in newspaper and offers it to an employee of the neighbouring brothel. Then he goes to bed. The police doesn’t find him until the next day, his head bloody and confused. Gauguin explains the facts to them and leaves Arles. He will never see his friend again.

The Yellow House (“The Street”), 1888, oil on canvas, oil on canvas, 72 cm x 91.5 cm.  Credits : Van Gogh Museum, Amsterdam (Vincent van Gogh Foundation)

The day after his crisis, Van Gogh was admitted to hospital. A petition signed by thirty people demanded his internment in asylum or expulsion from the city. In March 1889, he was automatically interned in Arles hospital by order of the mayor while continuing to paint, and on 8 May he left Arles, having decided to undergo psychiatric treatment in the insane asylum at Saint-Paul-de-Mausole, a little south of Saint-Rémy-de-Provence. He stayed there for a year (until May 1890), subject to three bouts of dementia, but between which his pictorial production was extraordinarily rich: he produced 143 oil paintings and more than 100 drawings in the space of 53 weeks.

One of the key works of this period is the Starry Night, now in the Museum of Modern Art in New York.

I have always been fascinated by this nocturnal painting, with its tormented sky in the background, composed of volutes, whirlpools, huge stars and a crescent moon surrounded by a halo of light. In the background, a village with a church steeple overstretched towards the sky, which at first glance is thought to be the village of Saint-Rémy-de-Provence. Due to the position of the moon, the orientation of its crescent horns and the streak of whitish mist over the hills, one does not need to be a great expert to see at first glance that the Starry Night represents a sky just before dawn. Can we go further?

In 1995, while snooping around in a bookshop in Paris, I stumbled upon a booklet entitled La Nuit étoilée: l’histoire de la matière et la matière de l’histoire. It was the French translation of an article booklet published in 1984 in the United States by Albert Boime (1933-2008), professor of art history at the University of California at Los Angeles (“Van Gogh’s Starry Night: A History of Matter and a Matter of History, Arts Magazine, December 1984).

The book is fascinating. The author raises many questions which he tries to answer, notably concerning the date of the painting’s execution and the nature of the astronomical objects represented.

I said in previous posts that Van Gogh painted from nature, and therefore intended to reproduce the night skies as he saw them at the precise moment he began his paintings. I have shown how his Café le soir (Café Terrace at night ) and his Nuit étoilée au-dessus du Rhône (Starry Night over the Rhône), painted in Arles, showed the striking realism he displayed in his pictorial transposition of the firmament. This realism is less obvious in the Starry Night of Saint-Rémy, with its immense sky full of luminous objects, this moon and these far too big stars scattered among vast swirling volutes. Could his representations of the sky have slipped from realism to the wildest imagination, or even to delirium in front of the easel, to the rhythm of his own psychic deterioration?

To answer this question, we must investigate the precise genesis of the work. If, thanks to an astronomical reconstruction, we find a sky identical or close to the one represented in the painting – as was the case with his Arlesian nocturnal works – then we will have proved the realism of the painting, in addition to having dated the sketch to the day and hour.

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Arts, Astronomy, Plastic arts

The Starry Nights of Vincent van Gogh (2) : Starry Night over the Rhône

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As we have seen in the previous post The Starry Nights of   Vincent Van Gogh’s  (1): Café Terrace at night, in Arles, Vincent has therefore been living in the old city of Arles since February 1888. In mid-September, after writing to his sister Wilhelmina (or Willemien according to the scripts) that he wanted “now absolutely to paint a starry sky“, he takes action in his Café Terrace, where he shows a small piece of sky dotted with a few stars of the constellation Aquarius.

A much wider sky is represented in The starry night over the Rhône, painted shortly after, at the end of September. This 72.5 cm x 92 cm canvas, now on display at the Musée d’Orsay in Paris, shows in the foreground, on the bank, a couple seen from the front and moored boats. The silhouettes of roofs and bell towers stand out against the blue of the sky, the city lights reflecting on the river. Among the many stars we recognize in the center the seven stars of the Big Dipper in the constellation Ursa Major, which illuminate a sky in shades of blue. As we will see, the canvas raises more questions than the Café Terrace, due to the incompatibility between the terrestrial view and the celestial view. A detailed survey was conducted in 2012 by photographer Raymond Martinez, whose main elements I am adding here with some personal additions.

The date of execution is confirmed by a letter addressed to his brother Théo on September 29th, when he has just finished the painting of which he attaches a sketch: ”Included herewith little croquis of a square no. 30 canvas — the starry sky at last, actually painted at night, under a gas-lamp. The sky is green-blue, the water is royal blue, the areas of land are mauve. The town is blue and violet. The gaslight is yellow, and its reflections are red gold and go right down to green bronze. Against the green-blue field of the sky the Great Bear has a green and pink sparkle whose discreet paleness contrasts with the harsh gold of the gaslight. Two small coloured figures of lovers in the foreground.”

Sketch of The Starry Night on the Rhone attached to the letter of September 29th to Théo Van Gogh.

On October 2nd, 1888 he sent a slightly different sketch to his painter friend Eugène Boch, with this description: ” And lastly, a study of the Rhône, of the town under gaslight and reflected in the blue river. With the starry sky above — with the Great Bear — with a pink and green sparkle on the cobalt blue field of the night sky, while the light of the town and its harsh reflections are of a red gold and a green tinged with bronze. Painted at night. »

Extract from the letter of October 2nd to Eugène Boch, where Vincent describes his Starry Night
Second sketch attached to the letter of October 2nd

Now let’s look for the place where the painting was done. A sentence from the September 14th letter [Letter 678] to his sister indicates that he certainly painted it on the spot: “Now there’s a painting of night without black. With nothing but beautiful blue, violet and green, and in these surroundings the lighted square is coloured pale sulphur, lemon green. I enormously enjoy painting on the spot at night. In the past they used to draw, and paint the picture from the drawing in the daytime. But I find that it suits me to paint the thing straightaway. It’s quite true that I may take a blue for a green in the dark, a blue lilac for a pink lilac, since you can’t make out the nature of the tone clearly. But it’s the only way of getting away from the conventional black night with a poor, pallid and whitish light, while in fact a mere candle by itself gives us the richest yellows and oranges.“

By comparing the current landscape (day and night) with that of the painting, we can spot the exact positioning of the bell towers of the churches of Saint-Julien and Saint-Martin-du-Méjan, the curve of the Rhône on the surface of which, at night, are still reflected the lights of street lamps (now electric, no more gas!), and in the center, the Pont de Trinquetaille:

From this we deduce the very precise location of Van Gogh’s easel and the angle within which the terrestrial landscape is inscribed: the orientation is South-West. Continue reading →

Arts, Astronomy, Plastic arts

The Starry Nights of Vincent Van Gogh (1) : Café Terrace at Night, in Arles

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“In which space do our dreams live? What is the dynamism of our nightlife? Is the space of our sleep really a rest area? Is it not rather an incessant and confused movement? On all these problems we have little light because we do not find, when the day comes, only fragments of night life. “

In these texts written from 1942 to 1962 (gathered in Le Droit de rêver, PUF, collection “Quadrige”, 2010), Gaston Bachelard celebrates the difficult synthesis of imagination and reflection that seems to him to guarantee, for writers as for artists such as Baudelaire and Van Gogh’s, fidelity to dreamlike values. “A Van Gogh’s yellow is like an alchemical gold, a gold butine like a solar honey. It is never simply the gold of the wheat, the flame, or the straw chair; it is a gold forever individualized by the endless dreams of genius. It no longer belongs to the world, but it is the good of a man, the heart of a man, the elementary truth found in the contemplation of a lifetime. “

Coucher de soleil sur champ de blé près d’Arles (Sunset on wheatfield near Arles), 1888

In the series of notes that I begin here, I will analyze in detail the extraordinary reports that Vincent Van Gogh (1853-1889) maintained with the vision of the Provençal sky.

On February 20, 1888, aged 35, Vincent, the man from dark-heavened Northern Europe, moved to the old city of Arles, in the South of France. Although he arrived in the city by a snowy day, he discovered the Provençal light, brighting day and night. Stunned by the transparency of the firmament, he writes to his brother Theo: “The deep blue sky was spotted with clouds deeper blue than the fundamental blue of an intense cobalt, and others of a blue clearer, like the blue whiteness of the milky ways. In the background, the stars sparkled, clear, green, yellow, white, lighter pink, diamond-like diamonds. ” From then sprout in him the crazy project of painting the sky.

Van_Gogh : Self portrait as an artist, Arles1888

On April 12, he wrote to his friend the painter Émile Bernard: “A starry sky, for example, well — it’s a thing that I’d like to try to do, just as in the daytime I’ll try to paint a green meadow studded with dandelions“. He hesitates however and procrastinates, intimidated by the subject. On June 19, he expressed his hesitation to Émile Bernard: “But when will I do the starry sky, then, that painting that’s always on my mind? Alas, alas, […] the most beautiful paintings are those one dreams of while smoking a pipe in one’s bed, but which one doesn’t make. But it’s a matter of attacking them nevertheless, however incompetent one may feel vis-à-vis the ineffable perfections of nature’s glorious splendours. “

On 9th (or 10th) of July 1888 he confesses to Theo: “But the sight of the stars always makes me dream in as simple a way as the black spots on the map, representing towns and villages, make me dream“.

From word to deed takes place between 9 and 14 September. In fact, he begins on the 9th a long letter addressed to his sister Willemien: “I definitely want to paint a starry sky now. It often seems to me that the night is even more richly coloured than the day, coloured in the most intense violets, blues and greens. If you look carefully you’ll see that some stars are lemony, others have a pink, green, forget-me-not blue glow. And without labouring the point, it’s clear that to paint a starry sky it’s not nearly enough to put white spots on blue-black.“

From left to right, self-portrait of Emile Bernard, friend of Vincent, photographic portraits of his brother Theo and his sister Willemien.

He did not post it and resumed his letter on the 14th. In the meantime he painted his first starry night, the painting is called Cafe Terrace at night (currently at the Kröller-Muller Museum in Otterlo, the Netherlands):

“I started this letter several days ago, up to here, and I’m picking it up again now.  I was interrupted precisely by the work that a new painting of the outside of a café in the evening has been giving me these past few days. On the terrace, there are little figures of people drinking. A huge yellow lantern lights the terrace, the façade, the pavement, and even projects light over the cobblestones of the street, which takes on a violet-pink tinge. The gables of the houses on a street that leads away under the blue sky studded with stars are dark blue or violet, with a green tree. Now there’s a painting of night without black. With nothing but beautiful blue, violet and green, and in these surroundings the lighted square is coloured pale sulphur, lemon green. I enormously enjoy painting on the spot at night“.

Terrasse de café le soir
And on September 16th, he describes his painting to Theo more briefly: “The second [painting of this week] shows the outside of a café, lit on the terrace outside by a large gas-lamp in the blue night, with a patch of starry blue sky.represents the outside of a cafe illuminated on the terrace by a large gas lantern in the blue night. with a corner of starry blue sky. […] The question of painting night scenes or effects, on the spot and actually at night, interests me enormously.“
We know exactly where the painting was executed: Place des hommes, now renamed Place du Forum. The map of Arles in Van Gogh’s time, shown below, shows its location, as well as other intramural sites where Vincent settled to paint La Maison jaune (The Yellow House) in September 1888), the Pont métallique de Trinquetaille (the Metallic Bridge of Trinquetaille) in October 1888) and Nuit étoilée sur le Rhône (Starry Night on the Rhone), on which I will return at length in the following post.
The café, which at that time was called the Terrace, has since been renamed Café Van Gogh. Fortunately, the historic site has not been ransacked by modern constructions as is so often the case elsewhere, and even today the walker immediately recognizes the layout of the streets and buildings painted by Vincent, day and night.
Café Van Gogh nowadays. Night photography shows the light pollution characteristic of urban lighting, violent and useless projectors erasing all traces of the firmament. A huge loss of cosmic feeling …
Now a question that arises is: are the stars he has represented on the canvas randomly arranged, or do they correspond to a real configuration of the night sky?
In the preparatory study for the painting shown below, the sky is just sketched with wiggling lines, without any star. It is quite possible that Vincent made this study during the day .
Preparatory study for the painting, September 1888. Dallas Museum of Art, The Wendy and Emery Reves Collection.
However, in view of van Gogh’s epistolary statements, everything suggests that he wanted to show a certain realism in the pictorial transposition of the firmament seen at night. Since, according to the letter that Vincent sent to his sister Willemien, we know the date of execution (between 9 and 14 September) within a few days, it is possible to check using a reconstitution software astronomical what portion of sky was represented by Vincent, seen from the Forum Square in a direction very close to the South (this is the orientation of the street).
Let’s use the excellent Stellarium software. Position us at the GPS coordinates of the Forum Square, namely 43 ° 40 ‘39.7 “N 4 ° 37’ 37.6” E, set the date from September 9, 1888 at about 10 pm, let us look south and let the map scroll to find a stellar configuration possibly close to that of the table, between 20 and 30° of declination (such is the height of the stars represented in the table).
I once read an article (which I lost references) claiming that it is the legs of the constellation Scorpio, with the stars α (the brilliant Antares), σ, β, δ and Scorpion π. The problem is that between 9 and 14 September, the constellation Scorpio is only above the horizon until 17h UT, after it passes below and can not be seen, even at the beginning of the night which in September falls well later. Also at that time the Moon was at its first crescent in the legs of Scorpio. This is not the correct identification.
Let’s now examine the map of the sky seen between 9 and 14 September 1888 around 22h in the southern extension of the Forum Square: we see the stars of the constellation Aquarius up to magnitude 5, with its characteristic configuration shaped from Y.
Stars of the Aquarius constellation visible to the naked eye between 9 and 14 September 1888 at 22h in the direction of the Cafe de la Terrasse.
 I added the profile of the buildings hiding part of the field of view, traced the characteristic lines connecting the most brilliant stars, and compared with Vincent’s painting:
The identification seems pretty convincing … It also reinforces the epistolary statements in which Vincent expressed his concern to represent a real sky and not imaginary.
This will be even more spectacular in the two famous starry nights painted in Arles in 1888 and Saint-Rémy in 1889. I will analyze them in the same way in the following posts, with the key to very unexpected surprises …

 

Cinema, My books & articles, Sciences

The Warped Science of Interstellar (6/6) : the final equation

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Sequel of the preceding post The Warped Science of Interstellar (5/6)

In november  2014, the Hollywood blockbuster and science-fiction movie Interstellar was released on screens and  much mediatic excitation arose about it.
This is the last one of a series of 6 posts devoted to the analysis of some of the scientific aspects of the film, adapted from a paper I published last spring in Inference : International Review of Science.

Formules

The final equation

At the very end of the film, the scientist’s character called Murph begins to write an equation aimed to solve the problem of the incompatibility between general relativity and quantum mechanics. We can see blackboards covered by diagrams and equations supposed to be a possible way to the « ultimate equation » of a so-called « Theory Of Everything ». If discovered by the scientists, it would eventually help to solve all the problems of humanity. I will not discuss the naivety of such a view, but briefly discuss the question whether the equations on the screen have any meaning.

The complete unification of the four fundamental interactions can be achieved only at very high energy, conditions which prevailed in the very early universe during the so-called « Planck era ».
The complete unification of the four fundamental interactions can be achieved only at very high energy, conditions which prevailed in the very early universe during the so-called « Planck era ».

At first sight we can doubt because the unification of general relativity and quantum mechanics remains unsolved – even if various approaches, such as the loop quantum gravity[1], the string theory[2] (of which the Randall-Sundrum model referred above is a very particular solution) or the non-commutative geometry[3], are intensively explored by theoretical physicists all around the world. Continue reading →

Cinema, Sciences

The Warped Science of Interstellar (5/6) : Time machine and Fifth Dimension

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Sequel of the preceding post The Warped Science of Interstellar (4/6)

In november  2014, the Hollywood blockbuster and science-fiction movie Interstellar was released on screens and  much mediatic excitation arose about it.
This is the fifth of a series of 6 posts devoted to the analysis of some of the scientific aspects of the film, adapted from a paper I published last spring in Inference : International Review of Science.

TIME TRAVEL INSIDE GARGANTUA

Interstellar-FLprStills16-2nd-Batch

In the last part of the film, the main character, Cooper, plunges into Gargantua. There, beware the tidal forces breaking anything up ! Indeed in the Schwarzschild geometry, the tidal forces become infinite as r -> 0 ; so, even for a supermassive black hole like Gargantua, once past safely the event horizon and approaching the central singularity, everything will be ultimately destroyed. Happily for the continuation of the story, Gargantua has a high spin, and its lethal singularity has the shape of an avoidable ring. Thus the space-time structure allows Cooper to use the Kerr black hole as a wormhole ; he avoids the ring singularity and transports to another region of space-time. In the movie he ends up in a five-dimensional universe, in which he will be able to go backwards in time and communicate with his daughter by means of gravitational signals.

Inner structure of a rotating black hole with a ring singularity
Inner structure of a rotating black hole with a ring singularity

A lot of research has been done on whether the laws of physics permit travel back in time or not. Black hole physics gives interesting results but no firm answers. As seen in the post The Warped Science of Interstellar (1/6), according to Penrose-Carter diagrams a rotating black hole could connect myriads of wormholes to different parts of the space-time geometry. Since two events can differ in time as well as in space, it would be possible to pass from one given position at a given time, along a carefully chosen trajectory, through a wormhole, and arrive at the same position but at a different time, in the past or future. In other words, the black hole could be a sort of time travel machine.

Noneless a journey back through time is an affront to common sense. It is difficult to accept that a man could travel back through time and kill his grandfather before he has had the time to produce children. For the murderer could not have been born, and could not have murdered him, and so on… Such time paradoxes have been pleasantly presented in the celebrated series of movies Back to the future.

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Cinema, My books & articles, Sciences

The Warped Science of Interstellar (4/6) : Time dilation and Penrose process

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Sequel of the preceding post The Warped Science of Interstellar (3/6)

In november  2014, the Hollywood blockbuster and science-fiction movie Interstellar was released on screens and  much mediatic excitation arose about it.
This is the fourth of a series of 6 posts devoted to the analysis of some of the scientific aspects of the film, adapted from a paper I published last spring in Inference : International Review of Science.

A HUGE TIME DILATION

The elasticity of time is a major consequence of relativity theory, according to which time runs differently for two observers with a relative acceleration – or, from the Equivalence Principle, moving in gravitational fields of different intensities. This well-known phenomenon, checked experimentally to high accuracy, is called « time dilation ».

The celebrated "smooth watches" by Salvador Dali are a nice metaphor of time elasticity predicted by Einstein's relativity theory.
The celebrated “smooth watches” by Salvador Dali are a nice metaphor of time elasticity predicted by Einstein’s relativity theory.

Thus, close to the event horizon of a black hole, where the gravitational field is huge, time dilation is also huge, because the clocks will be strongly slowed down compared to farther clocks. This is one of the most stunning elements of the scenario of Interstellar : on the water planet so close to Gargantua, it is claimed that 1 hour in the planet’s reference frame corresponds to 7 years in an observer’s reference frame far from the black hole (for instance on Earth). This corresponds to a time dilation factor of 60,000. Although the time dilation tends to infinity when a clock tends to the event horizon (this is precisely why no signal can leave it to reach any external observer), at first sight a time dilation as large as 60,000 seems impossible for a planet orbiting the black hole on a stable orbit.

As explained by Thorne in his popular book, such a large time dilation was a « non-negotiable » request of the film director, for the needs of the story. Intuitively, even an expert in general relativity would estimate impossible to reconcile an enormous time differential with a planet skimming up the event horizon and safely enduring the correspondingly enormous gravitational forces. However Thorne did a few hours of calculations and came to the conclusion that in fact it was marginally possible (although very unlikely). The key point is the black hole’s spin. A rotating black hole, described by the Kerr metric, behaves rather differently from a static one, described by the Schwarzschild metric. The time dilation equation derived from the Kerr metric takes the form:

1 – (dτ/dt)2 = 2GMr/c2rho2, where rho2 = r2 + (J/Mc)2cos2θ.

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Cinema, My books & articles, Sciences

The Warped Science of Interstellar (3/6) : Accretion Disk and Tidal Stress

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Sequel of the preceding post The Warped Science of Interstellar (2/6)

In november  2014, the Hollywood blockbuster and science-fiction movie Interstellar was released on screens and  much mediatic excitation arose about it.

This is the third of a series of 6 posts devoted to the analysis of some of the scientific aspects of the film, adapted from a paper I published last spring in Inference : International Review of Science.

VISUALISATION OF THE ACCRETION DISK

Since a black hole causes extreme deformations of spacetime, it also creates the strongest possible deflections of light rays passing in its vicinity, and gives rise to spectacular optical illusions, called gravitational lensing. Interstellar is the first Hollywood movie to attempt depicting a black hole as it would actually be seen by an observer nearby.

For this, the team at Double Negative Visual Effects, in collaboration with Kip Thorne, developed a numerical code to solve the equations of light-ray propagation in the curved spacetime of a Kerr black hole. It allows to describe gravitational lensing of distant stars as viewed by a camera near the event horizon, as well as the images of a gazeous acccretion disk orbiting around the black hole. For the gravitational lensing of background stars, the best simulations ever done are due to Alain Riazuelo[i], at the Institut d’Astrophysique in Paris, who calculated the silhouette of black holes that spin very fast, like Gargantua, in front of a celestial background comprising several thousands of stars.

BH_LMC_APOD-BR
Gravitational lensing produced by a black hole in a direction almost centered on the Large Magellanic Cloud. Above it one easily notices the southernmost part of the Milky Way with, from left to right, Alpha and Beta Centauri, the Southern Cross. The brightest star, close to the LMC is Canopus (seen twice). The second brightest star is Achernar, also seen twice. © Alain Riazuelo, CNRS/IAP

But perhaps the most striking image of the film Interstellar is the one showing a glowing accretion disk which spreads above, below and in front of Gargantua. Accretion disks have been detected in some double-star systems that emit X-ray radiation (with black holes of a few solar masses) and in the centers of numerous galaxies (with black holes whose mass adds up to between one million and several billion solar masses). Due to the lack of spatial resolution (black holes are very far away), no detailed image has yet been taken of an accretion disk ; but the hope of imaging accretion disks around black holes telescopically, using very long baseline interferometry, is nearing reality today via the Event Horizon Telescope[ii]. In the meanwhile, we can use the computer to reconstruct how a black hole surrounded by a disk of gas would look. The images must experience extraordinary optical deformations, due to the deflection of light rays produced by the strong curvature of the space-time in the vicinity of the black hole. General relativity allows the calculation of such an effect. Continue reading →

Cinema, My books & articles, Sciences

The Warped Science of Interstellar (2/6)

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Sequel of the preceding post The Warped Science of Interstellar (1/6)

One year ago, in november  2014, the Hollywood blockbuster and science-fiction movie Interstellar was released on screens and  much mediatic excitation arose about it.

This is the second of a series of 6 posts devoted to the analysis of some of the scientific aspects of the film, adapted from a paper I published last spring in Inference : International Review of Science.

THE FAST-SPINNING BLACK HOLE « GARGANTUA »

Once on the other side of the wormhole, the spaceship and its crew emerge into a three-planets system orbiting around a supermassive black hole called Gargantua. Supermassive black holes, with masses going from one million to several billion solar masses, are suspected to lie in the centers of most of the galaxies. Our Milky Way probably harbors such an object, Sagittarius A*, whose mass is (indirectly) measured as 4 million solar masses (for a review, see Melia[i]). According to Thorne, Gargantua would be rather similar to the still more massive black hole suspected to be located at the center of the Andromeda galaxy, adding up 100 million solar masses[ii]. Its size being roughly proportional to its mass, the radius of such a giant would encompass the Earth’s orbit around the Sun.

CGal_IR_1al
A view of the Galactic Center in X-rays

CGal_*Keck
The analysis of trajectories of stars orbiting around the Galactic Center leads to estimate the mass of the central black hole at about 4 millions solar masses.

m31
The Andromeda Galaxy (M31), located at 2.2 million light-years

coeurM31_HST
Detailed image of the core of Andromeda Galaxy by the Hubble Space Telescope. The central black hole would have 100 million solar masses.

Such enormous black holes are not a science-fiction exaggeration, since we have the observational clues of the existence of « Behemoth » black holes in faraway galaxies. The biggest one yet detected lies in the galaxy NGC 1277, located at 250 million light-years ; its mass could be as large as 17 billion solar masses, and its size would encompass the orbit of Neptune[iii]. Continue reading →

Cinema, Sciences

The Warped Science of Interstellar (1/6)

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One year ago exactly, in november  2014, the Hollywood blockbuster and science-fiction movie Interstellar was released on screens and  much mediatic excitation arose about it.

This is the first of a series of 6 posts devoted to the analysis of some of the scientific aspects of the film, adapted from a paper I published last spring in Inference : International Review of Science.

interstellar-posterInterstellar  tells the adventures of a group of explorers who use a wormhole to cross intergalactic distances and find potentially habitable exoplanets to colonize. Interstellar is a fiction, obeying its own rules of artistic license : the film director Christopher Nolan and the screenwriter, his brother Jonah, did not intended to put on the screens a documentary on astrophysics – they rather wanted to produce a blockbuster, and they succeeded pretty well on this point. However, for the scientific part, they have collaborated with the physicist Kip Thorne, a world-known specialist in general relativity and black hole theory. With such an advisor, the promotion of the movie insisted a lot on the scientific realism of the story, in particular on black hole images calculated by Kip Thorne and the team of visual effects company Double Negative. The movie also refers to many aspects of contemporary science, going from well-studied issues such as warped space, fast-spinning black holes, accretion disks, tidal effects or time dilation, to much more speculative ideas which stem beyond the frontiers of our present knowledge, such as wormholes, time travel to the past, extra-space dimensions or the « ultimate equation » of an expected « Theory of Everything ».

It is the reason why, beyond the subjective appreciations that everyone may have about the fiction story itself, many people – physicists and science journalists – have taken the internet to write articles lauding or criticizing the science shown in the movie. Kip Thorne has written a popular book, The Science of Interstellar [i], to explain how he tried to respect scientific accuracy, despite the sometimes exotic demands of Christopher and Jonah Nolan, ensuring in particular that the depictions of black holes and relativistic effects were as accurate as possible.

The aim of this article is not to write a (inevitably subjective) review of Interstellar as a fiction story, but to decipher some of the scientific notions, which support the framework of the movie.

AN ARTIFICIAL WORMHOLE IN THE SOLAR SYTEM ?

 In the first part of the film, we are told that a « gravitational anomaly », called a wormhole, has been discovered out near Saturn several decades ago, that a dozen habitable planets have been detected on the « other side » and a dozen astronauts sent to explore them. In particular, one system has three potentially habitable planets, and it is now the mission of the hero, Cooper, to pilot a spaceship through the wormhole and find which planet is more suitable for providing humanity a new home off the dying Earth. Continue reading →

Plastic arts

An Approach to Infinity

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Like the Italian artist and engraver Giovanni Battista Piranesi (1720-1778), whose follower he is, Jean-Pierre Luminet depicts space with passion and melancholy. By repeating ceaselessly black and white checkerboards, he evokes the notion of infinity and generates the dizziness of the glance. By disrupting the laws of classical perspective, he conjugates architectural immobility and time unsettledness. The artist immerses elements in a black ocean, and such a subtle interaction gives the sensation of perpetual time. Infinity is that aspiration felt by the man held on ground by gravitation. Jean-Pierre Luminet depicts this sensation by creating vanishing points towards which one feels irresistibly attracted.

Anne de Commines, Art critics
Cinema, News, Sciences

Black Hole Imaging (2) : Heads and Tails

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 The thought experiments which have been described in my  previous post Back to the basics are more than an intellectual exercise, because if black holes really exist (and we have strong observational arguments to believe that), then there is a good chance that they will be illuminated by a natural light source. For a black hole or a planet the most obvious form of lighting is a star. This star could, for example, be bound to the black hole in a binary system. Although such systems are common throughout our Galaxy, the corresponding black holes would be impossible to detect by this effect, as their image  by reflected light would be drowned in the intense light of the direct image of the star itself.

A much more interesting situation from an observational point of  view is when the source of light comes from a series of rings of matter in orbit around the black hole.  It is believed that a number of black holes are surrounded by such structures, which are called accretion disks. Saturn’s rings are an excellent example of an accretion disk; they consist of amalgamated pieces of rock and ice which reflect the light of the distant Sun, whereas those of a black hole consist of hot gas brighting by itself (another important difference is that the accretion disk of a black hole is continually being supplied with gas, whereas that surrounding Saturn is the remnant of the primordial Solar System).

Planet Saturn and its rings. One can assume that a black hole accretion disc, although made of hot gas instead of rocks and ice, has a similar shape, namely circular thin rings.
Planet Saturn and its rings. One can assume that a black hole accretion disk, although made of hot gas instead of rocks and ice, has a similar shape, namely circular thin rings.

 The gases fall slowly into the black hole, like water in a whirlpool. As the gas falls towards the black hole it becomes hotter and hotter and begins to emit radiation. This is a good source of light: the accretion rings shine and illuminate the central black hole. One can then ask : what would be the apparent image of the black hole accretion disk ? Continue reading →

Cinema, Sciences

Black Hole Imaging (1/3): Back to the basics

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The centre of the black hearth,
of setting suns on the shore :
ah ! well of magic
Arthur Rimbaud (Illuminations)

As probably all of you already know, the Interstellar movie tells the adventures of a group of explorers who use a wormhole to cross intergalactic distances and find potentially habitable exoplanets to colonize. For the scientific part, the film director, Christopher Nolan,  has collaborated with a colleague of mine, the famous physicist Kip Thorne, a specialist in general relativity and black hole theory.

With such a scientific consultant, the promotion of the movie insisted a lot on the realism of the black hole images calculated by Kip Thorne and the team of visual effects company Double Negative. The most striking one shows a glowing accretion disk appearing above, below  and in front of the black hole.

The simulation of a black hole with thin accretion disk as shown in the Interstellar movie

As soon as the movie was displayed on the screens, a lot of physics blogs have commented in details the “Science of Interstellar”. Kip Thorne himself has published a such entitled popular book, to explain how he tried to respect scientific accuracy despite the sometimes odd demands of Christopher Nolan, ensuring in particular that the depictions of black holes and relativistic effects were as accurate as possible.

destinSince, as soon as 1979, I was the first researcher to perfom numerical calculations and publish the simulated image of a black hole surrounded by a thin accretion disk (you can upload the technical article here), to inaugurate this new blog I’ll devote a series of 3 posts to the basics of black hole imaging. A good part is adapted from a chapter of one of my books, published in French in 2006, Le destin de l’univers – unfortunately not yet available in English. Continue reading →

Plastic arts

Luminet’s Illuminations

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Luminet’s reinstated visualization of a finite Universe, albeit one from which we can exit through one face and simultaneously enter through the opposite one, relies upon a keplerian form of mental sculpture that may be described as plastic rather than algebraic. Luminet’s characteristic lithograph, Big Bang, exploits the spatial vocabulary of perspective to evoke realms beyond the three dimensional. Whereas Escher relied on contradictions and oscillating ambiguity in his graphic art, Luminet suggests plunging, interpenetrating and matter organizes itself into structures on the right; the tumbling dice on the left imply irreversible disorganization arising from chance. The remarkable range of Luminet’s creativity in art and science is integral to his agenda to recreate what he calls a « humanism of knowledge » — not that the arts and sciences are somehow to be conflated, because they work in very different ways, with illogical and logical means. But Luminet argues that they well up from the same instincts and intuitions: « I do not believe that we acquire at the beginning the ‘heart of an artist’ or the ‘heart of a scientist’. There is simply within oneself a single devouring curiosity about the world. This curiosity pushes us to explore it through various languages and modes of expression, » he says.

Martin Kemp, professor of the history of art at the University of Oxford. Excerpt from “Luminet’s Illuminations : Cosmological Modelling and the Art of Intuition”, Nature, 20 november 2003, vol. 426, p. 232