Dark skies: a view of the milky way during a meteor shower, Myanmar. Photo: Getty
Show Hide image

Dark energy vs dark matter: a battle of two cosmic monsters

Michael Brooks’s Science Column.

It might be the most prestigious journal in physics, but the Physical Review Letters is no good at teasers. Early in November it published a paper entitled: Indications of a Late-Time Interaction in the Dark Sector. Hardly a great headline for what should have been, in the style of Alien v Predator, “Dark Matter v Dark Energy” – a story of two cosmic monsters locked in eternal conflict.

We believe these monsters exist, but we haven’t seen either of them and we know very little about them. We have suspected the existence of dark matter since 1933, when a Swiss astronomer noticed something odd about the way galaxy clusters spin. They looked like they were being held together by the gravitational pull of invisible matter, which he duly named dark matter. We have been trying to see the stuff ever since, to no avail.

Dark energy is a more recent idea. It, too, comes from astronomical observations, this time of supernovae. A 1998 analysis of the light from these stellar explosions suggested that not only is the universe expanding, but this expansion is getting faster all the time. That can only happen with the help of energy from some unknown source – hence dark energy.

Together, dark energy and dark matter make up 96 per cent of the universe. Now, it turns out, dark energy may be consuming the dark matter.

The discovery came from more observations: this time, of the rate at which cosmic structures form. Dark matter seeds galaxy formation, but galaxies aren’t forming as fast as we would expect. This would make sense if dark matter were disappearing from the universe, but various straightforward explanations for why that might occur have failed to correspond with the observed facts. Now a team of British and Italian researchers has created a computer model that does match the observations. Critical to its success is the idea that dark matter is slowly being converted to dark energy.

According to the simulation, the ingestion of dark matter would be a relatively recent phenomenon, beginning roughly eight billion years ago. If it is really happening, it is important to understand, because our attempts to chart the history of the universe depend on dark matter’s role in forming cosmic structures.

Working from observations of the cosmic microwave background radiation, which came into being roughly 300,000 years after the Big Bang, researchers have shown that the radiation’s distribution through the universe would have seeded long filaments of dark matter. The gravitational pull of these filaments attracted the first atoms of normal matter, gradually creating stars and galaxies in long strings. This is the kind of structure we see now.

Yet if dark energy is slowly taking over from dark matter our previous calculations of cosmic history will have to be corrected. And intriguingly (spoiler alert), it will change our predictions. If dark energy is consuming dark matter, the universe will become dominated by dark energy more quickly than previously thought. That will precipitate an inglorious finale in which dark energy’s repulsive power pushes everything interesting away from us.

Eventually, all the other galaxies will be so far away, and receding so fast, that their light will never reach what remains of our Milky Way. Nearby stars will burn out. Our sun is expected to end its life as a huge single crystal of carbon: a dark diamond in the sky, with no surrounding starlight to make it sparkle.

Afterwards, all the atoms will drift apart and then the fundamental particles of matter will slowly decay to nothing. It’s not a Hollywood ending, but don’t complain that you weren’t warned. 

Michael Brooks holds a PhD in quantum physics. He writes a weekly science column for the New Statesman, and his most recent book is At The Edge of Uncertainty: 11 Discoveries Taking Science By Surprise.

This article first appeared in the 27 November 2014 issue of the New Statesman, The rise of the insurgents

Joshua M. Jones for Emojipedia
Show Hide image

The emojis proposed for release in 2016 are faintly disturbing

Birds of prey, dead flowers and vomit: Emojipedia's vision for 2016. 

Since, as we're constantly being told, emojis are now the fastest growing languge in the UK, it seems only appropriate that its vocabulary should expand to include more commonly used images or ideas as its popularity increases. 

Next year, the Unicode Consortium, which decides which new codes can be added to the emoji dictionary, will approve a new round of symbols. So far, 38 suggestions have been accepted as candidates for the final selection. Emojipedia, an online emoji resource, has taken it upon itself to mock up the new symbols based on the appearance of existing emojis (though emojis are designed slightly differently by different operating systems like Apple or Android). The full list will be decided by Unicode in mid-2016. 

As it stands, the new selection is a little... well, dark. 

First, there are the faces: a Pinocchio-nosed lying face, a dribbling face, a nauseous face, an upset-looking lady and a horrible swollen clown head: 

Then there's what I like to call the "melancholy nighttime collection", including a bat, owl, fox, blackened heart and dying rose: 

Here we have a few predators, thrown in for good measure, and a stop sign:

There are a few symbols of optimism amid the doom and gloom, including a pair of crossed fingers, clinking champagne glasses and smiling cowboy, plus a groom and prince to round out the bride and princess on current release. (You can see the full list of mock-ups here). But overall, the tone is remarkably sombre. 

Perhaps as emoji become ever more popular as a method of communication, we need to accept that they must represent the world in all its darkness and nuance. Not every experience deserves a smiley face, after all. 

All mock-ups: Emojpedia.

Barbara Speed is a technology and digital culture writer at the New Statesman and a staff writer at CityMetric.