The dark side of cosmology

The components of our universe. Dark energy comprises 69% of the mass energy density of the universe, dark matter comprises 25%, and “ordinary” atomic matter makes up 5%. Three types of neutrinos make up at least 0.1%, the cosmic background radiation makes up 0.01%, and black holes comprise at least 0.005%. Credit: Science/AAAS

It's a beautiful theory: the standard model of cosmology describes the universe using just six parameters. But it is also strange. The model predicts that dark matter and dark energy – two mysterious entities that have never been detected—make up 95% of the universe, leaving only 5% composed of the ordinary matter so essential to our existence.

In an article in this week's Science, Princeton astrophysicist David Spergel reviews how cosmologists came to be certain that we are surrounded by matter and energy that we cannot see. Observations of galaxies, supernovae, and the universe's temperature, among other things, have led researchers to conclude that the universe is mostly uniform and flat, but is expanding due to a puzzling phenomenon called dark energy. The rate of expansion is increasing over time, counteracting the attractive force of gravity. This last observation, says Spergel, implies that if you throw a ball upward you will see it start to accelerate away from you.

A number of experiments to detect dark matter and dark energy are underway, and some researchers have already claimed to have found particles of dark matter, although the results are controversial. New findings expected in the coming years from the Large Hadron Collider, the world's most powerful particle accelerator, could provide evidence for a proposed theory, supersymmetry, that could explain the dark particles.

But explaining dark energy, and why the universe is accelerating, is a tougher problem. Over the next decade, powerful telescopes will come online to map the structure of the universe and trace the distribution of matter over the past 10 billion years, providing new insights into the source of cosmic acceleration.

Yet observations alone are probably not enough, according to Spergel. A full understanding will require new ideas in physics, perhaps even a new theory of gravity, possibly including extra dimensions, Spergel writes. "We will likely need a new idea as profound as general relativity to explain these mysteries."

When that happens, our understanding of the dark side of cosmology will no longer accelerate away from us.

Comments

This strange mineral grows on dead bodies and turns them blue

If you were to get up close and personal with Ötzi the Iceman – the 5,000-year-old mummy of a tattooed , deep-voiced man who died and was frozen in the Alps – you’d notice that his skin is flecked with tiny bits of blue. At first, it would appear that these oddly bluish crystal formations embedded in his skin are from freezing to death or some other sort of trauma, but it’s actually a mineral called vivianite (or blue ironstone) and it happens to form quite often on corpses left in iron-rich environments. For Ötzi, the patches of vivianite are from him resting near rocks with flecks of iron in them, but other cases are way more severe. According to Chris Drudge at Atlas Obscura , a man named John White was buried in a cast iron coffin back in 1861. During those days, coffins often had a window for grieving family members to peer inside even if the lid was closed during the funeral. Sometime after he was buried, that window broke, allow...

It's Official: Time Crystals Are a New State of Matter, and Now We Can Create Them

Peer-review has spoken. Earlier this year , physicists had put together a blueprint for how to make and measure time crystals - a bizarre state of matter with an atomic structure that repeats not just in space, but in time, allowing them to maintain constant oscillation without energy. Two separate research teams managed to create what looked an awful lot like time crystals back in January, and now both experiments have successfully passed peer-review for the first time, putting the 'impossible' phenomenon squarely in the realm of reality. "We've taken these theoretical ideas that we've been poking around for the last couple of years and actually built it in the laboratory," says one of the researchers , Andrew Potter from Texas University at Austin. "Hopefully, this is just the first example of these, with many more to come." Time crystals are one of the coolest things physics has dished up in recent months, because they point to a...

The Dark Side Of The Love Hormone Oxytocin

New research shows oxytocin isn't the anti-anxiety drug we thought it was. Oxytocin, the feel-good bonding hormone released by physical contact with another person, orgasm and childbirth (potentially encouraging monogamy ), might have a darker side. The love drug also plays an important role in intensifying negative emotional memories and increasing feelings of fear in future stressful situations, according to a new study. Two experiments performed with mice found that the hormone activates a signaling molecule called extracellular-signal-related kinases (ERK), which has been associated with the way the brain forms memories of fear . According to Jelena Radulovic, senior author on the study and a professor at Northwestern University's medical school, ERK stimulates fear pathways in the brain's lateral septum, the region with the highest levels of oxytocin. Mice without oxytocin receptors and mice with even more oxytocin receptors tha...

Aestus Ajith

Search This Blog