Weird discrepancy in cosmic measurements has cosmologists puzzled

[ This blog is dedicated to tracking my most recent publications. Subscribe to the feed to keep up with all the science stories I write! ]

The growing crisis in cosmology

For The Week:

How rapidly is the universe expanding?

Since Edwin Hubble first discovered in 1929 that galaxies are getting farther apart over time, allowing scientists to trace the evolution of the universe back to an initial Big Bang, astronomers have struggled to measure the exact rate of this expansion. In particular, astronomers want to determine a number called the Hubble parameter, a measurement of how fast the cosmos is expanding as we speak. The Hubble parameter tells us the age of the universe, so measuring it was a major goal for many astronomers in the latter half of the 20th century.

The problem, however, is that measuring the Hubble parameter is, perhaps unsurprisingly, quite difficult. There are multiple methods for doing so, and modern observatories are coming up with different numbers depending on which method they use. It seems the number obtained based on the appearance of the universe shortly after the Big Bang is significantly smaller than the number obtained when looking at measurements involving objects closer by.

[Read the rest at The Week]

The world … er, the universe is flat!

[ This blog is dedicated to tracking my most recent publications. Subscribe to the feed to keep up with all the science stories I write! ]

What’s the Shape of the Universe? A New Study Is Sparking Debate

For Curiosity:

What is the shape of the universe? The universe is everything that we can observe, so we can’t stand outside it to see if it’s shaped like a ball or a potato chip or something else entirely. That doesn’t mean cosmologists aren’t trying to figure it out, though. It’s an important question, though it forces us to expand our ways of thinking about shape. As it turns out, the answer to the question relates to what the universe is made of and how it began. The issue got some public attention recently when three cosmologists claimed the universe curls back on itself, which contradicts many other observations. So who’s right?

[Read the rest at Curiosity.com …]

BICEP3: Revenge of the telescope

[ This blog is dedicated to tracking my most recent publications. Subscribe to the feed to keep up with all the science stories I write! ]

Dusting for the fingerprint of inflation with BICEP3

A new experiment at the South Pole picks up where BICEP2 left off

For Symmetry Magazine:

When researchers with the BICEP2 experiment announced they had seen the first strong evidence for cosmic inflation, it was front-page news around the world. Inflation is the extremely rapid expansion of space-time during its first split second of existence, proposed to explain a number of puzzling properties of the universe, making the BICEP2 results a really big deal. Over the following months, though, the excitement evaporated: After combining their data with other experiments, the BICEP2 team showed that most or all of the signal attributed to inflation was likely produced by galactic dust inside the Milky Way.

But traces of inflation could still be hiding in the data, and that’s why scientists haven’t given up yet. BICEP3, the upgraded version of BICEP2, began collecting data yesterday. The first observations using the fully updated equipment will run through November. [Read the rest at Symmetry Magazine]

How standard are “standard candles”?

[ This blog is dedicated to tracking my most recent publications. Subscribe to the feed to keep up with all the science stories I write! ]

Not-so-standard candles

From Physics World:

The story is already legendary. In the late 1980s and early 1990s, two groups of rival researchers set out to measure the deceleration of the expanding universe. These groups often used the same observatory, sometimes even using the same telescope on consecutive nights. And they both found the same thing, publishing their results at roughly the same time in 1998–1999: the expansion of space–time isn’t slowing down at all. In fact, it’s getting faster. The leaders of those collaborations – Saul Perlmutter and Brian Schmidt – along with Adam Riess of the latter’s group, won the Nobel Prize for Physics in 2011 for this discovery. The implication of the result was that the universe consists not only of visible matter and dark matter, but also a gravitationally repulsive substance. Known as dark energy, the nature of this weird stuff remains as mysterious today as when it was first discovered.

Both groups used certain kinds of exploding stars called type Ia supernovae for their measurements. These supernovae brighten and fade in very similar ways and the current thinking is that this is because they have a common source: the explosion of either one or two white dwarfs, which are the stellar remnants of small-to-medium-mass stars such as the Sun. This consistent brightness allows astronomers to determine how far away the object was when the light left it and for that reason, type Ia supernovae are known as “standard candles” – reliable light- houses in the measurement of cosmic distances.

Or so we all thought.

The rest of this story is in the print edition of Physics World, which you can subscribe to through membership in the Institute of Physics, which costs £15, €20, or $25 per year. You can join by clicking here. You can also get a nice mobile- and tablet-formatted version of the story using the Physics World app, available in the Google Play and iTunes stores. However, if you just want to read the rest of this article, Physics World has kindly allowed me to offer it to you as a PDF download, which looks exactly like the printed version!

Traces of particles from the first second after the Big Bang

[ This blog is dedicated to tracking my most recent publications. Subscribe to the feed to keep up with all the science stories I write! ]

Signs of neutrinos from the dawn of time, less than a second after the Big Bang

First unambiguous observation of the cosmic neutrino background

From Ars Technica:

The first 400,000 years after the Big Bang are inaccessible to us by using light; the material that filled the entire cosmos made it opaque. However, neutrinos interact very little with ordinary matter, so they could travel right through the opaque mess. Lots of these low-mass, fast-moving particles were formed in the first second after the Big Bang, so they could provide a sensitive probe of some of the very earliest moments in the Universe.

Unfortunately, these primordial neutrinos have never been detected directly, and they may have too little energy for us to ever detect them. But a new paper published in Physical Review Letters showed an unambiguous indirect detection using measurements of the cosmic microwave background light. This article marks the first clear measurement of the cosmic neutrino background, which is a significant confirmation of one of the major predictions of the Big Bang model. [Read the rest at Ars Technica…]

Looking to the heavens for neutrino masses

[ This blog is dedicated to tracking my most recent publications. Subscribe to the feed to keep up with all the science stories I write! ]

Looking to the heavens for neutrino masses

From Symmetry Magazine:

Neutrinos may be the lightest of all the particles with mass, weighing in at a tiny fraction of the mass of an electron. And yet, because they are so abundant, they played a significant role in the evolution and growth of the biggest things in the universe: galaxy clusters, made up of hundreds or thousands of galaxies bound together by mutual gravity.

Thanks to this deep connection, scientists are using these giants to study the tiny particles that helped form them. In doing so, they may find out more about the fundamental forces that govern the universe. [Read the rest at Symmetry]

The BICEP2 telescope (foreground) with the South Pole Telescope (SPT) behind. [Credit: Steffen Richter (Harvard University)]

The BICEP2 telescope (foreground) with the South Pole Telescope (SPT) behind. [Credit: Steffen Richter (Harvard University)]

Today was an exciting and stimulating day: the BICEP2 collaboration announced the first measurement of the cosmic microwave background that might tell us whether or not inflation happened. Inflation is the hypothetical rapid expansion of the Universe during its first instants, which explains a lot about why the cosmos appears the way it does. However, data on inflation itself, as opposed to its side-effects, are hard to come by. This new observation could help resolve that…assuming we can figure out why some of its aspects don’t agree with prior observations.

While they do not constitute a direct detection of either primordial gravitational waves (the distortions causing the light polarization) or inflation, the BICEP2 results could provide the best evidence for both that could not be easily explained away by other theories. This observation cannot be the end of the story, however. The measurement of polarization is significantly larger that what is seen in the results of prior observations in a way that cannot be immediately dismissed. Whether the problems are with the interpretation and analysis of the BICEP2 data, or if something more subtle is at work, remains to be seen. [Read more….]

New data offer a peek into the Universe’s first instants