Cosmology Archives

March 1, 2020March 1, 2020 by Matt Williams

What is the Steady State Hypothesis?

Artist's impression of the Milky Way Galaxy. Credit: ESO

When it comes to our cosmic origins, a number of theories have been advanced throughout the course of history. Literally every culture that’s ever existed has had its own mythological tradition, which naturally included a creation story. With the birth of the scientific tradition, scientists began to understand the Universe in terms of physical laws that could be tested and proven.

With the dawn of the Space Age, scientists began testing cosmological theories in terms of observable phenomena. From all of this, a number of theories emerged by the latter half of the 20th century that attempted to explain how all matter and the physical laws governing it came to be. Of these, the Big Bang Theory remains the most widely accepted while the Steady-State Hypothesis has historically been its greatest challenger.

February 13, 2020February 13, 2020 by Matt Williams

Astronomers Simulated How the Universe Would Look Without Dark Matter

Since the 1960s, there has been a general consensus among astronomers and cosmologists that the majority of the Universe is made up of an invisible, mysterious mass (known as Dark Matter). While scientists still haven’t identified the candidate particle that makes up this mass, indirect tests and simulations have shown that Dark Matter must exist in order for the Universe to be the way it is.

In a fascinating twist, a team of European researchers conducted a simulation that looked at a Universe without Dark Matter. Using an alternative theory known as MOdified Newtonian Dynamics (MOND), the team created a computer simulation in which the galaxies were actually very similar to what we see in the Universe today. These findings could help to resolve one of the most enduring mysteries of modern cosmology.

February 6, 2020February 6, 2020 by Brian Koberlein

Did Neutrinos Stop The Early Universe From Annihilating Itself?

Illustration of the Big Bang Theory — The Big Bang Theory: A history of the Universe starting from a singularity and expanding ever since. Credit: grandunificationtheory.com

We can create matter from energy in the lab. Particle accelerators do this all the time. When we do, half of what is created is matter and the other half antimatter. There is a symmetry in physics that requires matter and antimatter to appear in equal amounts. But when we look around the universe, what we see is matter. So how did the big bang create all the matter we see without creating an equal amount of antimatter? The answer could be neutrinos.

January 17, 2020January 17, 2020 by Brian Koberlein

The Debate Over Cold Dark Matter Warms Up As Astronomers Take Its Temperature

An artist's impression of the cosmic web, the filamentary structure that fills the entire Universe. Credit: M. Weiss/CfA

Dark matter has long been one of the most mysterious things in the cosmos. It was first proposed in the 1930s as an idea to address stellar motion in some galaxies. The first solid evidence of dark matter was gathered by Vera Rubin, who studied the rotational motion of galaxies. The motion of these galaxies didn’t add up unless they contained a large amount of unseen mass. There must be some exotic, invisible matter unlike anything known before.

If dark matter exists, then it must have two major properties. First, it cannot interact strongly with light, otherwise we would see it and it wouldn’t be “dark.” Second, it must interact with other matter gravitationally, to make visible matter move in strange ways. We know of several things that satisfy those conditions, such as neutrinos or tiny black holes, but these can’t be dark matter. We know this in part because we are now able to take its temperature.

January 11, 2020January 11, 2020 by Brian Koberlein

There’s a new method to measure the expansion rate of the Universe, but it doesn’t resolve the Crisis in Cosmology

The venerable Hubble Space Telescope. After 30 years, it's still a productive scientific workhorse. Image Credit: NASA/ESA

In a recent post I wrote about a study that argued dark energy isn’t needed to explain the redshifts of distant supernovae. I also mentioned we shouldn’t rule out dark energy quite yet, because there are several independent measures of cosmic expansion that don’t require supernovae. Sure enough, a new study has measured cosmic expansion without all that mucking about with supernovae. The study confirms dark energy, but it also raises a few questions.

January 8, 2020January 8, 2020 by Brian Koberlein

New Research Casts A Shadow On The Existence Of Dark Energy

The cosmic distance ladder for measuring galactic distances. Credit: NASA,ESA, A. Feild (STScI), and A. Riess (STScI/JHU)

The universe is expanding. When we look in all directions, we see distant galaxies speeding away from us, their light redshifted due to cosmic expansion. This has been known since 1929 when Edwin Hubble calcuated the relation between a galaxy’s distance and its redshift. Then in the late 1990s, two studies of distant supernovae found that the expansion of the universe is accelerating. Something, some dark energy, must be driving cosmic expansion.

November 28, 2019November 28, 2019 by Evan Gough

Astronomers Are About to Detect the Light from the Very First Stars in the Universe

The Murchison Widefield Array radio telescope in remote Western Australia. Brown University.

A team of scientists working with the Murchison Widefield Array (WMA) radio telescope are trying to find the signal from the Universe’s first stars. Those first stars formed after the Universe’s Dark Ages. To find their first light, the researchers are looking for the signal from neutral hydrogen, the gas that dominated the Universe after the Dark Ages.

November 26, 2019November 26, 2019 by Brian Koberlein

A Fifth Fundamental Force Could Really Exist, But We Haven’t Found It Yet

Simulation of dark matter and gas. Credit: Illustris Collaboration (CC BY-SA 4.0)

The universe is governed by four fundamental forces: gravity, electromagnetism, and the strong and weak nuclear forces. These forces drive the motion and behavior of everything we see around us. At least that’s what we think. But over the past several years there’s been increasing evidence of a fifth fundamental force. New research hasn’t discovered this fifth force, but it does show that we still don’t fully understand these cosmic forces.

November 10, 2019November 10, 2019 by Matt Williams

Watch a Simulation of a Galaxy, From the Big Bang Until the Present Day

Since the mid-20th century, scientists have had a pretty good idea of how the Universe came to be. Cosmic expansion and the discovery of the Cosmic Microwave Background (CMB) lent credibility to the Big Bang Theory, and the accelerating rate of expansion led to theories about Dark Energy. Still, there is much about the early Universe that scientists still don’t know, which requires that they rely on simulations on cosmic evolution.

This has traditionally posed a bit of a problem since the limitations of computing meant that simulation could either be large scale or detailed, but not both. However, a team of scientists from Germany and the United States recently completed the most detailed large-scale simulation to date. Known as TNG50, this state-of-the-art simulation will allow researchers to study how the cosmos evolved in both detail and a large scale.

November 6, 2019November 6, 2019 by Brian Koberlein

New Research Suggests that the Universe is a Sphere and Not Flat After All

Diagram showing the Lambda-CBR universe, from the Big Bang to the the current era. Credit: Alex Mittelmann/Coldcreation

The universe is a seemingly endless sea filled with stars, galaxies, and nebulae. In it, we see patterns and constellations that have inspired stories throughout history. But there is one cosmic pattern we still don’t understand. A question that remains unanswered: What is the shape of the universe? We thought we knew, but new research suggests otherwise, and it could point to a crisis in cosmology.