GALAXIES LIKE GRAINS OF SAND--GREAT GRAPHICS GIVE US A BIT OF PERSPECTIVE

Every so often I come across a presentation that makes something I had a vague idea about crystal clear. I invite you to dive into this great piece by Brian Resnick and Javier Xarracina on Vox. It's partly about dark matter, but it uses a series of beautifully done graphics to give us a sense of where the Earth fits into the big picture of the sun, the Milky Way and the hundreds of billions of galaxies in the known universe, all of which are dwarfed in turn by dark matter and dark energy.

 Looking up at the Milky Way--our home galaxy

Credit: Free photos from Pixabay

Please give it a click! You won't be sorry.

And to get a totally different view of the history and immensity of the cosmos, check out this new video zoom out of the depths of the Hubble Legacy Field.

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Thanks to British author Brian Aldiss for the striking phrase "galaxies like grains of sand." That was the title of the American edition of a collection of some of his short stories, published in the UK under the title The Canopy of Time. 

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DARK MATTER FILAMENTS LINK GALAXIES INTO A COSMIC WEB

Scientists still don't know what dark matter is, although there appears to be five times more of it than of normal, visible matter, and cosmologists believe that it has played a crucial role in the evolution of the universe.

Since it doesn't interact with light or other electromagnetic radiation, and barely if at all with normal matter except through gravity, it's not surprising that it's proven excruciatingly hard to detect. A long series of increasingly sensitive experiments have narrowed the range of possible targets, but so far have failed to find actual dark matter particles.

Now, researchers at the University of Waterloo, in Ontario, Canada, have confirmed one of the key predictions of how dark matter should act by imaging for the first time strands or bridges of dark matter linking neighboring galaxies.

Dark matter filaments bridge the space between galaxies in this false colour map. The locations of bright galaxies are shown by the white regions and the presence of a dark matter filament bridging the galaxies is shown in red. Credit: S. Epps & M. Hudson / University of Waterloo

Astronomer Michael Hudson and graduate student Seth Epps detected the dark matter bridges through the gravitational lensing effect they had on the light coming from even-more-distant galaxies. The image above combines the observations of 23,000 galaxy pairs, which allowed the researchers to detect the dark matter filaments with a high degree of statistical certainty.

“For decades, researchers have been predicting the existence of dark-matter filaments between galaxies that act like a web-like superstructure connecting galaxies together,” said Hudson. “This image moves us beyond predictions to something we can see and measure.”

Their work proves the prediction that rather than isolated "island universes," galaxies and even larger galaxy clusters are like beads of condensation on an invisible cosmic web of dark matter.

Beads of water on a spider's web

https://goo.gl/images/RJO6Xe

You can find the original paper here.

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GALAXIES LIKE GRAINS OF SAND

The universe just got ten times more crowded.

Less than a century ago, astronomers believed that the Milky Way galaxy--our home galaxy--comprised the entire universe. In 1924, astronomer Edwin Hubble discovered galaxies, "island universes" far beyond the Milky Way. As telescopes got bigger and better, and eventually were sent into space, researchers estimated that the observable universe--the part of the universe from which light has had time to reach Earth--contained some 120 billion galaxies.

Hubble Ultra-deep field, 2014. Credit: NASA

Today, a team of researchers from NASA and ESA (the European Space Agency) released the results from a new and more accurate 3-D galactic census. The find that for every galaxy astronomers can see with today's telescopes, there are at least 10 that will be detected by the next generations of instruments.

"It boggles the mind that over 90% of the galaxies in the universe have yet to be studied," says the study's lead author, Christopher Conselice.

So it looks as though we live in a universe not with 120 billion other galaxies, but 1.2 trillion. With an average galaxy containing, say, 100 billion stars, that makes the star count around 10 to the 23rd power, or 10 with 23 zeroes after it.

It seems like pretty much every astronomical discovery, starting with Copernicus' shocking revelation in 1543 that Earth is not the center of the cosmos, has had the effect of pointing out that we're not quite as significant in the big scheme of things as we might like to think. 

The good news is that knowing that we're just the inhabitants of the third planet around one star out of a hundred billion in one galaxy out of a trillion does put our current worries--right down to the size of a particular presidential candidate's hands--into perspective.

(And hats off to British science fiction author, Brian Aldiss, for the evocative and prophetic title of his 1960 book, Galaxies Like Grains of Sand.)