There's A Ghost Right Next to You: The Science of Dark Matter

Source: Angela_Yuriko_Smith (via Pixabay.com) Accessed 15 Oct 2017

Dark Matter: The Ghost Right Next to You Is Big As the Universe
​By Heath Shive 

Right next to you.  Right now. There is a ghost as big as the universe. 

You cannot see it.  No device or instrument on Earth can detect it.  But it is there.
 
It is called dark matter. 

Dark matter and dark energy comprise the majority of the universe.  By the numbers, 68% of the universe is comprised of dark energy, 27% is dark matter, and only about 5% of the universe is detectable by modern science.  As one NASA article said, “More is unknown than is known.”

If Undetectable, How Do We Know About Dark Matter?

Early astronomers had noticed that stars were not evenly distributed and instead seemed to form patches and “clouds.”  By the early 20th century, astronomers realized that the “clouds” were actually different galaxies – which meant the Milky Way was not the whole universe. 

Even weirder, these galaxies seemed to form clusters which spun around an unseen axis. 

In the early 1930s, Swiss physicist Fritz Zwicky made measurements of the Coma galaxy cluster.  By measuring the star density, he could estimate the total mass of the galaxies.  He then measured how fast the galaxies were spinning. 

But the galaxies were spinning far too quickly!  They should be flying apart!  But they were stable.

Galaxies Spin, So What? 

Let me borrow an illustration made by Michael Brooks in his book “13 Things That Don’t Make Sense.”  Imagine that you have a tennis ball on the end of a rope.  Now imagine that you are spinning while holding that rope.  Now the ball is spinning in a constant orbit at a constant height. 

Now put a bowling ball on the end of the rope!  Now imagine how fast you would have to spin to have the bowling ball fly in the same orbit as the tennis ball.  You would have to spin much, much faster, right?

The greater the mass, the faster you have to spin to maintain orbit. 

Zwicky noticed that the galaxies were spinning at a far greater velocity than their size would indicate.  They should fly apart!  But they were stable.  Zwicky concluded that the galaxies were actually much, much denser – with an enormous mass that science could not detect. 

Dark Matter Discovered 

Zwicky couldn’t see the extra mass.  It was invisible.  This invisible mass was an order of magnitude greater than the visible mass!  This was the first true discovery of dark matter.

Dark matter and dark energy form the majority of the universe.  They cannot be seen.  They do not create any measurement in the electromagnetic spectrum – and thus are not detectable by any technology that humans possess!

They are ghosts – ghosts as big and wide as the universe. 

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Sources: 

Brooks, Michael.  13 Things That Don’t Make Sense: The Most Baffling Scientific Mysteries of Our Time.  Doubleday, 2008. 

“Dark Energy, Dark Matter.”  Nasa.gov. National Aeronautics and Space Administration.  Accessed 15 October 2017.  https://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy/

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