Hold a wineglass in front of a light. And empty one, that is, and you will see the image behind the wineglass distort and twist.
In the vastness of space there is a similar effect known as Gravitational Lensing and it has allowed astronomers and astrophysicists to delve deeper into the past of the universe and its composition.
But it’s not as simple as holding a wine glass up to a light.
Hubble has found some incredible objects peering into the abyss but arguably the most startling ones have been like the galaxies in the image below.
As you can see, light doesn’t travel in a straight line like it wants to. Space curves and light bends with it.
This was a seminal discovery that has allowed scientists to map the gravitational influence of clusters and galaxies around the universe. The gravitational influence that can only be accounted for with the existence of dark matter.
The normal matter, or ‘light’ matter, of the galaxies is not enough to account for the huge lensing effects that can be seen. Mathematically, there has to be something else that we cannot yet detect directly increasing the gravitational pull of the galaxy cluster.
In comes dark matter, a mysterious state of matter that cannot be detected directly by any instrument we currently posses. As previously mentioned, however, the effects could not be more obvious.
Dark matter is a difficult concept to wrap your head around, mostly because no one truly understands it, knows what it is made of, or how it is formed. There are theories, but so far, as we can only measure it indirectly, none of those have a solid basis underpinning them.
One thing is for sure though, gravitational lensing is an incredibly powerful tool that will only become more useful as our technology and understanding grows.
Further Reading/References:
Gravitational Lensing (hubblesite.org)
Discoveries – Highlights | Shining a Light on Dark Matter | NASA
Nature’s Lens: How Gravity Can Bend Light Like a Telescope | Space
Physics and Fiction 
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