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Skywatching

Dark energy matters

Until very recently, one of the wry jokes about fast radio bursts (FRBs) is that the number of theories attempting to explain them was bigger than the number of FRBs that have been detected.

The CHIME (Canadian Hydrogen Intensity Mapping Experiment) radio telescope is changing that. This instrument has a huge field of view - much of the sky -  and is catching lots of them.

Lets hope this will lead us to get a better idea of what they are. All we know at the moment is that very short (millisecond) bursts of radio emission are coming to us from millions or billions of light years away.

The transmitted energy must be huge, so big the only engines we know of that can drive them are neutron stars and black holes. We hope the number of theories will soon start to drop.

Theories are the currency of science. Coming up with a new theory is a lot more than having a casual idea to explain something we see. The first step is observing something and coming up with a possible physical process or set of physical processes to explain it. That could be a casual idea.

The science starts at the next step. This involves searching the literature for other work on the subject and then using this to flesh out the idea to generate a coherent series of physical and mathematical arguments to account for what was observed. This is not the end of the story.

That new theory must make predictions. If it is correct, there will be other consequences we can look for in new observations. The theory must predict things that can be tested. Unless it does this, it is not a proper theory and is useless.

If a theory survives a long period of detailed examination and testing, it may finally be recognized as a "law" — one of the fundamental rules used by Mother Nature to run the universe.

Isaac Newton provided us with good examples. He came up with a simple theory. I

f you push something with a steady force, an object will accelerate at a constant rate.

If you double the mass of the object, it will accelerate at half that rate.

On the other hand, if you push with twice the force, the object will accelerate twice as rapidly.

The consequences of this simple idea are now recognized as Newton's Laws of Motion.

He also theorized that objects attract each other with a force related to their masses and the distance between them. He came up with the idea of gravity.

Expressed mathematically Newton's Laws of Motion and Gravity have been tested and used over and over again, successfully, and are now recognized as fundamental Laws of Nature.

That is why scientists are so unhappy with the concepts of dark matter and dark energy.

When we saw that in most galaxies the stars orbiting in them are moving too quickly, we concluded the masses of the galaxies are much bigger than we thought. However, we cannot see that missing mass.

Someone suggested this invisible mass is made up of Dark Matter, an otherwise totally invisible "something" invented to make our measurements make sense.

The expansion of the universe is speeding up. This does not make sense. If all the objects in the universe are pulling at all the other objects, gravity should be slowing the expansion down.

The only way the expansion can accelerate is if some unknown outward force is at work.

Enter the idea of Dark Energy. As in the case of Dark Matter, we have just given something a name, we have no explanations or lines of analysis to follow.

This could change. The CHIME radio telescope is intended to map the hydrogen in the very young universe. This is when dark energy would be very active in starting the first galaxies to form.

This won't necessarily lead us straight to a theory, but at least it might tell us which way to go.

  • Mars lies low in the west after sunset.
  • Jupiter rises around midnight
  • Saturn rises at 2 a.m.
  • The Moon will reach first quarter on the 11th.

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About the Author

Ken Tapping is an astronomer born in the U.K. He has been with the National Research Council since 1975 and moved to the Okanagan in 1990.  

He plays guitar with a couple of local jazz bands and has written weekly astronomy articles since 1992. 

Tapping has a doctorate from the University of Utrecht in The Netherlands.

[email protected]



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The views expressed are strictly those of the author and not necessarily those of Castanet. Castanet does not warrant the contents.

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