Christian Long

Patricia Burchat: Leads a Search for Dark Energy

In TED Talks on April 22, 2010 at 8:08 pm

Reflection by DARCY S.

Original TED page w/ speaker bio, links, comments, etc:

Patricia Burchat:  Leads a Search for Dark Energy

As an astrophysics enthusiast, this talk was very exciting for me.

The theories of dark matter and dark energy are currently so enigmatic that it’s difficult to explain in simple terms to an audience with an assumed knowledge of the subject to be relatively blank, and Burchat does an excellent job of summarizing the nature of the universe which proves such particles and energies exist. Despite not having concrete explanations for these theories, it is obvious that these are the beginning steps towards the discovery of something unimaginable.

The concept of dark matter is perfectly rational. Burchat defines dark matter in terms of the effect it has on the rotational orbit velocity that stars and other “ordinary matter” (matter that reacts with the electromagnetic spectrum) in a galaxy. When looking at spiral galaxies, it would be expected that the orbital velocity of a star on the far end of the galaxy would be slower than the orbital velocity of a star closer to the centre of the galaxy. What scientists found, however, is that the speed is actually the same. That means that the stars in the galaxy rotate at the same speed around the centre of the galaxy, or the black hole. For this to happen, scientists suggest that the ordinary matter must be experiencing a gravitational force other than the force emitted by the mass in the centre of the universe. This other force is dark matter, which Burchat says is in a more spherical shape than the galaxy and extends much farther outward than the galaxy.

Although the concept is rational, it’s hard to process dark matter as actual particles of axions and squarks and photinos. Dark matter isn’t actually visible, which makes many people skeptical. Dark matter is matter that doesn’t emit energy which compromises with the electromagnetic spectrum when it reacts. Right now we can’t see dark matter at all, but there is a way that scientists can locate it.

It starts with knowing that galaxies aren’t just randomly sprinkled on the donut of the universe; they appear in clusters. In order for the galaxies to collect in clusters, there must be a gravitational pull that centers them in that cluster. There is only one problem: we can’t see the mass that pulls the galaxies. Burchat explains this my saying there must be a large cloud of mass that is “invisible” so to speak. It even goes further than that. By measuring the speed that the galaxies in that cluster are rotating, they can, in some super awesome astrophysical way, determine the amount of mass in the total cluster of galaxies. It appears that there is more mass than actually visible, which leads scientists to believe they aren’t getting the whole picture.

Of course it’s possible that we can’t literally see it. There are so many levels of interactions of matter in space, and its possible that this dark matter is so sparse (yet dense) that it hardly emits any energy at all when it reacts. That could be why dark matter can shift through ordinary matter that we experience and sense on a daily basis without effort; it reacts on such a small frequency of waves, lower than that of radio waves. Is it also possible that this matter is in a state of matter or existence totally new to us? It could be like plasma, in that it is matter, but completely different than any other state we have yet to know? Matter is matter, after all.

There is a way, Burchat says, that scientists can tell that there is a mass in the galaxy clusters missing.

When Einstein developed general relativity, he said that particles and light itself would be deflected when encountering a substantial amount of matter. To explain the next portion of this analysis, I have recreated the diagram Burchat uses, and added a touch of colour.

Diagram 1

When an observer sees a galaxy through a cluster of galaxies, it would be expected that the light, represented by the horizontal arrows, would travel in a straight line to the observer’s eye. If the mass of the clusters was what is appeared to be, then this would be the case. However it is not what has been observed. What actually happens is seen in Diagram 2.

Diagram 2

Diagram 3

Diagram 2 shows that if the mass of the galaxy cluster were great enough, the light would travel over and past the cluster into the observer’s eye. Because we live in a three-dimensional world, the observer would see a ring of this one galaxy. The light would go around the cluster in all directions, making what is called an “Einstein ring.”

Now Diagram 3 displays where the galaxy would actually appear to the observer. Seeing this same galaxy in multiple spots, scientists can infer where the galaxy actually is. However that is not the part to focus on. What needs to be acknowledged is that the fact that the Einstein’s ring of the one galaxy appears proves that there is more mass in the galaxy cluster than scientists can see. It’s not a miscalculation. Also, by using gravitational lensing, scientists can again calculate, by a different method that mentioned before, the mass of the cluster. Have I lost you?

Unfortunately, that’s not as confusing as it gets when it comes to dark matter and dark energy. Dark energy is even more mysterious.

Dark energy is still a fledgling theory. It’s so new to the science world, it can’t even be formally called a theory so much as a placeholder for an explanation we have yet to encounter. It starts with the recent quarrel over the expansion rate of the universe. In short, scientists were divided in their views about the rate at which space is expanding; many thought the expansion is slowing down and will, in a billion year’s time, cease to expand where as others thought it would keep expanding but always at a slower rate. Some believe the speed will remain constant when it reaches a certain point and others believe it will slow down, stop, and then contract. However, when a number of studies were done world wide, the scientific world was startled. The universe isn’t expanding at a slower rate than a billion years ago; it’s expanding faster.

Dark energy comes into play here. Scientists have yet to answer why the universe is expanding faster. Speaker Patricia Burchat narrowly avoided the explanation or definition of what dark energy physically is. From what I interpreted, it seems to be simply a type of energy, which, in the future, might be able to help scientists explain what could make the universe expand faster. A person by the name of Ellen Jackson who left a comment on the video gave an interesting response as to what dark energy might represent. She said dark energy, or whatever scientists are using to explain the matter, might actually be a property of space itself. Personally, I’m ready to accept any explanation at this early stage of processing the paradox.

Over all, it’s an interesting matter (pardon my pun).

Although many people who possibly claim to know more than they actually do might disagree with the concept of dark matter, at our current position there is no better explanation. Perhaps with the development of more intricate technology able to sense dark matter far out in the universe in greater numbers, as opposed to small labs 5,000 feet underground in South Dakota. Hopefully the mystery of dark matter will be foiled.

Dark energy though, appears today to be something that scientists throw at the hungry-for-information public for them to munch on while the real cooking begins; an appetizer, if you will. It’s all a work in progress that has the potential of being the greatest astronomical discovery in recent years.

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