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| Hubble - infant galaxy (Photo credit: Wikipedia) |
As is usual for me in regard to these kinds of presentations, I have come away with more questions than answers – but I guess that’s the nature of scientific inquiry.
We were presented with a lot of details, but were given three main takeaways:
- The universe is
expanding at an increasing rate.
- This is occurring despite the fact that the force of gravity is relentless – It is a relatively weak force, but never stops.
- Star formation is a relatively recent phenomenon (on the Cosmological time scale), and the rate of formation has slowed down.
He informed us that shortly after the Big Bang, the universe was quite smooth, but got more “lumpy” as gravity slowly took over – forming atom parts, then atoms themselves, and then progressively larger structures, including stars and galaxies.
STARS FORM
Dr. Holder described star formation as a result of the gravitational accumulation of gasses which become denser as time goes by. At some point, the increasing structural pressure within the star resists gravity enough to bring them into equilibrium. At this point, (paraphrasing Dr. Holder), gravity squeezes the gasses until “something happens” internally – the combination of the gravity pressure inward and the internal, structural molecular pressure outward causes the stars to emit light. All the while, the universe continues to expand.Although the universe has been expanding since the Big Bang, one would think that gravity would eventually cause this expansion to slow down. Evidence, however, has been to the contrary. According to the Mcgill website, “ In the late 1990s, astronomers discovered that the expansion of the universe appeared to be accelerating according to cosmic-distance measurements based onthe relatively uniform brightness of exploding stars. Gravity should have beenslowing the expansion, which followed the big bang.”
Many scientists theorize that this proliferation of gravitational compression and star formation continued for some time, but that at some point, the influence of a force deemed “dark energy”* surpassed that of gravity in the universe. They believe that this is when the universe’s expansion rate increased and that the rate of star formation is decreasing due to the available gasses becoming more spread out.
* “The most widely accepted property of dark energy is that it leads to a pervasive force acting everywhere and at all times in the universe. This force could be the result of space having energy, even when it is free of matter and radiation. This energy of empty space, called the cosmological constant, was originally hypothesized by Einstein in order to explain why the Universe was static and not collapsing; he later considered this to be one of his greatest blunders after learning that the universe is not static, but expanding.” – (http://aoc.mcgill.ca/news/channels/2012/april/1/south-pole-telescope-data-shedding-light-dark-energy)
Dr. Holder's Work
This week I am going to attend the next free physics dialogue (Thursday, May 31st at the Aspen Center for Physics), “The Universe Caught Speeding: the Mystery of Dark Energy” to learn more about dark energy’s role in the universe – I’m sure I’ll come away with some more questions!
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