The Future of Cosmology. What Will We Learn Next? A talk by Geraint Lewis at the Macarthur Astronomy Forum.
Thu, 24. October 2013
Astro-Speaker Watch - October 2013
Professor Geraint Lewis is one of my favourite astronomers. He is always willing to talk to the Society, always willing to answer questions and always looking for ways to explain cosmology. I admire his intellect, his outstanding knowledge of cosmology and his dynamic speaking style.
However, one of the things that intrigues me about Cosmology is that there appears to be no real understanding in layman's terms, of the fabric of the Universe. During the talk, Geraint touched on the accelerating expansion of the Universe and afterwards I asked Geraint two questions:
- Is it space which is expanding or is it spacetime?
- What is space (or spacetime) in laymen's terms? What does it consist of or how could he describe it? We know that it is expanding; we know that it is warped by massive bodies; and we know that even in a perfect vacuum, it has intrinsic energy, causing particle pairs to be created and annihilated. If it has properties like this, then rather than being 'nothing' surely it is 'something'?
Geraint informed me that for practical purposes it can be considered that space is expanding (rather than space-time) but his answer to the second question left me dissatisfied. A few years back I asked him the same question and he told me that space-time is a mathematical concept. So this time I asked for an answer that goes beyond that. This time he again pointed towards mathematics but he also said that cosmologists were not really looking for an answer to that question. That has left me pondering......
Here are images of some of Geraint's lecture slides:
The Hubble Constant, once the source of a huge debate between those who believed it was 50 and those who believed it was 100, was eventually agreed at about 73 (now refined to about 68 km/sec/kpc according to Wikipedia).
The Big Bang model is now well established and all the evidence supports it.
The process of the Big Bang in creating matter as we know it is well established and our observations and modelling are consistent. (Except for the very earliest tiny fraction of a second where our knowlege of physics breaks down, due to the apparent incompatibility of quantum mechanics and general relativity).
We now know that the Universe is neither static, nor shrinking. It is expanding at an accelerating rate.
The detailed Microwave background established by the recent Planck Mission complies exactly with the expected computer power diagram modelling.
We know the exact composition of the Universe (both now and just after the Big Bang) and we know that the early Universe was dominated by dark matter but that it is now dominated by dark energy.
Computer modelling predicts more dwarf galaxies than we observe around the Milky Way and local galxies such as M31.
We need to stretch the Hubble Diagram to more distant objects using gamma ray bursts, because....
....we have no idea what dark energy is.....
.....and we need a better understanding of gravity.
The long term future of the Universe is bleak, as long after the Milky Way and M31 merge, the expanding Universe will "hide" all other galaxies beyond our "Cosmic Horizons".
Cosmologists of the far future will see nothing outside the MW-M31 galaxy and the CMB will be stretched so flat it will be undetectable. Cosmologists will be out of work and the single Island Universe theory of the early twentieth century will become accepted again.
So there are many things cosmologists still need to know about, including gravity, dark energy, dark matter. We also need to find that elusive "Theory of Everything" (TOE) which will marry together general relativity & gravity with Quantum Mechanics & the weak, strong and electromagnetic interactions.
To that I would personally add that I need to know what the fabric of space/space-time is!
- Thanks Geraint for a fantastic lecture!
- Next Month at Macarthur Astronomy Forum: Galaxies of the Local Universe Dr. Ángel R. López-Sánchez (AAO)
- This series of monthly articles originated as contributions to Prime Focus, the monthly journal of Macarthur Astronomical Society. Since the journal ceased, I have continued to write about our guest speaker's presentations and you can view all > twenty articles here <
- This site is my personal blog site and is not the official Macarthur Astronomical Society Site. R.P.