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Erin: Welcome to T2A webchat for Wednesday, October 31st. We are meeting physicist Paul Steinhardt. Dr. Steinhardt and Neil Turok of Cambridge University recently published a new book, Endless Universe, in which they propose the ``cyclic model' of the early universe. This is a radical alternative to big bang/inflationary cosmology in which the evolution of the universe is periodic and the key events shaping the large-scale structure of the universe occur before the big bang.

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Mustafa Cankurt: Hi Ms. Brummett and Mr. Steinhardt Please explain what curved space is? Mustafa, Turkey

Paul: Prior to Einstein people believed that space and time were fixed, never changing. But what Einstein taught us is that space and time are actually elastic, they can stretch, shrink, twist and curve, just like an ordinary substance. So when we think about gravity, it is this twisting, curving, stretching, contracting space and particles moving through space react to whatever is happening to the space...so if the space is static, then light moves on simple straight lines, but if the space curves under the influences of energy and matter, then the light will move in straight lines but on a continuously curving space. So it will appear to an outside observer that the light is bending, but at each instance, it really is moving on the straightest possible path through a continuously curving and warping space. In a way it is similar to when you try to walk in a straight line on the earth's surface, your path would take you on an up and down terrain and eventually in a curved circle around the globe.

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Erin: thanks for your live chat question Mustafa. Please email us separately and provide your mailing address. You can reach us at chat@voanews.com

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Erlinda: What do you mean by cyclic model? Is it similar to cycle of project/program planning? Does it mean that the universe itself recycles its system to evolve a new more developed stage?

Paul: By cyclic we mean the universe goes through repeating periods, beginning from space filled with a hot dense soup of matter and radiation, which you might call the big bang -- to a period a trillion years later when it empties out and becomes vacuous and then a new bang occurs that fills the universe with new matter and radiation that produces new galaxies, stars and planets. The average properties from cycle to cycle are predicted to be the same, although the details would be completely different. So you and I would not be having this conversation in some other cycle. But there might be life and planets and beings communicating in some future cycle. So there is not the kind of evolution that I think you are referring to where things change from cycle to cycle, at least not in the type of model that we're currently thinking about.

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Nima Foroud: Under the “Cyclic Universe” theory, are the creation of new matter, galaxies, stars, and planets before each big bang included in the same universe OR do they live in parallel spaces and times? Nima, Iran

Paul: Thanks for your question. In the cyclic universe theory, new matter, galaxies, stars and planets are created in the same space as we currently occupy. So each piece of space continues from cycle to cycle to make new galaxies, stars, planets and life.

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A.K., India (email): What is the use of knowing about the origin of the universe when we know so little about the planet earth and ourselves?

Paul: By studying the origin of the universe we hope to learn something about the fundamental laws of nature that govern the behavior of everything we experience. By better understanding those laws, we can better understand why we are the way we are and why our planet formed and has the properties it has. The connection is not immediate. It may take decades or longer to discover the connection, but almost everything we know about earth and ourselves at present relies on principles that were first learned from studying the cosmos, going back to Newton and earlier.

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Assefa / Tom (email): Do you absolutely neglect God in the creation of the universe? Assefa   Does the cyclic model of the early universe affect the belief in a divine creator? Tom

Paul: As scientists, our role is to try to understand as much as we can about the universe that was created. Over history, we found that the universe can be explained through remarkably simple mathematics and beautiful concepts of symmetry and geometry. I don't believe this neglects a creator. In particular, we do not pretend to explain why it should be explainable by simple mathematics and simple laws, but observing that it is helps us to understand the beauty of what was created and it also helps us to better understand what may happen in the future.

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Adriano (email): Do you think the universe is too complicated for us to understand or do we just need more pieces to complete the puzzle?

Paul: One could well imagine that the universe is too complicated for us to explore. But much to our surprise the more we've tried to understand it, the simpler our explanations have become in the sense that everything that we observe can be described in terms of a few simple principles and laws. In fact, in some sense the universe was simpler back in its earlier history than it is today. Fourteen billion years ago it contained a hot soup of matter and energy that was very uniformly spread and could be described in very simple terms. Over time, as the universe expanded and cooled, that soup coalesced into the complex structure that we see today; of galaxies, planets and stars. So describing the earlier universe is actually easier than describing the present universe. And this gives us hope that we can trace its origins back in time to the big bang and beyond.

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Tom K: Are you saying that matter can be created and destroyed when you talk about new matter?

Paul: Yes, matter can be created and destroyed. Energy is conserved. That is to say that the total amount of energy in the universe does not change over time but matter is only one form of energy and we know how it is possible in the laboratory to create matter from other forms of energy and in the cyclic theory we are saying that what is normally called the big bang is actually a collision that takes gravitational energy and converts it into matter.

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Erin: Thanks for joining us live, Tom. Please send us your mailing address in an email to chat@voanews.com

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Mustafa Cankurt: Hi Ms Brummett and Mr. Steinhardt. Are there signs of species like humans in interstellar space or is this all science fiction? Mustafa, Turkey

Paul: Our cyclic theory doesn't say anything directly about the possibility of life on other planets. However it does say that whatever that probability is, it remains the same in future cycles. I think it's a fair scientific question to ask, whether there is life on other planets. All we can say at the moment is that we have not observed it but we haven't looked very far yet.

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Erlinda: What does the cyclic theory say about black holes? Erlinda, Germany

Paul: Black holes are interesting for the cyclic model because unlike other forms of matter, they are not evaporated and destroyed at any big bang. So whereas the stars, galaxies and planets are obliterated at each bang, the black hole survives from cycle to cycle. They are spread out during each cycle to enormous degree so that it may be that no black holes from previous cycles are anywhere within our range of detection. However in principle, old black holes from previous cycles do exist out there somewhere.

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Erlinda: How is the cyclic model related to Einstein's Theory of Relativity? Erlinda, Germany

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Paul: The cyclic model builds on Einstein's theory of relativity and ideas that go beyond it. We know that Einstein's theory of gravity provides a good description of most of the history of the universe and therefore most of the history according to cyclic theory. But we also know that Einstein's theory is not valid near the big bang. It's missing key ideas, in particular it does not include any quantum physics. So to complete the cyclic theory, we need an improved theory of gravity that includes quantum physics. The best candidate for this at present is what is known as string theory and our cyclic model is built on the elements of string theory, so that we can describe both the bang as well as what happens before and after.

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Mo, Baghdad - Iraq: Hi. So what are the basic differences between the Big Bang and the cyclic theories? Mo in Baghdad

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Paul: The conventional big bang theory says that the big bang was the beginning of everything; space, time, matter and energy -- and that anything that has happened and that affects the universe has only occurred since. It further says that in the future, the space we inhabit today will become empty and vacuous and remain that way forever. The cyclic model says no, the big bang is not the beginning of space and time and in fact the big bang occurred more than once, repeating perhaps once every trillion years. And that the key events that determined the large-scale structure of the universe occurred before the big bang, leaving signals that we can detect. As for the future of the universe, the universe will become empty in about a trillion years but that's not the end of the story. A new bang occurs, creating new matter and energy that begins a new cycle of cosmic evolution.

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Erin: Mo, thanks for joining us live. Please send us your mailing address in an email to chat@voanews.com

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Erin: What are dark matter and dark energy, and what role do they have in the makeup of the universe?

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Paul: According to the cyclic picture, dark energy is related to the force that causes the universe to undergo endless cycling. We imagine, as string theory suggests, that our three-dimensional world floats in a space with an extra dimension, separated by a tiny distance from another three-dimensional world. And these two worlds collide with one another on a regular basis, once every trillion years, due to a force that draws them together -- just as a stretched spring contracts when it is released. When a spring is stretched, it contains a kind of stored energy. Similarly the force that draws these two worlds together has a stored energy that acts just like dark energy, while these two worlds are separated as they are now. As for dark matter, one possibility is that this is matter that is currently in the other world which we can't see but whose gravity we can feel.

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Erin: That wraps T2A webchat. Our thanks to Dr. Steinhardt and to you for joining us. You can learn more about Dr. Steinhardt’s work by going to voanews.com and clicking on the T2A logo graphic. We hope you can join us next Wednesday, November 7th as we meet Internet technology expert Ken Berman. We will discuss Internet filtering and circumventing roadblocks on the Information Superhighway. That’s Wednesday, November 7th at 18 hours universal time on voanews.com See you then!