Saturday, February 25, 2017

A Small Big Universe

The universe is unfathomably large. Our galaxy, the Milky Way, is made of around 200,000,000,000 stars and there are about 200,000,000,000 galaxies in the visible universe. The Milky Way galaxy is about 100,000 light years across, which is  9.5 × 1017 km (6 × 1017 miles). (A light year is the distance light travels in a year which is 9,500,000,000,000 km or 6,000,000,000,000 miles.) We can see galaxies that are so far away it has taken about 13 billion years for their light to reach us.  Since the universe is expanding, those galaxies have continued to recede away from us during the time it took their light to reach us. So the present size of the known universe is approximately 93,000,000,000 light years across in all directions. That is, the universe we can see is now a sphere about 9 × 1023 km (6 × 1023 miles) in diameter. We talk about the "visible" or "known" universe because that is all of the universe we can see. We have no idea how large the universe is beyond that.

It is impossible to understand how big this is. Consider something much smaller, the distance to the nearest star which is about 4.3 light years away. If we could travel to that star at about the same speed as the Apollo astronauts traveled to the moon, it would take almost 1 million years to get there. That is just to the closest star in our galaxy! Even if we could travel at the fastest speed of any object ever created by humans it would take about 30,000 years to reach the nearest star.  You can do the math, but even at that extreme speed it would take 700,000,000 years to cross our galaxy.

Friday, February 17, 2017

The World at CERN

And now for something completely different...  The main focus of this blog is to discuss issues relating science and reason to Christianity and God.  However, I have spent the last week at CERN attending meetings, talking with people, trying to develop computer code to analyze data, and other such activities.  So I'm going to take this opportunity to talk about how experimental particle physics research is done within large collaborations like those at CERN.

I am a member of the ATLAS collaboration.  ATLAS is the name given to both the detector that we use to analyze data from proton-proton collisions at the Large Hadron Collider and the group of scientists who use the data from that detector to try to understand the fundamental particles and forces in the universe.  There are currently about 5000 scientists from about 180 institutions in 38 countries who are members of the ATLAS collaboration, with 1200 of those scientists being students working toward their Ph.D.  It takes that many people to operate the ATLAS detector and to analyze all of the data that we take with the detector.

Saturday, February 4, 2017

A Changing Arrow of Time?

This is one post I am not looking forward to writing.  Some of my readers have asked me to comment about alternative theories to the Big Bang which remove the necessity of our universe having a beginning.  I have been thinking for some time about how to write on this subject in a non-technical manner, which is the tone I strive for on this blog.  Because most of these ideas are quite theoretical, requiring complex mathematics and intricate nuances, it is quite a challenge for me to give an accurate and adequate description of most of these proposals, yet still be comprehensible.   Nevertheless, in this post I want to try to discuss the paper by Anthony Aguirre and Steven Gratton (AG) that describes a scenario which they claim requires no beginning.1   I also want to give some thoughts on how their idea fits into the whole discussion of evidence for or against a deity, particularly the Christian God.  My attempt may be an epic fail.

In the model proposed by Aguirre and Gratton, they claim to avoid a beginning by proposing a thermodynamic arrow of time that points in different directions depending on whether the universe is expanding or collapsing.  To understand what this means I need to first take a diversion to discuss what the thermodynamic arrow of time means.  Actually, no one really knows for sure why we experience time moving forward but we do know that a quantity called entropy must increase in any non-reversible process.  Entropy strictly has to do with the number of microstates available to a system. The concept of a microstate can be illustrated by considering two six-sided dice. There is only one microstate available for the dice to roll 2: both must show a one. However, there are six possible microstates available for the dice to roll a 7. The combinations are 1 and 6, 2 and 5, 3 and 4, 4 and 3, 5 and 2, or 6 and 1. Because there are more available microstates, the dice will more often roll a 7. A macroscopic system with more available microstates has a greater entropy than one with fewer microstates. The second law of thermodynamics states that an isolated system will evolve spontaneously to the state with maximum entropy.   This is a statistical idea.  In general, all processes move toward those that are more statistically probable.  That gives us the arrow of time.   Time moves in the direction where entropy increases.