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.

Atheists have made the claim that certainly humans cannot have any significance in the universe given its size.  Carl Sagan has called our planet a "pale blue dot" in the vast ocean of space and said, "Our posturings, our imagined self-importance, the delusion that we have some privileged position in the Universe, are challenged by this point of pale light. Our planet is a lonely speck in the great enveloping cosmic dark." In the movie Contact, based on Sagan's book of the same title, the statement is made a few times that, "The universe is a pretty big place....  So if it's just us, it seems like an awful waste of space."  The first sentence is undoubtedly true. The second sentence is someone's opinion. But is it also true?  Does the size of our universe mean that there is a lot of wasted space? Does the fact that we occupy a speck in the cosmic domain mean that we are insignificant? Why would any designer or creator invest in so much real estate and still give any significance to the occupants of one tiny rock?

To answer these questions we need to understand the process that has taken place over the last 13.8 billion years to form our planet earth.  There are three things I want to discuss. (1) Could there be any more or any less stuff in the universe than there is in a habitable universe? (2) Where did the elements that make up our planet and us come from? (3) What is the relationship between age and size in the universe?

(1) You may think that there is a lot of wasted stars, planets, and gas in the universe for our isolated planet to have any significance, but it turns out that if there were just a little more matter or just a little less matter, our planet wouldn't be here. As the universe has expanded from the original big bang the amount of matter in the universe dictates its history. If there is too much matter in the universe the gravitational attraction between all matter would have caused the universe to collapse in on itself before there was sufficient time to form stars and galaxies. If there is too little matter the universe would have expanded so fast that gravity could not have coalesced matter into stars and galaxies. So we don't have too few or too many stars and galaxies in the universe than what is necessary for planets and stars to exist today, despite the astronomical numbers (pun intended) listed above.

(2) The initial big bang created very few elements of the periodic table, mostly hydrogen, helium, and some lithium. All other elements necessary for planets and life, including the carbon in our bodies were created by stars at the end of their existence. Like most things in our universe, stars have a life cycle. They are born, they live, and they die. The first stars born were only made up of the hydrogen, helium, and lithium from the big bang. As they died, the process of their death formed many of the other elements of the periodic table using nuclear fusion. Another generation of stars (the second generation) were born from the remnants of the dead first generation of stars. Some of those second generation stars lived and died and in the process of their death made a larger abundance of the elements of the periodic table. It is from the remnants of many of those stars that our sun formed. Our sun is a third generation star and a third generation star is the first kind of star that has enough elements of the periodic table to make planets like our earth and life like us. From the big bang to the formation of a third generation star takes about 9 billion years. Our sun was formed about 9 billion years after the big bang, which was about 4.5 billion years ago. If you start with a big bang, the shortest time it will take to make a planet that can support life like us and to have that planet develop an environment hospitable to advanced life is nearly 14 billion years, the age of our universe.

(3) Finally, since the universe is constantly expanding as it gets older, its size is related to its age. The youngest universe that starts with a big bang and makes a planet to support higher life forms is about 14 billion years. In 14 billion years the universe grows to the size it is today. Since this is the youngest universe to support life like us, it is also the smallest universe that can support life like us.

So we live in the youngest, smallest, universe that we could live in. Any changes in age, size, or number of stars and galaxies would result in a universe that could not support any higher life forms. The statement made in Contact is just wrong and is bad science. Despite the vast size of the universe there is no wasted space, even if it's just us. Now I don't know if there is any other life in the universe or not, but for the sake of argument, let's say that God did want to create a universe with the physical laws we know of and wanted to populate that universe with only one significant species. If so, the end product would be this universe which is the smallest, youngest possible universe with no wasted space and no extra stars or galaxies.  Humans appear in our universe at the earliest time possible. It's almost as if the universe were, indeed, created with us in mind. It is an extremely naive statement to say that the size of the universe alone indicates that humans are insignificant.

Sometimes critics of the Christian God will argue that since they wouldn't do something in a certain way then God wouldn't do it that way either, and so God must not exist. In the case of the universe they argue it would be ridiculous to create such a vast universe with very few places in the universe that are hospitable to life. But the critics are missing some important points. First, though vast, the universe is the smallest it can be to do the job of hosting a life-supporting planet as discussed above. Second, if the goal of the creator is to make a home for humans who do have significance, the infrastructure for that home must be adequate. The critics don't see the overall picture of the purpose of the universe. Let me give you an example. When I was growing up I was fascinated by the space program which had the goal of sending humans to the moon and bringing them back to earth safely. To make such a mission possible, the most powerful rocket ever made was built: the Saturn V.  On top of this rocket that stood 36 stories high was a little tiny command module with barely enough room for three astronauts to sit in. Out of the entire rocket only a tiny fraction of the infrastructure was hospitable to life in space. So I guess the rest of the Saturn V was a colossal waste of space and indicates the lack of any real designer. The size and scope of the Saturn V was exactly what was required to send humans to the moon just as the size and scope of our universe is exactly what is required for us to live. Both the universe and the Saturn V are exquisitely designed to support life in only a tiny region of its entirety. But there is no wasted space. We live in a small big universe.

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