Gravity is a universal force that acts upon all bodies with mass. It would not do if one day you became impervious to gravity and could not put your feet down on the floor next to your bed. Each day we get up and trust that gravity will still pull in the same direction it did yesterday. Mathematics works and can explain things around us. Today, one plus two equals three. The circumference of a circle is pi (3.14159...) times the diameter of the circle. We can count on these things being true tomorrow. God could have created a universe in which these basic principles changed every few moments of time. Without these bedrock principles of our universe, chaos would reign and we would be in constant danger.
Our earth is in a place in our galaxy that makes it possible for life. At the centre of galaxies such as our own there is a black hole and a lot of deadly gamma rays and x-rays. Such rays would blast DNA to bits if we lived closer to the centre of the galaxy and this would make it impossible for life as we know it to exist. Furthermore, this planet on which we live is, on average, 150 million kilometers from the sun and so the life-giving energy of the sun takes about eight and a half minutes to get to us. If we were any closer to the sun our planet would be too hot for our kind of life. The average temperature on the planet Venus is 460 degrees C. Any further away and it would be too cold for us. The average temperature on Mars is -55 degrees C with an extreme range from -123 degrees C to 27 degrees C.
The planet earth has an orbit that is stable and is not unbalanced by other stars or planets in the vicinity. Thus, the duration of our orbit around the sun remains constant and we are not thrown about in a fashion that would make tidal forces extreme and land surfaces much more susceptible to large earthquakes. Our earth rotates at a relatively rapid rate around its polar axis and, much like a smooth running rotisserie, this rapid rotation keeps the entire earth warming quite nicely without extreme differences in temperature between night and day. Plants that rely on photosynthesis function well in this type of environment.
Earth is also tilted at approximately 23 degrees relative to the polar axis (23.44 degrees presently - varying between 22.1 and 24.5 degrees). When you purchase a globe, that represents our planet, it usually comes in a stand that shows this 23 degree tilt. This is a representation of how our planet travels through space around our sun. The moon that circles around our planet helps to stabilize this 23 degrees that helps protect our planet and make life, as we know it, possible. This 23 degree tilt is the major contributor to why we experience seasons. If you are like me you may need to pull out a globe (or ball of some sort) and walk it around a light source to imagine how this works. This 23 degree tilt causes the northern hemisphere to be partly pointed away from the sun at one particular position in its orbit and, at this same place in the orbit, the southern hemisphere is pointed more directly at the sun. This particular point in our orbit would be approximately December 21 of each year when the northern hemisphere experiences winter and the southern hemisphere experiences summer. So, while some of us celebrate Christmas in a winter wonderland, our Australian cousins are shouting, "fire up the barbie!" and having beach parties for Christmas fun. This variation of how directly or indirectly the sun's rays hit the earth also results in variation in the heating and cooling of various places on the earth. With a greater tilt, larger portions of the planet would be perpetually frozen, while others would be too hot to sustain life. With no tilt there would be no seasons and no summer or winter. Temperatures would be more like a perpetual spring.
Of course there could have been other ways to create a planet on which life might have been possible. Science fiction writers have often tried to imagine other worlds with dramatically different conditions. Poul Anderson in an epic short-story entitled, "Call Me Joe,"1 writes of a being named Joe who lives on Jupiter where the temperatures are cold enough, and the air is dense enough, for methane to exist as liquid. In this story Joe is able to live on the surface of this world, filling his lungs with this hyper-pressured atmosphere, survive the cold and drink methane like we drink water. Anderson imagines a world in which you and I could never survive; but one which is perfectly suited to Joe. Yet, even in this scenario the author imagines a degree of stability to this environment. Things like, the orbit of the planet, and physical principles of the universe in which Joe lives, and the temperatures at which he thrives remain relatively constant. So the point is not so much that our planet is the only planet on which life might thrive but rather that in order for life to develop and continue to exist on any given planet there must be some degree of stability and protection for that particular life to exist.
We could go on much further speaking of the various ways in which God has placed us in a protected corner of the universe surrounded by a number of properties that make life as we know it possible. Thus, we can recognize the large body of data that suggests that God is already protecting and sustaining us in an abundance of ways.
These various protections that make it possible to live on the planet earth are often spoken of in a different context. They are often used to describe the improbability that human-kind could ever come to be without the direct intervention and sustaining influence of a Creator. That is another important conversation. But, here, in a context in which we make the assumption that a creator God has indeed created this world in this way, we can also see these facets of the universe in which we live as examples of God's constant protection and sustaining activity.
1 Bova, Ben, ed. The Science Fiction Hall of Fame. Vol.
Two A. New York: Tom Doherty Associates, LLC, 1973, p. 1-33.