I hear my mother's voice echo in my head as I tell my own children to "go outside!" When I was growing up, I think these words were heard in most households. Unfortunately, my children are probably in the minority for hearing those words now.
In general, parents have a greater fear of the outdoors than in the past. The media has made child abductions seem common place and outdoor accidents often make overblown news stories. Plus, we are another generation or two removed form agriculturally life and connection to the outdoors.The good news is that these dangers are only perceived. The risk of child abduction is no greater now than it was in the 1970s or 1980s. What is the greatest cause of childhood fatalities? Riding in automobiles. Are people going to stop driving their kids around? Children probably spend more time in cars now than ever before. What causes the most accidents at home? Falling down stairs. So, obviously it is in our children's best interest to get them outside - AWAY from those dangerous stairs!
Playing outdoors allows children to be adventurous, to practice the scientific method, to learn hands-on about living things. In a more philosophical and theological sense, time spent outside, allows children to connect to nature and God's creation. They can see it as an integral part of who we are as humans. they have a greater understanding of how we fit as part of creation. The more we see ourselves as part of this planet, the better we will care for the other parts of the planet - and that can only make this a better and safer place to live.