A closed system is one in which no energy (or mass) is going into or out of it.
The only truly closed system is the Universe (since energy cannot be created or destroyed). All other systems are open.
The concept of a closed system is a computational convention used by scientists and engineers to analyze the thermodynamics and energy transfer of certain devices or instances.
For example you may want to figure out how long it will take your freezer to freeze a room temperature, one pound piece of ribeye steak to 30 degrees F if the freezer is set at 20 degrees F. Simple enough, you figure out how much heat energy is in the meat frozen, subtract that from the amount of heat energy in the meat at room temp and that is the amount of energy that must be removed from the meat to freeze it. Then figure out how quickly that heat can be transfered from the meat to the freezer and voila (tried to make this as simple as possible). Now, back to closed systems.
Closed systems are analytical tools. They are boxes of dotted lines drawn on a piece of paper around any part of this system I choose to analyze. But there is no such thing as a closed system (except for the Universe as a whole) so I must always remember – THIS IS IMPORTANT – to draw an arrow going into the box (system) representing the energy that is supplied to the system and an arrow going out of the box (system) representing the energy which is removed from the system:
– I may be a meat man interested in the properties of meat and choose just to analyze just the meat, draw a box around the meat.
– I may be a refrigeration engineer and I want to know what kind of refrigerant to use. Draw a box around the whole refrigerator, arrow in for electricity supplied – arrow out for heat removed.
– I may be an architect and want to know how much AC I am going to have to supply to keep the room cool. Draw a box around the room, arrow out represents how much heat is put out by the refrigerator into the room, this equals the amount of heat that my AC unit must remove from the room – arrow in representing electricity used by AC unit.
– I may be a power plant engineer trying to decide how much energy must be supplied to a whole town of people trying to freeze their meat and live. Draw a box around the whole town. Arrow out is how much energy they all use which is how much energy I must supply – arrow in.
This can go on and on. We have meteorologists studying the earth as a whole. They can draw a box around the earth for analytical purposes but they must always remember to account for the energy coming in from the sun and the earth itself – arrows in, and energy lost to space – arrow out.
I hope I haven’t lost everybody because this is the REALLY IMPORTANT PART when refuting religionists who make claims such as this. They use the science of Thermodynamics to back up their claim for the existence of God or to refute evolution but they always forget the arrow in and the arrow out. Religionists label all systems they want to refute as closed when in reality there are no closed systems except the universe as a whole.
The author makes a completely arbitrary claim that all the hydrogen should have been used up by now. Why? Because he says the Universe has been around forever? Current estimates are that the Universe is between 10 and 15 billion years old. The fact that the universe is a closed system doesn’t help his case. Indeed the energy in the universe has become more dispersed as the second law of thermodynamics suggests. The same amount of energy exists now as 10 billion years ago (energy cannot be created or destroyed) but the universe is bigger, thus the energy is more dispersed. But these facts don’t prevent gravity from working to pull hydrogen together, creating a star, which is concentrated energy that itself is dispersing. Yes daniel, gravity is one of the forces that tends to concentrate energy and mass (which is really just concentrated energy).
Religionists use a different phrasing of the second law, that closed systems tend from a state of more order to less order, to refute evolution. They say "in the closed system of the earth how could life have evolve from a less ordered state like single celled organisms to the more ordered state of cell colonies much less into human beings. But the earth is not a closed system. Evolution is not a closed system. And organisms are not closed systems. How long would one of us survive if we were put in an air tight box even resembling a closed system? Not long.
The site poohat linked talk origins is an excellent source for all things scientific, especially as they relate to refuting religionists.