Our sun emits light that our planet uses for energy to sustain life, but if our planet wasn't here the sun would still be emitting energy. It is not its purpose to sustain life on Earth. Just a byproduct of what it'd be doing anyway.

intersting, so you dont think there is a purpose for the energy emitted? cause and effect does explain why we have life, but it doesnt explain the phenomena of life. like animals have lungs, isnt the purpose of a lung to breath?

the manner in which things evolve doesnt require purpose. The whole process is causal and chance plays a large role, too. Lungs probably developed from gills of animals who happened to breathe air a little bit through their skin or mucosa. A selective pressure drove the gills to develop into more and more efficient oxygen filters. Selective pressure is the cause, and lung development is the effect.

This post was edited by Neptunus on Jan 3 2013 09:42am

What would that purpose be? As others have pointed out, purpose is a human concept. You might be temped to say that the sun's purpose is to provide us with energy, but that is problematic on many levels.

ok im just saying you guys are using the term ambiguously. lungs do serve a purpose, everything serves a purpose. but i see hwat you are saying about it being a human concept. everything else just exists, only humans struggle to find a reasoning of life. i wonder if any animals are philosophers

This post was edited by OrionGG on Jan 3 2013 05:15pm

Maybe this is just a semantics thing, but for me the word purpose implies an intent. There is a large chunk of iron sitting on the floor in my front hallway. This chunk of iron has a well defined shape, mass, electric charge, and many other properties. These properties can be described using numbers (math). These properties are independent of humanity. Kill everyone off and the chunk still has the same mass.

The reason/purpose it is there is because I like to use it to prop the door open sometimes. Without me, it has no purpose.

This post was edited by Azrad on Jan 3 2013 08:28pm

I don't know, I didn't create it.

Il

Yeah that still doesn't quite cover it but it is a semantics issue. I see what you are saying I just think nature does serve a purpose. Look at the way an ecosystem stabilizes and provides for itself. With or without humans, by definition nature does serve purpose.

Lungs developed over time in order to absorb oxygen into the blood. There were other, less-complex methods of incorporating oxygen into animals' bodies, but evolution favors things which give distinct competitive advantages, and being able to absorb more oxygen from the air (due to greatly increased surface area contact with the atmosphere) means you can run farther and faster than something with slower oxygen intake.

So while the purpose of the lung is to absorb oxygen in the same way that the purpose of wings are for flying (or swimming for some birds), it's not like it's the first and only method a lifeform ever used to obtain oxygen (e.g. gills).

I strongly recommend http://evolution.berkeley.edu/ as a resource if you have other questions about how various body parts came to be. It can give you the tools to understand the process of natural selection, and other sites on the internet actually can provide examples of where gradients on the way to a modern body part exist in current and past species (e.g. the eye first developed as a photo-sensitive patch on a microbial lifeform so it could detect/react to light, and then developed more complexity as time went on).

http://www.youtube.com/watch?v=W96AJ0ChboU <-- decent video on the concept of "irreducible complexity"