Community > Forum > The Spaceflight Cafe > The definition of life

The definition of life

Posted by: SuperShuki - Fri Oct 09, 2009 11:03 am
Post new topic Reply to topic
 [ 20 posts ] 
The definition of life 
Author Message
Space Station Commander
Space Station Commander
User avatar
Joined: Mon May 31, 2004 9:47 pm
Posts: 816
Location: Yerushalayim (Jerusalem) - capital of Israel!
Post Re: The definition of life   Posted on: Thu Oct 15, 2009 7:37 am
Lourens wrote:
I'd like to think of life as an opposing force to decay. Non-living things just are, and wither away over time. Living things keep repairing and recreating themselves. In more physical terms, perhaps we could say that something is alive if it comprises one or more processes that locally decrease entropy?


I like that definition. Now how do we define "something"?

_________________
“Once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return.”
-Anonymous


Back to top
Profile WWW
Space Station Member
Space Station Member
User avatar
Joined: Mon Nov 29, 2004 1:04 pm
Posts: 254
Location: Norway
Post Re: The definition of life   Posted on: Thu Oct 15, 2009 11:50 am
SuperShuki wrote:
I like that definition. Now how do we define "something"?


It's what occupies the space between nothing and everything


Back to top
Profile ICQ
Space Station Commander
Space Station Commander
User avatar
Joined: Mon May 31, 2004 9:47 pm
Posts: 816
Location: Yerushalayim (Jerusalem) - capital of Israel!
Post Re: The definition of life   Posted on: Thu Oct 15, 2009 7:19 pm
Lourens wrote:
I'd like to think of life as an opposing force to decay. Non-living things just are, and wither away over time. Living things keep repairing and recreating themselves. In more physical terms, perhaps we could say that something is alive if it comprises one or more processes that locally decrease entropy?

Perhaps I could enlarge on that definition. Life is the process of decreasing entropy. Entropy is movement towards chaos. Therefore life is the process of increasing order.
Order is separation. Now apply this idea to all areas of life . . .

_________________
“Once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return.”
-Anonymous


Back to top
Profile WWW
Space Station Commander
Space Station Commander
avatar
Joined: Thu Oct 27, 2005 7:44 am
Posts: 707
Location: Haarlem, The Netherlands
Post Re: The definition of life   Posted on: Thu Oct 22, 2009 8:03 pm
A thing (or object) is some subset of the universe that has a constant value for some property, and is surrounded by other subsets with different values for that property. I am a thing, because all of me has the property that it consists of cells containing my DNA, and none of the air, chair, floor, table and laptop that surround me have that property. A hole is a thing because it is an empty subset of the universe, surrounded by non-empty subsets.

I'm not sure that my definition of life is entirely correct yet though. Consider a computer that continuously sorts the numbers in its memory. That is a process that locally decreases entropy (of course the computer uses energy and produces heat, which makes total entropy increase, so it's not violating the laws of thermodynamics). Could we say that the computer is alive?

One could argue that at some point the numbers will have been sorted, and no further increase in entropy occurs, so that there is no continuous decrease in entropy. But then, every once in a while there will be a cosmic particle that flies through the memory chips and flips a bit, and the order will be off, and it will be fixed again.

Another, stronger argument would be that the computer hardware itself will still break down over time. So perhaps we could define a living thing as a thing that decreases (or keeps the same) entropy locally throughout all of itself? That would mean that my grandmother, with her prosthetic hip, isn't strictly alive, unless you consider her to end wherever the artificial joint begins, or unless she has the hip replaced whenever it wears out. That's not that unreasonable perhaps.

There's another question of whether alive or dead is really a binary thing, or that we should take the rate of entropy decrease into account and introduce an ordinal scale. In vegetation science there is the concept of vitality, which describes how well a plant is doing. During a dry period for example, your lawn will turn yellow, and we can say that its vitality gets worse. It's not quite as alive as when it was nice and green and wet. It works in animals too: old people aren't as vital as young ones, and indeed their cells divide more slowly and damage is repaired less quickly. Conversely, a tumour can then be said to be more alive than the surrounding tissue, so much so that it starves it of resources and threatens its continuous existance. Is a slow-growing oak less alive than a fast-growing poplar?

_________________
Say, can you feel the thunder in the air? Just like the moment ’fore it hits – then it’s everywhere
What is this spell we’re under, do you care? The might to rise above it is now within your sphere
Machinae Supremacy – Sid Icarus


Back to top
Profile
Space Station Commander
Space Station Commander
User avatar
Joined: Mon May 31, 2004 9:47 pm
Posts: 816
Location: Yerushalayim (Jerusalem) - capital of Israel!
Post Re: The definition of life   Posted on: Sat Oct 24, 2009 6:47 pm
I'd say that the process that the computer is engaged in is a life- positive process. However, the computer itself isn't actually doing the process. The computer is a tool, just the same as a hammer in your hand. Therefore the life process that the computer is engaged in is actually an extention of its maker's and operator's life.

_________________
“Once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return.”
-Anonymous


Back to top
Profile WWW
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 20 posts ] 
 

Who is online 

Users browsing this forum: No registered users and 12 guests


© 2014 The International Space Fellowship, developed by Gabitasoft Interactive. All Rights Reserved.  Privacy Policy | Terms of Use