Mars Announcement Raises Question: What Is Life?
2013 03 18

From: SPACE

NASA officials announced March 12 that ancient Mars could have supported primitive life. But this begs the question: What exactly constitutes life?

Merriam-Webster.com defines life as "an organismic state characterized by capacity for metabolism, growth, reaction to stimuli and reproduction." But there’s no single satisfactory definition of life.

"I think it is a mistake to try to define life, because we have only one example of life, familiar life on Earth, and we have reason to believe that this example may be unrepresentative of life in general," Carol Cleland, a philosopher of science at the University of Colorado, Boulder, told LiveScience in an email.

Defining life

Aristotle made the first attempt at a definition, describing life as something that grows, maintains itself and reproduces. But this definition would exclude mules, which are sterile, while including things like fire.

Calling life something that has a metabolism, the ability to take in energy to grow or move and excrete waste, is no good either; cars do this, for example.

In 1944, the physicist Erwin Schrödinger gave life a definition based on the second law of thermodynamics, which states that the entropy, or disorder, of a closed system increases over time. Schrödinger defined life as something that decreases or maintains its entropy. Yet this definition fails because it includes crystals, which resist entropy by forming highly structured lattices.

Trying to define life by its qualities is the wrong approach, Cleland said. As an example, she cites scientists’ early attempts to define water in terms of properties like being wet, transparent and a good solvent. "We didn’t ’define’ water as H2O, but rather discovered, in the context of molecular theory, that it is a chemical substance composed mostly of H2O molecules," Cleland said.

Life on Earth is typically divided into two main groups: the cellular life forms, which include archaea, bacteria and eukarya (all the plants and animals), and non-cellular life forms, like viruses. Whether viruses, which can replicate only inside the cells of a host organism, count as "life" is debated.

[...]

Read the full article at: space.com



Related Articles


Latest News from our Front Page

US Silent on Psychologists Role in CIA’s Tortures: Doctors
2014-12-20 21:53
Physicians for Human Rights had not received any response from the US Federal Commission to their call to investigate the role of health professionals in CIA’s torture program, Deputy Director of the organization told Sputnik. December 19 (Sputnik) — US government has not responded to calls to prosecute doctors, who participated in CIA torture program, the Deputy Director of Communications for ...
Ziolebrities: Simon Cowell donates £100,000 to Israeli soldiers to please pregnant jewish girlfriend Lauren Silverman
2014-12-20 21:00
Cowell, 54, is also planning a secret trip to Israel soon as he embraces the Jewish faith of Silverman, 36 Gala: Billionaire Haim Saban with Cowell Simon Cowell has publicly donated nearly £100,000 in support of the Israeli army. The X Factor boss pledged the cash to the Friends of the Israel Defense Forces at a US fund-raiser in Beverly Hills. The lavish gala ...
Former Chief Security Officer for NewsCorp: N. Koreans Not Behind Sony Hack, Interview Leak
2014-12-20 2:17
Hemanshu Nigam, a former federal prosecutor and former chief security officer for NewsCorp/Fox studios, says North Korea isn’t behind the Sony Hack. Nigam gave several bullet points for why the hack was likely an inside job. Attack code borrowed from a previous attack on Seoul, that’s why it’s in Korean. Private hackers typically borrow malicious code from other hackers.Nations state attacks follow ...
Sony Fires Back at Obama: Actually We Did Call the White House – Several Times
2014-12-20 2:13
Sony fired back at Obama after the press conference saying they had several conversations with the Obama White House before and after the movie was canceled. Via The Hollywood Reporter: After President Obama criticized Sony for its decision to cancel The Interview's release after theater chains decided not to show the film, the studio has issued a statement elaborating on the move. “The ...
The Bankster International
2014-12-20 1:55
Geopolitical analysis, the art of explaining power relationships through the prism of impersonal geography, can be a helpful tool for observers of the Great Game – but it also has its limitations. A case in point is the renewed US-Russia confrontation. Think tanks and policy insiders easily sell the narrative that from the dark days of the Cold War to ...
More News »