What Is Alive?

Life, the universe and everything is 42.
We try to define what life is and try to understand it better, but do these definitions really make sense?
So, without any further ado, turn on your imagination and lets go for a ride.

The Dictionary definition of alive: not dead, alert and active, animated.

The Dictionary definition of life: the condition that distinguishes animals and plants from inorganic matter.
Inorganic matter is something that is not carbon based(so not containing many carbon-hydrogen bonds).
So, according to this definition if its not carbon based its not alive. Substances like Gasoline(petrol) are primarily C-H bonds, so is petrol alive?
If gasoline is alive on the only premise of being carbon based then dead stuff is alive which is a contradiction.
Restricting life to carbond based sounds like a rather Earth centered definition. Why is life on Earth carbon based? Because things we classify as alive usually have DNA or RNA which are carbon based molecules that are mainly used for reproduction, and producing proteins.
What about noncarbon based life? Many people have pondered this question and Wikipedia has a nice summary of proposed ideas of what other based life might exist:https://en.wikipedia.org/wiki/Hypothetical_types_of_biochemistry
If you want go much more indepth I recommend to read a book called "Life As We Do Not Know It" by Peter Ward.

Is using water as a solvent part of being alive or is that also just an Earthling thing?
A solvent is a substance(usually liquid) that can dissolve other substances. So, aliens could easily use other liquids as their life solvent. This would also change properties of DNA(or RNA) and organelles in the cell because water is polar but if the life solvent is not polar other mechanisms would be used.

Current Scientific Definition of Life

1. Ordered/have one or more cells:
To have complexity.
2. Metabolism:
Is a chemical reaction to produce energy.
3. Homeostasis:
This is the ability to regulate chemicals, temperature, etc...
4. Growth:
Change over time.
5. Reproduce:
To make a copy(similar or identical) to ones self.
6. Response:
React to changes in the environment.
7. Evolution:
To adapt to the environment over generations.

Viruses

Viruses are not classified as alive because they can not reproduce themselves. They need to find a host to do it for them. They trick the host into copying their DNA or RNA to reproduce themselves.

• They grow
• and they evolve: viruses mutate and change over generations.
However,
• They do not have organelles for energy production, so they rely on the host to do metabolism for them.
• They also dont maintain homeostasis
• They dont really respond to their environment. They can identify if they are close enough to a host cell they can infect. But otherwise they dont actively react to stimuli.


• And they are made of cells? Well their cells are not classified as cells because they dont have a reproduction nor a metabolizing mechanism. They are a protective protein coated shell containing either RNA or DNA. Cells are the smallest unit of something that can live on its own. Thats a circular definition lol. But according to that viruses are not cells since they can not live on their own.

Fire Is Alive

1. Ordered/has cells:
Each flame is a cell.
2. Metabolism:
Like us humans, fire converts O₂ and food into CO₂ water and energy.
3. Homeostasis:
Fire regulates, once ignited it produces enough heat to keep burning. And if not given more food it will go into hibernation and only glow, trying to stay alive in the hope that it will find more food soon.
4. Growth:
A small flame can get bigger and higher if given more food and oxygen.
5. Reproduce
Fire typically starts of as one flame, but can than multiply creating more flames.
6. Response:
Fire reacts to its surroundings. If there is not much food it will go into hibernation and just glow. If there is a big supply of oxygen(because of wind for example) it will grow and reproduce a lot more.
7. Evolution:
Fire does not evolve. But it could be argued that it does not need to because it can easily be spawned. Also, because fire does not evolve it eventually dies out.

Rocks Evolve

They dont have metabolism but they do evolve. In different parts of the world there are different animals. For example, in Europe the squirrels are different from the ones in north America. With rocks it's the same thing. In different parts of the world there are different types of rocks. Like animals this is because of evolution. In places where water flows quickly soft rocks cant survive and get eroded. The environment shapes animals and forces them to adapt and same goes for rocks.

Who knows maybe rocks do have metabolism but just on a very long time period, so we humans dont notice.

Cars?

• Cars are made by humans(and robots) so they dont reproduce themselves.
• But a case could be made that they evolve(model T is very different from cars driving around today).
• They also metabolize(burn fuel or discharge a battery to produce energy)
• They regulate their engines temperature(homeostasis). Also, if the car has cruse control it does homeostasis by keeps speed constant.
• They change(age) over time by rusting. And Many modern cars get software updates(grow).
• They are complex(well they dont exactly have cells, but maybe it's a one celled organism?),
• If it is not a manual car but rather has automatic transmission then it responds to changes in speed and will shift gears accordingly. Not all but many cars automatically turn on their lights when it gets dark. Also, self driving cars are slowly becoming a thing, and they definitely respond to their environment.

If Aliens Visit Earth We Probably Would Not Notice

In both science and science fiction there are theories that life on Earth started somewhere else, like on Mars for example. And through a giant meteorite impacts or other phenomenon got ejected into outer space and eventually landed on Earth.

But even if aliens landed on Earth today, we would probably not notice. We discover new species every year. So, if aliens landed in the jungle or the ocean we would think they are an undiscovered species.

When scientists talk about looking for life on other planets and moons they are really looking for Earth like life. There might not be human like life in our universe(or maybe multiverse) but there is most likely other life that is potentially very different.

Who knows maybe dust devils are actually ninjago ninjas.

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