What makes Earth so gosh darn livable? How is it different from the other planets in our solar system, or viewable planets in our galaxy?

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What makes Earth so gosh darn livable? How is it different from the other planets in our solar system, or viewable planets in our galaxy?

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Anonymous 0 Comments

Earth was not made to be livable. Life was made to survive on Earth.

It’s like asking why a cup is the perfect shape to hold water. The cup isn’t the key. The water is molding itself to the cup.

Anonymous 0 Comments

The distance from the sun, which we call the Goldilocks zone. Far enough to not get baked into barren-ness like Mercury, and close enough to not freeze up like Neptune or Uranus.

The presence of water and absence of high concentrations of more “hazardous” components, like Venus’ runaway greenhouse effect and sulfuric acid clouds.

Anonymous 0 Comments

We have lots of things. With all of the billions of stars I’m sure life exists other places but life as we know it is limited to our situation.

We are located in a good orbit around the sun. It’s not to hot and bot to cold.

We have liquid water. Something we believe is required for life, carbon is also required.

We have a liquid core and an atmosphere. These protect us from radation.

We are a good size and density. Gravity isnt to harsh that it would crush us. It’s not so low we would float away.

Anonymous 0 Comments

Water. We have water, which is incredibly valuable to life, due to how common it is and how good it is at causing reactions.

Temperature. The temperature allows many complex molecules to form, *as well as water*.

Radiation. We’re not too irradiated, but our planet does get a fair amount of energy from the sun.

Anonymous 0 Comments

Earth has a combination of factors that made life much more likely to form here, vs anywhere else we know of.

First off, Earth’s orbit is at just the right distance from the sun to allow liquid water. Too close, and the oceans would boil. Too far, and they freeze. The region in between is called the habitable zone.

Having liquid water is important because it is a near-perfect environment for a lot of chemistry, *especially* organic chemistry.

Secondly, the sun itself is actually pretty important. It’s fairly calm as stars go, and will live quite a while. Stars that are much smaller or much bigger each have different problems.

Red and Orange Dwarfs, which are smaller than our sun, will sometimes flare violently. This can increase their brightness by as much as *eight* times! Imagine if the sun regularly became eight times brighter in the sky.

White and Blue stars, which are bigger than our sun, are much shorter lived. This likely doesn’t give any planets orbiting those stars enough time to develop complex life. Around the largest, shortest lived stars, planets won’t get enough time for *any* life, or even prebiotic chemistry.

Thirdly, Earth has a pretty strong magnetic field. This is important because, while our sun may be calm for a star, it still puts out ridiculous amounts of energy. This is mostly light, but there’s also a constant barrage of charged particles from the sun’s atmosphere. This is called solar wind, and over millions of years it will slowly blast away a planet’s atmosphere (and oceans if it has them). Fortunately, Earth’s magnetic field deflects most of the solar wind, protecting our atmosphere and oceans.

Anonymous 0 Comments

There are a number of factors like the presence of water and being the right distance from the sun so that the water is actually mostly liquid, but those factors don’t tell the whole story.

Venus for example is almost Earth’s twin and technically in same “Goldilocks” range as Earth where it is not too close and not too far away from the sun and it really is not habitable for life as we know.

Meanwhile places like Jupiters moon Europa are far outside the zone, but still thought to have oceans of liquid ice under its surface.

Places like Mars are thought to have been much more like Earth in the distant past.

On the other hand our own planet Earth has in the distant past been completely hostile to our type of life. Being at points completely frozen over and having started out with an atmosphere toxic to us.

It might be argue that Earth today is so suitable to our own form of life because it evolved here.

Life as we know it depends on liquid water because our type of life started out in liquid water. It depends on a certain range of temperatures and the presence of certain chemicals because that is what we have to work with.

Life is so well adapted to the condition on this planet because this is where it evolved.

Life also shaped how the planet itself is, keeping it at the right temperature and keeping the atmosphere as it is. We basically “terrafromed” the planet by existing on it.

Life on other worlds may or may not thrive under completely different conditions.

We don’t know what range conditions life may evolve and exist under.

We only really have a single example of life to work with.

The only clues we have to work with are our own planet, the few other worlds we have checked and found empty and the notion that intelligent life must be extremely rare for us to not see the signs of any other civilizations out there.

We have only so little data available.

It doesn’t help that planets like Earth are rather harder to detect from a distance than others, We can see bigger planets and planets close to their sun easier.

A planet that is about the size of Earth and about the right distance from a sun like our own, is much harder to see. So mostly we have found planets that are not much like our own.

Maybe planets like Earth are extremely common out there. Maybe they are rare.

Maybe Earth like planets are all teeming with life. Maybe they are all barren.

Maybe life is common on planets completely unlike our own and we are a fluke. Maybe life is common on all sorts of planets. Maybe life is extremely rare. Maybe we are on the only place with life at all in this galaxy.

We need to do gather more data to check.

Since we can’t even know what forms life may possibly take and how to check for it, we are mostly looking for life like ours on places like ours.

Anonymous 0 Comments

This is a pretty huge example of selection bias. Earth is livable *for us* because evolved here, so of course it is. That’s kind of like asking why you like your house so much after you bought that house specifically because you like it. Livable is only meaningful if you consider who lives there. The deep oceans are unlivable for humans for other sea life thrives there.

Earth is unique in our solar system but that’s not really representative of anything. There are between 200 and 400 *billion* stars in our galaxy. We’ve surveyed an infinitesimal fraction of a percent of them, and we’re already finding Earth-like planets all over the place. Galactically speaking, there’s really nothing special about Earth. Statistically ,there are at least 300 million Earth-like planets in our galaxy, and probably many more than that.

Anonymous 0 Comments

Because this is the planet we evolved to live on

if we evolved on another planet Earth wouldn’t be so gosh darn livable.

Its survivor bias or something

Anonymous 0 Comments

A couple of things that have not been mentioned: the moon. While planets having moons is common, the size of our moon is NOT common. At about 1/4 of the size of earth, it has the largest ratio of size to its planet than any other moon in the solar system. It is theorized that the moon is likely the result of a collision between earth and a mar sized proto-planet they call Theia. The collision added mass to Earth and the remains formed into the moon. This explains why Earth’s core is also very large for its size. Theia also may be the source of a most of Earth’s water (when Earth initially formed around the sun it probably didn’t come with much water).

The moon (and its origins) are important to life on Earth because

* its origins led to Earth’s large core which is vital for generating the magnetic field that protects the earth from solar wind which would destroy life
* its origins brought water to earth, essential for life
* the moon moderates Earth’s wobble on its axis, leading to a stable climate
* the moon causes tides, affecting ocean currents and climate
* the moon impacts tectonic plate activity, without the moon there would probably be less tectonic activity
* And more…

Another cool thing we take for granted: as children we look at the Sun and the Moon and think they are the same size because they appear the same size in the sky. We learn later than actually the Sun is much much larger, but further away, and the moon is much smaller but closer. IT JUST SO HAPPENS that the sun is about 400 times as wide as the moon, but also 400 times further away. Therefore the two look the same size in the sky, which is completely unique in our solar system. Although we do not know the odds of this happening in our galaxy, this seems like a very unusual coincidence. Because of the sizes and distances of the Sun and the Moon we are able to experience solar eclipses.

This was important for science in a really interesting way. in 1905 and 1915 Einstein published his theories of relativity and they were met with skepticism. But on May 29, 1919 Sir Arthur Eddington used two solar eclipses to prove Einstein’s general theory of relativity as correct. Direct evidence of “space-time” didn’t come until 2015 with the detection of gravitational waves.