Are we alone? Might Earth be the single exception to an otherwise dead universe? We should not be. The ingredients for life are everywhere – life should be common. But, then again, where’s everyone?
This article describes the 3 possible answers to this question. By the time you finish reading, you will have a solid grasp of the relevant science, enough to form an opinion on which answer is probably correct.
Requirements of Life To arise, life needs 3 things: Time, Energy, and Matter.
All may be found wherever there are actually stars. Each star is similar to a scratch-off lottery ticket – a chance to win by getting the right combination. The prize: the universe gains a new planet full of life.
The chance a ticket pays off remains unknown, but science has made progress in estimating the odds.
Because of the large number of tickets (there are actually 102210
Twenty-two stars in the observable universe), the chances appear to be good that more than one has paid off.
Let us review the exact requirements life has for matter, time and energy.
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The matter is actually the stuff life is actually made of, the building blocks. These are the chemical elements – hydrogen, nitrogen, carbon, oxygen, and so on. These elements are present everywhere. They are created as byproducts of fusion – the ash of nuclear fires which burn in every star.
The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, and the carbon in the apple pies of ours have been made in the interiors of collapsing stars. So we’re made of star-stuff.
Nitrogen, carbon, oxygen, and hydrogen make up more than ninety-nine % of the atoms in the health of ours. The others are actually needed only in trace amounts. Yet, these same 4 elements that compose the bulk of our bodies are also the most common chemically active elements in the solar system.
The same physics and chemistry that operate here apply everywhere in the universe. The common elements on Earth are actually found in every star and galaxy we see. This’s much more than conjecture. By analyzing light, astronomers can determine the chemical composition of faraway stars, nebulae, and galaxies.
Complex organic (carbon-containing) molecules, the precursors to life, including amino acids, have been detected in distant star-forming gas clouds or perhaps stellar nurseries near the center of the galaxy.
So you’re made of the same stuff as stars, planets, comets, and gas clouds.
Because of the accessibility of these essential ingredients, the entire universe is actually filled with the matter required for life. But life still needs enough time and energy to evolve.
All life feeds on energy. Energy forestalls the natural tendency towards disorder. Any time order is actually created, like in growing a body; energy must be expended.
Plants obtain energy from store and sunlight it in chemical bonds. Likewise, animals get energy from plants by consuming them and breaking those bonds to release energy, or perhaps they eat other animals.
The energy which drives the whole food chain and powers all living things on Earth started in the center of the sun ours. The same fusion responsible for cooking the chemicals of life provides stars, and life, the energy.
Though all life needs energy, not every life form gets it from sunlight.
Europa, Jupiter’s moons, appears on the surface to be a frozen ball of ice. But scientists think that ten miles under the frozen surface of its lies an ocean with two times the liquid water of Earth’s oceans.
What provides the power to melt this particular ice? The tides!
Tidal friction creates heat that can melt the ice as well as provide energy for life. Ultimately this energy comes from the spinning of Jupiter. As Europa’s own tidal forces drag on Jupiter, Jupiter’s rotation slows, and its days become longer.
Probably The oldest known lifeforms used geothermal rather compared to solar energy. They got their energy from hydrothermal vents like the Lost City – undersea geysers powered by the heat of Earth’s interior.
The last requirement for life is actually time – time for life to arise and evolve.
After the development of Earth, it had taken a couple of 100 million years for life to show up. Several billion more were needed to evolve multicellular life. It took a total of 4.3 billion years to get to mammals and 4.5 billion to yield a tool-making civilization.
To progress through these stages required an environment that remains stable for long periods.
The larger stars exhaust their nuclear fuel and explode or perhaps collapse after millions of years. This time is too light to host planets with life that is complex. But in the demise theirs, they give hope to others. This is because the elements baked in their cores are actually what enables life in other star systems.
This explains why life couldn’t appear much earlier in the universe’s history: many generations of large stars had to form, die, live, and explode to spread their ash, the stuff of life, into interstellar space.
Smaller stars are necessary to tend to a life-bearing planet. They offer enough time for life to do its thing. The lifespan of a star depends on its mass. The smaller the size of its, the longer it lives. Medium-sized stars like our sun last for billions of years. Smaller stars, like white dwarfs, can live for trillions.
Time is actually one thing the universe isn’t in short supply of. But life also needs stability.
For a planet to nurture life, it must provide stability. It requires a stable orbit along with a host star with a regular brightness. The planet must also stay away from potentially life-ending calamities – asteroid impacts, supervolcanoes, and gamma-ray bursts.
Earth has had the own share of her catastrophes. The Moon is actually believed to have formed when Earth collided with a Mars-sized planet called Theia. It is also thought that the whole surface area of Earth was covered in ice at one time.
Despite these and many asteroid impacts and supervolcanoes, when it got started, life has kept on.
As an indication of the severe conditions life might tolerate on other planets, biologists on Earth have taken a particular interest in extremophiles – creatures that can survive under extreme conditions.
The Bacillus bacteria have survived temperatures of 420°C (788 °F) and have been revived from a dormant state after 10,000 years. One report even claims to have revived it after being locked in a piece of amber for twenty-five million years.
Probably the most resilient species on Earth is actually the Tardigrade, also referred to as water bears. They are approximately one mm long and are like tiny 8 legged hippos. They may be found nearly anywhere.
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