Life has found a home on Earth for nearly 4 billion years. This is a significant part of the 13.77 billion year history of the universe. Presumably, if life arose here, it could arise anywhere. And for sufficiently broad definitions of life, it may even be possible for life to emerge within seconds of death. Big Bang.
To discover the origins of life, we must first define it. There are more than 200 published definitions of the term, which shows how difficult it is to get to grips with this concept. For example, are viruses alive? They reproduce, but they need a host to do so. What do you say prions, pathogenic protein structures? Debates continue over the line between life and non-life. But for our purposes we can use an extremely broad but very useful definition: Life is anything subject to Darwinian evolution.
This definition is useful because we will be exploring the origins of life, which by definition blurs the boundaries between life and non-life. At some point, deep in the past, Soil He was not alive. Then it was. This means that there is a transition period that will naturally push the boundaries of any definition you can make. We also want to keep our definition broad as we delve deeper into the past and explore other potential options for life, especially as we explore the more extreme and exotic corners of the world. Universe.
Relating to: Life may have evolved before Earth completed its formation
Considering this definition, it appears that life on Earth appeared at least 3.7 billion years ago. By then microscopic organisms had become sufficiently advanced to leave behind traces of their activities that persist to this day. These organisms were very similar to modern organisms: They used DNA to store information, RNA to translate that information into proteins, and proteins to interact with the environment and create copies of DNA. This three-way combination allows these groups of chemicals to experience Darwinian evolution.
But these microbes didn’t just fall from the sky; They evolved from something. And if life is something that evolves, then there must have been a simpler version of life that emerged even earlier in Earth’s past. Some theories suggest that the first self-replicating molecules, and thus the simplest possible form of life on Earth, may have emerged more than 4 billion years ago, when the oceans cooled.
And the Earth may not be alone – Anthem And Venus There were similar conditions at that time, so if life happened here, it might have happened there too.
The first life among the stars
But sun wasn’t the first star to catch fire fusion; It is the product of a long line of previous generations of stars. Life as we know it requires a few basic elements: hydrogen, oxygen, carbon, nitrogen and phosphorus. All of these elements, except hydrogen, which appeared in the first few minutes after the Big Bang, are created in the hearts of stars throughout their life cycles. That is, as long as you have at least one or two generations of living and dying stars, thus spreading their elements more widely galaxyYou can enable the emergence of Earth-like life in the universe.
This causes the possible first appearance of life to date back to 13 billion years ago. In this age history of the universe known as cosmic dawn, when the first stars were formed. Astronomers aren’t exactly sure when this transformative period occurred, but it was somewhere a few hundred million years after the Big Bang. As soon as these stars emerged, they may have begun to create the elements necessary for life.
So life as we know it, built on carbon chains, using oxygen to transport energy, and submerged in a bath of liquid water, may be much, much older than Earth. Even other life forms based on exotic biochemistry require a mixture of similar elements. For example, some alien life may use silicon instead of carbon as a basic building block or use methane instead of water as a solvent. Regardless, these elements have to come from somewhere, and that’s somewhere in the cores of stars. Without starsYou cannot have a chemical-based life.
The first life in the universe
But perhaps it is possible to live life without chemistry. It’s hard to imagine what these creatures might look like. But if we take our broad definition that life is anything that is subject to evolution, then we don’t need chemicals to make this happen. Of course, chemistry is a convenient way to store information, obtain energy, and interact with the environment, but there are other hypothetical ways as well.
For example, 95% of the energy content of the universe is unknown to physics, literally falling outside the known elements. Scientists aren’t sure what these mysterious components of the universe are. dark matter And dark energyhas been made.
Perhaps there are additional forces of nature that operate solely on dark matter and dark energy. Perhaps there is more than one “type” of dark matter;dark matter periodic tableWho knows what interactions and what dark chemistry are at play in the vast spaces between stars? Hypothetical “dark life” may have arisen extremely early in the universe, long before the first stars appeared, supported and mediated by forces exerted by us. I don’t understand yet.
Related Stories:
—Life as we know it may have its roots in an old, cold cosmic cloud
—Meteorites and volcanoes may have helped jumpstart life on Earth
—Scientists simulate possible origins of life in the laboratory
The possibilities could get even stranger. Some physicists have suggested that the forces of nature in the first moments of the Big Bang were so extreme and exotic that they could support the growth of complex structures. For example, these structures can be: cosmic versesare folds in space-time anchored by magnetic monopoles. With sufficient complexity, these structures may have stored information. There would be plenty of energy to go around, and these structures could self-replicate, making Darwinian evolution possible.
Any living creature existing in these conditions would live and die in the blink of an eye; Their entire history would last less than a second, but for them it would be a lifetime.