We live on a tiny green planet with a single moon orbiting a yellow star with a few less welcoming stones nearby and even less welcoming gaseous balls a little further away, which are named after all kinds of mythical deities. As we explore more and more distant regions of space, we are hopelessly trying to find other star systems that could contain pleasant worlds to live in. By appreciating these attempts and realizing how lucky we are to live in our system, we, in the meantime, can explore other possible and crazy scenarios about how different our solar system could be. Note to modern directors. What…
… if Mars hadn't lost its magnetic field
Mars once had a promising atmosphere when it was warm, humid and full of carbon dioxide. It disappeared when the Red Planet lost its magnetic field about 3.6 billion years ago, allowing the Sun to blow away the atmosphere with the solar wind with impunity. By cosmic standards, this happened quite quickly - most of the atmosphere disappeared in a couple of hundred million years after the magnetic field was turned off. Today, Mars' atmosphere makes up roughly 1% of the earth's atmosphere at sea level, and solar winds continue to devour it at a rate of about 100 grams per second.
We know that this planet once had a magnetic field, because magnetized rocks still exist on its surface. Some believe that the magnetic field was lost due to heavy bombardment by asteroids, which disrupted the heat flow inside Mars that generates the magnetic field. If this had not happened, Mars would have retained its primitive oceans and, perhaps, would have been another source of life in our solar system.
Another theory suggests that the old magnetic field could only cover half of the planet, thus calling into question its long-term viability. Understanding the composition of Mars' inner core will help answer this question. On Earth, liquid iron flows around a hotter, harder core that holds our protective magnetic field in place. If Mars only had a molten core, that could explain the loss.
… if the Earth did not have the Moon
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It is believed that about 4.5 billion years ago, a planetary embryo the size of Mars (called Theia) crashed into Earth, ejecting enough material from it to form our moon. The tidal effects of the Moon could have influenced early volcanism and increased the number of meteorites falling to obliterate early life. However, some believe that life first appeared at deep-sea hydrothermal vents in a process that could be positively influenced by tidal currents.
Rapid lunar tides, when the Moon was closer to Earth, could create shallow salty seas, in which fragments of protonucleic acids bind at weak flows and decay at strong ones, ultimately leading to the formation of DNA. According to paleobiologist Bruce Lieberman, “eventually, life could have formed without tides. But the lineage that led to the emergence of man is rooted precisely in the tides."
It is likely that tidal currents aided the transport of heat from the equator to the poles, implying that ice ages would be less severe without the moon and reduce evolutionary pressures on life. If life evolved on Earth without the Moon, it would probably go through fewer changes over time and come to less variety. The length of the day would also be different without the Moon, which helped slow the Earth's rotation from six to twenty-four hours, and also stabilized the Earth's tilt and therefore the seasons. Any life developing on a moonless world would experience extremely short days and nights and probably more severe climatic shifts.
In the absence of the moon, lifeforms would lose moonlight, which helps them stay active at night, affects nocturnal predators, and encourages the development of night vision. The cultural life of any sentient species would remain without the influence of the moon.
… if the Earth had rings
After colliding with the unstable planet Theia, the Earth briefly acquired rings, which eventually merged into the Moon. This happened because the debris lay outside the Roche limit, where gravitational forces tear apart any nascent natural satellite. If a small moon or satellite were too close to the Earth's gravitational pull, it would burst with the subsequent formation of a permanent ring.
Saturn has rings of ice that would hardly last long if they were as close to the Sun as we are, but theoretically rings of stone could survive, although they would be different from the rings of Saturn. The effect would be obvious, as the shadows cast by the rings would lead to cold winters and decreased sunlight in both hemispheres. If intelligent life was formed under such conditions, the rings would interfere with the development of ground-based optical astronomy. They would also significantly complicate space travel and satellites due to space debris.
Such rings would look different depending on the region of the Earth from which they were viewed - a thin line in the sky over Peru, a powerful arc in the half-sky in Guatemala, a 180-degree atmospheric clock in Polynesia, and the ubiquitous glow on the horizon in Alaska. One can only speculate about how the ancient peoples of the world would have incorporated these amazing species into their mythology and cosmology.
… if Jupiter were a star
The largest planet in the solar system, according to some, should have become a star, a brown dwarf, but it lacked a little mass. (Others think Jupiter needed to be thirteen times larger to do this.) Had Jupiter become a star, it would be dim and distant, a little brighter than Venus. Such a star would not generate enough light or heat and would be five times farther from the Earth than the Sun, so it would (fortunately) not affect the development of life on Earth.
Turning Jupiter into a star is not so easy, more difficult than just setting the planet on fire. Since Jupiter is made up mostly of hydrogen, to ignite it, you will have to cover it with oxygen half the volume of Jupiter: the result is water. But we need a star, not a big burner. To start fusion like the sun, more hydrogen is needed. It would take another 13 Jupiters for a brown dwarf, 79 for a red dwarf, and 1,000 times more Jupiters for a sun-sized star.
However, simulations have shown that increasing the size of Jupiter to the size of the sun will cause chaos in the solar system. The satellites of the outer planets will fly out of orbits in different directions, and the asteroid belt will be completely destroyed. And while Mercury and Venus will remain nearly intact, the Earth will eventually crash into another planet or orbit closer to the Sun.
… if the Earth rotated the other way
The most obvious effect of the Earth's reverse rotation would be the Sun rising in the west and setting in the east, but that's not all. According to the University of Pennsylvania astrophysicist Kevin Luman, “The Earth rotates this way because it was so born. When the Sun was a newborn star, there was a whole bunch of gas and dust around it, spinning in a large disc-shaped structure. The only planet that rotates in the opposite direction is Venus, and this was most likely due to a collision billions of years ago. Repetition of such a process with the Earth will probably exclude any observers for long summers.
Even if this happens at the behest of magic or aliens, the consequences will be very serious. The Coriolis effect, which determines how the Earth's rotation is transmitted to wind behavior, will be completely reversed. The trade winds will be facing the other way, which will lead to climate change in many regions. This will especially affect Europe, when the warm winds blowing across the Atlantic from the Gulf of Mexico are replaced by the Siberian cold blowing from the east.
In other places on the Earth, a change in rotation may have a more favorable effect. In North Africa, precipitation will increase, and the amount of river water entering the Mediterranean Sea will practically turn it into a freshwater lake. Warm air will be sent to the North Pacific and South Atlantic, making Alaska, Far Eastern Russia and parts of Antarctica more attractive for life.
… if we switched places with Mars
If Earth and Mars are rearranged, the effects will be quite interesting: Martian temperatures will rise, the polar caps will melt, gases will be released from the soil, and the climate will become almost as warm as it is now on Earth. The earth, on the other hand, will get much colder. More problems will result from the destabilization of the inner solar system due to the effect that the orbits of the planets have on each other.
Planetary physicist Renu Malhotra of the University of Arizona conducted simulations that showed severe destabilization of planetary orbits. She tried to ignore the results of Mercury, but everything led to the fact that Mars would be ejected from the solar system. Other simulations have shown that Earth and Mars will acquire unstable orbits due to the influence of Jupiter. This suggests that the orbital situation of the inner solar system is rather unstable, which calls into question the proposals of some futurists to move Mars closer to the Sun.
Remarkably, if such an orbital mechanics worked, the Earth would perfectly swap places with Venus. The study showed that the Earth, or a terrestrial planet, could potentially be habitable in the orbit of Venus, whose position is usually estimated to be slightly closer to the Sun than is necessary for life. Despite the doubled solar radiation, the cloud cover would keep the surface temperature within acceptable limits.
… if we lived in the center or at the edge of the galaxy
We seem to live in a rather boring sector of the Milky Way, far from the hustle and bustle of the galactic center. If we were in the center of the galaxy, the night sky would be much brighter, with a bunch of bright (like Venus) stars, because the stars in the core are separated by several light weeks, not years. The density of stars near the center is 10 million stars per cubic parsec, up from 0.2 in our faint segment. There are also many supernovae and a supermassive black hole nearby, but what can you do, city life is like that.
Meanwhile, if we were closer to the edge of the Milky Way, hardly anything would have changed if life had arisen at all. Star systems at the edge of galaxies have a lower level of metallicity, that is, they have fewer elements heavier than hydrogen and helium. Decreasing levels of metallic elements mean that gas giants like Jupiter, which are slowly gathering around solid cores, will appear less. Since the gas giants will not take the hit, solid worlds will be more vulnerable to comet impact. In addition, the Earth's night sky at the edge of the galaxy will be dull and empty.
Living in the suburbs can have positive aspects as well. Some believe that the conditions for life fit into a series of key conditions that are met only in a relatively narrow range known as the galactic habitable zone. In 2001, Guillermo Gonzalez stated that frequent supernovae and high levels of radiation inherent in the galactic center are preventing the emergence of life. Recent studies say this argument is rather skeptical, as frequent supernova sterilizations would be counterbalanced by the greater chances of life evolving.
… if there were two suns
In 2011, astronomers observed the first known planet in a binary star system, also known as a multiple-orbiting planet, called Kepler-16b. Alan Boss, astrophysicists at the Carnegie Institute of Science, was asked what the Earth would look like under such conditions. He said: “Slightly coldish. Although it is closer to its stars than Earth is to its own, these stars are not so bright, so the temperature on the planet will be only -73 degrees Celsius. If we replace our Sun with these stars, we would be even colder, since we are further from the Sun than this Tatooine."
Of course, not all binary systems are the same, and some situations are better suited for the development of life. Research presented at the 223rd meeting of the American Astronomical Society in 2014 showed that some binary star systems may be more favorable for the development of life than unitary stellar systems. Paired stars, whose rotation has been synchronized, will reduce each other's solar radiation and stellar winds, which often clear the atmospheres of planets and moons.
A study by astrophysicist Paul Mason has shown that stars orbiting each other in 10-60 Earth days will exert tidal forces that reduce rotation and reduce stellar winds, which could potentially expand the range of potentially habitable zones in the system by combining light from two stars instead of one. Mason admitted that having two suns, Venus could conserve its water, and the Earth would be a more humid world.
… if the sun disappeared
Despite the fears of the ancients, the Sun is not going to suddenly go out, and such a scenario is physically impossible, as far as we know. But if that happened, the Earth would not freeze instantly. If we stay in orbit of the cooled and dead butt of a once beloved star, temperatures will drop below -17 degrees Celsius in a week, and to -73 degrees in a year. Without photosynthesis, plant life will quickly fade, as will all other life as the oceans freeze.
The upper layers of ice will isolate deep waters and prevent the oceans from freezing for hundreds of thousands of years, so some oceanic and geothermal life forms can survive. Creepy, but the trees will stand for several more decades, thanks to their slow metabolism and sugar stores. The best places for human survival would be nuclear submarines or perhaps dwellings built in geothermal-rich countries like Iceland.
Apart from death from cold, there are still some advantages to living in a world without the Sun. The risk of solar flares will be reduced, satellite communications and conditions for astronomers will be improved.
But in general, of course, it would be better with the Sun. Even if you remove the Sun for just a second, without the gravity of the Sun, all objects in the solar system, instead of a circular orbit, will go in a straight line. A second later, when the Sun returns, everything from gas giants to cosmic dust will be in new orbits, some of which will be unstable. Also, for a second, the heliosphere, which protects the solar system from extrasolar radiation, will disappear. A second without shields will allow vile radiation from the outside to penetrate, which will lead to the appearance of auroras around the world, disrupt satellites and power grids, or possibly sterilize the Earth.
… if the Earth meets a black hole
Almost every curious child in this universe has thought about the effects that a black hole could have on Earth, or at least on the people living here. Frank Hale of Stanford University has suggested what might have happened if a coin-sized black hole, which would have approximately the same mass as Earth, ended up in the center of the planet. Not that the Earth is sucked in by a space vacuum cleaner, but there will still be some commotion.
Matter falling into the black hole will become extremely hot, causing radiation and pressure to push out the outer layers of matter and cause a spectacular explosion that fired from Earth like superheated plasma. Conservation of momentum will ensure that Earth's mass rotates faster around the black hole and creates an accretion disk that will limit the rate at which Earth's mass is absorbed. The earth will turn into rapidly revolving ruins, but it will take some time before it is eaten.
A smaller black hole won't be so bad. The universe is believed to be teeming with primordial black holes with a mass equivalent to a small mountain. These black holes lurk inside the gas giants and lead to the birth of premature supernovae. If such a black hole crashes into the Earth at high speed, it may just fly right through. Such a collision will result in a release of energy equivalent to the explosion of a ton of TNT, but it will stretch along the entire length of the path, so that hardly anyone will notice. However, the passage of such a black hole through the Earth will leave behind "a long tube of material heavily damaged by radiation, which will remain recognizable over geological time."
Things would be darker if the solar system collided with a supermassive black hole with a mass a million times the mass of the sun, possibly ejected by the gravity of two colliding galaxies. Astronomer Christopher Springob believes that we would suspect something was wrong when the black hole approached 1000 light-years from the solar system. After that, we would have only a few thousand years left to prepare for its arrival, after which this black hole will significantly disrupt the orbits of the planets and bite into the star system. When the black hole is within a light-year, its gravity will tear the world apart so that the Earth will be well chewed before being finally swallowed.
Or not. Samir Mathur of Ohio State University believes he has mathematical proof that we might not even notice that we are being eaten by a black hole.