The sun travels so predictably across the sky that you would not notice that its connection with Earth is constantly changing. In actuality, the average distance between Earth and the sun does not remain constant from year to year. So, do we know if the Earth is moving closer or further away from the sun? And what factors are at work on our planet and star to bring this about?
In short, the sun is gradually moving away from Earth. According to NASA, Earth is around 93 million miles (150 million kilometers) from the sun on average (opens in new tab). Its orbit, however, is not exactly round; it is somewhat elliptical, or oval-shaped. According to NASA(opens in new tab), the Earth's distance from the sun may range from 91.4 million to 94.5 million miles (147.1 million to 152.1 million kilometers).
Nonetheless, the average distance between Earth and the sun is gradually growing over time. There are two key reasons for this increased distance. The sun is shedding mass, for example. The other involves the same forces that create Earth's tides.
The sun is becoming smaller.
The sun's nuclear fusion processes convert mass to energy using Einstein's famous equation E = mc2. Because the sun is always generating energy, it is also losing mass. According to NASA(opens in new tab), the sun's remaining lifetime — estimated to be another 5 billion years or so — models of how stars evolve over time predict the sun will lose about 0.1 percent of its total mass before dying, according to Brian DiGiorgio, an astronomer at the University of California, Santa Cruz, in an email to Live Science.
Although 0.1 percent may not seem like much, "this is a lot of mass," according to DiGiorgio. "It has almost the same mass as Jupiter." According to the Exploratorium(opens in new tab) in California, Jupiter is approximately 318 times the mass of Earth.
The magnitude of an object's gravitational attraction is proportional to its mass. Because the sun is losing mass, its gravitational attraction on Earth is lessening, causing our planet to drift away from our star at a rate of around 2.36 inches (6 centimeters) every year, according to DiGiorgio. But we shouldn't celebrate the sun's departure just yet.
"This is very small, especially when compared to the typical change in Earth's orbital distance caused by its somewhat elliptical orbit — roughly 3%," DiGiorgio added.
The impact of tides
Earth's gravity tugs on the sun in the same way that the moon's gravitational pull causes tides. Britt Scharringhausen, an associate professor of physics and astronomy at Beloit College in Wisconsin, wrote for Cornell University's Ask an Astronomer(opens in new tab) page that this expands the side of the sun that faces Earth, resulting in a "tidal bulge."
The sun rotates on its axis about formerly every 27 days, according to NASA( opens in new tab). Because this is faster than the 365 or so days it takes for Earth to complete a route around the sun, the tidal bulge Earth generates on the sun sits ahead of Earth. The bulge's mass has a gravitational pull associated with it, lugging Earth ahead on its route and slinging it further from the sun, Scharringhausen noted. ( A analogous effect is leading Earth's moon to sluggishly drift down from our earth( opens in new tab).)
still, these tidal forces have a veritably weak effect on Earth's route They beget Earth to move about0.0001 an inch(0.0003 cm) down from the sun every time, DiGiorgio calculated.
Is there a major shift in the weather?
Might Earth's growing distance from the sun influence Earth's climate?
" As the Earth moves down from the sun, the sun's light will come dimmer," DiGiorgio said. Given that Earth's distance from the sun may grow by0.2 over the coming 5 billion times," this dimming corresponds to an a0.4 reduction of solar energy hitting the Earth's face," he said." This is fairly small compared to the normal variations in the sun's brilliance that be due to the Earth's elliptical route, so it's not important to worry about."
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The bigger thing to worry about" is that as the sun evolves over the coming 5 billion times, astral elaboration models prognosticate that it'll increase in brilliance by about 6 every 1 billion times, sluggishly adding Earth's temperatures and boiling off the abysses," DiGiorgio said." This will render the Earth uninhabitable to humans long before the sun ever potentially quaffs it."
Unwanted influence
Recent work suggests the routeways of Jupiter and other globes in the solar system have changed over time. So could their routeways grow unstable enough to one day influence Earth's route, hurling it closer to or further from the sun? Or might some other mischief body pass near enough to the solar system to have an analogous effect?
" The problem with trying to prognosticate the gravitational relations of numerous- body systems like the solar system or near stars is that they are chaotic, meaning they are insolvable to prognosticate with any certainty," DiGiorgio said." We've no idea where, specifically, the globes will be on timescales longer than around 100 million times because the bitsy crimes in dimension and disquiet from unmodeled relations grow too large over time."
Still," we can use this chaos to our advantage by running numerous simulations of the same chaotic system to see what the probability of an event being is," DiGiorgio said. This is analogous to how prophetic rainfall models work, he noted.
A 2009 study in the journal Nature( opens in new tab) that performed about,500 simulations of the solar system set up that in about 1 of them, Mercury's route came unstable, causing it to crash into either the sun or Venus." So it's theoretically possible for Mercury to move by the Earth and change its route mainly, as it did to Mars in one simulation," DiGiorgio said." This is veritably doubtful, however, as seen by its oddity in their simulations."
It's also veritably doubtful that a passing star, earth, or other body may undo Earth's route, DiGiorgio said." My reverse- of- the- envelope computations say that we should only anticipate a star to come closer than the route of Pluto about formerly every trillion times," DiGiorgio said." Any comets formerly in our solar system will not have enough mass or energy to affect our route mainly moreover."
The death of the sun
After the sun's hydrogen fuel runs out in around 5 billion years, it will begin to inflate and turn into a red giant star. Will Earth have grown far enough away from the dying sun to escape our star's death throes if it continues on its current path?
According to DiGiorgio, there is now considerable debate regarding how much the sun will expand during its red giant phase. There's a chance it won't inflate up enough to hit Earth, which means our planet may survive and keep orbiting. However, most projections indicate that the sun will become large enough to consume Earth, causing the planet to spiral "inwards towards annihilation," according to DiGiorgio.
"However, even if the Earth survives, humans have little chance of surviving with it," DiGiorgio remarked. "The heat and radiation from the advancing sun would likely boil not just the seas and atmosphere, but also the Earth itself. Humans would have to flee the raging lava ball before it could be consumed."
If humanity were still alive in 5 billion years and wanted Earth to stay livable throughout the sun's expansion, we would have to progressively shift the planet outward to about Saturn's orbit, keeping it temperate enough for life as we know it while the sun continued to emit more and more energy.
"However, this is really unrealistic," DiGiorgio remarked. "The simpler option would be to just depart Earth and live on another planet or solar system."
