You might not know that the sun's relationship with Earth is changing all the time, because the sun moves in such a predictable way. The average distance between Earth and the sun is not always unchanging. We don't know if Earth is getting closer to the sun. What are the forces that are making this happen?

The sun is getting closer to Earth. The average distance from the sun to Earth is about 15 million kilometers. It's slightly elliptical, but it's not a perfect circle. NASA says the Earth's distance from the sun can be between 91.4 million and 94.5 million miles.

Over time, the expanse between Earth and the sun is growing. The growing distance is caused by two factors. The sun is losing weight. The tides on Earth are caused by the same forces.

The sun will explode.

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The sun is shrinking

Nuclear fusion reactions that power the sun convert mass to energy. The sun is losing mass because it is constantly producing energy. Over the course of the sun's remaining lifetime, according to NASA, models of how stars evolve over time predict the sun will lose a small amount of its mass before it dies.

"This is a lot of mass," Di Giorgio said. About the same amount of mass as Jupiter. According to the Exploratorium in California, Jupiter is nearly three times the mass of Earth.

The strength of an object's pull is determined by the amount of mass it has. Our planet is drifting away from our star because the sun is losing mass. The sun should not be thrown a party just yet.

The normal variation in Earth's orbital distance is about 3%.

The effects of tides

Earth's gravity tugs on the sun just as it tugs on the moon. The "tidal bulge" on the side of the sun that faces Earth is caused by this stretching.

According to NASA, the sun rotates on its axis about once a month. The tidal bulge Earth creates on the sun sits ahead of Earth because this is faster than the time it takes for Earth to circle the sun. The bulge's mass has a pull on it that pulls Earth ahead on its path and throws it away from the sun. The effect is leading the moon to drift away from the planet.

DiGiorgio calculated that the tidal forces cause Earth to move less than one inch away from the sun each year.

Any major change in climate?

Earth's distance from the sun may affect the climate.

The sun's light will become dimmer as the earth moves away. The 0.4% reduction in solar energy hitting the Earth's surface is due to the dimming of Earth's distance from the sun. It's not much to worry about since this is relatively small compared to the normal variations in the sun's brightness.

What is the maximum number of planets that could be in the solar system?

According to stellar evolution models, the sun will increase in brightness by about 6% every 1 billion years, slowly increasing Earth's temperatures and boiling off the oceans. The Earth will be rendered uninhabitable to humans by this.

Rogue influence

Jupiter and other planets in the solar system have changed over time, according to recent research. Is it possible that their orbits could become unstable enough to affect Earth's position on the planet? Maybe another rogue body will have the same effect on the solar system.

The problem with trying to predict the interactions of many-body systems is that they are chaotic, meaning they are impossible to predict with any certainty. We don't know where, specifically, the planets will be on timescales longer than 100 million years because of the tiny errors in measurement.

DiGiorgio said that they can use the chaos to their advantage by running many simulations of the same chaotic system. He pointed out that this is similar to how weather models work.

A diagram of the planets in our solar system with the planets names. From left to right: the sun (bright yellow), Mercury (smallest, brown), Venus (slightly bigger, reddish-brown), Earth (slightly bigger, blue and green), Mars (slightly smaller, red), Jupiter (biggest, brown and beige), Saturn (slightly smaller, beige with a yellow ring around it), Uranus (smaller, but bigger than Earth grey), and Neptune (slightly smaller, blue). There are also white rings to show the orbit of each planet.

A diagram of the planets in our solar system. (Image credit: ChrisGorgio via Getty Images)

In a study done in the journal Nature, it was found that in about 1% of the simulations, Mercury became unstable and crashed into the sun or Venus. It is possible for Mercury to move by the Earth in a similar way that it did to Mars. It is very unlikely as seen in their simulations.

DiGiorgio said that it is very unlikely that a passing star, planet or other body would cause a problem. "My back-of-the-envelope calculations show that we should only expect a star to come close to the dwarf planet about once every trillion years," he said. "Any comets that are in our solar system won't have enough mass or energy to have an effect on us."

The sun's death

After the sun exhausts its hydrogen fuel, it will become a red giant star. Will Earth be able to survive the death throes of our star if it continues on its course?

Some people disagree about how much the sun will swell during its red giant phase. Our planet may survive because there is a chance it won't reach Earth in time. The planet will spiral towards oblivion if the sun grows enough to swallow it, according to most estimates.

Humans would not be able to survive with the Earth. The sun's heat and radiation would likely boil the oceans and atmosphere, but it would also boil the Earth. Humans would have to leave the ball in order to eat it.

If humans are still around 5 billion years from now, we would have to slowly move the planet out of the way of the sun in order to keep it warm.

DiGiorgio said that this is impractical. Abandoning Earth and finding another planet to live in would be the easiest solution.

It was originally published on Live Science