Earth has traditionally been the third rock from the sun, which makes visiting Jupiter inconvenient. Couldn’t we just move Jupiter closer?
Lucas from Wild Rose Elementary asked Scientific St. Albert, “What would happen if the planets switched order?”
Astronomers say the answer is either “nothing much” or “everyone dies,” depending on which planets you switch.
The current order
If you start from the sun, the order of planets in our solar system is Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
Researchers don’t have a firm idea as to why they are in that order, as they’re not sure how the planets formed.
One theory is that the solar system started as a big blob of gas, some of which collapsed by gravity to form the sun, explained Mathieu Dumberry, professor of planetary physics at the University of Alberta. The sun made it too hot for ice to form close to it, so the planets near it tended to be rocky, built up from clumps of rocks glomming together. Further out, it was cool enough for gas and ice to condense together, resulting in gas giants. The current order of those gas and rocky planets is largely due to chance.
Some theories, particularly the Nice Model, say the planets in this solar system have actually changed position in the past, noted Chris Mann, a PhD student and exoplanet scientist at the University of Montreal. This model says Neptune was originally much closer to the sun than it is now, but flew further out due to interactions with rings of rocks, Jupiter, and Saturn. It also swapped positions with Uranus at some point.
Mann noted that recent research suggests the “rocks inside, gas outside” order of our star system is actually pretty weird, as most of the other star systems we’ve spotted don’t follow that pattern. There are lots of Jupiter-sized planets right next to stars, for example, and far more Neptune-sized planets than we have here.
“Our solar system is not normal,” Mann said.
Shuffle mode
There are several ways we could shuffle our planets into different positions, Mann said. We could crack the Earth in half and kick one half away from us really hard (you may need to be Superman to do so), for example, or lob a whole bunch of asteroids past Earth, stealing momentum from each in a way similar to how satellites slingshot around planets to gain speed.
“You’d have to do this a whole lot,” Mann said of the latter, as each asteroid would only have a tiny effect on the Earth’s course.
Mann said we could move Earth more easily if we had an ultra-massive object we could position next to it — say Nemesis, the sun’s hypothetical twin. Gravity from said object would tug on the Earth, changing its position over time.
Let’s assume we have the omnipotent Q from Star Trek snap his fingers and rearrange planets for us.
In most cases, all this does is make the planets hotter or colder, based on whether they move closer to or farther from the sun. The sun contains 99.8 per cent of the mass in this star system and is the dominant gravitational force, Mann said. Moving everything else around, with one exception, would do little to change any orbits.
It would, however, affect life on Earth.
Earth is in the “Goldilocks Zone” where it is the right distance from the sun to have liquid water, Dumberry and Mann explained. If we swapped Earth with Venus or Mercury, it would be too close to the sun and too hot. All water would boil away, and all life would die.
Swap Earth with Mars, and life around the equator might survive, but St. Albert would probably be buried under ice, Dumberry said. Any further out and all surface water would freeze. Fish might survive if heat from the Earth’s core kept some deep waters liquified. Researchers suspect some of Jupiter’s moons might have liquid water beneath their frozen surfaces.
Jupiter’s a jerk
The one planet that would cause chaos if it moved is Jupiter.
“Jupiter is the big bully in our solar system,” Dumberry said, as it’s the biggest planet around — its Great Red Spot alone is twice the size of Earth.
Swap Jupiter with any other planet, and its gravity would start messing with everyone else’s orbits, Dumberry said.
“These planets would either be flung away to crash into the sun or crash into Jupiter or be sling-shotted away to outside the solar system.”
While it’s not really practical to reorder the planets, Mann and Dumberry said thinking about doing so can help us determine what solar systems are possible and how ours came to be in its current state.
“Part of the reason we study other planets is to also understand Earth,” Dumberry said.
