Is there anything ‘below’ Earth in space?

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if you have seen Illustration or model of solar systemmaybe you noticed that all the planets orbit the sun more or less in the same plane, and in the same direction.

But what is above and below that plane? Why do the orbits of the planets line up like this on a flat pancake, rather than each planet orbiting in a completely different plane?

i am a planetary scientist who work with robotic spacecraft, e.g. wanderer and Orbiter. It’s important for my colleagues and I to have a 3D map of our space neighbors as we send them out to explore our solar system.

Which way is “down”?

Earth’s gravity Has a lot to do with what people think is up and what is down. Objects will fall toward the ground, but the direction depends on where you are.

Imagine you’re standing somewhere in North America, pointing your finger downward. If you stretched a line from your fingertip all the way across the Earth, that line would point in the “up” direction of someone On a ship in the southern Indian Ocean.

From a larger perspective, “down” can be defined as below the plane of the solar system, below the plane of the solar system. ecliptic. By convention, we say that the plane above is Planet rotates counterclockwise Orbiting the Sun, they spin clockwise when viewed from below.

More “down” flavor

Is there anything special about the downward direction relative to the ecliptic? To answer this question, we need to look even further. Our solar system is centered around the sun, of which the sun is just one About 100 billion stars In our galaxy, the Milky Way.

Each of these stars, and their associated planets, are Orbiting around the center of the Milky Waylike a planet orbiting a star, but on a much longer time scale. Just as the planets in the solar system do not orbit randomly, the stars in the Milky Way orbit around the center of the galaxy close to a plane called the “Milky Way.” galactic plane.

This plane is oriented differently than the ecliptic in our solar system. In fact, angle between two planes It’s about 60 degrees.

To take a step back, the Milky Way is part of a known cluster of galaxies local groupsand—and you can see where this is going—most of these galaxies fall within another plane, called the supergalactic plane. The supergalactic plane is almost perpendicular to the galactic plane, The angle between the two planes is approximately 84.5 degrees.

How these objects end up on a path that approaches the same plane has to do with how they were formed in the first place.

Collapse of the Solar Nebula

The material that ultimately makes up the Sun and the planets in our solar system began as a diffuse, very extensive cloud of gas and dust called solar nebula. Every particle in the solar nebula has a tiny mass. because of any mass exerts gravitational forcethese particles attract each other, albeit very weakly.

Particles in the solar nebula begin moving very slowly. But over long periods of time, the mutual attraction these particles feel due to gravity causes The clouds begin to shrink inward, shrinking.

The Solar Nebula also has some very slight overall rotation, possibly due to the gravitational pull of a passing star. This rotation speeds up as the clouds collapse, much like a spinning figure skater spinning faster and faster as she pulls her arms toward her body.

As the clouds continue to shrink, individual particles get closer to each other and have more and more interactions due to gravity and collisions between particles, affecting their motion. These interactive This causes individual particles whose orbits are tilted away from the direction of the cloud’s overall rotation to realign their orbits.

For example, if a particle descending across an orbital plane strikes a particle ascending across that plane, the interaction tends to cancel the vertical motion, and realign their orbits Enter the plane.

Eventually, the once amorphous cloud of particles collapsed into a disc shape. Then Particles in similar orbits begin to cluster togethereventually forming the Sun and all the planets orbiting the Sun today.

On larger scales, similar interactions may eventually confine most of the stars that make up the Milky Way to the galactic plane, and most of the galaxies that make up the Local Group to the supergalactic plane.

The ecliptic, galactic, and supergalactic planes are all oriented back to the initial random rotation of the clouds from which they formed.

So what’s underneath the Earth?

So there’s really nothing special about the direction we define as “down” relative to the Earth, except for the fact that there aren’t many objects orbiting the Sun in that direction.

If you go far enough in this direction, you’ll eventually find other stars with their own planetary systems orbiting in completely different directions. If you go further, you might encounter other galaxies that have their own planes of rotation.

This question highlights one of my favorite aspects of astronomy: it puts everything into perspective. If you asked a hundred people on the street, “Which way is down?” they would each point in the same direction. But imagine you asked the question people from all over the earthor intelligent life forms in other planetary systems or even other galaxies. They all point in different directions.

This edited article is reprinted from dialogue Licensed under Creative Commons. read Original article.