How is there gravity in space

Astronauts in orbit are more accurately in free fall. They just happen to be also moving fast enough that they keep missing the ground. Gravity does weaken with distance. But for massive objects like stars and planets, their gravitational reach is enormous.

Instead, Earth keeps it on a gravitational tether. Likewise, the Sun retains a grasp over not just Earth and Jupiter and Pluto, but even the Oort Cloud of comets , which extends a full light-year away. The Sun is subject to the gravity of the massive black hole at the center of the Milky Way.

And the Milky Way itself dances to the gravitational drumbeat of other nearby galaxies. They just happen to be also moving fast enough that they keep missing the ground. Gravity does weaken with distance. But for massive objects like stars and planets, their gravitational reach is enormous. Instead, Earth keeps it on a gravitational tether. Likewise, the Sun retains a grasp over not just Earth and Jupiter and Pluto, but even the Oort Cloud of comets , which extends a full light-year away.

The Sun is subject to the gravity of the massive black hole at the center of the Milky Way. And the Milky Way itself dances to the gravitational drumbeat of other nearby galaxies. How to understand Einstein's theory of gravity.

What's the maximum gravity we could survive? How many exoplanets are there in the universe? Receive news, sky-event information, observing tips, and more from Astronomy's weekly email newsletter.

View our Privacy Policy. By signing up you may also receive reader surveys and occasional special offers. We do not sell, rent or trade our email lists. Login or Register Customer Service. RISE —. PHASE —. Tonight's Sky — Change location. US state, Canadian province, or country. Basically, you get in a car that drops off a tower. During the fall, you feel weightless—but you don't crash at the bottom.

Instead, the car is on a track that somehow slows down more gradually than if it smashed into the ground. How about another example? If you are in an airplane and the plane flies with a downward acceleration, everyone inside will be weightless. Even a dog. Check it out. View Iframe URL. In the end, there seems to be huge misunderstanding about gravity. I believe the reasoning follows like so: Astronauts are weightless in space.

There is no air in space. Therefore, if there is no air, there is no gravity. Here's how you'll see it: Some dude is floating around in space that's OK and then he enters the airlock of a spacecraft, still floating. The airlock door shuts and air is pumped into the chamber and boom —he falls to the ground because now there's gravity.

Here is what it should look like—from the epic movie A Space Odyssey. Not even for Dave. That scene is pretty much perfect. They even have no sound until the air comes in. Now back to the events in The The scene doesn't take place in orbit, it occurs during reentry. This is the part where the spacecraft enters back into the atmosphere and encounters an air resistance force because there is air.

Let me start with a simple force diagram showing the spacecraft at some point during this motion. Clearly, this not weightless. Yes, there is a gravitational force acting on everything—but there is also that air drag force that will make the spacecraft slow down as it moves down. If the human is going to stay inside the spacecraft, there must also be an extra force on that human from the floor. So, not weightless—in fact, the human would feel more than normal gravity because of the acceleration.

You already know this, though, because the exact same thing happens to you in an elevator. As the elevator is moving down and coming to a stop, it is also slowing down.

During this time, you would feel a little bit heavier because of the force from the floor pushing on you. You aren't really heavier, you just feel that way because of the acceleration.

Again, there is another movie example where someone gets this reentry physics right. It's from Apollo Notice the water falling from the ceiling.

In this case, the capsule is moving downward at an angle. However, the air resistance force is pushing in the opposite direction of motion causing the spacecraft to slow down. But what slows down the water? The water does cling to the surface a little bit—but the acceleration is too much to keep it there and it "falls" towards the astronaut. Note that "falling" here doesn't mean straight towards the surface of the Earth but rather just in the opposite direction as the acceleration. Looking back at the scene from The , here's how they could fix the scene—and it's pretty simple.