In space, if the ISS is traveling at 17,150 miles per hour how does it look so stationary in the video from the Dragon capsule. Also How does it dock so precisely when it is moving so fast.
In: Physics
Because the capsule is matching speed. Relative to the surface of the earth, both the capsule and ISS are travelling at the same speed. Relative to each other, they are barely moving as they speeds are matching and at the point of docking, they are not moving at all.
Because the Dragon capsule is traveling at a similar speed. Relative to one another, they are moving slowly.
To my understanding, it’s all about relativity. Yes, the ISS is moving incredibly fast, but so is the dragon capsule. It’s kind of like if you’re running with a friend. You’re both moving quickly, but your friend won’t look like they’re moving fast, or at all, relative to your pace, if that makes sense. That’s why docking can be so precise. The ISS is moving very close to the same speed, so it’s not like the dragon capsule will go crashing through the space station. They’ll just start going the exact same speed. Source: Took physics and astronomy
Their velocities (speeds) are relative, meaning that they are both travelling almost as fast as each other.
If two cars travel in sequence along a long, straight road at 60mph within 3ft of each other, as long as their speeds are completely stable they will always remain 3ft apart. But, if the car behind increases speed by just 1mph, they will gently touch bumpers (fenders) in a short while.
So, if you could block out the passing scenery and only view the car in front from the one behind, the relative speeds would make it seem like they weren’t moving at all. As soon as the car behind accelerates by 1mph, it would be perceived as a slow creep towards the car in front until bumpers touch.
It’s only the passing scenery, which is stationary, that gives you the relative impression of speed. Without that, you could be moving at incredible velocity, but you never perceive it unless there is something else for that velocity to be relative to.
Of course, if you’re accelerating at the time, the G-force will give a perception of speed, too. I refer to mostly stable velocities.
I think that’s the basic premise, no doubt others will explain it better.
Edit – shoddy spelling. Damn you, autocorrect.
You are currently moving at about 67000 mph through space. You can’t feel it because the air and everything around you is also moving at 67000 mph. You can walk through doorways and park your car at 67000 mph as long as this remains true. The Dragon capsule and the space station were travelling at the same speed as they docked. Just like you and your car or the doorway. If they were still in the atmosphere then things would be different but as the air at that altitude is pretty much none existent so they don’t feel like they are moving any quicker than we are on the ground
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It’s about *relative* speed.
Imagine you and I are on the bullet train which is travelling at its top speed. We’re both rocketing along at 200mph, but inside the cabin, we’re actually stationary in relation to each other.
So, if I throw a tennis ball to you and throw it at 5mph in the direction the train is moving, that ball is only moving at 5mph relative to you. You see the ball coming towards you at about average walking pace so it’s easy to catch… but to someone standing by the side of the track, when I throw that ball, it’s moving at 205mph relative to them. You’ve just caught a ball travelling at 205mph.
Think of it this way: right now the Earth is spinning at 1000mph. It’s orbiting the sun at about 66,000mph, and our solar system is orbiting around the center of the galaxy at 828,000mph.
So, from the perspective of someone standing at the center of the galaxy, when you park your car, you’re manuevering it into a parking spot while travelling nearly a million miles per hour.
How can you smile and wave and say ‘hi’ to a person in another car, while both of you are travelling at 80mph? Absolute speed doesn’t matter. Only the difference in speeds matters.
It’s moving 17,150 mph relative to *us*, but what matters for docking is how quickly it’s moving relative to the ISS. We are completely irrelevant at that point. At the point of docking, they’re basically moving at the same speed relative to us, so their speed with respect to each other is basically 0. It’s like if you’re in a car and your friend’s car pulls up next to you. You guys can be driving as fast as you want, but you can still do things like pass stuff back and forth between the cars without having to take their speed relative to the road into account. This is basically the whole idea behind reference frames. In their view, it’s the road that’s moving quickly, and that’s perfectly valid. Neither of those reference frames us any more valid or right than the other. Physics is the same in both of them. That’s the beauty of relativity.
You can extend the same idea to the Earth. The Earth is orbiting the Sun, the Solar System is moving through the galaxy, the galaxy is moving in our local group, our local group is moving with respect to other clusters. That’s a *ton* of motion, but everything seems still here.
If you are eating a cheesburger in your car traveling at 60 MPH, the cheeseburger is also traveling 60 MPH.
Now if someone throws a cheesburger into your mouth at 60 MPH, there can be problems.
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