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
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.
Because the Dragon capsule is traveling at a similar speed. Relative to one another, they are moving slowly.
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.
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
You know the earth is moving at something like 67,000 mph around the Sun and it yet we can throw a ball and catch it without thinking too much.
Why does it seem like that car infront of you isn’t moving when he’s doing 75 mph? Because you’re doing 75 mph.
Except the car infront of you is the ISS and you’re Crew Dragon.
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.
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.
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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.
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