[flatbutt]

Originally Posted by masraum

Nope, the 17k mph is almost certainly correct. Also the speed moving away from the earth (including the deceleration) is probably correct.

Imagine that you've got a weight on the end of a 6' string , and you're holding the string and spinning the weight around above your head, maybe 36 feet per minute in a circle. Also imagine that there's a tree 8' away. If you start slowly letting more string out, say 1" of string every 5 seconds. That would mean that the weight on the end of the string was approaching the tree at 1 foot per minute, but the weight on the end of the string is spinning at 36 feet per minute.

That's how Webb is approaching at one speed, but going another. Also, as the distance from the earth increases, the circumference of the orbit also increases, which means that it takes longer to complete and orbit and therefore the orbits are getting larger at a slower rate.

Also, one must consider that there is a difference between orbital velocity and escape velocity (which is indeed 17k mph). Orbital velocity being the speed that is required to reach extended orbit of a planet or star whereas escape velocity is the speed that is required to escape Earths gravity well.


Webb is nearly 200,000 miles out already!