4 ms·

Hang on, wouldn't this make that manhole cover also the furthest manmade object from Earth? Voyager 1, even after all of its slingshots, is traveling at about 3

Hang on, wouldn't this make that manhole cover also the furthest manmade object from Earth? Voyager 1, even after all of its slingshots, is traveling at about 38k mph. That manhole cover is traveling several times faster, and was launched decades before Voyager even thought about taking off. Edit: And before anyone mentions the fact that Brownlee's calculation did not take into consideration atmospheric forces (which probably disintegrated the cap before it got to space), at least some molecules of the cap probably did go that far, and would still remain the fastest, and possibly furthest object from Earth (assuming it did not get caught in the gravity well of another object on its way out).

short_sells_poo 5y ago
You are probably right. Although I'd assume that given the cover was very close to the epicenter of the detonation, it would've been almost instantly vaporized and turned into plasma even before air resistance would've done the job.
- LorenPechtel 5y ago
  The manhole cover *did* survive the detonation--it's visible one *one* frame of film. Unfortunately, only one so there's no way to figure out it's velocity. All they can conclude is a minimum velocity based on the fact that it's not on two frames. There have been objects placed even closer to nukes that have survived and note Project Orion--not only objects near a bomb, but the plan was to put a crew near bombs. Obviously, they would catch some radiation but that's going to happen anyway in deep space flight and back then they didn't realize the cancer risk. The basic physics of protecting the ship and crew from the nearby detonations is clear. There is some question about whether it could actually be used to take off from Earth, though--it's not so certain if the pusher plate could be kept cool enough during the ride to orbit. Deep space doesn't require such sustained thrust, it's no problem. EMP from near-Earth detonations is a big issue, though.
LorenPechtel 5y ago
Why would any molecules make it out of the atmosphere? The mean free path at low altitude is very short.

short_sells_poo 5y ago

You are probably right. Although I'd assume that given the cover was very close to the epicenter of the detonation, it would've been almost instantly vaporized and turned into plasma even before air resistance would've done the job.

LorenPechtel 5y ago
The manhole cover *did* survive the detonation--it's visible one *one* frame of film. Unfortunately, only one so there's no way to figure out it's velocity. All they can conclude is a minimum velocity based on the fact that it's not on two frames. There have been objects placed even closer to nukes that have survived and note Project Orion--not only objects near a bomb, but the plan was to put a crew near bombs. Obviously, they would catch some radiation but that's going to happen anyway in deep space flight and back then they didn't realize the cancer risk. The basic physics of protecting the ship and crew from the nearby detonations is clear. There is some question about whether it could actually be used to take off from Earth, though--it's not so certain if the pusher plate could be kept cool enough during the ride to orbit. Deep space doesn't require such sustained thrust, it's no problem. EMP from near-Earth detonations is a big issue, though.

LorenPechtel 5y ago

Why would any molecules make it out of the atmosphere? The mean free path at low altitude is very short.