221–230 of 517 posts
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Doesn’t relativity tell us it doesn’t matter?
PBS Space Time recently explained what the present time means within general relativity[1]. As I understand it... it matters in this context. [1]: https://www.youtube.com/watch?v=EagNUvNfsUI
Something I don't understand: when they say "X is 1 minute from happening", does that mean it's really 1 minute from happening or does that mean "in 1 minute we'll receive the signal that X has happened"? Maybe my question makes more sense in the case of "X is happening right now", because then I should either understand "we infer that X should have happened right about now" or "we have confirmed via signal that X ha…
Waiting for the physicist in the room to point out: there is no such thing as simultaneity! :)
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Yes, yes, you have shown you know what relativity is. But the relative velocity of earth and mars — which I can't convince Wolfram Alpha to tell me, but it's got to be on the order of their orbital velocity so let's say 5x10^4 mph — is a tiny tiny fraction of c so their inertial reference frames are essentially identical. So sitting in our reference frame, we can make inferences about what's happening "now" on mars,s…
Now is the part where someone brings up even with the low relative velocity, you haven’t accounted for the simultaneity issues we’d have if the earth collided with a black hole while the rover landing was happening.
Apparently the copter was made with off-the-shelf parts. I wonder if I can cop a replica somewhere, and how it would fly considering it is built for martian air
1. See page 20 of the launch press kit: https://www.jpl.nasa.gov/news/press_kits/mars_2020/download/...
I have serious doubts that this actually happened
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The Space Shuttle was reusable (with massive refurbishing after each flight) but given that'd it cost significantly more than a non-reusable rocket per pound I think the point stands. SpaceX managed to make a financially viable reusable rocket.
They really didn't. SpaceX is not cheaper than the shuttle no matter how many times it gets repeated. That SpaceX fudges the numbers so it is hard to compare doesn't make it true. In reality SpaceX is more expensive than not only the shuttle but also their own projections. Here's a breakdown: https://youtu.be/4TxkE_oYrjU
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They did, you're not wrong at all, but just to add a little bit of clarity the space shuttle was never as reusable as was hoped - it wound up costing a huge amount of time and money to retrofit the shuttle again before each launch. Reusable and Re-usability are different things :P As far as I know no solid state boosters were ever re-used (how would that work?) - but then again SpaceX doesn't re-use solid state boost…
The SRB segments vere regularly reused, not sure about the parachutes and the nozzle stearing gear. Still reportedly it was more expensive to reuse the segments (basically big metal tubes) than to build new set if SRBs for each flight, possibly using better techniques (monolithic carbon fibre overwrapped solid motors, like on Ariane 5/6).
I stopped watching videos like these when they started chanting like some crazy cult when things went well (USA! USA! USA!). No wonder we can't just get along.
Something I don't understand: when they say "X is 1 minute from happening", does that mean it's really 1 minute from happening or does that mean "in 1 minute we'll receive the signal that X has happened"? Maybe my question makes more sense in the case of "X is happening right now", because then I should either understand "we infer that X should have happened right about now" or "we have confirmed via signal that X ha…
It's the latter. The Earth-Mars latency at this time is something like 11 minutes, and the landing itself takes about 7 minutes, so when we on Earth first saw the craft entering atmosphere on Mars, by that time all the landing was already over, one way or another.
Apparently the latency time is currently 11 mins 22 seconds -- which is somewhere near the average. It goes from under 4 mins to over 22mins depending on distance.