211–220 of 517 posts
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Waiting for the physicist in the room to point out: there is no such thing as simultaneity! :)
Came here to suggest The Order of Time by C Rovelli, which explains this in such a captivating way.
i wish they would stream the video and audio from the craft live as it descends to the martian surface
The bandwidth to stream video from mars simply isn't available. Once it's landed, perserverance must lock onto sattelites orbiting mars in order to send media back to earth.
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> I think the point stands No it doesn't. The person was trying to say SpaceX > NASA. Many people here are trying to shit on the other side as if they have a real point. They're both doing cool and useful things and they're both really really good at what they do.
I'm not trying to say that SpaceX is better than NASA. I am responding to the point that NASA has done things that SpaceX hasn't (e.g. landing on other celestial bodies) by pointing out that SpaceX has done things NASA hasn't (e.g. SpaceX rockets land and can be reused). I don't think it makes sense to talk about which is better unless there is some specific metric that can be measured so a conclusion could be reache…
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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It depends on what coordinate system you're using. Simultaneity is ill defined in relativity. There's only future, past and "spacelike-separated" (neither past nor future). When they say, "X is 1 minute from happening," it's actually neither in the past nor the future. It's currently spacelike-separated, but in 1 minute, it will be in our past.
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…
You can also watch an EDL visualization in your browser: https://eyes.nasa.gov/apps/mars2020/#/home And read about how it will use Terrain Relative Navigation to find a safe landing spot: https://www.jpl.nasa.gov/news/a-neil-armstrong-for-mars-land... Perseverance is phenomenally complex, its Sample Caching System alone contains 3,000+ parts and two robotic arms. So exited for all the sciencing this nuclear-powered,…
They put those in to make the probe seem higher-quality. They got the idea from Beats headphones.
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Other posters have pointed out that it's the hazard avoidance camera, but they haven't said why the hazard avoidance camera is black and white. When you do computer vision, the first step you do is convert your color image into a black and white image, and run your CV algorithms on the black and white image. This is because when you're looking at objects and shapes and stuff, it's contrast that tells you where the bo…
Thank you for the explanation. That was highly interesting. Does anyone else know if the human eye does perceive color directly? Is this at all technically possible? And if yes, why aren't we doing it with cameras?
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Other posters have pointed out that it's the hazard avoidance camera, but they haven't said why the hazard avoidance camera is black and white. When you do computer vision, the first step you do is convert your color image into a black and white image, and run your CV algorithms on the black and white image. This is because when you're looking at objects and shapes and stuff, it's contrast that tells you where the bo…
Thank you for the explanation. That was highly interesting. Does anyone else know if the human eye does perceive color directly? Is this at all technically possible? And if yes, why aren't we doing it with cameras?
Long answer: Colour is a very rabbithole topic but Captain Disillusion has a summary of it (https://youtu.be/FTKP0Y9MVus) and Technology Connections has a discussion (https://youtu.be/uYbdx4I7STg).
NASA's ability of succeeding at landing things successfully on the first try on foreign bodies since 1969 is mind-blowing. Meanwhile, SpaceX takes half a dozen tries before managing to do the same on a fully known environment on Earth.
SpaceX has a very different set of risk tolerances and approaches. Nasa is a government funded entity and the tolerance for failure (rightly or wrongly) is very low according to every thing I've read. SpaceX being private has a much larger cushion for failure. Elon will keep funding it far longer than congress would Nasa is my guess. If SpaceX loses some rockets that's the cost of business, of course once those missi…
Also, SpaceX IS mostly funded by NASA anyway as a government contractor. SpaceX exists because the government wanted to create a private space market. Strangely thank George Bush for it. https://www.fool.com/investing/2017/02/05/how-profitable-is-...
As you can see, SpaceX was so cash strapped in 2017 it obviously didn't go to mars in 2018 as they wanted. Also notice Elon didn't fund that trip (otherwise it would have happened). There is no way he would risk HIS own money on that.
NASA's ability of succeeding at landing things successfully on the first try on foreign bodies since 1969 is mind-blowing. Meanwhile, SpaceX takes half a dozen tries before managing to do the same on a fully known environment on Earth.
That snipe was really unnecessary. Not to mention weird, considering how successful SpaceX has been at dominating the commercial launch sector.