michael_w_busch

michael_w_busch, 1 month ago

@elizabethtasker It seems like there should be a "return to asteroid sample" joke here somewhere.

michael_w_busch, 1 month ago

@bruces @nyrath I see you have learned about the peculiar habit of Chandra Wickramasinghe's group.

They will apparently claim that anything and everything that evolved on Earth came from space; from octopoids to diatoms to prions to SARS-CoV-2.

(Wickramasinghe has been doing this since the 1980s, when he and Fred Hoyle claimed that HIV came from space).

michael_w_busch, 1 month ago

@w7voa @nyrath The motivation for the proposed local lunar time standard is navigation.

Previous studies have looked at directly extending GPS navigation to 1 lunar distance; and obtain absolute navigation precision of ±4 m or so (e.g. https://ntrs.nasa.gov/api/citations/20190002311/downloads/20190002311.pdf ).

Relative range measurements can be accurate to < 1 cm.

A new time standard would mostly be a matter of making the accounting easier.

michael_w_busch, 1 month ago

@elizabethtasker The particularly American experience of thinking that that is not so bad.

Over here, the public service announcements for everyone from high school on up are "Run, Hide, Fight"...

michael_w_busch, 1 month ago

@nyrath That arXiv posting is by John Gertz the television producer, who keeps writing pieces that do not reflect how SETI works in terms of the relevant physics or human politics.

For example; Gertz neglects things like this; first negotiated by the IAA 35 years ago and updated a few times since:

"Declaration of Principles Concerning Activities Following the Detection of Extraterrestrial Intelligence" - https://iaaspace.org/wp-content/uploads/iaa/Scientific%20Activity/setideclaration.pdf

michael_w_busch, 1 month ago

@nyrath For an example of John Gertz' writing not reflecting how SETI works in terms of the relevant physics:

In 2016; Gertz wrote an opinion piece opposing METI. As part of that, he also said asteroid radar observations should turn off our beam whenever it would pass across a star - https://arxiv.org/ftp/arxiv/papers/1605/1605.05663.pdf .

That is not possible. At the ranges at which the beams from planetary radars might be detected by equivalent telescopes; they are tens of lightyears wide with many stars in them.

michael_w_busch, 1 month ago

@mekkaokereke Having ridden the train over the Danyang-Kunshan Bridge, which is really a viaduct:

This does not seem like a good comparison?

The longest stretch of the Danyang-Kunshan over water is 9 km over Yangcheng Lake outside of Suzhou; where it is supported by thousands of pilings.

And re. that last bit:

Nobody is sailing container ships near it. Yangcheng Lake is 2 meters deep.

michael_w_busch, 1 month ago

@nyrath I am now reminded of when Daft Punk decided to do space opera anime: https://www.youtube.com/watch?v=dKJfJMMsqX4

michael_w_busch, 2 months ago

@tkinias @nyrath Phil has previously advocated building landing pads on the Moon by binding the regolith together by various methods: https://arxiv.org/ftp/arxiv/papers/2205/2205.00378.pdf .

To avoid throwing dust around.

All of this becomes less necessary on a planet with any sort of atmosphere.

michael_w_busch, 2 months ago

@tkinias @nyrath The Moon's lack of atmosphere means that small dust grains, which can get accelerated to very high speed by an exhaust plume, do not slow down (given that they are high enough up that the grains are no longer colliding much with each other).

So they can both travel a very long way and potentially cause a lot of damage to sensitive things like solar panels and spacesuits if they hit them.

michael_w_busch, 1 month ago

@tkinias @nyrath For Mars surface pressure & gravity; impact depth for a 1-mm dust grain is about 100 meters. Far more than Earth, where it is only a few meters. But sandblasting the surroundings is way less of a problem than in vacuum.

michael_w_busch, 1 month ago

@tkinias @nyrath For a first approximation of the scale over which particles stop acting like projectiles and start moving with an atmosphere; you can go all the way back to Newton:

Impact depth = diameter * density of particle / density of atmosphere .

The details get complicated. Per the papers linked above.

michael_w_busch, 1 month ago

@nyrath @tkinias Here I will invoke Dr. Busch.

Although I am usually working with much smaller collections of regolith in vacuum.

michael_w_busch, 1 month ago

@tkinias @nyrath If I use "Dr." or "Mr." depends on context.

Astronomy and planetary science? Doctor.

Anything related to healthcare? Mister.

Because I have been confused for my cousin the hematologist before; which was a bit awkward.

michael_w_busch, 1 month ago

@cstross @n1vux @tkinias @RogerBW @Sevoris @nyrath Microwave lasers can get up to about 50% efficiency with resonant cavity vacuum tubes; which are extremely annoying to work with. But that still means sinking as much waste heat as the power going out.

Which some people who still promote beamed solar power as a replacement for panels on the ground are pleased to not acknowledge.

michael_w_busch, 1 month ago

@RogerBW @cstross @n1vux @tkinias @Sevoris @nyrath From @NuclearAnthro , I learned the phrase "a great example of a horrible idea".

For many different reasons.

michael_w_busch, 2 months ago

@nyrath @rr4idic The cover art on David Oberhaus' book is from the 1999 Cosmic Call message, which Yvan Dutil and Stéphane Dumas reused in 2003, working with Sasha Zaitsev at the RT-70.

The book covers all of the usual suspects for proposed SETI message designs.

I concede the quad and octal encoded texts I put together for the Test Message game (and have reused on request a couple of other times) are not as photogenic. I designed them that way.

michael_w_busch, 2 months ago

@ZachWeinersmith I would suggest separating out smartphones from discussions about social media.

I make this point because the editors for my local newspaper keep running "no phones for kids in school, ever!!" opinion pieces entirely uncritically; without engaging with the reasons kids may absolutely need their phones.

Ranging from "can navigate taking public transit on their own" to "can quietly text for help in whatever situation" to "uses their phone to manage their artificial pancreas".