Coffee House Musing

This trend in astronomy is just a minor corollary in what has now become known round the world as the Percy Postulate: eventually all jobs will be programming jobs. Even my coffee cup is programmable and has an app now: --Percy

Naw, everything's compatible, it's no problem, or at least it wasn't until the coffee cup got snippy after I used it for ramen noodles.Fortunately there are manual overrides, but they're in the Matrix guarded by my toaster which hasn't let me pass since I tried to use it to warm up a fried egg. --Percy

This has been explained previously, but once again, the term dark energy arose as a placeholder label for the cause of the accelerating expansion of the universe, which was discovered through observational evidence. Other than the observational evidence of its effects, nothing is known of dark energy. It might be a constant energy pervading all space, or it might vary across time and space, or it might be something else. We don't know at this time.The specific observational evidence and subsequent analysis demonstrating the likelihood of an accelerating expansion of the universe originally came from two studies, the High-Z Supernova Search Team and the Supernova Cosmology Project. There are no assumptions. What are you referring to?*You will have no trouble finding sites on the Internet challenging absolutely anything. Don't believe in a spherical Earth, just go here: The Flat Earth Society. Don't believe in the moon landings, just go here: Astronauts Gone Wild. Don't believe airplanes brought down the World Trade Center, just go here: 9/11 Conspiracy Theories. Don't believe Lee Harvey Oswald short JFK, just go here: John F. Kennedy Assassination Conspiracy Theories.And last but not least, if you don't believe in dark energy, just go here: It’s Over: Dark Energy Was Fake Science – CEH--PercyABE: *After seeing AZPaul3's Message 42 I realized that LamarkNewAge might be referring to the assumption that the accelerating expansion we observe at great distances is also taking place locally.Edited by Percy, : AbE.

Calling the cosmological principle (the idea that on large scales the universe has the same properties for all observers) purely assumptive might be an example of an overabundance of scientific caution because we have more than zero evidence. When we compare our local large scale region with remote large scale regions, they appear approximately the same. This means these other large scale regions that we observe are also approximately the same as each other.It's also consistent with what we observe on small scales, meaning that the physical laws we observe being followed locally are also being followed in all space that we observe. The structure of the universe on large scales is a reflection of all matter and energy following the same laws on tiny scales. For example, if the cosmological constant were different in the direction of Draco, that fact would stand out starkly when compared to observations made in the direction of Crux.Science couldn't make progress if we insisted on hyperskepticality and held that, for example, just because the triple point of water is 0.01°C on one side of room, we can't assume that it will still be 0.01°C on the other side of the room.Also, what would be the quality of our thinking if we abandoned generalization, concluding that because the triple point of water is 0.01°C everywhere we've measured it that therefore the triple point of water is 0.01°C everywhere. There's no denying the satisfaction of proving something true, but that kind of certainty is denied science. The best we can do is increase our confidence, but enough observations can make us very confident.So sure, on a didactic level the cosmological principle may be an assumption, but it's a damn good one, and one that if it is false it is only, at least by current measurements, in very subtle ways that we haven't yet found.--PercyEdited by Percy, : Grammar.

Replied in error.Edited by Percy, : No reason given.

For some people more information leads to more questions, for others more confusion. For this context they are directions looking outward from Earth, not places. No, I didn't say that. Sure thing. Yeah, that's it, everyone's playing bait and switch with you, your comprehension is perfect. Again, in this context, the stars of these constellations are used to indicate direction, not location. The particular locations of the stars that make up Crux and Draco are of no consequence. I chose these constellations simply because they are in approximately opposite directions so I could refer to regions of space as far from one another as possible. Just because you're paranoid doesn't mean everyone's not out to get you. The focus of my post was the cosmological principle, not dark energy. Yes, but I just chose something fundamental at random. A better choice might have been Planck's constant. I don't know enough about the cosmological constant to be sure that a different value would result in different physical laws, which is why Planck's constant might have been a better choice, since I'm pretty sure if it had a different value then our physical laws would also be different. No. Aye aye, sir.--Percy

I would urge posters here to avoid implying dishonest behavior.--Percy

The June, 2021, issue of Scientific American contained an article about protecting the Earth from asteroids and comets: https://www.scientificamerican.com/...t-earth-from-asteroids A central focus was the loss of the Arecibo radio telescope, our best detector of asteroids and comets this past December. The current goal is to find 90% of objects larger than 140 meters. A 20-meter asteroid exploded above Chelyabinsk Oblast in Russia in 2013, causing damage to buildings and many injuries due to broken glass and falling objects. There were no deaths.The article mentions a number of methods for defense against asteroids or comets whose orbit will intersect ours at some future point, deflection receiving the most attention. Some of these you already mentioned:

• Gravity tractor. Park a very heavy spacecraft next to it for years, gradually changing its orbit. The article says this approach won't be available for a century of two but doesn't say why. It seems the simplest technologically. The only reason I could guess is the difficulty of lifting a heavy enough spacecraft into space, but that doesn't make sense either, because the spacecraft could be lifted into Earth orbit by multiple launches and assembled in space. Or we could park many lighter spacecraft near the asteroid/comet instead one heavy one.
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• Vaporize material on the asteroid's surface causing it to push off into space and exerting a force on the asteroid/comet. This could be done by lasers or by mirrors deflecting the suns light or by painting a large part of the surface a dark color so it absorbs more heat from the sun.
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• Slam a spacecraft into it, deflecting it off course.
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• Nuclear blast. This is sufficiently violent that it introduces the possibility of break up into smaller pieces.

These solutions have a common problem: they require years of lead time. This article doesn't mention the PI possibility of Lubin and Cohen, but here's a link to the Lubin/Cohen article that appeared in Scientific American a week ago: Planetary Defense Is Good--but Is Planetary Offense Better? - Scientific American It claims the lead time for launch need only be hours for a small asteroid/comet and days for a larger one. The resulting "house-sized pieces" seem approximately the size of the Chelyabinsk meteor that caused so much damage and injury (though percentage-wise the damage and injury was very minor since it's a large population center of over a million), but that's still a much better outcome than the 50 meter asteroid that hit Tunguska back in 1908 which would likely have been catastrophic for the modern Chelyabinsk and killed at least thousands.--Percy

I do like the deflection approaches best because they leave the meteor/comet intact. Any breakup approach that leaves behind 50 meter fragments instead of 20 meter fragments ("Sorry to report that there was an undetected vein of weaker material running through the asteroid that caused breakup along different planes than originally planned.") that remain on the same course means we could get multiple catastrophic hits.--Percy

We also need to watch out for false prophets who claim that God and Jesus are real and that life can only be properly lived by obedience to a book.--Percy

Neat! The first thing I did was cover up the arrows, which as the article later points out makes no difference. The brain is not following cues from the arrows. I then started covering up the circles themselves a little at a time - the illusion persists even when much of the circles aren't visible. For me the illusion disappeared in the circle on the left when around 50% was covered up, while the illusion persisted in the circle on the right even after most of it was covered. The illusion does not require two circles - covering one of them up completely does not diminish the illusion in the remaining circle.--Percy

I suppose the medium-sized infrared dot is out of the question since we're on the other side of the sunshade. A question occurs to me: Obviously the sunshade doesn't interfere with communications, but did communications influence decisions about the sunshade?--Percy

No, you got it. I was wondering about the sunshade's effects on electromagnetic radiation (radio waves), things like the material used, reflectivity, absorption, density, did it have to be placed at an angle, is it flat or does it have a very specific topography, did its presence affect choice of communication frequencies, etc.--Percy

I wonder if the James Webb Space Telescope deserves its own topic. It was often mentioned in this thread. Here's a recent image of the Pillars of Creation: Wow!--Percy

He might also want to try not being so error prone. From Highest number counted out loud | Guinness World Records:

quote:

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In 2007 Jeremy Harper, of Birmingham, Alabama, verbally counted every number up to a million, in a series of live internet broadcasts spanning four months – highlights of which are still available on YouTube (Bitly | Page Not Found | 404). Starting on 18 June 2007, he counted for approximately 16 hours a day, finally reaching one million on 14 September that year – a total duration of 89 days, and averaging just over 11,200 numbers per day.

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--Percy