Astronomy & Space Exploration
- Thread starter MrMarcello
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Should have probably added this video in the previous post itself — here's a talk by the co-author, Thomas Hertog:
https://arxiv.org/abs/1707.07702
The case against dark matter
Erik Verlinde’s theory of emergent gravity is proof that not all physicists believe dark matter is necessary to explain the cosmos.
http://astronomy.com/news/2018/05/the-case-against-dark-matter
Erik Verlinde’s theory of emergent gravity is proof that not all physicists believe dark matter is necessary to explain the cosmos.
http://astronomy.com/news/2018/05/the-case-against-dark-matter
Very interesting. Never thought about it as an emergent property much like temperature is an emergent property of moving particles.
It definitely sounds like a novel solution. But we'll have to see what further research turns up.
Can hardly see things in any sort of detail on the tweety picture (not even the more prominent arms), and I don't feel inclined to pay for the poster...
This NatGeo one should do for the time being:
Cost-free!
P.S. This Pinterest gallery is quite good for basic astronomy posters.
Amazing how insignificant we are.
http://nautil.us/blog/-forget-earth_likewell-first-find-aliens-on-eyeball-planets
Forget “Earth-Like”—We’ll First Find Aliens on Eyeball Planets
Forget “Earth-Like”—We’ll First Find Aliens on Eyeball Planets
If you can find a link or stream or have hbo.go, VICE's episode on "Printing Tomorrow & Are We Alone?" was fantastic. Here's a preview clip.
https://news.vice.com/en_us/article...os-episode-printing-tomorrow-and-are-we-alone
https://news.vice.com/en_us/article...os-episode-printing-tomorrow-and-are-we-alone
"The number of possible life-hosting planets is quickly growing as space travel technology improves and probes go deeper into the galaxy"
That's news to me!
Speak for yourself.
Well we are.
Think it's fairly unlikely that tidal locked planets are great places to find life. The one thing you can say about earth is it has a very cyclic environment.
Summer, autumn, winter, spring, repeat.
Morning, mid-day, evening, night, repeat.
28 day lunar cycle
800,000 Milankovitch cycle (cycle in earth's orbit)
Why would a cyclic environment be beneficial? Surely that just leads to a greater chance of boiling the water off or freezing it all solid. Well we want the "life area" (whether that's in a deep ocean or on the surface) to be in the Goldilocks region, but that only needs to be an average. The system will always lag behind the extremes (hottest temperatures on earth tend to be after the longest days, a greenhouse with a water tank will be cooler in day and warmer at night).
But importantly you give life a chance to experience a variety of environments. Ice age - no problem. Desert conditions - no problem. But even more importantly it slows the change and gives life a chance to react.
Imagine a tidally locked planet with a Goldilocks zone. No night, no day, no winter, no summer (actually it could have those but let's assume not for a second). let's say it does have liquid water at its solar horizon - a thin strip of life whilst the rest of the planet burns and freezes. And changes to that planet and suddenly the thin strip of life dies.
However - Where I do think life will be very common is in moons on hot Jupiter's around red dwarfs.
You have the Hot Jupiter's cycle of the star, the moons cycle of the Jupiter. We know from the moons of Jupiter and Saturn that liquid oceans are incredibly common. We know from the study of exoplanets that Jupiter like planets are everywhere. And we know these larger Jupiter planets have more moons. And if panspermia is a real phenomenon, then it will happen with these close moons and gyzers ejecting life into space.
And such an idea is consistent with the Fermi paradox. If there is one thing these moons are unlikely to have, it's a substantial atmosphere. Would it be possible for an intelligent species to become space faring without an atmosphere? I.e. could a dolphin become space faring? Even with another billion years of evolution?
God has spoken to me. He said, "I made it all for you, mate!"
Flipper was learning to fly in one episode but they canceled the show.
You may be right about the Hot Jupiter moons, but we shouldn't underestimate the adaptability of life. Most bacterial life on our own world is found beneath the surface in the Earth's crust - although very little in 'waterless' environments such as dry deserts and the Antarctic.
Your point about the precariousness of life on an eyeball planet is hard to dispute. A tightrope walk with fire on one side and a deep freeze on the other.
Exactly. And I think the thing I'm not explaining well is, where you have a whole planet that is tuned to the right conditions, it takes *a lot* to move the average temperature one way or another. (Imagine how much energy is needed to increase the temperature of the sea by 10 *C)
But where you have only this narrow band, it will take far less energy to increase whatever water there is by 100's of degrees because there will be far less of it.
This is awesome and more evidence of panspermia.
And this is more evidence against the fictional Fermi Paradox
Those twats from Alpha always one upping us.
Fictional?
How, though? The Fermi Paradox merely posits “where is life?” Even though it has been bastardized over the years (most notably by Michael Hart - who had nothing to do with Fermi), the original hearsay inquiry is just: where...and...why aren't we seeing intelligent life around us when the galaxy and the cosmos should be teeming with it according to Fermi's rough calculations...
https://www.osti.gov/accomplishments/documents/fullText/ACC0055.pdf
There can be no evidence against the supposed Paradox because he wasn't really arguing anything...he was just genuinely puzzled why we haven't come across extraterrestrials life — and followed that up with some intuitive, offhanded, explanations.
To be fair the permit paradox isn't really a paradox. There is a rational explanation behind the lack of visible aliens, despite stars and planets being everywhere for billions of years.
Whether that explanation is life is rare (yes) or aliens are weird (yes) or something else (yes)
But from our perspective it is paradoxical so I think calling it fictitious is a bit flawed
Whether that explanation is life is rare (yes) or aliens are weird (yes) or something else (yes)
But from our perspective it is paradoxical so I think calling it fictitious is a bit flawed
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@rcoobc got hit with the autocorrect paradox it appears.
How, though? The Fermi Paradox merely posits “where is life?” Even though it has been bastardized over the years (most notably by Michael Hart - who had nothing to do with Fermi), the original hearsay inquiry is just: where...and...why aren't we seeing intelligent life around us when the galaxy and the cosmos should be teeming with it according to Fermi's rough calculations...
https://www.osti.gov/accomplishments/documents/fullText/ACC0055.pdf
There can be no evidence against the supposed Paradox because he wasn't really arguing anything...he was just genuinely puzzled why we haven't come across extraterrestrials life — and followed that up with some intuitive, offhanded, explanations.
Its been put forth as a stronger argument by people like Kurzweil and some others I knew in Uni. And it carries the name "Fermi Paradox" so I am talking about proponents of that live of beliefs more than the beliefs of Fermi as an individual. Its used by people like Kurzweil to almost assert that humans *are* the most intelligent form of life in the universe. Which is why work like Liu Cixin is so important because it quite clearly lays out how that entire line of thinking is illogical.
Someone should have asked Fermi "Why would you even assume we should be able to detect life in such a vast universe?"
Life can have evolved far beyond our current crude means of detection (we are ants solution), life can be too far away for us to detect it(vastness solution), life can be completely different than we assume and trying to communicate with us but we don't understand how yet (diversity solution), life can have moved beyond our single galaxy (not local solution), they are intentionally monitoring us and not interfering (star trek solution) and most powerfully from a game theory perspective it is actually illogical for intelligent life to broadcast and reveal itself (the Dark Forest solution). I think I am even missing a few but the Dark Forest is one of the most interesting and obvious solutions.
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Dark Forest solutions makes a lot of sense, but if the life has evolved in different ways, then you can expect that there are many groups of aliens who are actually sending signals, despite that it makes no sense. Sure, many more have isolated themselves, but why should all of them do so especially considering that alien civilizations should be very different to each other. Then there should be the explorator types of civilizations which just want to explore.
I don't think that you can assume that the life is so diverse, and then intelligent civilizations would behave the same, as in don't send signals, don't explore, hide yourself in fear of predator civilizations.
isn't that exactly what we did? Are you saying we are not intelligent life?
That's where the Star Trek and the Vastness solutions come into play. We might be in the complete rural wasteland of the universe and no one really cares about our little corner that much.
When I look at some of those Hubble Deep Field pictures, of hundreds of thousands-millions of galaxies so far away they are almost just specks to our most powerful telescopes I just think the universe is really much more vast than we really comprehend ya know?
Yes, in hindsight that was pretty stupid. We have to hope there aren't any more of those cigar shaped asteroids headed our way
https://www.mnn.com/earth-matters/s...steroid-another-star-and-unlike-anything-seen
Yep, we did that which in my opinion has been an idiotic thing to do. But it is a good example, that not ever intelligent civilization needs to be a rational civilization (by rational, I mean in game theory sense of rational).
Indeed. There are multiple reasons of 'why no one is there'. And we're not even sure that no-one has visited Earth in the first place. And let's not forget that we are capable of detecting radiowaves for less than a century, and have been a civilization for just ten thousand years.
That's a great point about time as well. For the universe the time we have been aware is so short. On the scale of the universe, it would be like glancing at a park from 50 meters away for 1 second, not noticing any movement and then concluding there was no life in the park.
Time is perhaps the biggest factor. Our system may have been discovered by other intelligent life long before we were here, and may be discovered long after we're gone. That time lapse between the two being so so miniscule in universal terms, but more than enough for life to begin, evolve and cease.
And the same from our perspective when we look for other life. Fascinating and disturbing in equal measure!
I got you, mate, and agree with most of what you said here, but that specific Fermi Paradox bit really brought out the pedant in me — poor Enrico's original inquiry was quite innocuous and was made in a light way in the company of colleagues and acquaintances, but a subsequent conveyor belt of pompous skeptics has transformed it into a demented hydra with the addition of increasingly cynical interpretations — including the likes of Kurzweil: who have put their own slant on things to justify their personal stance.
In terms of the solutions, the most straightforward argument is the minuscule scale of humanity's genuine cosmic observation...Reber's radio telescope is just over 80 years old, Project Ozama is less than 60 years old — that translates to only about ~85 and ~50 G-type stars from Sol, so our radio field of vision, and sample size and scope, is infinitesimally small, thus far. If the galaxy alone is equated to planet Earth, it's like we haven't even trained our sights beyond the first couple of steps. And that's with the consideration that any directed signals are being sent within the electromagnetic spectrum: heavily attenuated (on top of being time delayed because of expansion). Quite like the rather far-fetched Zoo/StarTrek hypothesis as well — mostly because it's the most palatable, and even a tad bit reassuring in that a Cosmic-scale U.N. is stopping extraterrestrial contact by decree of benign universal overlords. Not a fan of the Liu Cixin and Dark Forest, though — agreeable as a thought experiment, but for the most part it just paints the “aliens” with a uniform brush as massive, unadventurous, wusses — too paralyzed by the potential of existential threats to venture beyond their immediate vicinity, technological capability notwithstanding — dunno, just seems very counter-intuitive, lacking in je ne sais quoi, and unambitious.