81–90 of 279 posts
Is this the same collision theorized to have created the moon?
Earlier quoted context omitted.
The thing is that even for a super low probability event, the size of the universe is so huge and such events must be happening all the time. e.g. Say chance of a random planet ever being hit by a water-carrying comet is one in a billion, then with 100B - 1T planets in the milky way it'd happen here 100-1000 times. If chances are only one in a trillion, and we're the one in the milky way, then there are still another…
Do other galaxies matter here? A civilization would need to be incredibly powerful to be detectable from another galaxy.
The article says the light elements hydrogen, carbon and sulfur (and oxygen?) were only able to condense on the outer planets (and their moons). And the original article specifically says "the inner Solar System planets Venus and Mercury are largely devoid of volatile elements". If that's the case, why does Venus have so much carbon dioxide? (I'm not saying the article is wrong, just trying to understand.)
Venus doesn't have liquid water, which is needed for the reaction of silicates with CO2 ("weathering"). Without that reaction, CO2 just accumulates in the atmosphere. Most of the carbon on Earth (and there's a lot) is locked up in rocks.
There's also a biological effect. Here on Earth, silica in the ocean is scrubbed out by microorganisms that create silica shells; these tiny shells fall out into sediments, where (in deep ocean) they eventually form a kind of biogenic rock called "chert". Elsewhere, typically in shallow water, carbonate rocks are formed from the remains of other kinds of animals. Without these effects, the dissolved silicon concentration in seawater would be orders of magnitude higher, and the silica would react to form clays. This reaction would acidify the ocean and prevent carbonate formation.
Just such "reverse weathering" has been hypothesized to occur after the Permian-Triassic boundary, where CO2 levels stayed elevated for 5 million years. The extinction event was so severe it disrupted chert formation (a "chert gap").
Earlier quoted context omitted.
The equation itself makes no assumptions. But anyone trying to calculate something with it must. The last five factors in the equation will be filled in by assumptions based entirely on one data point, life on Earth. From your link: ne = the average number of planets that can potentially support life per star that has planets. fl = the fraction of planets that could support life that actually develop life at some poi…
Thanks, I read that part before I shared it. It's pretty clear to me, these are pretty well defined quantities, just hard to measure. What is unclear is perhaps the definition of life. But at no point does it assume a planet must be in the Goldilocks zone. So perhaps you want to point out those assumptions you are talking about to me, because I don't see them. Edit: the parent post has been edited substantially after…
They are "defined" conceptually, in words, not in physical quantities. It assumes we can assign a known value to any of that when we don't and likely never will. It's like saying "Let X answer the unanswerable question. X is the answer".
> at no point does it assume a planet must be in the Goldilocks zone
You could say it implies it with fl.
> Edit: the parent post has been edited substantially after I replied.
Only for legibility.
Earlier quoted context omitted.
Do other galaxies matter here? A civilization would need to be incredibly powerful to be detectable from another galaxy.
Galactic colonization, carried to saturation, would detectably modify the appearance of a galaxy. So called "type 3 civilizations" would convert a significant fraction of starlight to lower grade heat, which would be radiated. Searches have been conducted for this signature, with the result that no more than 1 in 100,000 galaxies has such a civilization, and with the result being consistent with none.
What’s the probability that a radio-capable civilization becomes a galactic type 3 one? Looking at the only example we have, it appears very unlikely. It seems much more probable that we’ll destroy ourselves within the next centuries.
This could mean in the Drake equation ne -number of planets capable of life- is very small. A planet has to be hit with a comet big enough to deliver a large amount of water but not so big or fast to destroy it. And be in the Goldilocks zone of the star. Also the mass of the planet would play a part - gravity of more massive ones would be more likely to capture a comet. But again, too massive and I could see that ham…
Earlier quoted context omitted.
The thing is that even for a super low probability event, the size of the universe is so huge and such events must be happening all the time. e.g. Say chance of a random planet ever being hit by a water-carrying comet is one in a billion, then with 100B - 1T planets in the milky way it'd happen here 100-1000 times. If chances are only one in a trillion, and we're the one in the milky way, then there are still another…
Do other galaxies matter here? A civilization would need to be incredibly powerful to be detectable from another galaxy.
In either case it's a statistical question of how common is life, and intelligent life, but of course there's the human interest in potential contact with another intelligent life form.
How Earth Got Its Water: A Cosmic Detective Story
The Big Question: How did Earth become a planet with oceans and life, when it formed so close to the hot Sun?
What Scientists Did:
- They used a "radioactive clock" made from two elements: manganese and chromium - Manganese-53 breaks down into chromium-53 over time (like ice melting at a steady rate) - By measuring these elements in meteorites and Earth rocks, they figured out WHEN Earth's basic chemistry was locked in
Key Finding: Earth's chemical recipe was set within just 3 million years after the Solar System formed (that's super fast in space terms!)
The Problem: At that point, early Earth was missing the ingredients for life—especially water, carbon, and other "volatile elements" (stuff that evaporates easily when hot)
Why Earth Was Dry: Close to the Sun, it was too hot for water and other volatile stuff to stick to the rocks that built Earth—they stayed as gas and floated away
The Solution: About 70 million years later, another planet called Theia (which formed farther from the Sun where it was cooler) crashed into Earth:
This collision created our Moon It also delivered water and other life-essential ingredients to Earth
The Big Takeaway: Earth needed a cosmic accident to become livable. Without that lucky collision bringing water from the outer Solar System, we wouldn't be here!
Why This Matters: If Earth needed such specific, lucky events to support life, habitable planets like ours might be much rarer in the universe than we thought.
Earlier quoted context omitted.
Your assumption we need water for life to exist is in my opinion wrong. We only know Earth so assume that is what is needed for life to exist.
There's a reason life is carbon-based, and it's not random. It's the only element that works, due to abundance; ability to form many bonds; bonds that are just durable enough but not too durable. There's plenty of sci-fi about silicon-based life, but that's infeasible fantasy. And no other elements have any hope. If you have carbon-based life, you need water as solvent and medium. It's a pretty safe assumption that a…
Well, the thing is that all of those are environment-dependent.
We do have data on a somewhat diverse set of environments, and it's enough to confirm what we knew about the flexibility of carbon. But it's not enough to disprove the alternatives.