Score
Title
9418
Megathread: 2017 Hurricane Season
24
Earthquake Megathread
6172
If a nuclear bomb went off in Boston harbor could scientists tell after the fact who had manufactured it, do they leave distinct radioactive signatures?
5747
Why aren't there any orbitals after s, p, d and f?
16
What do sexes in fungus mean?
135
Do black holes have electromagnetic field?
4
Where does the "blast" portion of a nuclear explosion come from?
6
Do atmospheric CO2 measurements include a significant diurnal cycle?
8
How do bionic arms work?
4
Historically, when large numbers of sailboats/ships had to travel in formation as a fleet, are there different dynamics governing the movement of ships in the front, middle and rear of the group?
6
Why are non-differentiable continuous functions integrable?
9
Are Toucans (Americas) and Hornbills (Asia/Africa) an example of convergent evolution?
4
What are the estimated thicknesses for northern sea-ice at the height of the Pleistocene glaciation, and how are those thicknesses estimated?
7
Ask Anything Wednesday - Physics, Astronomy, Earth and Planetary Science
2
Why are rainbows in an arc shape and does the radius change?
4
Why do nuclei release energy when they fuse?
24
How many layers are there in a modern integrated circuit?
8
Why does the Earth's rotation effect Rockets and not Planes?
2
Are there plant/animal somatic hybrids?
2
Would the opposite of codependency issues be considered as unhealthy as codependency? Wherein any form of dependency is abhorrent to the person in question? Does this have a clinical classification?
60
Do people that have degenerative diseases such as Alzheimer's lose their muscle memory as well?
20
How is it possible that something as large as a possible Planet 9 has completely evaded visual observation?
8154
There is a video on the Front Page about the Navy's Railgun being developed. What kind of energy, damage would these sort of rounds do?
8
Would global cooling create more land? If so, how much more land would be available before the whole earth freezes?
11
How did they measure hurricane wind speeds in the 1800's?
4125
In 1972 a woman fell 33,332 feet without dying. How is that possible?
12
How is it that scissors can curl ribbons?
12
What is happening at a molecular level when a knife cuts through nylon rope?
154
Could we railgun the Moon?
15
Why is caesium the largest atom? Shouldn't element 118 be the largest?
1
Why does your metabolism slow down with age?
7
Do snakes that can 'see' heat, such as ball pythons, compare their 'heat vision' with their normal vision?
17
[CHEMISTRY] How do chemical companies determine if one ingredient in a solution can be replaced by another?
2
In emergencies like on CDMX will using cellphone data on a very far state affect the capacity on CDMX cell towers to make calls and/or use cell phone data?
12
Can a human be allergic to any substance? As in, does every material have the potential to elicit an allergic response?
2
What defines an equation of state?
46
How is online gaming possible if there must be some delay?
5
Does my peripheral vision have a different latency than objects I look directly at?
15
Why is gold found in seams?
16
On an alien planet, would a regular compass still point true north?
11
Can someone with reading Aphasia "read" in Braille?
4
Would negative kelvin body always transfer heat to positive kelvin body?
14 Kenley Furthermore, it's conceivable that there were multiple origins of life early on, but the others didn't "make it." Perhaps, for whatever reason, they were less efficient at metabolism or reproduction than life-as-we-know-it, so they weren't able to get a foothold.
12 t_mo 'Possible' is a tricky word in origins biology. For Archae and Bacteria to have *no ancestor in common* would imply a profound level of convergence, a frequentist statistical probability approaching zero. At a certain point in development we have to start asking 'what does an ancestor actually look like', and we have to enter into a discussion of abiogenesis or some other theoretical origin point. We can't pinpoint specifics in the pre-cellular ancestors, and what that would actually look like depends on which perspective you take on likely biological origins. However, whatever we presume for the sake of discussion to be the pre-cellular ancestor of bacteria/archae, we know that it has a very limited number of forms and features. If those forms and features share so much in common (bound by membrane, pre-RNA features of replication, etc) we have to reconsider what the statement of 'two distinct ancestors' would look like even from a theoretical perspective, *could* they be sufficiently distinct while still sharing sufficient features to produce unicellular life as similar in form and function as archae/bacteria, or are we really just looking at two slightly different versions of the same replicating system? As with a lot of questions in origins biology, the discussion is mostly philosophical and not very practical.
6 Rather_Dashing All current life on earth came from a common ancestor. We know this because, among many other lines of evidence, we all have the same dna code (with some minor variation). For example the DNA codon 'TCT' codes for a Serine base. There are 64 different codons and they consistently code for the same amino acid bases across the kingdoms. The odds that two separate origins of life would come up with the same code is astronomically low. However if is possible, even likely, that life arose multiple times, but the other lines died out leaving all the life known today descending from a single ancestor.
2 rocketsocks Likely, in fact. And some of the earliest forms of life may have intermingled because they were so similar (if they weren't much more than just self-replicating RNA polymers, for example). However, at some point one form of life became advanced enough to outcompete all the others by a significant margin, and that became the "last universal common ancestor" (or LUCA) for all current life on Earth. It's possible that abiogenesis type events continue to occur on Earth today but aren't able to get a foothold on a planet with abundant life already. As far as we can tell all life on Earth has a common ancestor, however. We can be pretty certain of this due to the similarities in the core DNA -> RNA -> protein genetic coding pipeline. There is great similarity in the fundamental molecular machinery of all life. They share the same 3-nucleotide codon length, the translation table between codons -> amino acids is remarkably similar across species, the ribosomes, t-rnas, etc. which facilitate translation of RNA to amino acid sequences is also remarkably similar. There are far too many similarities in those core mechanisms to be due to either chance or convergent evolution, which points to a common evolutionary lineage between all life on Earth.
2 SweaterFish The evidence for a universal common ancestor of all current life on Earth is pretty convincing, but that doesn't rule out that there was also multiple origins. The common ancestor is not the same as the origin, it lived much, much later. Some theories of the origin of life suggest that different metabolisms or cellular components originated separately and would have been considered living and evolving on their own, but were adopted over time into a single, more flexible or efficient mosaic organism that was our common ancestor.
1 [deleted] [removed]
1 JereRB I saw a show once. Said that life not only happened, but has happened multiple times. Things in the past happened that killed literally everything: asteroids cracked the crust, worldwide volcanic eruptions, etc. Life happened after and between each one. So could it have happened in multiple locations way back when it first became possible after the latest cataclysm? Given that life seems to occur as soon as environmental conditions allow, it's very possible, if not highly likely. The fact that everything alive now shares a common ancestor just means that those other organisms met our forebears...and lost.
-1 chodumadan that carbon is the base of life on earth could be due to environmental factors like temperature. if the temperature were different - like it is on other planets - it is possible that some other element would be the base of life.
14 0 Kenley Furthermore, it's conceivable that there were multiple origins of life early on, but the others didn't "make it." Perhaps, for whatever reason, they were less efficient at metabolism or reproduction than life-as-we-know-it, so they weren't able to get a foothold.
13 0 t_mo 'Possible' is a tricky word in origins biology. For Archae and Bacteria to have *no ancestor in common* would imply a profound level of convergence, a frequentist statistical probability approaching zero. At a certain point in development we have to start asking 'what does an ancestor actually look like', and we have to enter into a discussion of abiogenesis or some other theoretical origin point. We can't pinpoint specifics in the pre-cellular ancestors, and what that would actually look like depends on which perspective you take on likely biological origins. However, whatever we presume for the sake of discussion to be the pre-cellular ancestor of bacteria/archae, we know that it has a very limited number of forms and features. If those forms and features share so much in common (bound by membrane, pre-RNA features of replication, etc) we have to reconsider what the statement of 'two distinct ancestors' would look like even from a theoretical perspective, *could* they be sufficiently distinct while still sharing sufficient features to produce unicellular life as similar in form and function as archae/bacteria, or are we really just looking at two slightly different versions of the same replicating system? As with a lot of questions in origins biology, the discussion is mostly philosophical and not very practical.
5 0 Rather_Dashing All current life on earth came from a common ancestor. We know this because, among many other lines of evidence, we all have the same dna code (with some minor variation). For example the DNA codon 'TCT' codes for a Serine base. There are 64 different codons and they consistently code for the same amino acid bases across the kingdoms. The odds that two separate origins of life would come up with the same code is astronomically low. However if is possible, even likely, that life arose multiple times, but the other lines died out leaving all the life known today descending from a single ancestor.
2 0 rocketsocks Likely, in fact. And some of the earliest forms of life may have intermingled because they were so similar (if they weren't much more than just self-replicating RNA polymers, for example). However, at some point one form of life became advanced enough to outcompete all the others by a significant margin, and that became the "last universal common ancestor" (or LUCA) for all current life on Earth. It's possible that abiogenesis type events continue to occur on Earth today but aren't able to get a foothold on a planet with abundant life already. As far as we can tell all life on Earth has a common ancestor, however. We can be pretty certain of this due to the similarities in the core DNA -> RNA -> protein genetic coding pipeline. There is great similarity in the fundamental molecular machinery of all life. They share the same 3-nucleotide codon length, the translation table between codons -> amino acids is remarkably similar across species, the ribosomes, t-rnas, etc. which facilitate translation of RNA to amino acid sequences is also remarkably similar. There are far too many similarities in those core mechanisms to be due to either chance or convergent evolution, which points to a common evolutionary lineage between all life on Earth.
2 0 SweaterFish The evidence for a universal common ancestor of all current life on Earth is pretty convincing, but that doesn't rule out that there was also multiple origins. The common ancestor is not the same as the origin, it lived much, much later. Some theories of the origin of life suggest that different metabolisms or cellular components originated separately and would have been considered living and evolving on their own, but were adopted over time into a single, more flexible or efficient mosaic organism that was our common ancestor.
1 0 [deleted] [removed]
1 0 JereRB I saw a show once. Said that life not only happened, but has happened multiple times. Things in the past happened that killed literally everything: asteroids cracked the crust, worldwide volcanic eruptions, etc. Life happened after and between each one. So could it have happened in multiple locations way back when it first became possible after the latest cataclysm? Given that life seems to occur as soon as environmental conditions allow, it's very possible, if not highly likely. The fact that everything alive now shares a common ancestor just means that those other organisms met our forebears...and lost.
-1 0 chodumadan that carbon is the base of life on earth could be due to environmental factors like temperature. if the temperature were different - like it is on other planets - it is possible that some other element would be the base of life.