Score
Title
82
AskScience Panel of Scientists XVIII
263
AskScience AMA Series: "I am Rhett Allain, physicist and technical consultant on Mythbusters and MacGyver. Ask me about the physics of pretty much anything!
393
Can dogs observe and recognize aging in adult humans? Do they differentiate between young adult, middle-aged and elderly humans?
10968
When does a mushroom die? When it's picked? When it's packaged? Refrigerated? Sliced? Digested?
30
Is it possible to transform martian soil into fertile soil through bacteria and fungi?
9
Do cats purr voluntarily or unvoluntarily?
12
What is the most amount of electrons forcibly added to an atom?
9
Why does the taste of tap water vary between locations?
51
Why do things like saliva or melted cheese pull into strings when you try to separate them?
3
Are seatbelt/phone detection cameras a real thing? And if so, how do they work?
26
I think I understand the difference between aleph-null and aleph-one as countable and uncountable infinities, but what is aleph-two?
10
If the vaporization point of water can be changed by increasing pressure, is the freezing point also affected by pressure?
7
Do any of the stars we can observe with tbe naked eye at night have planets orbiting them?
5743
Does a Mayfly, which only lives a day, evolve fast than a human?
6
The failed recovery of the Falcon Heavy's central core was attributed to the booster running out of TEA-TEB. How does this happen if the amount of fluid needed to ignite the engine, and the number of ignitions required is known beforehand?
5
How do we know what an asteroid is made of?
5
How do developers of Nuclear Weapons either keep (or protect themselves from) radioactive materials like Plutonium-239 from potentially ‘leaking’ out particles? Are there any methods to contain these particles from escaping the material so they won’t hurt biological matter near the material?
7
How does a "loop sensor" in a street work?
4
How far can the human eye see?
2
Could a spacecraft under constant acceleration ever reach near-lightspeed?
5
I've heard that catfish have ring shaped pupils, however this rather surprising adaptation is only ever mentioned in passing. Can anyone provide more information on this?
5
Why are the late derivatives of position so weirdly named?
6
We often see water used as a neutron moderator in fission reactors due to its high Hydrogen content. Would gaseous Hydrogen be a more effective neutron moderator?
3
Could a neutrino interact with a water molecule in my eye and release a photon that I could "see"?
0
Is the threshold frequency for alloys based on the elements in the alloy, or is it a different factor in the photoelectric effect?
23
Are mitochondria significantly different in different species?
12
When a Li-ion battery is first manufactured, is it already charged? If so, how much and why that amount?
1
How do power outages cause transient voltage spikes?
1
How did scientists choose the elements and method by which to create an atomic bomb?
0
What does hacking usually entail? How much of it is like the glamorous stuff we see on tv and how much is just calling and asking for a password?
13
If the four dimensions of space and time are intertwined, why can we not rotate an object into "time" the same way we can rotate an object in 3D space?
132
As a snake grows in length, does it grow additional ribs and vertebrae, or do they have a set number?
4
If an event happens an average of every x years, and it is been >x years since it last happened, are we more likely to experience the event? If so, can this likelihood be predicted?
0
Will checkpoint inhibitors (PD1/PD-L1, CTLA4) cause the host immune system to generate neutralizing antibodies?
6
Why does halorhodopsin only activate when exposed to yellow light and channelrhodopsin with blue light?
5
At an atomic level, what makes a material better at compression or tension?
30
Why isn't Boron created through normal stellar nucleosynthesis (i.e. nuclear fusion in stars)?
1
Are there any approximations for masses of the various continents of Earth?
44
What is special about sunlight versus artificial light that plants need it?
4
Do male species having lower life expectancy than female also occur in other animal species than human?
14
How much complexity can nuclear pasta phases in neutron stars support? Could one potentially have strong-force-based life in a neutron star?
29
Do other animals have 'accents' like humans do?
13 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.
11 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.
13 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.
11 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.
6 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.