Score
Title
9439
Megathread: 2017 Hurricane Season
47
Earthquake Megathread
5027
Nutrition Facts: Why is sodium listed instead of salt?
5
If NASA's mission to Mars is successful, will Mars become American Territory?
6
How heavy is fire? If something catches on fire is it heavier or lighter?
9952
Duck fat melts at 57 degrees Fahrenheit. So on a 90 degree day, is a living duck's fat just... sloshing around?
15
How does deodorant work?
15
What gas is inside of unopened peppers? Or is it just air?
6
How much Asteroid mining/extra mass until it has an impact on earth's orbit?
1
What is a kilowatt hour, and why do electric companies charge based on this instead of kilowatts?
4
Why is drinking milk after spicy foods better than drinking water?
192
If natural fruit juices contain large amounts of sugar, why do we only seem to refine sugars from a select few plants (sugarcane, sugar beets) instead of from fruits in general?
152
What have we learned from Cassini's dive into Saturn so far?
78
Why do hospitals have heart clinics specifically for Women? Aren't all hearts the same?
279
How does computer memory work when the computer is turned off?
45
Do ape's toenails grow slower than their fingernails, like humans?
8399
What have been the implications/significance of finding the Higgs Boson particle?
1
If we want to colonise mars, why don't we colonise it first with Cyanobacteria and then plants in order to create a habitable atmosphere?
97
Can microwaves work without using water molecules to heat up food?
7
Why does the fourth power show up in the Stefan–Boltzmann law?
7
When I scratch a piece of metal, do small amounts of atoms break off from it?
5
Do lactose intolerant people absorb the same amount of calories from milk as regular people?
3
What has kept land animals from evolving to enormous sizes, i.e. the size of a mountain?
14
How do they prevent the ISS from crashing into satellites and space junk?
29
Do small songbirds - a finch, say - ever get stung by bees/ wasps? If so, is it typically fatal?
45
It's been about 5 years since the Mochizuki's ABC Conjecture proof was originally published. What's its current status?
1
How do vaccines fail?
8
Does Quinine glow even after you remove it from a black light?
7
Can we forecast the northern and/or southern lights?
240
On a planet with more than 1 sun, what would a rainbow look like?
6
What can layers and swrils in rock indicate?
5
How do insects protect their eyes from direct sunlight?
4
Why can't you count the number of things touching you in a certain spot?
216
We are carbon based life forms, however, is it possible for life to be based off another element?
124
Is there a maximum size for a raindrop?
6
In a coronary bypass surgery, why do doctors use veins instead of arteries? Is there an advantage to this?
2110
Are there any challenges for parasites living in animal blood?
14
How real is the threat of human extinction by gamma ray bursts?
3
What happens when wind / a fluid is put through a T-shaped tube, where the bottom of the T is closed off, but the two sides are open? What happens to the fluid in the closed, vertical tube?
46
Is learning another language simply additive to your mother tongue, or is the second language "separate" in your brain?
8
What is actually happening when an electric current flows through an a salt solution or a molten salt?
3
How can Burning wood (carbon) generate UV radiation?
39 CrustalTrudger > Could a meteor have struck Earth so hard as dislodge soil or rocks, shoot them into the atmosphere Yes, at least on the rocks parts (any unconsolidated material like soil would not survive the process). A good analogue are [Martian meteorites](https://en.wikipedia.org/wiki/Martian_meteorite). These are meteorites that fell on Earth, but were originally part of the Martian crust that were ejected from Mars during meteorite impacts on Mars. > and spread life into space? Little more uncertain. As discussed above, there is certainly the expectation of a decent amount of material from Earth that has been distributed throughout the solar system via impacts. For example, calculations considering the Chicxulub impact (the one thought to have brought about the K-T extinction) suggest that a [volume of Earth material equal to the size of the impactor was ejected into space](https://arxiv.org/abs/1204.1719). More general calculations [predict massive amounts of material were transferred between planets via ejecta, but mostly during the late heavy bombardment period between 3.8 and 4.0 billion years ago](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3440031/). The real questions to which we don't know the answer are 1) how much of this ejecta was life bearing (i.e. we still have limited evidence of life on Earth from the before or during the late heavy bombardment, but some signs point to there being some microbial life at that time) and 2) under what circumstances (if any) would microbes ejected into space via this process remain viable? There are suggestions that depending on the size of the debris, [some viable DNA/RNA within microbes could survive for several million years](http://iopscience.iop.org/article/10.1088/0004-637X/690/1/210/pdf), but it's still uncertain whether that is actually quick enough for these ejecta to end up on a planet/moon where life could flourish (seems like a long time, but consider that many of the asteroids and meteors have been orbiting the sun without impacting large planets or moons since at least the end of the late heavy bombardment period 3.8 billion years ago).
5 LeonAnon The main problem with that is that the distance between stars is mindbogglingly large. The nearest next star is at 250000 AU, compared to 40 AU for Pluto. So by the time any microbes/life would have crossed the gap, their DNA (or equivalent) would have degraded beyond repair by hard cosmic radiation. Even on Earth, which is moderately shielded against radiation, DNA/RNA [completely degrades within 3-7M years](http://rspb.royalsocietypublishing.org/content/279/1748/4724), and gets fragmented beyond repair long before that. And then those fragments would still have to survive reentry on a new world.
4 64vintage I have read that since the origin of life on earth, there have been at least one and possibly multiple times when the surface of the earth was entirely uninhabitable - molten etc. Since the theory is that life evolved only once, the conclusion is that the earth was re-seeded by former ejecta that returned to earth many years later, when conditions were less hostile. On that basis, the answer to your question is yes. EDIT : https://nai.nasa.gov/annual-reports/2002/uw/giant-impacts-in-earths-early-history-reseeding-the-planet-and-the-search-for-earth-rocks-on-the-moon/ " Project Progress We explore the likelihood that early remains of Earth, Mars, and Venus have been preserved on the Moon in high enough concentrations to motivate a search mission. During the Late Heavy Bombardment, the inner planets experienced frequent large impacts. Material ejected by these impacts near the escape velocity would have had the potential to land and be preserved on the surface of the Moon. In order to determine whether the Moon has preserved enough ejecta to justify a search mission, we calculate the amount of Terran material incident on the Moon over its history by considering the distribution of ejecta launched from the Earth by large impacts. In addition, we make analogous estimates for Mars and Venus. We find, for a well mixed regolith, that the median surface abundance of Terran material is roughly 7 ppm, corresponding to a mass of approximately 20,000 kg of Terran material over a 10 × 10 square km area Mounting attention has focused on interplanetary transfer of microorganisms (panspermia), particularly in reference to exchange between Mars and Earth. In most cases, however, such exchange requires millions of years, over which time the transported microorganisms must remain viable. During a large impact on Earth, however, previous work (Armstrong et al., submitted) has shown that substantial amounts of material return to the planet of origin over a much shorter period of time (< 5000 years), considerably mitigating the challenges to the survival of a living organism. Conservatively evaluating experiments performed on Bacillus subtilis and Deinococcus radiodurans to constrain biological survival under impact conditions, we estimate that if the Earth were hit by a sterilizing impactor ~ 300 km in diameter, with a relative velocity of 30 km s-1 (such as may have occurred during the Late Heavy Bombardment), an initial cell population in the ejecta of order 10-4 – 10-2 cells kg-1 would in most cases be sufficient for a single organism to survive and return to an again-clement planet 3000-5000 years later. Although little can be said about the characteristics or distribution of ancient life, our calculations suggest that impact re-seeding is a possible means by which life, if present, could have survived the Late Heavy Bombardment."
40 0 CrustalTrudger > Could a meteor have struck Earth so hard as dislodge soil or rocks, shoot them into the atmosphere Yes, at least on the rocks parts (any unconsolidated material like soil would not survive the process). A good analogue are [Martian meteorites](https://en.wikipedia.org/wiki/Martian_meteorite). These are meteorites that fell on Earth, but were originally part of the Martian crust that were ejected from Mars during meteorite impacts on Mars. > and spread life into space? Little more uncertain. As discussed above, there is certainly the expectation of a decent amount of material from Earth that has been distributed throughout the solar system via impacts. For example, calculations considering the Chicxulub impact (the one thought to have brought about the K-T extinction) suggest that a [volume of Earth material equal to the size of the impactor was ejected into space](https://arxiv.org/abs/1204.1719). More general calculations [predict massive amounts of material were transferred between planets via ejecta, but mostly during the late heavy bombardment period between 3.8 and 4.0 billion years ago](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3440031/). The real questions to which we don't know the answer are 1) how much of this ejecta was life bearing (i.e. we still have limited evidence of life on Earth from the before or during the late heavy bombardment, but some signs point to there being some microbial life at that time) and 2) under what circumstances (if any) would microbes ejected into space via this process remain viable? There are suggestions that depending on the size of the debris, [some viable DNA/RNA within microbes could survive for several million years](http://iopscience.iop.org/article/10.1088/0004-637X/690/1/210/pdf), but it's still uncertain whether that is actually quick enough for these ejecta to end up on a planet/moon where life could flourish (seems like a long time, but consider that many of the asteroids and meteors have been orbiting the sun without impacting large planets or moons since at least the end of the late heavy bombardment period 3.8 billion years ago).
6 0 LeonAnon The main problem with that is that the distance between stars is mindbogglingly large. The nearest next star is at 250000 AU, compared to 40 AU for Pluto. So by the time any microbes/life would have crossed the gap, their DNA (or equivalent) would have degraded beyond repair by hard cosmic radiation. Even on Earth, which is moderately shielded against radiation, DNA/RNA [completely degrades within 3-7M years](http://rspb.royalsocietypublishing.org/content/279/1748/4724), and gets fragmented beyond repair long before that. And then those fragments would still have to survive reentry on a new world.
4 0 64vintage I have read that since the origin of life on earth, there have been at least one and possibly multiple times when the surface of the earth was entirely uninhabitable - molten etc. Since the theory is that life evolved only once, the conclusion is that the earth was re-seeded by former ejecta that returned to earth many years later, when conditions were less hostile. On that basis, the answer to your question is yes. EDIT : https://nai.nasa.gov/annual-reports/2002/uw/giant-impacts-in-earths-early-history-reseeding-the-planet-and-the-search-for-earth-rocks-on-the-moon/ " Project Progress We explore the likelihood that early remains of Earth, Mars, and Venus have been preserved on the Moon in high enough concentrations to motivate a search mission. During the Late Heavy Bombardment, the inner planets experienced frequent large impacts. Material ejected by these impacts near the escape velocity would have had the potential to land and be preserved on the surface of the Moon. In order to determine whether the Moon has preserved enough ejecta to justify a search mission, we calculate the amount of Terran material incident on the Moon over its history by considering the distribution of ejecta launched from the Earth by large impacts. In addition, we make analogous estimates for Mars and Venus. We find, for a well mixed regolith, that the median surface abundance of Terran material is roughly 7 ppm, corresponding to a mass of approximately 20,000 kg of Terran material over a 10 × 10 square km area Mounting attention has focused on interplanetary transfer of microorganisms (panspermia), particularly in reference to exchange between Mars and Earth. In most cases, however, such exchange requires millions of years, over which time the transported microorganisms must remain viable. During a large impact on Earth, however, previous work (Armstrong et al., submitted) has shown that substantial amounts of material return to the planet of origin over a much shorter period of time (< 5000 years), considerably mitigating the challenges to the survival of a living organism. Conservatively evaluating experiments performed on Bacillus subtilis and Deinococcus radiodurans to constrain biological survival under impact conditions, we estimate that if the Earth were hit by a sterilizing impactor ~ 300 km in diameter, with a relative velocity of 30 km s-1 (such as may have occurred during the Late Heavy Bombardment), an initial cell population in the ejecta of order 10-4 – 10-2 cells kg-1 would in most cases be sufficient for a single organism to survive and return to an again-clement planet 3000-5000 years later. Although little can be said about the characteristics or distribution of ancient life, our calculations suggest that impact re-seeding is a possible means by which life, if present, could have survived the Late Heavy Bombardment."