Recent comments in /f/askscience

LoneGiggity t1_j2e2ok0 wrote

Reply to comment by adam12349 in How did Rutherford arrive at gold foil as the best choice for his particle experiments? by Poltibolsa

Is this also the reason why NEO radiation shielding is gold thin? From these experiments? I vaguely remember being taught that thick shielding is the exact opposite of what is needed in module shielding for near earth and lunar orbits. Its information 30 plus years old that randomly sits in my brain.

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Busterwasmycat t1_j2e2dnc wrote

Reply to comment by NakoL1 in Why is Mitochondrial Eve dated to 150-170,000 years go? by jayhovian

which makes it so you have to go back to the very first life form (if there was such a thing), if you take it to the logical conclusion. There are some things that all life shares. We are not so much interested in that stuff, because it does not tell us anything we don't already know (that all life appears to have come from a common origin). We are interested in when the things that make us different came into existence, when we "separated" from the other life that is not like us.

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agate_ t1_j2dz8m3 wrote

Reply to How is Historic Sea Level Measured? by Rosanbo

Many ocean organisms live only at specific depths. For example, the coral Acropora palmata only grows within a few meters of the sea surface, where it can get the most sunlight.

Suppose you drill a core into a coral reef using a floating drill, and find some of this coral that's 10,000 years old at a depth of 100 meters below the surface. How could this happen? Either the sea level must have risen, or the island the coral is growing on must have sunk.

You can figure out whether the island has sunk by looking for very old corals of the same type. For example, if you find corals dating back to a previous warm period 120,000 years ago at or above sea level, you can be sure that the land isn't sinking very fast.

You can repeat this analysis for other corals that live at greater depth, you can repeat the analysis in coral reefs all around the world, and repeat it for other types of organisms that live near the water surface in colder climates, and you find a consistent pattern of sea level change over time.

> Is someone who denies the historic sea level graph equivalent to a Flat Earther?

There aren't many people who deny that sea level has changed. Most often climate change deniers use the past sea level graph to show that sea levels are not stable, and thus -- they say -- the current sea level rise is nothing special, and a natural process. Some people argue that the ages of the changes are wrong, and the sea level changes actually represent the biblical flood.

http://people.uncw.edu/grindlayn/GLY550/Fairbanks-Sealevel-1989.pdf

https://www.sciencedirect.com/science/article/abs/pii/S0012821X98001988

https://commons.wikimedia.org/wiki/File:Post-Glacial_Sea_Level.png

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clocks212 t1_j2dyrqf wrote

Reply to comment by Theban_Prince in How fast does the Milky Way spin? How far does Earth move through space in a year? by Sabre-Tooth-Monkey

Only from an outsiders perspective would you freeze. From an outsiders perspective a black hole can be thought of as “a region of space where nothing has ever happened”. From your perspective you would just fall straight through the event horizon like nothing was there until you were killed by gravitational forces or impacted whatever exists at the center of the black hole.

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FeloranMe t1_j2dyq46 wrote

Reply to comment by NeighborhoodNorth249 in Why is Mitochondrial Eve dated to 150-170,000 years go? by jayhovian

Mitochondrial Eve is the most recent ancestor who had an unbroken line of daughters to the present day. She also had to have had two daughters. If she had one that woman would be Mitochondrial Eve.

Eve's daughters passed on the mitochondrial line that are present today in every human on Earth. So she was the many times great grandmother of every human on Earth.

She was not a new species. She might not have had any advantageous characteristics. There is likely nothing special about her mitochondria. There were many other human beings living alongside her and long, long before her. What was significant was that her descendants included an unbroken line of daughters.

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