Mike!
Official Ponylandistanian National Treasure. Re
A scientific fact/tidbit you recently learned that you thought was interesting
- Thread starter bigred
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gypsyjackson
Master Poster
Not all necessarily very recent except the last, but these three were interesting to me:
A bruise is trapped blood under the skin.
Bones make blood.
Elephants sleep standing up.
The last one my 4 year old told me, and I sort of believed her, but still had to fact check. It’s true most of the time, and also true of giraffes.
My school had a weird decision point - at 13 you had to choose to study one of German, Art, Biology, Music or… a couple of others I forget. So I studied German, and as a result I have no idea about biology beyond Attenborough shows. It’s actually very nice, as I am constantly surprised by the wonderful natural world, though it makes me look thick.
A bruise is trapped blood under the skin.
Bones make blood.
Elephants sleep standing up.
The last one my 4 year old told me, and I sort of believed her, but still had to fact check. It’s true most of the time, and also true of giraffes.
My school had a weird decision point - at 13 you had to choose to study one of German, Art, Biology, Music or… a couple of others I forget. So I studied German, and as a result I have no idea about biology beyond Attenborough shows. It’s actually very nice, as I am constantly surprised by the wonderful natural world, though it makes me look thick.
SteveAitch
Master Poster
aka a haematoma.
And the fancy name for a black eye is a periorbital haematoma.
A bruise is technically an echymosis. This is bleeding into the skin, there is no distinct collection of blood. A haematoma is slightly different in that it is a collection of blood, this may be felt as a distinct lump, and if a needle is stuck in to the lump one could suck the blood out and empty the haematoma. Of course both may occur together. Haematomas are usually due to injury to a larger blood vessel with a rapid point leak of blood, bruising is due to injury to capillaries with a diffuse leak from small blood vessels over an area.
Small areas of bleeding into the skin less than 3mm in diameter and flat are called petechiae, larger areas are purpura, and if over 1cm become echymosis. If a result of trauma they may be grouped as contusions, but in some diseases the bleeding may be spontaneous. Most parents will have been warned to look for small non-blanching rashes in infants (petechiae) that may occur in sepsis.
ETA In medicine things ending oma usually mean that they cause a lump.
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lobosrul5
Philosopher
So what you are saying is, that not only is FTL impossible, but going faster than .5C is impossible if two objects are traveling in exactly opposite directions from a given point of reference? (or is that only the case if there is an observer?)
There's nothing preventing two objects from both traveling at a high fraction of c in opposite directions from the Earth (or any arbitrarily designated inertial "fixed" point). Let's say, two spaceships going in opposite directions. From Earth we observe each of them moving at .95c which would be an impossibly difficult technical achievement but completely consistent with the laws of physics.
We would be mistaken if we thought that meant the spaceships were traveling at .95c + .95c = 1.9c relative to one another. The speed of either ship, as observed/measured from the reference frame of the other ship, would still be below 1.0c.
Pixel42
Schrödinger's cat
It's only the case if Newton's laws of motion are correct, which they are not. They were superceded by Einstein's special theory of relativity. The relative speed of the two objects is not the sum of the two speeds.
Thermal
August Member
All of which is why time dilation really pisses a brother off.
ETA: the speed itself is not the issue. It's that you get a middle finger flipped named c at you for even trying.
ETA: the speed itself is not the issue. It's that you get a middle finger flipped named c at you for even trying.
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lobosrul5
Philosopher
So... lets say 2 probes are sent out from earth, each going .95c in exactly opposite directions. After 1 year they'd both be just under 1 light year away from earth. But relative to each other they are only traveling .999c.... but after year they'd be 1.9 light years way from each other... are those somehow both correct statements? This stuff does my head in.
Delvo
Дэлво Δε&#
They'd be correct statements for us here on Earth but not for them. Relativity stretches & squeezes not only speed but also time & distance.
Ziggurat
Penultimate Amazing
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There are multiple implicit assumptions in your question which are wrong. These are completely reasonable assumptions, but the universe doesn't have to behave according to what we think is reasonable. One of the biggest assumptions is that the two events (which we can define as a point in space and time), namely the location of each probe after 1 year on earth, are simultaneous in each probe's reference frame. They are not. One of the biggest things you have to wrap your head around when studying special relativity is that things which happen simultaneously in one reference frame actually happen at different times in other reference frames. We also need to add in length contraction, time dilation, and nonlinear velocity addition. The results aren't remotely intuitive, but they are mathematically rigorous, internally consistent (if they don't look that way, you're missing something, which can happen very easily), they are supported by tons of experimental evidence, and the universe is indifferent to our confusion.
Here's a breakdown of what this scenario looks like in three different reference frames:
Graph 1 is what things look like from earth if you send out two probes in opposite directions, they travel out to some fixed distance, then turn back around and return to earth. Graph 2 is what it looks like in the frame where the probe going right is stationary for its outbound travel. Graph 3 is what it looks like in the frame where the probe going left is stationary for its outbound travel.
Note that we aren't plotting what happens in a frame where either probe is always stationary, because those aren't inertial frames and things get REAL weird if we want to work with non-inertial frames so let's not do that because we don't need the headache.
ZirconBlue
Sole Survivor of L-Town
While a giraffe's only contains 7.
Horses also can sleep standing up.
lobosrul5
Philosopher
Horses do sleep a bit here and there while lying down. They need to do so in order to get REM sleep. The more comfortable and safe a horse feels, the more likely he'll lay down for some sleep.
https://www.petmd.com/horse/do-horses-sleep-standing
It looks like elephants are the same, but to a more extreme, only lying down for sleep a bit every 3rd of 4th night.
Thermal
August Member
I just googled that in surprise, and don't see a source that agrees. Do you have a work in mind that supports it?
Delvo
Дэлво Δε&#
"Fatal Familial Insomnia"
Loss of sleep starts in adulthood, late enough to have already passed the gene on. Once it begins, it leads to gradual deterioration of mental functions over months/years and then an early death.
Loss of sleep starts in adulthood, late enough to have already passed the gene on. Once it begins, it leads to gradual deterioration of mental functions over months/years and then an early death.
lobosrul5
Philosopher
That isn't equivalent to cannot dream = death sentence. I believe I went a couple or 3 years where if I did dream, I could not recall it.
Yes, you need to get into the details. though you may not recall it, you dream - REM sleep. E.g.
https://jamanetwork.com/journals/jamaneurology/fullarticle/2767713
or if you like celebrities
https://jamanetwork.com/journals/jamaneurology/fullarticle/2767713
You can argue about whether lack of sleep, or lack of dreaming is more important, but dreaming seems to be the key element and the Sandman is on my side.
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lobosrul5
Philosopher
That study suggests that lack of REM sleep is linked to increased morbidity. But it doesn't say that no REM means you are going to die*. Its not even clear that its the lack of REM that causes death, or if its a co-morbidity. If you suffer from poor quality sleep, its likely because of a health condition which is what is actually killing people. Although I can safely say that lack of quality sleep sucks.
*well obviously it does, since everyone eventually dies (so far)
ETA: in fact a conclusion from the study: . Accelerated brain aging may result in less REM sleep, making it a marker rather than a direct mortality risk factor
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catsmate
No longer the 1
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It's becoming more of a nuisance as atomic clocks become more accurate.