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/r/AskScience Weekly Top 10: Feb 11-18, 2012
Question | Top Answer Given :--|:-- 1. [How many plants would I need to have in a sealed room with me to never run out of oxygen?(Studybuddies)](http://www.reddit.com/r/askscience/comments/pmbbj/how_many_plants_would_i_need_to_have_in_a_sealed/) | tl:dr - answer: 17.5 trees **(madmaxola)** 2. [How do we measure mountains on Mars without a level for zero? Ie, our sea level.(HiDef90)](http://www.reddit.com/r/askscience/comments/ps7kw/how_do_we_measure_mountains_on_mars_without_a/)| You're right, there is no sea level but it is still useful to have a standard height against which to compare geographical features. So we arbitrarily defined a level which we call "zero elevation." This is called the Martian datum, and is defined as the height at which the atmospheric pressure averages 6.105 mbar at 273.16 K. **(FlexorCarpiUlnaris)** 3. [What would happen if a person stayed underwater continuously without drying off? Like.. for a day, a week, a year, whatever. (kungfu_kickass)](http://www.reddit.com/r/askscience/comments/pne5l/what_would_happen_if_a_person_stayed_underwater/)| What happens when you have prolonged immersion is your body absorbs a good bit of water through osmosis. The skin is not completely impermeable and after a long time it becomes even more permeable. This water is "pure" water lacking electrolytes (Na, K, etc.) and so moves into tissue cells. This skews your fluid balance and your body gets a bit confused. It becomes over-hydrated.**(binlargin)** 4. [What is happening when I wake up starving, wait an hour or two and don't eat, and the hunger dissipates?(ludvigsra)](http://www.reddit.com/r/askscience/comments/pjcyd/what_is_happening_when_i_wake_up_starving_wait_an/)| I'm an MD, but not an endocrinologist or dietary specialist. I'm just going off of my basic medical school knowlege here, plus a bit of personal reading, and I don't have a specific source to offer other than "an endocrine/metabolism textbook". So, don't take everything you see on the internet as gospel. This is not medical advice. Some parts may not be accurrate, but I hope they'll give people some place to start. ...|It's not starvation mode. When you get this feeling, your body has burned off much of the free, easy glucose in the blood, liver and muscle, and is in a transition period where it decreases the rate of glucose metabolism and begins to rev up the burning of fatty acids. Until this process is complete, and the fatty acid metabolism is up to speed, you'll feel wanting. But then you'll suddenly feel fine again. You usually don't feel hungry like that in the AM because you slept through the transition period and are already burning fat efficiently by the time you wake. For most people, the culprit is likely eating late in the evening or having a "midnight snack." By doing this, your body won't run low on glucose until later in the night, possibly not until the time you wake up. ...|If you wake up still in (or not even yet having started) the transition phase, you'll get the ravenous hunger feeling. Actual starvation phase begins much later. Here, the body starts breaking down muscle and organ tissue. Exactly when this starts varies a lot, depending on the individual fat stores and such, but doesn't generally begin until 10 days or two weeks without sufficient intake. If the starvation is dramatic (like, bam, all of a sudden eating almost nothing), then the muscle/organ breakdown may begin earlier.**(You_Know_My_Name)** 5. [Why do people pee whilst pooping?(Machrus)](http://www.reddit.com/r/askscience/comments/ps7rt/why_do_people_pee_whilst_pooping/)|To speed defecation (i.e. to poop quickly), humans contract their abdominal muscles. This increases the pressure inside their abdomen, forcing its contents (i.e. poop) out. However, increasing intra-abdominal pressure also puts pressure on your bladder.our bladder is specially designed to contract and make you pee whenever it senses pressure. This is called the micturition reflex. Usually, pressure in the bladder is a sign that the bladder is full, so peeing is necessary. But when you are pooping (and straining a bit, which increases the pressure in your abdomen) the bladder senses this increased pressure and contracts. The reason you sometimes can't stop yourself from peeing is that the combined pressure of your abdomen contracting to poop and your bladder contracting reflexively overpowers your external urethral sphincter.**(FlexorCarpiUlnaris)** 6. [What happens inside your body when you get hit on the head hard enough to black out? (Caturday_Yet)](http://www.reddit.com/r/askscience/comments/pqpuf/what_happens_inside_your_body_when_you_get_hit_on/)|Losing consciousness is complex, it's not usually a matter of damage to any particular part of the brain, but rather a disruption in the coordination of neural activity. This loss of coordinated brain activity is also what happens during sleep or anesthesia, though usually in a less disruptive way. When the different components of your brain can't talk to each other, you can't do high-level coordinated things like talking, thinking, standing etc. ...|Much more worrying are acute complications and long term consequences, a blow to the head that causes blacking out can cause intercrainial bleeds which is a "get to the hospital and get a hole drilled in your head or be dead in an hour" situation. Anyone blacking out for more than a few seconds should probably be getting a CT or MRI real quick. Long term consequences can also be dire, lots of regions can get damaged during a head injury: hippocampal damage can cause transient or permanent amnesia, motor cortex damage can cause tremors, dorsal striatal damage can cause gambling addiction, and damage to visual cortex can cause you to see stars (sometimes permanently).**(Majidah)** 7. [Does popping your neck and back daily cause damage?(saw630)](http://www.reddit.com/r/askscience/comments/pu1mg/does_popping_your_neck_and_back_daily_cause_damage/)|The popping sound you get is due to a process call cavitation, where carbon dioxide bubbles will form in fluid, then collapse on itself. This process is pretty harmless. You could potentially injure yourself by extreme or sudden stretching or deviation. The injury can be muscular (straining your neck or back), skeletal (dislocation, although very unlikely), or neural (pinching a nerve). Of course if you have associated problems or had previous injury, you are more likely to get hurt. However, these are more trauma related and acute injuries. Daily cracking your neck and back, within normal limits, probably won't cause any degenerative or chronic damage to your joints. As for the stroke, he would have had to have previous or underlying risk factors (aneurysm, family history, high blood pressure, etc.), but I highly doubt that it was his neck cracking that caused him to have that stroke.)**(one_way_only)** 8. [CERN People! Is this real data?(haikarainen)](http://www.reddit.com/r/askscience/comments/ppntn/cern_people_is_this_real_data/)-Look at the backdrop of the leftmost display in this picture, is that just fancy eyecandy or is that real data? Like a current snapshot of one of them bang-in-long'pipe-chambers? Either way it feeds my brain teh munchies! |t's more fancy eyecandy than data. Granted we all love how it looks, and displays like this help us debug our software, but usually we're running through millions or billions of collisions and we can't sit down with a picture and a ruler and make measurements. So all the data is stored in some file, then passed over with some analysis software, and then the physics pops out as some histogram or something from the analysis software. But the display is accurate it is a representation of the tracks and energy passing through the detector (the tracks are the things that look like tracks, and energy is the big towery lookin things)(shavera) 9. [Is there any organism that can't perceive three dimensions?](http://www.reddit.com/r/askscience/comments/ptpkt/is_there_any_organism_that_cant_perceive_three/)(self.askscience)(RiseOtto)|This really depends on your definition of "perception". In theory, if a flat organism is utilizing chemotaxis to perceive the world, only two dimensions can be recognized at a time. However, there is no reason that a third axis would be completely unrecognized -- if a drop of that same chemical trigger is placed above the organism, a similar response would occur as if it were to the side, although movement may or may not be entirely successful. Hence, perception is present, but the ability to respond is not. ...|If you take it down to the simplest of things, then the inability to perceive would be the only way an axis of dimension can be ignored. For example, a free-floating microbe that relies on currents to attain food and other resources would not be able to, or even need to, recognize the three dimensions. ...|I guess at this point, you may as well say that this is a philosophical question, as you implied: does perception matter if you cannot recognize and react to it?**(8vdude8)** 10. [How do the lungs heal after a smoker quits?](http://www.reddit.com/r/askscience/comments/pnu7h/how_do_the_lungs_heal_after_a_smoker_quits/)(Ignite_My_Paradigm)|Within 20 minutes after quitting, blood pressure and heart rate decrease. Within 12 hours, carbon monoxide levels in the blood decrease to normal. Within 48 hours, nerve endings and sense of smell and taste both start recovering/Within 3 months, circulation and lung function improve. Within 9 months, there are decreases in cough and shortness of breath. Within 1 year, the risk of coronary heart disease is cut in half. Within 5 years, the risk of stroke falls to the same as a non-smoker, and the risks of many cancers (mouth, throat, esophagus, bladder, cervix) decrease significantly. Within 10 years, the risk of dying from lung cancer is cut in half, and the risks of larynx and pancreas cancers decrease. Within 15 years, the risk of coronary heart disease drops to the level of a non-smoker.**(medstudent22)** **Note:** Answers may have been edited for formatting/clarity purposes. Please refer to the link for the original post if you require more information. For mo|re questions/answers, please visit /r/askscience. more