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Sunday, June 30, 2019

How long did it take dinosaurs to go fully extinct?

How long did it take dinosaurs to go fully extinct?


How long did it take dinosaurs to go fully extinct?

Posted: 29 Jun 2019 11:34 AM PDT

How much of life was vaporized on impact, and how long could those that survived the initial impact manage to live? Was it a matter of hours, days, or years or even generations before the dinosaurs fully vanquished?

Edit: I do realise birds and some other animals evolved from dinosaurs, but, as we just recently had a case of a bird species evolving itself back from extinction, let's just simplify to the big ones we all know and love from children's books and from Jurassic Park, the ones that definitely aren't around anymore :)

submitted by /u/FrogsArePeople2
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Given the way the Indian subcontinent was once a very large island, is it possible to find the fossils of coastal animals in the Himalayas?

Posted: 30 Jun 2019 06:55 AM PDT

Does lava at the center of the earth rotate with the crust, or does it keep still like water in a rotating glass?

Posted: 30 Jun 2019 03:54 AM PDT

I know the crust is a relatively thin layer and I can only imagine big layers of earth to be rotating around the center underneath the crust, if not the entire inside of our planet. But is there a point at which the hot fluid material inside stays still relative to the outer layers, just like water in a rotating glass?

submitted by /u/pavignon
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How were heavier elements than iron created?

Posted: 30 Jun 2019 03:53 AM PDT

I've just read that young stars fuse hydrogen together into helium. After a few million years, the H in the core uses up and the star starts burning hydrogen outside its centre, expand and cool. Then, after the hydrogen is fused, it will start fusing helium, carbon, neon, oxygen, silicon and finally iron. But the last one doesn't fuse further. So, how did the heavier elements come into existence? I'm talking about lead, gold, silver, copper etc. They weren't created in stars, so where were they?

submitted by /u/d4rg0n
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Why do intermolecular dipolar forces decrease at a rate of 1/r³ and ion-ion interactions decrease at 1/r rate even though the force that mediates them is the same (electromagnetic)?

Posted: 30 Jun 2019 04:57 AM PDT

While driving, if you look at dips in the road that are far away they seem to reflect light from ahead like a mirror. Why?

Posted: 29 Jun 2019 01:29 PM PDT

Would there be less drag when swimming if your body had hydrophobic coating?

Posted: 29 Jun 2019 08:50 PM PDT

Just watched this youtube video where a guy was coated in aerogel which made him completely dry even if he went shoulder deep into water. Which made me wonder if Michael Phelps was coated in this aerogel would their be less drag in the water which would = better times?

submitted by /u/koukiboi
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Can quartz make noise with electricity ?

Posted: 30 Jun 2019 01:02 AM PDT

Soo crystal oscillators use electricity to oscillate quarts for time measurement but can you get quartz to vibrate at an audible frequency that can be heard just from the crystal?

submitted by /u/Cobbledon
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How can we see light beams even when they are not pointing towards us?

Posted: 29 Jun 2019 10:28 PM PDT

So light beams are usually cylindrical and point in a specific direction. From what I have learnt, if we see an object, light is reflecting off that object and into our eyes. If a light beam is not pointing at us i.e the light is not reaching our eyes, how are we still able to see it? P.S. I just realized how stupid this question may end up being, this is what you get from a dumb 15 year old

submitted by /u/Ciltan
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If light is an electromagnetic wave , just like infra red or radio, can we use non optical instruments like Antennae to detect it ?

Posted: 29 Jun 2019 11:50 PM PDT

Conversely, is it possible to use optical equipment to detect non optical em radiation, eg. a lens or mirror to detect radio waves ?

submitted by /u/Vidhrohi
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What is the oldest expression we still use in modern times?

Posted: 29 Jun 2019 08:24 AM PDT

Expressions like "to the bitter end" are relatively new, but are there some which made it over from old cultures? And how old would they be?

submitted by /u/Fubushi
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Is the heat from a fire transferred by convection, conduction or by radiation?

Posted: 30 Jun 2019 02:09 AM PDT

Why do some satellites need to boost themselves to stay in low earth orbit while others (Kosmos-2251) can cease function and remain in orbit?

Posted: 29 Jun 2019 12:07 PM PDT

Kosmos-2251 ceased function in '95 yet stayed in orbit until it collided with an Iridium sat in '09.

submitted by /u/yota-runner
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Are jugular veins redundant, or feed one side of the brain each?

Posted: 29 Jun 2019 11:37 PM PDT

And would death be experienced differently depending on which side of the brain loses blood first?

Bonus question: If you fall asleep with one jugular compressed, can you die from it?

submitted by /u/xot
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Why are modern birds dinosaurs and not fish?

Posted: 29 Jun 2019 10:31 PM PDT

I've seen it said many times (eg https://xkcd.com/1211/ ) that modern birds are dinosaurs. But couldn't the same be said that all vertebrates with lungs are fish? What are the rules about whether descendant groups get excluded from a classification? Is this what's meant by "paraphyly"?

submitted by /u/ElectronRotoscope
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Who was the first to realize that the Moon is round?

Posted: 29 Jun 2019 09:44 AM PDT

There's plenty of info about the discovery that the Earth is round, but I can't find anywhere that discusses who first guessed/proved that the Moon is round.

On the one hand it seems like it would be easy to figure out because of the way it is lit, but I could also see its synchronous rotation throwing people off.

submitted by /u/ajkolenc
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What would happen if the black hole in the center of our galaxy suddenly disappeared?

Posted: 29 Jun 2019 03:28 PM PDT

How does our brain interpret what we see? further explanation inside

Posted: 29 Jun 2019 12:53 PM PDT

I want to know in a general sense, does our brain put together the simple concepts first and then work its way up to the more complex details?

e.g. You open your eyes after a long nights rest. Does your brain first differentiate whether it is light or dark, then the general environment you are in such as the shape of your room, then how large that room is, how much space do objects take up, then the what do those objects look like, what's kept in those objects or the fine details of their decorative design, etc.

OR does it all happen at once, like a computer generating all details of a render simultaneously?

Thank you for any help you can provide :)

submitted by /u/OfficialDodo
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How are food expiration dates assigned?

Posted: 29 Jun 2019 02:45 PM PDT

In other words, what is the process behind determining that my fruit snacks might not be as good in February 2021 as they are in January 2021?

submitted by /u/CrazyHorse1495
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Is superluminal communication possible?

Posted: 29 Jun 2019 02:44 PM PDT

I've never found a very clear answer to this question. By superluminal communication I mean some phenomenon that causes information to be transported over a distance faster than light travels over that same distance. In science fiction I often hear that quantum entanglement represents such a phenomenon but I haven't found the concrete science to support this. Thanks for your reply!

submitted by /u/konglongjiqiche
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How do bladeless fans generate wind?

Posted: 28 Jun 2019 10:07 PM PDT

Saturday, June 29, 2019

Why do plants never get cancer?

Why do plants never get cancer?


Why do plants never get cancer?

Posted: 28 Jun 2019 01:51 PM PDT

All humans and most other animals are at risk of getting cancer during their lifetime.But why plants have the privilege of not getting this disease?

I'm really impressed by most of your responses,but their is a question in my mind that is still bugging me.

When a person gets really old,cancer cells would form in a certain part of his body since his DNA becomes "weaker"as he got older ,but let's say just in this case that the cancer cells can not move to other parts of his body(Metastasis )to make the situation similar to plants where cancer cells are locked in this position since they have cell walls that surround the cells. Cancer cells would still originate from different parts of his body as he gets older until tumor covers all of him and he dies.

This case is theoretically possible for a human,but some trees live for thousands of years and it doesn't seem that tumors are covering all of their parts...Why?

submitted by /u/typicalredditluser
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During the carboniferous period, the oxygen level was ~35%. Now it is ~21%. There is less oxygen in atmosphere now. Where is that oxygen now?

Posted: 29 Jun 2019 04:14 AM PDT

During the carboniferous period, the oxygen level was ~35%. Now,the level is ~21%. There was a 41.5% oxygen decrease in atmosphere. Considering the fact that the level of CO2 were always negligible - at the beginning of the carboniferous period was only 7000ppm (~0,7%),now it is ~0,04% . Where is that oxygen now? I understand that breaking down lignin was difficult and it became coal but coal is mostly carbon. This explains the fact that carbon is trapped as coal but where is that oxygen trapped now?

submitted by /u/diablo950
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How do scientists get neutrons for experiments?

Posted: 28 Jun 2019 09:04 AM PDT

I'm an amateur nuclear engineer, and I want to preform an experiment with lithium fission, but I need a source of neutrons. I've heard of neutron sources like AmBe, PuBe, RaBe, etc. Are these typically used as neutron sources in experiments, and where can I get one? I can't find them online.

Thanks in advance!

submitted by /u/Adam__999
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Why do we get ticklish?

Posted: 29 Jun 2019 04:03 AM PDT

Why can't Dendritic cells kill HIV?

Posted: 28 Jun 2019 08:47 PM PDT

It is known that Dendritic Cells can engulf free floating pathogens.How is it so that they can't engulf all free floating Human immuno deficiency virus before they find a host cell (the CD4+ cell)?

submitted by /u/idkyallzxcv
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Can we see the Milky Way?

Posted: 29 Jun 2019 02:28 AM PDT

All those beautiful pics on Reddit of the Milky Way Galaxy, can they be seen by the naked eye or is that only possible through a lens?

submitted by /u/GenderlessJohn
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When performing a gravitational slingshot maneuver, does the direction the planet is rotating in relative to a spacecrafts trajectory make a difference?

Posted: 28 Jun 2019 05:23 PM PDT

I've probably worded this poorly, and this might seem obvious.

I read some interesting comments on a post earlier and when speaking to my friend about it we disagreed on the above statement.

While I was able to find lots of information about gravitational slingshots I didn't immediately see any that explicitly mentioned the rotation direction of the planet.

I thought that it was the gravitational pull of the planet that accelerated a spacecraft and it wasn't really important what direction it was rotating in.

He thought that it was entirely dependant on the rotational direction of the planet and a spacecraft would have to enter its gravity in the same direction.

Please can you help me clear this up.

Thank you!

submitted by /u/Dev_alo
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In terms of sleep-quality, is it better to dream or not dream?

Posted: 28 Jun 2019 06:31 AM PDT

I feel most rested after sleeping when I cannot recall my dreams upon waking, and least rested when I wake with memories of intricate, vivid dreams.

Is one better than the other in terms of physical and mental rest?

submitted by /u/morbid_possum
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Can photons red-shift due to gravity wave losses?

Posted: 28 Jun 2019 06:10 PM PDT

I have heard photons have momentum, and with it an effect on gravity. If large masses slowly lose speed due to radiating gravity waves, could photons be affected similarly over long enough distances? Would it change our estimates of galaxy speeds?

Edits: For more clarification, I am asking about the red-shift due to gravity waves emitted by the photons themselves, not about normal red-shift from climbing out gravity wells.

submitted by /u/sparkgenerator
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Identifying basic sedimentary rocks in the field. How can I distinguish sandstone, limestone, shale, etc with a hand lens? I'm more looking for what I should see using hand lens rather than "shale looks like sheets of gray rocks while sandstone + limestone generally won't"

Posted: 28 Jun 2019 05:55 AM PDT

Why is the periodic table called the periodic table?

Posted: 28 Jun 2019 05:24 AM PDT

Why does a book fall faster than a paper of the same length and breadth?

Posted: 28 Jun 2019 05:07 PM PDT

What will happen to the gas giants once the sun becomes a white dwarf? Will they break free from the solar system? How long will they stay as gas giants?

Posted: 28 Jun 2019 12:46 AM PDT

There are a lot of sources out there describing what would happen to the solar system ones the sun becomes a red giant. Mercury, Venus, and Earth would be swallowed by the sun, Europa, Enceladus, Titan etc would probably have better conditions for life, Saturn would lose its rings etc. But what I don't find a lot of sources in is what would happen to the gas giants once the sun passes its red giant phase. Would its gravity still be strong enough to keep the gas giants in the solar system? When would our little neighborhood in the milky way cease to exist? I guess the reason why there aren't a lot of sources on this one is because it's too far ahead in time to theorize a plausible scenario. But are there any vague or general theories out there?

submitted by /u/haters811
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Why is precipitation is so scarce in the Levant region on summer being that there's plenty of heat and humidity?

Posted: 27 Jun 2019 11:31 PM PDT

Is there a blob of particles that only loosely interact with matter at the 'bottom' of gravity wells, such as Earths?

Posted: 27 Jun 2019 08:30 PM PDT

I know there are particles out there that don't have very many interactions with the EM field and the Strong field, like Neutrinos, which are more or less only affected by gravity. I know Neutrinos are very short-lived, but if they were longer, they would collect eventually at the bottom of gravity wells, in the center of massive objects. Is it possible that there are bunch of exotic particles at the center of the earth, the sun, etc? If so, is there any way we could even know this? Could an increase in gravity from these particles be distinguished from just a heavier core?

submitted by /u/bryophytic_bovine
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How is the amount of calories in a given food determined?

Posted: 27 Jun 2019 08:15 PM PDT

Friday, June 28, 2019

Why are interplanetary slingshots using the sun impossible?

Why are interplanetary slingshots using the sun impossible?


Why are interplanetary slingshots using the sun impossible?

Posted: 27 Jun 2019 05:51 PM PDT

Wikipedia only says regarding this "because the sun is at rest relative to the solar system as a whole". I don't fully understand how that matters and why that makes solar slingshots impossible. I was always under the assumption that we could do that to get quicker to Mars (as one example) in cases when it's on the other side of the sun. Thanks in advance.

submitted by /u/dracona94
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AskScience AMA Series: I'm Susan Goldberg, Editor in Chief of National Geographic - AMA!

Posted: 28 Jun 2019 04:00 AM PDT

My name is Susan Goldberg and I'm the Editor in Chief of National Geographic. Tiny resume: 10th editor of National Geographic since it first published in 1888; 1st woman in the job; ran two major metro dailies; 40 years as a journalist; Michigan native; proud MSU j-school grad.

Since I joined National Geographic in 2014, we've covered everything from gender and race to the war on science and climate change. We're all about taking National Geographic from reverence to relevance, so you'll find us across print, digital and social platforms. Two weeks ago, we started our first podcast called Overheard at National Geographic!

There's a lot happening, but now's the chance to ask me anything! I'll be on at 1pm MDT / 3pm ET (19 UT).

submitted by /u/AskScienceModerator
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What's so special about lead (Pb) that makes it block radiation? Can other elements do this?

Posted: 27 Jun 2019 03:14 PM PDT

How Do Astronomers or Scientists Visualize Milky Way and The Exact Position of Our Solar System?

Posted: 28 Jun 2019 01:34 AM PDT

How do they do that actually? It is like figuring your specific coordinate in a random place in Earth just with a view from your camera in monopod. I doubt that there are camera/telescope that is placed above the milky way and just take a picture of it then send to Earth when Voyager 1, the farthest camera in Earth that I know, was only 3.75 billion miles away. The same with other galaxies like Andromeda. We are surrounded with celestial bodies in all directions, so how do they exactly picture/visualize that?

submitted by /u/Pervert_Spongebob
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How do our brains know how fast to make our hearts pump?

Posted: 27 Jun 2019 04:19 PM PDT

Why don't we just coat windshields in superhydrophobic coatings instead of using windshield wipers on cars?

Posted: 27 Jun 2019 09:36 PM PDT

It's 1am and I'm tired.

submitted by /u/t1r3dd
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What gives the purple tint to lightning bolts?

Posted: 27 Jun 2019 05:44 PM PDT

Are there any studies done on how many people's health was affected by Deep Water Horizon?

Posted: 27 Jun 2019 10:33 PM PDT

What is the current status of the nuclear winter hypothesis?

Posted: 27 Jun 2019 01:30 PM PDT

What is the current status of the nuclear winter hypothesis? Is the concept of a nuclear winter supported by scientific evidence?

submitted by /u/Lefty1992
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Geologists: do we know or would it be possible to know if there was ever a peak taller than Mount Everest in the past?

Posted: 27 Jun 2019 07:36 AM PDT

How do bones turn to ashes during cremation?

Posted: 27 Jun 2019 10:32 AM PDT

Is plate tectonics unique to out planet?

Posted: 27 Jun 2019 10:36 AM PDT

Do other planets in our solar system, or planets we have observed outside of our system, show signs of earthquakes, volcanic activity, rift valleys?

submitted by /u/InitialCareer
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How does the mitochondria maintain its proton gradient if the outer membrane have large pores that allow large molecules like acetyl-coa to pass through?

Posted: 27 Jun 2019 10:24 PM PDT

I did my own research beforehand but: one, the science speech puzzled me and I shouldn't be wondering about this an hour before my biochem exam; two, it talked about proton leaking through the inner membrane and not the outer one which is the one that I'm asking about. Thx.

submitted by /u/DANDANTHEDANDAN
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What happens at molecular level when water douses fire?

Posted: 27 Jun 2019 10:19 AM PDT

If anti freeze lowers the freezing point of a fluid, wouldn’t it also lower the boiling point?

Posted: 27 Jun 2019 03:43 PM PDT

How is TMB (tumor mutation burden) measured, and what are the limits that prevent it from clinical use at this point in time?

Posted: 27 Jun 2019 05:17 PM PDT

Do aquatic plants have a mechanism to inhibit or deter algae growth on their leaves?

Posted: 27 Jun 2019 05:25 AM PDT

What chemical reaction causes food to go stale?

Posted: 27 Jun 2019 06:03 PM PDT

How could we track pluto but not the other asteroids in the belt?

Posted: 27 Jun 2019 04:34 PM PDT

How did the greeks manage to observe Pluto consistently yet now we know its only one of hundreads in the belt, not even being the largest?

How didn't they loose Pluto or find Eris? What makes Pluto, Ceres, Vesta or Oallas so special we could keep track of them without noticing the rest of the belt?

Edit: Spelling

submitted by /u/_Drion_
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