Why are the stars and planets spherical, but galaxies flat? | AskScience Blog

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Monday, March 4, 2019

Why are the stars and planets spherical, but galaxies flat?

Why are the stars and planets spherical, but galaxies flat?


Why are the stars and planets spherical, but galaxies flat?

Posted: 03 Mar 2019 09:15 PM PST

Starfish Prime was the largest nuclear test conducted in outer space, by the US in 1962. What was its purpose and what did we learn from it?

Posted: 04 Mar 2019 05:28 AM PST

AskScience AMA Series: We are John Ibbitson, an award-winning journalist, and Darrell Bricker, a leading international social researcher, and we wrote a book about population decline happening sooner than projected. Ask us anything!

Posted: 04 Mar 2019 04:01 AM PST

An award-winning journalist and leading international social researcher make the provocative argument that the global population will soon begin to decline, dramatically reshaping the social, political, and economic landscape.

For half a century, statisticians, pundits, and politicians have warned that a burgeoning population will soon overwhelm the earth's resources. But a growing number of experts are sounding a different alarm. Rather than continuing to increase exponentially, they argue, the global population is headed for a steep decline-and in many countries, that decline has already begun.

In Empty Planet, John Ibbitson and Darrell Bricker find that a smaller global population will bring with it many benefits: fewer workers will command higher wages; the environment will improve; the risk of famine will wane; and falling birthrates in the developing world will bring greater affluence and autonomy for women.

But enormous disruption lies ahead, too. We can already see the effects in Europe and parts of Asia, as aging populations and worker shortages weaken the economy and impose crippling demands on healthcare and social security. The United States and Canada are well-positioned to successfully navigate these coming demographic shifts--that is, unless growing isolationism leads us to close ourselves off just as openness becomes more critical to our survival than ever.

Rigorously researched and deeply compelling, Empty Planet offers a vision of a future that we can no longer prevent--but one that we can shape, if we choose.

To read an excerpt or buy a copy, please visit: https://www.penguinrandomhouse.com/books/545397/empty-planet-by-darrell-bricker-and-john-ibbitson/

Our guests will be here at 2 PM ET (18 UT). Ask them anything!

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Can daily sunscreen use make you more vulnerable to the sun?

Posted: 03 Mar 2019 08:16 PM PST

It is to my understanding that UVA radiation is what triggers melanocytes to produce melanin. My skin is relatively tan naturally and growing up (Los Angeles) I rarely applied sunblock and never got burned. When I was 18 i started working outdoors for 9 hours at a time and noticed I began to develop sun burns; as a result, I did some googling and started applying sun block daily. Its been about a year now since I started applying daily sun block and it seems as if any day I don't apply it my skin burns. Growing up I could go hours and hours in the sun without being burnt and now I burn incredibly quickly. Is this a result of permanent damage done to my skin through the years or is this a result of my daily use of sunblock preventing melanocytes from producing the bodies natural sun block, melanin?

tl;dr Does sunblock prevent melanin from forming, therefore, making you weaker to the sun when you do not apply sunblock

submitted by /u/CMCarbon
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What is a topological material?

Posted: 04 Mar 2019 03:10 AM PST

I saw this article and I have no idea what's going on. I tried to figure it out by looking stuff up, but it still escapes me.

https://www.reddit.com/r/EverythingScience/comments/ax54l4/ubiquity_of_topological_materials_revealed_in/

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Are Thymine, Adenine, Guanine, and Cytosine present/used in DNA of all living organisms on earth?

Posted: 03 Mar 2019 08:49 PM PST

Are there any organisms anywhere that dont use ATCG DNA or a variation of it?

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How well is chemistry understood? Can we predict the properties of elements and molecules just by the rules of chemistry?

Posted: 04 Mar 2019 07:06 AM PST

Like do we know why the properties of elements are why they are?

Lets say you would teach someone without prior knowledge all we know about chemistry, could he predict the color, hardness etc of a given element or compound? would he know that gold is, well golden and not, say, blue?

Or ist that still a mystery?

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How safe is it to eat food from the floor?

Posted: 04 Mar 2019 03:53 AM PST

Does cold have diminishing returns, e.g. does -40 degrees generally really feel that much colder than zero degrees?

Posted: 04 Mar 2019 06:55 AM PST

Where does uranium in the ocean water come from?

Posted: 04 Mar 2019 07:53 AM PST

I've read that there are some efforts to extract uranium from seawater, and that it is considered "renewable". Surely that's an exaggeration, as I'm not aware of any element considered to be truly renewable (given that it's destroyed in the fission process).

Do the articles mean that ocean deposits of uranium salts dissolve overt time? Wouldn't these run out eventually?

I'm not considering the practicality of deposits lasting for extreme lengths of time so as to be considered undepletable.

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Is the Oort Cloud considered part of the solar system?

Posted: 04 Mar 2019 06:26 AM PST

How is Plutonium-238 enriched from Uranium-238?

Posted: 04 Mar 2019 05:17 AM PST

I've been trying to find a reliable source to get this information but nothing is conclusive. I know that if you hit U-238 with a deuteron it becomes Neptunium-238 and then that becomes Pu-238 (I'm still unsure if this info is correct). Then i read on some places that its not just Pu-238 but also Pu-239 that are together and that needs to be enriched.

Any help will be appreciated.

Edit: I think my title might be wrong but i'm not sure. Any clarification will he appreciated.

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What is the mechanism of action of endo- and phyto-cannabinoids in treating pain?

Posted: 03 Mar 2019 10:18 PM PST

Tl;dr: Need hard science about cannabinoids and their impact on pain. How they work, why they work, what they do, how well they do it. I'm a scientist, but not a chemist/biologist, so a lot of it goes over my head. Please help!

I have been doing cursory research for a few weeks now, but unfortunately everything I find seems to be 1)locked behind a paywall, 2)using jargon that goes beyond my understanding, or 3)heavily biased one way or another.

How do endocannabinoids work in the body to treat pain, and how do phytocannabinoids trigger those receptors? I've seen plenty at a glance about the CB1 and CB2 receptors, and how anandimide and 2-AG are agonists of those receptors, but what is the difference between the impact? What exactly does an agonist of the CB1/2 receptor do, and why do some cannabinoids induce a "high" and impact appetite while others do not? Also, I have seen a lot about the analgesic effects of cannabidiol (CBD), but it is a mild antagonist of those receptors instead of an agonist; how does it work? Where do the analogues lie between endo- and phyto-cannabinoids?

Thank you guys so much in advance. As you can see, I have a lot of questions on the topic that I'm trying to make specific, so absolutely anything helps including just a basic explanation, but please, please, PLEASE, if you've got sources on the topic, send it my way! If you're a kind soul who's willing to translate the biochemistry in them as well, that'd be even better!

Best,

u/pm_some_good_vibes :)

submitted by /u/pm_some_good_vibes
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What happens to the atmospheric density profile when you double gravity?

Posted: 03 Mar 2019 08:04 PM PST

I'm starting to get extremely frustrated with understanding pressure and how it relates to various atmospheric phenomena. Everything feels so unintuitive. My main struggle right now is finding out how increasing gravity would affect hydrostatic equilibrium and the density profile of the atmosphere. I understand why the following equation holds:

change in pressure/change in height = -density * gravity

but I'm confused about why an increase of gravity leads to a steeper density profile. It seems to me like doubling gravity would just make the force diagram for any parcel of air the same, except with all values doubled, and thus with a doubled pressure gradient. Does anyone have an explanation for why increasing gravity makes the air near the surface denser and the air far aloft far less dense? Is there an intuitive way to think about this? Thanks!

submitted by /u/Braindoesntwork2
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would there be muzzle flash if a firearm was fired in a vacuum?

Posted: 03 Mar 2019 07:12 PM PST

How long would it take for a human being to safely accelerate to 99.9% the speed of light?

Posted: 03 Mar 2019 12:25 PM PST

The question assumes it's possible for physical matter to be accelerated to 99.9% the speed of light. And I mean if somebody was confined to to an airtight spacecraft, so not exposed to the surrounding space.

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What are the known scientific differences between the male and female orgasm?

Posted: 03 Mar 2019 02:25 PM PST

If the Earth moves far and long enough from the sun, would the core freeze? And if so, how long would it take?

Posted: 04 Mar 2019 01:06 AM PST

How is heat death of the universe possible if energy cannot be destroyed?

Posted: 03 Mar 2019 09:00 PM PST

Does this mean all heat and light would be emitted into infinite emptiness?

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How is NADPH+ synthesized Through photosynthesis?

Posted: 04 Mar 2019 06:31 AM PST

Lets start with what I know on my end, briefly. I know that when light of a certain wavelength hits the chlorophyll molecule it gives of a electron sending it down an electron transport system, that uses redox. At the end of this transport it ends up at the cytochrome.

My questions: What does the cytochrome do? ( I see in a depiction of this process that it continues through anotherchlorophyll here: https://en.wikipedia.org/wiki/Photosynthesis under light dependent reactions)

How is the electron in a higher state of energy? (after the chlorophyll absorbs a photon). Is it the electron in a higher orbital? how can that be when its not on a molecul?

How is this energy used for the synthesis of NADPH?

Also, how is the energy from a proton gradiant used for the synthesis of ATP?

I apologize for the confusing structure, but I think i might have some information twisted or just flatout wrong.

submitted by /u/Vepetar
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How does bleach work in that it strips materials of pigment?

Posted: 03 Mar 2019 07:12 PM PST

How is a DNA sample computerized?

Posted: 03 Mar 2019 01:13 PM PST

In other words, what is the process to take a biological sample and convert it to code that can then be stored and analyzed by a computer? For example, what would I have to do a sample of my own cheek cells in order to be able to upload my own DNA profile to GEDmatch?

submitted by /u/PlatypusEgo
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Why is Lake Baikal so deep?

Posted: 04 Mar 2019 06:07 AM PST

What is the difference in carbon the humans created vs. natural?

Posted: 03 Mar 2019 06:47 PM PST

I was watching Cosmos, and Tyson stated that the carbon that humans emit have a distinct signature.

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