How do we know that the universe is constantly expanding? | AskScience Blog

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Thursday, June 27, 2019

How do we know that the universe is constantly expanding?

How do we know that the universe is constantly expanding?


How do we know that the universe is constantly expanding?

Posted: 26 Jun 2019 12:48 PM PDT

AskScience AMA Series: I'm Dr. Majdi Osman, an infectious diseases physician and Clinical Program Director at OpenBiome - a nonprofit stool bank that provides material for fecal transplants. Ask me anything!

Posted: 27 Jun 2019 04:00 AM PDT

Today is World Microbiome Day! I'm here to talk about fecal transplants and microbiome research. Fecal transplants are exactly what they sound like - taking stool from a healthy donor, carefully screening it, and transplanting it into a patient.

At OpenBiome, we provide material for fecal transplants to clinicians treating patients with an infection called C. difficile, and we collaborate with researchers around the world investigating the potential of fecal transplants in other conditions, like inflammatory bowel disease, malnutrition, typhoid, food allergies and multiple sclerosis.

Our Executive Director Carolyn Edelstein joined a panel at the Aspen Ideas Festival this weekend on "The Power of Poop" - you can watch it here. You can also check out our work on our website, Facebook, and Twitter. AMA!

I'll be on at 11am ET (15 UT). Ask me anything!

submitted by /u/AskScienceModerator
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How do so many groups in Arabian regions cope with constant desert heat?

Posted: 26 Jun 2019 12:18 PM PDT

I'm wondering more about groups that don't do a lot of trading and are semi-nomadic or completely nomadic. Many people in Arabia have full fabric covering their body, and I understand how that could help in a sandstorm, but what about the heat cooking your body under all that material? I'm sure it protects from sunburn but is it really worth the trade off, or are their clothes somehow cooling them even more? I just don't get it

submitted by /u/TwentyFirstSintury
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If someone is a match for one organ are they a match for all?

Posted: 26 Jun 2019 12:16 PM PDT

I know organ transplants are really finnicky and have a lot of issues with rejection, but I'm curious - if someone is a match for, say, a heart transplant, does that mean they're a match for kidneys too?

submitted by /u/stealthmissionary
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Can Processors Execute both branches of a conditional statement instead of predicting? Would this be faster or slower than the predict-and-reset-if-wrong method currently employed?

Posted: 26 Jun 2019 12:40 PM PDT

According to a book on computer science I am reading, when a conditional statement occurs in code the processor will predict which option will be taken and begin instructions while another part of the processor checks which branch was the correct one, as a way to make better use of parallelism in modern processors. If the processor guesses right it continues on, but if it guessed incorrectly then it has to throw out all the work after the statement and start over from the branch, this time choosing the other path. This incurs a large performance penalty.

I am wondering, is it possible to have the processor execute both branches? Most likely it would be slower than a correct guess in the current method, but it also removes the risk of being wrong. Is this currently employed? Would it require new processor technology that is not feasible currently? Do the prediction mechanisms guess correctly often enough that it would reduce speed to evaluate both branches? Is there another factor that I don't know about?

Thanks in advance!

submitted by /u/Kesseleth
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Why does Osmium, in bulk form, not generate toxic Osmium tetroxide at room temperature?

Posted: 26 Jun 2019 08:29 PM PDT

According to all the information I can find, including some chemistry text-books and "processing guideline" manuals, bulk Osmium is considered generally safe, because it does not produce toxic osmium tetroxide at room temperature (only above 400C). Powdered osmium sponge, on the other hand, transforms into osmium tetroxide at room temperature.

My question is: Why does a block of osmium not constantly form a small amount of osmium tetroxide on its surface?

Osmium tetroxide can't form a protective layer on the surface, as it is a liquid (and it can evaporate), so why is oxidation not continually occurring?

I get that it has less surface area than a powder, but so does a chunk of iron vs iron powder, and iron chunks still rust, hence my confusion.

submitted by /u/Natolx
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Why don't the different gases in the atmosphere separate?

Posted: 26 Jun 2019 12:59 PM PDT

All those gases have different densities, so why isn't the nitrogen (28g/mol) floating on top of the oxygen (32g/mol)? In other words, what keeps our atmosphere homogeneous?

submitted by /u/merdouille44
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How will quantum computers be able current encryption methods?

Posted: 27 Jun 2019 03:55 AM PDT

I have a very basic understanding of what quantum science is and how encryption/hashing works.

I keep seeing various news/blog sites saying that quantum computers will be able to easily break current encryption methods (implied near future)

My understanding of quantum computers is that we can store qubits. These can be a superposition of 1 AND 0, but we still need conventional computers and binary to input data into qubits, and to return the value of the qubits at a given time analogous to opening schroedingers box. The superposition no longer exists and a binary outcome is observed.

Now I also saw someone say that (N qubits = 2N bits) This is incredible scaling but we can't even make a quantum computer that comes close to a conventional computer. We also use conventional computer and binary as input and output even when doing quantum computing... so what is the significance of the qubits anyway? How would any of this break encryption?

If someone could also explain why qubits scale this way - since the output is regular binary? A qubit can be a superposition of 0 and 1 but it can only return one or the other when asked. How does this enable say 3qbits to equal 8bits?

submitted by /u/nekowaiidesu
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How do electrons "know" that the circuit is closed?

Posted: 26 Jun 2019 11:10 PM PDT

Imagine a battery with 2 loose copper wires, attached to each terminal (+) and (-) of a battery.

Connect the loose wire end which comes from the (-) terminal to a light bulb: the light bulb stays turned off. Of course, because there's no current. That means that the electrons inside the wire and the light bulb are not moving.

Now connect the other loose wire end which comes from the (-) terminal to the light bulb, closing in fact the circuit: Magic, the light bulb lights up!

Interpretation:

That means that the electrons inside all the circuit are now moving. But how did the electrons "know" that the circuit is now closed? If we picture the electric current as a water flow: Normally, even connecting the light bulb on only one wire would trigger the light bulb to ignite, even for a brief period of time: the battery is "pushing" the electrons so they are pushed into this new part of the metal which is the light bulb.

And another problem of this imaginary picture: if the battery is pushing the electron, the last element of the circuit (the closest to the (+) battery terminal would be pushed later than the first ones? But in fact, you could have a 10m or a 30cm circuit, all the light bulbs inside the circuit will light up instantly.

submitted by /u/presse_citron
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What is the hottest manmade temperature ever recorded on Earth, and how was it created?

Posted: 26 Jun 2019 04:25 PM PDT

Why does the Earth have a stronger gravitational pull at the poles?

Posted: 26 Jun 2019 10:41 PM PDT

I understand the rotation of the earth creates a relative "force" that goes against gravity and is strongest at the equator, but the earth is wider at the equator because of this. Being wider I would imagine would mean more gravitational force. Shouldn't Earth continue to "flatten" until gravity is fairly universal all over?

submitted by /u/Eatenplace7439
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Why don't photons interact with another ones?

Posted: 26 Jun 2019 09:05 AM PDT

You have some unknown differentiable function from reals to reals and that all functions are equally likely candidates. If you know the output of the function at two inputs, what is the expected output of the function at an input lying on the line between the two known points?

Posted: 27 Jun 2019 12:00 AM PDT

Keeping in mind that any differentiable function is equally likely, I would guess the answer would be the value found by linear interpolation between the two known points. Is my intuition off? I'm also interested in topics to search to answer questions like this because I have no idea where to start.

submitted by /u/save_scummer
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Why does Salt make an open wound sting?

Posted: 26 Jun 2019 01:23 PM PDT

How is antimatter stored?

Posted: 26 Jun 2019 02:42 PM PDT

As the title is. Wouldn't the antimatter collide with matter of a normal container and annihilate? I don't know much about antimatter but I'm interested.

Any help and explanation will be greatly appreciated. Thank you!

submitted by /u/BigManSilverNugget
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Pangaea: How did all the continents end up all crammed together in the first place?

Posted: 26 Jun 2019 08:22 PM PDT

It seems really weird to me that all the above‐water landmasses would start out all clustered together on the same side of the planet, instead of more‐or‐less randomly distributed across the earth's like they are now (except, you know, a different more‐or‐less random distribution, presumably). How did they get that way?

submitted by /u/BrokenEye3
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What is the difference between a coil gun and a rail gun?

Posted: 26 Jun 2019 10:07 PM PDT

the title pretty much says it all. Are they pretty much identical mechanically?

submitted by /u/DukeV22
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How does hyperthermia kill you, biologically speaking?

Posted: 26 Jun 2019 03:57 PM PDT

Looked a bit at the wiki page. It tells you what symptoms you get at various temperatures, and the maximum temperature you can survive in until you're likely to die. But it doesn't go into much detail in regards to the exact biological mechanism that hyperthermia kills you, only that it does.

More curious than anything else. I'm intrigued by the fact that the human body seems to have a very 'narrow' temperature range it can survive in, in both directions.

submitted by /u/MayaFey_
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What's the most accepted hypothesis (or theory) for the cause (not pathology) of autoimmune diseases?

Posted: 26 Jun 2019 11:04 PM PDT

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