Wikipedia:Reference desk/Archives/Science/2016 April 1

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April 1

are we inside a black hole?

the schwarzschild radius of the observable universe is like 13 billion light years. there's a lot of dark matter too, could we be inside a huge black hole? if we were though, wouldn't one side of the universe (the side facing the center of mass) be completely black to us?— Preceding unsigned comment added by 203.213.116.10 (talk • contribs)

You appear to have answered your own question. Beyond that, all we could do is provide you with references (if they exist) that suggest we're in a black hole or attempt to explain why there wouldn't be a huge black spot. We can't really answer questions, just repeat answers that already exist. Ian.thomson (talk) 02:03, 1 April 2016 (UTC)

Sort of like a black hole does. Shock Brigade Harvester Boris (talk) 02:04, 1 April 2016 (UTC)

Well, I think the best evidence that we aren't inside a black hole is that the universe appears not to be contracting, but expanding, and not only expanding, but the rate of expansion is increasing. Secondly, I'm not sure you could explain the Cosmic microwave background from inside a black hole. Vespine (talk) 04:06, 1 April 2016 (UTC)

I think it is possible to have a standard cosmological spacetime with a finite total volume and mass, surrounded by an infinite Schwarzschild vacuum. Possibly if the matter recollapses, then it's inside the Schwarzschild radius, but I may be misremembering. This is sort of like a "universe inside a black hole", but I don't know what sort of process would produce it, and the evidence doesn't support a recollapsing universe anyway.

One side of the universe wouldn't be completely black. It would look almost the same as the actual world (including the CMB), and it would be almost the same, unless we were close to the edge of the matter region (and if the matter region is large enough, the chance of that is negligible).

In a recollapsing universe, you eventually hit a curvature singularity no matter what you do. The collapse is sometimes described as a "union of black holes." If you can't avoid ending up in a black hole, then by definition you're already in it. So maybe recollapsing universes are "inside a black hole" by definition, even without the surrounding Schwarzschild vacuum. -- BenRG (talk) 07:33, 1 April 2016 (UTC)

As said above we don't seem to be in one because the rate of expansion is increasing. I don't know what being inside a white hole would be like but perhaps this is it. Dmcq (talk) 11:51, 1 April 2016 (UTC)

Hearing loss from music performance

(Professional advice disclaimer noted.)

http://www.bbc.co.uk/news/entertainment-arts-35938704

"A renowned viola player is suing the Royal Opera House for ruining his hearing and his career during rehearsals of Wagner's Die Walkure."

Does anyone here know of any papers on what the type of injury is likely to be? ShakespeareFan00 (talk) 10:21, 1 April 2016 (UTC)

The news report you linked to says Acoustic shock. Our article doesn't include any papers but a search should find ones like [1] [2] [3] [4] [5] [6] [7]. These in turn link to other research. Stuff like [8] may also be relevant. Nil Einne (talk) 12:11, 1 April 2016 (UTC)

The thread title is far different from the specific question. The Royal Opera House musician claimed that loud music during one set of rehearsals for one piece had caused this "acoustic shock" similar to a syndrome experienced by call center personnel in India whose headphones had squeals or were generally loud. This is despite his having been provided with hearing protection which reduced the sound pressure level by 28 dB, which is close to the best protection obtainable via earplugs or over-ear protectors. The claimed syndrome rather than rendering him unable to hear soft noises caused him to have psychological trauma when he heard a variety of sounds, such as his infant, or random household noises. The more common manifestation of actual "hearing LOSS from musical performance" is that the 130dB or whatever from combined percussion and brass in an orchestra or band causes lower hearing sensitivity at some frequencies, or causes tinnitus which interferes with hearing, as reported in a study from Michigan State University, which reported 71% of the Chicago Symphony musicians had experienced hearing loss. Some classical or popular musicians use special earplugs by companies such as Etymotic Research mentioned in a journal article which are supposed to let them hear the ensemble better than standard industrial hearing protection. Even in high school bands, having a number of trumpets playing a few feet behind one is painful and likely damaging to hearing. Studies with rats show that loud noise literally destroys permanently the "hair cells" in the cochlea which are the sensory receptors for sound. Edison (talk) 17:07, 1 April 2016 (UTC)

Comment: This is a bit of an aside as I don't know of any scientific studies -which is what the OP is seeking. I sometimes used to get asked to stand in for a sick band member. With a stack of Marshal amps behind me, the only way I could hear my contribution (which was why I was there) was to listen to a on-stage speaker such as this in front of me. Therefore, I think the ambient noise level can reach a point where ones hearing gets too overloaded. Rather than resort to wearing wax ear plugs (which attenuated too much, some of the frequency I wanted to hear) I stood on stage with ear defenders. To make it look like a stage act, I added curly wire antennas to them with little balls at the end. Whether this particular musician is suffering hearing lose due to his employment or whether its due to natural hearing loss that he would suffer regardless -I do not know. Yet, I can't help but notice when I bump into some of my old chums, many now need hearing aids. Some have further admitted, that they where still in their very early twenties when they first noticed hearing loss. But because they could afford a sound mixer at gigs and in the studio, it did not bother them too much at the time. But such is the isolation and frustration they now experience in their 60's and 70's, when trying to follow any of their grandchildren's conservations, they wish they knew then, what they know now. Food for thought. --Aspro (talk) 13:07, 2 April 2016 (UTC)

Nuclear renewable energy

What is the relation between the nuclear energy and renewable energy?--5.2.200.163 (talk) 15:06, 1 April 2016 (UTC)

They both contain the word "energy". --Jayron32 15:09, 1 April 2016 (UTC)

Thats a pretty fececious remark J. Below your station I suggest. Why not try to be helpful?--178.101.224.162 (talk) 23:57, 1 April 2016 (UTC)

Nuclear energy is in no way "renewable". The fuels that it uses (uranium, for example) are mined and will eventually run out just like coal and oil. Even fusion power requires materials like Deuterium that are not "renewable" (at least not rapidly).

The closest relationship I could imagine between nuclear power and true renewables (such as wind, wave and solar power) is that nuclear energy could provide a stop-gap measure as we phase out hydrocarbon fuels and phase in those true renewables.

Nuclear fission reactors cannot be a long-term solution to mankind's energy needs.

SteveBaker (talk) 15:44, 1 April 2016 (UTC)

I'm not deliberately trying to be facetious, but why are wind, wave, and solar power "renewable"? They depend on a unidirectional flow of solar energy. Over a sufficiently long time, the sun will consume all of its hydrogen, and that's a one-way trip. It will take billions and billions and billions of years before a new cluster of hydrogen coalesces under its own gravity, collapses into a core, and reaches critical mass-density to sustain hydrogen fusion inside a new sun. Eventually, over the timescales of tens or hundreds of billions of years, the universe will run out of free hydrogen from which we can form more stars.

Meanwhile, fossil fuels only take a few million years to collect a large quantity of biological kerogen, and then a few more million years to cook into useful petroleum, gas, and other fossil fuel. On geological timescales, fossil fuels form really fast. We can renew our fossil fuel resources much faster timescales than we can renew the hydrogen-resources that fuel our sun. The only downside is that nobody in present company will survive long enough to wait for the next batch to come out of the proverbial geological oven.

The terminology "renewable resource" refers to a renewal process that happens within a specific timeframe. Most of the time, that timescale is compared to the characteristic life-cycle of a human, or a group of humans.

Depending on how far out you're thinking, though, no energy source is renewable: our universe is on a steady march governed by the laws of thermodynamics, paraphrased thusly: (1) you can't win; (2) you can't break even; (3) you're guaranteed to lose.

If we're speaking purely in terms of physics, solar energy (and wind energy, and so on) are not renewable. Their actual advantage has nothing to do with the fact that they're renewable. They really have advantages because they are (potentially) low cost; (potentially) low-polluting; (potentially) low ecological impact; and because to first order approximation, they provide an "approximately" infinity-sized hot-bath reservoir for the enormous Carnot engine that is human society. None of those advantages have anything to do with "renewability." Don't get me wrong - I'm a huge fan of hydroelectric power generation, wind power generation, and so forth ... but I think we should be pitching for these excellent alternative sources of energy on their real merits, not their illusory merits.

Nimur (talk) 16:46, 1 April 2016 (UTC)

Not since Protagoras laid the touchstone for the Age of Enlightenment in his words "Man is the measure of all things" should anyone need apologise, or be mocked by a pedant, for qualifying renewable energy sources as those which are naturally replenished on a human timescale. The writers of ISO 13602-1:2002 are not pitching an illusion when they state that a renewable resource is "a natural resource for which the ratio of the creation of the natural resource to the output of that resource from nature to the technosphere is equal to or greater than one". AllBestFaith (talk) 20:38, 3 April 2016 (UTC)

1) Nuclear energy could last us for a very long time before we run out of uranium. That's not technically "renewable", but what we really care about is having an energy supply that lasts so long we don't need to worry about it running out, and it qualifies in that case. According to our peak uranium article "The identified resource at the start of 2013 was enough to supply reactors at current consumption rates for more than 120 years, even if no additional uranium deposits are discovered in the meantime." And, of course, there are many undiscovered reserves and even the possibility of extracting it from sea water at some point in the future. As with most natural resources, the higher the price goes, the more can be produced, since the less accessible reserves can then be accessed, at higher costs. However, unlike other natural resources, the price of uranium has little to do with the cost of the energy produced by it. That's because a huge amount of energy is produced by a very small amount or uranium, and most of the cost of the energy is due to the construction, operation, and maintenance cost of the reactor, transmission costs, etc.

2) Breeder reactors may possibly be used to make fuel for nuclear reactors, from other radioactive materials. Of course, those radioactive materials might themselves eventually be used up.

3) Nuclear fusion reactors should one day provide even more energy.

So, by combining these, we have centuries of nuclear energy available. It may, ironically, last longer than some actual renewable energy sources, like wood. This is because, if we were all to burn wood to provide energy, we would use it up faster than we could grow new wood. Then there would also be massive pollution created by burning all that wood. StuRat (talk) 16:32, 1 April 2016 (UTC)

How about radioisotope thermoelectric generators, how do they fit in in this context? And also isotope and elements regeneration by neutron capture and beta decay?--5.2.200.163 (talk) 16:39, 1 April 2016 (UTC)

Reply to first first question: Doesn't really fit in at all. Those portable devices are comparable to a can of Sterno used for camping. That is, the amount of energy produced by them is totally insignificant in the overall picture. (We could in theory each have a portable nuclear generator, but the risk or accidents and terrorism is just too high to do that.) StuRat (talk) 16:47, 1 April 2016 (UTC)

There are small modular reactors waiting to be used. It seems that also aqueous homogeneous reactors can be made portable.--5.2.200.163 (talk) 10:32, 5 April 2016 (UTC)

Nuclear energy is off the charts clean per unit energy created..."renewable energy"20:06, 2 April 2016 (UTC)68.48.241.158 (talk) is not particularly clean per unit of energy created if look at all the infrastructure and maintenance costs etc etc etc...nuclear power plants are basically capable of powering entire metropolitan areas by themselves....the downside is the small chance of catastrophic disaster, and dangerous waste products etc..there's no efficient manner of storing large quantities of energy either so when the sun doesn't shine and the wind doesn't blow etc, renewables are useless...68.48.241.158 (talk) 19:24, 2 April 2016 (UTC)

They just need to take my advice and build nuclear reactors deep in abandoned mines, in stable geologic areas, far from population centers, so they can just push the nuclear waste they generate into an already constructed concrete bunker at the end of the mine, rather than hoping to ship it across the country some day to a nuclear waste storage facility that has yet to be built. The cooling towers would still be on the surface, and they would need high tension wires to send the electricity to cities. If they did have a meltdown, they would just evacuate the mine and bury it in concrete. If the reactors survived to their projected lifespan, they would again bury the mine in concrete, and would only need to post a few guards, since drilling through all that concrete to get to the nuclear waste would take terrorists way too long to go unnoticed. StuRat (talk) 19:34, 2 April 2016 (UTC)

I'm no expert but I'd imagine there's all kinds of technical difficulties in what you propose, might hugely increase the cost of nuclear power, defeating the purpose..just dealing with the hydrology needed underground... 68.48.241.158 (talk) 20:06, 2 April 2016 (UTC)

The problem with the mine idea is, mines tend to flood, so any reactor placed in an abandoned mine would be under water in short order. Generation 4 and later reactors are being designed as "walk away safe", where one could quite literally walk away from the reactor and it wouldn't melt down. Add thorium into the equation of nuclear reactors, nuclear waste (depleted uranium) is "burned" in the reactor, leaving little waste at the end of the fuel cycle and that waste would only be radioactive for a few hundred to a few thousand years. That's a whole lot less than what waste we have now, being dangerous for hundreds of thousands of years. But, for more renewable (nuclear isn't renewable at all, once you run out of fissionables, you're out), fusion power would be the way to go. Alas, we've yet to get gain in fusion, all fusion processes currently operate at a loss - more energy going in than being generated. Solar is nice, however heavily polluting in making the solar cells and storage batteries and highly inefficient (top of the line solar cells are only around 10% efficient). Wind is nice, when there's wind. Tidal power is workable, if disruptive to shorelines. Every technology has its strengths and weaknesses, as TANSTAAFL.Wzrd1 (talk) 20:51, 2 April 2016 (UTC)

Try mines in deserts to avoid flooding. The opening can be sealed while in operation, too. I am aware that nuclear fission can be done safely, but the problem is that we must rely on large corporations and government agencies to ensure that they are safe, and nobody much trusts them to keep us safe anymore. So, to get public support, we need to move them to some place where we don't have to trust people who have proven they can't be trusted. StuRat (talk) 22:04, 2 April 2016 (UTC)

You are aware that there are underground aquifers even in dessert regions, and that (almost?) all deep mines need active water level management, right? That was what Newcomen atmospheric engine was first used for when we seriously started this hole fossil fuel business. --Stephan Schulz (talk) 15:58, 5 April 2016 (UTC)

The reactor doesn't have to be particularly deep, just deep enough so that any explosions won't escape to the atmosphere. Hopefully that would put it above the water level in a dessert. Another option might be a mine inside a mountain. StuRat (talk) 16:47, 5 April 2016 (UTC)

Nuclear power proposed as renewable energy might be the answer to the OP's question.--Heron (talk) 09:18, 3 April 2016 (UTC)

I had noticed it and intended to mention here.--5.2.200.163 (talk) 10:30, 5 April 2016 (UTC)

Radium mixed with uranium

If radium is mixed with uranium in a container, is the halflife of the uranium decreased? By a lot, or hardly measurably?Eva M. Kahn (talk) 20:01, 1 April 2016 (UTC)

Outside of certain unusual environments such as the interior of stars, nothing changes the halflife of any element. --Guy Macon (talk) 20:05, 1 April 2016 (UTC)

(ec)No, radioactive decay, to an excellent approximation, is completely unaffected by external chemical or physical processes. There are some possible quibbles (especially for unusual decay modes like K-capture, which doesn't apply to uranium), but at any level you're likely to care about, the decay of the uranium is unaffected. --Trovatore (talk)

I was just about to correct myself. See Radioactive decay#Changing decay rates. --Guy Macon (talk) 20:09, 1 April 2016 (UTC)

I suspect you are confusing two different things. The half-life refers to it's tendency to decay all on it's own. You can, however, cause it to undergo nuclear reactions quicker than that, by exposing it to various forms of radiation. A nuclear explosion is the ultimate example of this. StuRat (talk) 20:16, 1 April 2016 (UTC)

I'm wondering if the OP has read about reactors that can burn nuclear waste. In this case, many of the radioactive isotopes – (combined with other fuel which maintains a high neutron flux) are fissioned well before there normal half-life expectancy.--Aspro (talk) 14:36, 2 April 2016 (UTC)

That's not changing the half-life of the nuclides — it's transmuting them into different nuclides that have different half-lives. But I agree it's possible that that's what Eva M. Kahn had in mind.

If that's the idea, then adding radium is not likely to work well. Radium is an alpha emitter, and what you want is neutrons. But in any case you're generally not trying to get rid of uranium, as at least U-238 is so long-lived that it doesn't have much radioactivity. It used to be used to make a bright red-orange glaze for pottery, and it was safe to eat off of. --Trovatore (talk) 19:22, 2 April 2016 (UTC)

That's not strictly true. Uranium painted dishes were safe to eat off of if the glaze remained intact, as the food would never touch the uranium. As for disposing of nuclear waste, one of the selling points for thorium reactors is that one can place depleted uranium into the thorium reactor and it'd "burn" it, leaving short half-life waste. Of course, the shorter the half-life, the more radioactive it is, but it has to be stored for a much shorter amount of time.Wzrd1 (talk) 20:55, 2 April 2016 (UTC)

I don't know why you would want to get rid of depleted uranium. It's useful for all sorts of things, and so slightly radioactive that for most purposes it's not really a problem. Breeder reactors (and perhaps thorium reactors; I haven't heard that but could be true) can use DU to get energy, and that's different of course, but getting rid of the DU is not the purpose. --Trovatore (talk) 21:17, 2 April 2016 (UTC)

True or false? "Winter ice maximums in the arctic are relatively unchanged. Summer minimums are lower."

Is it true that "Winter ice maximums in the arctic are relatively unchanged. Summer minimums are lower." (according to User:DHeyward above). If there is some source of this, it could be interesting to update some articles. --Scicurious (talk) 22:28, 1 April 2016 (UTC)

https://nsidc.org/data/bist/bist.pl?annot=1&legend=1&scale=75&tab_cols=2&tab_rows=2&config=seaice_extent_trends&submit=Refresh&hemis0=N&img0=trnd&hemis1=N&img1=plot&mo0=03&year0=2016&mo1=09&year1=2016 Maximum extent is in March. Min extent is in September. Rate of loss is roughly an order of magnitude difference between max and min. Not sure what articles you think need updating. --DHeyward (talk) 23:16, 1 April 2016 (UTC)

I suppose Polar_ice_cap#North_Pole and Arctic sea ice decline could benefit from this information.--Scicurious (talk) 23:24, 1 April 2016 (UTC)

Take it to WP:RDL, guys. Evan (talk|contribs) 19:07, 3 April 2016 (UTC)
The following discussion has been closed. Please do not modify it.
Just to be pedantic: its minima and maxima. Still, not everyone had the experience of Latin in school.--178.101.224.162 (talk) 00:00, 2 April 2016 (UTC) Just to be pedantic: (1) it's it's; and (2) both plurals are correct for those nouns. This is English, not Latin. --69.159.61.172 (talk) 08:00, 2 April 2016 (UTC) Thats an American dictionary. Not English.--178.101.224.162 (talk) 00:09, 3 April 2016 (UTC) The speak English in the United States. Perhaps you noticed that... --Jayron32 03:28, 3 April 2016 (UTC) Also it's my error: it's it's not its. Glad we cleared that up. The American Heritage dictionary confirms: Its is the possessive form of the pronoun it and is correctly written without an apostrophe: The cat licked its paws. The contraction it's (for it is or it has) should always have an apostrophe: It's the funniest show I've seen in years. TearsOfaClone (talk) 12:00, 2 April 2016 (UTC)

The time series graph on this NSIDC page is probably useful in answering the question. --Tagishsimon (talk) 00:11, 2 April 2016 (UTC)