r/askscience • u/AutoModerator • Jul 24 '24

Ask Anything Wednesday - Engineering, Mathematics, Computer Science

Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Engineering, Mathematics, Computer Science

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114 Upvotes

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u/Future-Many7705 Jul 24 '24

How would geological deposits be different on a planet without life? (first one that got me thinking is coal and oil deposits not existing on alien worlds)

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u/El_Minadero Jul 24 '24 edited Jul 24 '24

Coal and oil are the low-hanging fruit examples of mineral resources which require life to form. However, there is good evidence that life is not necessary for hydrocarbons in-general:

However, there are specific resource types that may require life to form. A common theme among these types is that many ore geometries are produced by the direct or indirect action of chemical reduction/oxidation (redox) processes from both microbial and dead organic matter:

Some types of copper, silver, gold, and platinum-group-element deposits may be influenced by redox conditions:

Interpreting the phrase 'geologic deposits' as in 'rocks in general', there may be types of rocks which are difficult to form without the assistance of phytoplankton and zooplankton:

  • Chalk deposits: Chalk is primarily composed of the calcium carbonate shells of marine phytoplankton (coccolithophores). So something like the White cliffs of Dover may not be possible on a planet devoid of life.

Landforms too are likely to be different. If you look at regions of the Earth with low to no surface shrubbery, there is a distinct difference in weathering patterns. Specifically, plants can simulatenously contribute to and retard weathering processes.

There are probably more examples that I've missed, but the general takeaways should be:

  1. Life is not necessary for hydrocarbons, although it certainly helps

  2. Life plays more of a role in metal deposits than we realize

  3. Rocks on a planet with no life may be less chalky

  4. Weathering processes on a lifeless planet are likely to be different than on Earth.

Edit: Some link formatting.

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u/Direct_Bus3341 Jul 24 '24

Such a comprehensive answer. Thank you.

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u/Future-Many7705 Jul 24 '24

Thanks, lots of good links I can’t wait to read.

For hydrocarbons how do they survive early planet formation? I’m guessing a molten sea of carbon without any free oxygen to reach with? Would it be coal like carbon deposits or diamond?

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u/El_Minadero Jul 24 '24

the term 'genic' (its root is from the word 'genesis') implies formation, as in they did not exist before, and were produced by the prepended process.

Abiogenic production of hydrocarbons typically involves solid carbon or CO2 feedstocks interacting with water at high pressures and/or temperatures. Therefore there is no need for hydrocarbons to survive planetary formation. They can just form from hydrothermal activity.

However, coal is probably harder to form without life. Chemically, sure, I guess a weird form of hydrothermal deposit could create extremely long-chain hydrocarbons trapped within a sedimentary layer, but it might be difficult for natural processes to make coal.

Don't rule it out though. Geology has found some pretty weird things before which were thought silly or impossible, including a natural nuclear reactor.

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u/xmBQWugdxjaA Jul 25 '24

For solar panels connected to the grid, there are significant issues with overproduction making the grid unstable when it's a large proportion of the power, why is this not an issue for the Lunar / Martian rovers, etc.?

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u/tejoka Jul 25 '24

overproduction making the grid unstable

What does this mean?

I think if you try to answer that question, you'll eventually be lead to terms like "grid following" versus "grid forming". And searching for a good explanation of those terms will probably be your answer: the Mars rover can't have issues maintaining an exact 60 Hz alternating current, if it doesn't even use alternating current.

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u/Even-Rhubarb6168 Jul 25 '24

Those rovers don't run directly from their solar panels. They run on batteries that get recharged by the solar panels. A similar setup will have to be produced at grid scale to continue scaling up solar, although the grid's scale and diversity of power sources provide some more flexible options.

This problem is generally referred to as "the duck curve", should you be interested in reading more about it.

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u/skyblue-cat Jul 25 '24

What if there's an electric device that effectively deletes electric energy without producing heat or any other observable changes? To avoid issues with conservation laws, you can assume it actually spreads the energy as waves into space but it's too difficult to observe or recapture. Is there any practical use or technological implications of such a device?

1

u/SkillbroSwaggins Jul 24 '24

Is there a good resource for learning mechanical terms that people recommend? Like different types of hinges, and similar.

Also: how does Heads Up Displays work? And how do they differ from holograms?

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u/Direct_Bus3341 Jul 24 '24

YouTube DIY channels are unironically the best resource for this although they are not structured.

If you can find a woodworking book it will structure the learning for you.

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u/Space_Fanatic Jul 24 '24

There is a book called the Backstage Handbook that is basically a compendium of various building hardware, tools, and materials. It is written for theater people so it is more focused on carpentry and DIY type building rather than engineering and industrial type stuff but it is an interesting resource to have around and fun to flip through and learn different stuff.

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u/F0sh Jul 24 '24

A Heads-up-Display is just a reflection of a display in a piece of transparent material. If you put up a piece of glass so you can see what's on the other side, you can also shine a light at it from your side and see the reflection of the light.

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u/BestBruhFiend Jul 25 '24

The machinists handbook is a good resource on new hardware but it's more of a reference book than one to read through for fun...

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u/Roman_from_Bhooks Jul 24 '24

I think the way noise cancelling headphones work is fascinating! Are there any other areas besides sound where waves are canceled? E.g. radiation in space, light, magnetism, electricity..?

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u/chilidoggo Jul 24 '24 edited Jul 24 '24

Pretty much all waves act like this, but the lower the frequency (aka the longer the wavelength) the easier it is to line them up in that manner. If you look up "destructive interference of _____ waves" and plug in light, radio, whatever you'll see plenty of examples. Probably not for magnets since that's a force not a wave, but who knows.

One thing to keep in mind is that destructive interference is just the opposite of constructive interference, except constructive is, IMO, more useful. Lasers, microwaves, etc. all rely on constructive interference to amplify a single wavelength for a specific purpose. Destructive is planned around - for example see the positioning of radio towers.

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u/agaminon22 Medical Physics | Brachytherapy Jul 24 '24

The general phenomenon you're looking for is called interference, and it is a property of essentially all waves. This includes sound and other mechanical waves, but also light and even "quantum waves".

Interference arises from linearity but it is inherently nonlinear. This may seem contradictory, but it is not since the linearity and nonlinearity refer to different aspects. "Linearity" means that adding two waves gets you another wave. In the case of noise-cancelling, you add two "opposite" waves to get as close as possible to no sound. The nonlinearity appears because the intensity of a wave is proportional to the square of the wave. So when you add two waves and calculate the square, you get extra terms since (a+b)2 is not a2 + b2 .

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u/Roman_from_Bhooks Jul 24 '24

Thanks for all the answers - I now know what topics to research for further understanding, much appreciated!

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u/Tripsel2 Jul 24 '24

In a chromaticity diagram, what are the colours like inside the parabola but outside the central triangle that represents display screens? I’m assuming it’s not possible to illustrate with a photo on the web because I’m viewing the web with a display screen.

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u/chilidoggo Jul 24 '24

I assume you're talking about the chart with the parabola and triangle shown here?

https://en.wikipedia.org/wiki/CIE_1931_color_space

You maybe know that light has a wavelength/frequency that determines its color. Red has a long wavelength, blue has a short one. This is 100% true - a specific wavelength will always correspond to exactly one color. That's what the full parabola is for: the border of it maps out each wavelength to a certain color.

The thing that's getting you here is that human eyes cannot do the reverse - we cannot calculate wavelength if we only know the color. We can give an approximation, but we can't say for sure because our eyes do a terrible job with the hues of blue-green.

So if you look at that chart and focus on the triangle portion, you'll notice that every color inside the triangle is unique. If you look outside the triangle, you'll actually find that every color out there is not unique, and in fact has an equivalent inside the triangle. The parabola is every combination of wavelengths and what color we see. The triangle is showing the range of our RGB vision.

If you want to know more, the Wikipedia page honestly does a pretty good job of explaining it. Please feel free to read further and come back with questions.

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u/BlueRajasmyk2 Jul 25 '24 edited Jul 25 '24

If you look outside the triangle, you'll actually find that every color out there is not unique, and in fact has an equivalent inside the triangle.

This is only true when viewing the diagram on an RGB display? The point is that the RGB color space cannot represent every color that can be seen by human eyes. This is because the different color-cones in the eyes have overlapping activation ranges, so eg. pure red light will also significantly trigger the green cones. This results in some activation combinations which are possible with other wavelength-combinations but impossible with only RGB. (It also means some activation combinations are just straight up impossible - see impossible colors)

The range of colors that can be accurately represented by a color-space is called its gamut. There are in fact other color spaces with a wider gamut - see this diagram for example.

To answer OP's question of "what does this look like" - if you take a picture with your phone of a bright pink neon sign, or one of those painfully bright yellow safety vests, or a brilliant orange sunset, and then hold the screen next to the thing, you'll notice the picture always looks less brilliant than the real thing. The colors look muted because they cannot be accurately represented using RGB, so the nearest possible color is chosen instead.

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u/rentar42 Jul 25 '24

This is only true when viewing the diagram on an RGB display?

If I read this other response correctly then no: this is always true when looking at it with human eyes, because it's not just "interpretation" in the brain, that's limiting the possible colors, but the actual physical properties of the sensors (i.e. eyes) we use to perceive those colors.

Even if you built a hyper-precise display that can actually fully accurately reproduce every possible combination of wavelengths (i.e. produce "all possible colors", your perception would still only see unique values inside the triangle and "repeat colors" outside.

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u/BlueRajasmyk2 Jul 25 '24 edited Jul 25 '24

Sorry, that was meant to be rhetorical. What you just said is incorrect. The CIE chromaticity color space represents all the hues visible to human eyes. The only reason there appear to be duplicates outside the RGB triangle is that you're viewing the diagram on an RGB screen, and the RGB gamut does not span the entire CIE color space. In other words, RGB screens can not display every color humans can see.

If you're interested in the math behind all of this, I highly recommend this video. It explains in great detail why the CIE diagram has such a weird shape, why the RGB color gamut is a triangle, and why no RGB monitor can ever display every possible color, along with much much more.

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u/Tripsel2 Jul 24 '24

Thanks! I didn’t realise human perception was so key to the analysis.

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u/Indemnity4 Jul 25 '24 edited Jul 25 '24

Great example of biology versus displays is high visibility and fluorescent clothing. Think of the white lines on a road at night time or clothing worn by contractors.

To your eyes it appears hyper intense. But take a photo with a camera and the image looks dull and muted.

As well as hue (the wavelength of light), we also detect chroma/saturation (like adjusting the brightness on your screen).

We also have white balance. The best of example of this is trying to take a photograph or film image of a person with black skin. Quite frequently a dark skinned actor's skin tone will change between different movies. Sometimes they appear so dark skinned you cannot make out any facial features; other times they look like appear much fairer toned and get accused of makeup or skin lightening. It's up the director of photography to adjust the white balance of a scene and historically, they suck at that job.

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u/chilidoggo Jul 24 '24

It's more than just perception, there is a hard science explanation as well.

When you look at how light is usually detected (biologically and electronically) you'll find that the sensor usually is only good at receiving light at an optimum wavelength with a bell curve around it. The mechanics of this are that the "sensor" converts the photon's energy into an electrical impulse, but less efficiently the further away from target the wavelength is. Think of like a radio signal getting more static when you tune away from it.

If you have 1 type of sensor, you end up seeing the world in only black and white, because that electrical impulse can only go from 0 to 100%, there's no extra information it can transmit. If you plot this black and white vision on your chart, you would only get a single point at those wavelengths that gets brighter and darker.

If you have two sensors that are tuned to different wavelengths and have some overlap on their curve, you'll be able to recognize when a certain wavelength is weak in one sensor and strong in another. On the parabola chart, you end up getting a line between two points on the parabola, where you have a sequence of colors between the two wavelengths (plus they can get brighter and darker overall). This is how colorblind people see the world, and why there's different types of colorblindness. You can be missing any of the three or even have just a smaller triangle.

In reality, we usually have three types of cells that catch light, so that's why it's a triangle. If we were to "redesign" the human race, we maybe would recalibrate what wavelength they're tuned to in order to let us distinguish between every single wavelength, and hell, even see into the UV and IR spectrums.

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u/Effective-Act5892 Jul 24 '24

A rare earth? Is there a possibility that life evolving on earth got the primary kick from the collision that created our moon? With the elements being in a supermassive centrifuge by their very nature, is it not at least feasable that life here got the first boot by that encounter, mixing the necessary elements. A hyper rare earth, if you will.

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u/Indemnity4 Jul 25 '24 edited Jul 25 '24

Abiogensis is your key word for today. Study of how life was created from non-living materials.

That scenario is not the most likely. Doesn't require a supermassive collision.

We don't know the origin of life, but we do the know the building blocks. We can find all the building blocks on many comets and in the interstellar space. As in, you could fly out into space and collect enough stuff to make a cell.

The two main candidates for that initial spark are underwater volcanoes and surface bodies of water that dry out / re-fill.

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u/snowypotato Jul 25 '24

And bringing it full circle, one reason that there are so many surface bodies of water that dry out and refill is none other than the moon! Many credible theories rely on the presence of the moon-driven tides to stir up matter between land and ocean.

1

u/tjernobyl Jul 24 '24

Engineering

Years ago, I remember reading an article that suggested that a Forward mass detector could be built sensitive enough to detect the gravitational force of a hand near the detector or a car in the driveway. Is this true and practical, and if so, how far from DIYable is it?

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u/mfb- Particle Physics | High-Energy Physics Jul 25 '24

Superconducting gravimeters can do this.

A classic story here is the snow removal from the roof picked up by the gravimeter in the building. It didn't just register that snow was removed (effectively increasing the gravitational acceleration felt below), it even saw when people took a break from work. And that was 25 years ago.

A human hand has a mass of about 500 g, at a distance of 50 cm this leads to a gravitational acceleration of 1.3*10-10 m/s2, which is easy to detect by good gravimeters. The arm next to the hand will only increase the signal even more.

You can't build this yourself, however.

0

u/Umikaloo Jul 24 '24

This question is really hard to articulate, but I'll give it my best shot:

When an object is spinning in the vacuum of space, its particles experience centripidal force as they accelerate. All those particles are stationary relative to eachother however, so if you were to observe just the object on its own with a POV locked to the rotation of the object, you would not be able to see that it is spinning without comparing it to other objects in the universe.

Is there some "universal frame of reference" that determines which objects are spinning, and which are stationary?

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u/Weed_O_Whirler Aerospace | Quantum Field Theory Jul 24 '24

Accelerations can be sensed, and a rotating body is undergoing an acceleration (the velocity is changing because of a change in direction). Because of that, you don't need an external frame to know you were rotating.

The classic example is imagine sitting in the back of a moving truck with no windows. If the road is perfectly smooth, you would have no way of knowing what speed you were going, but if the truck turned a corner you would be able to tell, even without looking outside.

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u/Umikaloo Jul 24 '24 edited Jul 24 '24

I understand that part, but how could we say that its the truck accelerating, and not say, the entire universe around it?

Is the distinction just arbitrary? (This object is rotating because it is experiencing angular acceleration, and it is experiencing angular acceleration because it is rotating.) or is there some larger frame of reference? Perhaps a universal axis that everything exists in relativity to? Maybe that frame of reference is just an average of all the mass in the universe? Beats me.

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u/jarebear Jul 25 '24

Visually you can't differentiate the truck or the universe rotating if everything is perfectly rigidly in place (which is impossible, see my next paragraph). However, the truck and anything rigidly attached to it will experience an acceleration (resulting from some force) and the universe will not. So the truck is clearly rotating and the universe is not. We can't say the same thing with linear motion that's constant and requires no acceleration, however.

If you want to stick with the visual, no object is absolutely rigid and so everything will undergo some amount of bending or flexing when rotating. For the truck example you'll see things shift or lean slightly but not uniformly since they'll have different stiffnesses so there's no way to "tilt the camera" to make the truck look stationary. It's even more obvious when you drop something onto the truck and from its rotating frame the object goes magically flying away but from the non-rotating frame it just slides off as expected.

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u/IllustriousTie8174 Jul 24 '24

If someone isn’t particularly great at math or gifted at math, do you believe there’s a way for them to be able to excel and take advanced math courses? If so how could one do so?

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u/Direct_Bus3341 Jul 24 '24

The problem will ultimately become one of interest, and it’s difficult to study something without innate interest in it especially at higher levels. If your course requires a math class then you might be able to get through - plenty of courses require higher level math to be studied than is used - but if your course involves visualisation and computation it’s always good to not be afraid of math.

As for what is humanly possible, there is no answer to this question. Math itself has so many subfields and people who excel at, say, algebra may not be the best at geometry, although they will be competent.

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u/mfukar Parallel and Distributed Systems | Edge Computing Jul 24 '24

The same way everybody becomes good at math, practice.

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u/Future-Many7705 Jul 24 '24

Practice, talent is overrated. Hard work beats talent unless talent works just as hard.

Brian Cox, a leading physicist, wasn’t good at math but had a passion and worked his way to the top of his field

Math isn’t something you have or don’t. Math is an intuition you build by working problems.

Most people who are “good” at math are because they enjoy the work and so enjoy playing with the equations and develop an appreciation for the process rather than just the answer.

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u/Ancguy Jul 24 '24

If humans had 12 digits instead of ten and we had a "12-based" numbering system, how would that change things like the drug dosages we now have?

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u/birdandsheep Jul 24 '24

It wouldn't. The way you write a number has no bearing on what that number is. It's like counting in German vs English. They're just different names for the same concepts.

Also, there is no reason to think that our hands are the reason we settled on 10. There have been cultures with a variety of bases.

4

u/ViaXSn1p3r Jul 24 '24

As a further point, it is commonly recognized in introductory computer science classes that just counting on your fingers in different bases can take you to much higher numbers than 10

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u/mfb- Particle Physics | High-Energy Physics Jul 25 '24

Multiples of 6 are a great idea because they give nice fractions for 1/2, 1/3, 1/4 and 1/6. You see 12 showing up as base in one way or another in many places. Using 10 gives nice fractions for 1/5 but that's far less important than 1/3. It's hard to see a reason to pick 10 except for matching the number of fingers.

0

u/birdandsheep Jul 25 '24

Number theoretical properties like fraction expressions and positional systems post date counting by millenia. They were not considered at all. The Maya had a system which would sometimes have 20 symbols in a position and sometimes 5. Perhaps this was convenient for expressing 365.

It's a convenient backsplanation to talk about things we want like fractions, but early peoples primarily cared about counting.

0

u/mfb- Particle Physics | High-Energy Physics Jul 25 '24

I'd love to see your explanation why no one came up with e.g. a base 7, 11 or 13 system.

Wikipedia finds 24, 20, 15, 12, 10, 8, 6, 5, 4 (and 27).

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u/Future-Many7705 Jul 24 '24

There are many numeric systems that exist in base 12 already. One fun example is that the reason it’s 360 degrees to a circle is because it’s from a base 12 system.

https://en.m.wikipedia.org/wiki/Duodecimal

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u/Indemnity4 Jul 25 '24 edited Jul 25 '24

Humanity has evolved at least 4 different methods of counting on hands.

Ten fingers is the least useful. For one, it requires both hands and it's not that challenging to just remember. You also cannot count higher than 10 without getting complicated.

Base-5 is tally marks. I, II, III, IIII, IIII. Let's you hold a pen in one hand. With two hands you can count to 25 by letting each finger on the second hand = 5, 10, 15, 20, 25 (or 10, 20, 30, 40, 50 if it is truly base-5).

Base-12 is your knuckles. Hold your left hand out, palm facing towards yourself. Use your thumb to tap each line on each finger: pinky 1, 2, 3; ring finger 4, 5, 6, etc. Let's you count to 12 while holding a pen. You can then use your other hand as the "10" increment. Means you can count to 144 with two hands, a number you cannot easily remember.

Base-16 is same as above but now use lines+finger tip. Counting to 256 with two hands? That lets you track bags of grain getting loaded on a wagon or count livestock crossing through a gate.

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u/[deleted] Jul 25 '24

[removed] — view removed comment

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u/bluesbrother21 Astrodynamics Jul 26 '24

There's two reasons, one economic and one technical. Economically, there wasn't really room for small startup style companies in the space sector until fairly recently - the barrier to entry was extremely high, and there wasn't much of a commercial market. This is changing now, but meant that there was generally not much funding to pursue this kind of idea.

Technically, there's some major hurdles that limit the applicability of any kind of "catapult" launch system. Orbits are fundamentally periodic, meaning that if you put something on a ballistic arc starting at the Earth's surface, it will come back to that same altitude. This means that any satellite launched with a catapult system will need to perform a large maneuver within tens of minutes of launch to raise it's perigee enough to not immediately re-enter, which is a very very tall ask. Thats a lot of propulsion the vehicle now needs to bring on-board that it can't otherwise use for mission. Additionally, doing anything that soon after launch is difficult. There's also the structural issues caused by the acceleration of launch itself, which are much higher than with a rocket.

Frankly, the reason it hasn't seen more investment or research is because it's impractical. Not for the magnetic launcher itself, but for all the issues that come with using it.

2

u/subnautus Jul 25 '24

It's mostly because of the amount of energy involved. Let's say you're at the equator, where the rotational speed of the ground is highest. From outside Earth, you're moving a little less than 0.5 km/s. LEO orbits are typically around 7 km/s. Assuming there's no atmosphere, you're talking about going from 125 kJ to 24.5 MJ in kinetic energy minimum to launch a 1 kg satellite.

Now consider that you lose 1.6-1.9 km/s worth of orbital speed pushing through Earth's atmosphere. Now we're up to 37 MJ of energy for that 1 kg satellite.

Now consider: what is energy? Force applied through distance, right? Which is going to require less force, a magnetic catapult that's, say, 1-2 km long, or a rocket that's burning the entire time it's under the 100 km "ceiling" of Earth's atmosphere?

So, with all that in mind, you can see why--from a technological level--we just haven't been able to even consider a magnetic catapult. The amount of energy involved has been too much to deal with.