# What is Impossible: Definition and 298 Discussions

The Heartfelt is an album by Figurine, released in 2001. It was re-released in 2005.

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1. ### Work greater than heat given to colder reservoir -- impossible?

photo below... Is it possible to make a machine that would take more heat from the hot reservoir to do work than what would hot reservoir give to the cold reservoir(heat)? Apparently, it's impossible because it violates 1st law of thermodynamics. the thickness of the arrows symbolizes the...
2. ### I Why is it Impossible to Solve the Three Body Problem Analytically?

Three (many) body problems where three or many bodies (particles) interact are impossible to solve analytically. First one appeared in classical mechanics where equations of motion of planets were tried to be found by applying Newton's 2nd law for system of planets and stars interacting via...

4. ### Arc length of vector function - the integral seems impossible

The vector equation is ## v(x)=(e^x cos(2x), e^x sin(2x), e^x) ## I know the arc-length formula is ## S=\int_a^b \|v(x)\| \,dx ## I found the derivative from a previous question dealing with this same function, but the when I plug it into the arc-length function I get an integral that I've...
5. ### I Is the existence of a Dyson Sphere impossible?

Specifically a monolithic Dyson Sphere; also, how would a Dyson Swarm work / be a better option?
6. ### Apparently impossible indefinite integral?

Hi guys, I got to solve this integral in a recent test, and literally I had no idea of where to start. I thought about substituting ##tan(\frac{x}{2})=t## in order to apply trigonometry parametric equations, integrating by parts, substituting, but I always found out I was just running in a...
7. ### I Bell's Inequality => 4 entangled Photons impossible?

Correlation between polarization measurements of entangled photons at angles less than 45 are greater than classically statistically possible. No set of hidden variables can be preordained to explain the 75% correlation of photon measurements at 30 degrees and complete anticorrelation of...
8. ### Is this an impossible aspiration for an Electrical/Controls Engineer?

Is there (or will there be) some specific fields or roles within electrical engineering that support the ability to work fully remote? To escape the 9-5, location dependant norm. This could be as a employee, contactor or maybe self employed? More info: my current background includes panel...
9. ### I Shouldn't the Big bang be physically impossible?

I would appreciate if someone could clarify this simple contradiction with the Big Bang. Assume black holes exist, and are caused by the collapse of large quantities of mass due to gravity. The resultant singularity is so massive that not even light can escape, much less material. Yet if the...
10. ### Can you name someone that pulled off a certain impossible feat academically?

Could be someone you know, or someone you heard/read about. By "certain impossible feat academically?" I mean someone who achieved something that is really, really impressive and must be a combination of individual merit, endeavor, talent and of course, luck. Someone for example won the Draper...
11. ### COVID Surely a truly “symptomless superspreader “ of Covid 19 is impossible

When cells get "Hi-jacked" to make new virus particles it usually has a considerable effect on us, and we feel tired and unwell. The so-called "superspreaders " are presumably able to ignore these effects , but they must have them to a lesser degree than usual.
12. ### I Simple, almost "intuitive" conjecture, hard or impossible to solve?

Hello, I have posted a problem (on math stack exchange) I was given for fun by an uncle, who doesn't know whether the proof is possible to establish. I tried my best and failed so far. I don't think I can solve the problem with my current knowledge and I would love to know if you can find a...
13. ### B Impossible to find the quantile of any equation

Given the distribution function $$f(x) = 2xe^{-x^2}$$ The probability density function would then be $$F(x) = -e^{-x^2}$$ To find the .5 quantile I set F(x) = .5 $$.5 = -e^{-x^2}$$ $$ln(-.5) = -x^2$$ And already here we have the issue, you can't take ln of a negative number.

15. ### Engineering Efficiency of Heat Engines & Refrigerators: Is Impossible Possible?

For the heat engine: First I converted all the temperatures to Kelvin, ηmax=1-(333)/(1000)=0.667 ηclaim=(1*10^3)/(1.75*10^3)=0.5714 So the heat engine seems to be less efficient than a Carnot heat engine which means it can exist. For the refrigerator: COPmax=(253)/(363-253)=2.3...
16. ### Welding Machine Increases Power: Physically Impossible?

How is it possible for a welding machine to end up creating more power than what it started with if that is physically impossible? For ex; 200 amp @ 28vdc welding machine. starts out with main voltage being 120v @ 20amps = 2400 watts then converts it to 200 amps at 28vdc which = 5,600 watts of...
17. ### I An integral rewritten (from “Almost impossible integrals“, p.59 in Valean)

I want to understand where the minus 1 in the first line in the RHS term comes from. I assume the little apostrophe means taking a derivative. But the antiderivative of x^(n-1) is (1/n)x^n. Why the -1? thank you
18. ### I How Can Improbability and Infinitesimal Probabilities Exist in Real Life Events?

Distributions with finite variance and infinite support suggest non-zero, but negligible probability of very extreme outcomes. But how small is negligible, and how improbable is actually impossible? For example, the adult male height in the US can be roughly characterized as N~(175, 9) in...
19. ### Isaac Arthur “Things that Shall Never Exist”?

Isaac Arthur is an awesome science populizer and futurist. On August 22nd, his channel is premiering it’s 200th episode titled “Things Which Shall Never Exist”. He will be talking about things that will never be possible to be created. Arthur is pretty optimistic about technology. He predicts we...
20. ### Impossible Relative Velocity Values

The answers were 1) 150 km/h 2) 200 km/h 3 )500 km/h 4) 700 km/h 5) 800 km/h (Chosen Solution) I know that values 700km/h ,100km/h ,-100km/h are possible scenarios but in what ways are 150km/h ,200km/h and 500km/h possible ?
21. ### B Can an Impossible Differential Be Solved in Calculus?

Hey, someone I know told me that the differential dy/dx= 24x/(2x+3) is not possible to solve... Is this true? If not what's the differential for it. This is my first year of calc in high school so my apologies if I butchered some of the terminology.
22. ### Showing that a tiling of a chessboard is impossible

Homework Statement Delete one of the corner squares of a chessboard. Is it possible to cover the remaining area by ##21## dominoes of size ##1 \times 3##? Homework EquationsThe Attempt at a Solution I claim that it is impossible. Here is my attempt to describe my solution in words. Go to the...
23. ### Impossible hydrostatic scenario

Homework Statement There is an infnite high hydrostatic head in an infite high tank on the surface of earth. How big is the pressure p(r) in tank at a distance r. Ignore the rotation of the Earth and assume the water stays liquid. ( So basically ignore it's an impossible scenario )...
24. ### Are space fighters really impossible in realistic Sci Fi?

TL;DR at bottomIt's a somewhat accepted convention that in realistic scifi space fighters should be impossible to use effectively. In general they are regarded as being easy targets that, at interstellar ranges would be unable to survive in a battlefield that employs current plausible scifi...
25. ### A Multiverse theory with impossible universes?

I found an article written by physicist George Ellis that confused me a little. http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.498.4569&rep=rep1&type=pdf At some part, he says: 3.2 Non-uniqueness: Possibilities There is non-uniqueness at both steps. Stating “all that is possible...
26. ### B Exactly why FTLC is impossible with entangled photons?

It’s written almost all physics books and courses that entangled photons can’t be used for faster than light communication. The question about used entangled photons to communicate faster than light has been discussed before, but I didn’t get exactly why faster than light communication with...
27. ### B Math Jokes: 1-1=0, but 2=0? Impossible!

I would like share a nonsense math problem which certainly wrong but its fun I would like others to join as well in my endeavor to create jokes by using math. the joke is as follows As we know, 1-1=0 let, a = 1 , b = 1 then...
28. ### Absolute zero temperature is impossible to achieve?

Just a general musing. Could absolute zero ever be physically possible or is it like the speed of light but for an inverse reason? The speed of light take infinite energy to achieve. So therefore is impossible because the energy put into the system adds mass. This is not noticeable at slower...
29. M

### Coefficients that make Gaussian elimination impossible?

Homework Statement Given this matrix: I am asked to find values of the coefficient of the second value of the third row that would make it impossible to proceed and make elimination break down. Homework Equations Gaussian elimination methods I used given here...
30. ### I Impossible to lift the identity map on the circle

Suppose that L: ##S^1## ---> ##R## is a lift of the identity map of ##S^1##, where e is the covering map from ##R## to ##S^1##, where ##R## is the real numbers and ##S^1## is the circle. Then the equation e * L = ##Id_{S^1}## (where * is composition) means that 2*pi*L is a continuous choice of...
31. ### A Breaking of a local symmetry is impossible, so what about global symmetry....

Breaking of a local symmetry is impossible. It is often said that therefore the role of the Higgs mechanism in the standard model is a different one. Namely, Once a gauge is fixed, however, to remove the redundant degrees of freedom, the remaining (discrete!) global symmetry may undergo...
32. A

### B Is Time Travel Possible? Exploring the Speed of Light and the Nature of Time

I just wanted to share this idea with other people who may be interested: I watched a PBS Space Time episode about the speed of light more accurately described as the speed of causality. And I Submit! That "time" is simply a interaction between atoms. And though an interaction can be...
33. ### A Impossible Curl of a Vector Field

Let's assume the vector field is NOT a gradient field. Are there any restrictions on what the curl of this vector field can be? If so, how can I determine a given curl of a vector field can NEVER be a particular vector function?
34. ### I Is it Impossible for Entanglement > FTL Communication?

Lots of people have wondered about whether we can get FTL communication from entanglement. My question is slightly different. Is it impossible to get FTL communication out of entanglement? If it has been shown to be impossible, then we can shut off the entanglement-FTL avenue altogether and...
35. ### B Is it impossible to prove that some functions are periodic?

Heres an example. Let G(s) be the moving average of all previous values of f(s). G(s) and F(s) intersect at multiple points. Is it possible to prove that the intersections happen periodically?
36. ### B Flaw in my proof of something impossible

Given :- $$g(f(x_1)) = g(f(x_2)) \implies x_1 = x_2$$ Question :- Check whether ##g(x)## is injective or not. Now this is of-course false; counter examples are easy to provide. But I proved that ##g(x)## must be one-one even after knowing the fact it must not. Here is the proof :- Let...
37. ### I Circular Reasoning and Impossible Equation

Suppose there is a problem such that in order to know a variable x, you have to know a variable y. But in order to know variable y, you have to know the variable x. Because of this circular dependency, wouldn't it be impossible to write any sensible equation containing x and y?
38. ### Is this impossible to solve due to lack of information

Homework Statement I came across this question in another forum and the members of the group said it can't be solved due to lack of information. Can anyone solve it? Homework EquationsThe Attempt at a Solution
39. P

### Have you ever fallen in love with a celebrity?

A famous singer, actress or in general a girl who is famous and impossible to be with or meet Same for girls: singer, actor and in general someone impossible to get How did you deal with that? I mean you know it's impossible
40. ### I Impossible to exclude hidden variables without entanglement?

Hi. In most articles on Bell's inequalities, both the reality and locality assumptions are thrown at the reader from the beginning. DrChinese however starts with only the reality assumption and shows that it doesn't comply with QM IF it were possible to measure two non-commuting observables...
41. ### MHB Equivalent Goldbach proof impossible question.

Prove that the number of unordered partitions of an even number 2n into 2 composites is greater than the number of unordered partitions of an odd number 2n+1 into 2 composites for n>1 and n\ne p prime.
42. ### Medical Is it impossible for one to change his habits

i am not asking for a diagnosis or anything , but it it impossible for one to change his bad simple habbits . for example if someone is used in eating like a savage and he does not chew his food , can this person become normal ? and if someone is not organised at all , can this person become an...
43. ### Impossible Op-Amp Circuit....Maybe

Could anyone verify if this is an impossible circuit, I put it in pSpice and it didn't work, I have no op-amps or voltage generators to build the circuit otherwise I would have built it. What do you all think, is it possible to find the transfer function of the far right op-amp? The schematic is...
44. ### Why is two level laser impossible even with non-optical pump

I think I understand why two level laser is not possible if we use optical pumping. However, I don't understand why we can't create laser with two energy levels that are pumped by non optical pump? Why we can't create population inversion that way? For example, if we could somehow pump...
45. ### Impossible Integration involving cosx/sqrt(a-bcosx)

Ok, I have encountered this one a few hours ago: \int \frac{cos x}{\sqrt{a - b cos x}}dx I have tried all techniques I know, integration by part, half-angle formula, substitution, trigo approach, and so on, but it seems, I could not integrate this one. I am no noob in integration, but this one...
46. C

### Absolute zero should be impossible

So since heat comes from atoms vibrating and moving and as they go fast heat increases and when they go slower heat decreases. If I got this right absolute zero is when they give off no heat and this would mean that the atoms are not moving at all. Well then if that is how absolute zero works...
47. ### I Godel's ITs & the Physical World: Is a ToE impossible?

Both Hawking and Dyson have said that Godel's incompleteness theorems prove that it is impossible for us to formulate an absolutely fundamental Theory of Everything. Is that true? Do the theorems apply to the physical world as they apply to the realm of mathematics?
48. ### I Godel's ITs & the Physical World: Is a ToE impossible?

Both Hawking and Dyson have said that Godel's incompleteness theorems prove that it is impossible for us to formulate an absolutely fundamental Theory of Everything. Is that true? Do the theorems apply to the physical world as they apply to the realm of mathematics?
49. ### Dimensionally impossible equation

I was reading some stuff about dimensionally impossible equations. It was said that the equation v = e^bt (b is a constant so that bt is dimensionless) was dimensionally impossible. I understand that BUT I don't understand what they said next about the dimension of the right-side. They said...
50. ### Magnification at a Different Distance from Mirror?

Homework Statement The focal length between a person and his mirror that produces a magnification of 1.50 when his face is 12.0 cm away is 0.36 m. He then moves to a distance of 3.7 times the focal length away from her mirror. What is the magnification now? Homework Equations di/do=m...