Cosmic Expansion

  • Thread starter jeffinchiangmai
  • Start date
Status
Not open for further replies.
J

jeffinchiangmai

Guest
I would like to ask a dumb question. "Since then, dark energy's continuing push has been causing the cosmic expansion to speed up, and it seems likely now that this expansion will continue indefinitely". At what speed does the cosmic expansion reach it's limit in regard to the speed of light? It must eventually stabilize. What happens then?
 
M

MeteorWayne

Guest
Cosmic expansion is the expansion of space itself, so is not limited by the speed of light. The speed of light is the limit traveling through space.
 
J

jeffinchiangmai

Guest
MeteorWayne":hssucyc6 said:
Cosmic expansion is the expansion of space itself, so is not limited by the speed of light. The speed of light is the limit traveling through space.
I knew that. Thanks for your time MeteorWayne. Still learning.....!
 
M

MeteorWayne

Guest
No problem, lots to learn, so little time. Welcome to Space.com!
 
D

DrRocket

Guest
jeffinchiangmai":14tk3r9s said:
I would like to ask a dumb question. "Since then, dark energy's continuing push has been causing the cosmic expansion to speed up, and it seems likely now that this expansion will continue indefinitely". At what speed does the cosmic expansion reach it's limit in regard to the speed of light? It must eventually stabilize. What happens then?
It is a little bit misleading to say that dark energy is causing the acceleration of the cosmic expansion. Data indicates that the expansion is accelerating, and dark energy is simply a hypothesis for that expansion. We don't know what dark energy is or how it might cause an accelerating expansion --- not much of a clue. We do know that if you simply insert a positive constant into the Einstein field equations of general relativity that the result is a model with an accelerating expansion. So dark energy and a cosmological constant are the same thing at this point. Both are just ad hoc ways of modeling accelerating expansion and in a sense are simply another way of sayiing that the expansion is accelerating. Unless and until we get an explanation for dark energy in terms more fundamental than expansion of space-time it really is no more fair to say that dark energy causes expansion than it is to say that expansion causes dark energy.

There is no particularly good reason for the expansion to slow down or to stop. Apparently there is not enough mass to cause gravity to stop the expansion. Unless we later find the data for accelerated expansion to be equivocable.

In order to really answer your question we need to have at least a fundamental explanation for the accelerating expansion and perhaps need a much better theory of particle physics and gravity than what we have now. Physics is still an exciting area of research and there is an awful lot that is not known.
 
J

jeffinchiangmai

Guest
I suppose this must be one of the most frequently asked questions since 1905 but I am still trying to get my head around space-time. I think I understand the analogy of the ball of current dough which started expanding 13.7 billion years ago until now. I'm trying to see how any point in that ball of dough can look in any direction for 13.7 BY and see the same thing. Suppose our galaxy is a current right near (or on) the surface of the ball of dough, if we look inward, we look back 13.7 BY but if we look outward we can see nothing (i.e no other galaxy - nothingness). I can understand, if I am right that in looking out, that small distance (if any) is still 13.7 BY where time has gone very slowly (in that distance), (or even stopped if we are right on the surface of the ball of dough).

If we are right on the surface of the expanding ball of dough and look inwardly in all directions so that we can see the inner shell of the ball of dough (or maybe balloon in this case), I can see how that inner surface, at distances from zero to maximum would represent the CMBR and that these distances would still represent 13.7 BY due to those distances materializing in the same time span.

If our galaxy was right on the surface of the balloon and that surface represents the CMBR, would we also be the same age as the CMBR, i.e. zero years old? How could that be when all galaxies are the same age?

Another analogy could be a great circle map (used in ham radio) where the circumference of the great circle map represents a single point on the opposite side of the earth. May be I'm being too complex here.

I just want the penny to finally drop. So glad I found this sight.
 
D

DrRocket

Guest
jeffinchiangmai":3otzy6in said:
I suppose this must be one of the most frequently asked questions since 1905 but I am still trying to get my head around space-time. I think I understand the analogy of the ball of current dough which started expanding 13.7 billion years ago until now. I'm trying to see how any point in that ball of dough can look in any direction for 13.7 BY and see the same thing. Suppose our galaxy is a current right near (or on) the surface of the ball of dough, if we look inward, we look back 13.7 BY but if we look outward we can see nothing (i.e no other galaxy - nothingness). I can understand, if I am right that in looking out, that small distance (if any) is still 13.7 BY where time has gone very slowly (in that distance), (or even stopped if we are right on the surface of the ball of dough).

If we are right on the surface of the expanding ball of dough and look inwardly in all directions so that we can see the inner shell of the ball of dough (or maybe balloon in this case), I can see how that inner surface, at distances from zero to maximum would represent the CMBR and that these distances would still represent 13.7 BY due to those distances materializing in the same time span.

If our galaxy was right on the surface of the balloon and that surface represents the CMBR, which occurred 13.7 BY ago, would we would also be the same age as the CMBR, zero years old?

Another analogy could be a great circle map (used in ham radio) where the circumference of the great circle map represents a single point on the opposite side of the earth. May be I'm being too complex here.

I just want the penny to finally drop. So glad I found this sight.
The ball of dough or the balloon analogy are intended to help you think about space-time as a manifold without using the word "manifold" or invoking the associated mathematics. It can be a bit confusing.

A manifold is mathematical construct, a topological space, that "locally looks like" ordinary Euclidean space of the appropriate dimension. Space-time is a 4-dimensional Lorentzian manifold. The term "Lorentzian" tells you something about the geometry of the manifold and what is called the "differentiable structure", but we won't worry about that here.

The surface of a balloon, or the surface of a ball of dough, is a 2-dimensional manifold. Locally it looks like a plane, just as the surface of the earth looks like a plane at small scales, but at larger scales you see the effect of curvature.

While the examples that you are being given are of manifolds that are contained, or embedded in some higher-dimensional space (the surface of the ball of dough for instance is a 2-manifold that is embedded in the 3-dinmensinal space of the kitchen) is it not at all necessary for a manifold to embedded in anything at all. Such manifolds are called "intrinsic manifolds". Space-time is an intrinsic manifold. It is not necessarily embedded in anything else. That point is critical -- an intrinsic manifold is complete unto itself and there need not be any larger space anywhere.

So, now think of the surface of the balloon or the surface of the ball of dough as intrinsic manifolds -- just forget about the larger space in which they are realized. The surface is all that there is. If you not imagine yourself as an ant on that surface, then things look the same in all directions -- remembering that by a "direction" we mean along any line that lies totally on the surface. Further, by a line we mean a geodesic on the surface -- a curve that is locally the smallest distance between points. On a sphere the geodesics are great circles. (This gets a little more complicated with Lorentzian manifolds but that complication is not necessary to point here).

So the reason that things look the same in all directions on your ball of dough is because you are only allowed to look along curges that lie on the surface. You are not alllowed to look "inward" or "outward" because those directions lie in dimensions that do not exist with respect to the intrinsic manifold.
 
C

CommonMan

Guest
DrRocket":27c95h3i said:
jeffinchiangmai":27c95h3i said:
I suppose this must be one of the most frequently asked questions since 1905 but I am still trying to get my head around space-time. I think I understand the analogy of the ball of current dough which started expanding 13.7 billion years ago until now. I'm trying to see how any point in that ball of dough can look in any direction for 13.7 BY and see the same thing. Suppose our galaxy is a current right near (or on) the surface of the ball of dough, if we look inward, we look back 13.7 BY but if we look outward we can see nothing (i.e no other galaxy - nothingness). I can understand, if I am right that in looking out, that small distance (if any) is still 13.7 BY where time has gone very slowly (in that distance), (or even stopped if we are right on the surface of the ball of dough).

If we are right on the surface of the expanding ball of dough and look inwardly in all directions so that we can see the inner shell of the ball of dough (or maybe balloon in this case), I can see how that inner surface, at distances from zero to maximum would represent the CMBR and that these distances would still represent 13.7 BY due to those distances materializing in the same time span.

If our galaxy was right on the surface of the balloon and that surface represents the CMBR, which occurred 13.7 BY ago, would we would also be the same age as the CMBR, zero years old?

Another analogy could be a great circle map (used in ham radio) where the circumference of the great circle map represents a single point on the opposite side of the earth. May be I'm being too complex here.

I just want the penny to finally drop. So glad I found this sight.
The ball of dough or the balloon analogy are intended to help you think about space-time as a manifold without using the word "manifold" or invoking the associated mathematics. It can be a bit confusing.

A manifold is mathematical construct, a topological space, that "locally looks like" ordinary Euclidean space of the appropriate dimension. Space-time is a 4-dimensional Lorentzian manifold. The term "Lorentzian" tells you something about the geometry of the manifold and what is called the "differentiable structure", but we won't worry about that here.

The surface of a balloon, or the surface of a ball of dough, is a 2-dimensional manifold. Locally it looks like a plane, just as the surface of the earth looks like a plane at small scales, but at larger scales you see the effect of curvature.

While the examples that you are being given are of manifolds that are contained, or embedded in some higher-dimensional space (the surface of the ball of dough for instance is a 2-manifold that is embedded in the 3-dinmensinal space of the kitchen) is it not at all necessary for a manifold to embedded in anything at all. Such manifolds are called "intrinsic manifolds". Space-time is an intrinsic manifold. It is not necessarily embedded in anything else. That point is critical -- an intrinsic manifold is complete unto itself and there need not be any larger space anywhere.

So, now think of the surface of the balloon or the surface of the ball of dough as intrinsic manifolds -- just forget about the larger space in which they are realized. The surface is all that there is. If you not imagine yourself as an ant on that surface, then things look the same in all directions -- remembering that by a "direction" we mean along any line that lies totally on the surface. Further, by a line we mean a geodesic on the surface -- a curve that is locally the smallest distance between points. On a sphere the geodesics are great circles. (This gets a little more complicated with Lorentzian manifolds but that complication is not necessary to point here).

So the reason that things look the same in all directions on your ball of dough is because you are only allowed to look along curges that lie on the surface. You are not alllowed to look "inward" or "outward" because those directions lie in dimensions that do not exist with respect to the intrinsic manifold.
I have a personal question for you, if it’s allowed, I don’t want to ask anything I’m not supposed to, but I was wordending if you are a real bonafide scientist. Not like jim48 claims to be. I have been reading your replies to some of these threads and wonder why you spin your time replying to some of the questions like the ones I write and waste your time on them. Are you retired? Or have the extra time for this? It seemed to me that one with your education could find something more profitable to do. Don’t get me wrong I like to see someone who really knows what they are talking about and spins the time trying to make some of us dummies understand.
 
S

Saiph

Guest
Well, I'm not sure about DrRocket's reasons for posting here, but I'll provide my own, which are many, for why I post here and use the knowledge I gained in achieving my B.S. in astronomy to answer seemingly trivial questions:

1) To exercise my mind and knowledge of the subject. I find the advice about learning often touted to be accurate "You learn best, by teaching". After all the help I've provided on SDC, I find that I never understand a subject well until I've tried to explain it to someone else. AND that even after the tenth explaination of the same subject, I still seem to get a little bit of insight. Part of this is because I have to break it down in a way that others can understand, laying out each piece of information to form the entire picture. The other part is the other posters on the board often ask questions I'd never have contemplated, or ask familiar questions in unfamiliar ways that still lead to an interesting perspective.

2) To encourage the hobby and interest in the field. Science is sadly a waning interest in the US (the predominate audience of SDC) despite the technological boom we've helped spearhead. At least, that's what I see when I talk to people. And it isn't really because people aren't interested in the material, but because it isn't presented in an approachable fashion. To often do the public see science as a field best left to the ivory tower intellectuals, and don't think they can even begin to understand any of it.

I like to make the experience of learning about astronomy, and physics and the world around us enjoyable, and understandable. If people can't find a ready source of information on a subject, they just get frustrated, and give up trying. I like to think that I help provide that information, and encourage people's efforts to learn about the universe.

3) Sadly, an often to frequent a reason, to counteract the psuedo-science whacko's, or the misguided (but very enthusiastic) amateurs from leading people astray. Another phrase you're probably familiar with fits here "Evil triumphs when good men stand aside". Not quite so dramatic here, but still apt: "Ignorance triumphs when wise men stay silent".

If myself and others who do know how to address the questions asked here say nothing, but ufo conspiracy theorist speaks up and spews their jibberish...the poster and those that lurk around here have no real choice but to believe them, as they aren't provided an alternative. I rarely have any aspirations to converting the mistaken soul that insists martians made a face on mars, or that the sun is a solid sphere of iron, or the galaxy is just a giant battery..or....etc, etc. But I can keep them from convincing others who are just asking a simple question, and I'll often debate such people for pages to make sure they don't win through sheer volume and endurance.
 
J

jeffinchiangmai

Guest
Saiph":26zmevim said:
Well, I'm not sure about DrRocket's reasons for posting here, but I'll provide my own, which are many, for why I post here and use the knowledge I gained in achieving my B.S. in astronomy to answer seemingly trivial questions:

1) To exercise my mind and knowledge of the subject. I find the advice about learning often touted to be accurate "You learn best, by teaching". After all the help I've provided on SDC, I find that I never understand a subject well until I've tried to explain it to someone else. AND that even after the tenth explaination of the same subject, I still seem to get a little bit of insight. Part of this is because I have to break it down in a way that others can understand, laying out each piece of information to form the entire picture. The other part is the other posters on the board often ask questions I'd never have contemplated, or ask familiar questions in unfamiliar ways that still lead to an interesting perspective.

2) To encourage the hobby and interest in the field. Science is sadly a waning interest in the US (the predominate audience of SDC) despite the technological boom we've helped spearhead. At least, that's what I see when I talk to people. And it isn't really because people aren't interested in the material, but because it isn't presented in an approachable fashion. To often do the public see science as a field best left to the ivory tower intellectuals, and don't think they can even begin to understand any of it.

I like to make the experience of learning about astronomy, and physics and the world around us enjoyable, and understandable. If people can't find a ready source of information on a subject, they just get frustrated, and give up trying. I like to think that I help provide that information, and encourage people's efforts to learn about the universe.

3) Sadly, an often to frequent a reason, to counteract the psuedo-science whacko's, or the misguided (but very enthusiastic) amateurs from leading people astray. Another phrase you're probably familiar with fits here "Evil triumphs when good men stand aside". Not quite so dramatic here, but still apt: "Ignorance triumphs when wise men stay silent".

If myself and others who do know how to address the questions asked here say nothing, but ufo conspiracy theorist speaks up and spews their jibberish...the poster and those that lurk around here have no real choice but to believe them, as they aren't provided an alternative. I rarely have any aspirations to converting the mistaken soul that insists martians made a face on mars, or that the sun is a solid sphere of iron, or the galaxy is just a giant battery..or....etc, etc. But I can keep them from convincing others who are just asking a simple question, and I'll often debate such people for pages to make sure they don't win through sheer volume and endurance.
I agree with everything you have said here. I'm not a scientist although I have friends who are. Having watched a UK quiz show for the general public I can usually guarantee that every science question will be answered incorrectly. e.g. "what is the measurement of electrical frequency", the answer given was "volts".

Like Hawking said, the fact that mankind can sit on this little planet and understand the beginning of the universe is our greatest ever achievement.

I, as the general public (with only engineering background) became interested in cosmology after reading Hawking's first book. Cosmology and similar sciences just puts everything else into perspective. I tried to read as much other material as I could but often get stuck when things become too difficult.

Yesterday I found this site and was delighted. What this is, is a kind of club for enthusiasts but in every club you get a mixture of people like me and people like you who want to act as mentors to people like me. However, without people like you, there would be no club. Hope this explains the point of view from the receiver side.
 
J

jeffinchiangmai

Guest
CommonMan":1hbzu6jt said:
DrRocket":1hbzu6jt said:
The ball of dough or the balloon analogy are intended to help you think about space-time as a manifold without using the word "manifold" or invoking the associated mathematics. It can be a bit confusing.

A manifold is mathematical construct, a topological space, that "locally looks like" ordinary Euclidean space of the appropriate dimension. Space-time is a 4-dimensional Lorentzian manifold. The term "Lorentzian" tells you something about the geometry of the manifold and what is called the "differentiable structure", but we won't worry about that here.

The surface of a balloon, or the surface of a ball of dough, is a 2-dimensional manifold. Locally it looks like a plane, just as the surface of the earth looks like a plane at small scales, but at larger scales you see the effect of curvature.

While the examples that you are being given are of manifolds that are contained, or embedded in some higher-dimensional space (the surface of the ball of dough for instance is a 2-manifold that is embedded in the 3-dinmensinal space of the kitchen) is it not at all necessary for a manifold to embedded in anything at all. Such manifolds are called "intrinsic manifolds". Space-time is an intrinsic manifold. It is not necessarily embedded in anything else. That point is critical -- an intrinsic manifold is complete unto itself and there need not be any larger space anywhere.

So, now think of the surface of the balloon or the surface of the ball of dough as intrinsic manifolds -- just forget about the larger space in which they are realized. The surface is all that there is. If you not imagine yourself as an ant on that surface, then things look the same in all directions -- remembering that by a "direction" we mean along any line that lies totally on the surface. Further, by a line we mean a geodesic on the surface -- a curve that is locally the smallest distance between points. On a sphere the geodesics are great circles. (This gets a little more complicated with Lorentzian manifolds but that complication is not necessary to point here).

So the reason that things look the same in all directions on your ball of dough is because you are only allowed to look along curges that lie on the surface. You are not alllowed to look "inward" or "outward" because those directions lie in dimensions that do not exist with respect to the intrinsic manifold.
Thanks for the very clear explanation and for pointing me in th right direction. With this guidance, I can now go and do a bit of in depth reading. At this stage I won't bother you with silly questions. Let me understand more and I will get back.
 
D

DrRocket

Guest
CommonMan":1r8n4zup said:
I have a personal question for you, if it’s allowed, I don’t want to ask anything I’m not supposed to, but I was wordending if you are a real bonafide scientist. Not like jim48 claims to be. I have been reading your replies to some of these threads and wonder why you spin your time replying to some of the questions like the ones I write and waste your time on them. Are you retired? Or have the extra time for this? It seemed to me that one with your education could find something more profitable to do. Don’t get me wrong I like to see someone who really knows what they are talking about and spins the time trying to make some of us dummies understand.
I am retired. I do a little consulting from time to time.

Posting here keeps me thinking and I hope provides a little help for people who are geneuinely trying to learn science. My objective to to help such people to learn and to point out the pitfalls in the incorrect things that are posted so that they don't get derailed.
 
D

DrRocket

Guest
jeffinchiangmai":f91kr5df said:
Saiph":f91kr5df said:
I agree with everything you have said here. I'm not a scientist although I have friends who are. Having watched a UK quiz show for the general public I can usually guarantee that every science question will be answered incorrectly. e.g. "what is the measurement of electrical frequency", the answer given was "volts".
It is worse than you think. The question demonstrates some ignorance as well.

It is clear that the answer for which they were fishing is "Hertz" which used to be called "cycles per second". That is NOT an electrical term. It applies to all periodic phenomenon. It applies just as well in acoustics and theory of mechanical vibrations as it does to the electromagnetic spectrum or simple AC power generation.

The question was not only misleading, it also demonstrates a problem with the general way in which "science" is presented -- with emphasis on terminology and not on understanding. Feynman was fond of pointing out that knowing the name of something has little to do with understanding that thing. Knowing the term "Hertz" demonstrates no understanding whatever of the science of periodic phenomena. I'll bet the person who posed the question knows that the answer was "Hertz", but knows nothing about Fourier series and how periodic functions can be used to understand complex physical phenomena.
 
M

MeteorWayne

Guest
A very good point Dr Rocket. I often get frustrated with quiz shows with poorly worded or misunderstood questions (or in the case of Jeopardy, answers :) ) How do you answer an incorrect question?

As for why I post, it is for all the reasons that Saiph and Dr Rocket mentioned, but it's also to share. I am a reading addict; I have been that way since I got my first "Weekly Reader" subscription at age 5. I am a voracious reader, and have therefore piled up boatloads of knowledge. Sharing what I have learned is a great pleasure. Reading SDC is an even greater pleasure since there are those that know more about subjects than I do, or can explain them in better ways than I can, which help me understand it better. This allows me to share that knowledge in the future, which makes me happy as well. I love public nights at the NJAA when the man, woman, and kid off the street get to ponder the sky, ask questions, and get answers, many for the first time. I love getting to teach an Adult Education class on my passion, Meteors (Next Thursday :) ) again, to share what I have learned. It's one of the better aspects of my life.

MW
 
S

SpeedFreek

Guest
DrRocket":1nloho67 said:
I am retired. I do a little consulting from time to time.

Posting here keeps me thinking and I hope provides a little help for people who are genuinely trying to learn science. My objective to to help such people to learn and to point out the pitfalls in the incorrect things that are posted so that they don't get derailed.
DrRocket is being modest - as I remember (and I hope he doesn't mind me saying this..), he is actually a retired rocket scientist, with various qualifications including a PhD in Mathematics, a subject he used to teach.

:)

Whereas I am simply an enthusiastic amateur - and I just hope I don't spread too many misconceptions!
 
J

jeffinchiangmai

Guest
MeteorWayne":98ua7emk said:
A very good point Dr Rocket. I often get frustrated with quiz shows with poorly worded or misunderstood questions (or in the case of Jeopardy, answers :) ) How do you answer an incorrect question?

As for why I post, it is for all the reasons that Saiph and Dr Rocket mentioned, but it's also to share. I am a reading addict; I have been that way since I got my first "Weekly Reader" subscription at age 5. I am a voracious reader, and have therefore piled up boatloads of knowledge. Sharing what I have learned is a great pleasure. Reading SDC is an even greater pleasure since there are those that know more about subjects than I do, or can explain them in better ways than I can, which help me understand it better. This allows me to share that knowledge in the future, which makes me happy as well. I love public nights at the NJAA when the man, woman, and kid off the street get to ponder the sky, ask questions, and get answers, many for the first time. I love getting to teach an Adult Education class on my passion, Meteors (Next Thursday :) ) again, to share what I have learned. It's one of the better aspects of my life.

MW
Good points. I'm 61 and have picked up a few things over the years. (Nothing worth mentioning at you level of course). I read somewhere that old age is when you know all the answers but no body asks the questions. It great that you can teach and pass on some of your knowledge and experience and commendable that you can spend your time on this site.

A few years ago when the media was full of the encroaching Leonids shower, I found myself in the back of a pickup in Thailand heading up a mountain road to the highest point which was the Thai/ Burmese border armed with binoculars, cameras and lenses. Many other people had the same idea. The sky was clear but it was so cold that many people build fires by the side of the road so the air became so thick with smoke that we decided to head back home.
 
J

jeffinchiangmai

Guest
DrRocket":3gqs4t1j said:
jeffinchiangmai":3gqs4t1j said:
Saiph":3gqs4t1j said:
I agree with everything you have said here. I'm not a scientist although I have friends who are. Having watched a UK quiz show for the general public I can usually guarantee that every science question will be answered incorrectly. e.g. "what is the measurement of electrical frequency", the answer given was "volts".
It is worse than you think. The question demonstrates some ignorance as well.

It is clear that the answer for which they were fishing is "Hertz" which used to be called "cycles per second". That is NOT an electrical term. It applies to all periodic phenomenon. It applies just as well in acoustics and theory of mechanical vibrations as it does to the electromagnetic spectrum or simple AC power generation.

The question was not only misleading, it also demonstrates a problem with the general way in which "science" is presented -- with emphasis on terminology and not on understanding. Feynman was fond of pointing out that knowing the name of something has little to do with understanding that thing. Knowing the term "Hertz" demonstrates no understanding whatever of the science of periodic phenomena. I'll bet the person who posed the question knows that the answer was "Hertz", but knows nothing about Fourier series and how periodic functions can be used to understand complex physical phenomena.
Many yeas ago, the head engineer of a steel company in a certain country that must remain nameless, came and asked me a private question. "Why do we have to have such big transformers outside when we could have small ones - (after all), they have the same voltages. He obviously had never understood anything that he had been taught. He did have a very good memory though. I agree with you about science being about understanding. I think in engineering you also develop a "sense" when something is right or wrong.
 
D

DrRocket

Guest
jeffinchiangmai":fk6qus9d said:
Many yeas ago, the head engineer of a steel company in a certain country that must remain nameless, came and asked me a private question. "Why do we have to have such big transformers outside when we could have small ones - (after all), they have the same voltages. He obviously had never understood anything that he had been taught. He did have a very good memory though. I agree with you about science being about understanding. I think in engineering you also develop a "sense" when something is right or wrong.
That "sense of when something is right or wrong" is a two-edged sword. Good engineers do develop that sense, but they do no rely on it. When you have a "sense" you need to back it up with real data and valid calculations. I cannot begin to count the number of times I have seen engineers with a "sense" that was completely wrong. And the results of those incorrect "senses" have often been major failures, sometimes with fatalitiess.

In God we trust -- all others bring data.
 
J

jeffinchiangmai

Guest
DrRocket":87g3efq5 said:
jeffinchiangmai":87g3efq5 said:
Many yeas ago, the head engineer of a steel company in a certain country that must remain nameless, came and asked me a private question. "Why do we have to have such big transformers outside when we could have small ones - (after all), they have the same voltages. He obviously had never understood anything that he had been taught. He did have a very good memory though. I agree with you about science being about understanding. I think in engineering you also develop a "sense" when something is right or wrong.
That "sense of when something is right or wrong" is a two-edged sword. Good engineers do develop that sense, but they do no rely on it. When you have a "sense" you need to back it up with real data and valid calculations. I cannot begin to count the number of times I have seen engineers with a "sense" that was completely wrong. And the results of those incorrect "senses" have often been major failures, sometimes with fatalitiess.

In God we trust -- all others bring data.
Yes, you are absolutely right and I can understand your contempt for people who "think" they are right without doing sufficient and thorough investigation, especially where the consequences can be significant.
I used to be quite good at finding faults on complex equipment which I wasn't always particularly familiar with.
I felt that I has a "nose" for it.
Once I drove a long way to an old steel rolling mill which I had never been to before. At 2 in the morning I was taken to a huge cellar underneath the mill. The cellar contained rows and rows of cabinets and racks and racks of what turned out to be selenium diodes contained in little valve bases. (maybe there had been a revamp at some stage where diode valves (tubes)) had been replace by solid state devices.
After 5 minutes mulling over schematics trying to isolate the location of the problem, I found what I thought to be the problem area containing a faulty selenium diode that I had identified on one of the schematics. Knowing that selenium diodes give of a characteristic pungent smell when they burn out, I sniffed out the offending article within seconds without reference to the schematic. Within minutes, the mill was back on line again.
Of course this problem didn't require any further investigation as the cause was straight forward but I never left a problem until I fully understood the real cause behind it and to make sure that it would not reoccur (well only once but I learned my lesson). Unfortunately, the trend today is to replace the damaged component without analyzing the real cause.
Again, this come back to an understanding of the big picture rather than just the individual part.
 
D

DrRocket

Guest
jeffinchiangmai":1djmr9gn said:
Yes, you are absolutely right and I can understand your contempt for people who "think" they are right without doing sufficient and thorough investigation, especially where the consequences can be significant.
I used to be quite good at finding faults on complex equipment which I wasn't always particularly familiar with.
I felt that I has a "nose" for it.
Once I drove a long way to an old steel rolling mill which I had never been to before. At 2 in the morning I was taken to a huge cellar underneath the mill. The cellar contained rows and rows of cabinets and racks and racks of what turned out to be selenium diodes contained in little valve bases. (maybe there had been a revamp at some stage where diode valves (tubes)) had been replace by solid state devices.
After 5 minutes mulling over schematics trying to isolate the location of the problem, I found what I thought to be the problem area containing a faulty selenium diode that I had identified on one of the schematics. Knowing that selenium diodes give of a characteristic pungent smell when they burn out, I sniffed out the offending article within seconds without reference to the schematic. Within minutes, the mill was back on line again.
Of course this problem didn't require any further investigation as the cause was straight forward but I never left a problem until I fully understood the real cause behind it and to make sure that it would not reoccur (well only once but I learned my lesson). Unfortunately, the trend today is to replace the damaged component without analyzing the real cause.
Again, this come back to an understanding of the big picture rather than just the individual part.
Precisely. You use your intuition to identify the likely problem and then use rigorous science and engineering to show that your intuition was correct. It is when people take their intuition as the last word that thing go bad.

That is, to some people surprisingly, the way that research mathematicians work. First you "guess" the answer or theorem. Then you go back and rigorously show that your intuition was correct. But what winds up being published is the rigorous proofs and the discovery process often remains a bit mysterious.

Engineers and scientists (the good ones) work in similar ways. But unfortunately there are some not-so-good ones who don't realize when their intuition is faulty and they are the cause of a lot wasted money, a lot of wasted effort, and, unfortuately, on occasion lives. I have seen that happen, and have prevented it from happening in a few instances.

Intuition is important, even vital. But it is not enough.
 
D

drwayne

Guest
I remember several years ago having a discussion with someone who was using a term
incorrectly. Upon having this pointed out to him - he said something along the lines of
"why can't words mean what I want them to mean"

:roll: :roll: :roll:

Wayne
 
D

derekmcd

Guest
drwayne":1l9kxv5d said:
I remember several years ago having a discussion with someone who was using a term
incorrectly. Upon having this pointed out to him - he said something along the lines of
"why can't words mean what I want them to mean"

:roll: :roll: :roll:

Wayne
Must have been an electric universe proponent... :p
 
Q

QuantumLeap_26

Guest
DrRocket":3gxf7e3i said:
jeffinchiangmai":3gxf7e3i said:
Yes, you are absolutely right and I can understand your contempt for people who "think" they are right without doing sufficient and thorough investigation, especially where the consequences can be significant.
I used to be quite good at finding faults on complex equipment which I wasn't always particularly familiar with.
I felt that I has a "nose" for it.
Once I drove a long way to an old steel rolling mill which I had never been to before. At 2 in the morning I was taken to a huge cellar underneath the mill. The cellar contained rows and rows of cabinets and racks and racks of what turned out to be selenium diodes contained in little valve bases. (maybe there had been a revamp at some stage where diode valves (tubes)) had been replace by solid state devices.
After 5 minutes mulling over schematics trying to isolate the location of the problem, I found what I thought to be the problem area containing a faulty selenium diode that I had identified on one of the schematics. Knowing that selenium diodes give of a characteristic pungent smell when they burn out, I sniffed out the offending article within seconds without reference to the schematic. Within minutes, the mill was back on line again.
Of course this problem didn't require any further investigation as the cause was straight forward but I never left a problem until I fully understood the real cause behind it and to make sure that it would not reoccur (well only once but I learned my lesson). Unfortunately, the trend today is to replace the damaged component without analyzing the real cause.
Again, this come back to an understanding of the big picture rather than just the individual part.
Precisely. You use your intuition to identify the likely problem and then use rigorous science and engineering to show that your intuition was correct. It is when people take their intuition as the last word that thing go bad.

That is, to some people surprisingly, the way that research mathematicians work. First you "guess" the answer or theorem. Then you go back and rigorously show that your intuition was correct. But what winds up being published is the rigorous proofs and the discovery process often remains a bit mysterious.

Engineers and scientists (the good ones) work in similar ways. But unfortunately there are some not-so-good ones who don't realize when their intuition is faulty and they are the cause of a lot wasted money, a lot of wasted effort, and, unfortuately, on occasion lives. I have seen that happen, and have prevented it from happening in a few instances.

Intuition is important, even vital. But it is not enough.

I am admittedly a bit of a newcomer to this forum, but I found this post as well as the posts of many others involved as resonating with my own convictions. I've long dismissed the distinctly faulty premise of human infallibility as merely that, distinctly faulty, if not downright erroneous. The human ego is by far the most impressive thing mankind's got going for it. Don't get me wrong. I'm merely an adolescent, and so my vast stores of idealism have yet to wane. I do not for one second doubt the capacity of man to perceive more than what is readily revealed to him. After all, this is the entire basis of the vision underlying our species. I just agree with the comments voiced in the preceding posts: that science is the objective acquisition of knowledge, not the mere predisposition to it. And despite our acute discomfort with such prospects, we're not all that "predisposed" in the first place. We are forced to go out of our way in order to construct instruments that compensate for our gross biological and intellectual shortcomings. We apply rigor to our theories because they are the product of human minds, and are therefore subject to error, in need of a firm experimental basis with which to support their claims. It is a requisite of science that we acknowledge our faculties as being formidable yet fallible.
 
A

aphh

Guest
Heureka! I think I have an explanation for the ever expanding universe!

The universe is simply spinning around an axis. Even if it was spinning at constant rate, the huge masses involved would mean that due to inertia they are only accelerating outwards. Because there is no reference frame, we can't see or feel our universe spinning, but only the effects of the spinning!

Problem with this theory is if the universe is expanding to all directions. But if the space can be bent, how do we know that the direction isn't still the same direction, just visually bent because of curved space?
 
D

DrRocket

Guest
aphh":17a8yp19 said:
Heureka! I think I have an explanation for the ever expanding universe!

The universe is simply spinning around an axis. Even if it was spinning at constant rate, the huge masses involved would mean that due to inertia they are only accelerating outwards. Because there is no reference frame, we can't see or feel our universe spinning, but only the effects of the spinning!

Problem with this theory is if the universe is expanding to all directions. But if the space can be bent, how do we know that the direction isn't still the same direction, just visually bent because of curved space?
`
There are a few problems:

1. The universe IS expanding in all directions. The universe appears to be quite isotropic.

2. Spinning with respect to what ? That is not a trivial question. You can only provide a sensible answer if the universe is embedded in some larger space, but there is no evidence of that. Even if there were something with respect to which the universe is spinning, all of our physics is based on descriptions that rely solely on the universe itself. Hence all of the issues below remain valid. Our physical laws are not formulated in any manner in which some higher-dimensional space would change them..

3. IF the universe were spinning in any reasosnable sense, then there ought to be some pretty noticeable deviations from Newtonian mechanics (e.g. coriolis forces would be noticeable) that are not seen. There would need to be an axis of rotation (you can prove that mathematically for a 3-dimensional space simply because there needs to be a real eigenvalue for the isometric transformation of rotation). And if there were an axis of rotatin everything would be moving outward from that axis creating a noticeable hole somewhere that is not seen.

4. Space appears to be pretty flat on the largest scales. So any explanations that rely on a strongly curved spatial model are in trouble.
 
Status
Not open for further replies.

ASK THE COMMUNITY

Latest posts