Astronomy / Space Is the universe expanding faster than the speed of light?

[DigitalDuck]

Lightspeed isn't constant.. Gravity can change/warp/bend and indeed in the case of a black hole have such a force that light isn't fast enough to escape the field. At least that's what was described to me when I was at stargazing live in January.

The speed of light is constant. Bending space doesn't change the speed of light, it just changes the path it travels (in the case of a black hole, changes it so much that it's pretty much impossible to comprehend what actually happens to it). As a massless particle it can't physically travel at any speed other than the universal constant.

That doesn't mean it's necessarily the fastest thing around, though...

 

[Sir.Tj]

The speed of light is constant. Bending space doesn't change the speed of light, it just changes the path it travels (in the case of a black hole, changes it so much that it's pretty much impossible to comprehend what actually happens to it). As a massless particle it can't physically travel at any speed other than the universal constant.

That doesn't mean it's necessarily the fastest thing around, though...

That's pretty much how I've always seen it.

However, I don't believe that light is the fastest thing in the universe, the speed my kids disappear when the washing-up needs doing beggars belief

In fact I propose E=mk+d2

E=mass(kid+dishes)2

 

[Aewarin Jameson]

The speed of light is constant

Didn't sound right to me this statement ... I know the speed of light is denoted 'c' and that value doesn't change, and AFAIK gravity doesn't slow light but bends it (so a black hole basically bends light into itself if the beam gets too close) but the speed of light isn't constant or am I misunderstanding that news letter ? In other words the speed of photons (light) move at some speed up to 'c' ?

 

[Cody]

The speed of light in a vacuum is the constant (denoted as 'c').

 

[Orbitalai]

The expansion of the universe has always puzzled me: gravity is an attractive force, Brownian motion doesn't seem to be sufficient to push things apart, and the expansion is apparently speeding up, so it's not just a leftover "explosion". There must be some really big forces we have no idea about?

Brownian motion is also not responsible for the expansion. Stretching of the space itself is.

You are right about that, there never was any explosion. An explosion is an expansion from a centre pushing things apart, the universe is expanding at same rate everywhere, there is no centre. But there was however most likely in the beginning a rapid expansion, astronomers tend to think it was caused by a field called the inflaton. It stopped however.

Space itself does also seem to cause an expansion of itself. The more space there is, the faster it will expand. This effect was very small at beginning, as the space was not so big. But slowly that effect has become so big that it overcomes the collective gravity attraction of the entire universe, so that the universe is now even accelerating the expansion. If it continues with this rate you will later never see any light at all, since the separation of even close objects will be faster than speed of light. This effect they call dark energy btw., its cause is not known yet.

I'm just an amateur who has read lots of books, but it feels like we know lots about the minutiae, and can do the maths very well, but have no clue about what is all really means (cf Copenhagen interpretation).

String theory and supersymmetry are good, but we are still missing something *huge* in our understanding of the universe. Maybe we can never "understand" it in any meaningful way.

I am also just an amateur, and have spent countless hours looking into this stuff. Its just too fascinating.

Indeed. Particle physics is much much better understood than large scale things. That is also why lately alot of hints of new particle physics have not come from particles, but from astronomical observations. As they say themselves astronomical studies is racing ahead, while particle physics in many aspects has been stale for 30 years, only confirming the known stuff and coming up with ideas they cannot falsify.

I feel however that judging from humans past ability to discover secrets about the universe I am fairly optimistic about our ability to get good post big bang understanding in a couple of hundreds years.

 

[DigitalDuck]

Didn't sound right to me this statement ... I know the speed of light is denoted 'c' and that value doesn't change, and AFAIK gravity doesn't slow light but bends it (so a black hole basically bends light into itself if the beam gets too close) but the speed of light isn't constant or am I misunderstanding that news letter ? In other words the speed of photons (light) move at some speed up to 'c' ?

The speed of light in a vacuum is the constant (denoted as 'c').

This is something that's often confused.

The speed of light (the photons themselves, or at least when you're representing light as photons) is constant. Photons cannot travel at a speed that is not 'c'. They can't even travel at 0.999999999999c. They have no mass, and therefore do not exist at speeds less than, or greater than, c.

What's happening in the experiment, or indeed when light travels through any medium, is that the apparent speed of light is reduced. Light doesn't travel in a straight line, it travels the path of least energy. When other particles are in the way, some of the light scatters around it (taking a longer path, and therefore appearing slower), and some of the light is absorbed by the particle, and then re-emitted at a later time (basically "taking a break" in the middle, and therefore appearing slower).

At no point do any individual particles travel at less than c.

 

[Darren Grey]

There's an interesting effect when electrons travel faster than the apparent speed of light in a medium

 

[DrBaggy]

Brownian motion is also not responsible for the expansion. Stretching of the space itself is.

You are right about that, there never was any explosion. An explosion is an expansion from a centre pushing things apart, the universe is expanding at same rate everywhere, there is no centre. But there was however most likely in the beginning a rapid expansion, astronomers tend to think it was caused by a field called the inflaton. It stopped however.

Space itself does also seem to cause an expansion of itself. The more space there is, the faster it will expand. This effect was very small at beginning, as the space was not so big. But slowly that effect has become so big that it overcomes the collective gravity attraction of the entire universe, so that the universe is now even accelerating the expansion. If it continues with this rate you will later never see any light at all, since the separation of even close objects will be faster than speed of light. This effect they call dark energy btw., its cause is not known yet.



I am also just an amateur, and have spent countless hours looking into this stuff. Its just too fascinating.

Indeed. Particle physics is much much better understood than large scale things. That is also why lately alot of hints of new particle physics have not come from particles, but from astronomical observations. As they say themselves astronomical studies is racing ahead, while particle physics in many aspects has been stale for 30 years, only confirming the known stuff and coming up with ideas they cannot falsify.

I feel however that judging from humans past ability to discover secrets about the universe I am fairly optimistic about our ability to get good post big bang understanding in a couple of hundreds years.

Thanks for that thoughtful post. Of course every answer raises more questions: why (or perhaps more properly, how) does space expand? I have never quite got my head round "finite but unbounded". And Richard Feynmann was spot on when he described forces as "spooky action at a distance". The implications of the two slit experiment are mind-blowing. I agree it's fascinating: it feels as though there is something overarching and probably simple out there, but we just can't get to it. Probably our ideas of quarks, gravity, Higgs bosons etc will turn out to be something very different from what we think. Maybe, like phlogiston and the aether, they are ideas to hang things on while we grope to understand the very big, very small and very fast with our middle-sized imaginations.

Fascinating stuff!

In my own area, we know lots about the brain, but practically nothing about consciousness. We are flatworlders in a 16 dimensional universe!

 

[Orbitalai]

why (or perhaps more properly, how) does space expand? I have never quite got my head round "finite but unbounded". And Richard Feynmann was spot on when he described forces as "spooky action at a distance". The implications of the two slit experiment are mind-blowing.

Well space expansion mechanics is also way over my head. Something to do with vacuum decay, no clue really.

I was not aware that Feynman used that phrase also. Einstein used it also to describe quantum entanglement, which he did not believe in. But when thinking about the force fields extending all over space, and the Higgs field even being turned on everywhere, I do not see it as so spooky, I sorta view the forces as just extending everywhere, gravitation from objects billions of LY away make more meaning to me in that view. An yeah, two slit experiments sure can result in mind-blowing stuff, like ultra mind-blowing. Also quantum entanglement and tunnelling is more freaky that I ever could imagine nature to act. I sometimes wish I had become a particle physicist instead of engineer, just to understand that stuff.

 

[DigitalDuck]

I sometimes wish I had become a particle physicist instead of engineer, just to understand that stuff.

Anybody who claims to understand quantum mechanics doesn't understand quantum mechanics.

 

[Orbitalai]

Anybody who claims to understand quantum mechanics doesn't understand quantum mechanics.

Yes, I guess so. Still would like to have greater insight though. I find it so fascinating, and on top of that it is one of the two branches of the most fundamental sciences we have. And I find cosmology very interesting too, and its pretty hard to understand that without quantum theory. I spend alot of time trying to get deeper insight into it without the mathematics part of it, but I find some parts of it is extremely hard, like symmetries and stuff etc., and it can only ever be superficial without training and understanding of the math. Hence why I maybe should have studied it.

 

[DrBaggy]

Brownian motion is also not responsible for the expansion. Stretching of the space itself is.

You are right about that, there never was any explosion. An explosion is an expansion from a centre pushing things apart, the universe is expanding at same rate everywhere, there is no centre. But there was however most likely in the beginning a rapid expansion, astronomers tend to think it was caused by a field called the inflaton. It stopped however.

Space itself does also seem to cause an expansion of itself. The more space there is, the faster it will expand. This effect was very small at beginning, as the space was not so big. But slowly that effect has become so big that it overcomes the collective gravity attraction of the entire universe, so that the universe is now even accelerating the expansion. If it continues with this rate you will later never see any light at all, since the separation of even close objects will be faster than speed of light. This effect they call dark energy btw., its cause is not known yet.



I am also just an amateur, and have spent countless hours looking into this stuff. Its just too fascinating.

Indeed. Particle physics is much much better understood than large scale things. That is also why lately alot of hints of new particle physics have not come from particles, but from astronomical observations. As they say themselves astronomical studies is racing ahead, while particle physics in many aspects has been stale for 30 years, only confirming the known stuff and coming up with ideas they cannot falsify.

I feel however that judging from humans past ability to discover secrets about the universe I am fairly optimistic about our ability to get good post big bang understanding in a couple of hundreds years.

Not sure if others feel the same, but I find it frustrating to me that since Einstein's insights, physics seems good at describing the mathematical equations that describe particle physics to astonishing accuracy, but shrugs its shoulders as to what those equations mean (I realise the word "mean" may be meaningless, but I feel we ought to have a go!)
For instance, it seems to me that if we have two main classes of particle/wave, one of which cannot reach C because it becomes infinitely heavy, and another class that not only can move at C, but HAS to (in a vacuum). That says to me that the latter class is a wave, and the former loops on itself in some way (string theory fits this, which is why it appeals). But in several books I have read the theorists say "don't think about what this means, feed the data into the equations and they will give accurate answers".

Maybe it's impossible for a 4d creature to understand a 16d universe: we are all "flatworlders". However, I don't think we should stop trying: my instinct is that Feynman and Zen Buddhism are telling us the same thing: there is no such thing as "separateness", it just makes it easier for us to categorise if we act as though there is.

Ok, maybe put Solving the Universe on hold till it cools down a bit.....anyway, we know it's 42

 

[Darren Grey]

We should be happy enough that on this little rock us tiny bags of water are able to string enough electrons through our thought centres to even consider the constitution, origin and fate of the universe in its entirety

 

[DrBaggy]

We should be happy enough that on this little rock us tiny bags of water are able to string enough electrons through our thought centres to even consider the constitution, origin and fate of the universe in its entirety

Excellent point!

On the other hand:

"Ah, but a man's reach should exceed his grasp,
Or what's a heaven for? All is Darren Grey"

As Robert Browning very nearly said

 

[Orbitalai]

but shrugs its shoulders as to what those equations mean (I realise the word "mean" may be meaningless, but I feel we ought to have a go!)

For those effects they have not found a reason for, but only a way to describe, like uncertainty principle, quantum tunneling etc, there are many interpretations. Some are more believed in than others, but when you do the math, they all come up with the same answer. They are hard to falsify though. I think you are wrong, I think many if not all of them think about these interpretations very much, and maybe ways to falsify them.

if we have two main classes of particle/wave, one of which cannot reach C because it becomes infinitely heavy, and another class that not only can move at C, but HAS to (in a vacuum). That says to me that the latter class is a wave, and the former loops on itself in some way (string theory fits this, which is why it appeals).

I am no expert in any stretch of the word, but that way of classifying them seems to be not used so much, and the tables showing the standard model does not seem designed to highlight this difference.
Mosty I get the impression its fermions vs. bosons or generation vs other, particles vs. anti-particles vs. do-not have-anti-particle, leptons vs. quarks, selfinteracting vs. not.

I think string theories aim to expand on the standard model, not replace some of that stuff, much of which has been confirmed to incredible presision.

I mention this because your suggestion seems to change what standard model shows us; that all of them are waves, ripples or other deformation of their field, and are in fact never a particle even if they act as one from time to time, which led people to conclude that they were particles before quantum field theory was discovered. Not sure M-theory even has a field theory yet, I think it wont be done by a looong time, if ever.

As i understand it, all 'particles' travel at speed of light all the time. The more they interact with the Higgs field and get mass, the more gravitons will bump into them and make them sorta zigzak and appear to move slower. (been a while since I last looked at this, could be I remember wrong).

in several books I have read the theorists say "don't think about what this means, feed the data into the equations and they will give accurate answers".

Yes, sadly nature's laws does not seem to be designed to be understood intuitive by our brains. Especially if M-theory ends up being a theory.

there is no such thing as "separateness", it just makes it easier for us to categorise if we act as though there is.

Yes, hehe. So have I understood it correctly that all wavefunctions in a field can be combined theoretically into 1 major that describes all all its 'particles'? Sounds kinda connected to me, even if it does not mean they interact much with each other.

Ok, maybe put Solving the Universe on hold till it cools down a bit.....

I think that we actually live in the perfect time.

Not so late that all we can see is our own local galaxy group, or later so we can only see our own galaxy and might have concluded that it is the entire universe. Will also not be funny when the sun goes nova or other bad stuff that could be waiting on us.

Not so early that we would not have found dark energy.
Wait till we can observe even less, sounds a little Zen, but no thanks.

anyway, we know it's 42

Yeah!!! - oh wait, if that IS the answer, does that mean the superhighway will be made.

Not sure the mice will be happy with it either..

 

[DrBaggy]

For those effects they have not found a reason for, but only a way to describe, like uncertainty principle, quantum tunneling etc, there are many interpretations. Some are more believed in than others, but when you do the math, they all come up with the same answer. They are hard to falsify though. I think you are wrong, I think many if not all of them think about these interpretations very much, and maybe ways to falsify them.



I am no expert in any stretch of the word, but that way of classifying them seems to be not used so much, and the tables showing the standard model does not seem designed to highlight this difference.
Mosty I get the impression its fermions vs. bosons or generation vs other, particles vs. anti-particles vs. do-not have-anti-particle, leptons vs. quarks, selfinteracting vs. not.

I think string theories aim to expand on the standard model, not replace some of that stuff, much of which has been confirmed to incredible presision.

I mention this because your suggestion seems to change what standard model shows us; that all of them are waves, ripples or other deformation of their field, and are in fact never a particle even if they act as one from time to time, which led people to conclude that they were particles before quantum field theory was discovered. Not sure M-theory even has a field theory yet, I think it wont be done by a looong time, if ever.

As i understand it, all 'particles' travel at speed of light all the time. The more they interact with the Higgs field and get mass, the more gravitons will bump into them and make them sorta zigzak and appear to move slower. (been a while since I last looked at this, could be I remember wrong).




Yes, sadly nature's laws does not seem to be designed to be understood intuitive by our brains. Especially if M-theory ends up being a theory.



Yes, hehe. So have I understood it correctly that all wavefunctions in a field can be combined theoretically into 1 major that describes all all its 'particles'? Sounds kinda connected to me, even if it does not mean they interact much with each other.



I think that we actually live in the perfect time.

Not so late that all we can see is our own local galaxy group, or later so we can only see our own galaxy and might have concluded that it is the entire universe. Will also not be funny when the sun goes nova or other bad stuff that could be waiting on us.

Not so early that we would not have found dark energy.
Wait till we can observe even less, sounds a little Zen, but no thanks.



Yeah!!! - oh wait, if that IS the answer, does that mean the superhighway will be made.

Not sure the mice will be happy with it either..

What can I say Orbitalai that's a pretty comprehensive response, and I have a feeling you are more of an expert than you are letting on! You may be right about the experts not just "doing the maths", but in the conversations I have had with PhD's they shrug their shoulders when it comes to interpretation. Maybe that's right: we do the maths, get the right answers and don't worry about the interpretation. However, I'm a great fan of Roger Penrose and others who try to ask "what do those equations tell us".

I must admit it's pure prejudice (and a Zen experience) that makes me want to make everything fit together. We see a complex world arising from a few chemicals, made up from fewer fundamental particles governed by simple equations, so it feels the deeper you get, the simpler it should be, with complexity arising as an emergent property. So then you go from simple electrons/protons/neutrons (which kinda looks like a proton+electron somehow) to the "particle zoo" of up/down charmed/purple spotted Quarks and think what???
I really hope we come to a theory that makes these stupid particles arise from a wave (i know they are all both!) and, yes, to all be interconnected as quantum entanglement, the two slit experiment and Chromodynamics (is that right: the Feynman one) suggest they are. and hopefully our ideas of "particles", "fields" and "quantum effects" will go the way of phlogiston and the aether. Likewise in biology, we have amazing complexity from simple building blocks.

But that's prejudice mainly, and also the fact that physicists have found that "beautiful" equations are usually correct, which to me says there's a fundamental simplicity to the world (or that I'm fundamentally simple!) So whether it ends up with strings, branes (how can we have 14 or 16 dimensions??) or whatever, I hope the meaning of Life, the Universe and Everything will, at heart, be simple and interconnected.

But you are right: we live at an amazing time: late enough to have lots discovered, but still plenty out there to discover.

A bit like a virtual galaxy appearing in under a year.....

 

[Orbitalai]

so it feels the deeper you get, the simpler it should be, with complexity arising as an emergent property.

I total agree, the good part is that is also how it works. There is only 17 fundamental particles (neutron and proton is not among them btw.), might become 18 if graviton is found.

The hundreds of particles from the zoo, is composite particles combined from the 17 fundamentals.

Not only that, but the equations for the standard model, can be written very short.

String theories will destroy that concept badly, another reason to hope it will not someday describe our universe.

I really hope we come to a theory that makes these stupid particles arise from a wave

That is what we have today. There is no particles in quantum field theory. The idea of particles is only used by people not in the know, or for historical reasons.

 

[DigitalDuck]

That is what we have today. There is no particles in quantum field theory. The idea of particles is only used by people not in the know, or for historical reasons.

When I use particles, it's to simplify explanations; it's much easier for most people to imagine particles as most people have held a ball at some point ("it's like that, but much smaller"). While "everything is a wave" is true, it only leaves people asking "a wave of what?"

So the idea of particles should be preserved at higher levels - it's sufficient to explain a lot whilst also being relatively simple. Obviously, when it gets down to quantum scales it's necessary to replace particles with waves propagating through the quantum field to fully explain what happens, but sometimes clarity is more important than truth.

 

[Orbitalai]

When I use particles, it's to simplify explanations;

I understand that. But people who have the slightest interest in these things, get bombarded with extra dimensions, branes, multiple universes, that particles are really strings vibrating in multiple dimensions, holographic universe and lots of weird stuff that baffles their brain much more than waves would do, and might not even be our reality.

But that waves are really our current understanding of what particles is, that brain meltdown we have to spare them. Not sure I really get it, actually strike the first sentence I made here.

Everyone I talked to about this, and most did not really believe it, apparently wild string stuff is much more plausible to them (I wonder why, if we do not even show them the incredible beauty in our current understanding), but those that believed it thought it was really cool, and was glad someone told them.

 

[DrBaggy]

I understand that. But people who have the slightest interest in these things, get bombarded with extra dimensions, branes, multiple universes, that particles are really strings vibrating in multiple dimensions, holographic universe and lots of weird stuff that baffles their brain much more than waves would do, and might not even be our reality.

But that waves are really our current understanding of what particles is, that brain meltdown we have to spare them. Not sure I really get it, actually strike the first sentence I made here.

Everyone I talked to about this, and most did not really believe it, apparently wild string stuff is much more plausible to them (I wonder why, if we do not even show them the incredible beauty in our current understanding), but those that believed it thought it was really cool, and was glad someone told them.

Just looked up the particle zoo in Wikipedia: there are some curious animals there! for instance:

A spurion is the name given to a "particle" inserted mathematically into an isospin-violating decay in order to analyze it as though it conserved isospin

I want my fundamental "particles" (and glad to hear they are just labelled that) to have more gravitas than "spurions"!