The speed of light, etc
 

The scientists are often telling us that the various space telescope have observed light emanating some “short” time after the so-called “big bang”.

Is there a brainpower on this forum who can explain the paradox that I describe below.

For this discussion, two axioms apply:

1. There was a big bang c. 13.5 billion years ago;
2. The material of the universe has expanded ever since.

Taking one of the observations as an example of my point (no citation provided), we are told that we can observe a galactic event that took place 13 billion years ago (as measured by red-shift of the received light frequency).

But if our portion of the universe hadn’t yet been expanded to, how can we see light from 13 billion years ago unless one of the axioms is wrong?

Also this stuff about “Space-Time”. Is n’t time entirely relative to an observer and thus nothing to do with space?

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It's only Monday and you just made my head hurt. Not happy with you Sir!!!!!


:bsmack:

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This may (or may not) clarify things…

https://science.nasa.gov/mission/webb/big-bang-q-and-a/

And this expands upon it…

https://www.edge.org/response-detail/27054

And just to confuse you further

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Don't worry about it. We live in a universe inside a gigantic black hole which is expanding in an external universe which is also expanding. I had this confirmed by Keith at my local the other night. Keiths also captain of the darts team so has many strings to his bow.

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And here’s the real noggin buster

It’s the space between galaxies that’s expanding and pushing them galaxies apart and that expansion is occurring faster than the speed of light. This is what gives us the term ‘the observable universe’

There are elements of the universe that we will never observe as it’s light will never reach us

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I read that too, and it encourages me. I doubt the big bang theory; I'm of the school that everything has always been there, in one form or another.

In that case, we will always be able to "see" events that occurred 13 billion years ago. There'll no doubt be a limit if Mr M's point holds good about expansion occurring faster than the speed of light.

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Thing is science can not even decide if light is a particle or a wave without that knowledge how can you take anything related to light with anything other than a pinch of salt

The only answer I want an answer too is where all the energy came from. From what I can find there is only one theory that does not require a pre existing energy source and that isa Quantum field theory that theorises Quantum Flutuations where energy just pops into and out of existence. Yes as convenient as Dark Matter and Dark Energy used to allow for the fact they had it all totally wrong and thought there was not enough energy or matter for the universe to still be expanding so they said oh it must be there we can not see it

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If you accept my theory that everything has always been there in one form or another, (and the things that it does) then it gets easier. And, indeed, it's logical.

On the question of light, I address this problem in my mind for an exclusive half-hour each day. It's clear that a source of energy emits light, which is why we can't see each other in the dark. If our eyes were IR sensitive, we could see each other. So there we have the proof that light is a waveform generated from energy.

Next, is light a particle? They seem to have isolated individual photons but they are said to be massless - and I believe that. Why? If, like the electron, photons are elementary particles (electron has mass - something elementary must have mass), then there is no need to explain their behaviour - like being bent by gravity. Rather interesting read: https://profoundphysics.com/if-photo...have-momentum/

Btw, "always been there" then there is no "God the Creator".

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It’s not about that scientists can’t decide , it’s that light behaves differently due to something called the wave-particle duality

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Now even light is turning trans lmao

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Does chaos theory come into this as well? Because trying to understand that when I was a very serious teenager, whilst also attempting to understand the difference between existentialism and nihilism, gave me a similar headache.

Jean-Paul Sartre and Arthur C Clarke had a lot to answer for. <<sigh>>


Sorry if my ramblings aren't relevant but, really, I don't think anyone has ever come up with a universally accepted definitive answer regarding what happened all those eons ago.

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I have come up with a "definitive answer", but universal acceptance would put a lot of people out of work. As in, Photons and Electrons are fundamental particles, along with a number of -uons and -ons of various sorts that, in chaos, produce more tangible matter.

And, they have always existed (how could it not be so?).

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all the scientists I have ever spoken to avoid like the plague the question "what come before the big bang" because basically it is a infinite question which can not be answerd.

Infinity blows my mind. I know the theory or cyclical the symbol figure 8 thing but we are here the matter we see is here it has always existed (unless of course our idea of reality is wrong and you can get something from nothing) but then even if there was nothing there is a infinite past of nothing no start. I am rambling now too haha

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Infinity is a fine concept when you align it, as mentioned before, with the highest positive number or the highest prime number.

To my mind, this answers it all. Space is infinite and matter recycles as gravity does its work. Indeed the entropy theory falls flat because although things cool down, they collide with other things which releases energy, particles, matter etc.

Simples. Or what?

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Yeah but as I said that answers everything other than give it a beginning

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OMG why did i look at this thread, i now need to have a little lie down

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One does not discount the other.
There seems plenty of evidence the big bang happened.
However, whatever went "bang" was already in existance.

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and there within is the crux .

What ever was there before ( even if it is matter in an ever expanding contracting exploding universe) must always have been there which to our linear mortal brains is impossible

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One i haven’t got my head around yet is how the Big Bang and Big Crunch theories work together, according to the second law of thermodynamics the total amount of entropy in an enclosed system (which the universe is) can only remain constant or increase never decrease.

So, if if entropy increases in a big bang Big Crunch scenario where does it come from ? & if entropy remains constant what happens to matter if it crosses the event horizon of a black hole ? It must come out? Hawkins radiation ?

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Can someone explain how something infinite (the universe) can be expanding?

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The universe in theory isn't infinite what is is expanding into is . Although even nothing is something and if it is nothing it goes on forever (maybe) re end scenes of Men in Black

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So what is it expanding into and how would you know where the edge of the universe is and when you'd crossed over to the infinite expanse outside?

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The universe can’t expand into something because it’s everything , there is no edge

https://www.newscientist.com/lastwor...xpanding-into/

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I've worked that one out - at least to my satisfaction. There must be somewhere in space where no matter exists (yet). So I should be theoretically able to get there. What would I see? I believe you'd see everything you see now because the totality of the material universe bends light.

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How do you know?

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Let’s dissect this for fun

1. Somewhere in space where no matter exists would imply containment and the universe expanding into something
2. If you can’t travel faster than the speed of light and galaxies are being pushed apart faster than the speed of light how do you reach this area ?

Mind you it could be turtles all the way down for all we know….

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Speed of light (in a vacuum) is a constant therefore relative to everything , however there is no reference frame that can be applied IIRC Newton & Einstein stated this (although I may have butchered it somewhat)

Point 2 those bloody turtles again

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"The turtle* moves!"

*Great A’Tuin

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Cosmic turtles and elephants....... just saying.

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Imagine the universe like a giant, stretchy balloon with tiny dots drawn on it. These dots represent galaxies.


1. The Universe Expands Like a Balloon

At the very beginning, the universe was tiny, hot, and dense. Then, it started expanding, like blowing up a balloon. The galaxies (dots) weren’t moving through space; instead, space itself was stretching between them.


2. The Light We See Started Its Journey Billions of Years Ago

When we see light from a galaxy that’s 13 billion years old, it means that light left that galaxy 13 billion years ago. But back then, that galaxy was already far away from where we are now, the universe had expanded a lot even by that time.


3. Space Has Stretched the Light on Its Way to Us

Light always travels at the same speed (about 300,000 km per second), but because space itself is expanding, the journey the light had to take got stretched over time. This also makes the light appear redder (this is called redshift). Light moving away appears bluer. This is the light version of a doppler in audio (where an police car siren appears to change frequency and pace as the car approaches and then goes past).


4. The Galaxy Is Much Further Away Now

Even though the light has taken 13 billion years to reach us, the galaxy it came from isn't 13 billion light-years away today. It's much further, maybe 30+ billion light-years away! That’s because space has been expanding the whole time.


So, Why Can We See It?

Even though space was smaller back then, there was already a path for the light to travel. That galaxy wasn’t in the exact spot where we are now, but its light had enough time to reach us as space stretched.


Think of it like this:

If a friend sends you a balloon with a drawing on it, but the balloon inflates while the drawing is traveling to you, the picture still arrives, it just looks stretched out.

That’s what happens to light in our expanding universe!

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The other way to think of the universe expanding is the raisin bread baking analogy
It’s not the raisins moving but the dough between them expanding

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By definition we are at the centre of the observable universe.

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If the universe is expanding, and everything is moving away from everything else, how can we be on a collision course wth Andromeda?

I've watched every episode of How The Universe Works on Discovery and still don't understand it.

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If the universe can be likened to an expanding balloon, with everything travelling away and apart, is there still something at the centre and what is surrounding those galaxies that have travelled the furthest, is there no limit to the 'space' we are all expanding into. Hope it's not finite eventually causing the balloon to implode
Blooming heck, another headache and am due to at hospital soon.

Off to have a lie down in a dark room.

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The expanding balloon analogy is totally flawed, imo. One has to consider what is causing the universe to expand. It could be one of three choices:

1. A big bang, so big and sufficiently "recent" for expansion to still be occurring.

2. An unknown process where matter is being spontaneously created and filling in the universe. Why the latter (so-called Dark Matter) should cause expansion when gravity might suggest otherwise is beyond me; and I haven't found that question addressed by the scientists.

3. We haven't go a bloody clue what's really going on. Hence my reversion to logic.

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You have missed 1 unless you throw creation in as an unknown process

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Yeah - but who/what is the creator? If there was one, I moot that the creator is now dead. If there wasn’t one, the universe has always been there. If there was one, who created the creator? Etc.

I would like to think that a good dose of logic goes a long way! But, thank you.

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Or…

As put forward by Lee Smolin in his book "The Life of the Cosmos".

- Every time that a black hole is created, a new Universe is formed springing from the BH singularity
- Therefore, the Big Bang of our universe is interpretated as one of such black hole creations
- All the material that falls into the Black hole, ends up in the Baby Universe

From - https://www.physicsforums.com/thread...plained.58067/

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Archery darts is real but not that common, even then a bow only has one string.

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Because Andromeda can be moving faster than the expansion. Imagine you are running down a corridor that is getting longer, as long as you can run faster than the expansion you will get to the end.

The noggin scratcher is if the edge of the universe is expanding faster than light then you can't even SEE what is beyond, let alone get to it.

I can answer some questions but I'm not going to be defending the truth of the big bang theory - if you don't believe fine I don't care. All cosmology is nuts -- scientific or otherwise, but some of it has empirical backing.

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Re: The speed of light, etc
 

The universe is seen to be expanding, if you run it in reverse it looks like it came from a point. That is empirical backing.

There are other problems with the model but that bit is uncontroversial.

Re: The speed of light, etc
 

The "Big Bang" is highly controversial, imo. The expansion has an empirical basis of observation of the red-shift of light from receding galaxies. There is some evidence that the expansion is taking place at an accelerating rate, which is not consistent with big-bang.

The scientists are beginning to bottom out what the elementary particles do and how they combine in chaos to create matter as we know it. We are made of that matter and our molecules and bodies all hang together notwithstanding the atomic forces going on in said atoms/molecules.

Eventually, I expect all that research to reach a hard stop when everything about matter, elementary particles is known - in the frame of the tangible universe.

The rest will be speculation - like how were the elementary particles created? Have they always existed and were never created? After all, without these elementary particles, we couldn't be having this discussion.

Re: The speed of light, etc
 

Well the thing about opinions is everyone has one.
There is certainly some debate over it, but "highly controversial" ? Not really.

The simple fact is we dont know, and since we cannot time travel, almost certainly never will.
All we can do is build theories that match the things we know and/or can observe. Those theories change over time.

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You're absolutely correct. My brain skipping ahead and leaving the fingers behind! Thank you for correcting :)

---------- Post added at 21:58 ---------- Previous post was at 21:56 ----------

If that was all it that was needed to understand the universe, we would all be experts!

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I think the most controversy lies in how the proposed big bang came about and what, if anything, preceeded it. The true answer is possibly beyond any current understanding.

Re: The speed of light, etc
 

The stuff in the universe has always been there should be within general understanding. I wonder what the reason is for resistance to that notion?

Re: The speed of light, etc
 

The old logical paradoxes are. If the universe is eternal why hasn't everything happened yet? If the universe had a beginning then what caused it.

Re: The speed of light, etc
 

Surely, if the universe is eternal, anything can happen within the bounds of the laws of physics (whatever those bounds may be). If there's a future (which there obviously is) there is still time for more things to happen.

The logic of the universe that I'm putting forward is that it cannot have been created because anything that might have caused its creation then has to be explained; which it cannot be.

The big bang is not precluded by my logic it's just that it needn't have happened. If it did happen, then logically I surmise that it happened as soon as the singularity had formed because the elementary particles in there would be in chaos from which the instability could have occurred. But it comes back to one thing: The material of the universe has always existed together with any means of creating matter to replace that which is mutually destroyed.

Re: The speed of light, etc
 

Right so you are advocating a steady state model. https://en.wikipedia.org/wiki/Steady-state_model

It may be true but we have no understanding how the additional matter would come into existence or any confirmation that it happens.

Re: The speed of light, etc
 

Thing is when something can not be explained literally nothing can be disclaimed therefore it might have been created no one can say for sure it was not . They can profess it loudly often violently but no one knows

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Re: The speed of light, etc
 

This reasoning is not logical.

I get where you’re coming from, that there cannot ultimately have been a first moment, because spontaneous creation ex nihilo defies every physical law we have ever conceived of. But it does not follow that this present universe is eternal.

Its cause however may have originated with an eternal source. Discussion of that is the purview of philosophers and theologians, at least some of whom seek meaning within creation as a means of getting at who or what the eternal cause of the universe is.

I have always openly been Christian on this forum so my position on who the first cause of this universe is, is hardly a secret. But I don’t want to bend this into a religion thread - the discussion of celestial mechanics is quite interesting enough, and besides, I’m on holiday. :D

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Particles are generated in supernova however these are from the energy already existing in the star. Not additional things entering the universe. Or so is understood.

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On the balloon analogy:

That just doesn't wash. In that analogy, the matter in the universe is on the outer perimeter with nothing inside. The universe we are observing is full of stuff. What have I misunderstood?

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The balloon analogy does have problems but there isn't really a better one. You need to learn the math for a better understanding - which I never have done btw.

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You're probably right in that it should have matter represented inside it also, a bit difficult with a balloon. It just shows rather crudely that everything is moving away from everything else. That said it's a 4D (apparently) representation of space-time not just space so perhaps the inside is the time vector and the surface represents 3D space. Difficult to represent 4 dimensions using 3.

Re: The speed of light, etc
 

But what the heck is "space-time"? 3D is quite simple, with a force causing or having caused expansion. Time in this context is the number of time unit (seconds, minutes, years, etc) for a galaxy to move from 3D location "A" to 3D location "B".

In my assessment, for what it is worth, "space-time" is a confection of convenience for scientists who know quite a lot about the square root of all this, but not the bit underneath it all.

"Time vector" - don't we all understand this as time moving in one direction only? As in forwards? It has to be measured by some entity that can do such measurements or imagine them with a sound basis in fact. "Space-Time" - includes a "time vector"? Might as well be a triaxellated amplification of a sub-space message from Starfleet.

Imo!

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I think someone mentioned the raisin bread analogy as an alternative, which I actually think is a better one as that does describe for matter on the inside.

Re: The speed of light, etc
 

Do the raisins expand in space-time? When an analogy is provided, it's usually intended to simplify a more complex situation to help understand what's going on. But really (and absolutely), no such analogy has any bearing on the universe's forces.

That's why I say we should apply logic to the question of the speed of light and what we can see in the universe.

The frequency shift of light emanating from a moving object proves (to me at least) that the speed of light is fixed.

In the theory of accelerating universe expansion, the logical situation is that somewhere, everything is moving away from us (ignoring local gravity effects) and some galaxies are approaching recession speeds that cannot be measured with existing detection systems. If the universe's expansion is truly accelerating, then the corollary is, that, relative to us as an observer, some galaxies are receditn at a speed faster than light. A lot of bottoming out still to be done!

Re: The speed of light, etc
 

Well, that’s a fascinating point, and it touches on some of the fundamental aspects of relativity and cosmology. But let’s break it down carefully.

You're absolutely right that analogies, while useful for simplifying concepts, don't alter the fundamental laws of physics. They help us build intuition, but ultimately, the universe follows mathematical principles that don;t depend on our human need for simplification.

Now, regarding the speed of light, yes, the Doppler effect, or more specifically the redshift of light, is strong evidence that the speed of light is constant. This is central to Einstein’s special relativity, which tells us that the speed of light in a vacuum is the same for all observers, regardless of their motion or the motion of the source of the light.

As for the accelerating expansion of the universe, this is where general relativity comes into play. Space itself is expanding, and that’s not the same as objects moving 'through' space. When we talk about galaxies receding from us faster than the speed of light, we’re not violating relativity because it's not the galaxies themselves moving at superluminal speeds through space; rather, the space between us and them is expanding. This means that light from these galaxies will nevre reach us, because the fabric of space is stretching too quickly for the photons to make headway.

So, in a way, we have a sort of observational horizon, the so-called 'cosmic event horizon'. Beyond this, light from galaxies can’t reach us because space is expanding too fast. This is a direct consequence of the universe's expansion being governed by what's called 'dark energy', which is driving this acceleration.

Now, your intuition that we still have a lot to work out is absolutely correct! We don’t yet fully understand what dark energy is, or why the universe’s expansion rate changed over time. But the mathematical framework of relativity does an incredibly good job of describing what we 'can' observe. But there's nothing to say that what we can see is everything that is there.

So yes, there’s definitely a lot of bottoming out still to be done, but people far more clever than myself making good progress, I should think.

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Correct, there is no certainty it exists. It is just the best explanation (that dark matter does not interact with light, but does have mass, as something is holding things together) that fits the driven theories used in physics (Newton’s laws of motion and Einstein’s theory of relativity). Keep in mind dark matter has not been show horned into the theories, more the observations in relation to the theories show that something is missing. It’s the most logical answer to what is being seen.

The other option is that physics needs a new theory, such as Modified Newtonian Dynamics.

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Although reading this thread is still giving me a headache :) I find it fascinating, and I am never surprised, by our member's depth of knowledge when they get to discuss/debate subjects outside of the normal scope of the forum. Respect to you all. :nworthy:

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Nothing can travel faster than light in space/matter. Space creation isn't subject to this limitation, I'm not pretending to understand it, the maths presumably allows it to be true.

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Because the galaxy’s absolute velocity is not greater than the speed of light. The distance between that galaxy and us may be increasing at greater than the speed of light because we are moving away from the galaxy at speed, just as it it’s moving away from us. But neither object is moving at greater than light-speed if observed from a fixed point.

There is a concept called the ‘future light cone’ - the region of spacetime within which nothing is moving at greater than light-speed relative to us. Anything light-emitting within this region can be observed by us. But anything whose speed relative to us exceeeds light-speed, was never within our future light cone, and never will be.

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OK. <, sigh>> Skip to my final comment and don't feel you have to read/reply to this as it's probably a silly question and, as before, being totally irrelevant.

If there was a straight line from A through B & C to
point D. (Have I lost you yet)

1) I am on point A with a speedometer oh and a mahoosive telescope.

2) If I were able to see points B & D, point C being invisible (big bang or whatever) and .......

..... I can see B & D are moving apart from each other at the speed of light what would my speedometer register as the relative speed that they were travelling apart...... I am assuming super dooper planets could move that fast :dunce:

Give up reading now unless you want the same headache as I have.

3) My head is seeing 2 cars, driving in opposite directions, passing at 30 mph surely they would be moving apart at 60 mph

Off to go and lie down in a dark room.

Add// Just realised I'm probably confusing the speed of light with the speed of sound but I have spent so much time pondering about all this that I blowed if I'm going to delete the sodding post!!!!!!!!!!

Re: The speed of light, etc
 

Chris wrote:

OK - I can buy that. If we could be still while our galaxy was moving in space (not "space-time - what is that?) then the receding galaxy would not be moving away from us faster than light. That is a thought experiment because we don't know (someone might) how to become still/motionless in space.

Re: The speed of light, etc
 

If you’ve not come across the term ‘spacetime’ then you haven’t a cat in hell’s chance of understanding any of the issues you’re raising here (not that I’m presenting myself as an expert either, you understand).

In Einsteinian physics, space and time are not separate concepts. Time is measured as a fourth dimension of space. A four-dimensional spacetime model is essential for understanding relativistic effects, which are not mere mathematical oddities but have real-world applications (in the operation of GPS for example).

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I’m getting a headache but only because I don’t know why I’d be able to see B and D but not C, if A, B, C and D are all in a line together :confused:

As for point 3, yes, two cars traveling through town at 30mph in opposite directions are increasing the distance between them at a rate of 60mph, but neither car is traveling at 60mph and so neither car is breaking the speed limit.

Likewise, two galaxies traveling in opposite directions at 75% of lightspeed are increasing the distance between them at 1.5x lightspeed, but neither galaxy is actually traveling faster than light and therefore neither of them is breaking the universal speed limit.

If you were an observer located in either one of these galaxies, you would never be able to see the other galaxy because the light emanating from each could never reach the other (the light would have to travel at 1.5x lightspeed in order to do so, and it can’t).

Re: The speed of light, etc
 

Thanks for your patience Chris and sorry about the headache. I can't see point C as it's apparently everywhere and was using point C as the starting point for the 2 things that are travelling away from each other.

I saw the following video by Brian Cox, explaining cosmic inflation, when it was first aired and since this thread started I have watched it again and keep hoping that one day there will be an explanation that I can comprehend.

https://www.youtube.com/watch?v=BD0r2Xfgh_E

Re: The speed of light, etc
 

Wow yes I guess it is!!

Its all fascinating..... Thank you for the page!!