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navarro

Senior Member
Messages
863
Hi Everyone. I have two questions for the astronomers /scientists within the forum. I have recently watched one of the plethora of programmes about the universe which are on television.

Question 1. The Doppler effect/shift, I don`t quite understand the reasoning behind this? Answer in laymans terms please.

Question 2. The big bang theory and expanding universe. I assume when scientists refer to this they mean our universe or known universe. Now here is what confuses me in my own simple way I imagine a crossroads in space and me standing there. I look left and right, up and down and see the same thing in every direction. But this is what puzzles me, are there spacial gaps between universes and if this is so and taking the big bang and expansion theory as a premise, are scientists saying that this law is not universal but only applicable within their own universal theoretical limitations? I may not have explained myself very well but answers please in terms I understand. Regds N.
 

aldevis

Surrealist Contributor.
Cafe Moderator
Messages
12,125
Q1: If an ambulance is coming in your direction, the sound of the siren goes sharper, it goes flatter if going away from you.

Q2: Being creationist would help finding an easy answer.
Big Band Theory is a Carla Bley album, though.
 

Andante cantabile

Senior Member
Messages
695
The Doppler effect is named after the Austrian physicist Christian Doppler who described it in 1842. He postulated that the combined effect of the sound waves and the source of these waves moving towards the listener would force the sound waves closer together, and therefore raise the pitch of the sound. The listener of course has to be stationary or at least be slower than the source. The reverse would happen if the source moved away from the listener. Hence the common analogy of the sound of an ambulance. Train whistles are also good for testing this effect. (In 1842 this really was theoretical physics. Nothing was fast enough to allow the theory to be tested). Now, the same happens with light. When the source moves towards you, the waves get closer together and become more blueish (i.e. the blueshift) and they move further apart when the source moves away from you (i.e. the redhift).

The Big Bang does indeed refer to the origins of our universe about 13.7 billion years ago.

The question of multiple universes is rather complicated, speculative, but based on modern physics. Perhaps I could quote Brian Greene. In The Hidden Reality he says that "parallel worlds or parallel universes or multiple universes or alternative universes or the metaverse, megaverse, or multiverse - they're all synonymous and they are all among the words used to embrace not just our universe but a spectrum of others that may be out there".

It helps if you are into superstring theory, general relativity and quantum physics.

I hope this helps Sorry for the length of it.
 

navarro

Senior Member
Messages
863
The Doppler effect is named after the Austrian physicist Christian Doppler who described it in 1842. He postulated that the combined effect of the sound waves and the source of these waves moving towards the listener would force the sound waves closer together, and therefore raise the pitch of the sound. The listener of course has to be stationary or at least be slower than the source. The reverse would happen if the source moved away from the listener. Hence the common analogy of the sound of an ambulance. Train whistles are also good for testing this effect. (In 1842 this really was theoretical physics. Nothing was fast enough to allow the theory to be tested). Now, the same happens with light. When the source moves towards you, the waves get closer together and become more blueish (i.e. the blueshift) and they move further apart when the source moves away from you (i.e. the redhift).

The Big Bang does indeed refer to the origins of our universe about 13.7 billion years ago.

The question of multiple universes is rather complicated, speculative, but based on modern physics. Perhaps I could quote Brian Greene. In The Hidden Reality he says that "parallel worlds or parallel universes or multiple universes or alternative universes or the metaverse, megaverse, or multiverse - they're all synonymous and they are all among the words used to embrace not just our universe but a spectrum of others that may be out there".

It helps if you are into superstring theory, general relativity and quantum physics.

I hope this helps Sorry for the length of it.
Thanks B I`m not into QPs etc. but you have answered my question there is a lot of theoretical speculation. It is a really fascinating area. It puts meaning to the word infinity. Regds N.
 

Andante cantabile

Senior Member
Messages
695
Yea! But wot was arownd b4 the big bang? :confused:
I am not aware that there is a truly satisfying answer to this question. The Big Bang theory answers the question as to how our universe came to be what we perceive it to be. For that purpose it really is very hard to argue with.

If you want to pursue this further, Sir Roger Penrose has come up with a theory of what might have been there before the Big Bang in Cycles of Time: An Extraordinary New View of the Universe. It is at times heavy going (for me, at any rate), and I have not yet finished it.
 

aldevis

Surrealist Contributor.
Cafe Moderator
Messages
12,125
I was going to insist joking on the creationist path, but I realized that people could take me seriously and I could end up leading a new sect of saxophone players idolatrating some vintage horn.
 

BigMartin

Well-Known Member
Messages
3,904
Yea! But wot was arownd b4 the big bang? :confused:
Just in case this was a serious question...

As I understand it (ie not very well), the reason we can't get our heads round this is that we are living in a stage of the universe's life where time seems to be a regular thing that we can measure with hour glasses, clocks, metronomes
and so on. Our intuition about time is conditioned by that. To understand something like the big bang (I nearly wrote "band" there) you have to put your intuition on one side and do the maths. And the maths/physics says that the flow of time is related by the laws of thermodynamics to the state of the matter in the universe (increasing entropy etc). There is no "before the big bang" because time itself started then. And just after the big bang, time didn't work the same way it does now. There were no nice regular processes going on to measure it by.
 

gladsaxisme

Try Hard Die Hard
Subscriber
Messages
3,409
This is in no way an answer to anything but my own thoughts on the universe which you can all laugh at as much as like if you so wish,because they are after all just my thoughts,I have never come across any scientist's ideas of how the universe would look if could take a slice through the middle of it and look at it,ie would it be like a big cake in the shape of a football with matter interspersed evenly throughout it ,or would it be more like a doughnut with all the matter held in what would be the dough and an absolute vacuum of nothingness in the middle or expanding on this would it look more like the largest balloon you could imagine with all the matter contained in the skin of that ballon and a total massive void of nothingness being the empty area of the ballon,now think that the skin of the balloon is in fact billions and trillions of light years in thickness, now imagine that what we perceive as the universe is merely the slightest speck as perhaps a single atom in the make up of the skin of the balloon,it kind of makes me wonder how much we may or may not know about the universe.Now my brains hurting so I'll leave you to ponder that.....John
 

kevgermany

ex Landrover Nut
Subscriber
Messages
21,947
There is no "before the big bang" because time itself started then. And just after the big bang, time didn't work the same way it does now. There were no nice regular processes going on to measure it by.
This is more a limitation imposed by our maths/modelling. True we have no knowledge, and it's just speculation, but there's nothing to prevent there being a before big bang.. After all, how did the known universe get to be in such a compressed and unstable state? There must be a beginning somewhere. Whether we're capable of identifying it, let alone understanding it is anyone's guess.

I found this recent article rather interesting: http://www.bbc.com/news/world-europe-19870036
 

kevgermany

ex Landrover Nut
Subscriber
Messages
21,947
This is more a limitation imposed by our maths/modelling.
How do you know?
A model's a model. No more, no less. For many years people believed there was an end to the earth...

True we have no knowledge, and it's just speculation
And therefore pointless?
Why? Without curiosity we find nothing. Many people think searching for the Higgs bosun is pointless.
There must be a beginning somewhere.
Must there? And if there was, doesn't that mean that nothing happened before it?
Of course. Things aren't always there - in the same way that infinity isn't real.
 

Colin the Bear

Well-Known Member
Messages
13,079
As time was created at the big bang then there is no before. Space and time are the same thing as far as I understand. Everything was eternally nothing, universally connected in no space. No wonder it went bang. It must have been the boredom kicking off.
 

old git

Tremendous Bore
Messages
5,545
I am not aware that there is a truly satisfying answer to this question. The Big Bang theory answers the question as to how our universe came to be what we perceive it to be. For that purpose it really is very hard to argue with.

If you want to pursue this further, Sir Roger Penrose has come up with a theory of what might have been there before the Big Bang in Cycles of Time: An Extraordinary New View of the Universe. It is at times heavy going (for me, at any rate), and I have not yet finished it.
Bleedin ell, neva meant 2 kik thees orf.

Cycles of Time? Doz thet keen were orl dopd?
 

Lorraine

Member
Messages
36
As time was created at the big bang then there is no before. Space and time are the same thing as far as I understand. Everything was eternally nothing, universally connected in no space. No wonder it went bang. It must have been the boredom kicking off.
Yeah - I've always had a problem with this response advocated by Hawkins et al. in the 1990s. The idea that because time didn't exist it is pointless to ask about what came before the big bang, imho, didn't answer the question. And it goes against everything we understand about our universe which is cause and effect. We assume there must have been a catalyst to spark off matter because the concept that 'everything comes from nothing' is one our feeble little brains (well mine anyway) can't grasp.
Either we are looking at the idea in a completely pointless way because our perception and therefore our understanding is skewed - or its there and we will figure it out eventually.
I recommend the Intro to astrophysics courses - run by the Open University - I did a few of these years ago and they were fascinating....
 

Colin the Bear

Well-Known Member
Messages
13,079
Before our universe came into existence, our universal rules of cause and effect cannot apply. Before our space/time came into being there was just potential. Perhaps just energy. Maybe from another dimension. Perhaps it was a 2D universe that became 3D. You'd need the glasses to see it though. Maybe it was plasma, but they use a lot of energy so probably backlit LCD. The whole universe comes into being at a single point. No wonder it went bang. Perhaps misleading to call it the big bang. I suppose it must have been silent. Probably a big flash.

Let there be light.

I get my physics from Star Trek and the Big Bang Theory show so this may not be true, fact or even good science.
 
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