Physics Question

[Bozo Erectus]

I dont get something. You know how astronomers are seeing further and further back in time with more powerful telescopes, and are getting close to the 'Big Bang'? This is the part I dont get: why would photons from just after the Big Bang be hitting telescope lenses now? Theyve been travelling for 12 billion years or so, is that correct? Does this mean that the universe inflated faster than the speed of light, so light from the event is 'catching up' with us?

 

[cairo140]

That's a good question. I would like to know as well. I know there are ways to examine cosmology (the origins of the universe) with things like red shift (looking at the colours of far-away starts to determine their velocity) and examining planet and star cores, but I don't know where this idea of photons coming back now comes from.

 

[Bozo Erectus]

Im sure when its explained, it'll turn out to be something obvious, and we'll both go 'DOH!' and smack our foreheads.

 

[The Capitalist]

That's a good question. I would like to know as well. I know there are ways to examine cosmology (the origins of the universe) with things like red shift (looking at the colours of far-away starts to determine their velocity) and examining planet and star cores, but I don't know where this idea of photons coming back now comes from.

Why bother yourself with cosmology,it is a logic fiction that have nothing to do with science.The role of a scientist is a role of a neutral observer.Nothing else.The rest(cosmology for example) are just for people that like to tell lovely stories to read on your bedside.

 

[Sidhe]

It's a slightly naive question too, but it is still a good question. matter from 3 billion years ago has changed position relatively speaking it's now alot further away from the matter that makes up us than it was a few milliseconds after the big bang, it's not so much the light from these objects catching up with us as hitting us after travelling some pretty huge inflationary distances. There are plenty of websites which explain the big bang, simply look up a few. Light is not confirming our ideas about the big bang as much as radio telescopes are. Look up the microwave background radiation and various other telescopic universe images that do not rely on light.

In answer to your question though there was a period a few millionths of a second after the big bang which explains the size and uniformity of the universe and in fact had to be travelling faster than the speed of light, but it's entirely different from the reasoning in the orgiinal question.

http://www.ncsu.edu/felder-public/kenny/papers/inflation.html

 

[Mise]

I dont get something. You know how astronomers are seeing further and further back in time with more powerful telescopes, and are getting close to the 'Big Bang'? This is the part I dont get: why would photons from just after the Big Bang be hitting telescope lenses now? Theyve been travelling for 12 billion years or so, is that correct? Does this mean that the universe inflated faster than the speed of light, so light from the event is 'catching up' with us?

Obviously, we can't actually see the big bang.

I think what you are referring to is the fact that we can infer a tremendous amount about the big bang by looking deeper into space. A number of mysteries still remain, such as the net baryon number, the cosmological constant, and dark matter; mysteries which originate from the big bang but perhaps have their solutions elsewhere in the galaxy.

Personally I find it fascinating that problems on the plank scale in particle physics can be solved by astrophysics on a cosmological scale.

 

[Shaihulud]

I think you are talking about the "Cosmic background radiation" its the radiation that is theorised to be produced at the moment of the Big Bang. The problem with the ay you resolve it is that you think of the Universe expanding in a directional motion from a point source. Given that the Universe is curved by its gravitional constant, its propable that the remnant of the radiation from the Bigbang is still around us, permeating space around us.

 

[The Last Conformist]

I dont get something. You know how astronomers are seeing further and further back in time with more powerful telescopes, and are getting close to the 'Big Bang'? This is the part I dont get: why would photons from just after the Big Bang be hitting telescope lenses now? Theyve been travelling for 12 billion years or so, is that correct? Does this mean that the universe inflated faster than the speed of light, so light from the event is 'catching up' with us?

The big bang happened everywhere - it wasn't a localized explosion. Similarly, the cosmic background originated everywhere; at any given point we're observing photons that happened to be created at such a distance so as to reach us right now.

The universe may have expanded faster than light during a theorized "inflationary epoch", but that, if it happened, was before the cosmic background got emitted - since then expansion has been slower.

 

[The Capitalist]

To Bozo Erectus:

If you want to know fully about the science of Astronomy.Study Optics,and a little thing called Thermodynamicfor starters.Then read many theories.Of course you might want to know Newton's laws of mechanics too as well.

 

[Sidhe]

To Bozo Erectus:

If you want to know fully about the science of Astronomy.Study Optics,and a little thing called Thermodynamicfor starters.Then read many theories.Of course you might want to know Newton's laws of mechanics too as well.

Id skip newtons laws of motion and just read Einsteins theory of relativity, that way you'll understand what they mean by curved space. You don't need to know jack about thermodynamics either really. It's all fairly simple physics without too much need for profound understanding. It's only when you start asking questions like why does matter exist in the universe and why is the hubble constant increasing that you need to know more. the basic big bang is big explosion --> expansion ---> still expanding microwave radiation appears to be pretty uniform confirming the Big Bang theorie's initial ideas.

 

[The Capitalist]

Id skip newtons laws of motion and just read Einsteins theory of relativity, that way you'll understand what they mean by curved space. You don't need to know jack about thermodynamics either really. It's all fairly simple physics without too much need for profound understanding. It's only when you start asking questions like why does matter exist in the universe and why is the hubble constant increasing that you need to know more. the basic big bang is big explosion --> expansion ---> still expanding microwave radiation appears to be pretty uniform confirming the Big Bang theorie's initial ideas.

I c,well i did indeed left out Einsteins theory,but was stating for starters, by saying that you must read alittle of Newton's laws of mechanics to understand what Einstein was refuting.I find that studying histories of the scientific development in the order of the past to the future as a way to understand one theory killing off other old theories in order to understand why the existing paradigm exist today.It easy to admire the fencer(Einstein) but fallacious when you see the opponent being obliterated.

 

[Sidhe]

I agree but Newtons laws are fairly obvious in todays world, even laymen know that the force of gravity is proportional to mass and distance(inversely proportianl to distance though obviously) That's all you really need to know. The only thing Einstein law expands on is the bending of space time which is the cause of the attractive forces, otherwise Newtons laws all work fine for practically all classical experiments. If you want to answer why the suns Umbra an penumbra in an eclipse appear to be bent out of shape from what one would expect then you need general relativity. Reading inflationary theory makes very little recourse to either Newtonian or Einsteinian mechanics, It's mostly conceptual. Thus read any old web site on the big bang and you'll understand it if you have a half decent education and if you want to understand the intracacies then start looking further.

 

[Perfection]

I think you are talking about the "Cosmic background radiation" its the radiation that is theorised to be produced at the moment of the Big Bang.

CMBR is from about 300,000 years (IIRC, the number may be off) after the Bang.

 

[Lambert Simnel]

I agree but Newtons laws are fairly obvious in todays world, even laymen know that the force of gravity is proportional to mass and distance(inversely proportianl to distance though obviously)

Obviously ? Me and Newton keep getting fixated on the idea that the gravitational force is inversely proportional to the square of the distance between the two objects. But maybe that's just us ?

 

[Souron]

I dont get something. You know how astronomers are seeing further and further back in time with more powerful telescopes, and are getting close to the 'Big Bang'? This is the part I dont get: why would photons from just after the Big Bang be hitting telescope lenses now? Theyve been travelling for 12 billion years or so, is that correct? Does this mean that the universe inflated faster than the speed of light, so light from the event is 'catching up' with us?

I am not sure what the rate of inflation was right after the big bang, but it is largely irrelivant.

It's not that the photos are catching up to us; that does not make sence. They simmply started at 12 billion light years away.

The key concept to remmember is that although the universe was very dence, it was not at all small. In fact it might have been infinate.

 

[El_Machinae]

Bozo - one hint that might help is that the Big Bang was a 4D event, not a 3D event. It's not like the explosion occured in a point of space "over there", it occurred in point of 4D space "over there".

 

[Sidhe]

Obviously ? Me and Newton keep getting fixated on the idea that the gravitational force is inversely proportional to the square of the distance between the two objects. But maybe that's just us ?

fg=gk m1+m2/r^2 trouble is if I write it like this no one knows what the hell I'm talking about, I do however at least credit people with the intelect to know that the further two objects apart the less the gravitational effect so I rarely feel the need to patronise people by pointing this out, thus if I say that gravity is proportional to mass and distance, I think your average 10 year old knows that bigger means stronger pull and further apart means weaker pull. this aint rocket science you know

 

[Lambert Simnel]

fg=gk m1+m2/r^2 trouble is if I write it like this no one knows what the hell I'm talking about, I do however at least credit people with the intelect to know that the further two objects apart the less the gravitational effect so I rarely feel the need to patronise people by pointing this out, thus if I say that gravity is proportional to mass and distance, I think your average 10 year old knows that bigger means stronger pull and further apart means weaker pull. this aint rocket science you know

I'd put some brackets in that thar equation, pardner, or we'll be thinking your dividing jes' your second mass by that thar distance squared, when we knows you'll really be wantin' to divide the sum of them masses.

Hell, there was another thread in which you got it right first time, so I don't doubt for a minute that you know what you're talking about. It was just a bit funny that you were using terms like "obviously" and then got it wrong (let's be honest, now, inversely proportional to the square of the distance is not the same as inversely proportional to the distance), espesh in a thread marked "physics question". Gah, when I was a physics student, we would wind each other up all day long about this sort of trivial error - what wags we were! What fun we had!

 

[Sidhe]

See I miss that being on an OU course I don't get so much pupil pupil interaction. However if I ever feel the need to derive schrodingers equation from first pricniples do me the kindness of avoiding pointing out the errors as It could take several years for me to write it perfectly . f(g) g(k) f(x') g(x) with a decent maths package the brackets are unnecessary. Shame they don't have a maths font here anyway if you arent happy just write it out yourself.

OK f(g) = g(k) (m1+m2)/r^2 oh for a ruler

 

[Bozo Erectus]

Bozo - one hint that might help is that the Big Bang was a 4D event, not a 3D event. It's not like the explosion occured in a point of space "over there", it occurred in point of 4D space "over there".

Or it occurred everywhere at once, right?

Thanks for the replies everybody, Im slightly less in the dark.