How can radiation from the Big Bang come from all directions?

[dr-spock]

If radiation from the big bang has been traveling away from it's origin, how can it arrive at the same point from opposing directions?

 

[marcus]

The CMB radiation did not originate at the start of expansion. That is the most ancient light and we detect it coming in roughly the same from all directions. It started on its way around year 370,000 when the hot gas filling space cooled enough and thinned out enough to become transparent.

I don't understand the problem. Why shouldn't it come from all directions?

 

[Orodruin]

If radiation from the big bang has been traveling away from it's origin, how can it arrive at the same point from opposing directions?

I believe you have a very common misconception about what the Big Bang was. The Big Bang was not an explosion at a point in space which threw out material in all directions. It is the start of the expansion of space itself from a very small size and it therefore did not happen at a point in space, but occurred everywhere at once. Since it happened everywhere, in particular it happened at the places in the universe where it would take exactly the age of the universe for light to reach us (modulo marcus' comment that the CMB did not really release at time zero). The CMB from positions which were closer has already passed us and the CMB from places further away might reach us later or never depending on the current expansion of the universe.

 

[bapowell]

If radiation from the big bang has been traveling away from it's origin, how can it arrive at the same point from opposing directions?

This might help: https://www.physicsforums.com/insights/poor-mans-cmb-primer-part-0-orientation/, in particular, the discussion surrounding Figure 2.

 

[Mantuano]

From _inside_ an explosion its energy comes from everywhere around any point. We are nor have never been outside, so it is completely logical that CMB comes from all around us.

 

[phinds]

From _inside_ an explosion its energy comes from everywhere around any point. We are nor have never been outside, so it is completely logical that CMB comes from all around us.

The big bang was not an explosion.

 

[Orodruin]

The big bang was not an explosion.

As pointed out in #3 already.

From _inside_ an explosion its energy comes from everywhere around any point. We are nor have never been outside, so it is completely logical that CMB comes from all around us.

Please read the entire thread before replying. In particular when you are not familiar with the subject on a sufficient level.

 

[phinds]

As pointed out in #3 already.

OOPS. I"m usually more careful in reading threads.

 

[slatts]

I believe you have a very common misconception about what the Big Bang was. The Big Bang was not an explosion at a point in space which threw out material in all directions. It is the start of the expansion of space itself from a very small size and it therefore did not happen at a point in space.

I believe you're using "space" in one of two possible senses here, as the immaterial separation between objects, or between an object and its components. Where this gets confusing is that it had always been generally taken to mean the immaterial expanse beyond all objects, as well. The more specialized meaning you're employing is scientific, since science relies on evidence (real or hypothesized), but I think that people making a "beginner" post will tend to be using the more general meaning, which is much older. If there are mathematical or other reasons why you think I might be mistaken about this, I'd appreciate it if you'd bring them to my attention.

 

[phinds]

... it had always been generally taken to mean the immaterial expanse beyond all objects, as well.

There is no such thing as "beyond all objects" according to the Cosmological Principle.

 

[slatts]

There is no such thing as "beyond all objects" according to the Cosmological Principle.

Well, yes, but the descriptions of the Cosmological Principle rely heavily on the term "universe", which, being a compound word (from Latin "unus versus", or "all together"), is very likely to be a newer word than "space" (from Latin "spatium", or "space"). Scientific concerns have found expression at least since Anaximander, but people had been talking plenty earlier than that.

Understand, I'm not trying to knock Ordurin's main point, which is that the Big Bang was more temporal than (in the scientific sense) spatial: I'm just saying that implying that space was created, or that all of space expanded, can confuse people who are not fully aware that the word's being used in a more recently specialized sense. "Outer space" was the usual way to differentiate the variety that was felt to be unbounded even as recently as my own childhood, and, of course, its own bound (the inflating region) was hypothesized (with some supportive evidence) much more recently than that.

The failure of that 20th-Century differentiation is probably what has people failing to differentiate the "between objects" part of space from the "beyond objects" part of it at all: Unfortunately, I'm sure it also has a lot of people who glance at scientific matters concluding that science includes more mystical gabble-de-gook than it really does.

 

[Mantuano]

As pointed out in #3 already.

Please read the entire thread before replying. In particular when you are not familiar with the subject on a sufficient level.

Yes you are right, it is not if you mean a _chemical_ explosion, but some name has to be given to such an energy burst, and even the "bang" word relates to sound, so the word "explosion" is as valid as any other to describe that. Thanks.

 

[phinds]

Yes you are right, it is not if you mean a _chemical_ explosion, but some name has to be given to such an energy burst, and even the "bang" word relates to sound, so the word "explosion" is as valid as any other to describe that. Thanks.

No, it is not. "Big Bang" was given as a dirisory term and is now just a name that has a specific meaning. "Explosion" also has a specific meaning and is NOT one that is appropriate as a name for what we call the "big bang".

 

[slatts]

"

No, it is not. "Big Bang" was given as a dirisory term and is now just a name that has a specific meaning. "Explosion" also has a specific meaning and is NOT one that is appropriate as a name for what we call the "big bang".

Phinds is right on this one. As Guth points out in The Inflationary Universe , if The Bang's closest resemblance had been to an "explosion", that part of the Big Bang's oldest layers which has turned into visible light would be visible as a very marked concentration of light in one part of the sky unless our current location had been its center at the time of its occurrence, and, since the Earth is only some thousands of miles across whereas the observable universe has a width of many trillions of miles, that last possibility is phenomenally unlikely to have been the case. (It would also have had Copernicus spinning in his grave.) Its closest resemblance was actually to an extremely rapid "expansion" or "inflation", as in the usual analogy to the expansion of a cooking pudding containing, as its raisins, either incipient local universes (-like our own, which is much larger than the part of it we can observe) or incipient clusters of galaxies. The main difference would've been that the cosmic expansion involved cooling rather than cooking.

The reheating that occurred, when quantum fluctuations or perturbations ended the expansion locally, produced that "hot dense soup of particulate energy" which provided the usual description of the Bang during the three decades between the failure of Hoyle's Steady State cosmology and the development of the inflationary cosmology that admits the possibility of numerous local universes, and it is that nearly exponential expansion which seems to have occurred during part of the time between the present day and an original Big Bang on a much smaller spatial scale that has rather confusingly pre-empted the term "inflation", just as the "space" popularized by sci-fi writers has interfered with use of the term "separation", which might've provided a much more specific one for the physical gaps between any entities with mass. However, such alternatives as the one developed by Hawking in his No Boundary Proposal, and elaborated in 2003 by Aguirre and Gratton, leave it unclear whether that earlier Big Bang even occurred.

 

[Ophiolite]

No, it is not. "Big Bang" was given as a dirisory term and is now just a name that has a specific meaning. "Explosion" also has a specific meaning and is NOT one that is appropriate as a name for what we call the "big bang".

This is a common misconception. I held it myself at one time. The myth is that Hoyle chose it to poke fun at the theory when promoting his own Steady State concepts.

Hoyle first used the term publicly in a BBC broadcast in the late 1940s. Some proponents of BBT, interpreted the term, as you suggest, as derisory. However, Hoyle maintained he had no such intention and was simply looking for an expression that would convey something of the nature of the event to a lay public.

 

[Rafael Munoz m]

Ok the radiation comes fron all arround because the universe is an hipersphere.
But
Why are we looking at that adiation as an old photo? That keeps Showing us the same face forever
That radiation emited photons, that are arriving to us today after a 14500000000 years aprox, but why do the photons keep arriving forever, it should be like an old movie that you can see it or loose it, after it is gone it is gone because the photons emited at that instant, reached us and kept going past us forever gone.
But we keep looking at the short wave radiation like if it kept glowing forever and we know that after it became a transparent universe it should have stped glowing

 

[Orodruin]

Ok the radiation comes fron all arround because the universe is an hipersphere.
But
Why are we looking at that adiation as an old photo? That keeps Showing us the same face forever
That radiation emited photons, that are arriving to us today after a 14500000000 years aprox, but why do the photons keep arriving forever, it should be like an old movie that you can see it or loose it, after it is gone it is gone because the photons emited at that instant, reached us and kept going past us forever gone.
But we keep looking at the short wave radiation like if it kept glowing forever and we know that after it became a transparent universe it should have stped glowing

You are right, the CMB is changing. Today, we are receiving CMB photons which were emitted closer to us than the ones we will receive tomorrow. However, the regions of relatively constant temperature were large enough to make this a very very slow change.

 

[Rafael Munoz m]

You are right, the CMB is changing. Today, we are receiving CMB photons which were emitted closer to us than the ones we will receive tomorrow. However, the regions of relatively constant temperature were large enough to make this a very very slow change.

Ok, the emission area was big and kept expanding, and that is the area covered by the short wave radiation that today cover the inside of the sphere we can see all around us, but I question about the thickness of that photon train reaching us.

It started at the big bang supposedly, then stopped after 300,000 years when the universe became transparent to energy and atoms formed, then the photon train should have been just 300,000 years long and a very small probability for us to catch that brief 300,000 year photon train after 14,500,000,000 years.

The only solution I see, is that the photon train´s end, is receding from us at light speed, fact that is confirmed by the fact that we don’t see the photon train go past us, it just keep getting cooler and longer wavelength.

That would mean we have a speed gradient with that photon train end, equal to light speed and that time, has stopped for us concerning that photon train, but then why at that particular time?

Another explanation I see, is that every space region that has a speed gradient with us equal to light speed, keep freezing its photons that go past us and showing us a photo face and not a movie, a photo face that just keep getting cooler and not going past us, in other words, a frozen photon train wave.

If we see those photos at 14,500,000,000 light years, it may mean that, that is the only distance we will forever see, because a photo never change, just gets cooler and cooler and its wavelength longer and longer until it is no longer detectable.

Then it would mean, that the universe is not that old, just that we cannot see past that distance, because at that distance, the space is growing at light speed between us.

Another inconsistency I see, is that, that 300,000 light year photon train, reaching us, keep going past us, because we are catching those photons and each end every one of those photons have energy, energy lost from the photon source; and that explain why we can see the source cooler and cooler. We are seeing a spring getting longer and longer and going past us without emitting more energy, just spreading over a longer distance or bigger space.

 

[Orodruin]

It started at the big bang supposedly, then stopped after 300,000 years when the universe became transparent to energy and atoms formed, then the photon train should have been just 300,000 years long and a very small probability for us to catch that brief 300,000 year photon train after 14,500,000,000 years.

No, you are missing the fact that this happened everywhere. And we cannot see the photons which were around more than 300000 years ago, they were quickly reabsorbed in the hot plasma. The background radiation which reaches us now was released when the Universe was about 300000 years old and the Universe became transparent. Because this happened everywhere, there are places which are so far away that the light from that time has not yet reached us. The CMB we see today are the photons which come from exactly so far away that it took them 13.4 billion years to reach us. Photons from places which were further away when the Universe was 300000 years old will form the CMB of tomorrow and that of 50 years from now.

 

[phinds]

@Rafael Munoz m you completely misunderstand the CMB. There IS no "photon train". We are seeing photons that were all emitted in a much shorter span of time than 380,000 years, but that happened 380,000 years after the singularity, in a process called the "Surface of Last Scattering". The photons that we see today were emitted from a region of the galaxy that was on the Surface of Last Scattering and is a distance away from us that make it such that the photons are reaching us not. In a billion years, we will be seeing photons what were emitted, ALSO from the same Surface of Last Scattering, but from positions that were enough farther away that their photons don't reach us for another billion years. This just goes on forever, although at some point the photons from the Surface of Last Scattering that we "see" are from a distance so large that the photons have been red shifted beyond detectable.

EDIT: I see orodruin beat me to it.

 

[bapowell]

Ok, the emission area was big and kept expanding, and that is the area covered by the short wave radiation that today cover the inside of the sphere we can see all around us, but I question about the thickness of that photon train reaching us.

It started at the big bang supposedly, then stopped after 300,000 years when the universe became transparent to energy and atoms formed, then the photon train should have been just 300,000 years long and a very small probability for us to catch that brief 300,000 year photon train after 14,500,000,000 years.

Rafael, see if this helps: https://www.physicsforums.com/insights/poor-mans-cmb-primer-part-0-orientation/. Read the "Orientation" paragraph.

 

[Rafael Munoz m]

Once atoms formed, light and matter stopped constantly interacting with one another, and photons were suddenly able to travel freely. As a result, the Universe became transparent.

One instant it was an opaque soup and the next one a transparent universe being filled with protons and neutrons.

That instant before it became transparent, we see as a surface emitting the background radiation or a surface of last scattering.

We refer to this epoch as the "Surface of Last Scattering;" light from this period is observed today as the CMB or background radiation or short wave background radiation, because it is reaching us now as shortwave radiation from all around us.

Since we cannot be outside our universe, we are inside and it is like if we were inside a sphere with us at the center; the same for every place in the universe so every place is the center and we are just one of those places that feel at the center of the universe.

That background radiation surface we see today is that surface of last scattering, non the less, that light arrive to us as a train of photons that should be just 380,000 (using your numbers) years long after the singularity and that mean, that after that, the 380,000 light yearlong photon train go past us (The duration of the epoch when the universe was opaque), then we should be seeing the singularity or the time when the excess matter in quarks came together in a specific combination of three quarks to make either a proton or a neutron. When the quarks that did not combine were annihilated. Thus, a little over one and a half minutes after the Big Bang, the time when all protons and neutrons had formed; or the time when the universe was hyper inflationary and growing faster than light.

We should be seeing anything after the 380,000 light yearlong photon train, but we keep seeing the same surface of last scattering forever and that mean, we will be receiving and absorbing photons forever, each one with energy and that mean infinite energy being carried away by those photons, photons that arrive to us from all around us forever and that mean, infinite energy that we know is impossible because it is an inconsistency.

That is what I am wondering as an inconsistency coming from the standard model believed true today.

 

[bapowell]

Once atoms formed, light and matter stopped constantly interacting with one another, and photons were suddenly able to travel freely. As a result, the Universe became transparent.

One instant it was an opaque soup and the next one a transparent universe being filled with protons and neutrons.

That instant before it became transparent, we see as a surface emitting the background radiation or a surface of last scattering.

We refer to this epoch as the "Surface of Last Scattering;" light from this period is observed today as the CMB or background radiation or short wave background radiation, because it is reaching us now as shortwave radiation from all around us.

Since we cannot be outside our universe, we are inside and it is like if we were inside a sphere with us at the center; the same for every place in the universe so every place is the center and we are just one of those places that feel at the center of the universe.

Yes.

That background radiation surface we see today is that surface of last scattering, non the less, that light arrive to us as a train of photons that should be just 380,000 (using your numbers) years long after the singularity and that mean, that after that, the 380,000 light yearlong photon train go past us (The duration of the epoch when the universe was opaque), then we should be seeing the singularity or the time when the excess matter in quarks came together in a specific combination of three quarks to make either a proton or a neutron. When the quarks that did not combine were annihilated. Thus, a little over one and a half minutes after the Big Bang, the time when all protons and neutrons had formed; or the time when the universe was hyper inflationary and growing faster than light.

We should be seeing anything after the 380,000 light yearlong photon train, but we keep seeing the same surface of last scattering forever and that mean, we will be receiving and absorbing photons forever, each one with energy and that mean infinite energy being carried away by those photons, photons that arrive to us from all around us forever and that mean, infinite energy that we know is impossible because it is an inconsistency.

That is what I am wondering as an inconsistency coming from the standard model believed true today.

It's not an inconsistency; as people have been trying to explain in this thread, you simply have a misunderstanding. Did you read the link I posted above? Did you read the other responses in this thread explaining why thinking that there should be a 380,000 ly long train of CMB photons is incorrect?

Suppose the universe is closed, like the surface of a sphere. Imagine the CMB photons being released after the balloon has inflated a bit. Will we ever stop seeing CMB photons?

 

[phinds]

That background radiation surface we see today is that surface of last scattering, non the less, that light arrive to us as a train of photons that should be just 380,000 (using your numbers) years long after the singularity
.

You have ignored what both orodruin and I told you. Continuing to repeat something that has been shown to you to be wrong is not going to make it right. Read our posts (18 & 19) again and see it you can make sense of them.

 

[slatts]

We should be seeing anything after the 380,000 light yearlong photon train, but we keep seeing the same surface of last scattering forever and that mean, we will be receiving and absorbing photons forever, each one with energy and that mean infinite energy being carried away by those photons, photons that arrive to us from all around us forever and that mean, infinite energy that we know is impossible because it is an inconsistency.

That is what I am wondering as an inconsistency coming from the standard model believed true today.

I don't think that either the orientation piece that Bapowell referred us to, or the standard model, currently require that anything should necessarily continue "forever": In fact, it's my understanding that a cosmological constant will, if our galaxy lasts long enough and if there is (as many physicists believe) such a constant, leave it inaccessible to photons coming from anywhere beyond its "local group" of galaxies (which are just a small part of our currently observable region of space, that is itself just a small part of a local universe that, under the inflationary cosmology that does seem to be an accepted part of the "standard model", is very unlikely to be the only local universe).

I've got to add that I've never seen any hint that the photons in the CMB won't always be around somewhere: They just might not be visible from here. (A lot of the local universes, however, might lack any perceptible difference from ours, just as it is here and now.)

 

[Jorrie]

I've got to add that I've never heard any hint that the photons in the CMB won't always be around somewhere--they just might not be visible from here. (A lot of the local universes, however, might lack any perceptible difference from ours, just as it is here and now.)

With our current knowledge, the CMB will eventually redshift to very, very long wavelengths, but it should always be around.

BTW, if the cosmological constant does not change, I think it's our galaxy (maybe even the Virgo cluster) that will eventually be all that we can observe - these structures are gravitationally bound and do not expand with the universe.

 

[Mantuano]

No, it is not. "Big Bang" was given as a dirisory term and is now just a name that has a specific meaning. "Explosion" also has a specific meaning and is NOT one that is appropriate as a name for what we call the "big bang".

Well, then i'll wait until a cleaner word is proposed for what has derisorily been called Big Bang to give a better explanation to the omnidirectionlity of CMB, being inside the cosmos where this has supposedly happened.

 

[phinds]

Well, then i'll wait until a cleaner word is proposed for what has derisorily been called Big Bang to give a better explanation to the omnidirectionlity of CMB, being inside the cosmos where this has supposedly happened.

The omni-directionality of the CMB is already part of the big bang model and requires no further explanation, as you will see if you read up on it.

 

[Rafael Munoz m]

The CMB is a wall we can not see past it, and it is going away from us at light speed.
We estimate that the universe is 14,500 million years old because we can't see objects older tham that.
But we know that galaxies and stars needed more time to allow for what we actually see, and we invented inflation, an era that suposedly allowed everything to move faster than light, violating the GR rule that nothing can move faster than light.
We are violating the laws we have, a law that we can not see an exception anywhere in the visible universe.
What I am postulating is that instead of believing that during an inflationary era some parts or all the parts of the universe moved faster than light, the opaque era may be longer, but we can not see exactly when the universe started because of the CBM light wall that surround us.

 

[Rafael Munoz m]

Concerning that the CBM is part of the standard universe model need no more explanation, I think that we need to rethink every part of the standard model, because it is not explaining many data we are aquiring wirh the new isnstruments.
Accepting the standard models would condemn us to not accepting GR by not question the then standard model.
That is how science advance, by questioning everythin all the time, even when we have to start iver again and again

 

[phinds]

The CMB is a wall we can not see past it, and it is going away from us at light speed.
We estimate that the universe is 14,500 million years old because we can't see objects older tham that.
But we know that galaxies and stars needed more time to allow for what we actually see, and we invented inflation, an era that suposedly allowed everything to move faster than light, violating the GR rule that nothing can move faster than light.
We are violating the laws we have, a law that we can not see an exception anywhere in the visible universe.
What I am postulating is that instead of believing that during an inflationary era some parts or all the parts of the universe moved faster than light, the opaque era may be longer, but we can not see exactly when the universe started because of the CBM light wall that surround us.

You misunderstand metric expansion. Things receding from each other is not proper motion. Nothing ever moves, or has moved, faster than light.

 

[phinds]

Concerning that the CBM is part of the standard universe model need no more explanation, I think that we need to rethink every part of the standard model, because it is not explaining many data we are aquiring wirh the new isnstruments.
Accepting the standard models would condemn us to not accepting GR by not question the then standard model.
That is how science advance, by questioning everythin all the time, even when we have to start iver again and again

There is nothing wrong with the Standard Model, just with your understanding of it. If you think there are experiments that show a violation, please be very specific and say what they are.

 

[bapowell]

we invented inflation, an era that suposedly allowed everything to move faster than light, violating the GR rule that nothing can move faster than light.

This is false. Things did not move "faster than light" during inflation any more than they do during decelerated expansion. If this statement confuses you, do some reading about the metric expansion of space, or have a look here: https://www.physicsforums.com/insights/inflationary-misconceptions-basics-cosmological-horizons/. Before discarding an idea, I urge you to learn more about it.

 

[Rafael Munoz m]

Bapowell
Thank you, it certainly made things clear

 

[nikkkom]

Once atoms formed, light and matter stopped constantly interacting with one another, and photons were suddenly able to travel freely. As a result, the Universe became transparent.

One instant it was an opaque soup and the next one a transparent universe being filled with protons and neutrons.

That instant before it became transparent, we see as a surface emitting the background radiation or a surface of last scattering.

Wrong. Hot ionized hydrogen gas did not *instantly* became neutral. It happened gradually, over some 100 000 years.

We refer to this epoch as the "Surface of Last Scattering;" light from this period is observed today as the CMB or background radiation or short wave background radiation, because it is reaching us now as shortwave radiation from all around us.

Since we cannot be outside our universe, we are inside and it is like if we were inside a sphere with us at the center; the same for every place in the universe so every place is the center and we are just one of those places that feel at the center of the universe.

That background radiation surface we see today is that surface of last scattering

Sort of. I see it this way. At 400 000 years since BB, I'd still see nothing but a uniform red glow (~3000K) coming from everywhere. But at 500 000, I'd start noticing that it looks like I'm at a center of a transparent bubble, which has the opaque glowing red walls, approximately 100 000 light years away from me. Still almost the came color temperature.

This apparent "bubble" would grow with time. After a few millions of years, the grow would become noticeably redder, eventually shifting into infrared. It's not because "walls" are colder - it's because they are moving away - the gas in them is not stationary in respect to us, it's moving away. Doppler red shift.

The "walls" of this bubble are exactly the regions which were ~300000 years old and which experienced hydrogen recombination, emitting this red glow in the process. They are not paper-thin - they are about 100 000 light years thick.

By now, the walls are (apparently) 13.7 billion light-years away from us.