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Physics, Astronomy & Cosmology / Re: Is it possible for the laws of physics to change in time?

« on: 25/10/2019 23:58:22 »

It seems pretty unlikely that laws of physics don't change over time, Entropy would see to that.

Entropy doesn't affect the laws of physics because it is a by-product of the laws of physics. The second law of thermodynamics, in particular.

I mean, honestly, how can chaos be lawful? You either have a descent into chaos or you dont.

Depends on how you define "chaos" and "lawful". The way in which chaos is defined in terms of entropy requires no change in the laws of physics over time.

What's so special about stupid old energy  that only it should suffer entropy, why shouldn't laws be affected too?

Because entropy is defined in terms of energy specifically.

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Physics, Astronomy & Cosmology / Re: What is the cosmic microwave background?

« on: 15/10/2019 01:38:04 »

Well, I just don't understand it... If it is infinite then why all the to-do and palava about "We've calculated the mass of the entire universe and it's been found wanting, and in need of a shed-load more mass, which just happens to be invisible" (Dark Matter). It's this statement that inspired me to question what CMBR actually is and why somebody thought it suggested there wasn't enough of it (mass that is).

Is dark-matter another myth that's been blown out of proportion?

We have looked at the observable universe how it behaves.  It behaves as if it contains a lot more mass than the mass we can see or detect via the electromagnetic spectrum.  So we have calculated the mass of the entire "observable universe", and found that visible mass only makes up a part of it.
On smaller scales, we look at galaxies. We can measure how fast the stars in them orbit.  But if we calculate how fast they they should orbit based on the matter we can see, they are orbiting too fast.  Not only that, but the way their orbital speeds change as you move out from the center of the galaxy isn't consistent with the way the matter we see is distributed. So for example with a typical spiral galaxy, instead of behaving like the matter is constrained to the visible disk shape, they behave as if the majority of the matter is spread out in a sphere which extends above and below the disk of the galaxy.
There are two possible explanations for this: Either there is something with mass there that we can't see, or our understanding of gravity is wrong.   Both possibilities have been examined and considered. But as more and more data comes in, the dark matter keeps gaining evidence and the other model loses it. For example, we've recently found some galaxies that behave as if they have little to no dark matter.  Now while is is perfectly reasonable for this to occur in the dark matter model, it is less reasonable that gravity itself behave differently in these galaxies then other.  If the rules governing gravity are different than those we think they are, they would still need to be consistent from galaxy to galaxy.
And It's not as if we don't already know of particles that behave similar to the way dark matter would. The neutrino is a massive particle, with gravity, which does not interact via the electromagnetic interaction. It is effectively invisible.  It is a WIMP (Weakly Interacting Massive Particle)*, which is one of the possible candidates for dark matter, In fact, one hypothesized type of neutrino( the Sterile Neutrino) has been suggested as a suspect.

*The other candidate is MACHOs or MAssive Compact Halo Objects

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Physics, Astronomy & Cosmology / Re: Is light an independent entity, or is it an effect of a larger mechanism ?

« on: 14/10/2019 18:13:16 »

Is this a good time to ask about something I came across recently in a popular science video somewhere....

Concerning a particular type of particle which, when its 'state' was changed then a matching particle's state also changed - instantaneously, no matter how widely seperated in distance (thus appearing to break the lightspeed limit).

Sorry I forget the details and the video, because I didn't pay too much attention to it. But just wondering if this rings any bells here?

Like as already been alluded to such "quantum entanglement" can't be used to send actual information faster than c (speed of light in a vacuum.)  Using the glove example.  In QM, until you open an envelope, not only do you not know whether it contains a LH or RH glove, but neither does the "glove" know* which it is. It is in some undetermined state.  When you open your envelope and your glove "decides" what it is, the other entangled glove "decides" its the other.
The problem is that when you open your envelope to ans see a LH glove, you don't know if that is because you opened the envelope and set off the decision making process, or if someone else had already opened the other envelope, and that event decided what glove you would see. It would take some slower than light communication between you and where the other envelope is to determine this.  The same goes with the changing of state (turning the glove inside out).  You don't know if the inside-out glove was the original unchanged state or the "changed" state without communicating with the other end by some slower than light means.

* This is not to say that you could actually do this with an actual pair of gloves, the glove here is just stand-in for a subatomic particle. One of the reasons quantum behavior seems so strange to us is that by the time you get to the macroscopic scales these effects "average out" to being immeasurable, and how objects appear to behave at this scale is what we accept as "natural".

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Physics, Astronomy & Cosmology / Re: Is light an independent entity, or is it an effect of a larger mechanism ?

« on: 14/10/2019 10:32:25 »

The analogy breaks down (as do all classical analogies of quantum phenomena, eventually) if you alter the state of your glove, say by turning it inside out. According to QM, and indeed demonstrably, the other glove alters its state too, and in a shorter time than it would take for a photon to travel between them.

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Physics, Astronomy & Cosmology / Re: Is light an independent entity, or is it an effect of a larger mechanism ?

« on: 14/10/2019 10:11:54 »

Concerning a particular type of particle which, when its 'state' was changed then a matching particle's state also changed - instantaneously, no matter how widely seperated in distance (thus appearing to break the lightspeed limit).

You are hearing about entangled particles. Difficult to describe in detail, but it has to do with correlation and quantum statistics and also what we know about the particles.
An analogy: lets say a friend puts a rh glove in one envelope and a lh glove in another but doesn’t tell you which is which. We could say the contents of those envelopes are entangled and there is a correlation between the ‘state’ of the gloves in each envelope.
So, you now send one envelope to another person on other side of the world and keep one. If you open your envelope (measure the state of your glove), you instantly know the state of the other glove, but nothing has changed other than your knowledge. We can do the same with particles eg electrons or photons and when we measure the state of one we can be sure of the state of the other.
However, quantum statistics are more complicated than everyday statistics so this is a fascinating area of misunderstanding, and you will need some maths to understand what is happening.

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Physics, Astronomy & Cosmology / Re: What is the cosmic microwave background?

« on: 12/10/2019 23:38:20 »

why don't we see other radiation that must have been emitted before [and after] this 3000k period?

We don't see light emitted before this period because the plasma was opaque before this era.
- In a plasma (before this era), electrons are not attached to atoms, and so they can have every possible energy
- As electrons approach positive nuclei (or negative electrons), they are accelerated/decelerated by the electric field
- This produces "Braking Radiation" (with the German name "Bremsstrahlung") which can absorb and produce light of every possible energy level - but in thermal equilibrium, it will have a distinctive spectrum
https://en.wikipedia.org/wiki/Bremsstrahlung

In atoms (after this era), electrons can have specific energy levels, and thus produce a line spectrum
- Cosmology suggests that there was an even later phase (150 million to 1 billion years after the Big Bang), where hydrogen fusion started in early stars, which produced lots of UV light, causing hydrogen & helium to again become a plasma
- With larger telescopes, we are now able to see quasars that were active towards the end of this period in the early universe
- These have high red-shift (z=6 to 20), but not nearly as much as the big-bang radiation (z=1089)
- They do have many atoms beyond hydrogen and helium, since nuclear fusion produced them, and supernovas spread them into space
- Astronomers are hoping that the James Webb Space telescope will be able to see a lot more of these infra-red =high red-shift quasars which were active earlier in this reionization phase (if and when it is successfully launched & commissioned)
- But the universe was much less dense during the reionization phase than in the pre-3000K era, so we can still see the CMB at microwave frequencies through the infra-red haze of radiation from this later phase (and the visible-light of today's stars and galaxies).

See: https://en.wikipedia.org/wiki/Reionization

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Physics, Astronomy & Cosmology / Re: What is the cosmic microwave background?

« on: 12/10/2019 09:18:31 »

The conversation seems to imply the CMB generation was quite a short phase (when the universe was a 3000k plasma). If its effects are still saturating the universe after 13.7bn years (due to its photons filling cubic meters of space as fast as they leave it), then the volume of this plasma must have been.... 'large'. But, why dont we see other radiation that must have been emitted before and after this 3000k period?

To add to what @Halc said, I’m giving a very simplified analogy.
Think about a light bulb, lots of very bright light. Switch it off and you will see the light fade quickly and the filament still glow red for a while. Now touch the glass, still very hot, move the bulb 100m away and a thermal imaging camera will still pick up that heat (infrared) radiation.
Now imagine a universe filled with light bulbs (lets ignore for the moment the inflation that put them there) if they are all switched off together they begin to cool, but still radiating. When the ones next to us have cooled, all of them will have cooled, but the radiation reaching us from the ones billions of light years away was emitted when they were still quite hot - less hot than IR and was down to microwave frequencies.

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Physics, Astronomy & Cosmology / Re: What is the cosmic microwave background?

« on: 12/10/2019 01:45:24 »

The conversation seems to imply the CMB generation was quite a short phase (when the universe was a 3000k plasma). If its effects are still saturating the universe after 13.7bn years (due to its photons filling cubic meters of space as fast as they leave it), then the volume of this plasma must have been.... 'large'. But, why dont we see other radiation that must have been emitted before and after this 3000k period?

There was light before then, but the universe was opaque, so the light never got far before hitting something.
There is light since then.  That's all the stars and whatnot, most of them brighter than the CMB.

Why isn't this still filling up cubic meters of space as fast as they leave it like the cmb? Or is this the dark matter that ppl are still looking for?

It does fill space as fast as it leaves it, else the stars would not shine continuously.  There's nowhere you can be (except in places like clouds that obstruct light) where galaxies cannot be seen, so their light fills all space, same as the CMB.

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Physics, Astronomy & Cosmology / Re: What is the cosmic microwave background?

« on: 12/10/2019 00:12:14 »

oxyacetylene gas torch

This also has several things that didn't appear in the Big Bang, like the OH, CH, C₂ and C₃ species.

Which makes things worse.
With no molecular species, only atomic transitions were available.
Neither hydrogen nor helium can give a black body spectrum at 3000K except under pressure.

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Physics, Astronomy & Cosmology / Re: What is the cosmic microwave background?

« on: 09/10/2019 15:33:19 »

I would not rely on any estimate of cosmos(or even galactic) mass.  All stars spew out isolated free charge continuously.  Think about that......think how long they have been doing that.   We can find no evidence of charge recombination from our sun.  The charge from our sun is still accelerating out past Neptune.  If that charge recombined, we would detect the emission.  Think about all the charge from the sun for eons.  And eons of stars.  There could be a good chance that most of the mass(isolated charge) in the universe, is not under gravitational influence.

And a good chance that there could be much, much more mass than thought.   Naked mass might be different than gravitational mass.

How about this, we believe that high velocity makes it difficult for recombination.  What if a simple pole flip on a particle made a difference?  What if there are certain velocity and density conditions where a high velocity recombination readily occurs with an unknown emission spectrum..........such as CMB.  CMB might be fresh.  A cold spectrum.

Astronomy is an unique science.  When we photograph motion on earth, all the objects are in present time. One time stamp. But a star field is not an image of objects........it's an image of time stamps, with unknown AND different times.  This is unique. We are foreign to this dynamic.  On earth, we have never had need of this way of thinking and understanding.  That does not include recognizing star field patterns with season.  That reasoning when to the gods.

We can not see the present universe or even our present galaxy. The present universe might be dark and scattered.

It's hard to fathom that our galaxy's center could have super nova-ed thousands of years ago.

Compare the number of assumptions that astronomy uses with the number of assumptions that chemistry uses.   Astronomy needs salt to swallow.

Not that there is anything wrong with astronomy.  Like I said, it's unique. A different kind of puzzle.

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Physics, Astronomy & Cosmology / Re: What is the cosmic microwave background?

« on: 09/10/2019 10:38:09 »

what has generated (or is generating) the CMB?

As Kryptid said, the CMBR photons last interacted with matter when the universe had a temperature around 3000K.
- A plasma at 3000K will continually absorb and reemit light with a characteristic "black body spectrum"

At that time, the universe was mostly hydrogen, some helium, and almost nothing else.
- When the temperature drops below 3000K, hydrogen and helium can capture and hold onto electrons, so emission of the black body radiation effectively stops, and emission becomes a "line spectrum".
- Hydrogen and Helium bind their electrons tightly, so it takes very energetic photons (Ultraviolet) to excite them and allow emission of a line spectrum.
- By the time the universe dropped below 3000K, there was very little ultraviolet around, so space became transparent to this 3000K black-body radiation.

The subsequent expansion of the universe by a factor of over 1000 has dropped the effective temperature of the black body radiation from 3000K to 2.7K.
- Since we are still within the "fireball", we are being continually bombarded by this black body radiation from all directions (but severely red-shifted).

See: https://en.wikipedia.org/wiki/Cosmic_microwave_background#Relationship_to_the_Big_Bang

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Physics, Astronomy & Cosmology / Re: What is the cosmic microwave background?

« on: 08/10/2019 17:28:34 »

And just to add to What Kryptid already said. While the photons we detect today are different ones than the ones we detected yesterday or will detect tomorrow. The one we detected yesterday where a bit "younger" and and the one we will detect tomorrow will be a bit "older".   In other words, the CMB is still decreasing in temp as the universe continues to expand.  The decrease is very small, so it would take a long time before it became enough to be discernible by our measurement standards, but it exists.


 

So the radiation we saw last week must now be gone forever. It sounds like this radiation must have been tavelling past us and 'disappearing forever' for the last umpteen billion years. why is it STIIL travelling past us in a way that we can register with instruments?

This is like saying that because the average water molecule speed is something is in the 100's of meters per second, that a fish in a lake should not detect any water around him because the water molecules that he felt yesterday has traveled off to some other part of the Lake. New water molecules have replaced them.*

*Now it is true that with the lake being a confined body of fixed size, he can encounter the same water molecule more than once.  This is note completely inconceivable for the universe if it were of a finite fixed size.  a Photon could pass the Earth, "circumnavigate" the universe and pass it again. How long it takes between passes would depend on the size of the universe. ( in a really small "closed" universe you could conceivably look off into the distance with a telescope and see the back of your own head)
 But with an expanding universe, even if it is finite, the size and rate of expansion could be such that the "circumference" grows faster than light can traverse it, and light passing you at any given moment can never return. ( but this still doesn't mean that it won't be replaced by a different photon.)

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Physics, Astronomy & Cosmology / Re: What is the cosmic microwave background?

« on: 08/10/2019 16:50:24 »

The fact that we're 'seeing' this radiation is proof that it's moving through space, right? It isn't just loitering around in our vicinity with nothing better to do. So the radiation we saw last week must now be gone forever. It sounds like this radiation must have been tavelling past us and 'disappearing forever' for the last umpteen billion years. why is it STIIL travelling past us in a way that we can register with instruments?

It's true that the radiation is constantly on the move. However, that radiation is travelling in all directions at very nearly the same rate. As many photons of this radiation are entering any given cubic meter of space as are leaving it. So there is always radiation present to measure.

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Physics, Astronomy & Cosmology / Re: What is the cosmic microwave background?

« on: 08/10/2019 16:40:02 »

Modern theory believes that mass and motion can change time.

They also believe that a change in clock tic rate, or a change in frequency is proof of a change in time.

This allows time to vary with motion.  They believe this is the only way to explain light velocity measurements.

Any theory or explanation of CMB must have these underpinnings.

So, if you capture a CMB wave, it would appear very old to us, but for the wave, it thinks it's only milliseconds old.

See what you can do with science?

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Physics, Astronomy & Cosmology / Re: What is the cosmic microwave background?

« on: 08/10/2019 16:02:23 »

The problem is that you are thinking of the Big Bang as an explosion in space, rather than the expansion of space.
With an explosion in space, the Photons could have raced past the matter into the space beyond. But with the Big Bang, there is no "space beyond" for the photon to expand into. We are at the "forefront" of this expansion.
An analogy would be that the universe is like the skin of an expanding soap bubble. Everything in it, photons, matter, etc. is confined to the skin. When the bubble is small everything is much more crowded together and as it expands, Things on a whole move apart and it is less crowded.  With photons, when it is small their frequencies are high ( the universe is "hot"), but as the bubble expands, they are stretched out to longer wavelengths and lower frequencies ( the universe "cools"). The CMB are those early photons that have been stretched out, but still confined to the same "Bubble skin" as everything else.