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originally posted by: pfishy
Your explanation makes perfect sense. Though I think I may have misstated my question slightly. It isn't necessarily red shift that I'm referring to, but the overall lengthening of the waveform from what it was originally to what it is now due to expansion. I know this is also a description of red shift, but since the CMB is universally pervasive, it isn't trying to measure distance. Merely the physical alteration of a given wavelength due to spacetime expanding the medium through which it's traveling. Though you did clarify that my assumption of the CMB originating an high frequency gamma isn't likely correct, so it's likely a moot point.

You're asking great questions. This is another good one, and actually the early cosmologists didn't quite get this distinction between doppler shift and cosmological redshift quite right, as they thought the redshift was Doppler redshift in the early days. We now know to a fairly high confidence that the cosmological redshift isn't due to Doppler redshift, but rather it's due to pretty much what you said: "the overall lengthening of the waveform from what it was originally to what it is now due to expansion".

Modern cosmologists however do know the difference so any scientific cosmology sources you read this millenium will explain that correctly. The other thing that modern cosmologists know is that the "naive Hubble" formula for redshift doesn't work well at high redshift, but it worked fine 80 years ago because they couldn't see anything far enough away to contradict the simple correlation.

But yes at 3000K a blackbody produces very few gamma rays. Even our sun at nearly twice that doesn't produce many gamma rays, well that's not strictly true. It makes gamma rays in the core where the fusion takes place, but they almost never make it out of the sun, so what the sun actually emits includes very few gamma rays. So 380,000 years after the big bang when stars were forming the same thing was going on with the new stars back then: gamma rays were produced in stellar processes, but they mostly don't escape the stars (a few do, more from higher temperature stars, again mostly fitting the blackbody profile of frequency distribution though not exactly):

Solar core

In the process of heat transfer from core to photosphere, each gamma ray in the Sun's core is converted during scattering into several million visible light photons before escaping into space.

So, that's what happened to most of the gamma rays produced in stars then and now.

Speaking of the energy the sun emits, here's an interesting question:

Which emits more power per unit volume, your body, or the sun? (as measured in say, watts per cubic meter or use whatever units you like)

originally posted by: bottleslingguy
What's wrong with this idea? www.youtube.com...

A lot. The one thing that looks interesting are the pictures he shows of the sunspots that do make it look like the sun might be hollow inside, but images can be deceiving and this reminds me of Don Scott's claim that he's seen electrical processes carve out things that look like the grand canyon so maybe the grand canyon was carved out by electrical processes.

This whole idea that something "looks like" something else may sound intuitively pleasing but there is a lot more corroboration required to establish such claims.

There's too much wrong with the video to explain everything wrong with it, but I'll pick a few key points.

First, his claim that the "eardrum" senses both sound and gravity is false. It really doesn't sense either, but it's related to sound. The inner ear has the vestibular system that relates to gravity (balance), which has a different function from from the cochlea which is related to hearing. The fact that they are in proximity doesn't mean much. The fact you breathe and eat through your mouth doesn't mean your stomach and lungs are closely related. If you want to go down that path you can try to answer Neil Tyson's question about why the human body has an entertainment complex in the middle of a sewer system, referring to things like urine and sperm excreting through the same opening. Sharing an "address" doesn't mean they're related.

Second, in a way he debunks his own claim but I don't think he understands enough physics to realize it. He talks about a vortex having low pressure at the center which is correct and shows a coffee cup with a vortex in it. But what he doesn't explain is the fluid dynamics that creates this low pressure, where the faster speed of the fluid creates lower pressure. Then he talks about how the angular momentum of the sun is so low, rotating once every 30 days, but this discussion debunks his claim about the sun being anything like a low pressure vortex at the center of a coffee cup where the fluid moves quickly, because by his own admission the sun is rotating very slowly.

What he would need to do to support his idea is to show that a vacuum exerts gravitational influence, but what the evidence actually shows is that not only does the vacuum not exert gravitational attraction as he claims, it apparently does the opposite to some extent, as we think it exerts some kind of repulsion, which is what we refer to as "dark energy" that was discovered in 1998. The repulsion is so small per unit volume that we've only measured it on cosmological scales. However the volume of the universe is so vast that even this very small effect of the vacuum ends up being credited as having most of the mass-energy content of the entire universe.

So in summary the only evidence related to his claim about a vacuum I'm aware of (dark energy measurements) says that a vacuum does the opposite of what he claims, and will have more tendency to push things apart (via the metric expansion of space), instead of pulling things together.

originally posted by: Arbitrageur

originally posted by: darkorange
"Wind resistance'" that is what I am asking about. is there a resistance to cosmos from what it expands into?

Referring to my previous answer about what the universe is expanding into, if the universe is infinite it's not expanding into anything. If it's finite there could be a boundary of some sort but the question can't be answered scientifically because we've never observed any such boundary and therefore can't say anything about it. If the inside of our universe has space-time and outside our universe, there's a lack of space-time or anything else, it may provide no resistance at all. You could guess any properties you want for what's beyond our universe if there is such a thing, but if there's no way to ever make observations to confirm or reject any of the guesses, then the guesses aren't meaningful, or as Ned Wright put it in his cosmology faq, it's not a profitable thing to think about.

If ther is then entropy would find escapades punching black holes to bleed excess energy/pressure? No?

I'm not sure what you mean by this, but if I understand your question correctly, this isn't like accelerating a particle THROUGH space, where it might start bleeding off some of the additional energy it attains in other forms such as EM radiation. The reason the metric expansion of space is different is it's not moving THROUGH space, the space itself is stretching.

Just as we discovered dark energy in 1998, the door is open to learn more about about the profile of accelerating expansion over time, which I'm sure we will. More accurate measurements are still being made and we'll have to see what adjustments to our models will best fit the observed data, so I wouldn't completely rule out the possibility of finding something more complex going on.

yes and no.
I was thinking that something like black holes may occur when excess energy works into creating punctures when elastic medium cannot accommodate pressure demands in volume. Like a balloon blown too fast or reaching it's stretch limit, air will ultimately rip it. Entropy, how I understand it, has no means to reach equilibrium punching escape routes out. Too bad my vocabulary sucks and English is pretty rich to deliver the point said, given masterfully used.
In any event, probably first BHs were formed during A.Guth version of BB because of this very reason.
As to what it is expanding into...hmm..you cannot say it is expanding into nothing. I think there is a resistance of what it is expanding into because of the very nature of BHs.

One day universe will enter contraction phase (if not already so). If there was no resistance then it would face cold death, which, in it's turn, suggest universe is one time event. Do you think it is?

thanks


D0.

Can sound travel through dark matter?

Can sound bend light ; experiment link

originally posted by: darkorange
One day universe will enter contraction phase (if not already so). If there was no resistance then it would face cold death, which, in it's turn, suggest universe is one time event. Do you think it is?

Prior to 1998 cosmologists were asking questions about the rate of the universe expansion and if the expansion would eventually stop, then move into a contraction phase. So, before 1998, it was an open question. I think the data they collected just before 1998 was trying to answer that, but analysis of the data blew their minds when it showed the expansion was accelerating.

At first even the researchers who did the study didn't want to believe it and there was skepticism in the community that wanted to see confirmation. Then there was confirmation and eventually most cosmologists believe the accelerating expansion is real. Lately someone said those calculations need some tweaking based on new data, but they haven't published the revised calculations or new data yet, but I got the impression it will just show the rate of acceleration may be slightly different. That still won't allow for a contraction phase.

So before 1998 nearly all cosmologists seemed to think a future contraction phase might be a possibility. Since about 2005 I don't know of a single one who thinks that anymore. Other than the "tweaking" of the analysis of dark energy I just mentioned I don't see the data being refuted enough to suggest a contraction might happen. I suppose we could always make a new discovery that will change our opinion again, but for now, contraction seems inconsistent with observations that not only is the universe expanding, the expansion is accelerating.

originally posted by: yulka
Can sound travel through dark matter?

That depends on how you define dark matter. If you include baryonic dark matter like the stuff the Earth is made of, yes of course it can travel through baryonic dark matter. But if you refer to the most popular dark matter candidate for the undiscovered particles known as "WIMPs" or "weakly interacting massive particles", sound as we ordinarily think of it probably can't travel through those as they seem to not interact with ordinary matter, and ordinary matter must interact with itself to transmit sound.

a reply to: Arbitrageur

We can see the baryonic but not the popular dark matter?

originally posted by: yulka
a reply to: Arbitrageur

We can see the baryonic but not the popular dark matter?

We can see the Earth because we're standing on it, but distant planets are "dark" meaning they emit too little radiation to detect from a great distance, so other planets in other solar systems are a type of dark matter. So are a type of dim star called "brown dwarf", where we can only see them within so many light years of Earth and not beyond that. We can only guess at how much stuff is in the Oort cloud in our own solar system, because even that matter is dark and too dimly radiating to detect with current technology.

Even though we can't see all that other baryonic matter, we don't think there can be enough of it to explain the gravitational effects we observe, which is why we invented the idea of "WIMPs" as a possible explanation. But Baryonic dark matter certainly accounts for some dark matter even if not all of it:

Baryonic dark matter

In astronomy and cosmology, baryonic dark matter is dark matter (matter that is undetectable by its emitted radiation, but whose presence can be inferred from gravitational effects on visible matter) composed of baryons, i.e. protons and neutrons and combinations of these, such as non-emitting ordinary atoms. Candidates for baryonic dark matter include non-luminous gas, Massive Astrophysical Compact Halo Objects (MACHOs: condensed objects such as black holes, neutron stars, white dwarfs, very faint stars, or non-luminous objects like planets), and brown dwarfs.

The total amount of baryonic dark matter can be inferred from Big Bang nucleosynthesis, and observations of the cosmic microwave background. Both indicate that the amount of baryonic dark matter is much smaller than the total amount of dark matter.

a reply to: Arbitrageur

If its baryonic condensed matter in a black hole, and it bends light. Can gravity bend light? A super magnet?

a reply to: Arbitrageur

Specifically per unit of volume? Well, I suppose that you are referring to an average energy output for the sun, as different regions output more than others (i.e. core vs surface vs photosphere).
And since you brought it up in the manner that you did, I'm going to say the human body, though it seems very counterintuitive.

a reply to: yulka

Can gravity bend light?

Yes. Well, not really, but sort of.

Gravity cannot bend light but it can bend space. From the outside it appears that the path light follows is bent. From the point of view of light, it's traveling in a straight line.

a reply to: Phage

Doesnt a black hole bend light? Or suuuuck it in?

a reply to: yulka
Yes. Well, not really, but sort of.

Gravity cannot bend light but it can bend space. From the outside it appears that the path light follows is bent. From the point of view of light, it's traveling in a straight line.

In the case of a black hole, space is bent a lot. Really, really a lot.

originally posted by: Phage
a reply to: yulka
In the case of a black hole, space is bent a lot. Really, really a lot.

So it isnt gravity? It distorts space?

Time = Gravity?

a reply to: yulka

Gravity, as described by general relativity, is the distortion of spacetime caused by matter.

Gravity is the distortion of space. They are the same thing.

a reply to: yulka
Edit: Phage is correct. Gravity bends spacetime, which the light travels through. My following statement is an oversimplification.

Gravity can indeed bend light. Astronomers use this effect (called gravitational lensing) to study galaxy and galaxy clusters that would normally be obscured by massive foreground objects such as other galaxy clusters. The effect is a highly distorted image of the distant object or sometimes even multiple images.

Here's a good article about it.
Einstein cross

a reply to: Phage

Our earth core distorts space?

a reply to: yulka

Our earth core distorts space?

The whole Earth does. That's why we can stand on it.

You distort space. A little. A very, very little.

a reply to: Phage

According to Newtonian Physics, you are correct...

However

Fairly recent tests have supported Einstein's theories in that gravity in fact does effect light.. (Bend)

For all practical purposes though, Newton's laws work in the real world of practical physics..

a reply to: pfishy

Isnt this just distance and they are using galaxies as magnyfying glasses?

a reply to: semperfortis

Newtonian physics has nothing to do with what I said. It's all about general relativity.
Mass bends space. Light travels in a straight line through space. Bent space means that light appears to bend from an outside frame of reference.