Thread: Dumb Questions (again)

Hawking says that the universe expanded by a factor greater than the speed of light in the first billionth of a billionth of a billionth of a second(probably missed a few billionths).

Is this expansion speed analogous to the speed of curled up dimensions opening up? If a curled up dimension suddenly opened up would the effect be universally instantaneous?

Again, I'm no physicist and I probably have misunderstood something along the way (very common) and if so then could somebody please straighten me out.

Originally Posted by zinjanthropos

Hawking says that the universe expanded by a factor greater than the speed of light in the first billionth of a billionth of a billionth of a second(probably missed a few billionths).

Is this expansion speed analogous to the speed of curled up dimensions opening up? If a curled up dimension suddenly opened up would the effect be universally instantaneous?

1. It is not analogous.

2. Nobody even knows if compactified spatial dimensions are real. If there were more "large" spatial dimensions things would be very different, and if the number were even Huygens principle would cease to hold making electromagnetics (including light) a whole new ball game.

Originally Posted by zinjanthropos

Hawking says that the universe expanded by a factor greater than the speed of light in the first billionth of a billionth of a billionth of a second(probably missed a few billionths).

That is called inflation. The term was made up to explain why the universe is smooth (it isn't) which was rather unnecessary since without biases, the BB would have been smooth anyway as in if you toss a coin up a billion times, you'll get virtually 50% heads and 50% tails as anomalies disappear over such scales.

Is this expansion speed analogous to the speed of curled up dimensions opening up? If a curled up dimension suddenly opened up would the effect be universally instantaneous?

The speed of light is a set figure and this would not get around it. But if you could imagine a balloon with dots on it being blown up, then though no two dots separate from each other at light speed, it is possible to bypass that speed. If you have a line of ten dots separating at half light speed, then the distance between the first and the last is separating at five times light speed (as in ten times half light speed).

Again, I'm no physicist and I probably have misunderstood something along the way (very common) and if so then could somebody please straighten me out.

You learn by asking questions.

Originally Posted by Cyberia

Originally Posted by zinjanthropos

Hawking says that the universe expanded by a factor greater than the speed of light in the first billionth of a billionth of a billionth of a second(probably missed a few billionths).

That is called inflation. The term was made up to explain why the universe is smooth (it isn't) which was rather unnecessary since without biases, the BB would have been smooth anyway as in if you toss a coin up a billion times, you'll get virtually 50% heads and 50% tails as anomalies disappear over such scales.

wrong

In fact inflation explains why the universe is smooth on the largest scales, which it is, but lumpy on smaller scales.

Inflation is not due to Hawking, but originally to Guth and since modified and refined by others, notably Linde. Guth's popularization, The Inflationary Universe is not bad -- go read it.

Is this expansion speed analogous to the speed of curled up dimensions opening up? If a curled up dimension suddenly opened up would the effect be universally instantaneous?

Originally Posted by Cyberia

The speed of light is a set figure and this would not get around it. But if you could imagine a balloon with dots on it being blown up, then though no two dots separate from each other at light speed, it is possible to bypass that speed. If you have a line of ten dots separating at half light speed, then the distance between the first and the last is separating at five times light speed (as in ten times half light speed).

A garbled analogy, taken from some popularization and distorted.

The speed of light is a local thing and nothing travels faster than light locally. But expansion of space itself is not subject to any limit and as space expands it is possible for the distance between points to increase rapidly enough for points to recede from one another superluminally. This is because the rate of recession, as in the baloon analogy is proportional to the distance separating them -- which is what Hubble discovered and what convinced Einstein that the universe is expanding.

Originally Posted by Cyberia

Again, I'm no physicist and I probably have misunderstood something along the way (very common) and if so then could somebody please straighten me out.

Your first correct statement -- you are indeed no physicist. Congratulations.

Originally Posted by Cyberia

[You learn by asking questions.

nope

You learn by coming to understand the answers.

Originally Posted by DrRocket

wrong

In fact inflation explains why the universe is smooth on the largest scales, which it is, but lumpy on smaller scales.

The idea of inflation was produced to explain why the universe was believed to be smooth on a large scale. With voids up to a billion light years across, it isn't:


http://www.atlasoftheuniverse.com/superc.html

A garbled analogy, taken from some popularization and distorted.

Same old bear with a sore head making the same old insults.

The speed of light is a local thing and nothing travels faster than light locally. But expansion of space itself is not subject to any limit and as space expands it is possible for the distance between points to increase rapidly enough for points to recede from one another superluminally. This is because the rate of recession, as in the baloon analogy is proportional to the distance separating them -- which is what Hubble discovered and what convinced Einstein that the universe is expanding.

I did mention this so no need to say it again. However it does need a hypersphere (four physical dimensions) to work and there is no evidence of such a thing, so an idea.

nope

You learn by coming to understand the answers.

That assumes that the answers are correct and not just speculation.

Originally Posted by Cyberia

Originally Posted by DrRocket

The speed of light is a local thing and nothing travels faster than light locally. But expansion of space itself is not subject to any limit and as space expands it is possible for the distance between points to increase rapidly enough for points to recede from one another superluminally. This is because the rate of recession, as in the baloon analogy is proportional to the distance separating them -- which is what Hubble discovered and what convinced Einstein that the universe is expanding.

I did mention this so no need to say it again. However it does need a hypersphere (four physical dimensions) to work and there is no evidence of such a thing, so an idea.

Not just wrong, but in fact ridiculous.

Ref: any text on general relativity. Gravitation by Misner, Thorne and Wheeler will do nicely.

Originally Posted by Cyberia

Originally Posted by DrRocket

wrong

In fact inflation explains why the universe is smooth on the largest scales, which it is, but lumpy on smaller scales.

The idea of inflation was produced to explain why the universe was believed to be smooth on a large scale. With voids up to a billion light years across, it isn't:


http://www.atlasoftheuniverse.com/superc.html

Incorrect! The inflation was brought up as a possible explanation for the uniformity of the Cosmic Microwave Backround (CMB). The uniform temperature distribution seen there cannot be explained simply by the exchange of thermal energy due to the limited speed of light. The structure of the current universe is largely irrelevant. They are explained as the result of the tiny anisotropy of the early universe as it is seen in the CMB.

Originally Posted by Cyberia

That assumes that the answers are correct and not just speculation.

Hear, hear!

Originally Posted by Dishmaster

Originally Posted by Cyberia

Originally Posted by DrRocket

wrong

In fact inflation explains why the universe is smooth on the largest scales, which it is, but lumpy on smaller scales.

The idea of inflation was produced to explain why the universe was believed to be smooth on a large scale. With voids up to a billion light years across, it isn't:


http://www.atlasoftheuniverse.com/superc.html

Incorrect! The inflation was brought up as a possible explanation for the uniformity of the Cosmic Microwave Backround (CMB). The uniform temperature distribution seen there cannot be explained simply by the exchange of thermal energy due to the limited speed of light. The structure of the current universe is largely irrelevant. They are explained as the result of the tiny anisotropy of the early universe as it is seen in the CMB.

You need to look deeper into the theory. Yes it does address the "horizon problem", but it also addresses observed anisotropies -- see the discussion on quantum fluctuations here and relationship to observed anisotropies from the Boomereang and CBI experiments.. http://web.mit.edu/physics/news/phys..._cosmology.pdf

Originally Posted by DrRocket

Originally Posted by Dishmaster

Originally Posted by Cyberia

Originally Posted by DrRocket

wrong

In fact inflation explains why the universe is smooth on the largest scales, which it is, but lumpy on smaller scales.

The idea of inflation was produced to explain why the universe was believed to be smooth on a large scale. With voids up to a billion light years across, it isn't:


http://www.atlasoftheuniverse.com/superc.html

Incorrect! The inflation was brought up as a possible explanation for the uniformity of the Cosmic Microwave Backround (CMB). The uniform temperature distribution seen there cannot be explained simply by the exchange of thermal energy due to the limited speed of light. The structure of the current universe is largely irrelevant. They are explained as the result of the tiny anisotropy of the early universe as it is seen in the CMB.

You need to look deeper into the theory. Yes it does address the "horizon problem", but it also addresses observed anisotropies -- see the discussion on quantum fluctuations here and relationship to observed anisotropies from the Boomereang and CBI experiments.. http://web.mit.edu/physics/news/phys..._cosmology.pdf

Thanks for the link. I will read it. I always said, I am no expert in cosmology.

Originally Posted by DrRocket

Not just wrong, but in fact ridiculous.

Ref: any text on general relativity. Gravitation by Misner, Thorne and Wheeler will do nicely.

Another non answer.

Originally Posted by Dishmaster

Incorrect! The inflation was brought up as a possible explanation for the uniformity of the Cosmic Microwave Backround (CMB). The uniform temperature distribution seen there cannot be explained simply by the exchange of thermal energy due to the limited speed of light. The structure of the current universe is largely irrelevant. They are explained as the result of the tiny anisotropy of the early universe as it is seen in the CMB.

The smooth CMB produced the anything but smooth universe. Perturbations, my foot.

Originally Posted by Cyberia

Originally Posted by DrRocket

Not just wrong, but in fact ridiculous.

Ref: any text on general relativity. Gravitation by Misner, Thorne and Wheeler will do nicely.

Another non answer.

A reference to the standard text on general relativity is hardly a non-answer. Read the book fool.

Originally Posted by DrRocket

A refereence to the stabdard text on general relativity is hardly a non-answer. Read the book fool.

Any self confessed genius can tell someone to read a book he has clearly never read. Even a five year old could do that.

Originally Posted by Cyberia

Originally Posted by DrRocket

A refereence to the stabdard text on general relativity is hardly a non-answer. Read the book fool.

Any self confessed genius can tell someone to read a book he has clearly never read. Even a five year old could do that.

Not nearly as easily as someone who owns and has read the book -- like me.

What is abundantly clear is that you have never read, or at least have never understood, any real physics or mathematics text.

We await your first correct statement regarding either subject.

Originally Posted by DrRocket

Not nearly as easily as someone who owns and has read the book -- like me.

Evidence, other than hand waving? I know you're lying. Any worthwhile book I read, I can use the material for posts on forums, something you have flatly refused to do. Liar.

What is abundantly clear is that you have never read, or at least have never understood, any real physics or mathematics text.

We await your first correct statement regarding either subject.

Another non answer from a non entity.

Originally Posted by Cyberia

Originally Posted by DrRocket

Not nearly as easily as someone who owns and has read the book -- like me.

Evidence, other than hand waving? I know you're lying. Any worthwhile book I read, I can use the material for posts on forums, something you have flatly refused to do. Liar.

I have told you what the books say in simple language. I don't need to reproduce long passages and do not intend to do so.

Your inability to understand is due to your own iadequacies. Stupidity is like that.

Now go do a little homework and read a real book on cosmology.

Originally Posted by DrRocket

I have told you what the books say in simple language. I don't need to reproduce long passages and do not intend to do so.

You refused to say what is in the books, in posts that are still there for all to see.

Your inability to understand is due to your own iadequacies. Stupidity is like that.

Now go do a little homework and read a real book on cosmology.

I have explained to you a number of times why I cannot read the books you list but your comprehension skills are so very, very poor that you have failed to understand, as you have failed to understand anything in these books so cannot quote anything.

Now stop spamming your hatred of me and get on with your crappy life.

Originally Posted by Cyberia

I have explained to you a number of times why I cannot read the books you list but your comprehension skills are so very, very poor that you have failed to understand, as you have failed to understand anything in these books so cannot quote anything.

Now stop spamming your hatred of me and get on with your crappy life.

No you have not.

You have, on the other hand demonstrated that you lack the capability to understand physics in general. Iguess it all boils down to intelligence.

Originally Posted by DrSpamit

No you have not.

You have, on the other hand demonstrated that you lack the capability to understand physics in general. Iguess it all boils down to intelligence.

Now stop spamming your hatred of me and get on with your crappy life.

Originally Posted by Cyberia

Originally Posted by DrSpamit

No you have not.

You have, on the other hand demonstrated that you lack the capability to understand physics in general. Iguess it all boils down to intelligence.

Now stop spamming your hatred of me and get on with your crappy life.

We don't do the insult-by-changing-the-username bit here.

Temp suspension for your account.

Next warning is the last.

I read what I can and I look for books on cosmology that are written in layman's terms. Usually I end up reading them over and over, and still there's always something I can't grasp. Something I read about in a Paul Davies book still bugs me because I never really got it and is the basis for my next dumb question.

Is Davies-Unruh radiation the same as Hawking radiation? I struggle trying to understand the D-U effect. Perhaps someone can shed some info on it. Not really sure if it's a theory that's been tested or if it is impossible to test. I would also like to know if Hawking radiation has been confirmed or if it is also an untested theory.

Originally Posted by zinjanthropos

I read what I can and I look for books on cosmology that are written in layman's terms. Usually I end up reading them over and over, and still there's always something I can't grasp. Something I read about in a Paul Davies book still bugs me because I never really got it and is the basis for my next dumb question.

Is Davies-Unruh radiation the same as Hawking radiation? I struggle trying to understand the D-U effect. Perhaps someone can shed some info on it. Not really sure if it's a theory that's been tested or if it is impossible to test. I would also like to know if Hawking radiation has been confirmed or if it is also an untested theory.

The Davies-Unruh effect is predicted by general relativity, and relates to an accelerating observer perceiving a different background temperature than a non-accelerated observer. Unruh radiation may result, although this is not uncontested. There are disputed claims that Unruh radiation has been observed.

Hawking radiation is predicted by quantum field theory in curved spacetime. That theory is not rigorously formulated. It predicts a very low level of emission from a black hole due to quantum effecvts. It has not been observed, and likely will not be any time soon, since even if it exists the effect is very small.

Unruh radiation and Hawking radiation are different things.

Originally Posted by DrRocket

The Davies-Unruh effect is predicted by general relativity, and relates to an accelerating observer perceiving a different background temperature than a non-accelerated observer. Unruh radiation may result, although this is not uncontested. There are disputed claims that Unruh radiation has been observed.

I have a great deal of trouble with the word "perceive". Perceive has me thinking that what is sensed is in reality something your brain doesn't truly recognize. An observer can't see temperature but they could feel it. Since this is background temperature are we talking about something one can use a thermometer to measure?

Originally Posted by zinjanthropos

Originally Posted by DrRocket

The Davies-Unruh effect is predicted by general relativity, and relates to an accelerating observer perceiving a different background temperature than a non-accelerated observer. Unruh radiation may result, although this is not uncontested. There are disputed claims that Unruh radiation has been observed.

I have a great deal of trouble with the word "perceive". Perceive has me thinking that what is sensed is in reality something your brain doesn't truly recognize. An observer can't see temperature but they could feel it. Since this is background temperature are we talking about something one can use a thermometer to measure?

Perceive in this case means "measure in one's own reference frame". It has nothing to do with psychology. The word is pretty common, along with "see" in discussions involving relativity.

You would probably use an IR thermometer of some sort in this particular application.

Originally Posted by DrRocket

Perceive in this case means "measure in one's own reference frame". It has nothing to do with psychology. The word is pretty common, along with "see" in discussions involving relativity.

You would probably use an IR thermometer of some sort in this particular application.

Thanks Doc... going to go back later and read up on it again with that in mind, it's a big help. That word pops up a lot in books on cosmology. I like the way Davies writes, for an average stiff like myself it's not so hard to take. I like him better than Hawking.

Originally Posted by zinjanthropos

Originally Posted by DrRocket

Perceive in this case means "measure in one's own reference frame". It has nothing to do with psychology. The word is pretty common, along with "see" in discussions involving relativity.

You would probably use an IR thermometer of some sort in this particular application.

Thanks Doc... going to go back later and read up on it again with that in mind, it's a big help. That word pops up a lot in books on cosmology. I like the way Davies writes, for an average stiff like myself it's not so hard to take. I like him better than Hawking.

Davies is OK.I generally prefer either real hard-core science books or popularizations by the very top researchers. Hawking is one -- but his most recent, The Grand Design is awful.

Davies is a good scientist, but not in Hawking's class. He wrote a really good book, Superstrings: A Ttheory of Everything ? that consists of interviews with the A-team.[/tex]

Originally Posted by zinjanthropos

Since this is background temperature are we talking about something one can use a thermometer to measure?

In principle yes, but there are so many other heat sources in the universe that it becomes quite difficult to disentangle all the contributions. The best way to illustrate and overcome the problem are the COBE and WMAP results.

You can't use a simple thermometer for this purpose, but you can measure the energy distribution spectrum of the radiation, like it was done with COBE. It is a continuous Planck spectrum of a perfect Black Body. It is uniquely determined by the temperature. The peak of the distribution tells you exactly, what the temperature is.


Disentangling can be done by spatially resolving the different contributors. The image below contains lots of radiation coming from the Milky Way. This must be subtracted from the data by applying models in order the retrieve the background radiation alone.

Originally Posted by Dishmaster

In principle yes, but there are so many other heat sources in the universe that it becomes quite difficult to disentangle all the contributions.

You can't use a simple thermometer for this purpose, but you can measure the energy distribution spectrum of the radiation, like it was done with COBE. It is a continuous Planck spectrum of a perfect Black Body. It is uniquely determined by the temperature. The peak of the distribution tells you exactly, what the temperature is.

Disentangling can be done by spatially resolving the different contributors. The image below contains lots of radiation coming from the Milky Way. This must be subtracted from the data by applying models in order the retrieve the background radiation alone.

I'd love to understand physics and cosmology the way you guys can. Simple things like knowing how to get those temperatures.

So how did Davies & Unruh deduce this effect? What is it about GR that led them to this hypothesis?