Thread: About the big bang theory

a few questions about the big bang theory, the expansion of the universe and the singularity:

1) why the cosmological singularity is superdense and superhot, and if in the superdense state the molecules do not move, and therefore the temperature does not rise (from a school physics course, the higher the speed of movement of the molecules, the higher the temperature)

2) the most important question: why at the moment there can be a big difference in temperature for different parts of the universe, because as I understand it, the expansion is the same in all right directions and, so to speak, in the primary state of the universe (singularity), all parts of the universe should have the same temperature (or not ?)

Actually, cosmologists are asking the opposite question: How can the cosmic microwave background radiation (CMBR) resulting from causally disconnected random fluctuations be so uniform across the sky? It is the uniformity of the CMBR that cosmological inflation attempts to explain. It should be noted that the well known images of the CMBR provides an exaggerated view of the variations across the sky, which are only about 18 μK compared to the 2.726 K of the CMBR itself.

Originally Posted by KJW

Actually, cosmologists are asking the opposite question: How can the cosmic microwave background radiation (CMBR) resulting from causally disconnected random fluctuations be so uniform across the sky? It is the uniformity of the CMBR that cosmological inflation attempts to explain. It should be noted that the well known images of the CMBR provides an exaggerated view of the variations across the sky, which are only about 18 μK compared to the 2.726 K of the CMBR itself.

no, wait, in one apartment, let's say the temperature is 19c and in another 22c, and how this diversity "flowed" from the non-diversity (homogeneous "broth" (this is how I imagine kosm.singularly aka the state of the universe many years ago (the big bang theory)) ?

Originally Posted by Anffaeledig

Originally Posted by KJW

Actually, cosmologists are asking the opposite question: How can the cosmic microwave background radiation (CMBR) resulting from causally disconnected random fluctuations be so uniform across the sky? It is the uniformity of the CMBR that cosmological inflation attempts to explain. It should be noted that the well known images of the CMBR provides an exaggerated view of the variations across the sky, which are only about 18 μK compared to the 2.726 K of the CMBR itself.

no, wait, in one apartment, let's say the temperature is 19c and in another 22c, and how this diversity "flowed" from the non-diversity (homogeneous "broth" (this is how I imagine kosm.singularly aka the state of the universe many years ago (the big bang theory)) ?

It's not clear what you're going on about. It seems that you may be wondering why not all objects in the universe are at the same temperature. Is that it?

Originally Posted by tk421

Originally Posted by Anffaeledig

Originally Posted by KJW

Actually, cosmologists are asking the opposite question: How can the cosmic microwave background radiation (CMBR) resulting from causally disconnected random fluctuations be so uniform across the sky? It is the uniformity of the CMBR that cosmological inflation attempts to explain. It should be noted that the well known images of the CMBR provides an exaggerated view of the variations across the sky, which are only about 18 μK compared to the 2.726 K of the CMBR itself.

no, wait, in one apartment, let's say the temperature is 19c and in another 22c, and how this diversity "flowed" from the non-diversity (homogeneous "broth" (this is how I imagine kosm.singularly aka the state of the universe many years ago (the big bang theory)) ?

It's not clear what you're going on about. It seems that you may be wondering why not all objects in the universe are at the same temperature. Is that it?

yes, why is there such a heterogeneity in temperature when everything, as for me, began to expand from a homogeneous medium.

I would love

Originally Posted by Anffaeledig

Originally Posted by tk421

Originally Posted by Anffaeledig

Originally Posted by KJW

Actually, cosmologists are asking the opposite question: How can the cosmic microwave background radiation (CMBR) resulting from causally disconnected random fluctuations be so uniform across the sky? It is the uniformity of the CMBR that cosmological inflation attempts to explain. It should be noted that the well known images of the CMBR provides an exaggerated view of the variations across the sky, which are only about 18 μK compared to the 2.726 K of the CMBR itself.

no, wait, in one apartment, let's say the temperature is 19c and in another 22c, and how this diversity "flowed" from the non-diversity (homogeneous "broth" (this is how I imagine kosm.singularly aka the state of the universe many years ago (the big bang theory)) ?

It's not clear what you're going on about. It seems that you may be wondering why not all objects in the universe are at the same temperature. Is that it?

yes, why is there such a heterogeneity in temperature when everything, as for me, began to expand from a homogeneous medium.

I would love

You seem to be assuming that the large-scale homegeneity of the CMBR implies perfect homogeneity at all scales. That's incorrect. Note that measurements of the CMBR do show heterogeneities. They're small, but they are not zero.

Quantum fluctuations would suffice to seed the formation of galaxies, for example, as considerable modeling efforts have shown. I would say that this work is far from complete, but it successfully shows that the existence of galaxies, stars and planets is consistent with the CMBR that we measure.

And, as KJW noted in his reply, inflation has been invoked to explain the remarkable homogeneity that is observed. Inflation would amplify small-scale fluctuations while simultaneously explaining the large-scale uniformity of the CMBR. Inflation may have its own problems as a theory, but it does answer many deep questions.