History of the Big Bang

[Jim_Baur]

I am sure this has been written about here a great deal.

I will keep my question short.

How has the discovery of dark matter and dark energy effected the original math?

Thanks!

 

[kompaz]

Short answer: on this graph

physics.uoregon.edu/~jimbrau/BrauImNew/Chap26/6th/26_Discovery02-F.jpg

if there was no dark energy the Universe would evolve along the purple line. According to present understanding we are somewhere between the purple line and the green line.

Fun fact: Einstein’s cosmological equations actually include dark energy. This is because his original equation indicated that the universe is expanding… and he believed that the universe was static (universal expansion has not yet been discovered), so he added a negative cosmological constant to arrive at static universe. When Hubble discovered that the Universe indeed expands, the cosmological constant was viewed as Einstein’s blunder… but, when dark energy was discovered people noted that they could include it in Einstein’s equations by assuming a cosmological constant with a positive value.

 

[empther]

Very recently, about two years ago I think, surveys of the distributuion of galaxies in the universe indicated that without the gravity of dark matter, visible matter, that is hydrogen, would have been too thinly dispersed in space to coelesce into stars and galaxies,
and we would not be here.

 

[Poseidon]

I can’t give you a mathematical answer, since I don’t know the math myself, but basically, dark matter is added in because there isn’t nearly enough luminous matter to explain the current state of the universe. If there was only luminous matter then the universe would just be a bunch of fine, dispersed particulate, because it would never have coalesced into the structures (galaxies, etc) that we have today.

Dark energy is a theory put forward to explain the acceleration of the expansion of the universe. Not only is the universe expanding, but it’s expanding faster and faster each minute.

Hopefully this helps a bit!

 

[Jim_Baur]

Thanks for the helpful ideas!

 

[empther]

dark matter is added in because there isn’t nearly enough luminous matter to explain the current state of the universe. If there was only luminous matter then the universe would just be a bunch of fine, dispersed particulate, because it would never have coalesced into the structures (galaxies, etc) that we have today.

Dark matter isn’t just a fudge factor. It has been detected.

Galaxies don’t rotate at the correct speeds for the amounts of visible matter they have.

There has to be enormous amounts of dark matter to provide the mass needed.

---

In my book, a mysterious entity called HAL is made of dark matter.

 

[Drinkgasoline]

There should be a science section for this forum

 

[Alberti_Devoveo]

Dark matter isn’t just a fudge factor. It has been detected.

Galaxies don’t rotate at the correct speeds for the amounts of visible matter they have.

There has to be enormous amounts of dark matter to provide the mass needed.

---

In my book, a mysterious entity called HAL is made of dark matter.

Neither dark matter nor dark energy has been detected. Only the effects of these materials have been detected. Some, like myself, posit that higher order terms (like multiples of the Ricci scalar) need to be added to the Lagrangian in the action integral and satisfactory explanations are given, instead of invoking WIMPs (Weakly Interacting Massive Particles).

 

[Jim_Baur]

Concerning the size of the universe of which we knew and know, how much bigger is the universe now than in the 1950s? (This question is based on our knowledge of the universe, and not it actual size.)

In a similar manner, how fast is the actual size of the universe growing? When will it double? Or how often does it double in size?

Thanks!

 

[Alberti_Devoveo]

Concerning the size of the universe of which we knew and know, how much bigger is the universe now than in the 1950s? (This question is based on our knowledge of the universe, and not it actual size.)

In a similar manner, how fast is the actual size of the universe growing? When will it double? Or how often does it double in size?

Thanks!

The universe expands at a rate of about 71 kilometers per second per megaparsec (one parsec is about 3.1x10[sup]18[/sup] cm = 3.25 lightyears). This means that a galaxy that is 200 megaparsecs away from us is moving at a speed of 71 km/s/Mpc * 200 Mpc = 1420 km/s away from us while a galaxy 1 megaparsec away is moving 71 km/s.

 

[empther]

Neither dark matter nor dark energy has been detected. Only the effects of these materials have been detected.

Now there’s a classic case of quibbling!

 

[Alberti_Devoveo]

Now there’s a classic case of quibbling!

To be fair, you had presented a classic case of misinformation!

While I give credence to DE (I have had lots of conversations with researchers and read many papers to accept it, I was fairly rigorous in my denial of it), I think DM is bunk. According to this theory, these particles outnumber the baryonic matter nearly 5 to 1, yet we have not observed one. We have not observed even a transition from one energy state to another. Nor have we observed a decay through the b bar b channel.

 

[empther]

I think DM is bunk. According to this theory, these particles outnumber the baryonic matter nearly 5 to 1, yet we have not observed one. We have not observed even a transition from one energy state to another. Nor have we observed a decay through the b bar b channel.

Can you explain why galaxies spin so fast they should fly apart if there is no dark matter?

 

[Alberti_Devoveo]

Can you explain why galaxies spin so fast they should fly apart if there is no dark matter?

I already have done so in the post you originally quoted from me: higher ordered terms in the Lagrangian (in the action integral). This is sometimes (erroneously) called MOND, but really is f(R) and F(T) theories of gravity.
These theories and DM theories both produce data that match observations. Which do you find more plausible: higher order physics (like taking a jump from Newtonian to Einsteinian mechanics) or an invisible particle that is non-baryonic but material?

 

[empther]

Originally Posted by empther

forums.catholic-questions.org/images/buttons_khaki/viewpost.gif
Can you explain why galaxies spin so fast they should fly apart if there is no dark matter?

I already have done so in the post you originally quoted from me: higher ordered terms in the Lagrangian (in the action integral). This is sometimes (erroneously) called MOND, but really is f(R) and F(T) theories of gravity.

I see.
So you’ve proven that all the astronomers are wrong, hunh?

You should get the Nobel Prize for Funnyphysics.

 

[Alberti_Devoveo]

I see.
So you’ve proven that all the astronomers are wrong, hunh?

You should get the Nobel Prize for Funnyphysics.

I have not proven any of my colleagues wrong or right. The f(R) and f(T) theories of gravity offer plausible explanations of galactic phenomena without resorting to inventing a non-baryonic matter that is very near impossible to observe directly.

 

[Jim_Baur]

Thanks for the help.

Concerning our knowledge of the size of the universe in 1945, how much larger is it than we thought it was in 1945? (If we include the dark matter and dark energy.)

Again, thanks!

God bless

 

[Alberti_Devoveo]

Thanks for the help.

Concerning our knowledge of the size of the universe in 1945, how much larger is it than we thought it was in 1945? (If we include the dark matter and dark energy.)

Again, thanks!

God bless

That is a tough question because the universe is expanding. I do not know the value, however, we can certainly estimate it. Assume that the universe expands linearly with time (i.e., R[sub]Universe[/sub]=ct). From here, we can see that:

• 50 years = 1.58x10[sup]9[/sup] seconds
• using c=2.9979x10[sup]10[/sup] cm/s, then R[sub]50 years[/sub] = 4.76x10[sup]19[/sup] cm
• using V=4piR[sup]3[/sup]/3, then V[sub]50 years[/sub]=4.52x10[sup]59[/sup] cm[sup]3[/sup]

That is a pretty big number! However, we really need to compare this value to the linearly-interpolated volume of the universe.

• 13.7 billion years = 4.32x10[sup]17[/sup] s
• R[sub]Universe[/sub]=ct=1.30x10[sup]28[/sup] cm
• V[sub]Universe[/sub]=4piR[sup]3[/sup]/3=2.90x10[sup]84[/sup] cm[sup]3[/sup]

This is an even bigger number! The difference of 50 years seems like a lot, but compared to the entire universe, it is rather insignificant!

Also: the expansion rate was determined via observations and is independent of the existence/non-existence of dark matter and/or dark energy.

 

[winc]

That is a tough question because the universe is expanding. I do not know the value, however, we can certainly estimate it. Assume that the universe expands linearly with time (i.e., R[sub]Universe[/sub]=ct). From here, we can see that:

• 50 years = 1.58x10[sup]9[/sup] seconds
• using c=2.9979x10[sup]10[/sup] cm/s, then R[sub]50 years[/sub] = 4.76x10[sup]19[/sup] cm
• using V=4piR[sup]3[/sup]/3, then V[sub]50 years[/sub]=4.52x10[sup]59[/sup] cm[sup]3[/sup]

That is a pretty big number! However, we really need to compare this value to the linearly-interpolated volume of the universe.

• 13.7 billion years = 4.32x10[sup]17[/sup] s
• R[sub]Universe[/sub]=ct=1.30x10[sup]28[/sup] cm
• V[sub]Universe[/sub]=4piR[sup]3[/sup]/3=2.90x10[sup]84[/sup] cm[sup]3[/sup]

This is an even bigger number! The difference of 50 years seems like a lot, but compared to the entire universe, it is rather insignificant!

Also: the expansion rate was determined via observations and is independent of the existence/non-existence of dark matter and/or dark energy.

so how much closer was the sun to the earth over all those millions and billions of years ago and how about the initial short distance for the speed of light to travel - btw no water canopy protection from the sun - winc

 

[Alberti_Devoveo]

so how much closer was the sun to the earth over all those millions and billions of years ago and how about the initial short distance for the speed of light to travel - btw no water canopy protection from the sun - winc

Earth was created about 4.5 billion years ago at a distance from the sun that is not much different from the current distance of 1 AU (astronomical unit, about 1.5x10[sup]13[/sup] cm). Light from the sun’s surface would have taken about the same 8 minutes it does now.