What are the unanswered questions in Cosmology?

  • Thread starter jimjohnson
  • Start date
  • Tags
    Cosmology
In summary: I think what you had in mind is the period of accelerated expansion in the early universe, which may or may not be due to inflation. We shall see.
  • #1
jimjohnson
84
0
What are the greatest mysteries in Cosmology? Please comment on my list.
1 Complete explanation of black holes, what happens to time and space (worm holes?).
2 Process of symmetry breaking during initial stages of the of the big bang (includes matter/antimatter unbalance).
3 Source and characteristics of dark matter.
4 Source and characteristics of dark energy (cosmological constant).
5 Nature of gravity waves.
6 Is space and time discrete?
7 Source of ultra-high-energy cosmic rays.
8 Ultimate fate of the universe.
Any more?
 
Space news on Phys.org
  • #3
What happened at the big bang, was there a before and if so what?
Did inflation happen ? If so , how and is it eternal or not?
 
  • #5
Loosely related to cosmology in Cosmological horizons though more QM related. Particle entanglement.

Thats about the only thing I could think of to the list above
 
  • #6
After reviewing the open questions in physics by John Baez, I compiled a revised list of the greatest mysteries in Cosmology. They are organized in three groups as shown below. Comments?
Big Bang/Universe
1 What happened before the big bang?
2 What was the process of symmetry breaking during initial stages of the of the big bang (includes matter/antimatter unbalance and inflation theory)?
3 Is the universe finite or infinite?
4 Are there more than 4 dimensions?
5 Is space and time discrete (arrow of time)?
6 What is the ultimate fate of the universe?
Energy/Forces
1 What is the source and characteristic of dark matter?
2 What is the source and characteristic of dark energy (cosmological constant)?
3 What is the nature of gravity waves?
Other
1 Is there a complete explanation of black holes, what happens to time and space (worm holes)?
2 What is the source of ultra-high-energy cosmic rays?
3 Why are galaxies distributed in clumps and filaments?
4 When were the first stars formed and what type were they?
 
  • #7
jimjohnson said:
4 When were the first stars formed and what type were they?

Fairly sure I read or saw on a programme that the first stars formed about 10 billion years ago. They were huge short lived stars composed of hydrogen. From other sources I've read, at this point only hydrogen, helium and lithium were most likely in existence with other elements being formed later from those stars deaths.
 
  • #8
Fairly sure I read or saw on a programme that the first stars formed about 10 billion years ago. They were huge short lived stars composed of hydrogen. From other sources I've read, at this point only hydrogen, helium and lithium were most likely in existence with other elements being formed later from those stars deaths.

does the deep field image not show a galaxy of 13.2 billion light years away? this must mean stars formed before 10 billion years ago
 
  • #9
Johnahh said:
does the deep field image not show a galaxy of 13.2 billion light years away? this must mean stars formed before 10 billion years ago



There are also some stars which are measured to be older than big bang,but this doesn't make sense as we all know that big bang is the start of every thing. Either our estimation of the time of big bang must be false or the time of formation of stars must be false.
 
  • #10
night_sky said:
There are also some stars which are measured to be older than big bang,but this doesn't make sense as we all know that big bang is the start of every thing. Either our estimation of the time of big bang must be false or the time of formation of stars must be false.

They aren't older, but further away than normal expansion can explain. This is where inflation comes into play. Somehow, it appears that space became larger, for want of a better word, between our planet and a source. Space with gravitation bound entities expand slowly in their region but no longer inflate. That region can contain galaxies that are bound together as we are with Andromeda. Then there is space that doesn't have any gravitation bound entities and these areas appear to inflate instead of expand. This causes distant areas of space to recede from us, some at faster than light speed. This leads to our being able to see objects further away than the age of the Universe. The important part is that the object isn't moving away from us at great speeds, but the light from the object is having to travel further to reach us because of the inflation.

Scientists with math beyond my abilities can explain the effects that are happening. We don't know why or how though. It is believed by many that Dark Energy, which we don't know exactly what that is, plays a part. Some believe a particle called an Inflaton, which hasn't been found, could also play a role.

I'll also say my age of 10 billion was probably from old data. I did come across some recent findings of primordial gas with no heavy elements, that is from 750 million years after the Big Bang. You can read about that here http://phys.org/news/2012-12-stars-universe-million-years.html
They also mention less than 11 billion years ago heavy elements can be detected. That would suggest that some stars had formed and created heavy elements by that time.
 
  • #11
Ogr8bearded1 said:
They aren't older, but further away than normal expansion can explain. This is where inflation comes into play. Somehow, it appears that space became larger, for want of a better word, between our planet and a source. Space with gravitation bound entities expand slowly in their region but no longer inflate. That region can contain galaxies that are bound together as we are with Andromeda. Then there is space that doesn't have any gravitation bound entities and these areas appear to inflate instead of expand.
You must be very careful with your terminology: inflation is a specific kind of expansion. Expansion occurs whenever the Hubble parameter, [itex]H=\dot{a}/a[/itex], is positive (contraction, when it is negative). Inflation is accelerated expansion, i.e. [itex]\ddot{a} > 0[/itex]. Now, no expansion takes places -- inflationary or otherwise -- in gravitationally bound structures (solar systems, galaxies, etc.).
 
  • #12
Thanks bapowell, I'm still trying to learn all the correct terminology. What I meant to say was that the area of a gravitation bound region could become larger. Such as, our solar system is a certain size now. If the Sun lost mass, such as it will when starts dying, the planets would orbit further away from it. Everything is still bound to each other but is now further apart and covering more area. The way I phrased it was that space in that region was slowly expanding and that was wrong.
 

1. What is dark matter and dark energy?

Dark matter and dark energy are two of the biggest mysteries in cosmology. Dark matter is a type of matter that does not emit or absorb light, making it invisible to telescopes. Its existence is inferred through its gravitational effects on visible matter. Dark energy, on the other hand, is a hypothetical form of energy that is believed to be responsible for the accelerating expansion of the universe.

2. What caused the Big Bang?

The Big Bang theory is the most widely accepted explanation for the origins of the universe. However, the exact cause of the Big Bang is still unknown. Some theories suggest that it was the result of a quantum fluctuation in a pre-existing state of nothingness, while others propose that it was triggered by the collision of two branes in a higher-dimensional space.

3. Is the universe infinite or finite?

This question has been debated by scientists for centuries. The latest evidence suggests that the universe is most likely infinite in size, but it is still expanding. However, there is no way for us to know for sure if the universe is truly infinite, as our observable universe is limited by the speed of light.

4. What is the fate of the universe?

Scientists have proposed several possible scenarios for the future of the universe. One possibility is the "Big Freeze," in which the universe will continue to expand and eventually all matter and energy will dissipate, resulting in a cold and lifeless universe. Another possibility is the "Big Crunch," in which the expansion of the universe will eventually halt and reverse, leading to a collapse and possibly a new Big Bang. However, the fate of the universe is still uncertain and more research is needed to determine which scenario is most likely.

5. Are there other universes or dimensions?

Many theories in cosmology, such as string theory and the multiverse theory, suggest the existence of other universes or dimensions beyond our own. However, there is currently no concrete evidence to support these theories, and the concept of multiple universes or dimensions remains a topic of debate among scientists.

Similar threads

Replies
1
Views
1K
Replies
4
Views
1K
Replies
37
Views
2K
Replies
8
Views
1K
Replies
13
Views
2K
  • Cosmology
Replies
4
Views
1K
Replies
20
Views
2K
Replies
4
Views
1K
Replies
25
Views
1K
Replies
5
Views
1K
Back
Top