More questions about the universe

[JustinW]

How can a cosmological constant be constant? Any energy density or force should still follow conservation principles, shouldn't it? So how can a constant remain stable or even accelerate without some sort of input?

 

 

Also shouldn't this conservation law be apllied to gravity? Does gravity weaken over time by energy conservation?

 

 

It seems to me that force should also be accounted for when figuring the overall density of the universe, and not just baryonic matter. It seems that energy or force can be detrimental to a systems density or pressure. Why is it not included in such a measurement?

 

 

 

Just some short questions for now.

[DrRocket]

How can a cosmological constant be constant? Any energy density or force should still follow conservation principles, shouldn't it? So how can a constant remain stable or even accelerate without some sort of input?

 

 

Also shouldn't this conservation law be apllied to gravity? Does gravity weaken over time by energy conservation?

 

 

It seems to me that force should also be accounted for when figuring the overall density of the universe, and not just baryonic matter. It seems that energy or force can be detrimental to a systems density or pressure. Why is it not included in such a measurement?

 

 

 

Just some short questions for now.

 

 

Eneergy conservation in general relativity is a bit of a problem. Energy can be shown to be conserved locally -- at any single point. But energy is not necessarily conserved over a non-zero volume. So there is no global conservation of energy law in general relativity. This is not as serioius an issue as you might think since enrgy conservation is normally thought of as applying between two instants of time, and there is not such thing as global time in general relativity either.

 

To compound that problem, gravitational potential energy is not clearly defined in general relativity.

 

The cosmological constant does not "accelerate" but rather is a factor in the field equations that describe the spacetime metric and it is metric expansion of space that is accelerating.

 

Pressure is included in the stress-energy tensor that determines spacetime curvature. A positive cosmological constant is equivalent to a negative pressure term, and that is the possible connection between the quantum mechanical notion of the zero point energy of the vacuum and the cosmological constant. Unfortunately the best estimate of the cosmological constant in terms of that vacuum energy overpredicts the observed cosmological constant by 120 orders of magnitude.

[JustinW]

The cosmological constant does not "accelerate" but rather is a factor in the field equations that describe the spacetime metric and it is metric expansion of space that is accelerating.

Yeah I should have thought about that as a force applied constantly, as opposed to a strengthening force. One more dunce moment on my part.

So there are two forces that are constants that we know of so far that have no implications of entropy or conservation? The constant and gravity? Those two are about the trickiest subjects to read about that I've come across so far.

[JustinW]

As stars explode they not only form heavier elements, like oxygen and carbon, but also leave behind materials that make up new stars that are less massive. Since the new stars can never be as strong as the old ones, what does the future hold for stars in general? In this scenario, stars, life, and even black holes will be a thing of the past? If so it's kind of depressing to think that we will never be able to outrun our own extinction.

 

I've heard about a so called "death star" galaxy, galaxy 3c321, that has been emitting a plasma jet at twice the SOL for over 2 million years. This plasma is made up of ions and electrons and it is thought that the magnetic fields coupled with the very high rate of rotation is responsible for the power of this jet. But how can these particles in this jet be faster than the SOL? I thought that was the cosmic speed limit of any known particles.

 

I have heard about wondering stars that are ejected out of a system to wonder the cosmos. Observed? Just likely? How do we know other than speculating the high probability?

 

The "void" is an interesting concept. Some have attributed it to the very "fabric" of space all the way down to the make up of atoms(the reason why they are mostly hollow). What are your thoughts on the subject and does anyone think that we will ever be able to test this idea?

 

In 1843 a spuernova formed the Eta Corina nebula that has enough mass to collapse into a black hole within the next million years. I had thought that nebula usually ignite into stars rather than skip right into supernova. Is it possible that a nebula can collapse like that?

 

What exactly is the process that tells us the relative age of the universe. Is it a mathematical calculation that tracks trajectories back to their origins, or is there some other means that give us an affirmative time?

 

Why couldn't dark energy be thought of as the opposite of gravity? Does anyone say whether or not gravity was created by the BB? Or could it have already been there and it was the BB that gave it something(matter) to act upon? I've heard some say that dark energy was created in the BB, but could it not also be that it too was always there as an intrensic value? Are there any models that may explain what they are, where they came from, and how they work?

 

They say that life may be present in ice on moons or in oceans on moons, but doesn't life need some heavier elements, like carbon and such, to form life? And wouldn't the absence of a molten core mean that these heavier elements are likely not present?

 

 

If jupiter is made up mostly of hydrogen and helium, is it's gravity just not strong enough to ignite these elements? Is it not massive enough?

 

If jupiter is such a catalist in projecting asteroids towards earth at such high velocities, then why are we not following Near Jupiter Objects the same as we follow Near Earth Objects? Or do we?

 

 

 

I think that's all the questions I have for now. More are sure to follow.