E4.8-4.14

E4.8: Distinguish between the terms open, flat and closed when used to describe the development of the universe.

An open universe is one that continues to expand- gravity slows down the rate of expansion, but it is not enough to stop it.

A closed universe is one that will eventually collapse back on itself- the force of gravity is great enough to stop the rate of expansion. This would result in a BIG CRUNCH, the reverse of a BIG BANG.

A flat universe is in between an open and a closed universe- the force of gravity slows the expansion, but theoretically, it takes an infinite time to come to rest.

Image from: Heinemann HL- Chris Hamper

E4.9: Define the term 'critical density' by reference to a flat model of the development of the universe.

The critical density, ρ0, is defined as the theoretical value of the density that would create a flat universe.

15) a)Actual density < Critical density: OPEN universe, Actual density = Critical density: FLAT universe, Actual density > Critical density: CLOSED universe

bi) p= 3 x ((2.7 x 10^-18)^2)/ (8π x 6.67x10^-11)
p= 1.3 x 10^-26 kg m^-3

ii) Determining the equivalent no. of nucleons per unit volume:

(NOT SURE)


E 4.10: Discuss how the density of the universe determines the development of the universe.

The outcome depends on the mass density- the amount of matter per unit volume available to provide gravitational attraction.

If the density is GREATER than the critical density, it will head towards a CLOSED universe, and if it is LOWER than the critical density, it will head towards an OPEN universe.

E4.11: Discuss problems associated with determining the density of the universe.

The density of the universe is not an easy quantity to measure- to determine this, we need to know how much mass it contains- it should be relatively easy to estimate by estimating the number of stars and their average mass. However, we can only see about 10% of the universe- the rest is made up of dark matter, which is too cool for its radiation to be detected. Hence, the estimated value for the mass is inaccurate.

There are a number of possible theories to explain why there is so much dark matter and what it consists of. These include:

-The matter could be found in Massive Astronomical Compact Halo Objects (MACHOs)- these are low mass "failed" stars, or high- mass planets, or could even be black--holes, and would produce little or no light.

-There are some fundamental particles (neutrinos) that exist in huge numbers; it is unknown whether their masses are 0 or very small- if they have some mass, it could account for a lot of the missing mass.

-There may be new particles which we do not know about- Weakly Interacting Massive Particles (WIMPs)

E4.12- State that current scientific evidence suggests that the universe is OPEN.

Current scientific evidence suggest that the universe is open. In 1997, cosmologists discovered that Supernova explostions in distant galaxies showed that the expansion of the universe was accelerating.
So the universe appears to be more open than expected. There must be some other previously unknown force, acting in opposition to gravity, which is pushing the universe apart. This new phenomenon is called 'DARK ENERGY'.

E4.13: Discuss an example of the international nature of recent astrophysics research.

Articles:

http://www.nrao.edu/pr/2009/bhbulge

http://www.research-in-germany.de/53166/2010-09-27-new-astronomical-phenomenon

E4.14 Evaluate arguments related to investing significant sources into researching the nature of the universe.

FOR:
-Understanding the nature of the universe can help us understand philosophical questions such as:
-Why are we here?
-Is there life elsewhere in the universe?

-It is one of the most fundamental and interesting areas for mankind, and thus deserves to be researched.

-This research will give rise to new technology, which may eventually improve the quality of life for many people.

-Life on Earth may become impossible at some time in the future, so we must be able to colonize new planets (:

AGAINST:
- If money is to be allocated to research, we may be able to get better returns from medical research

-The money could be better spent on providing food, shelter and medical care to the millions of people suffering from hunger, homelessness and disease- OPPORTUNITY COST.

-It may be better to fund a large amount of small diverse research than putting lots of funding into one field

-Is the information gained really worth the cost?