The age of the univverse is CALCULATED!

Nzowa Godat

JF-Expert Member
Jun 15, 2011
2,757
2,000
The ΛCDM model is based on
six parameters: physical
baryon density, physical dark
matter density, dark energy
density, scalar spectral index,
curvature fluctuation
amplitude and reionization
optical depth. From these the
other model values, including
the Hubble constant and age of
the universe, can be derived.
Parameter values listed below
are from the Seven-Year
Wilkinson Microwave
Anisotropy Probe
(WMAP) temperature and
polarization observations.[2]
These include estimates based
on data from Baryon Acoustic
Oscillations[3] and Type Ia
supernova luminosity/time
dilation measurements.[4]
Implications of the data for
cosmological models are
discussed in Komatsu et al. [5]
and Spergel et al.[6]
Parameter
Value
Description
t0
years
Age of the universe
H0
km s−1Mpc−1
Hubble constant
Ωbh2
Physical baryon density
Ωch2
Physical dark matter density
Ωb
Baryon density
Ωc
Dark matter density
ΩΛ
Dark energy density
ΔR2
, k0 =
0.002Mpc−1
Curvature fluctuation
amplitude
σ8
Fluctuation amplitude at 8h
−1 Mpc
ns
Scalar spectral index
z*
Redshift at decoupling
t*
years
Age at decoupling
τ
Reionization optical depth
zreion
Redshift of reionization
The "physical baryon density"
Ωbh2 differs from the "baryon
density" Ωb in that the baryon
density gives the fraction of
the critical density made up of
baryons (the critical density is
the total density of matter/
energy needed for the
universe to be spatially flat,
with measurements indicating
that the actual total density
Ω tot is very close if not equal
to this value, see below), while
the physical baryon density is
equal to the baryon density
multiplied by the square of the
reduced Hubble constant h,[7]
where h is related to the
Hubble constant H 0 by the
equation H0 = 100 h (km/s)/
Mpc.[8] Likewise for the
difference between "physical
dark matter density" and
"dark matter density".
Extended models
Possible extensions of the
simplest ΛCDM model are to
allow quintessence rather than
a cosmological constant. In this
case, the equation of state of
dark energy is allowed to
differ from −1. Cosmic
inflation predicts tensor
fluctuations ( gravitational
waves). Their amplitude is
parameterized by the tensor-
to-scalar ratio, which is
determined by the energy
scale of inflation. Other
modifications allow for spatial
curvature (Ω tot may be
different from 1), hot dark
matter in the form of
neutrinos, or a running
spectral index, which are
generally viewed as
inconsistent with cosmic
inflation.
Allowing these parameters will
generally increase the errors
in the parameters quoted
above, and may also shift the
observed values somewhat.
Parameter
Value
Description
Ωtot
Total density
w
Equation of state
r
< 0.24, k0 = 0.002Mpc&#8722;1
(2&#963;)
Tensor-to-scalar ratio
d ns / d ln k
, k0 =
0.002Mpc&#8722;1
Running of the spectral index
&#937;vh2
< 0.0062
Physical neutrino density
&#931;m&#957;
< 0.58 eV (2&#963;)
Neutrino mass
 

Zagazaga

JF-Expert Member
Mar 2, 2011
564
500
duuuuuu..... imagine ndo pepa hilo....lazima utoke na yai. nimesoma kufika mwisho sikumbuki nianzia wapi. mwe...
 

Mama Mdogo

JF-Expert Member
Nov 21, 2007
2,952
2,000
Haya ndiyo matatizo ya cut and paste, hata huyo aliyeleta mda (Nzowa Godat) huenda hata hajui kipi ni kipi. Haya yetu macho na masikio, haya mambo ebu tuwaachie hao ma-astro physcists waliokubuhu, yaani, Carl Sagan, Edwine Hubble, Stephen Hawking, Tadashi Nakajima, Albert Einstein, Isaac Newton etc.
 

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