The age of the universe can be estimated in three ways: the age of chemical elements, the age of oldest star clusters, and the age of oldest white dwarf stars. Measurements from the Hubble Space Telescope and Wilkinson Microwave Anisotropy Probe have estimated the age of the universe to be approximately 13.8 billion years. However, this estimation depends on the underlying cosmological model being correct. The discovery of dark energy in 1998 revealed that the expansion of the universe is accelerating, contrary to expectations, and dark energy remains one of the greatest unsolved mysteries in physics today.

1. AGE OF THE
UNIVERSE

2. There are at least 3 ways that the
age of the Universe can be
estimated:
The age of the chemical elements.
The age of the oldest star clusters.
The age of the oldest white dwarf
stars.

3. • The age of the Universe can also be
estimated from a cosmological model based on
the HUBBLE CONSTANT and the densities
of matter and dark energy. This model-
based age is currently 13.75 +/- 0.1 Gyr.
But this Web page will only deal with
actual age measurements, not estimates
from cosmological models. The actual age
measurements are consistent with the
model-based age which increases our
confidence in the Big Bang model.

5. 1650: James Ussher, Archbishop of Armagh and Primate of All
Ireland, correlates Holy Writ and Middle Eastern histories to
“correct” the date to October 23, 4004 BC

6. 1831: Charles Lyell uses fossils of marine
mollusks to estimate age as 2.4x108 years

7. 1760: Buffon uses cooling of Earth from its
molten state to estimate age as 7.5x104 years

8. • Current Jewish calendar would
“suggest” a date of creation about
Sep/Oct 3760 BCE
• 1905: Lord Rutherford uses
radioactive decay of rocks to
estimate age as > 109 years (later
refined to 4.3x109 years)

9. • . In 1915 Albert Einstein published the theory
of general relativity.[16] Based on Einstein's
theory, Mgr. Georges Lemaître's work
showed that the Universe cannot be static
and must be either expanding or contracting.
Einstein himself did not believe this result
and so he added what he called a
Cosmological Constant to his equations in an
unsuccessful attempt to produce a theory
consistent with a Steady State Universe.

10. The Age of the Universe
No gravity: v = Hor  to = r/v = Ho
-1
Newtonian gravity for a flat universe:
½ mv2 - GmM/r = 0  v = dr/dt = (2GM/r)½
so we can integrate r½adr = (2GM)½dt to get
to = 2/3 (r3/2GM)½ = 2/3 (r/v) = 2/3 Ho
-1

11. • The first direct observational
evidence that the Universe has a finite
age came from the observations of
astronomer Edwin Hubble published in
1929.Earlier in the 20th century, Hubble
and others resolved individual stars
within certain nebulae, thus
determining that they were galaxies,
similar to, but external to, our Milky
Way Galaxy.

12. • The first reasonably accurate
measurement of the rate of expansion
of the Universe, a numerical value now
known as the Hubble constant, was
made in 1958 by astronomer Allan
Sandage. His measured value for the
Hubble constant yielded the first good
estimate of the age of the Universe,
coming very close to the value range
generally accepted today.

13. NASA's Wilkinson Microwave Anisotropy Probe
(WMAP)
 project's nine-year data release in 2012 estimated the
age of the universe to be 1.3772±0.0059×1010 years
(13.772 billion years old, with an uncertainty of plus
or minus 59 million years).
 However, this age is based on the assumption that
the project's underlying model is correct; other
methods of estimating the age of the universe could
give different ages. Assuming an extra background of
relativistic particles, for example, can enlarge the
error bars of the WMAP constraint by one order of
magnitude.
 BASED ON THE LIGHT TIME TRAVEL.

14. • The discovery MICROWAVE COSMIC
BACKGROUND RADIATION announced in
1965 finally brought an effective end to the
remaining scientific uncertainty over the
expanding Universe. The space probe WMAP,
launched in 2001, produced data that
determines the Hubble Constant and the age
of the Universe independent of galaxy
distances, removing the largest source of
error.

15. This number represents the first accurate
"direct" measurement of the age of the
universe (other methods typically involve
HUBBLE’S LAW and age of the oldest stars in
globular clusters, etc.). It is possible to use
different methods for determining the same
parameter (in this case – the age of the
universe) and arrive at different answers with
no overlap in the "errors".

16. `

21. • In the early 1990's, one thing was
fairly certain about the expansion of the
Universe. It might have enough energy
density to stop its expansion and
recollapse, it might have so little energy
density that it would never stop
expanding, but gravity was certain to
slow the expansion as time went on.
Granted, the slowing had not been
observed, but, theoretically, the
Universe had to slow.

22. • Then came 1998 and the Hubble Space
Telescope (HST) observations of very distant
supernovae that showed that, a long time
ago, the Universe was actually expanding
more slowly than it is today. So the
expansion of the Universe has not been
slowing due to gravity, as everyone thought,
it has been accelerating. No one expected
this, no one knew how to explain it. But
something was causing it.

33. Eventually theorists came up with
three sorts of explanations. Maybe there is
something wrong with Einstein's theory of
gravity and a new theory could include
some kind of field that creates this cosmic
acceleration. Theorists still don't know
what the correct explanation is, but they
have given the solution a name. It is called
dark energy.

35. More is unknown than is known.
We know how much dark energy
there is because we know how it
affects the Universe's expansion.
Other than that, it is a complete
mystery. But it is an important
mystery. It turns out that roughly 70%
of the Universe is dark energy.

38. quantum theory of matter
• In this theory, "empty space" is actually full
of temporary ("virtual") particles that
continually form and then disappear. But
when physicists tried to calculate How much
energy this would give empty space, the
answer came out wrong - wrong by a lot.
• The number came out 10 times too big.
That's a 1 with 120 zeros after it. It's hard to
get an answer that bad. So the mystery
continues.

39. • Another explanation for dark energy is
that it is a new kind of dynamical
energy fluid or field, something that
fills all of space but something
whose effect on the expansion of
the Universe is the opposite of that
of matter and normal energy.

40. • A last possibility is that Einstein's
theory of gravity is not correct. That
would not only affect the expansion of
the Universe, but it would also affect
the way that normal matter in galaxies
and clusters of galaxies behaved. This
fact would provide a way to decide if
the solution to the dark energy problem
is a new gravity theory or not: we could
observe how galaxies come together in
clusters.

41. • AND FINALLY; the last thing that
we needed to decide between
dark energy possibilities –is that a
property of space, a new
dynamic fluid, or a new theory of
gravity - is more data, better
data.