How did they come up with the age of the universe.?

Question

If the age comes from looking back at the Cosmos... then what about looking forward? Is that counted as well? What about the elapsed time?

If they measured the farthest star, and used that as the minium age, what about the farthest star in the other direction? Shouldn't that distance also be added to the age of the universe? If nothing travels farther than the speed of light, how can the universe expanded faster than the speed of light? So let's say the farthest star is 10 billion light years away (in one direction) and 10 billion in another, the minumn age is 20 billion years. But since the light took 10 billion years to reach us, we can not possibly know how long that same lightsource was out there before our eyes absorbed the light.

Answer 1

The Universe is expanding in all directions. you work out the speed at which the distance between the stars is increasing.

Then you simply deduct that figure until all of the points converge.

Alternately you can use the Biblical method of Ussher of counting back the dates of recorded events and the ages of the various people named and you hit a figure of 4004 B.C.

...... hmmmmm

Answer 2

When looking at galaxies, astronomers noted that the further away a galaxy was, the faster it seemed to move away from us.

Many found a steady rate: a link between the distance and the apparent recession speed (people like Hubble).

Another astronomer (a priest) proposed that if we imagined time going backwards, all these galaxies would have been at the same place at some time in the past. Meaning, the universe would have been contained in a "primeval atom".

Using all these ideas, astronomers calculated how far back in time one would have to go to get all the galaxies into that "atom". Hubble made the first serious calculation.

The modern calculations show that this must have been around 13 to 14 billion years ago.

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Separate from that, we know that light in the vacuum of space has a finite speed (this was known from the 1700s). Since Einstein, we know that this speed is the speed limit in the universe.

Therefore, any light from space that we see today cannot have left today (and even less tomorrow). So, every time we look towards space, we are looking "back in time".

We cannot look "forward" in time because that would mean seeing light before it was emitted.

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Putting the two ideas together (the universe has an age AND light has a speed limit), we conclude that there should be a limit to the distance we can see. And sure enough, the furthest thing we can see is the cosmological microwave background. This is how we perceive the light that existed in the universe when it became transparent (when it had cooled enough for neutral atoms to exist).

We cannot see anything further out than that distance in any direction, because we cannot see further back than that time.

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The elapsed time between when light was emitted from an object far away and when we actually see it usually means that the object is now much further away from us than what it appears (because the universe has continued to expand while the light was travelling from there to here).

Normally, distance to astronomical objects is listed as the perceived distance (the distance the light travelled). However, it is possible to find distance tables that add the correction for the expansion that took place in the meantime. It is called a "comoving distance" .

Answer 3

A good way to get an idea of the age of the universe is to start at time zero.
It was probably 100 million years before the first stars lit up.
They blew up in 10 million years.
Their debris traveled out ward for about 2 million years.
The solar system took about 4.5 billion years to reach the point we are at now.
We are in the outer arms of a galaxy that preceded us by about 1 billion years.
This makes the universe about 6 billion years in radius.
The universe can't be much bigger but it could be much older.
The farthest galaxies we see don't exist any more.
The information needed to estimate the actual age of the universe was destroyed when the farthest galaxies went out of existence.

Answer 4

Three different techniques are currently used to calculate the age of the Universe. [See also http://www.astro.ucla.edu/~wright/age.html.]

Velocity-distance relationships measured from galaxies
The Hubble constant, the value for the rate of expansion of the Universe can be used to estimate the time that has elapsed since the formation of the Universe at the Big Bang. This is estimated from the relationship 1/H0.
Recent improved measurement of the parameters Hubble's constant, the mass density of the universe, and the cosmological constant, yield an age for the universe of 13.4 ± 1.6 billion years, which is a billion years younger than other recent age estimates.
See: Lineweaver, CH, 1999. A Younger Age for the Universe, Science, 284, Number 5419, pp. 1503-1507.
Radioactive dating methods and models of galactic evolution
The ratio of the isotopes of the radioactive element Uranium when this heavy element was synthesised can be used to estimate the age of the Universe. Combining measurements of uranium isotope ratios with models of galactic evolution allows us to infer an age for the Universe of between 12 and 15 billion years.
Measurement of stellar age from uranium decay

Nature, 409, pp.691-692 (2001) © Macmillan Publishers Ltd.

R. CAYREL, V. HILL, T. C. BEERS, B. BARBUY, M. SPITE, F. SPITE, B. PLEZ, J. ANDERSEN, P. BONIFACIO, P. FRANÇOIS, P. MOLARO, B. NORDSTRÖM & F. PRIMAS

The ages of the oldest stars in the Galaxy indicate when star formation began, and provide a minimum age for the Universe. Radioactive dating of meteoritic material and stars relies on comparing the present abundance ratios of radioactive and stable nuclear species to the theoretically predicted ratios of their production. The radioisotope 232Th (half-life 14 Gyr) has been used to date Galactic stars, but it decays by only a factor of two over the lifetime of the Universe. 238U (half-life 4.5 Gyr) is in principle a more precise age indicator, but even its strongest spectral line, from singly ionized uranium at a wavelength of 385.957 nm, has previously not been detected in stars. Here we report a measurement of this line in the very metal-poor star CS31082-0018, a star which is strongly overabundant in its heavy elements. The derived uranium abundance, log(U/H) = -13.7 ± 0.14 ± 0.12 yields an age of 12.5 ± 3 Gyr, though this is still model dependent. The observation of this cosmochronometer gives the most direct age determination of the Galaxy. Also, with improved theoretical and laboratory data, it will provide a highly precise lower limit to the age of the Universe.

Models of stellar evolution
The luminosity of a star of a specified chemical composition is determined by the supply of hydrogen to its core. We can therefore infer the age of a star from its mass. The oldest stars calculated in this way are between 12 and 15 billion years old.
The three independent methods of dating all broadly agree, although the precision claimed for the first model is currently thought to be the best estimate for the age of the Universe.

Answer 5

Further to Raymond's answer, perhaps you should check out the Wikipedia entry for "Age of the Universe".

It describes how determining the parameters associated with the Lambda-CDM model of the Universe leads to the time elapsed since the epoch of the Big Bang.

An important passage (describing how the Wilkinson Microwave Anisotropy Probe produces an answer) is the following:

"This measurement is made by using the location of the first acoustic peak in the microwave background power spectrum to determine the size of the decoupling surface (size of universe at the time of recombination). The light travel time to this surface (depending on the geometry used) yields a reliable age for the universe. Assuming the validity of the models used to determine this age, the residual accuracy yields a margin of error near one percent."

Answer 6

they simply look to very distant stars and try to estimate its age. The distance will tell us the elapsed time between the event that happen in the star between our time. The image we see is delayed. For example, if a star measures 100 light years away from us, it means that the image of what happened on that star will be seen on our's after 100 years.

Answer 7

Simply this: they measure how far away stars are, and using the speed of light (since it is the limit) to find the minimum number of years old our universe is.

Answer 8

Don't know all about the scientific stuff....seems to me that if one has no starting point then there is no measure and if there is a starting point then that's the beginning of the measure but one then has to know what the starting point is.....confused?...you will be. How long is a piece of string?

Answer 9

approximately 4.6 5 billions years

Answer 10

thats a good question , because
if you think about what they are saying,
that what we see is looking back in time
then what we are seeing isn't really there anymore ?
and it may look totally different now, but we will not know for two more million years or whatever the case may be