# How to find the size of the universe?

• whozum
In summary, scientists have calculated the size and rate of expansion of the universe by using data from various sources. The radius of the observable universe is currently estimated to be 47 billion light-years.
whozum
How does one figure something like this out? As well as its rate of change, and such things?

Another question, I've heard velocities of stellar objects can be/are measured relative to the stars, how does this work if the stars themselves rae moving? Is it that their movement is so minute relative to the object that they can be considered stationary?

I wish we knew the topology of the universe. According to standard cosmology, the universe should be a closed system.

Check out this http://www.newscientist.com/article.ns?id=dn4250

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There is no way

whozum said:
How does one figure something like this out? As well as its rate of change, and such things?
There is no way to figure this out considering the universe has not been discoverd for its full extent and probably never will be...

There are some approximations out there,and I'm asing how those came about.

The universe has a very distinct, and finite size observationally.

Well I know this, do you have an answer to my question?

the universe is expanding and it is actually accelerating in its rate of expansion.
we can tell this from the red shift in the spectrum of galaxies as seen from Earth.
It is not of constant size.
love and peace,
and,
peace and love,
(kirk) kirk gregory czuhai
owner/ceo Heaven Sense
http://HeavenSense.ws

The observable universe is approximately 47 billion light-years in radius. The light from objects further than 47 billion light-years away has not yet had time to reach us.

- Warren

That's quite a radius for the observable universe. Then again I'm not all that surprised because it is the universe we are talking about. Warren, do you know how scientists arrived at that figure? I mean how did they calculate it?

misskitty:

Using instruments like WMAP, cosmologists can fit the universe around us to one of a number of candidate models. The models produce, among other data, the rate of expansion of space at each moment in time. You can use that function to determine the present-day radius.

- Warren

That is really cool. I hadn't heard about it. Would it be possible to predict the diameter of the universe based on that data? Might it be possible to predict the radius of the whole thing?

Thanks chroot. Its kind of an obvious way now that I think about it.

misskitty: Divide by two :)

Whozum, i know how to find the radius of the circle. I meant predicting the diameter of the entire universe.

can we use the formula of the gamma particle when desiontegrated from uranium to know the age of the universe?
because as i know it travels throughout space and nothing can stop it!?

A_I_ said:
can we use the formula of the gamma particle when desiontegrated from uranium to know the age of the universe?
because as i know it travels throughout space and nothing can stop it!?

This would assume that there was a noticable and large supply of uranium at the beginning of time. However, uranium is generally created in supernova explosions and, since there weren't any stars around at the beginning of time, there was no uranium either. As far as I know, even at the present time there is no strong source of uranium emission in space. A lot of the radiation we see from supernovae, however, is from the radioactive decay of titanium-44 and aluminum-26.

Also, it's not true that nothing can stop gamma-rays. In fact, the reason we can't observe them from the ground is that they're absorbed and scattered in the atmosphere.

whozum said:
How does one figure something like this out? As well as its rate of change, and such things?
.
The universe is infinite and cannot be measured or modeled.
This is why mathematicians do not like the infinite universe.
They cannot meaure it. Except in terms of the big bang that theoretically happened and is finite. Maths teachers can then work. :!)

SpaceTiger said:
This would assume that there was a noticable and large supply of uranium at the beginning of time. However, uranium is generally created in supernova explosions and, since there weren't any stars around at the beginning of time, there was no uranium either. As far as I know, even at the present time there is no strong source of uranium emission in space. A lot of the radiation we see from supernovae, however, is from the radioactive decay of titanium-44 and aluminum-26.

Also, it's not true that nothing can stop gamma-rays. In fact, the reason we can't observe them from the ground is that they're absorbed and scattered in the atmosphere.
PF readers may find http://www.eso.org/outreach/press-rel/pr-2001/pr-02-01.html of some interest (it's only indirectly related to what SpaceTiger said above) ... "They* measured for the first time the amount of the radioactive isotope Uranium-238 in a star that was born when the Milky Way, the galaxy in which we live, was still forming. It is the first measurement ever of uranium outside the Solar System"

*Roger Cayrel (P.I.), Francois Spite and Monique Spite (all Observatoire de Paris, France), Vanessa Hill and Francesca Primas (ESO), Johannes Andersen and Birgitta Nordström (Copenhagen and Lund Observatories, Denmark and Sweden), Timothy C. Beers (Michigan State Univ., USA), Piercarlo Bonifacio and Paolo Molaro (Trieste, Italy), Bertrand Plez (Montpellier, France), and Beatriz Barbuy (Univ. of Sao Paulo, Brazil).

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misskitty said:
That is really cool. I hadn't heard about it. Would it be possible to predict the diameter of the universe based on that data? Might it be possible to predict the radius of the whole thing?
Lots of details here - Ned Wright's Cosmology website (includes a calculator).

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Lot's of details is an understatement dear.

Kitty

## 1. How do scientists measure the size of the universe?

Scientists use a variety of methods to measure the size of the universe, including triangulation, redshift, and cosmic microwave background radiation. These methods involve observing and measuring the distances and movements of objects in the universe.

## 2. Can scientists accurately determine the exact size of the universe?

Due to the vastness and complexity of the universe, it is impossible for scientists to determine the exact size. However, through advanced technology and mathematical calculations, scientists have estimated the observable universe to be about 93 billion light-years in diameter.

## 3. How has our understanding of the size of the universe changed over time?

Throughout history, our understanding of the size of the universe has evolved as our technology and knowledge have improved. From ancient civilizations believing the Earth to be the center of the universe, to modern-day scientists using advanced telescopes and instruments to study the vastness of space.

## 4. Are there any theories or models that attempt to explain the size of the universe?

Yes, there are several theories and models that attempt to explain the size of the universe. Some of the most well-known include the Big Bang theory, which suggests that the universe began as a singularity and has been expanding ever since, and the inflationary model, which proposes that the universe experienced a rapid period of expansion shortly after the Big Bang.

## 5. Why is it important for scientists to study the size of the universe?

Studying the size of the universe allows scientists to better understand the origins, structure, and evolution of the universe. It also helps us gain insight into the fundamental laws of physics and the potential for other habitable planets or life forms beyond our own. Additionally, studying the size of the universe can lead to technological advancements and innovations that benefit our daily lives.

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