does space have an end?
how can they calculate the distance between pluto & earth?

The length of the universe and calculation of distance between planets are two different questions. Calculations can be measured by using the effect of parallax. New methods include using radio transmission to calculate distance by observing the time it takes for these signals to travel across space.

according to einstein and hawking space is finite. but at the moment the edge of space is still expending after the big bang. there is no sign of the expension stopping yet. even if it suddenly contract it will take BILLIONS of year for the gravitational force to pull everything back to pre big bang

so dont worry people. the fable end of the world armageddon scenario often seen in religious books is at least a few billion years away! haha

why care abt celestial stuff when we cant even manage 1 planet properly

Yes, indeed the universe is expanding since the day it was born...
Scientists measure distance between planets and stars by calculating the time it takes for light to travel across 1 star to another (or 1 planet to another). Thus, u'll normally see why they state that this star is 10 light years away - it means that it takes 10 years for the light to travel from the star to another star at the speed of 299 792 458 m/s....

This post has been edited by gstrapinuse: Aug 20 2009, 11:03 PM

err , u mean that the universe is expanding day by day ? i never knew that.. thx for the info..

if u subscribe Astro, i suggest u turn to Channel 555, History Channel. there's alot of good info about universe, especially the Secret of Universe documentary.

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Added on August 21, 2009, 7:40 amlike this one - http://www.history.com/content/universe

This post has been edited by mi-g: Aug 21 2009, 07:40 AM

So far that is the theory. There is no end of the universe as it continue expanding. May try to read astropyhsic, astronomy n etc books..

I think it's just the planets expanding outwards, right? Not the space itself, as space is infinite. If space was finite, would there be a wall to stop us from going further?

Well firstly we have defined space to be whatever's affected by the 'big bang', so we do suspect that space (which is contained within the Universe) is indeed finite, and very large, not infinite.

As to whether space has an end: An equivalent question in many of our minds would be whether we would be able to ever 'leave' space if it were finite. As of now, this is unknown, but doubtful.

well maybe we havent reached he limit yet.
i dont believe that anything has infinite values.

even light, the fastest thing in the known universe has a value.
i think that we just havent discovered or understood it just yet

its 15000000000x300000x365x24x60x60km in diameter and expanding, read an article about it. Beyond that it just darkness.

well darkness is just the absence of light right?
and even darkness needs "space" to be in.

its hard to prove something that is so far and so out of our grasp.

The sun's hydrogen fuel in the core will run out by then.

When dealing with infinite space of the universe, most of us could get confuses easily.

The curved surface of the Earth can be used as an analogy. The Earth's surface is finite in area, but unbounded (no boundary). A traveller will not meet any edge or boundary in whatever direction he goes.

Similarly space could be finite in volume, but without any edge or boundary. An astronaut could, in principle, pointing his rocket in one direction and would return to his starting point at the end.

The big bang theory suggests that all matters (planets, asteroids, galaxies) are moving apart from each others a.k.a expending universe.

While the matters are moving away from each others, so DOES the SPACES within them are expending (imagine the spaces are stretch in an expending universe). The matters is NOT expending in spaces that already there, but the SPACES are being stretch further when the matters expend.

Many of us often assume that universe space is infinite and the planets are moving away and filling up more spaces which is already there (like a boy moving two balls apart in a big room (where spaces already be there) which is NOT TRUE.

Universe is a hypersphere with finite volume without boundary. The volume (x, y,z, t) continues to expend (and one day may retract) as a result of the big bang explosion.

If you are interested to understand this more, please refer to Einstein's hyperspherical cosmos modeling.

Cheers.

Therefore space is something imaginary.

they are just THEORIES.

actually, the universe is not just expanding, it's accelerating. means it's going faster and faster by the minute. there might not even be a mass collapse. however, assuming the big bang theory is true, then what keeps the universe accelerating?

ah, that's the question isnt it?

which is why everybody is trying to find out what is dark energy (not to be confused with dark matter ).


i might disagree here. in most articles i read, it mentions specifically that the density of the universe is dropping as the result of the accelerating expansion. if as u said matter also expands, then there should be no way to measure the expansion because everything is relatively expanding, we might not even notice it!

space expands. matters dont. which is why in a couple of billion years, there wont be any stars visible in the sky bcoz the distance is increasing faster than the light could reach us.

and until proven wrong, we accept it to be true.

That is a good description and illustration of "Space" in 2 dimension.

However, how can "Space" be described and illustrated in 3 dimension?

BTW, there might just be enough "dark-matter" in space to encourage and influence a "closed universe"... (Otherwise, there is just simply not enough matter in the form of visible or bright matters in space to create a closed universe; the universe will continue expanding and become an "Opened Universe"... ) Think about a hollow sphere being inside out or outside in; which space will eventually become in 2 dimension; depending on the amount of matter influencing the outcome...

It will be the ultimate result of the battle between gravity and the "dark-force"... If the "dark-force" wins the battle; our university will continue expanding forever in eternity into everlasting emptiness, darkness, and coldness... If the universe has enough matter; the expansion will eventually come to a halt as gravity overcomes the dark-force, then the university will slowly retract back and end up in a big crunch as gravity work...

Currently, scientist already know that there is simply NOT enough visible matter in space to be able to influence a closed-universe. (Based on the ratio of visible matter alone in our universe suggest that the fate of our universe lies in everlasting expansion into everlasting emptiness and darkness - an opened universe... where the universe will slowly parish in cold dark emptiness...)

The only hope lies in the mysterious "dark-matters" of our universe... (Which will be the factor to ultimately determine the fate of our universe.)

One such form of "dark-matter" is of my uttermost interest: Black Holes... (But lots of mathematics involved. )

This post has been edited by Benjamin911: Aug 21 2009, 11:54 PM

Agreed with the forumers here.

Cosmology and theoretical sciences are started from the imagination plus some observation, measurement made. From there hypothesis were then postulated.

The beauty of sciences is it encourages questions, doubts and dare to be challenged. Nobody owns it, not even Einstein. Should someone discovers a better way of explaining the universe later, it would be rejoiced as we are one step closer to the truth.

Just to add, the reason why hypersphere is a better model:

1) It resolves the issues with hitting with a "wall" at the end of the spaces

2) It complements with General Relativity of space and time curvatures

3) It agrees with big bang discovery (In mid-1965, two pyhsicists in Bell Telephone Company discovered some mysterious radiation (white noise) from space. They revealed that it is a relic of the primeval heat, the last fading glow of the fiery birth of the universe. This discovery provides a solid evidence of a singularity explosion leading to the expension of the universe.

4) It overcomes the limitation Of Steady State theory (Hermann Bondi, Thomas Gold and Fred Hoyle)
- The universe is infinite in age (no start, no end, always there). To overcome the thermodynamics heat death, low entropy matters are postulated to be contineouly created within the universe.
- Unfortunately the discovery of cosmic background heat radiation in 1965 has nailed this postulate down into the coffin.

Although Steady State theory has been replaced, it remains an important idea that:

A) It demonstrates the logical possibility of a universe without creation nor creator is possible
B) An universe which will not heat death after infinite time has passed is also possible
C) All processes, the matters could be attributed to the natural mechanisms

Feel free to share your idea.

Cheers.

alright so the universe is infinite. if it is so, how possible it is for it to expand? when something is absolute, the state of it being changed is impossible. you cant increase nor decrease ∞.

so they say its expanding, therefore, if with a new-fangled advance device to measure the size of universe at the speed of light so we wont miss a unit in calculation, we should be able to estimate the size of universe by measuring the perimeter it has covered at a specific time before it expands further.

Not exactly true that the universe is infinite, it is at most near infinite.

That means it is so large that it is like infinity to we earthlings.

The problem is;

Ever since the occurrence of the big bang approximately around fifteen-billion years ago (if my memory serves me well); light rays from distant celestial objects only had that much limited time to travel and reach our perimeter of sight until today... That means, today we are only capable of seeing fifteen billion years back in time (back into the past) through the world's most powerful astronomical telescopes and detectors. We are limited; our "visible universe" from our respective point of sight today is only a radius of fifteen-billion light years, whereabouts light rays from objects further out than that are completely invisible to us since their light rays are still travelling to reach our point of sight!

We can never see the rest of the universe that is outside of our fifteen billion years timeline...

One light year equals the distance that the speed of light has achieved/covered in one year.

The "actual" universe is MUCH larger that we can ever imagine...

The worse is; celestial objects (stars, galaxies, planets etc...) located further away from us are also at the same time moving away from our point of sight faster than the celestial objects located nearer to us...

"Quasars" come to mind... (Being one of the most 'redshift' objects of our visible universe...)

This post has been edited by Benjamin911: Aug 22 2009, 02:30 PM

According to Einstein cosmos, universe is a hypersphere with finite volume without boundary.

Volumes mean matters, spaces and time. Due to the expansion, the matters are moving away from each others and the spaces between them are stretched, hence the volumes of the hypersphere is larger but still finite. Imagine a tennis ball (the hypersphere universe) expands become a basketball.

A finite (finite doesn't mean fix, it means contain) volumes can expand, this is the whole idea.

Just ask another question, can an infinite volumes expand further. This question is meaningless as infinite volumes mark the highest volumes imaginable. Just like what you have quoted.

Ever heard of Doppler Effect? Imagine your are driving a car and an ambulance (with siren on) from the opposite direction. The sound signal from the siren would be weak, stronger, strongest, weaker, weak as the ambulance is moving closer to you and then moving away.

Now replace your car with planet earth and the ambulance with a planet under observation, and sound to be replaced by light.

Distance from two planet could be estimated using the method. Cosmologists encountered that the distances between the planets are getting further, hence by looking backward, these planets were closer and at a point, there were together (singularity) before the explosion.

Don't have answer to your question though, on measuring the perimeter of the universe. However, aren't the extension of the distance between two planets signify the universe expansion already?

Cheers.

nice.rider: Small correction. The Doppler effect refers to the fact that the frequency of the incoming light (which is the case here for astronomical measurements) is increased if the body emitting it and us are moving towards each other [this is called blueshifting], and the frequency drops if the body emitting it and us are moving away from each other [this is called redshifting].

So yeah, your analogy would be to talk about a higher pitch when the ambulance comes towards you, and a lower pitch as it moves away from you

This post has been edited by bgeh: Aug 22 2009, 07:31 PM

Not exactly related, but here is a short video on the Ultra Deep Field
It also give a very brief information on redshift.

http://www.liveleak.com/view?i=00f_1250151235

Wow, that is a very happening video; especially if you really understand what is really going on, or understand what you are really seeing.

BTW, besides Dark Matter and Quasars, also look up Globular Clusters and Seyfert Galaxies...

This post has been edited by Benjamin911: Aug 23 2009, 12:00 PM