# Thread: Is the universe really..

1. i have learned that the universe is expanding at very fast rate because of the observation that the galaxy are getting further from our galaxy and in that case the unverse must be finite ,to take any reference size and if its finite what can be its size

2.

3. I think currently the observable universe is considered to be 93 billion light years in diameter. Although the BB occured 13.7 billion years ago, it has been expanding ever since, so it's current diameter is not 13.7 x 2 = 27.4 billion light years wide, as we might assume. This is because spacetime itself has been expanding. So although a photon of light may have traveled for 13 billion years to reach us from an early galaxy, the distance between that galaxy and us is greater than that now due to the expansion of the space between that galaxy and us.

It's as if you marked 1 inch on a rubber band. A little man walking on the rubber at 1 inch per hour would have traveled that 1 inch in one hour. Now you streach the rubberband and your original 1 inch marking now measures 3 inches. The little man now has traveled 3 inches in that one hour. His walking speed has remained the same, but the streaching of the rubber has carried him a longer distance.

We must remember this would be the diameter only of the observable universe. Due to the finite age of the universe, light from a galaxy farther away from us than 93 billion light years (taking into account of the expansion of the universe) would not have had enough time to reach us. The size of the observable universe may be only a tiny fraction of the size of the entire universe.

4. To StarMountainKid,

There is an estimation that size of the universe is 93 billion light years as you have written but how can it be estimated or with what reference it is estimated.If estimated with any reference then what is beyond that or what type boundary does it have.

If the galaxy is going farther can't we assume that galaxy can have certain path it has to revolve,why do we assume that the universe is expanding.

And i didn't exactly get what do you mean by space time can you please explain and 2nd paragraph.

5. newspaper,
I think the 93 billion light year diameter of the observable universe is estimated by taking the age of the universe, 13.7 billion years, and calculating how much it has expanded in that period of time.

The observable universe is like a sphere 93 billion light years in diameter with the Earth at the sphere's center. The sphere's radius would be 46.5 billion lights years, so the farthest we can see is 46.5 light years in any direction. The light from galaxies farther away than that has not had enought time to reach us.

The universe is expanding because it began to expand at the instant of the Big Bang, its creation, and that expansion continues today. The Big Bang was like an explosion in a sense. Evidence of this is the fact that when light is recieved from a source that is moving away from us, it's wavelength is shifted toward the red end of the spectrum. When we observe galaxies far away, their light is redder than expected, so they must be moving away from us due to the expansion of the universe.

Spacetime is the concept Albert Einstein came up with in his theories of Relativity. Spacetime has four dimensions. The three dimensions of space and one dimension of time. Space and time cannot be seperated and must be considered as one construct--spacetime. This is because, for example, when you are at some point in space you must also be there at some moment in time. When you tell your friend you will meet him at the corner of 5th and Main St., you must also tell him what time you will be there. So to have a complete coordinate system, we must specify not only where a point is in space, but when it is there.

As for my 2nd paragraph, when we consider light travelling great distances in space we must also consider that the space in which it is travelling is expanding. If a photon of light leaves one galaxy and travels to another galaxy 10 million light years away, because the space between the galaxies is expanding, during that 10 million years of photon travel the other galaxy has moved farther away from the 1st galaxy. So although the photon has travelled for 10 million years and has reached the other galaxy, the distance traveled will have been more than 10 million light years.

It's a little hard to picture at first because we have to consider two things happening at the same time. The photon travelling and the expanding space in which it is travelling.

The expansion of space between the galaxies is like the streaching of the rubber band. Space is being streached like the rubber band is being steached. Hope some of this helps.

6. Starmountainkid,

I have little idea about big bang.But i do not know what needed big bang to occur and what is its process. If possible can you please explain.

Can we say that Galaxy moving further means unverse is expanding, what evidence is there to support.I got the concept about the shifting of wavelength,but this only shows the galaxy going further, isn't it .It may have been that unverse is infinite and just that galaxy is going further.

It may be that i do not know the precise definition of the expanding unverse. I view the expanding universe as the volume of the space of the universe .And what's your view.

And for the spacetime ,I got the concept, It was a great explanation and thanks.

7. newspaper, I would agree with you that the expansion of the universe is the volume of space expanding. The light from all distant galaxies is red-shifted, so if every galaxy is moving away from us we presume the entire universe is expanding.

As to the cause of the BB, string theory and M-theory have an explanation for it. In string theory, tiny vibrating strings of energy are thought to be the basis for the elementary particles and the four fundamental forces. In string and M-theory these strings (except for strings that are responsible for gravity) are attatched to membranes or branes which exist in a higher dimensional reality. Our universe resides on a brane. A brane may be like a sheet of paper with these vibrating strings attatched to it. These branes drift around and sometimes collide with each other. When they bumb into each other energy is released and a new universe is created--a Big Bang.

The strings that are responsible for gravity are closed loops so they cannot attatch themselves to the branes. They drift around among the brains. The force of gravity is very week compared to the other three forces because these closed-loop strings are not attatched to the branes. This is my simple understanding of the subject.

8. I had tough time understanding these theories.

Do you mean that these strings make up the proton and neutron?
And one more thing i could not view strings.
I could not understand these particular sentences

(In string theory, tiny vibrating strings of energy are thought to be the basis for the elementary particles and the four fundamental forces. In string and M-theory these strings (except for strings that are responsible for gravity) are attatched to (membranes) or (branes) which exist in a higher dimensional reality. )

9. newspaper,
You can google search 'string theory' and 'M-theory'. Also you can watch the PBS NOVA television program The Elegant Universe' online here:

http://www.pbs.org/wgbh/nova/elegant/program.html

This tv program is from the book, 'The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory' by Brian Green. Perhaps you can purchase the book.

The fundamental particles are photons, electrons, protons, neutrons, etc. These particles are composed of smaller particles called quarks. (You may want to search 'quark' on the internet). String theory states that these quarks on a more fundamental level are created by small strings of vibrating energy. Like tiny vibrating guitar strings. The frequency at which these strings vibrate determine what particle it creates.

These strings are really small. Anyway, stings come in two types. Open strings which have two ends, and closed strings like loops. The two ends of open strings are attatched to a 'brane' or membrane which is a higher dimensional object, but we can imagine it like a sheet of paper. The open ends of strings are 'glued' to the paper. Since our universe existes on one of these brains, the stings are attatched to our universe on the brane.

The open strings that are attatched to our universe on the brane create the fundamental particles and three of the four fundamental forces, electromagnetism, the strong force and the weak force. The closed strings (loops) creat gravity. Since they are not attatched to the brain they are free to move around, and it's thought that this is why gravity is the weakest of the forces.

String theory is not proved to be a correct theory. Hope this helps and that I am accurate in what I have said.

10. Hi guys---

Hopefully I won't obfuscate the discussion, but if you have any more detailed questions I can answer them. I have been working in strings for a few years.

11. Hi Ben,
Maybe you can explain exactly how a string can create a particle. This thread seems to have morphed into string theory, for the moment anyway.

12. thanks ,for the site StarMOuntainKid

Hi Ben,
nice to see you here in this discussion.
I was wondering to know the history behind the development of the string theory and ahh... also about why scientist would think this string exist.

13. it is impossible to say for any human

i would guess the universe would be infinite, there is no matter so there are no bounds to the lengths,

and even matter in space without gravity is in perpetual motion, and i think the borders would be kind of like that, without an enegy to counteract its expansion it shall continue to expand

14. There's another possibility.

It's the "red-shift effect" factor.

Basically, generally it is accepted that the "red-shift" effect is evidence of the expanding universe.

We actually don't know if the red-shift effect is a distortion ITSELF of QUANTA reaching this solar system in an otherwise steadY-state Universe.

It is for that LACK of reasoning the scientific community provides that I am not a "believer" in the "expanding Universe" theory.

I mean, we don't know whether or not space with "less" concentration of mass, like the space between star systems, actually stretches the wavelength of QUANTA alone, creating a type of red-shifted effect of light, and that the so-called "dark-matter" isn't actually a fetaure related to that red-shifting of light in an otherwise steady state Universe.

Dark matter is a concet that tries to explain the effect on QUANTA by what appears to be empty-space (yet no one is brave enough to join the dots).

........we "don't know".........until we actually go out there.

15. Originally Posted by streamSystems
There's another possibility.

It's the "red-shift effect" factor.

Basically, generally it is accepted that the "red-shift" effect is evidence of the expanding universe.

We actually don't know if the red-shift effect is a distortion ITSELF of QUANTA reaching this solar system in an otherwise steadY-state Universe.
Red shift is where the object is speeding away from the observer, so any light that is given off is more spread out because of the velocity of the object. The greater the velocity away from the observer the greater the shift towards the red end of the spectrum
e.g, stationary object ............................
moving object . . . . . . . . . . . . . .
It's the Doppler shift with light

16. Yes.

I agree.

Yet my point was, "what if space is more stretched creating the "effect" of a red-shift".

Now, for something really difficult, tie that concept in with the little understiood "dark matter" idea.

17. Originally Posted by streamSystems
Yes.

I agree.

Yet my point was, "what if space is more stretched creating the "effect" of a red-shift".

Now, for something really difficult, tie that concept in with the little understiood "dark matter" idea.
I am hardly in the position to explain dark matter (too stupid in other words) I will have a read

18. Originally Posted by StarMountainKid
newspaper,
You can google search 'string theory' and 'M-theory'. Also you can watch the PBS NOVA television program The Elegant Universe' online here:

http://www.pbs.org/wgbh/nova/elegant/program.html

.
i saw that progam...i liked it, they make it really easy to understadn the string theory..i don't know if i beleiev it though..

19. Very good observation.

What if the agency or person with the BEST "discovery video" of the Universe actually should be awarded the "most believeable theory of space-time" award of the year award..........in the future, of course.

Would we believe it..........must we.............

OK, do we believe what is happening in Iraq?

What should be happening?

Should a theory of space-time incorporate what the Universe wants or what we want?

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