The Physics That I Don't Understand, queries seeking replies Options

[kallubhai4u]

hi nature, really good to find u in this topic. thnx alot for making these hi-fi physics clearer to all of us. plz post some more details on Friedman's model. it'll really help all of us.
bye!!!

[kallubhai4u]

hi

these r the answers( which i found on http://forum.physorg.com/index.php?showtopic=2963...u can read it too, no registering required) to the questions shivani had asked...her questions being:-

1.IS it correct to treat time the same way as we treat x/y/z ?

2.What is the relationship between time and memories/events. Whenever we talk of going to a particular time, it is because we wish to go back to a particular event

3.Is microwave radiation (observed by Penzias & Wilson as well as COBE) the only experimental evidence for Big Bang ?

ANSWERS:-

(1) No. There is a term used in the Lorentz transformations from one frame of reference to another. One frame might be attached to Earth, the other to a muon traveling at 99.999 percent of the speed of light. This factor is the square root of x^2 +y^2 +z^2 - c^2* T^2. Notice that the time factor is subtracted, not added. And the whole thing is under the radical of a square root. Thus, time by itself must be an imaginary number.

(2) Our concept of time arises becauses of memories of the past and expectations about the future. If we had no memories or expectations we would never have invented time.

(3) No, there is all kinds of evidence, beginning with Hubble's observation that all galaxies outside the local group are moving apart, and the further away, the faster they are moving. There are also the quantities of certain rare isotopes not created in stars, such as deuterium and Helium 3. These are what one would expect if all matter was once hot enough and dense enough to turn a quarter of the matter present from hydrogen to helium. Of course, the Big Bang itself is a complete mystery. Assuming it happened, we can understand most things that happened after about one second. But why there is something rather than nothing is a complete mystery.

1.IS it correct to treat time the same way as we treat x/y/z ?





No it is not correct to treat Time the same way as xyz. This Time is another dimension or a 4th dimension stuff is a left over from how the common man popularized the mathematical concept of time in mathematical equations. Somewhere in the 18th century, mathematicians started to refer to time as being on an axis 90° rotated from the x-y-z axes. Therefore the 4th dimension. It is like projecting a sphere on a sheet of paper so only a circle is visible. If you add movement to that sphere, you will see an expanding and then shrinking circle.

The same way you can imagine a human life as a 4 dimensional object that moves through out 3 dimensional space, aging as it moves.

But all those examples do not do justice to the complex thing that time is. Time and space (xyz) are linked however but not in the way that up/down and left/right are linked.




2.What is the relationship between time and memories/events. Whenever we talk of going to a particular time, it is because we wish to go back to a particular event




Time is used to order memories and events in a (chrono)logical order. when talking about going back in time, it is indeed meant as going back to an event that has already happened. Real time travel is not possible, even though mathematics might show otherwise and rotating black holes, relativity, worm holes and quantum foam might indicate otherwise. We always look at what has already happened, and will always 'move' toward the future. When we start talking about multiple dimensions however, we can do allot though, but that is as outsider.




3.Is microwave radiation (observed by Penzias & Wilson as well as COBE) the only experimental evidence for Big Bang ?




No, it is just one of the many observed indications that support the big bang theory. The speed of the far away galaxies is used as another. If you look far away to an object in the galaxy, you are in fact looking at the light that was emitted by that object millions to billions of years ago. The movement, as in speed of objects further away, as measured with Doppler, was higher, but slows down if you look at closer objects. This would indicate that the universe is slowing down its movement in time. calculations lead to one original point where it all started, therefore the Big Bang. However, even this theory has some unaccounted points and inconsistencies, and more is known every year and the Big Bang theory is adjusted and revised all the time with more details.

QUOTE

[bibhas]

My newfound understanding of the basic tenets of String theory has raised the following questions in my head:

1. Hithesh mentioned in an earlier post that String theory addresses the Universe in its "Pre-Big Bang" state. How does it do so, and more importantly, what is its description of the 'Pre-Big Bang" Universe ?

2. On a more general note, what is the model of the Universe according to String Theory ? Does it agree with the "no boundary" condition ?

Bibhas