# danny8522003

Senior Members

320

1. ## Locating the position of the BIg Bang

So what's your theory on the beginning of the universe then EL?
2. ## Singularities

But if m=dv then when trying to find m we get m=inf.*0. Anything multiplied by 0 is 0 so surely if the mass would be 0 when you do it backwards? So v must be >0 for the formula to work, but if it is >0 then we end up with infinite mass which im sure isnt allowed.
3. ## black hole+white hole

Upon further thought ... much like a matter-antimatter collision where the two particles are anihilated and are turned into energy (e=mc^2), would a collision between a black hole and a white hole not result in the same sort of effect? For example: If a 10kg black hole collided with a -5kg white hole, a 5kg black hole would result but according to Conservation of Energy the mass has to go somewhere. In other words 5kg would be turned into energy and released according to e=mc^2. Goes to find calculator... That would mean 4.5x10^17 joules of energy would be released, and that's just for 5kg. This would never occur the other way round (i.e. the white hole could not be more massive than the black hole because they would never meet, as explained earlier). In addition, if you think about spacetime as a flat sheet with a black hole as a depression and a white hole as a "hill" then superposition applies creating a depression equivelent to a 5kg mass. Just an educated assumption, feel free to correct
4. ## The center of the universe

If you think of the universe as a 2D film (like the skin of a balloon) that has expanded into a sphere of 3Ds, you will realise that without escaping our universe you could never locate the centre of this sphere. What would be the point in doing so anyway? We could never "point" to the centre of the universe or even reach it so IMO it would be useless especially seeing as the sphere would be of a rediculously large size. You have to take into account that this sphere would also have to be 4D and it's surface 3D, creating a hypersphere. This discounts time as another dimension.
5. ## Little help?

The Big Bang did not happen at a single point in the universe, it happened everywhere in the universe at once. Therefore, there is no way we can pinpoint the location of the Big Bang relative to this universe. The only way we could even begin to imagine where it took place would be to view the universe from the outside of it. Needless to say that would be impossible.

7. ## Book Suggestions

I liked "Black Holes, Wormholes and Time Machines" by Jim Al-Khalili. It explains everything in a thorough yet light-hearted manner that is easy to understand.
8. ## Fire or Ice?

Evidence at the moment would suggest that the universe is still expanding and doesnt look like it will slow down (in fact it is still getting faster), this can be seen because of the Red Shift of all but one of thr galaxies around us. If this is the case and the universe continues to expand, the matter and energy will become less dense and the universe will infact end in a big freeze. (Well technically it wont end in this case)
9. ## black hole+white hole

Surely is the white hole is more massive then it would repel the black hole with greater force than the black hole's "pull" on it, therefore they would part. If the black hole was more massive then it could "pull" the white hole towards with greater force than the repulsive effect of the white hole, hence whn they collide a smaller black hole would be formed. Your quite right in saying small black holes can evaporate and this is due to Hawking Radiation, explained in a link here.
10. ## Dispelling infinite universes

I believe a universe in a shape you are describing is called a hypersphere (a 4D sphere), not that you could even begin to imagine what one looked like unless you do away with one of the spacial dimensions in your mind.
11. ## A Planet Changeing it's Orbit

I wouldnt have thought the gravity of the moon would be strong enough to prevent the Earth from colliding with the Sun. If you consider the mass of the Moon and that of the Sun, there is a big different meaning the gravitational force of the Moon would be negligible. In my opinion, the moon leaving the Earths orbit would just result in a change in the Earth axil rotation and it's wobble, as well as the tides obviously...
12. ## Dispelling infinite universes

I had that same revelation, i hate thinking of something only to find someone else thought of it first .. nevermind. I understand the point your making, but why does the rate of expansion need to be infinite? The way i see it, every decision spawns a new universe seperate to our own, like taking a turn in a road. Each of these universes is completely independant of each other (unless considering time travel paradoxes, but that's seperate) and therefore the rate of expansion for each universe would be independant of the other universes. I.e. just because this universe is expanding at a certain rate, what's to say a parallel one isnt contracting because of a different quantum "choice" made earlier in time?
13. ## Question about Inflation

I read in a book titled "Blackholes, Wormholes and Time Machines" that the rate of expansion is due to a critical amount called omega. I guess flutuations in this value caused the rate of expansion to fluctuate after the big bang. This number is related to the relative density of the universe and also dictates whether it is negatively curved and open or positively curved and closed.
14. ## Singularities

Ive read a lot about black holes and singularities both in books and on the net and there has always been one thing that puzzles me. If mass = density x volume and the density is said to be infiniate, then surely the mass is infinite unless the volume = 0. If it is 0 then the mass would be 0 and space-time would not be warped to form the blackhole. A factor i have thought of is that the singularity may not have any dimensions, if this is the case then it would exhibit 0 volume but again ow could it have mass? Also i wondered whether anyone has thought that maybe the hidden mass in the Universe known as dark matter maybe just a black hole or a series of them? Mainly because we can be unsure of how many of these holes exist and whether it is enough to prevet infinite expansion.
15. ## The Official "Introduce Yourself" Thread

Hi, another new member. Im very interested in Astrophysics and Cosmology, which unfortunately isnt covered in the A-Levels im taking at the moment , so i thought id come and gain some insight here .
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