# Modelling universe.

1. Aug 15, 2009

### Hippasos

If we were to model the universe can we calculate the gravitational information rate which a particle receives in a universe?

2. Aug 15, 2009

### nicksauce

Well, first one would have to define "gravitational information rate".

3. Aug 15, 2009

### Hippasos

Could it be defined like this:

Gravitation information rate = How much data is gathered when calculating the vector sum of the modeled particle (all attractions) in a given time in a modeled universe.

Would the order in which the particles affect each other become problem i.e. how could we handle the causality in our model in a proper way?

4. Aug 15, 2009

### Danger

Flat out simple answer is that it's impossible to model the universe, so it's an irrelevant question. No offense intended, but a lot of people don't realize that in order to model something, the facility has to be significantly larger than the item being modeled. So what such facility, readily available, is significantly larger than the universe? This is one of my reasons for being an Atheist, but that's beside the point.

5. Aug 15, 2009

### kuruman

I am not sure I understand the use of the term "facility" or, as a matter of fact, the statement itself. Could you elaborate? For example, if the "item" to be modeled is the solar system (a centuries old problem), what is the "facility"? Thanks.

6. Aug 15, 2009

### Danger

What I mean is that to perfectly model anything, you have to duplicate it life-size right down to the subatomic particles, and even virtual particles, involved it its structure. The facility (laboratory or factory or whatever) then obviously has to be large enough to house that model with some space left over. To model the universe, the facility therefore has to be larger than the universe itself.

7. Aug 15, 2009

### kuruman

I see.

8. Aug 15, 2009

### Hippasos

Danger none taken.

I should have made this a bit clearer. The reason I asked is not if I would like to actually model but to find out how the universe works.

9. Aug 15, 2009

### Naty1

First, off ignore anyone who claims you "you can't do that". That's not how science has ever progressed. Post #6, however, IS valuable because it explains obstacles which must be overcome.

Of course you can model anything you want mathematically. How well it matches the actual situation involved is another matter. That likely involves lots of trial and error, calculations,etc...not an easy task...

Likely there are such models around to start...surely NASA must use such for space travel, for example. The earth's orbit around the sun for example, likely has little to do with distant galaxies as gravity varies by the inverse square of distance....And likely you could include the effects of a few if necessary by approximating them as a single source. But nearby planets in our own solar system probably do have an effect.

For a particle, I wonder if cosmic microwave background radiation has an effect? Surely particles from our own sun have an effect that must be considered.

On the other hand, I did read about some abberations in planned trajectories of vehicles headed for Mars, I think...am unsure if those were ever sorted out...it would be interesting to know if dark energy and dark matter have any effect on our local orbit...perhaps such effects tend to cancel due to the overall uniformity of the cosmos???

Lots to consider....

10. Aug 15, 2009

### Danger

Ahhh... I see. Well, we all want that, and a few PF members pursue that information professionally. It's gonna take a while, though.

11. Aug 16, 2009

### cristo

Staff Emeritus
I presume by "model" he means model mathematically. That is certainly possible, and is what a lot of people try to do!