The Universe. Whats out there?

**Chairman Mao** · 05-05-2010, 10:10 PM

Good read.

One thing I think most people need to realise is that time isn't a constant - Time is (minutely) slower on an aeroplane than on Earth - and has a close relationship with gravity. It is faster/slower viewed from two different points.

One day humans will master its manipulation.

That, given human's trackrecord, may well be a very bad day.

**dantilley** · 05-05-2010, 10:39 PM

This is good, it might take a while to load, but it's worth it. When loaded, either use the left or right cursor keys or gently drag the slider left / right at the bottom of the page to see how big or small everything we know about is. Has some quite nice ambient music in the background also.

http://primaxstudio.com/stuff/scale_of_universe.swf

**DrAndy** · 05-05-2010, 10:42 PM

Originally Posted by Takeovers

As I said before, the defense is not 100%, but it is probably much higher than 95%. So if the earth was hit 20 or more times more often with large asteroids, we would not be here.

I am sure there have been some asteroids that were captured by Jupiter before hitting the earth, nobody knows how many though

I am not sure where you get your figures from as there has been no analysis and could not be any. There is no defence, only chance. You could calculate probabilities though; asteroids passing close to Jupiter may well be captured but most asteroids would not be in the vicinity, they come from all angles, from all regions of space

so assuming Jupiters effective gravity covers about a quarter of a degree out of the 360 degrees surrounding earth, that may well reduce impacts by 1/1440, about 0.0007%

additionally, the gravity may well divert asteroids towards earth

so not very much defence really

Originally Posted by Takeovers

If an asteroid would miss Jupiter by a small margin without gravity at work, it will hit under the influence of gravity

as said above, the reverse is also true; an asteroid that will miss earth may be moved off course by Jupiters gravity and hit the earth

**Takeovers** · 05-05-2010, 10:44 PM

Originally Posted by hillbilly

A must read.

STEPHEN HAWKING: How to build a time machine | Mail Online

Yes, very interesting read.

Unfortunately or rather fortunately he says in one paragraph:

Any kind of time travel to the past through wormholes or any other method is probably impossible, otherwise paradoxes would occur. So sadly, it looks like time travel to the past is never going to happen. A disappointment for dinosaur hunters and a relief for historians.

**DrAndy** · 05-05-2010, 10:47 PM

I am travelling in time right now

whoooosh

**Overman** · 05-05-2010, 10:53 PM

Hawking changes his mind about the 'secrets of the universe' as often as his nappy.

Whichever way you look at it - he's full of shit.

Great thread though - such a shame humans will never survive long enough to even begin to comprehend what it's all about.

**StrontiumDog** · 05-05-2010, 11:04 PM

Here's some research from a few years back on this issue...

Jupiter: Friend Or Foe?

Jupiter: Friend Or Foe?

ScienceDaily (Aug. 25, 2007) — The traditional belief that Jupiter acts as a celestial shield, deflecting asteroids and comets away from the inner Solar System, has been challenged by the first in a series of studies evaluating the impact risk to the Earth posed by different groups of object.

On Friday 24th August at the European Planetary Science Congress in Potsdam, Dr Jonathan Horner presented a study of the impact hazard posed to Earth by the Centaurs, the parent population of the Jupiter Family of comets (JFCs). The results show that the presence of a Jupiter-like planet in the Solar System does not necessarily lead to a lower impact rate at the Earth.

Dr Horner, from the UK's Open University (OU), said, "The idea that a Jupiter-like planet plays an important role in lessening the impact risk on potentially habitable planets is a common belief but there has only really been one study done on this in the past, which looked at the hazard due to the Long Period Comets. We are carrying out an ongoing series of studies of the impact risks in planetary systems, starting off by looking at our own Solar System, since we know the most about it!"
The team at the OU developed a computer model that could track the paths of 100,000 Centaurs around the Solar System over 10 million years. The simulation was run five times: once with Jupiter at its current mass, once without a Jupiter, and then with planets of three-quarters, a half and a quarter the mass of Jupiter (for comparison, Saturn is about a third of the mass of Jupiter). The team found that the impact rate in a Solar System with a planet like our Jupiter is about comparable to the case where there is no Jupiter at all. However, when the mass of Jupiter was between these two extremes, the Earth suffered an increased number of impacts from the JFCs.

Dr Horner said, "We've found that if a planet about the mass of Saturn or a bit larger occupied Jupiter's place, then the number of impacts on Earth would increase. However if nothing was there at all, there wouldn't be any difference from our current impact rate. Rather than it being a clear cut case that Jupiter acts as a shield, it seems that Jupiter almost gives with one hand and takes away with the other!"
The study shows that if there is no giant planet present, the JFCs will not be diverted onto Earth-crossing orbits, so the impact rate at the Earth is low. A Saturn-mass planet would have the gravitational pull to inject objects onto Earth-crossing orbits, but would not be massive enough to easily eject objects from the Solar System. This means that there would be more objects on Earth-crossing orbits at any given time, and therefore more impacts.

However, a planet with Jupiter's vast mass can give objects the gravitational boost to eject them from the Solar System. Therefore, if Jupiter deflects JFCs to an Earth-crossing orbit, it may well later sweep them right out of the Solar System and off the collision course with the Earth.

The group is now assessing the impact risk posed to the Earth by the Asteroids and will go on to study the Long Period Comets, before examining the role of the position of Jupiter within our system.

Jupiter family of comets

The Jupiter Family of Comets (JFCs) are short period comets with an orbital period of less than 20 years. Their orbits are controlled by Jupiter and they are believed to originate from the Kuiper Belt, a vast population of small icy bodies that orbit just beyond Neptune. Famous JFCs include Comet 81P/Wild 2, which was encountered by the Stardust spacecraft in January 2004 and Comet Shoemaker Levy-9, which broke up and collided with Jupiter in July 1994.

**StrontiumDog** · 05-05-2010, 11:05 PM

Originally Posted by melvbot

Explanation:
Some spiral galaxies are seen almost sideways. NGC 3190, one such galaxy, is the largest member of the Hickson 44 Group, one of the nearer groups of galaxies to our own Local Group of galaxies.

Pictured above, finely textured dust lanes surround the brightly glowing center of this picturesque spiral. Gravitational tidal interactions with other members of its group have likely caused the spiral arms of NGC 3190 to appear asymmetric around the center, while the galactic disk also appears warped. NGC 3190 spans about 75,000 light years across and is visible with a small telescope toward the constellation of the Lion (Leo).

Taken by Hubble I think, I had Moon freak on the way to work again this morning. I just wish I had enough cash for a telescope.

Images like this are simply breathtaking, they awe me...and humble me....

Incredible. The beauty of the universe.

**DrAndy** · 05-05-2010, 11:09 PM

Originally Posted by Overman

Great thread though - such a shame humans will never survive long enough to even begin to comprehend what it's all about.

I don't think this thread is that difficult

Originally Posted by StrontiumDog

Dr Horner said, "We've found that if a planet about the mass of Saturn or a bit larger occupied Jupiter's place, then the number of impacts on Earth would increase. However if nothing was there at all, there wouldn't be any difference from our current impact rate. Rather than it being a clear cut case that Jupiter acts as a shield, it seems that Jupiter almost gives with one hand and takes away with the other!"

wot I sed to Takeover

**mud** · 06-05-2010, 03:56 PM

it's big out there.

**Overman** · 06-05-2010, 05:00 PM

Originally Posted by DrAndy

I don't think this thread is that difficult

Einstien compared himself trying to understand the universe to a chicken trying to understand him.

**Chairman Mao** · 06-05-2010, 07:47 PM

you gotta give it to Einstein, the lad had some good quotes.

**DrAndy** · 06-05-2010, 09:16 PM

Originally Posted by Overman

Originally Posted by DrAndy

I don't think this thread is that difficult

Einstien compared himself trying to understand the universe to a chicken trying to understand him.

sorry, I thought we were talking about this thread being understandable

now the universe, completely understandable except we don't have all the facts yet

**melvbot** · 17-05-2010, 01:58 AM

Explanation: Why is this giant crater on Mimas oddly colored? Mimas, one of the smaller round moons of Saturn, sports Herschel crater, one of the larger impact craters in the entire Solar System.

The robotic Cassini spacecraft now orbiting Saturn took the above image of Herschel crater in unprecedented detail while making a 10,000-kilometer record close pass by the icy world just over one month ago. Shown in contrast-enhanced false color, the above image includes color information from older Mimas images that together show more clearly that Herschel's landscape is colored slightly differently from more heavily cratered terrain nearby. The color difference could yield surface composition clues to the violent history of Mimas. An impact on Mimas much larger than the one that created the 130-kilometer Herschel would likely have destroyed the entire world.

Amazing detail on this photo.

**agudbuk** · 17-05-2010, 07:24 AM

Nothing here is relevant as we are all but figments of our own imagination.

Thread: The Universe. Whats out there?

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