Originally Posted by Peter B

G'day! Love your avatar.

snippety snip...

What was the source of this information? Did you check it out for yourself, or are you assuming everything you've mentioned is correct?



So you say this object was visible to people who lived about 4000-5000 years ago? Just checking the numbers here.



Hmmmm. The Greek philosopher Plato was the cause of Atlantis. No one recorded the name before him, and although many people claim to have found it, there really is no evidence for it existing beyond Plato's description.



Reference please?



A brown dwarf would need to pass very close to the Earth to heat it up. They simply don't produce a lot of heat.



Well, we can do some calculations, thanks to the laws governing the motion of orbiting bodies developed by Johannes Kepler and Sir Isaac Newton. If the Sumerians recorded the passage of this brown dwarf 4000-5000 years ago, and it's due to return in 4 years (not 5, remember, it's already 2008), then it's already going to be really close - well within the orbits of the outer planets. So it's hardly going to be coming completely out of nowhere.



That's true. But the reasons we're blindsided by comets explain why we're not going to be blindsided by a brown dwarf. Comets are a lot smaller than brown dwarfs. Comet core < 100 kilometres across. Brown dwarf > 100,000 kilometres across. That alone is going to make them screamingly obvious in the sky. Secondly, comets are made of ice, and so very cold. Brown dwarfs are failed stars, but still generate some heat. That also is going to make them stand out in the sky.

Put simply, a brown dwarf already closer to the Sun than the outer planets is going to stand out like proverbials - it's larger than Jupiter, much brighter than Jupiter, not much further from the Sun than Jupiter, and it's moving across the sky. Virtually anyone pointing a telescope into the sky is going to spot that.



Reference please.



Putting my hand up.



What about someone in South America or southern Africa? Remember, the entire southern sky is visible from everywhere in the southern hemisphere.



Pardon? There's some embargo on selling them, is there?



How good do you think governments are at keeping secrets? Anyway, don't you think amateur astronomers might have spotted Brownie, given what Brownie's characteristics must be? Do you think they're all keeping the secret too?



It is.



Well, I might have a look, but if your source of information turns out to contain silly mistakes, prepare to be mocked.

One other point. The Solar System is about 4.5 billion years old. If Brownie orbits the Sun every 4000-5000 years, that means it would have passed through the Solar System about a million times. Something the size of Brownie would leave very obvious traces, such as in the orbits of the planets. Instead, the planets are behaving as though nothing serious has affected their orbits for the last few billion years.