Comments on: Telescope Trick Reveals the Ghostly Glow Left by a Dead Star

By: Albert Bakker

Albert Bakker — Mon, 13 Jul 2009 05:25:02 +0000

Yes the number 3 appears quite frequently, but the zero’s are more important. The nuclei of hydrogen, helium and lithium are formed about 3 minutes after the Big Bang, but only after 300.000 years free electrons are (sufficiently) caught by these nuclei to form atoms, allowing photons to go about their merry ways; the universe slowly becomes transparent. And the 300.000.000 years figure is when for the first time stars and galaxies begin to form. And then about 2 billion years later these stars already violently commit suicide and release their fusion products to make it possible for a bunch of monkeys in a distant future to actually see where they came from. Isn’t it just beautiful?

By: Jason

Jason — Mon, 13 Jul 2009 00:10:25 +0000

Wasn’t it some 300 million years before matter condensed from the cooling universe? Hydrogen, Helium and Lithium were created at this time, not at the instant of the ‘Big Bang’ that started it all.

By: Albert Bakker

Albert Bakker — Sat, 11 Jul 2009 08:38:57 +0000

As I understand it so far. The misunderstanding causing all these different numbers is primarily in the word “now.” There is no global or universal “now.” There exists only a now on the centre of each lightcone, to which everything else inside of it is causally related.

In the current paradigm there are three separate horizons in our universe:

1. Light from any object further away than our universe is old. This is currently estimated to be about 13,7 billion years. This horizon is expanding: we wil be able to see more in the future.
2. Light from any object further away than that object moves away from us with a speed greater than lightspeed due to expanding space between us. A photon emitted from beyond this horizon will forever have more distance to travel to us than it has covered. This horizon is contracting or rather said with time more and more matter will lie outside of it as seen from any point in the universe. The cosmological constant (dark energy) in this region will stay the same, so the expansion will accelerate: we will be able to see less in the future (at an increasing rate.)
3. The theoretical horizon of our universe (possibly in a “multiverse”) where our laws of physics are valid due to the inflation epoch. I have no idea how enormously big this is. But it is also not relevant since it extends way beyond any information that can ever reach us or anything that can ever affect us.

By: YouRang

YouRang — Fri, 10 Jul 2009 13:21:26 +0000

Strictly speaking the universe (multiverse) is an infinite distance across; it was right after creation also. What is 93 billion light years from us is that mass which we will ever be able to see. It will take an infinite length of time for us to catch a glimpse of it.

By: Jhem

Jhem — Fri, 10 Jul 2009 09:15:00 +0000

Well, because of the expansion of space any explosion made 11 billion years ago will have moved away from us during those 11 billion years, see the expasion of space:
http://en.wikipedia.org/wiki/Metric_expansion_of_space

And this is measureable with a technique called redshift:
http://en.wikipedia.org/wiki/Redshift

And wikipedia is probably not 100% correct a 100% of the time – just like any other textbook in the world.
This topic is actually not one of the more questionable topics [on wikipedia], as physics, like math, is rather emperically testable and stable (not saying there isnt any development in physics, just saying that our knowledge about the world just doesnt change radically very sudden).
There are of course topics which are potentially more questionable, but we all have to make our own judgment when it comes to reading stuff on the web/newspaper/tv/conversations etc.
In the end its only our own critical behavier that will prevent us from low-quality-information overload.

By: Tejas

Tejas — Fri, 10 Jul 2009 03:40:43 +0000

such problems are not wikipedia solvable – if you can answer such a thing, you will be earning PhD for yourself!

By: John Cassady

John Cassady — Fri, 10 Jul 2009 03:30:12 +0000

Nick, you know that wikipedia isn’t 100% reliable, right?

By: Nick

Nick — Fri, 10 Jul 2009 03:03:55 +0000

It’s not a distance of 11 billion light-years. The universe is expanding. It’s light that’s 11 billion years old. Please see the wikipedia article on the size of the universe, which is actually about 93 billion light years across at this point. Even Nat Geo says that the supernovae is now about 18 billion light years distant from us – which isn’t that far away considering the universe’s radius (Ur) is about 46.5 light years across. So it’s less than halfway to the where the edge of the visible universe is currently theorized to reside.

It took 11 billion years for light to travel across an expanding distance between the origin and us. I’m not an astrophysicist, but I believe that means the supernovae was actually closer to us 11 billion years ago than 11 billion light-years, but I can’t figure out how much with casual wikipedia-ing. Maybe someone else has some insights?

However, as a relative measure, a supernovae that took place 11 billion years ago was definitely farther away than one that took place 9 billion years ago.