Universe From Nothing

[Harryz]

http://www.youtube.com/watch?v=7ImvlS8PLIo

Thought I would share this, a lecture from Lawrence Krauss on the universe. I really recommend it.

 

[lame-o]

Wow. That was totally worth an hour of my life. I'm surprised I haven't heard more about this kind of stuff before though...

 

[Seppo]

Atheist propaganda... this guy is just some scientist dude who's guessing how things supposedly might have happened. his theory might seem plausible if it wasn't for the fact that the creation of the world is allready described in the holy bible, in great detail, and it's written by actual eye witnesses.

 

[David.Seth2]

Thanks for posting this. I thought his name looked familiar, and after a quick google, I found out that he wrote the book The Physics of Star Trek. I've read this book a couple of time. Not only is it a really good read, he also does a great job of explaining how all the stuff in Star Trek could theoretically work. Highly recommend it.

 

[No Limit]

That is a very cool lecture. I still dont really understand how they come up with the standard candle. Even though the star is exploding how are they able to calculate how bright it actually is?

I also have a hard time getting my mind around the idea of a flat universe. How can something that has up or down be flat?

 

[Harryz]

Thanks for posting this. I thought his name looked familiar, and after a quick google, I found out that he wrote the book The Physics of Star Trek. I've read this book a couple of time. Not only is it a really good read, he also does a great job of explaining how all the stuff in Star Trek could theoretically work. Highly recommend it.

He did mention something about Star Trek (may be in this lecture or some other one), wondering what he was talking about. Cheers, I'll definitely will be picking that one up.

 

[Shakermaker]

Awesome talk. I really enjoyed that, thanks for posting.

@No Limit

All supernovas burn with the same brightness, so they're the ideal standard candle.

And the Universe is mathematically flat, not physically.

 

[No Limit]

Thanks! Although that helps clear up some confusion it opens up new questions for me. How do we know they are all the same brightness? Does light have an absolute limit on how bright it can be? And how do we know that (if the explaination is simple enough to understand, I'm guessing it isn't)?

About it being flat mathematically, I'm not really sure what that means and this always has been one of the big things I dont understand when I hear or read that the universe is flat. Does our sun lay evenly with a sun a billion light years away? Looking up at the sky at night the answer seems to be no, and all the stars and galaxies are spread out above and below us.

 

[Shakermaker]

How do we know they are all the same brightness?

I am no physicist so I will let someone else explain:

One example of a standard candle is a type Ia supernova. Astronomers have reason to believe that the peak light output from such a supernova is always approximately equivalent to an absolute blue sensitive magnitude of -19.6. Thus, if we observe a type Ia supernova in a distant galaxy and measure the peak light output, we can use the inverse square law to infer its distance and therefore the distance of its parent galaxy.

Because type Ia supernovae are so bright, it is possible to see them at very large distances. Cepheid variables, which are supergiant stars, can be seen at distances out to about 10-20 Mpc; supernovae are about 14 magnitudes brighter than Cepheid variables, which means that they can be seen about 500 times further away. Thus, type 1a supernovae can measure distances out to around 1000 Mpc, which is a significant fraction of the radius of the known Universe.

Does light have an absolute limit on how bright it can be?
You have to think more in terms of energy than light. But I'd imagine a supernova that can be seen from another galaxy must be pretty bright.


And how do we know that (if the explaination is simple enough to understand, I'm guessing it isn't)?
As in all science you never know something for sure. But most of the evidence points towards it.


About it being flat mathematically, I'm not really sure what that means
The problem with describing the 'shape' of the universe is that time comes into the equation, so it has more than three dimensions. The mental image of the Universe that comes closest imo, is an infinite ribbon.

 

[AJ Rimmer]

That was excellent. Hugely interesting, thanks for posting it! Even though it kept me up an hour after I planned to go to bed.

 

[The Monkey]

Reminded me of this:

http://www.youtube.com/watch?v=BlpyGhABXRA

 

[jondy]

Going to watch the video in a half hour, sounds super-cool but I'm on a 512k line so no streaming

 

[Shakermaker]

It's a specific type of supernova, Ia, which explode with the same critical mass. Going to watch the video in a half hour, sounds super-cool but I'm on a 512k line so no streaming

Yes, you're right. I corrected that in the post after the one you quoted.

 

[jondy]

Yes, you're right. I corrected that in the post after the one you quoted.

haha oh dear! Sorry Shaker

 

[Tyguy]

i'm annoyed, i watched a half hour and fell asleep at my desk at work...and now i want to finish the other half but i can't keep my eyes open...

DAMN YOU SCIENCE!!!!

 

[CptStern]

Atheist propaganda... this guy is just some scientist dude who's guessing how things supposedly might have happened. his theory might seem plausible if it wasn't for the fact that the creation of the world is allready described in the holy bible, in great detail, and it's written by actual eye witnesses.

lol

we need more people to post stuff like this ..as bait for the real thing!!! then it's hammer time