A question

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Nikita
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Post by Nikita » Fri Jul 18, 2008 6:14 pm

{{{giggle}}}
That would get her going! Better yet, we can make one!
And it's stuff like this that makes parenting so much fun!

startrak
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Post by startrak » Sat Jul 19, 2008 2:52 pm

I know, I know, Nikita. Sorry. But since I've gotten a computer and have access to all this astronomy stuff and being involved with Stardust I've been completely fascinated and excited.

I'll definitely look into the suggestions from you and John.

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Post by Nikita » Sat Jul 19, 2008 10:48 pm

No worries!
I don't know if you have it, but our library has a used book sale about every other month. It's a very cheap way to find stuff, but you do have to watch out for the age, as John pointed out.
I did pick up the "Official US Space Camp & US Space Academy Manual" called Throttle Up today. It looked awsome!
But, alas, nothing current on space theories.
From dust we come

bmendez
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Post by bmendez » Mon Jul 21, 2008 6:15 pm

Hi All,

Startrak, I checked out that article. One of the key parameters in determining the age of the Universe is the Hubble constant. It's the expansion rate of the Universe. Turns out that it is not constant in time, but it a constant in space at any given time. The age of the Universe depends on the Hubble constant, such that lower values give an older Universe, while higher values give a younger Universe (since with a faster expansion rate it would have less time to reach its current size).

One can measure the Hubble constant by measuring the distance to a galaxy and by measuring its cosmological redshift. Redshift is an easy measurement: it requires taking a spectrum of the galaxy and looking for typical spectral lines from common elements, like hydrogen, and comparing their measured wavelengths to their rest-frame wavelengths. Distance, however, is notoriously difficult to measure. My thesis work involved measuring distances to nearby galaxies using a technique called the Tip of the Red Giant Branch.

The study you read about in Space.com had the team from Ohio using a new technique to measure the distance to a nearby galaxy, M33. Most techniques are not direct, but need to be calibrated by observations of closer objects. This new technique of theirs used eclipsing binary stars to make direct measurements. In principle, such a technique could yield good results. Their measurement of the distance to M33 turned out to be closer than other measurements have yielded. Taken alone, that could mean a lower value of the Hubble constant, and hence an older age of the Universe.

But, there are lots of problems with measuring the Hubble constant with a single galaxy. M33 is part of the Local Group and gravitationally bound to the Milky Way and Andromeda galaxy. So it is not taking part in the Hubble expansion of the Universe, and its distance would have more to do with its motions within the Local Group (called peculiar motions). To actually measure the Hubble constant with their technique it would need to be applied to many galaxies all in different groups or clusters of galaxies.

I would need to read the actual paper published from this result, but my guess is that the Space.com article latched on too strongly to the bit about the Hubble constant. The paper probably only passingly mentions that if their lower value for the distance M33 were also applied to other galaxies that it would yield a lower Hubble constant.

But with only a single measurement, such a claim is really only a speculation meant to tantalize the reader.

As the astronomer who was interviewed to comment on the research has said, so many other lines of evidence have pointed to the current best value for the Hubble constant, that it seems unlikely to be so different in reality. Of course, in science, you can never say never.

Oh, and Nikita, you should tell your daughter that what's on the other side of the Universe is the same as what is on this side. That's actually a fundamental principle of modern cosmology, called the Cosmological Principle. The idea is that on large scales the Universe is the same everywhere. All modern models of the Universe are based on that assumption.

Cheers,
-Bryan
"I am made from the dust of the stars, and the oceans flow in my veins"
- RUSH

Nikita
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Post by Nikita » Mon Jul 21, 2008 7:01 pm

Thanks for the suggestion. I'll wait a while and tell her that. Right now, all I have to do is ask her what is beyond the universe and her eyes get big and she starts saying, "No! I can't take it!" It's just too much fun!
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startrak
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Post by startrak » Fri Jul 25, 2008 3:54 pm

Thank you, Bryan. I'm certain it will take me a long time to digest even bits and pieces of all your interesting information. Bet I'll be hearing those explosions in my head again.

Nikita
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Post by Nikita » Sat Jul 26, 2008 7:11 pm

It's a good thing we have so many brain cells!
It's when you stop getting those explosions that you begin to lose the wonder of it all....
What we have found is amazing, that we can understand it is, to me, the most amazing thing! (Well, that SOME of us can understand it. I'll be in the shallow end looking into the depths of it all.)
I won't stop trying though, these guys had extra schooling to learn what we are trying to learn on our own.
From dust we come

Jessica
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Re: A question

Post by Jessica » Mon Apr 12, 2010 5:48 pm

@ Nikita

I saw your comment about your libraries used book sales. Indiana is very lucky to have many monthly book sales (some libraries only do 1 sale a year).

My site http://www.booksaleamanger.com lists these sales for free for the non profits who run them so book lovers, such as your self, can easily find them. I hope that helps you (and other readers) find books they love to read at cheap prices.

fjgiie
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Re: A question

Post by fjgiie » Wed Apr 14, 2010 6:05 am

Is this a self-promotion or advertisement?         http://www.booksalemanager.com/

           fjgiie

DanZ
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Re: A question

Post by DanZ » Wed Apr 14, 2010 11:30 am

Yeah, I've been administrating a lot more these days. Must be the increase of traffic since Phase 3 started that brings them in.

Dan

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