Test Your Astronomy Knowledge!

[Mr Spinkles]

There are so many fascinating tidbits in my Astronomy book, and I'd like to share them with everyone. I don't know if this is true for everyone, but I had a lot of misconceptions about the nature and size of the cosmos. The universe is truly more complex and vast than we can comprehend: our imaginations struggle with concepts like expanding space and the beginning of time, and we find it impossible to truly grasp the bigness of numbers like "14 billion" (the approximate age in years of the universe).

Here's an example: True or false, the galaxies are traveling away from each other?

False!

Aside from local gravitational interactions, the galaxies are sitting motionless in space. However, the distance between the galaxies is increasing, because space itself is expanding. (Kind of hard to imagine, isn't it?) :help:

Okay here's another one: True or false, there are an infinite number of galaxies?

 

[No*s]

Okay here's another one: True or false, there are an infinite number of galaxies?

Great thread Mr_Spinkles. I'll keep watching it.

I don't know the answer to this, so I'll not guess (can we know the answer yet?).

 

[Circle_One]

Wow, this is a great thread.

Part of me says the answer to that has to be no, because I cannot comprehend there being an infinite number of galaxies, but part of me urges that I guess yes, there is an infinite number.

One thing about the universe that's always been incomprehensible to me is the idea that when we look up into the sky at the stars, we are looking back into the past because of how many light years it takes for the light of the stars to reach us on earth. That's always been absolutely mind-boggling to me.

 

[Scuba Pete]

What a nova idea!I am truly star struck that you would start such a heavenly thread. It sorta brings you down to earth, if you know what I mean. Which would be cool, since I obviously don't.

By definition, there are not an infinite number of galaxies, though we don't really have numbers that go that high.

 

[Scuba Pete]

BTW, why DO stars seem to twinkle and planets don't?

 

[Circle_One]

BTW, why DO stars seem to twinkle and planets don't?

Stars seem to twinkle firstly because, like the sun, they produce a light source of their own, whereas planets do not. It is also because they are much farther away than planets and so as we look at them, their light is shining through our earth's atmosphere from a farther vantage point than the planets do, which is why they sometimes seem to twinkle out. It is not that their light has "gone out", but mainly because as the light travelled through the atmosphere it was directed to another point at that exact time.

 

[Mr Spinkles]

True or false, there are an infinite number of galaxies?

True!

There are an infinite number of galaxies in the universe. The trouble is, the universe is not infinitely old, so the light from galaxies very far away hasn't reached us yet. As Circle One pointed out, when we look into space we are looking into the past, and the deeper in space we look, the further into the past we can see. Why, even now, as you look at your computer screen, you are seeing it as it existed a tiny fraction of a second ago! *brain explodes*

Circle One is also right about the twinkling of stars. Notice that the stars twinkle less during the cold winter months, when the atmosphere is less turbulent.

Okay here's another one: What causes a meteor shower?

 

[Scuba Pete]

When we pass through cosmic debris (Usually from a comet)! Though I have to admit to passing through some "cosmic debris" right here on this site!

BTW, the point that was missed about the stars... is that the apparent SOURCE of their light is so much smaller that we see the effects of the earth's convection currents more. The planets, being so much closer appear "bigger" and so are not as affected as much. BUT if you look closely, you can see them twinkle just a bit.

 

[Scuba Pete]

BTW, I don't buy the "infinite" galaxy thing! Just because we can't count them doesn't make them infinite (without beginning or end).

 

[Mr Spinkles]

BTW, I don't buy the "infinite" galaxy thing! Just because we can't count them doesn't make them infinite (without beginning or end).

It has nothing to do with our inability to count them, or your willingness to "buy it" NetDoc . We know there are an infinite number of galaxies because 1) Space cannot have an edge or a center 2) The big bang is happening everywhere (not just here) 3) Recent studies suggest that the geometry of space is flat and open (not curved and closed).

What produced a cluster of galaxies here produced a cluster of galaxies everywhere, NetDoc...and as it turns out, "everywhere" is infinite. That's how we know there are an infinite number of galaxies.

BTW-- You're absolutely right about the planets. They don't 'twinkle' per se, but they can appear hazy through a telescope. Some astronomers say that looking at objects through our atmosphere is like looking at something through 20 feet of water!

 

[painted wolf]

here is a basic question that has to do with astronomy and science in general. Surprizingly most people get this one wrong.

Why do we have seasons?

infinity is a tough thing to wrap the brain around.

wa:do

 

[Scuba Pete]

Precession.

 

[Mr Spinkles]

Because of the tilt of Earth's axis relative to its orbital plane.

 

[Scuba Pete]

That's what I said.

 

[HelpMe]

?*correction*?

as far as we can tell, space is infinite, but not galaxies(at least not any more than dogs are infinite).the number is very well beyond our comprehension, which is not to say it is actually infinite.the number can seem unbounded, but this cannot be known for sure, not from where we are, not definitely by any means.to a baby crawling on the ground, the earth seems infinite, and if it were to stay a baby crawling for a short lifespan, the earth would remain, in the baby's eyes, infinite(enough commas?).just because we cannot see the end of the universe does not mean it does not exist.(i am not saying i believe the universe has an end, i am meerly stating theoretical fact)

 

[painted wolf]

most people when asked will say that its because we are futher from the sun.. wich is actually wrong. In the northern hemisphere were are actually closest to the sun during winter, but thanks to the tilt we do not get any direct sun.

as for the infinite and finite nature of the univerce... when we find the edge of the univerce we will know it is finite. Untill then there is no proof of a finite univerce.

wa:do

 

[Scuba Pete]

Was that the comma Kohote?

BTW, I think I got a handle on "Billion" once. There is a sinkhole in Ocala Fl called "Hal Watts" 40 Fathom Grotto. It's @ 240' deep. When I hit the wall at 130' ft I was amazed at how someone had taken the time to glue circular knives all over the place. How rude I thought! At @ 115', enough of the narcosis wore off for me to recognise them as sand dollors stacked one on top of each other like cord wood. The entire wall consists of sand dollars, sea biscuits and urchins piled up on each other. I only saw the first 130 feet and the grotto was easily the width of a football field at this point. Simply unbelievable.

 

[HelpMe]

...Untill then there is no proof of a finite univerce...

as i tried to state, there is also no such thing as proof for an infinite universe.

 

[Mr Spinkles]

That's what I said.

For those who don't know, precession is the motion of the Earth's poles in a circular motion...it's a motion similar to the wobbling of a spinning top. The Earth precesses once every...hang on let me check...about every 26,000 years. (And no, it is not why the Earth has seasons .)

HelpMe-- "Proof" is something confined to mathematics and liquor. In science, evidence is what counts. The evidence strongly suggests that there are an infinite number of galaxies. If you like, I will gladly start a new thread in the debate forum in which you can present any evidence you have that suggests there are a finite number of galaxies.

In the meantime, I recommendthis book: http://www.amazon.com/exec/obidos/tg/detail/-/0534395376/qid=1103168636/sr=1-1/ref=sr_1_1/104-4787065-9112713?v=glance&s=books

Moving on...

Anyone know what causes a meteor shower?

 

[Circle_One]

Meteor showers are caused when the Earth's orbit takes it through large clouds of dust and debris left behind by comets who's icy surfaces have been melted by the sun.