If you squint at the Sun on a bright day you'll be seeing the light and feeling the warmth of it from eight minutes ago.
Since the apparent movement of the Sun is actually the movement of the World turning we can point at the Sun. If the Sun was moving around the World then we'd be pointing at the place that the Sun WAS eight minutes ago.
Okay, how can we know how far more distant stars and even galaxies are? For the closest ones we can use parallax.
If we take a picture of part of the night sky in June and map that on to a picture of that same part of the sky in December, very close stars will seem to move compared to distant stars.
It's like if your nose was our Sun, the Jnne picture was your left eye, the December picture was your right eye. If you hold up your finger to represent a close star and 'wink' back and forth, your finger seems to move relative to objects on the wall.
Astronomers can calculate how near close stars are by knowing the distance between the summer and winter pictures and how far the close star seems to shift compared to far background stars.
But the point I'm trying to make is that, just like the light from the Sun is eight minutes old when we see it, the light from a close star is a few years old when we see THAT!
If we're talking about the closest star, we're talking FOUR YEARS ago. We can't say that Alpha Centauri is four light-years away, we can only say that Alpha Centauri WAS four light-years away, four years ago!
So here's where I start scratching my head. If astronomers are acurately telling us that the light that comes from the farthest galaxies is about 13 billion years old then THAT doesn't tell us where they ARE NOW, it tells us where they were THEN!
I think that speeding galaxies might have 'moved' a bit in 13 billion years, don't you?
44 comments:
OK- you can call me a smart ass, but I'm not ... it's my husband.
"Think about it honey - it's an equation (vector) that uses speed, time, and direction. It's the same way we know where the moon is going to be tomorrow night and the same way that radars work ... by measuring where the target is now and comparing it to 1 second ago."
He's pretty gud at splainin' things to me.:-)
P.S. - I should say that he enjoyed that question. :-)
Hmm.. I'm thinking about it.(Ugh, arghh.. mmm,nuh.. agagagaga... (sigh). I think I 'got' it.
(flush)
DARN, I wasn't supposed to flush!)
I'm confused. Are the distant galaxies distances calculated to be 13 billion light-years away from light that is seen to be only, say, 5 to 7 billion years old coming through the telescopes?
He went to bed already and I'm not sure I understand your question.?
The way I understand it is ... we can take measurements every second, or every month, or year.
And compare the movement to a second ago, or a month ago, or a year ago.
It gives us direction and speed.
Then the astronomers do some mathy stuff to figure it all out.
I am further confused by the fact that the Andromeda galaxy is only like a couple of million light years away and is three degrees across the sky, but we can barely see a 'smudge'.
Seems to me that we'd be lucky to see a photon or two from a galaxy billions of light years away. (just saying)
If you were travelling north at 60 mph for 1 day --- where were you 2 hours ago?? Where will you be in 2 hours??
The light is constant ... it travels. If it disappears then the source was 'put out' at some earlier time .
If I were to start travelling north at 60 miles a hour(for a day) in two hours i would report being 120 miles away. Two hours ago, I was just starting out and in two hours I will be 240 miles away.
I don't understand the significence.
If we look at a distant galaxy and 'check' the red-shift it can tell us the speed of the galaxy compared to us. (the relative speed)
But we're moving too(compared to a third party(the Klingons?) looking on from their galaxy.
If the Klingons see a different red shift for us and that other galaxy, doesn't that mean they will come to different conclusions with THEIR calculations?
Pboy,
I was just thinking about that last week! I saw a documentary on the universe. The scientists had some really cool 3-D map (in globe form) of the universe it was constantly changing dependent on the data.
They were talking about all these things that are happening to the universe now, and using the same exact data to talk about what had happened and what will happen without even blinking an eye.
I ain't the brightest coin in the bunch, so I called up the old man and asked him to break it down for me. He loves cosmology (well physics and space). He told me my observation was legit.
Don't know if it makes you feel better to have a theist in your corner but there I be. Now spit in the bucket the bell's about to ring.
LOL.. spit in a bucket! Good one.
You're husband is a theist?
Well, he must not be a political theist. I can't imagine that you'd be able to NOT kill him if he was a political theist.
No wait, you said, "..there I be."
Hey, if you're a theist that's fine, I understand.
I don't understand theism, but I understand why someone would be a theist.
I took 'old man' to be oneblood's father. Hmmmm ...
I'd like to know what the observation is that you are referring to, oneblood?
LOL.. sorry Stacy, I was thinking so hard I didn't notice that oneblood had joined the conversation.
Sorry oneblood. Same goes for you though, dude, it's not the fact that you believe that bothers me, it's that 'easy insultedness' and certainty and wanting to 'MAKE' everyone (at least pretend to be) theists by force of law and such that a lot(it seems) of Christians(not you) DO do.
""Think about it honey - it's an equation (vector) that uses speed, time, and direction. It's the same way we know where the moon is going to be tomorrow night and the same way that radars work ... "
But what I'm saying by 'we don't know where that galaxy is', is really, we don't know WHEN that galaxy is because if the light is from 13 billion years ago NOW, the light being given off NOW won't reach us for 13 billion years PLUS the distance(which is equivalent to actual years it takes, right?).
These galaxies are seen to be moving at large fractions of light-speed!
Therefore, the galaxy ought to be like (say the galaxy was moving at 0.2 light speed) over 15 billion light years away!
Older than the universe!
Wow, that was funny.
Even funnier is the poly tics joke.
Stacy,
Mainly the observation about 13 billion year old data being current. Same one pboy made.
Cosmology is interesting but sometimes these guys act like their heads are in space.
Off topic.
In the Pokerstars Tournament page, I 'clicked on the info for an upcoming.
The info says that the Tourney starts in 49,606 days and 20 hours.
Also after this 150 years has passed the date will be back to Nevember the 8th. 2008 AGAIN!
Oh yea, and just to heap another thing on, how is it that astronomers think that the universe is accelerating?
How much energy WOULD it take to accelerate something as big as a galaxy and where is that energy coming from?
Conservation laws anyone?
How astronomers got to learn that the expansion of the universe is accelerating is pretty simple: they measured how far galaxies were from us, and it turned out that current galaxies are moving faster apart than than the old ones used to.
As to why? No one has a clue. (The reason is called "dark energy", but that doesn't mean anyone knows anything about it except for the most general of properties.)
So much for finding a GUT if they don't have a clue what's going on.
If anyone has been giving the impression that a successfully verified GUT or TOE is imminent, that person is probably crazily more optimistic than most scientists ...
(Might explain who has been stealing all of my own optimism. ;)
"(Might explain who has been stealing all of my own optimism. ;)"
I'll be reporting to CERN that I have found a source of dark energy! LOL
Ummm, ahhhh, ummm
Yes?
You might be interested in my comment that got out of hand.
pboy - Yoo did a whole article just for you. He's the best. Always answers these types of questions for me.
Ah, hahaha.. welcome to my world, Stacy and Yoo!
So you're saying that the light from these far galaxies isn't ACTUALLY 13 billion years old, it is calculated that the galaxies ARE NOW 13 billion light years away?
Sometimes you seem to be saying that and other times you seem to be agreeing that the very distant galaxies are, in fact, at distances, which if newly observed WOULD make the universe seem like it was 17 billion years old?
How do objects, starting at a point, become 17 billion light years apart if nothing can travel faster than light, in a universe that is only 13.5(is that right?) billion years old?
Answering my own question here, if both the distant galaxies and our galaxy are zooming apart then the universe is at most 27 Billion light years apart and the distant galaxy is accounting for half the red shift and our galaxy's movement is accounting fot the other half?
Your other point about the Andromeda Galaxy. 'She' seems to be travelling towards us at approximately LIGHT SPEED!
Stupid me, I was always under the impression that the only thing that could travel at light speed was the Star Ship Enterprise!
I shouldn't be IN this conversation because I'm a dolt about this stuff.
I was all happy before, but now you've gone and messed with my mind! ;-)
I think I understand this ...
"... the universe is at most 27 Billion light years apart and the distant galaxy is accounting for half the red shift and our galaxy's movement is accounting fot the other half?..."
This makes sense. 27/2 = 13.5
If the starting point is the same.
Nothing moves faster than the speed of light that we KNOW of!
Like I said to Yoo! "My brain hurts"!
But, Stacy, to make matters much, much worse, what if that has all been taken into account in their calculations and they STILL 'percieve' the farthest galaxies to be travelling faster than light speed!?
That would mean that we are travelling faster than light speed in the other direction TOO!
Hmm.
"That would mean that we are travelling faster than light speed in the other direction TOO!"
That's impossible. Ask me how I know.
Okay, I'll bite, "How do you know?"
Because I can't even ride a roller coaster without throwing up! ;-)
Indeed, that's some nailed-down, concrete, fineley calibrated evidence you have there.
Have you written this up in a peer reviewed magazine yet?
Nah ... but I've been thinking about it though.
About the Andromeda Galaxy seemingly traveling near the speed of light: I don't recall 0.1% of the speed of light ever being referred as approximately light speed. :P
"..it’s pretty certain that it is even now approaching our galaxy at a steady 300 kilometers per second."
Well, Yoo, they're your figures.
See what I did there, I saw the 300 and the 'kilo' and that made 300,000 ... and I know that 300,000 km/sec is light speed.
And before you ask, no I was not the one responsible for crashing that last Mars disaster!
I think that this offers up a reasonable explanation for why galaxies are further apart than going at the speed of light would provide. Namely, that, at some point, the universe did expand faster than the speed of light (which I assume is the Big Bang).
My verdict? Cosmology is a hell of a mindfuck.
Maybe it's a 'work-around'.
Nothing can travel faster than light, BUT anything with enough energy so that it ought to travel faster, it doesn't but it rips space open behind it 'as if' it WERE travelling faster!
Presumably that creates some kind of drag or stretching, so we might expect it to (on a local scale) sproing back together!
Sproing back together...I've always liked that idea! The "Big Crunch", where the Universe just runs out of gas and starts slipping back from once it came...
I think that that particular scenario has been partially ruled out, but you never know when it comes to these things. Physics seems to always be getting some complicated modifications, so ya never know...
pboy said,
"...Seems to me that we'd be lucky to see a photon or two from a galaxy billions of light years away. (just saying)"
This is accurate. It takes very large telescopes to even resolve enough detail in Andromeda to discern that it's not a "spiral nebula", as it was once called.
And don't forget that it was only in the late 1920's that Edwin Hubble proved the expanding universe with redshift calculations. Prior to that, the Milky Way was thought to BE the universe, and that was less than 100 years ago.
Then, if we consider that the age is 13.5 By, that gives a radial distance from the 'center' of 27 Billion light years to where the speeding galaxies are now, or a diameter of something like 54 billion light years.
A more intriguing question is:
"Into WHAT is the universe expanding?"
The diameter calc assumes that the objects at the very edge of the universe (if the universe can be said to have an "edge") would be receding from the "center" at speeds approaching 'c'.
Or I could be all wet.
Who lives in a blog right next to the sea?
Pboy Squarepants!
Pboy,
Did you see this?
WWPD.
Yea Ed, it's kind of a 'head=scratcher, isn't it?
oneblood. I liked the cartoonist and his cartoons.
I don't think that he was 'so much' funny as very insightful.
Anyway, what are you a psychic?
You were on about Jimi Hendrix and it dawned on me that I was wearing a 'Jimi Hendrix' t-shirt.
Now you show me these cartoons and I just happen to have bought a Wacom 'Bamboo' pad and I've been thinking what to do with it.
Of course I'll never believe that you are psychic until you give me the winning lottery numbers and when to play them!
Still, if I did win multi-millions I'd get the house and car etc. then give fifties away at the soup kitchen and buy some early-bird bums their morning booze at the liquor store.
I wonder if I'd be able to stay completely non-judgemental.
Seems that seed has already been planted because I'd already be on the lookout for professional 'helpers-of-the-poor' with their never ending need for more money, more money, more money...
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