Help me understand the universe.

Something that's bothered me for a long time now, and I thought maybe someone here can help me out.

Can someone please explain to me how they know the distance of objects in the universe?

If it takes the sun’s rays about 8.3 minutes to reach earth that means when we look at a sunrise, the sun's actually not where we see it, but 8.3 minutes “higher” than what we see. (Sorry if it sounds a little confusing).
That means we are looking at the sun in the past, about 8.3 minutes.

Now how about an object in space, like a distant galaxy. NASA says it’s 50 million light years away. That means we see it now as it looked 50 million ears ago, since it took 50 million years for its light to reach us, right?
SO does that mean the object might be gone by now or changed completely? I mean a LOT could have happened in 50 million years.
Does that mean everything we know about the universe is outdated by millions of years?

Am I just not understanding this??


Could it be the black holes, supernovas and all the other cool things out there might be gone by now or might have changed into something completely different?

anything is possible, when you don't have any answers.

Myself, I believe we've already collided with another galaxy, a galaxy that we cannot see.

some things are closer... but yeah, a lot of stuff they see is way in the past.

reply to post by Nightfury

You are correct. The "further away" an object appears, the older the light/information is. There are a lot of assumptions astronomers/astrophysicists make about what those super distant objects are doing now based on what they see "closer by".

The part that has always baffled me, is that the further/older those objects appear, the faster those objects appear to be moving away from us. Paradoxically, from that they conclude that the expansion of the universe is increasing. What? That makes no sense. If the more recent information/closer objects appear to be moving slow means the expansion is actually slowing down (past-->fast + recent-->slow = expansion is slowing)!!!!!!!

I asked an astronomer that question, and he didn't seem to understand this most basic of concepts, which made me wonder about his critical thinking abilities.

reply to post by leira7


Could we have collided with our own mirror galaxy of dark matter?

Maybe since everything is flat dimensions are stacked on top of each other like an apartment building and you can only see what's on your floor unless you can figure out how to get the damn elevator to work.

Ok, I'll shut up. I'm not even sure if it's all flat. I know some of it is.

Seriously, how is it that they can detect speed that far out?... by characteristics of the light it is emitting... or something else?

reply to post by SpaceJ


To add a question to this thread that has never really occurred to me before... How do they know how far away anything is really? I mean they can't really tell just by looking can they?

I don't think they are looking at it in a traditional sense when it's that far away. They are detecting radiation somehow or something and probably have to go through all kinds of processes to get the idea of an actual image.

One more thing...

To observe distance, you need to have a perception of depth. That's why we have 2 eyes and a person with only 1 eye, can't percieve depth, so they can't tell distance, so how can they tell the distance by looking through a telescope?
Don't tell me they read it with a range finder by shooting a laser and waiting or it to bounce back,,, 50 million light years might make for a long wait..

So how do they know the distance?

Originally posted by Nightfury
One more thing...

To observe distance, you need to have a perception of depth. That's why we have 2 eyes and a person with only 1 eye, can't percieve depth, so they can't tell distance, so how can they tell the distance by looking through a telescope?
Don't tell me they read it with a range finder by shooting a laser and waiting or it to bounce back,,, 50 million light years might make for a long wait..

So how do they know the distance?

When you find out, you tell me ok.

Even if they COULD detect distance, that # happened way the # back when, so it the universe is slowing, yeah, it would be faster back then.

reply to post by harrytuttle

The part that has always baffled me, is that the further/older those objects appear, the faster those objects appear to be moving away from us. Paradoxically, from that they conclude that the expansion of the universe is increasing. What? That makes no sense. If the more recent information/closer objects appear to be moving slow means the expansion is actually slowing down (past-->fast + recent-->slow = expansion is slowing)!!!!!!!

The expansion depends on distance between two objects, so thats why distant objects appear to move away faster than closer objects.

en.wikipedia.org...

this site explained the ways of determining distances of various objects in space pretty well

underwater-demolitions.blogspot.com...

reply to post by Nightfury

For things that are close to us, like our Sun, we can use a little math. By comparing the angles between our Sun and Moon we can come up with an Earth-Sun distance.
Sun and Moon
Sun and Venus

To determine the distance of nearby stars and galaxies we can compare the observed angles between a distant object and Earth at different points in our orbit around the Sun. This is called Parallax.
Parallax

Another way of determining the distance of relatively nearby objects is by using Cepheid variable stars.
Cepheid variables
Cepheid stars have what we call a standard candle, luminosity, that can be compared with stars of the same type observed from here on Earth. The comparison of the brightness of these stars can give us a distance.

The problem that these measurements face is that they become unreliable over great distances. The greater the distances the more unreliable these measurement become. At some point in the observable Universe these measurements fail and from this point we use 'H'.

Hubble's Law or the Hubble Constant (or simply 'H') is measuring the observed Doppler effect of light from distant objects that are a product of the objects amount of acceleration away from us.
Hubble's law
This seams to work well except when we are dealing with phenomena like quasars and how light is effected over really vast distances. It is from this observation that it does appear that the farther away an object is from us the faster it seems to be accelerating away. Now reverse this idea of Universal expansion and we can conclude that there was at one time a Universal singularity, i.e. big bang.

The thing is that even the Hubble constant has problems and our understanding of the Universe is limited to what we can observe from where we are. I think the theory behind Universal expansion and the big bang are a product of this limited understanding or rather misunderstanding. It is said that the Universe is 13-15 billion years old yet we measure some objects at over 40-50 billion light years away. One of these measurements must be wrong yet that's not how cosmologists deal with this problem. They add in a factitious factor called "Lookback Time" which again, like the big bang theory, is in violation of physics and relativity.

Originally posted by leira7

Myself, I believe we've already collided with another galaxy, a galaxy that we cannot see.

Actually we can see it. It's the galaxy Sagittarius.
Sagittarius galaxy
There is also a theory that our solar system is originally from Sagittarius.
We are not from here.

Originally posted by Devino
It is said that the Universe is 13-15 billion years old yet we measure some objects at over 40-50 billion light years away. One of these measurements must be wrong yet that's not how cosmologists deal with this problem. They add in a factitious factor called "Lookback Time" which again, like the big bang theory, is in violation of physics and relativity.

excellent post devino, I think you answered the OP question well and I agree with your post up to the part I quoted.

What objects have been measured at 40-50 billion light years away?

I also don't understand why you would say lookback time is in violation of physics and relativity.

To the OP, you have to realize 50 million years isn't very long on an astronomical scale, so the object seen with 50 million years lookback time may still exist today but would be in a different position than it was 50 million years ago.

However an object 11 billion light years away (lookback time) probably doesn't exist today, in its current form. If it was a galaxy, 11 billion light years away 11 billion years ago, it may be 30 or 40 billion light years away today, but is made up of completely different stars, since all the 11 billion year old stars we see now probably died and were replaced with younger stars.

Like the Cepheid variable devino mentioned, the type 1A supernova is another "yardstick" astronomers use to determine distance. The luminosity curve of those particular supernovas is believed to be a good indicator of distance when they occur.

Here is the Wikipedia article that answers the OP question in depth:

Cosmic distance ladder

The cosmic distance ladder (also known as the Extragalactic Distance Scale) is the succession of methods by which astronomers determine the distances to celestial objects. A real direct distance measurement to an astronomical object is only possible for those objects that are "close enough" (within about a thousand parsecs) to Earth. The techniques for determining distances to more distant objects are all based on various measured correlations between methods that work at close distances with methods that work at larger distances. Several methods rely on a standard candle, which is an astronomical object that has a known luminosity.

The ladder analogy arises because no one technique can measure distances at all ranges encountered in astronomy. Instead, one method can be used to measure nearby distances, a second can be used to measure nearby to intermediate distances, and so on. Each rung of the ladder provides information that can be used to determine the distances at the next higher rung.

That summary should give you an idea about what's in the article, it describes all the measurement techniques at each rung of the ladder in detail.

Thanks for all the replies..

I learned quite a bit, and now have even more questions, but I guess we will never "really" know... at least not yet. Till we can come up with a way to measure those type of distances, it's pretty much a guessing game. There is just too many variables. Space sure is a mystery.

reply to post by Arbitrageur

What objects have been measured at 40-50 billion light years away?
I also don't understand why you would say lookback time is in violation of physics and relativity.

I think most of this discussion can be found in threads like,"The Big Bang Never Happened", which you and I had spent some time in. I don't know if I can find the article that claims to have measured objects at 40+ Gly away but I remember the discussion over this from these older threads. Going off of memory I think that the object in question was a Quasar.
I did a little search and found stuff like this.

The current comoving distance to the particles which emitted the CMBR, representing the radius of the visible universe, is calculated to be about 14 billion parsecs (45.7 billion light years), while the current comoving distance to the edge of the observable universe is calculated to be 14.3 billion parsecs (46.6 billion light years)

Source- Wiki

Current interpretations of astronomical observations indicate that the age of the universe is 13.75 ±0.17 billion years,[4] and that the diameter of the observable universe is at least 93 billion light years, or 8.80 × 1026 metres.[5] According to general relativity, space can expand faster than the speed of light, although we can view only a small portion of the universe due to the limitation imposed by light speed.

Source- Wiki

I don't recall anything even close to this underlined claim anywhere in General Relativity so I find that I disagree with this statement. Actually I find this to be in direct contradiction to the theory of General Relativity. To put it in simple terms empty space has no value (0) and therefore cannot expand nor contract, speed up nor slow down. Here is a Wiki definition of expanding space.

The metric expansion of space is the increase of distance between distant objects in the universe with time.
It is an intrinsic expansion—that is, it is defined by the relative separation of parts of the universe and not by motion "outward" into preexisting space. (In other words, the universe is not expanding "into" anything outside of itself).

Source- Wiki
Again I find the underlined to be in contradiction but it is just one word and I don't see any reason to argue simple semantics.
Space does not expand outward nor inward into nor out of itself. It is the objects within space that expand away from each other, space itself has no value. All objects have an acceleration limitation and there are limitations on how far light can travel over a given amount of time. To make the claim that expanding space can somehow accelerate these values well over their limitations makes no sense and thus is in contradiction.

While special relativity constrains objects in the universe from moving faster than the speed of light with respect to each other, there is no such theoretical constraint when space itself is expanding. It is thus possible for two very distant objects to be moving away from each other at a speed greater than the speed of light

Source same as above.

The problem I have with lookback time is summarized within the above statement.
This problem is dealt with in the theory of relativity (two objects moving away from each other at a supposed greater than 'c' value) without the need for an expanding space and the same limitations to the speed of light are maintained. It is only with the theory of expanding space that an attempt is made to explain a loop hole in the theory of relativity.

I find it interesting that this made up value of a supposed expanding space exactly fit these huge measured distances which would otherwise contradict our current theory of the Universe. It seems that this arbitrary value was created to make the big bang theory fit observations and therefore is a fictitious value.

I realize that an understanding of what is really happening in the Universe goes far beyond the limitations presented here in this forum yet I cannot accept the overall concept of expanding space. What I see here is not a loop hole around relativity but rather a contradiction. What is being observed by astronomers contradicts our current theory of the Universe and therefore should be adjusted rather than make up new and impossible values such as invisible matter/energy and the expansion of nothing.

It is the medium in space that propagates light and it is this medium that has value although we have not yet measured its value yet. Call this medium dark energy, the Aether or whatever but not a void nor empty space. If this "medium" is out there then we can find it and measure it. However, if we conclude that this medium is not there or is a void then we will never find anything. Why look for that which is not there?

Hope this helps you understand the Universe a little more.