Thread: how can we know the age?

We are constantly moving out from where the big bang happened correct? Now I know its hard to know exactly where the singularity was located, but I'm having a hard time understanding something. The observable light that we examine as far back in time as we can could not be the earliest light nor could it be early at all, right? Heres my illustration. Imagine we are on a baseball field. If the earth was a ball and we were in the pitchers hand on the mound. (point of the big bang) and I were thrown to the catcher. (the point spatially we are at right now in the universe) it would take time to get there, far slower than the light traveling around me. If I started trying to observe what happened anywhere before I hit the catcher's mitt, it would be impossible because that light had already passed me while I was traveling to the catcher. This makes me think that there must have been an enormous amount of time we could never observe given the size of the galaxy and the amount of time it took to get matter to those places, because the early light had passed us and continued out into the universe. How then can we determine the age of the universe if we cant see anything before the time it took to get here? Am I thinking about this wrongly? What am I missing?

When you look at something a very long distance away the light takes a long time to reach you so what you are seeing actually happened a long time ago.

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Light cone - Wikipedia, the free encyclopedia

Right here, where we are, is the place where the big bang happened. We are not "moving out from where it happened". We are not moving thru space as a result of "the expanding universe". (We are moving , but that's not the reason, generally speaking orbital mechanics is the reason.) Space is getting bigger. All of space is expanding. So Earth is where the big Bang happened and so is Mars, and so is Sirus and so is the Andromedia galexy, etc etc.

Sealeaf says it right.
When the cosmologists and astronomers talk about seeing back to the Big Bang they are talking about seeing back in time. They seeing the events that were about the time of the big bang because the light is finally reaching us now from events located very far away in distance.

Originally Posted by thestotle

We are constantly moving out from where the big bang happened correct?

No. It was everywhere.

Now I know its hard to know exactly where the singularity was located

It was here! (And there, and over there...)

Perhaps the best way to realise this is to run the movie backwards: the universe contracts, and gets more and more dense; eventually we are right next to the Andromeda galaxy then things keep getting denser. Eventually the entire (visible) universe is smaller than a dot. Everywhere is in one small volume.

The observable light that we examine as far back in time as we can could not be the earliest light nor could it be early at all, right?

The oldest radiation we see is the cosmic microwave background. This was released when the universe first became transparent (about 380,000 years after time zero).

Its a difficult question that others have answered, but will add a bit more. First step was to gain a standard candle. This is a souce of light constant across space to help us determine how far away an object is. Stars & galaxys come in all shapes and sizes. Thus, for our standard candle we have type 1A supernova. these supernova always go bang with the same lumonisity.

Thus if its brighter or dimmer to us, we know if the object is closer or further away. As others have said. We are the center of the universe, we are also not the center of the universe. Center does not work with the universe because of the properties of what the universe is. It is, literally everything. The best anology for our universe I have seen is the balloon anology. Take an uninflated balloon and draw several dots on it then blow it up. Which one is the center dot? Of course, this is only taking into account the 2d plane of the balloon surface & not the 3rd dimension, but if you can visualize this anology into the 3rd & 4th dimension you can better understand the properties of the universe.

When we look back to the beginning of the universe, we do not turn our telescopes to a certain point of the sky & say "thats the center" no, we just peer back in time. What we see could better be defined as the hazy outer shell of the observable universe. We are viewing events billions of light years ago & thus, billions of years ago because the light has just now reached us.

Consider a civilization 13 billion light years away from us turning there telescopes to look at us. They would see the early universe, just shortly after the big bang.

They would not see our star, or our earth because they have not formed yet. A civilization 66 million light years away from us could point there telescopes at us and they would witness the dinosaurs being extinct, not humans roaming around on the planet. That is because light from the extinction event is just now reaching them. Kinda understanding the properties of space-time yet? We are not viewing objects 13 billion light years away as they are now, but as they were 13 billion years ago.