Some questions I have about the universe...?

[Neogaia777]

Here's a good explanation: Accelerating expansion of the universe - Wikipedia

No one is sure what is causing the expansion. There are pretty good mathematical models of the expansion, but they involve a constant that's just put in the model to make it fit observation. It's not clear what the physical explanation of it is.

Wikipedia notes "The simplest explanation for dark energy is that it is simply the "cost of having space": that is, a volume of space has some intrinsic, fundamental energy. ... In fact, most theories of particle physics predict vacuum fluctuations that would give the vacuum this sort of energy." But there are problems with that explanation, as noted in the article, and there are other possibilities. This is an area that many people are working on.

The rate appears to be increasing, though I wouldn't consider that a final result. There wouldn't be a center, because all of space is expanding. Every point is going away from every other point.

The fact that we don't have a complete explanation doesn't mean it might not be happening. There are plenty of things that we know happen even if we can't explain them.

So, the big bang theory is probably wrong or needs to be rethought then, since it isn't expanding from any definable center?

Is all the "stuff" and the space within galaxies and star systems expanding as well, or not, and if not, why not...?

Thanks for your response,

God Bless!

 

[hedrick]

So, the big bang theory is probably wrong or needs to be rethought then, since it isn't expanding from any definable center?

Is all the "stuff" and the space within galaxies and star systems expanding as well, or not, and if not, why not...?

Thanks for your response,

God Bless!

The big bang was not an explosion. It was also an expansion of space, which also didn't start from any specific point. It's just that popular explanations often don't bother to explain that.

It's worth noting that when you see claims about the size of the universe, that's not quite accurate either.

We have no idea how big the universe actually is. The sizes given are for the "observable universe," i.e portions that we could conceivably know something about. When people say that one second after the big bang the universe was some small size, it's actually only the space that turned into the observable universe that was that small size. The whole thing could have been larger.

E.g. here's a statement from Wikipedia "The proper distance—the distance as would be measured at a specific time, including the present—between Earth and the edge of the observable universe is 46 billion light-years (14 billion parsecs), making the diameter of the observable universe about 91 billion light-years (28×10^9 pc)." Note that they are careful to say "observable universe."

My guess personally is that the universe is finite, but larger than the "observable universe."

Note also that someone spoke of space as "void." That's not entirely accurate. There's stuff going on throughout it. It's mostly on such a small scale that we can't see it. Particles are being created and dying throughout "empty space" all the time. Indeed at very small scales (too small for us to understand much at the moment) one theory is that it's something called a "quantum foam." Note: this is stuff we're not yet sure about. But we are sure that space isn't just a void.

No, the solar system isn't expanding. That's even true of galaxies and clusters of galaxies. They are held together by gravity. That gravity is a lot stronger than the forces that are driving the expansion. Those forces are very weak. They have a big effect just because distances are so great; they've got plenty of space to work on. Here's an answer to your question: Do Atoms Get Bigger as the Universe Expands?. That page points out that the balloon analogy is true only over very long distances. It oversimplifies the situation, but it's still a good way to get people to understand the difference between an explosion and the expansion of the universe.

 

[Neogaia777]

The big bang was not an explosion. It was also an expansion of space, which also didn't start from any specific point. It's just that popular explanations often don't bother to explain that.

It's worth noting that when you see claims about the size of the universe, that's not quite accurate either.

We have no idea how big the universe actually is. The sizes given are for the "observable universe," i.e portions that we could conceivably know something about. When people say that one second after the big bang the universe was some small size, it's actually only the space that turned into the observable universe that was that small size. The whole thing could have been larger.

E.g. here's a statement from Wikipedia "The proper distance—the distance as would be measured at a specific time, including the present—between Earth and the edge of the observable universe is 46 billion light-years (14 billion parsecs), making the diameter of the observable universe about 91 billion light-years (28×10^9 pc)." Note that they are careful to say "observable universe."

My guess personally is that the universe is finite, but larger than the "observable universe."

Note also that someone spoke of space as "void." That's not entirely accurate. There's stuff going on throughout it. It's mostly on such a small scale that we can't see it. Particles are being created and dying throughout "empty space" all the time. Indeed at very small scales (too small for us to understand much at the moment) one theory is that it's something called a "quantum foam." Note: this is stuff we're not yet sure about. But we are sure that space isn't just a void.

No, the solar system isn't expanding. That's even true of galaxies and clusters of galaxies. They are held together by gravity. That gravity is a lot stronger than the forces that are driving the expansion. Those forces are very weak. They have a big effect just because distances are so great; they've got plenty of space to work on. Here's an answer to your question: Do Atoms Get Bigger as the Universe Expands?. That page points out that the balloon analogy is true only over very long distances. It oversimplifies the situation, but it's still a good way to get people to understand the difference between an explosion and the expansion of the universe.

Thanks for your explanation and reply,

Gives me some insight, thanks,

God Bless!

 

[hedrick]

I should note that I'm a computer programmer, not a physicist. I'm looking stuff up and checking it pretty carefully, so I'm pretty sure I'm giving you reliable information. But at some point an actual physicist might want to comment.

 

[Neogaia777]

I should note that I'm a computer programmer, not a physicist. I'm looking stuff up and checking it pretty carefully, so I'm pretty sure I'm giving you reliable information. But at some point an actual physicist might want to comment.

K, Thanks for clarifying that...

God Bless!

 

[Widlast]

The notion of topology applies wherever there are sets. Specifically it applies to sets of points in spacetime.

What part of "void" escapes you?

 

[LutheranGuy123]

Just a side note, if something is X light-years away, that doesn't mean that the light we see from is is X years old. We are moving as well, so the light could be much more recent if we are moving in an opposite direction.

 

[Neogaia777]

Just a side note, if something is X light-years away, that doesn't mean that the light we see from is is X years old. We are moving as well, so the light could be much more recent if we are moving in an opposite direction.

You mean possibly more "older" if we are moving apart, right?, but possibly more "recent" if we are approaching each other, correct? Or, do I have that wrong? Kind of confusing to think about...? On second thought, it could be the other way around, Like I said, kinda confused...?

If so, or either way, it wouldn't probably only be a relatively minor difference, that they could probably make "adjustments" for it in their calculations...

God Bless!

 

[Neogaia777]

Is anything moving at or beyond the speed of light? If so, would we even know, or be able to see it...?

God Bless!

 

[SkyWriting]

Relative to an outside observer.

Suppose you step in a spaceship and travel at great speed around the solar system.
Right before you leave, you sync your watch with one that stays on earth.
Upon your return, more time will have passed according to the watch on earth, as opposed to the watch that you took with you.

This is why the internal clocks of GPS satellites are calibrated to run slower then those on earth, to make up for the relativistic effects.

Without that calibration, GPS would be off several miles.

As you approach the speed of light
the difference goes up to infinite.

Faster than light travel might evaporate
both into dust.

 

[LutheranGuy123]

You mean possibly more "older" if we are moving apart, right?, but possibly more "recent" if we are approaching each other, correct? Or, do I have that wrong? Kind of confusing to think about...?

If so it wouldn't probably only be a relatively minor difference, that they could probably make "adjustments" for it in their calculations...

God Bless!

Think of two galaxies five thousand light-years apart. After 5005 years, the light from galaxy A touches galaxy B, because B was moving away from A at .1% the speed of light. But A was also moving away from B at the same speed, so they're 5010 light-years apart even though B is seeing 5005-year-old light.

 

[Neogaia777]

Relative to an outside observer.

Suppose you step in a spaceship and travel at great speed around the solar system.
Right before you leave, you sync your watch with one that stays on earth.
Upon your return, more time will have passed according to the watch on earth, as opposed to the watch that you took with you.

This is why the internal clocks of GPS satellites are calibrated to run slower then those on earth, to make up for the relativistic effects.

Without that calibration, GPS would be off several miles.

Would you age less, or would you not age nor any time pass at all, if you were at the speed of light, yet light or anything at it's speed, does take "time" to travel, travel wise...?

 

[Neogaia777]

Think of two galaxies five thousand light-years apart. After 5005 years, the light from galaxy A touches galaxy B, because B was moving away from A at .1% the speed of light. But A was also moving away from B at the same speed, so they're 5010 light-years apart even though B is seeing 5005-year-old light.

Ok...?, thanks...?

Think I'm getting it... Wouldn't .1 light speed be 250 or 500 years though and 500 or 1,000 total or do I have that wrong...? Oh, never mind, you said .1 "percent", you are correct in that case...

I'm terrible with numbers by the way...

Disregard...

Thanks,

God Bless!

 

[LutheranGuy123]

Ok...?, thanks...?

Think I'm getting it... Wouldn't .1 light speed be 250 or 500 years though and 500 or 1,000 total or do I have that wrong...? Oh, never mind, you said .1 "percent", you are correct in that case...

I'm terrible with numbers by the way...

Disregard...

Thanks,

God Bless!

Well slow it down a bit. Say we're ten yards away from each other and you send another guy (light) running at me at one yard/second. If we don't move, then he's ten yards old when he gets to me. But if I move away from you at .5 yards/second, then he will catch me after fifteen seconds when we're fifteen yards apart. Now let's say that you also run away from me. He catches me after fifteen seconds, but we'd be twenty yards apart.

 

[Neogaia777]

Well slow it down a bit. Say we're ten yards away from each other and you send another guy (light) running at me at one yard/second. If we don't move, then he's ten yards old when he gets to me. But if I move away from you at .5 yards/second, then he will catch me after fifteen seconds when we're fifteen yards apart. Now let's say that you also run away from me. He catches me after fifteen seconds, but we'd be twenty yards apart.

Oh, Ok, that sounds simple enough and makes some sense, Thanks...

Except, what do you mean by ten yards old...?

God Bless!

 

[LutheranGuy123]

Oh, Ok, that sounds simple enough and makes some sense, Thanks...

Except, what do you mean by ten yards old...?

God Bless!

Seconds old, sorry

 

[Neogaia777]

Seconds old, sorry

Oh, OK...

Thanks again,

God Bless!

 

[lesliedellow]

What part of "void" escapes you?

a.) The universe is not a void. If it was you wouldn't be here.
b.) Even if it was a void, you could still put a topology on it - most likely one derived ffom the Minkowski metric.

 

[TagliatelliMonster]

Would you age less, or would you not age nor any time pass at all, if you were at the speed of light, yet light or anything at it's speed, does take "time" to travel, travel wise...?

Relative to the observer.

You will experience time the same way you always do.
But relative to the ones not travelling at high speed, "your" time will run slower.

 

[Radrook]

I wonder if someone would humor me and answer some questions I have about the universe...?

How much space is there between galaxies? Are they far apart like star systems are in galaxies, or not so much?



God Bless!

Galaxies close together are called groups and are closer to one another than to galaxies of other groups. Our group is composed of fifty-four members. Andromeda is two million light years away from us despite being of the same group. Large galaxies such as our own and Andromeda have satellite galaxies which are very much closer. For example the Large Magellanic Cloud orbits our galaxy at a distance of 150,000 light years and the Sagittarius Dwarf galaxy orbits our galaxy at a distance from its hub of a mere 50,000 light years.


The closest galaxy to us is the Canis Major Dwarf Galaxy. It is approx 42,000 light-years from our galactic center, and just 25,000 light years from our Solar System. This puts it closer to us than the center of our own galaxy, which is 30,000 light years away from the Solar System. In short the distances are too varied to give an average for galaxies in the entire visible universe.

BTW
These galaxies which orbit ours are adding individual stars and globular clusters to our own as they are captured by the Millky Way's gravitational pull as they orbit near us. Eventually they will merge with the Milky way entirely. Some speculate that our solar system was added to the Milky Way in that manner.