Real Science Friday: The Best Astronomy DVD Ever Made

[One Eyed Jack]

Looks like this is doomed to be another starlight thread. :chuckle:

If we are at the center of the universe then gravity is increasing for all light as it travels toward us.

Well, it's already moving at light speed, so that really doesn't make any difference. General relativity isn't going to make the time go by any slower for the light because it's already stopped due to special relativity.

But I don't see how this solves the travel time problem.

Can you explain?

What do you mean? Light itself has no travel time problem. It can be everywhere at once. We're just dealing with perspectives.

 

[Stripe]

Well, it's already moving at light speed, so that really doesn't make any difference. General relativity isn't going to make the time go by any slower for the light because it's already stopped due to special relativity. What do you mean? Light itself has no travel time problem. It can be everywhere at once. We're just dealing with perspectives.

OK .. let's take a light source that is very distant from us, say from another galaxy. When the source was created it started emitting light. For that light to reach us it had to travel for say a billion years at light-speed to reach Earth.

But that is assuming that the light travelled at a constant rate.

At source it will feel less effect from the universe's center of gravity. As it nears Earth the effect of gravity will increase (assuming Earth is near the center). This will change the speed at which the light travels - slowing it down, I believe.

Is this what you are talking about, or is it something else?

 

[One Eyed Jack]

OK .. let's take a light source that is very distant from us, say from another galaxy. When the source was created it started emitting light. For that light to reach us it had to travel for say a billion years at light-speed to reach Earth.

That's a common misconception. It doesn't actually take the light any time. The billion years is from the perspective of the source. From our perspective it might not be as long. From the light's perspective, it isn't any time at all. It's all relative.

But that is assuming that the light travelled at a constant rate.

At source it will feel less effect from the universe's center of gravity. As it nears Earth the effect of gravity will increase (assuming Earth is near the center). This will change the speed at which the light travels - slowing it down, I believe.

No, time itself will slow down -- for everything in that frame of reference. The light is somewhat independent of that, as time has already stopped for it. It'll be moving, from within whatever frame of reference, at the speed of light.

Is this what you are talking about, or is it something else?

I'm just saying if time is going slower here than out there, we should be seeing exaggerated effects. Which can help explain the acceleration of the expansion of the universe or why the quasars appear so energetic when they're so far away.

 

[Stripe]

That's a common misconception. It doesn't actually take the light any time. The billion years is from the perspective of the source. From our perspective it might not be as long. From the light's perspective, it wasn't any time at all. It's all relative. No, time itself will slow down -- for everything in that frame of reference. The light is somewhat independent of that, as time has already stopped for it. It'll be moving, from within the frame of reference, at the speed of light. I'm just saying if time is going slower here than out there, we should be seeing exaggerated effects. Which can help explain the acceleration of the expansion of the universe or why the quasars appear so energetic when they're so far away.

OK.

I think we are talking about the same thing, but you are using relativity to explain yourself. I do not think time is a malleable commodity. I think light is. But we can avoid that discussion because the result for both of us is the same.

Your reason for "time going slower" (which I would translate as "light slowing down") would be that there is more gravity toward the center of the universe, right?

 

[One Eyed Jack]

OK.

I think we are talking about the same thing, but you are using relativity to explain yourself. I do not think time is a malleable commodity. I think light is. But we can avoid that discussion because the result for both of us is the same.

Yeah, it works out either way.

Your reason for "time going slower" (which I would translate as "light slowing down") would be that there is more gravity toward the center of the universe, right?

Pretty much. At least a gravitational center. I'm not absolutely sure there'd be more gravity there, per se, but I'm not ruling it out.

 

[Stripe]

Yeah, it works out either way.

:up:

Pretty much. At least a gravitational center. I'm not absolutely sure there'd be more gravity there, per se, but I'm not ruling it out.

How could there not be? The further away one goes from the center of gravity, the less the effect of the gravity.

 

[The Barbarian]

What make you think the universe has a center? The evidence indicates that it no more has a center than the surface of the Earth can have a center.

Learn about it here:
http://www.desy.de/user/projects/Physics/Relativity/GR/centre.html

 

[voltaire]

The universe is not exanding period. If it isn't expanding then you cannot say it has no center.

 

[voltaire]

Radiation would not kill all living things barbarian if the source of the radiation is far removed from living things. The vast quantity of water would also diffuse alot of the radiation.

 

[The Barbarian]

The universe is not exanding period. If it isn't expanding then you cannot say it has no center.

The surface of a ping pong ball is not expanding, and yet it has no center. Remember, the surface.

 

[The Barbarian]

Radiation would not kill all living things barbarian if the source of the radiation is far removed from living things. The vast quantity of water would also diffuse alot of the radiation.

The ground and water would have produced killing radiation, if the speed of light was much greater than it is. There are radioactive elements in all of them, but they decay relatively slowly, and so aren't that much of a hazard, in most cases.

If the speed of light had been much greater, the rate of radioactive breakdown would be much greater, and every living thing on Earth would have been fried by it.

 

[Dr.Watson]

Could you give my post a more uncharitable reading? I doubt it.

Psarris brought up some contradictions in the theory on how the solar system was made using the data provided by the theory itself. Until the theory can answer the contradictions within it, it isn't a theory.

Yikes. Theories don't produce data. They are explanations of data. A good theory can make accurate predictions. Perhaps this is what you meant?

 

[Stripe]

Yikes. Theories don't produce data. They are explanations of data. A good theory can make accurate predictions. Perhaps this is what you meant?

Hi, Watties. :wave:

Long time no see.

Hey! Do you have an answer on how aquifers formed yet? If you don't know, feel free to say so. :thumb:

 

[Yorzhik]

Yikes. Theories don't produce data. They are explanations of data. A good theory can make accurate predictions. Perhaps this is what you meant?

Yes, obviously, data doesn't come from a theory itself. With an ever so slight charity to a layman you could have come up with this:
Psarris brought up some contradictions in the theory on how the solar system was made using the data the theory itself stands on. Until the theory can answer the contradictions within it, it isn't a theory.

But, of course, you can't give even the slightest charitable reading to anything said on the opposing side because that's how you act when you realize your theory is not sound.

 

[The Barbarian]

Yes, obviously, data doesn't come from a theory itself. With an ever so slight charity to a layman you could have come up with this:
Psarris brought up some contradictions in the theory on how the solar system was made using the data the theory itself stands on. Until the theory can answer the contradictions within it, it isn't a theory.

If so, there aren't any theories. All of them have unresolved questions about the details. Science is about investigating the questions and improving the theory by increasing it's predictive power. There is no magic bullet out there.

 

[Dr.Watson]

Long time no see.

Not long enough.

 

[Stripe]

Not long enough.

You could leave again .. for longer this time.

But - onto important matters - no answer for us? :noid:

If you don't know, feel free to just say so. :thumb:

 

[Dr.Watson]

But - onto important matters

If only anything you have ever said was even remotely important (or interesting)...le sigh. While you discuss "important matters" the rest of us will discuss scientific ones.

 

[Stripe]

So .. no answer then. Why didn't you just say so?

 

[DavisBJ]

The Best Astronomy DVD Ever Made

This is the show from Friday July 1st, 2011.

The fact that Enyart considers Psarris’ DVD to be the best astronomy DVD ever made is fascinating. With the myriads of good DVDs detailing what has been learned through astronomy and astrophysics, Enyart prefers a DVD that focuses on trying to show much of the astrophysics community are a bunch of incompetent dolts.