I don't get it?

[ikester7579]

13th February 2003 at 04:46 PM JohnR7 said this in Post #5

According to the theory, the light took 13 billion years to get here. But 13 billion years ago, the universe was smaller than the size of a peanut. So what is moving faster, the expansion of the universe of light?

Good point! Lets see, Since the light that was actually 13 billion years old has already reached us because it was closer, the expansion of space made it take longer for the light to get to us. Have to figure out a formula that would include how fast the exspansion was compare to light speed and how old the earth is. To say this was not so is to say there was no light and the universe was in total darkness 13 billion years ago. So if there was no light when did we get light?

 

[ikester7579]

Yesterday at 01:47 AM Lacmeh said this in Post #11

John, you realize, that room and time are not seperable? Look up Einstein´s theories.
Gravity also affects the room, light won´t be able to excape if gravity is high enough. Hence the term Black Hole...(Light goes in but can´t escape anymore)

 

If a black hole was there. And knowing how much gravitational pull they have, how could anything expand beyond it. In other words how much volicity does it take to escape a black hole?

 

[ikester7579]

Has anyone been able to bend light with gravity?

 

[Jerry Smith]

We have seen light bent by gravity. Here are some good links...

http://sci.esa.int/content/doc/1b/13851_.htm
http://www.iam.ubc.ca/~newbury/lenses/research.html
http://www.iam.ubc.ca/~newbury/lenses/glgallery.html
http://zebu.uoregon.edu/~js/glossary/gravitational_lens.html
http://antwrp.gsfc.nasa.gov/apod/ap001010.html

 

[JohnR7]

Today at 07:20 AM ikester7579 said this in Post #21 exspansion was compare to light speed and how old the earth is. To say this was not so is to say there was no light and the universe was in total darkness 13 billion years ago. So if there was no light when did we get light?

Genesis 1:3
    And God said, Let there be light: and there was light.

We do not know for sure if there was no light in the whole universe, of if this verse means that the planet earth was spinning so fast that there was no light here on earth.

If we are moving away from the "Big Bang" at about the speed of light, and everything in the universe is moving away from each other. Then just like two cars heading away from each other, then the whole universe is moving away from itself at twice the speed of light. But the expansion rate it would seem is very close to the speed of light.

 

[Lacmeh]

Perhaps you should look up on how black holes form. It takes some time for building up a supernova...
Room and time are the same dimension according to Einstein.

Of course does light bend to gravity. It has no other choice. Because light has mass. Granted not very much, but it has it.

 

[Yinlowang]

Light does not have rest mass.

It bends as it follows the curature of spacetime created by mass.

 

[Lacmeh]

Well, light does have mass, according to physics about 7,something grams of photons per year are emitted to earth.

 

[MartinM]

Light carries momentum and therefore mass-energy, in accordance with the relation E^2 = (pc)^2 + m^2c^4
It has no rest mass - the mass-energy is purely a result of its momentum.

 

[DNAunion]

DNAunion:

1) I think there is some confusion as to where the Big Bang occurred. So where did it happen? Right here where Earth is today.

Where else did it happen? Right there where the Sun is today. Where else did it happen? Everywhere in our solar system, in our galaxy, in our galaxy cluster, and so on. I had trouble with this at first, but once someone explained it to me it made sense.

Follow expansion back in time. All points gradually converge and continue to do so until, at the very beginning, all points in space - even those that are billions of light years apart today - were at the same exact "point in space". The Big Bang did not occur "over there" and shoot matter, or light, towards us "over here". It happened "right here", billions of years ago, no matter where in the Universe one is now. So at least some light didn't have to travel more than an inch to reach "us".

2) Lucaspa made a good point. By the time light was "set free", the Universe was already 300,000+ years old. And since inflation occurred before that point in time, the Universe had already expanded at speeds far greater than the speed of light in a vacuum. So by the time the Universe became transparent to light, there were points in space that were so far apart that it took light billions of years to catch up.

3) There are points in space, even today, that are receding from us at a speed greater than c. Surrounding every point in space is something called a Hubble sphere. Roughly speaking, all receding galaxy clusters within a given point's Hubble sphere are receding subluminally; galaxy clusters at the boundary of the Hubble sphere are receding at the speed of light; and those galaxy clusters that lie outside of a Hubble sphere are receding superluminally.

 

[Loki]

Yes, light has been observed to bend from a "straight" path. It was one of the experiments that proved the theory of general relativity. Scientists observed, during a solar eclipse, a star that should not have been visible because the sun is in our line of sight to that star. The light was curved around the sun because of the sun's gravity.

 

[Tenek]

Good old equivalence principle.

Roll a ball on a flat table. It goes straight. Roll the same ball on a table with a dip in the middle, and it will bend inwards slightly. Curvature of space-time bends light and moving objects (gravity).

If you want to see light bending, consider an elevator accelerating upwards away from the earth at 9.8ms^-2 (32 ft.s^-2). If you're in the elevator, you can't tell whether or not you're in an accelerating object, or in a gravitational field.

Now, get somebody to shine a light in the side. Let's reduce c to 1 m/s. In one second, it moves 1 m to the right, and the elevator moves, say, 0.1 m away from it, so you see the beam bent down. The next second, it moves 1 m to the right again, but the elevator moves 0.2 m away, so the curvature is increased. Repeat ad infinitum and you'll see a curved beam in the accelerating elevator, which is exactly what will happen in a gravitational field.