As for the observable universe, unless something’s changed since my astronomy class last semester, we can only see out to about 15-16 billion light years. This is not to say that it isn’t possible that radiation from stars or events more distant than that might be reaching us, but only that we haven’t yet got the technology to detect it.

Drew:
Basically, in a special relativity environment such as our universe is generally accepted to be, nothing goes faster than light because infinite energy would be required to drive it forward. Since light always moves at the speed of light, units of time coupled to that speed are convenient measuring sticks around the cosmos. However, with stars or events that are farther away from us, the measurements begin to break down because the space that the light has been traveling through has been expanding. The current theory goes that spacetime is getting bigger all the time, creating space in all directions almost like a balloon being blown up.
The common 13.6 billion ly number comes from calculations on the cosmic background radiation working from the Big Bang theory, assuming that the radiation comes from that event and calculating how long it would take a blackbody emitter (something that radiates all frequencies of the electromagnetic spectrum evenly, like stars do) to cool down from the estimated trillions of degrees generated at the beginning of the universe. They got about 13.6 billion years, so that is now the accepted figure for the age of the universe.
Assuming that the universe started at about the same size as it is now, then we couldn’t see any farther than the age of the universe times the speed that our information travels at (in this case, the speed of light). However, the going theory is that the universe has been creating space fairly evenly all around for billions of years. Therefore, light that originated from matter that was at one time much closer to Earth than it is now could arrive here thousands or billions of years before light from its current position could.

Photons cemitted in the sun’s core take approximately one million years to reach the photosphere (surface layer of the sun). From there, they take only eight minutes to reach Earth.

The event horizon (point at which nothing can escape) of a black hole is smaller than the planet Earth for a three-solar-mass black hole (the most common size). It is thus almost impossible to get pulled into one unless one wanted to go there in the first place.

“The comoving distance from the Earth to the edge of the visible universe is about 46.5 billion light-years in any direction; this is the comoving radius of the visible universe. It is sometimes quoted as a diameter of 92.94 billion light-years[4]. Since the visible universe is a perfect sphere and space is roughly flat, this size corresponds to a comoving volume of about 4/3 x pi x R^3 = 1.4 x 10^32 ly^3
or 3.4×1080 cubic meters.

The figures quoted are distances now (in cosmological time), not distances at the time the light was emitted. For example, the cosmic microwave background radiation that we see right now was emitted about 13.7 billion years ago by matter that has, in the intervening time, condensed into galaxies. Those galaxies are now about 46 billion light-years from us, but at the time the light was emitted, that matter was only about 40 million light-years away from the matter that would eventually become the Earth. See comoving coordinates.

While it is commonly understood that nothing travels faster than light, it is a common misconception that the radius of the observable universe must therefore amount to only 13.7 billion light-years. This would make sense in the static spacetime of special relativity and the big bang being an explosion in this unchanging spacetime.”

Now if anyone can explain exactly what all that means to me then please go ahead.

As an object travels in a curved path, it has an acceleration vector toward the concave side of its arc of travel. The Moon has an acceleration vector directed toward the Earth as it circles monthly, and also has a vector directed at the Sun as it circles annually.

The Moon’s acceleration vector with respect to the Sun is larger than it’s vector toward the Earth, so even at a point in it’s orbit when it is between the Earth and Sun and moving “away” from the Sun W.R.T. Earth, it is still accelerating toward the Sun.

Thus the Moon should be said to orbit the Sun, not the Earth. The Earth and Moon are a true binary planet.

The question is if the universe started with a single point mass and is “only” 13.7 billion years old, how could the diameter of the universe be 93 billion light years? It should at most be 27.4 billion light years across. It’s almost 3.5x too big.

Our solar system is about two-thirds out from the center of the galaxy.

There is complicated evidence that there is a blackhole in the center of the galaxy.

Blackhole do not suck things in, but the high gravitational pull will not allow even light to escape.

If you watched a friend enter a black hole, they would appear frozen in time.

Venus reaches it’s closest to earth every 584 days. This is almost exactly 5 Venusian solar days. Astronomers have yet to discover if this is purely a coincidence.

The first photographs of the far side of the moon were taken by the Soviet Luna 3 space probe in 1959. It wasn’t until 1968 during the Apollo 8 mission that human eyes first saw it in person. But the crew was so busy making sure their trajectory was just right — they wouldn’t crash into the moon nor be flung off into space — that they didn’t have much time to enjoy the view.