We're looking back in time the further out we go because it takes time for light to travel to us. So the furthest out we can see is about 46.5 billion light years away, which is crazy, but it also means you can look back into the past and try to figure out how the universe formed, which again, is what cosmologists do.
The farthest object in space that you can see with only your eyes in the night sky is the Andromeda Galaxy. It is a huge spiral galaxy, and it is the closest large galaxy to us outside of the Milky Way.
The most distant thing we can see with our bare eyeballs is Andromeda at 2.6 million light years, which in dark skies looks like a fuzzy blob.
The light that travels the longest gets stretched by the greatest amount, and the object that emitted that light is now at a greater distance because the universe is expanding. We can see objects up to 46.1 billion light-years away precisely because of the expanding universe.
We are able to see the farthest galaxy almost 13.8 billion light years away. The scientists have estimated their current location, due to the expansion of the universe as 46.5 billion light years away, hence the diameter of the visible universe is 93 billion light years.
More specifically, the observable universe is the region of space visible to us from Earth. And since the universe is only about 13.8 billion years old and light takes time to travel through space, then regardless of what direction we look, we see light that's been traveling, at most, 13.8 billion years.
We do not know the exact age of the universe, but we believe that it is around 13 billion years - give or take a few billion. Astronomers estimate the age of the universe in two ways: (a) by looking for the oldest stars; and (b) by measuring the rate of expansion of the universe and extrapolating back to the Big Bang.
For most space objects, we use light-years to describe their distance. A light-year is the distance light travels in one Earth year. One light-year is about 6 trillion miles (9 trillion km). That is a 6 with 12 zeros behind it!
Light-year is the distance light travels in one year. Light zips through interstellar space at 186,000 miles (300,000 kilometers) per second and 5.88 trillion miles (9.46 trillion kilometers) per year.
Travel Time
At the rate of 17.3 km/sec (the rate Voyager is traveling away from the Sun), it would take around 225,000,000,000,000 years to reach this distance.
When in a tall building, the horizon can be as far as about 40 miles. From the ISS, the distance to the horizon is over 1,000 miles. So from horizon to horizon, the section of the Earth you can see at any one time is a patch about 2,000 miles across, almost enough to see the entire United States at once.
Without a space suit, a human can survive up to 8 kilometers (5 miles) into space. Any space above that is known as the Death Zone because there is not enough oxygen to support life. But with a space suit, a human can go as high as 555 kilometers (347 miles). That's the altitude of the Hubble Space Telescope.
One such estimate says that there are between 100 and 200 billion galaxies in the observable universe. Other astronomers have tried to estimate the number of 'missed' galaxies in previous studies and come up with a total number of 2 trillion galaxies in the universe.
There's a limit to how much of the universe we can see. The observable universe is finite in that it hasn't existed forever. It extends 46 billion light years in every direction from us.
The trite answer is that both space and time were created at the big bang about 14 billion years ago, so there is nothing beyond the universe. However, much of the universe exists beyond the observable universe, which is maybe about 90 billion light years across.
One thing's for sure: the Universe does not have an edge. There's no physical boundary – no wall, no border, no fence around the edges of the cosmos. This doesn't necessarily mean that the Universe is infinitely large though.
If an object ever did reach the speed of light, its mass would become infinite. And as a result, the energy required to move the object would also become infinite: an impossibility.
But Einstein showed that the universe does, in fact, have a speed limit: the speed of light in a vacuum (that is, empty space). Nothing can travel faster than 300,000 kilometers per second (186,000 miles per second).
At 99.99999 percent of the speed of light, for a year, more than 2000 years would pass on Earth. The point is, the closer you get to the speed of light, the more time dilation is experienced. Achieving those speeds, however, is incredibly unlikely and probably impossible.
Five years on a ship traveling at 99 percent the speed of light (2.5 years out and 2.5 years back) corresponds to roughly 36 years on Earth. When the spaceship returned to Earth, the people onboard would come back 31 years in their future--but they would be only five years older than when they left.
Constant Speed
So what does this sentence really mean? Surprisingly, the answer has nothing to do with the actual speed of light, which is 300,000 kilometers per second (186,000 miles per second) through the "vacuum" of empty space.
The universe is everything. It includes all of space, and all the matter and energy that space contains. It even includes time itself and, of course, it includes you. Earth and the Moon are part of the universe, as are the other planets and their many dozens of moons.
HD 140283 had a higher than predicted oxygen-to-iron ratio and, since oxygen was not abundant in the universe for a few million years, it pointed again to a lower age for the star. As a result of all of this work, Bond and his collaborators estimated HD 140283's age to be 14.46 billion years.
The Big Bang was the moment 13.8 billion years ago when the universe began as a tiny, dense, fireball that exploded. Most astronomers use the Big Bang theory to explain how the universe began.
One study suggested that the "Methuselah Star" is older than the Universe itself. The Universe is thought to be 13.797 billion years old, with an uncertainty of ±0.023 billion years. In 2013, a measurement of the "Methuselah Star" suggested that it is 14.45 billion years old — older than the age of the Universe.