Size Of The Universe
The size of the universe can be viewed as either the entire physical Universe or the largest distance that light could travel and reach us on Earth. With this in mind, scientists have estimated that the radius of the observable universe is around 93 billion light years. Note that each light year is the distance of which light travels in a year, or about 6 trillion miles. So to put the size of the observable into digits, our observable universe is approximately 558,000,000,000,000,000,000,000 miles. That's the equivalent of 6,002,852,500,000,000 times the distance between the Earth and the Sun.
On the other hand there is the rest of the universe that we could never physically come into contact with. This is where mysteries fill the minds of scientists. How can we find what is outside the observable universe if we couldn't ever see it? After the rise of modern astronomy, another paradox began to puzzle astronomers. In the early 1800s, German astronomer Heinrich Olbers argued that the universe must be finite. If the Universe were infinite and contained stars throughout, Olbers said, then if you looked in any particular direction, your line-of-sight would eventually fall on the surface of a star. Although the apparent size of a star in the sky becomes smaller as the distance to the star increases, the brightness of this smaller surface remains a constant. Therefore, if the Universe were infinite, the whole surface of the night sky should be as bright as a star. Obviously, there are dark areas in the sky, so according to Olbers, the universe must be finite. We know today that the reason that out sky is not filled with stars is that in many cases, light can't travel all the way to Earth from where they came.
Whether the universe is infinite or finite is still arguable because there are reasons to believe and disbelieve both. For example, if the universe is finite, then with the discovery of gravity attracting everything together, theoretically the universe should have collapsed on itself. However, to believe that the universe is infinite leads to a mind-boggling struggle to picture the entire universe. After the discovery of the expansion of the universe, scientists began to believe that the universe outside of what is observable to us is finite.
The estimated age of the observable universe is approximately 13.75 billion years. Scientists have made this estimation using the redshift of the oldest observable stars that produce the lowest energy light. This comes with the idea universe must be older than the oldest star. This means that if the universe has been expanding, it has been expanding for the last 13.75 billion years. It would be very difficult, maybe impossible to comprehend how far the universe has expanded in such a huge time frame.
The image to the right is an image captured by NASA’s WMAP satellite in 2003, illustrating what seemed to be the most distant galaxies in the observable universe at the time. Of the light that has reached us in the last 13 billion years, these were the most distant observable galaxies. Because this distant light has taken approximately 13 billion years to reach us, the image also allows us to see stars as they were around the time that the universe was born.
On the other hand there is the rest of the universe that we could never physically come into contact with. This is where mysteries fill the minds of scientists. How can we find what is outside the observable universe if we couldn't ever see it? After the rise of modern astronomy, another paradox began to puzzle astronomers. In the early 1800s, German astronomer Heinrich Olbers argued that the universe must be finite. If the Universe were infinite and contained stars throughout, Olbers said, then if you looked in any particular direction, your line-of-sight would eventually fall on the surface of a star. Although the apparent size of a star in the sky becomes smaller as the distance to the star increases, the brightness of this smaller surface remains a constant. Therefore, if the Universe were infinite, the whole surface of the night sky should be as bright as a star. Obviously, there are dark areas in the sky, so according to Olbers, the universe must be finite. We know today that the reason that out sky is not filled with stars is that in many cases, light can't travel all the way to Earth from where they came.
Whether the universe is infinite or finite is still arguable because there are reasons to believe and disbelieve both. For example, if the universe is finite, then with the discovery of gravity attracting everything together, theoretically the universe should have collapsed on itself. However, to believe that the universe is infinite leads to a mind-boggling struggle to picture the entire universe. After the discovery of the expansion of the universe, scientists began to believe that the universe outside of what is observable to us is finite.
The estimated age of the observable universe is approximately 13.75 billion years. Scientists have made this estimation using the redshift of the oldest observable stars that produce the lowest energy light. This comes with the idea universe must be older than the oldest star. This means that if the universe has been expanding, it has been expanding for the last 13.75 billion years. It would be very difficult, maybe impossible to comprehend how far the universe has expanded in such a huge time frame.
The image to the right is an image captured by NASA’s WMAP satellite in 2003, illustrating what seemed to be the most distant galaxies in the observable universe at the time. Of the light that has reached us in the last 13 billion years, these were the most distant observable galaxies. Because this distant light has taken approximately 13 billion years to reach us, the image also allows us to see stars as they were around the time that the universe was born.