What is space? |
A typical galaxy contains over 100,000 million stars.
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The Universe
The Universe takes in Earth and its moon, the Sun and the solar system, the Milky Way, the galaxies we know, and the galaxies we haven't yet discovered.
The Universe takes in Earth and its moon, the Sun and the solar system, the Milky Way, the galaxies we know, and the galaxies we haven't yet discovered.
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That's big...
The galaxies are spread over such unimaginable distances that even a space probe would take two billion years to cross our galaxy. |
...and getting bigger
The Universe is still expanding, so all the galaxies are moving farther and farther apart. |
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Dark mysteries
We can't see everything in space. Experts think there's lots of mysterious "dark matter" between the stars. |
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More of the same?
There might be other, parallel, Universes. Experts call these the "multiverse". |
Experiment
You can make your own Universe by drawing dots and spirals around a flat balloon to represent galaxies. As you inflate the balloon, these "galaxies" move apart - that's what's happening to the Universe. |
How fast does the Voyager 1 travel?
About 17.1 km per second.
Hubble Telescope
Frequently Asked Questions
What is the universe?
The universe includes all of space and is everything that we know. Made up of matter and space, it holds everything from the tiniest particle to the biggest galaxy. This includes planets, moons and stars. Millions of stars gathered together are called galaxies, which make up what we know as the universe.
How did the universe begin?
Before the universe there was nothing. There was no time and no matter. Astronomers believe that the universe began with an explosion which is known as the Big Bang. Big Bang theories are constantly being reviewed because it is such a difficult idea to explore. It is very difficult to imagine that an extremely hot fireball just came out of nowhere.
The explosion was not like bomb explosions that we know where fragments are thrown outward. It was more an explosion of space within itself. Immediately after this explosion, the fireball began to expand rapidly. As it expanded, it began to cool and particles began to form. These particles then became the building blocks of life upon which all other matter was created.
Astronomers believe that the universe has been growing bigger and bigger ever since this time. The Big Bang was the very beginning of time, space and matter.
The explosion was not like bomb explosions that we know where fragments are thrown outward. It was more an explosion of space within itself. Immediately after this explosion, the fireball began to expand rapidly. As it expanded, it began to cool and particles began to form. These particles then became the building blocks of life upon which all other matter was created.
Astronomers believe that the universe has been growing bigger and bigger ever since this time. The Big Bang was the very beginning of time, space and matter.
Why is the sky dark at night?
The answer to this question provides proof that the universe did have a definite starting point and has not been in existence forever. If the universe were infinitely old (did not have a definite starting point), then we would not see darkness at night. Because of the billions and billions of stars that would exist in an infinite universe, when you looked into the sky at night all you would see would be a blaze of light. There would be no dark patches in between the stars.
The fact that we can see darkness at night suggests that there is a point beyond which stars do not exist. This means that the existence of stars is not infinite. When we look into the sky we can see beyond the stars into a black void. This suggests that there was a time when stars began to exist.
The fact that we can see darkness at night suggests that there is a point beyond which stars do not exist. This means that the existence of stars is not infinite. When we look into the sky we can see beyond the stars into a black void. This suggests that there was a time when stars began to exist.
How old is the universe?
The age of the universe represents the largest possible value of time ever measured. For this reason it is difficult to measure it accurately. There are, however, several different methods and formulae that scientists use to determine its approximate age. Three of these methods are outlined below.
It is possible for scientists to study the expansion rate of the universe, then try to work backwards to find out when it began expanding. This would indicate the approximate time of the Big Bang.
Another method is to study meteorites. Meteorites are chunks of rock or metal that hit the Earth. Scientists look for radioactive material in meteorites that were produced in stars way back around the time of the Big Bang. Scientists are able to estimate ages by the rate of decay of this matter.
Scientists can also study stars in very old clusters in the Milky Way. By looking at the oldest clusters, they can determine that the universe would have begun prior to these stars being formed.
Currently, the most accurate age of the universe is determined by taking an average of the results of many different methods. By doing this, the current belief is that the Universe is approximately 13.7 billion years old.
It is possible for scientists to study the expansion rate of the universe, then try to work backwards to find out when it began expanding. This would indicate the approximate time of the Big Bang.
Another method is to study meteorites. Meteorites are chunks of rock or metal that hit the Earth. Scientists look for radioactive material in meteorites that were produced in stars way back around the time of the Big Bang. Scientists are able to estimate ages by the rate of decay of this matter.
Scientists can also study stars in very old clusters in the Milky Way. By looking at the oldest clusters, they can determine that the universe would have begun prior to these stars being formed.
Currently, the most accurate age of the universe is determined by taking an average of the results of many different methods. By doing this, the current belief is that the Universe is approximately 13.7 billion years old.
Why did the universe begin?
It is very difficult to imagine the nothingness before the universe began. It is more difficult to understand that the universe came out of that nothingness - from nowhere. It is only natural that we ask the question, "Why did a fireball just appear out of nowhere?".
Science cannot answer that question, however. Philosophers and theologians have their own theories about the causes of the Big Bang and how our world began. For now, however, it will remain a mystery as such theories are very difficult to prove or disprove.
Science cannot answer that question, however. Philosophers and theologians have their own theories about the causes of the Big Bang and how our world began. For now, however, it will remain a mystery as such theories are very difficult to prove or disprove.
How big is the universe?
Scientists have never been able to measure the exact size of the universe. After all, it is bigger than anything else ever measured. The closest they have come to measuring its size has been with the use of a spectroscope. A spectroscope is an instrument that can measure whether an object in space is moving away from the Earth or towards it.
Using this instrument, scientists were able to learn that the universe is still constantly growing in every direction. There is evidence that it has been expanding ever since the beginning of time. It is extremely difficult to comprehend the size that it must be today. Scientists do not know whether it will ever stop growing or just continue expanding forever.
Using this instrument, scientists were able to learn that the universe is still constantly growing in every direction. There is evidence that it has been expanding ever since the beginning of time. It is extremely difficult to comprehend the size that it must be today. Scientists do not know whether it will ever stop growing or just continue expanding forever.
What is the future of the universe?
There are a number of theories about what may happen to the universe in the future. One of these theories is that the expansion of the universe will eventually slow down. It is believed that this could be caused by the increased gravitational attraction of all matter in the universe.
If this were the case, the universe would not only stop expanding, it would begin the opposite process of contracting (getting smaller). This contracting would last for about the same amount of time as the expanding process lasted in total. Eventually, all matter would be compressed (squashed together). All matter, time and the universe as we know it would cease to exist.
The end of the universe occurring in this way has been labelled the Big Crunch. It is seen to be the opposite of the Big Bang theory. The Big Crunch is a rather dim forecast for the future of our beautiful world as we know it. It is good news, therefore, that another theory about the future seems much more likely.
Recent scientific evidence has shown that the expansion of the universe is not slowing down, but is, in fact, accelerating. In other words, it has been discovered that the universe is increasing in size much faster now than in the past. Since the universe is expanding so fast scientists have to use a new amount of time called planck times which are very significantly shorter than a single second. Most scientists now believe that the Big Crunch will never happen and that the universe will continue to expand forever.
If this were the case, the universe would not only stop expanding, it would begin the opposite process of contracting (getting smaller). This contracting would last for about the same amount of time as the expanding process lasted in total. Eventually, all matter would be compressed (squashed together). All matter, time and the universe as we know it would cease to exist.
The end of the universe occurring in this way has been labelled the Big Crunch. It is seen to be the opposite of the Big Bang theory. The Big Crunch is a rather dim forecast for the future of our beautiful world as we know it. It is good news, therefore, that another theory about the future seems much more likely.
Recent scientific evidence has shown that the expansion of the universe is not slowing down, but is, in fact, accelerating. In other words, it has been discovered that the universe is increasing in size much faster now than in the past. Since the universe is expanding so fast scientists have to use a new amount of time called planck times which are very significantly shorter than a single second. Most scientists now believe that the Big Crunch will never happen and that the universe will continue to expand forever.