On average only in the last two decades, professional astronomers and astrophysicists have gotten a dimmer glimpse of how the universe is like. This word universe comes from Latin and means litterally, “turning as one.” As you can guess, the universe is everything, treated as a unit. It is all the matter and energy that exists.
The universe would most resemble a sponge built of light. A three-dimensional mesh of fine strands of light, with empty spaces in between. The curving lines and sheets of light are built up of about 100 billion dots of light, some considerably brighter than others. Each of these dots is a galaxy.
One of the most remarkable features of the universe is its stillness. Though visible light and all the other electromagnetic waves or radiation, such as radio waves, microwaves, infrared light, ultraviolet light, X rays, and gamma rays (the electromagnetic spectrum), travel at the astonishing speed of 300 000 km per second or 186.281 miles every second, all of them seem virtually motionless at the scale of the universe.
This awesome feature of the speed of light may make us to conclude that there is not such a thing as the universe “now”, because there are events on it that occurred in the long past (in time and space). Just for giving an example, an event that has occurred about 2.000.000 light years ago (this is the distance between our galaxy and our next bigger neighbor, the great spiral galaxy of Andromeda), is reaching us just now. We do not know how it is Andromeda now because through this average distance the light that is leaving Andromeda now will reach us until the next 2.000.000 years from now.