For centuries, time was regarded as a constant, independent force, as if the Universe's progress is governed by a single clock.This description of time changed in 1905 with Albert Einstein's theory of special relativity.While the passing of time was already known to be closely connected to space, this monumental theory was the first to combine space and time into a single field, one with measurements that vary depending on the relative motion or gravitational forces of objects within it.Basically, that means time is relative

How does time work?

Time is a measure of non-stop, consistent change in our surroundings, usually from a specific viewpoint.While the concept of time is self-evident and intuitive – the steady passing of events before our eyes; the orbit of the Moon around our planet – describing its fundamental nature is much harder.Even physicists aren't sure what actually happens when time passes. Although they do have a few hypotheses.

What's Time? (In Science)

similarly, the space-contorting volume beyond the horizon of a black hole also distorts perspectives of time.in our universe, we have freedom of space and can move around as we like, but we're forced to march along time's arrow in a linear direction.Calculations show that crossing over a black hole's horizon would swap those freedoms. So we'd no longer have to follow time's strict arrow of direction, but we'd lose the freedom to move around in space, allowing for time travel (of sorts).

What about time travel?

Two people moving at the same velocity will each agree their measures of distance and time match. As one person changes speed, however, they will see the other's measure of time and distance change, even as their own stays the same.Without any reason to prioritize one perspective of time over another, this means time isn't a constant universal unit at all. It is a relative measurement that varies as objects move faster or slower, or as they're subjected to more or less gravity.Gravity curves space and time: The stronger the gravity, the more it curves space-time, and the more time slows down.

Is time real?

Of course, for us to actually see these effects on time, the change in speed or gravitational pull must be enormous. But as an observer accelerates towards the speed of light, unique measures of time become increasingly noticeable.In theory, as a particle approaches the speed of light, we would see its 'clock' slow down. Once it exceeds the speed of light, its clock would, theoretically, seem in reverse from our point of view. From the particle's point of view, our clock would seem to reverse

Is it possible to reverse time?

Models of space-time can describe measurements of time and space varying from one point to the next, but they don't explain much about time's stubborn adherence to a sequence of events.Under these descriptions of time, our Universe is a single block of space-time. There's sort of a beginning – the Big Bang – before which our best understanding of the laws of physics can't be applied. There's sort of an end, where change is no longer measured with any significance. But no single slice of time stands out physically as 'now'.

Why is there a future and a past?

Lively illustrations and fun, accessible text provide an account of the history of time and the evolution of keeping time, from following the sun and the moon to the huge clocks we use today.

timemanagement

Time Management

books

Books

scienceandnature

Science & Nature

Time to read a book. Time to wash dishes. Time to do this or that. You say things like this every day, all the time. But there was a time when time itself was undefined--no one knew the difference between a minute, an hour, or a day. Then people started creating tools to measure time. First they used the big stuff around them--the sun, the moon, water. Soon after, using the knowledge they got from their natural time-telling tools, people began to build clocks--huge clocks unlike the ones we use today. They also used their knowledge of the sun and moon to create calendars made up of months and years. Now, centuries later, we have clocks all around us. We can easily figure out how long a month is. But it took many years of tinkering and inventing to perfect the art of telling time. You could take a few moments now to read all about time. If you have a minute, that is. This title has been selected as a Common Core Text Exemplar (Grades 4-5, Informational Texts)

Bruce Koscielniak is the author and illustrator of several books for children; he is also a musician who has played the violin and jazz guitar for many years. He lives in the Berkshires region of Massachusetts.