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A Brief History of Time

From the Big Bang to Black Holes

By Stephen Hawking
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A Brief History of Time: From the Big Bang to Black Holes by Stephen Hawking

A Brief History of Time (1988) takes a look at both the history of scientific theory and the ideas that form our understanding of the universe today. From big bangs and black holes to the smallest particles in the universe, Hawking offers a clear overview of both the history of the universe and the complex science behind it, all presented in a way that even readers who are being introduced to these ideas for the first time will understand.

Key idea 1 of 13

Theories based on what you’ve seen in the past can help predict the future.

You’ve probably heard of the theory of gravity or the theory of relativity? But have you ever paused to think what we really mean when we talk about theories?

A theory, in its most basic terms, is a model that accurately explains large groups of observations. Scientists collect data from observations they see in, for example, experiments, and use it to develop explanations of how and why phenomena happen.

For example, Isaac Newton developed the theory of gravity after observing many phenomena, from apples falling from trees to the movements of planets. Using the data he collected he was able to describe gravity in a theory.

Theories have two great benefits:

First, they allow scientists to make definite predictions about future events.

For example, Newton’s theory of gravity allowed scientists to predict the future movements of objects like planets. If you want to know, say, where Mars will be six months from now, it’s possible to predict this precisely using the theory of gravity.  

Second, theories are always disprovable, meaning they’re open to reform if new evidence that doesn’t fit the theory is found.

For example, people once believed in the theory that everything in the universe revolved around the Earth. Galileo disproved this theory when he noticed moons orbit Jupiter; he could therefore show that actually not everything orbit the Earth.

So in effect, a single future observation can always invalidate a theory, no matter how reliable it seems at the moment. This means theories can never be proven correct, and this makes science a constantly evolving process.

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