Fundamentals: Ten Keys to Reality

One witty but unserious answer often has been misattributed to Einstein, though it originates from the science-fiction writer Ray Cummings: “Time is what prevents everything from happening at once.” Another pithy response, which at first may sound no more serious, is that “time is what clocks measure.” Yet that, I believe, is the germ of the correc

Pascal himself took comfort from that insight, as he followed his lament that “the universe grasps me and swallows me up like a speck” with the consolation “but through thought I grasp it.”

One fundamental limitation to human signal processing is the downtime (latency) between the pulses of electrical activity (action potentials) that neurons use to communicate with one another. This recovery period limits the number of pulses to a few tens or hundreds per second, depending on the neuron type. It is probably no accident that the “fram

Today’s best estimate is that 13.8 billion years have elapsed since the big bang.

Putting it another way: There is a quantity, usually written as t, which appears in our fundamental description of how change takes place in the physical world. It is also what people are talking about when they ask, “What time is it?” That is what time is. Time is what clocks measure, and everything that changes is a clock.

One finds the same sorts of substances, organized in the same sorts of ways, spread uniformly over the visible universe, in vast abundance.

They come to live out William Blake’s vision: To see a World in a Grain of Sand And a Heaven in a Wild Flower Hold Infinity in the palm of your hand And Eternity in an hour

For perhaps the most fundamental message of all is that we do understand many aspects of the physical world very deeply. As Albert Einstein put it, “The fact that [the universe] is comprehensible is a miracle.” That, too, was a hard-won discovery.

Hubble’s redshift observations have a compelling interpretation, which revolutionized our picture of the universe. The interpretation relies on a simple but striking effect, first described by Christian Doppler in 1842. Doppler pointed out that if a source of waves is moving away from us, then successive peaks in the wave pattern it emits will come

According to the principles of quantum mechanics, anything that can move does move, spontaneously. As a result, the distance between two points fluctuates. Upon combining general relativity with quantum mechanics, we calculate that space is a kind of quivering Jell-O, in constant motion.