l and  sucoo small tomake tiniest detectable difference to us. But for ot,gravity, tself—tters of consequence.

    So if tivity seem  is only because  experience ts ofinteractions in normal life. o turn to Bodanis again, erotivity—for instance o sound. If you are in a park and someoneis playing annoying music, you kno if you move to a more distant spot ter. t’s not because ter, of course, but simply t your positionrelative to it o sometoo small or sluggiso duplicate t a boom box could seem to to produce tvolumes of music simultaneously might seem incredible.

    t cuitive of all ts in tivityis t time is part of space. Our instinct is to regard time as eternal, absolute,immutable—noturb its steady tick. In fact, according to Einstein, time is variableand ever c even  is bound up—“inextricably interconnected,” inStepime.

    Spacetime is usually explained by asking you to imagine somet but pliant—amattress, say, or a s of stretcing a , suc of terial on ting to stretcly. to t t a massive object sucime (terial): it stretc. No, it tries to go in a straigon’slaion, but as it nears t and t rollsdoably drao t. ty—a product of time.

    Every object t es a little depression in t it, is “timate sagging mattress.” Gravity on tcome—“not a ‘force’ but a byproduct of time,” in t Micy does not exist; s and stars is tortion of space andtime.”

    Of course ttress analogy can take us only so far because it doesn’tincorporate t of time. But take us only so far because it is sone