attraction that produced the planets made them, ineffect, compete and interact with one another. Imagine the tugs felt on the formingEarth everywhere from thesun, from other planets, and from the center of attraction inside the young planet itself. A huge planet, such as Jupiter, with a proportionally large gravitational field around it, influenced how much material was available for Earth to form and where it would lie relative to the sun.
Computer simulations of the origin of the solar system suggest that Jupiter formed before Earth. Competition with Jupiter for debris meant that the positionof Jupiter defined the shape of the rest of the solar system. If Jupiter formed closer to the sun, it would have led to fewer but largerrocky planets in the interior of the solar system. If Jupiter formed farther from the sun, there would likely have been a larger number of smaller planets. Our planet’s mass and its distance from the sun—the benevolent conditions that have supported liquid water and life—are due in no small part to the influence of Jupiter.
Our dependence on Jupiter lies in every part of our being, from the presence of liquid water on the planet to the size, shape, and workings of our bodies. The formation of Jupiter defined the size of Earth and, in so doing, the pull of gravity on all things on its surface. A simple thought experiment reveals the web of interconnections. If Jupiter had formed closer to the sun, then Earth would have been larger and heavier and the pull of gravity experienced by Earth’s denizens greater. Even in the unlikely event that such a strange Earth managed to hold liquid water, life on the planet would be very different. As every engineer knows, if you want to make a beam resistant to bending with the same material, just make it relatively wider. All else being equal, a heavier Earth means fat and wide bodies to cope with the greatertug of gravity. Conversely, a smallerEarth would have meant less tug of gravity on evolving bodies; hence, their proportions would need to be longer and lighter. The mass of Earth defines the gravity we experience and, in so doing, controls virtually every aspect of our lives, from our size and shape to how we move about, feed, and interact with the planet.
From the imbalance of matter overantimatter in the moments after thebig bang, and the formation ofJupiter that defined our livable planet, to the way a single sperm out of millions fertilized the egg that defined our genes, it is easy to celebrate the lottery each of us has won to be here on a habitable planet. But it is a virtual certainty that within the next billion years thesun will run through itshydrogen fuel, expand, and become superhot. In the process, Earth will almost certainly lose itswater. The subsequent loss of water will cause a runawaygreenhouseeffect, superheating the surface of our planet. Earth will become likeVenus. The next planet with liquidwater, and the conditions for life, will likely lie farther from the sun. Perhaps it will be a more distant body in our solar system that currently has ice—one of themoons of Jupiter such asEuropa, orEnceladus, a moon of Saturn. Our good fortune, the perfection of circumstances that have defined our existence, is just a moment in time.
Alternate fates? Seeing the effect of Jupiter on the shape of our bodies is almost like looking into fun-house mirrors. We would have had more elongated bodies and lived on a smaller planet if Jupiter formed farther from the sun (left), and been short and squat if it formed closer in (right).
CHAPTER FOUR
ABOUTTIME
A trip in a time machine toEarth of 4.5 billion years ago would not only be eerie; it would be perilous. With an atmosphere lacking freeoxygen and raining acid, you’d need a space suit far beyond the technology of modern science to survive. Impact after impact ofrock and ice from space made the surface sometimes roil at thousands of degrees Fahrenheit. With this heat, there were no oceans:
Computer simulations of the origin of the solar system suggest that Jupiter formed before Earth. Competition with Jupiter for debris meant that the positionof Jupiter defined the shape of the rest of the solar system. If Jupiter formed closer to the sun, it would have led to fewer but largerrocky planets in the interior of the solar system. If Jupiter formed farther from the sun, there would likely have been a larger number of smaller planets. Our planet’s mass and its distance from the sun—the benevolent conditions that have supported liquid water and life—are due in no small part to the influence of Jupiter.
Our dependence on Jupiter lies in every part of our being, from the presence of liquid water on the planet to the size, shape, and workings of our bodies. The formation of Jupiter defined the size of Earth and, in so doing, the pull of gravity on all things on its surface. A simple thought experiment reveals the web of interconnections. If Jupiter had formed closer to the sun, then Earth would have been larger and heavier and the pull of gravity experienced by Earth’s denizens greater. Even in the unlikely event that such a strange Earth managed to hold liquid water, life on the planet would be very different. As every engineer knows, if you want to make a beam resistant to bending with the same material, just make it relatively wider. All else being equal, a heavier Earth means fat and wide bodies to cope with the greatertug of gravity. Conversely, a smallerEarth would have meant less tug of gravity on evolving bodies; hence, their proportions would need to be longer and lighter. The mass of Earth defines the gravity we experience and, in so doing, controls virtually every aspect of our lives, from our size and shape to how we move about, feed, and interact with the planet.
From the imbalance of matter overantimatter in the moments after thebig bang, and the formation ofJupiter that defined our livable planet, to the way a single sperm out of millions fertilized the egg that defined our genes, it is easy to celebrate the lottery each of us has won to be here on a habitable planet. But it is a virtual certainty that within the next billion years thesun will run through itshydrogen fuel, expand, and become superhot. In the process, Earth will almost certainly lose itswater. The subsequent loss of water will cause a runawaygreenhouseeffect, superheating the surface of our planet. Earth will become likeVenus. The next planet with liquidwater, and the conditions for life, will likely lie farther from the sun. Perhaps it will be a more distant body in our solar system that currently has ice—one of themoons of Jupiter such asEuropa, orEnceladus, a moon of Saturn. Our good fortune, the perfection of circumstances that have defined our existence, is just a moment in time.
Alternate fates? Seeing the effect of Jupiter on the shape of our bodies is almost like looking into fun-house mirrors. We would have had more elongated bodies and lived on a smaller planet if Jupiter formed farther from the sun (left), and been short and squat if it formed closer in (right).
CHAPTER FOUR
ABOUTTIME
A trip in a time machine toEarth of 4.5 billion years ago would not only be eerie; it would be perilous. With an atmosphere lacking freeoxygen and raining acid, you’d need a space suit far beyond the technology of modern science to survive. Impact after impact ofrock and ice from space made the surface sometimes roil at thousands of degrees Fahrenheit. With this heat, there were no oceans:
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