In “A Beacon from the Big Bang,” Lawrence M. Krauss suggests that, if verified, possible observation of gravitational waves from the early universe could provide evidence for a theory in which the universe underwent a period of explosive expansion, or inflation, shortly after the big bang.

Because so much of the described event occurs within an infinitesimal fraction of a second, would not the early universe's components have to have been moving at many multiples of the speed of light?

New York City

How can we see something from the origin of the universe? If light was emitted from that origin, it would travel out from it at the speed of light. Our galaxy and solar system and Earth would evolve billions of years later, meaning the light of the big bang has long since passed us by.

Fort Collins, Colo.

KRAUSS REPLIES: In response to Betancourt: one has to be careful when parsing the phrase “nothing can travel faster than light.” Nothing can travel through space faster than light, but space can expand without limit. This is because, locally, objects in an expanding universe are not moving through nearby space. It is the space that is carrying them apart, like a wave carrying a surfer, who is not moving with respect to the water but moving with respect to the shore.

Concerning Parker's question: the big bang didn't happen at a single point in our universe but throughout all of space, which was at that time contracted to a single point. Therefore, light is not traveling “outward” from a single “center” but rather from all of space.


In “The Other T Party” [The Science of Health], Carina Storrs was quite thorough but neglected one point relating to how many men in the U.S. have received needless testosterone treatment in recent years: she failed to mention the role of the pharmaceutical companies and their extensive promotion of testosterone directly to consumers. These companies have spent millions of dollars in direct advertising to consumers through television.

Oakland, Calif.


In “Know the Jargon” on the “human shield effect” [Advances], Jason G. Goldman reports that a study found that samango monkeys in a South African research center feel safe when a human is behind them. Are these monkeys familiar with humans and thus “know” that humans won't harm them? Or is it that humans “look” safe and that the monkeys “think” they will make a commotion and deflect predators? Or might this attitude exist for some other reason?

Berkeley Heights, N.J.

GOLDMAN REPLIES: These monkeys are well habituated to human presence because they live on the land of South Africa's Lajuma Research Center. It is precisely because the center's monkeys are familiar with humans and are not hunted by them that the monkeys have learned to rely on humans for cover from natural predators that are around them. In areas where humans do represent a threat or where monkeys are uncertain of human intentions, you would not expect a similar pattern of behavior.


In “An Inconvenient Ice,” Lisa Margonelli discusses the potential of methane hydrates, large deposits of methane gas trapped in ice below the seafloor, as both an energy source and a danger in its potential to exacerbate climate change.

It occurs to me that the last Ice Age may have ended when sea levels got low enough to cause massive outpouring of methane from methane hydrates. Are there data that would support this idea?

Pitman, N.J.

MARGONELLI REPLIES: According to earth scientist Gerald R. Dickens of Rice University, “the answer is somewhat complex,” but “it is unlikely that there has been a significant release of methane over the past 100,000 years” from falling sea levels. He explains: “Here's a bit of background: The gas hydrate stability window below the seafloor increases with pressure, and hence depth, but does so nonuniformly. Consequently, even large-amplitude changes in sea level and pressure have a minimal effect on gas hydrate stability at most deep locations.

“But the relatively shallow-water continental slopes that are affected by falling sea levels have experienced many large-amplitude changes in sea level over the past 700,000 years. Gas hydrate deposits take a long time to form and require continuous high pressures to accumulate. This upper zone contains very little gas hydrate because it has been in a continual state of transition over a long period.”


“Let the Games Continue,” by Colm Mulcahy and Dana Richards, celebrates the late Martin Gardner, the longtime author of the Mathematical Games column in Scientific American.

I was a high school freshman when I discovered Gardner's genius in your publication. From then on, I never missed his column while it ran. His ability to grasp complex scientific and mathematical concepts and recast them to be understandable to the layperson was extraordinary. At his death in 2010, humanity lost a great teacher. Gardner was a true inspiration to me. I encourage you to keep celebrating his life and works every October ad infinitum.

via e-mail


“Saving ‘Bambi,’” by Roger Drouin [Advances], reports on efforts that have been suggested to save the monarch butterfly, whose population has greatly declined, including the creation of more milkweed habitat in the U.S.

As a native plant professional, I can confirm that ecological restoration of native grassland ecosystems that contain milkweed plants is the only method to keep the monarchs from going extinct. At a minimum, between $100 billion and $200 billion is necessary for purchasing land for thousands of milkweed patches, restoring the native ecosystems and performing annual maintenance to keep weeds out.

The monarch must be granted an emergency listing as a threatened species. In addition to buying and restoring the milkweed sites, the U.S. Fish and Wildlife Service and each state in the U.S. that the butterflies migrate through should approve a recovery plan and maps of the needed critical habitat areas. Anything less, and the monarch will go the way of another migrating species that we lost 100 years ago: the passenger pigeon.

Redwood City, Calif.


In the “Test Yourself” box in “Let the Games Continue,” by Colm Mulcahy and Dana Richards, the wording of the first puzzle, related to lightbulbs, was potentially misleading. In the sentence “then go to the third floor to see the bulb,” the text should have said “check” instead of “see.”