What better way to kick off the Ask Me Anything column at Hippo Reads, the new Santa Monica, CA-based publisher of academically inclined essays, than to put some cosmic questions about the shape of the universe and the feasibility of time travel to a theoretical physicist? And who better to serve as the inaugural Hippo Reads AMA respondent than a physicist who’s also an award-winning writer, teacher, and historian?
I speak, of course, of David Kaiser, Germeshausen Professor of the History of Science at MIT and Department Head at the Program in Science, Technology, and Society (the Knight program’s home department at MIT). In addition to his STS duties, Prof. Kaiser serves as a senior lecturer in MIT’s Department of Physics, where he co-leads a group with Prof. Alan Guth focused on inflationary cosmology, the events that occurred in the first few fractions of a second after the Big Bang. Hippo Reads assistant editor Benjamin Winterhalter tapped Prof. Kaiser for the AMA honor after seeing him on physicist Brian Greene’s recent NOVA special Fabric of the Cosmos.
Under the Ask Me Anything format, developed to a fine art by the social news site Reddit, notable people typically agree to respond to questions from community members. Most questions tend to be some variation on “what’s it like to be you” or “what do you think about social issue x, y, or z.” But that’s not at all the point of the Hippo Reads version of AMA. The editors put their goals this way:
This is your chance to explore everything you’ve ever wanted to know about a particular topic, but never had the chance (or audacity!) to ask. At Hippo, we’re always asking questions to which we don’t have the answers. We have a feeling our readership also has a lot of burning questions about the world. As such, we’ve created a new venue for you to ask your most pressing, most bizarre, most creative questions of a vetted Hippo academic.
It’s a great variation on the AMA idea—offering, as it does, one more way for thoughtful members of the public to engage directly with people on the front lines of science and engineering. Readers sent in a variety of questions for Prof. Kaiser, and the Hippo Reads editors narrowed them down to just four winners:
I understand the idea that forwards time travel is theoretically possible, but what about backwards time travel?
What shape is the universe?
If you get sucked into a wormhole, is it theoretically possible to get back out? If so, what would you use to escape?
They say the universe is always expanding. But what lies beyond the end of the universe, the space it has not yet expanded into?
Prof. Kaiser, who took time out from his sabbatical this semester to respond, lived up to the example of top science communicators like Greene, Neil de Grasse Tyson, and Carl Sagan by writing detailed yet literate and witty answers. (Highly detailed. Kaiser’s answer to the first question ran to almost 1,500 words.) I recommend you read the full AMA for the whole picture, but Kaiser’s four answers were basically as follows:
- Yes, backward time travel is theoretically possible (at least from one point of view).
- The universe is neither positively curved (closed like a sphere) or negatively curved (open like a saddle) but seems to have the critical “Goldilocks” density to yield zero curvature.
- You might survive a trip through a wormhole, but you’d have to tame dark energy first.
- It’s possible that there are other universes “outside” our own. Kaiser says he visualizes these other universes as bubbles in a huge bathtub, the “multiverse.” He writes:
Inside one of those bubbles, an observer would see a huge — in fact, infinite — space that is stretching larger and larger over time…Yet from outside the bubble, looking from some other point within the “bathtub,” we would see a bubble of perfectly finite size…we would see the bubble get larger over time — we would see the walls of the bubble move outward at the speed of light — but at any finite time the volume would remain less than infinity. This is a delicious example of how general relativity and warped spacetimes can play tricks with our intuitions. The coordinates that an observer would use inside the bubble-universe, which would best respect the symmetrical distribution of matter and energy within the bubble, would make the bubble appear to be infinite in extent, whereas an observer outside the bubble would see the walls of the finite-sized bubble expand into the neighboring, pre-existing, space of the bathtub-multiverse.
Got that? Me neither, but I’ve convinced Prof. Kaiser to explain it to me again over beers some evening.
The Hippo Reads AMA feature, which will doubtless cycle between experts in science and the site’s other focus areas such as art and literature, economics, government, history, medicine, philosophy, psychology, and religion, will be a fun new place for curious Web readers to interact with the site’s hand-picked experts. We’re proud that our own department head is paving the way.