By: Natalie Wolchover
Published: 04/13/2012 03:23 PM EDT on Lifes Little Mysteries
In this weekly series, Life's Little Mysteries provides expert answers to challenging questions.
Black holes are without question some of the strangest places in the universe. So massive that they hideously deform space and time, so dense that their centers are called "points at infinity," and pitch- black because not even light can escape them, it isn't surprising that so many people wonder what it would be like to visit one.
It's not exactly a restful vacation spot, as it turns out.
If you were to take a step into a black hole, your body would most closely resemble "toothpaste being extruded out of the tube," said Charles Liu, an astrophysicist who works at the American Museum of Natural History's Hayden Planetarium.
Liu said that when an object crosses a black hole's "event horizon" — its outer boundary, or point of no return — the same physics that causes Earth's ocean tides begins to take effect. Gravity's strength decreases with distance, so the moon pulls on the side of the Earth closer to it a bit more vigorously than the side farther from it, and as a result, Earth elongates ever so slightly in the direction of the moon. The land is sturdy, so it doesn't move much, but the water on Earth's surface is fluid, so it flows along the elongated axis. "That's the tidal interaction," he said.
Rising tides are about as calming a scene as there is. A human toeing the line of a black hole? Not so much. [What's at the Center of a Black Hole?]
Near a black hole roughly the size of Earth, tidal forces are magnified off the scale. Swan-diving into one, the top of your head would feel so much more gravitational pull than the tips of your toes that you would be stretched, longer and longer. "[The British astrophysicist] Sir Martin Rees coined the term 'spaghettification,' which is a perfectly good way to put it. You eventually become a stream of subatomic particles that swirl into the black hole," Liu told Life's Little Mysteries.
Because your brain would dissociate into its constituent atoms almost instantly, you'd have little opportunity to soak in the scenery at the threshold of an Earth-size black hole.
However, if you're dead-set on visiting a space-time singularity, we recommend going big; bigger black holes have less extreme surfaces. "If you had a black hole the size of our solar system, then the tidal forces at the event horizon … are not quite that strong. So you could actually maintain your structural integrity," Liu said.
In that case, you would get to experience the effects of the curvature of space-time, predicted by Einstein's general theory of relativity, firsthand.
"First of all, you approach the speed of light as you fall into the black hole. So the faster you move through space, the slower you move through time," he said. "Furthermore, as you fall, there are things that have been falling in front of you that have experienced an even greater 'time dilation' than you have. So if you're able to look forward toward the black hole, you see every object that has fallen into it in the past. And then if you look backwards, you'll be able to see everything that will ever fall into the black hole behind you.
"So the upshot is, you'll get to see the entire history of that spot in the universe simultaneously," he said, "from the Big Bang all the way into the distant future."
Not such a bad way to go, in the grand scheme of things.
Hubble's 20th anniversary image shows a mountain of dust and gas rising in the Carina Nebula. The top of a three-light-year tall pillar of cool hydrogen is being worn away by the radiation of nearby stars, while stars within the pillar unleash jets of gas that stream from the peaks. Credit: NASA, ESA, and M. Livio and the Hubble 20th Anniversary Team (STScI)
Credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA) Acknowledgment: W. Keel (University of Alabama, Tuscaloosa)
Credit: A. Caulet (ST-ECF, ESA) and NASA
Credit: NASA and The Hubble Heritage Team (STScI/AURA) Acknowledgment: Dr. Raghvendra Sahai (JPL) and Dr. Arsen R. Hajian (USNO)
Credit: NASA, ESA, F. Paresce (INAF-IASF, Bologna, Italy), R. O'Connell (University of Virginia, Charlottesville), and the Wide Field Camera 3 Science Oversight Committee
Image Credit: NASA, ESA and The Hubble Heritage Team (STScI/AURA) Acknowledgment: R. Sahai (Jet Propulsion Lab) and B. Balick (University of Washington)
Credit: NASA, Andrew Fruchter and the ERO Team [Sylvia Baggett (STScI), Richard Hook (ST-ECF), Zoltan Levay (STScI)]
Credit: NASA; ESA; Hans Van Winckel (Catholic University of Leuven, Belgium); and Martin Cohen (University of California, Berkeley)
Arp 274 is a trio of galaxies. They appear to be partially overlapping in this image, but may be located at different distances. Credit: NASA, ESA, M. Livio and the Hubble Heritage Team (STScI/AURA)
This youngest-known supernova remnant in our galaxy lies 10,000 light years away in the constellation Cassiopeia. The light from this exploding star first reached Earth in the 1600s. Image Credit: NASA and The Hubble Heritage Team (STScI/AURA) Acknowledgment: R. Fesen (Dartmouth) and J. Morse (Univ. of Colorado)
An onionskin-like structure of concentric dust shells surround a central, aging star. Twin beams of light radiate from the star and illuminate the usually invisible dust. Artificial colors show how light reflects off the particles and heads toward Earth. Credit: NASA and The Hubble Heritage Team (STScI/AURA) Acknowledgment: W. Sparks (STScI) and R. Sahai (JPL)
Credit: NASA, ESA, and the Hubble SM4 ERO Team
Credit: NASA, ESA, and the Hubble SM4 ERO Team
Plumes of glowing hydrogen blast from the central nucleus of M82. The pale, star-like objects are clusters of tens to hundreds of thousands of stars. Credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA) Acknowledgment: J. Gallagher (University of Wisconsin), M. Mountain (STScI), and P. Puxley (National Science Foundation)
Credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA) Acknowledgment: A. Nota (STScI/ESA)
A billowing tower of gas and dust rises from the stellar nursery known as the Eagle Nebula. This small piece of the Eagle Nebula is 57 trillion miles long (91.7 trillion km). Credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA)
Image Credit: NASA and The Hubble Heritage Team (STScI/AURA) Acknowledgment: Ray A. Lucas (STScI/AURA)
Credit: E.J. Schreier (STScI), and NASA
Credit: NASA and E. Karkoschka (University of Arizona)
Credit: NASA, ESA, and A. Riess (STScI/JHU)
Credit: NASA, ESA, SSC, CXC, and STScI
Image Credit: NASA, ESA, and The Hubble Heritage Team (STScI)
Credits for X-ray Image: NASA/CXC/ASU/J. Hester et al. Credits for Optical Image: NASA/HST/ASU/J. Hester et al.
Thousands of stars are forming in the cloud of gas and dust known as the Orion nebula. More than 3,000 stars of various sizes appear in this image. Some of them have never been seen in visible light. Credit: NASA,ESA, M. Robberto (Space Telescope Science Institute/ESA) and the Hubble Space Telescope Orion Treasury Project Team
Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)
Credit: NASA, ESA, P. Challis and R. Kirshner (Harvard-Smithsonian Center for Astrophysics)
Credit: NASA, ESA and J. Hester (ASU)
Credit: NASA, ESA, and E. Karkoschka (University of Arizona)
Credit: NASA, ESA, C.R. O'Dell (Vanderbilt University), M. Meixner and P. McCullough (STScI)
Credit: NASA and The Hubble Heritage Team (AURA/STScI)
The Cat's Eye Nebula, one of the first planetary nebulae discovered, also has one of the most complex forms known to this kind of nebula. Eleven rings, or shells, of gas make up the Cat's Eye. Credit: NASA, ESA, HEIC, and The Hubble Heritage Team (STScI/AURA) Acknowledgment: R. Corradi (Isaac Newton Group of Telescopes, Spain) and Z. Tsvetanov (NASA)
Science Credit: NASA, ESA, and B. Schaefer and A. Pagnotta (Louisiana State University, Baton Rouge) Image Credit: NASA, ESA, CXC, SAO, the Hubble Heritage Team (STScI/AURA), and J. Hughes (Rutgers University)
Bright knots of glowing gas light up the arms of spiral galaxy M74, indicating a rich environment of star formation. Messier 74, also called NGC 628, is slightly smaller than our Milky Way. Credit: NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration Acknowledgment: R. Chandar (University of Toledo) and J. Miller (University of Michigan)
Credit: H. Ford (JHU/STScI), the Faint Object Spectrograph IDT, and NASA
Credit: NASA, ESA, R. O'Connell (University of Virginia), F. Paresce (National Institute for Astrophysics, Bologna, Italy), E. Young (Universities Space Research Association/Ames Research Center), the WFC3 Science Oversight Committee, and the Hubble Heritage Team (STScI/AURA)
The Crab Nebula is a supernova remnant, all that remains of a tremendous stellar explosion. Observers in China and Japan recorded the supernova nearly 1,000 years ago, in 1054. Credit: NASA, ESA, J. Hester and A. Loll (Arizona State University)
A brilliant white core is encircled by thick dust lanes in this spiral galaxy, seen edge-on. The galaxy is 50,000 light-years across and 28 million light years from Earth. Credit: NASA and The Hubble Heritage Team (STScI/AURA)
Credit: NASA, ESA, STScI, J. Hester and P. Scowen (Arizona State University)
Credit: NASA, ESA, SAO, CXC, JPL-Caltech, and STScI Acknowledgment: J. DePasquale (Harvard-Smithsonian CfA), and B. Whitmore (STScI)
Credit: NASA, ESA, and Jonathan Nichols (University of Leicester)