Clif's Reviews > Black Holes & Time Warps: Einstein's Outrageous Legacy

I had read Einstein's book "The Evolution of Physics" (reviewed) and with the introduction that he supplied, felt I was ready to fall into black holes. I had seen a cover blurb describing Kip Thorne's book (subtitle: Einstein's outrageous legacy) as exemplary science writing and, though it is somewhat dated (1993) bought a used copy.

Thorne wastes no time, initially taking the reader on a visit to black holes of various sizes, though widely separated in distance, in our galaxy. Relativity is seen by the wildly different amount of time experienced by the astronauts compared to that on earth during their absence. A trip to the center of the Milky Way at light speed would only be 30 years for the voyagers but many thousands of years would pass on earth, many thousands more for the return trip!

This a result of what Einstein found - that time is relative. There is no independent time, alike for everyone everywhere. Only the speed of light is constant everywhere and always. It is this adjustment of our dimensions of height, width and depth to accord with the constant of light speed that results in the weird stretching and compressing of objects and of time.

The central theme of the book is gravity and what happens when it becomes far more powerful than we know it to be in our solar system. Even as early as the 18th century there was speculation about what would happen if a star was so massive that its gravity would prevent even light from escaping.

Thorne takes us on the investigation through physics that really took off after Einstein came up with the concept of spacetime, which is curved by gravity. Because spacetime is a dimension that we can never see, limited as we are to the 3 dimensions that we know, Thorne uses what are called embedding diagrams to give a sense of how curvature of spacetime can result in the three angles of a triangle summing to more or less than 180 degrees, or the shortest distance between two points not being a straight line as we would see it.

The best way I've found to think of spacetime is as follows: light must always follow the shortest path between two points and it must do so at the fixed speed of 186,000 miles per second. Einstein showed that light has mass, though very little, and is therefor affected by gravity.

The intense gravity of the sun is enough to bend the path of light that passes near it. If we look at the light of a star with high precision, we note that if the sun's edge passes near the position of that star, the star's light will be offset from where it would otherwise be, shifting the position of that star in relation to all the other stars seen in that part of the sky. As the sun moves away, the distant star appears to move back into its normal place.

Now, if light cannot change speed and must be coming to us from that distant star by the shortest path at all times, then it is the path, through Einstein's spacetime, that is distorted because of the sun's gravity. Were the sun a black hole, the distant star's light passing near it would be greatly displaced, just as the text in a book would be moved and distorted as you pass a magnifying lens over it.

Surprisingly, the author is able to make the strangeness he describes comprehensible. The idea that as stars become increasingly massive their fate takes them to different endpoints - white dwarfs, neutron stars and finally black holes, is clearly explained with many diagrams and side comments. I only had difficulty in the last chapter where he goes into time machines. There, the level of abstraction went where I could not follow, and abstraction is what the cutting edge of physics is all about.

You will get a great introduction to great minds in math and physics of the 20th century, many of them friends of Kip Thorne. There are plenty of personal accounts and a good bit of humor to humanize what might be a dry subject. There is excellent coverage of the instruments used, such as the radio telescope or the X-ray detecting satellites. Thorne does a great job of catching the reader up in the excitement of the professionally curious who are forever asking why.

Something I had not considered before, the author relates how traditional optical astronomy, starting with the naked eye, only reveals a relatively quiet universe. The rip-roaring world of X-rays, gamma rays and gravity waves cannot be "seen" without special instruments that have only been practical within the last 75 years. An exciting part of the book for me was the story of Grote Reber, a hobbyist in Wheaton, Illinois, who built his own backyard radio telescope and detected (with low precision) strong radio sources before professional astronomers knew about them. So impressive was his work that astronomers from the Yerkes Observatory traveled to visit him.

Thorne takes you across the electromagnetic spectrum, from light through radio and X-rays up to the latest area of investigation, non-electromagnetic gravity waves, being sought as the inevitable result of black holes in collision. Since Kip Thorne recommended the construction of the first gravity wave interferometer at Caltech, he's well placed to discuss the search. Because of the age of this book, I was curious to see what happened with this particular project, called LIGO. As it happens, it was built and operated for several years but detected no gravity waves. It has been dismantled and a successor instrument is about to take up the search.

Black holes are discussed in great detail, as you'd expect, but not as you'd expect the discussion can be followed without difficulty through the decades, as one great mind after another puts up an idea to be either upheld against fierce criticism or destroyed by the math of another. Behind it all lies Einstein's relativity that opened up a chapter on the search for truth by minds that have to model places in the universe where matter and energy take on magnitudes unknown to human experience.

I had to chuckle when Thorne would describe untold hours and even years of work being upset like this: After X had been working on the problem, trying to tie together the different loose ends, Z showed that, after all, everything could be explained by looking at the math in a different way, that, really, there was no difficulty after all. You can imagine the real storm and strife of egos behind a summary statement like this, with someone screaming, WHY DIDN'T I SEE THAT!

Join Kip Thorne for this inside story on what is real, though it may contradict our experience. There are more weird things in this book than in a carnival freak show, yet all of them have stood up to the best testing that has been devised.