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Space, Time, Matter"The standard treatise on the general theory of relativity." Nature "Whatever the future may bring, Professor Weyl's book will remain a classic of physics." British Journal for Philosophy and Science Reflecting the revolution in scientific and philosophic thought which accompanied the Einstein relativity theories, Dr. Weyl has probed deeply into the notions of space, time, and matter. A rigorous examination of the state of our knowledge of the world
"The standard treatise on the general theory of relativity." -- Nature"Whatever the future may bring, Professor Weyl's book will remain a classic of physics." -- British Journal for Philosophy and Science
Reflecting the revolution in scientific and philosophic thought which accompanied the Einstein relativity theories, Dr. Weyl has probed deeply into the notions of space, time, and matter. A rigorous examination of the state of our knowledge of the world following these developments is undertaken with this guiding principle: that although further scientific thought may take us far beyond our present conception of the world, we may never again return to the previous narrow and restricted scheme.
Although a degree of mathematical sophistication is presupposed, Dr. Weyl develops all the tensor calculus necessary to his exposition. He then proceeds to an analysis of the concept of Euclidean space and the spatial conceptions of Riemann. From this the nature of the amalgamation of space and time is derived. This leads to an exposition and examination of Einstein's general theory of relativity and the concomitant theory of gravitation. A detailed investigation follows devoted to gravitational waves, a rigorous solution of the problem of one body, laws of conservation, and the energy of gravitation. Dr. Weyl's introduction of the concept of tensor-density as a magnitude of quantity (contrasted with tensors which are considered to be magnitudes of intensity) is a major step toward a clearer understanding of the relationships among space, time, and matter.
Binding Type: Paperback
Publisher: Dover Publications
Published: 06/01/1952
ISBN: 9780486602677
Pages: 368
Weight: 0.79lbs
Size: 8.01h x 5.44w x 0.72d
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★★★★★ 5
Fun Dog Toy
Color: Orange - 3.15Inch, Color: Orange - 3.15Inch
My Goldendoodle loves this ball! It’s the perfect size, easy to carry, and keeps her busy for a long time. Great purchase.
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Reviewed in the United States on June 10, 2026
★★★★★ 5
Orange Ball Endless Dog Zoomies
Color: Tangerine - 3.15Inch
My dog was immediately curious about this ball, and it quickly turned into one of the toys that gets pulled out multiple times throughout the day. The movement keeps things interesting and encourages chasing in a way that a regular ball doesn’t. I like that it keeps my dog occupied when the weather isn’t great for long outdoor play sessions. The textured surface provides a decent grip when carrying it around the house. It has bounced off furniture and walls a few times and still looks surprisingly good afterward. The size worked well for my medium-sized dog and was easy for him to grab. There were a couple moments where it got stuck in tight spaces, but that’s more a result of enthusiastic play than a problem with the toy itself. The activity level definitely increased when this ball started moving around. It’s been a fun way to add a little extra excitement to indoor playtime.
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Reviewed in the United States on June 10, 2026
★★★★★ 5
Easy to charge and bounces nicely on the grass
Color: Tangerine - 3.15Inch
Getting the kids' backpacks ready usually means the dog gets ignored for a bit and starts pacing. I turn this ball on and toss it out the back door. It has a surprising amount of bounce on the grass, and the random movements keep him running circles trying to catch it. Pushing the button to switch the rolling modes is straightforward. The battery gets me through a few play sessions before it needs to be plugged back in. The outer shell gets pretty dirty outside, but wiping it down with a damp rag cleans it right up. It’s got a decent weight to it, so it doesn't just get stuck under the lawn chairs immediately.
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Reviewed in the United States on June 12, 2026
★★★★★ 1
Beware of poor quality issues!
Color: Orange - 3.15Inch, Color: Orange - 3.15Inch
Got limited use out of ball, seemed to have quite a strong motor and was going to be a good buy. But upon going to recharge it for the first time, discovered the USB port was completely loose/not attached. Will steer clear of this brand going forward.
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Reviewed in the United States on May 26, 2026
★★★★★ 5
The Ball Never Gets Boring
Color: Tangerine - 3.15Inch
My dog was immediately curious about this ball, and that curiosity turned into a surprisingly long play session. The movement keeps things unpredictable enough that it holds attention longer than a standard toy. I liked that it encouraged activity without requiring me to constantly throw something across the room. The textured surface also seemed easy for my dog to grab and carry around. One thing I noticed is that hard floors allow the ball to move around much more dramatically than carpet. It feels sturdy enough to handle enthusiastic play and occasional chewing. The bright color makes it easy to spot when it inevitably ends up under furniture. Charging was simple and didn’t become a hassle.
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Reviewed in the United States on June 13, 2026