How the Universe Works
SKU: 28438808168

How the Universe Works

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Description

How the Universe Works"This volume fills a gap between books for lay readers and books for serious students of cosmology. An undergraduate student seeking a big picture understanding of cosmology and an easy introduction to the mathematics involved will find this book very useful. Each section concludes with a helpful summary in question answer format. This is really useful in answering some questions and clarifying concepts that really do get addressed properly in the

"This volume fills a gap between books for lay readers and books for serious students of cosmology. An undergraduate student seeking a big picture understanding of cosmology and an easy introduction to the mathematics involved will find this book very useful. Each section concludes with a helpful summary in question-answer format. This is really useful in answering some questions and clarifying concepts that really do get addressed properly in the running prose format. Various lucid, simple graphs illustrate concepts throughout the text. A particularly refreshing aspect is the authors' respect for the reader's intelligence: they clearly admit where scientists still do not know the answers and at best can speculate."

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This book is about the history and the current state of the art in the exciting field of cosmology -- the science about the Universe as a whole, which is guaranteed to attract the attention of a wide range of readers. It mostly aims to explain the main ideas of modern cosmology: the expanding Universe, its creation in a Big Bang, its evolution, characteristics, and structure, as well as issues -- dark matter and dark energy, black holes and other exotic objects etc. It also answers most frequently asked questions about cosmology.

How the Universe Works stands between a popular science book and a textbook, acting as a sort of a bridge across the great chasm separating popular science from true science. It can be also used as an introductory textbook for undergraduate students. It is also suitable for the non-experts in cosmology who wish to have an overview of the current state of the field. It is different from most popular science books because it avoids cutting corners in explanations and contains justification for various assumptions or estimations made in cosmology. It does not hide problems faced by modern cosmology as well as issues the community has no consensus about. It also does not try to pass hypotheses for established theories, which is not uncommon in scholarly articles.

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SKU: 28438808168

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4.7 ★★★★★
Based on 332 reviews
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Verified Purchase
Shanna S.
New York, US
★★★★★ 4
Looooves her crazy new ball
Color: Orange, Color: Orange
Our 90lb mastiff/boxer mix Indie is very playful, curious and energetic. She needs toys that engage her and keep her busy. This ball does the job! We’ve had it for less than a week. Here’s what I love and what could be better: PROS: • She dog loves it. She whines for it. She gets absurdly excited when I get it out. She’s a bit of an anxious dog, but had zero problems with it inexplicably coming to life. • It lasts a while on a single charge, so it keeps her busy for a good long time. The longest we’ve used it at a stretch is an hour. • It’s pretty durable. She’s a super chewer (destroyed every “non-destructible” toy we’ve purchased for her), but the actual ball is hard plastic. She gnaws on it and it gets scratches, for sure. But she’s not going to chew it to pieces. • On carpet, it’s reasonably quiet. • It comes with a replaceable silicone button. • It’s easy to charge…just pull off the silicone button and the charging port is inside. • The silicone button is flush with the ball’s hard plastic surface, so there’s no way for her to pull the silicone button out and swallow it or get to the charging port. CONS: • Cover is worthless if your dog is a chewer. It goes on like an envelope with a Velcro closure. We took it off immediately. • Without the cover, it’s very noisy on hardwood floors. To us, it’s worth it. (Though, I work from home, so I might feel differently after the holiday vacation.) • She’s an XL dog, so she can fit the whole ball in her mouth easily and accidentally chomp down on the button and turn the ball off. Not a big deal, just something to know if you’ve got a Lab or larger dog. • With extended playtime, the two halves can come unscrewed, especially with a large dog who uses their paws/jaws on it a lot. Thankfully, it makes a loud buzzing noise when this happens, so we know we need to take it from her and screw it back together. Is this a potential danger? With the rechargeable battery inside, I’d say yes. But we also don’t let her play with this toy without supervision. So keep that in mind. Bottom line: It has its drawbacks, but it keeps her entertained and seems like it should last her at least 6 months with supervised play. Which is honestly REALLY good when we’re talking about Indie, Destroyer of Toys. I’d buy it again.
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Reviewed in the United States on December 31, 2024
T
Verified Purchase
T. Bock
Los Angeles, US
★★★★★ 3
Difficult/impossible to unscrew plastic cups (in order to recharge the vibrating/blinking device)
Color: Orange
Generally, I don't leave feedback on items purchased. However, in this case, I feel compelled to do so in hopes the mechanical engineers (of this product) will take my input to heart and ultimately modify it. First the pros... - I have 2 high-energy dogs (Jack Russell Terriers) who love their toys (e.g., chewing bones, tug-of-war, etc.) but usually get bored with them rather quickly. - This interactive PetDroid ball, however, keeps them busy for a long time. - In fact, my smaller dog (Max) knows its storage location and sits (as early as 6 AM) in front of the cabinet so that I give him "his ball". It keeps him busy for up to 1-2 hours at a time. - Max is literally addicted to the PetDroid ball... his determinant play with it makes me laugh all the time. Now, the cons... - After several days of play, the exterior looks chewed up quite a bit. That's no problem though. - Unfortunately, the interior "threads/grooves" of the two plastic cups (for closing/fasting) are very tiny. - Thus, after an hour-long hard play, it is almost impossible to unscrew the 2 plastic cups in order to recharge the interior device. - It appears the 2 cups somehow come off track and get realigned from the inside. - At that point, I cannot unscrew the PetDroid ball in order to recharge the device.... and without the blinking/vibration, this toy is no longer fun for play. - Ultimately, I had to place the bottom half of the ball into a vise and then use a plumbing wrench to untwist it. Proposed Solution: - Increase the size of the plastic cups' interior threads/grooves so that they won't get realigned/come off track. - This would mitigate the current dilemma of NOT being able to unscrew the ball in order to recharge it. In my view, this should be a relatively simple fix and significantly improve the durability of this product. Thank you for your time.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on February 4, 2022
S
Verified Purchase
Scott L.
Bozeman, US
★★★★★ 5
Good fun and entertaining!
Color: Orange
A really fun interactive toy for your dog! It's pretty erratic and really gets him chasing it. The included soft cover was kinda hard to install and then it's hard to turn it off and on with the cover on, I feel like the cover didn't really improve it at all, sure it's louder without the cover but I feel like dog also likes it that way, he likes loud squeaky toys and this thing making a bunch of noise is appealing to him. We have mostly hardwood floors so it really gets moving, I'm sure on carpet it would be a bit quieter and maybe even a bit slower to move around but on hard smooth surfaces this things can really get zipping around abd get some speed to make him chase it. Overall a fun and entertaining toy.
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Reviewed in the United States on January 27, 2026
B
Verified Purchase
bill a.
Whiting, US
★★★★★ 5
Awesome
Color: Orange
Awesome Toy . My Jack is crazy over it. She usually get bored with others, but this toy still has her attention after a couple of weeks Runs a long time on a short charge. 👍🏻
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Reviewed in the United States on May 30, 2026
C
Verified Purchase
Chad
Alexandria, US
★★★★★ 2
Not the Fetch-Fest I Hoped For
Color: Orange
I had high hopes for the PetDroid Interactive Dog Ball, especially with the newly upgraded features and promises of durable, motion-activated fun. Unfortunately, it didn’t quite live up to expectations for my furry friend. Here’s why I’m giving it 2 stars. Promising Features, Lackluster Results The idea behind this toy is fantastic: a durable, motion-activated ball that would entertain my dog without much effort on my part. The ball is supposed to roll around on its own, keeping my dog engaged and active. However, in practice, it just didn’t capture my dog’s interest. Durability I will give credit where it’s due: the ball is well-made and seems durable. It can withstand some rough handling, which is great for more aggressive chewers. Unfortunately, durability doesn’t mean much if your dog won’t play with it in the first place. Motion Activation The motion activation feature is hit or miss. While the ball does move around as advertised, it didn’t seem to move in a way that intrigued my dog. He gave it a sniff, watched it for a minute, and then walked away, unimpressed. I tried multiple times to get him interested, but he simply wasn’t having it. Lack of Engagement The biggest issue is that the ball just didn’t engage my dog at all. It might be more suitable for a different personality type or breed, but for my pooch, it was a total flop. He’s usually quite playful and curious, so I was surprised by his lack of interest. Final Thoughts Overall, the PetDroid Interactive Dog Ball might work for some dogs, but it was a miss for mine. If your dog is easily entertained by automated toys, it might be worth a try. However, based on my experience, I can’t wholeheartedly recommend it. Pros: Durable construction Motion-activated as advertised Cons: Did not engage my dog Motion activation wasn’t intriguing enough Might be more suitable for specific dog types or personalities If you decide to give it a shot, just be prepared for the possibility that your dog might not find it as entertaining as you hope. For us, it’s back to the drawing board for a more engaging toy.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on June 14, 2024

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