Compare Our Picks

Others Tested

Sakara Life; starts at $141 per week; up to $465 for specialty programs: This plant-based, gluten-free meal kit reminds me of what most people think when they think of “crunchy” vegan food—raw vegetables with an earthy taste. Nearly all meals in Sakara’s lineup are uncooked and preprepared—items like veggie burgers are without buns, lasagnas are “deconstructed.” For example, a “Lavender Quesadilla” has broccoli pesto and cashew “cheese” with hibiscus salsa … you get the idea. The menu is curated each week, and meals come in single servings. Sakara also has health supplements (which can be scientifically dubious), like a metabolism booster and fulvic acid cell reset. Sakara’s signature nutrition program meal plan is designed to replace all meals and is delivered twice weekly. If you buy one week of five days, three meals a day, it’s $465 per week; weekly subscriptions of five days, three meals a day, is $395 per week; prices go down to $141 per week with a 12-week subscription for three days at two meals per day. There’s also a “Level II: Detox” program, starting at $465 per week. This meal kit seems fit for Gwyneth Paltrow or WAGs (wife or girlfriend of professional athletes) everywhere, but it wasn’t the right fit for my budget and taste preferences.

NutriFit

NutriFit for $10 to $45 per meal: NutriFit is more like a personal chef than a meal-kit delivery service, specializing in nutrient-dense, fully prepared meals with a huge range of fare, with gluten- and dairy-free and vegetarian and vegan options. The company ships to the lower 48 states, and most meals hovered around $20. NutriFit has customized, chef-curated meal plans that are tailored for the eater and include specifics like health goals and dietary restrictions, where the customer can select their own meals on the Premium plan or have the curated meals from the 13-week rotating menu, starting at $19 per day. There are also à la carte options, which I tested, which range from $10 to $45 per meal. These don’t require a subscription or a minimum, and come in meals that serve three to four people or in individual size Fit for ONE meals that feed one, where you choose from “Always Available Favorites” and rotating new specials. A lentil chickpea salad, cold udon noodles, hearty roasted tomato soup, and crispy vegan tacos were standouts. But I wasn’t a huge fan of most of the chef-curated specials, and the food started to wilt or get mushy if not eaten within the first few days. The user interface of the service isn’t the best or easiest to navigate, either.

Photograph: Molly Higgins

Fresh! Meal Plan from $11 to $14 per meal: You can choose from 6, 10, or 14 meals per week, or order à la carte (which is a minimum of eight meals), ranging from $11 to $14 per meal, with the price lowering the more you order. It’s got choices for keto, paleo, high-protein, dairy- and gluten-free, and vegan and vegetarian meals, and everything is preprepared and just needs to be microwaved (or air fried) for about three minutes. There were six vegan meals and four vegetarian meals at the time of writing, with a menu filter to easily see choices. The vegetarian coconut chia breakfast pudding and margherita breakfast pizza were standouts, the vegan crab cakes had a mushy consistency and almost cinnamon-like flavor, and the vegan blackened “chickn” and Cajun pasta was rubbery and lacked spice. Since testing several months ago, none of the plant-based meal choices has changed, so this may be best as a supplemental meal kit for plant-based eaters.

Not Recommended

Photograph: Molly Higgins

Eat Clean for $9 to $13 per meal: This vegan meal delivery service would be best for someone who loves the taste and convenience of TV dinners. Eat Clean has a dozen plant-based heat-’n’-eat meals available, with availability to order six to 20 meals per week, ranging from six meals for $13 each to 20 meals at $9 each. Each meal comes in a plastic container and needs to be microwaved or heated for around three minutes. Many of the meals have very similar flavors—the tomato sauce base for the chili, spaghetti, and lasagna all tasted the same. The meals with sides often felt random: zucchini with mac and cheese and nuggets; a cornbread on the side of chili that tasted exactly like a cinnamon coffee cake (the flavors didn’t go well together on that one). Like TV dinners, flavors were often one-note, and I opted to air fry to enhance mushy textures. This meal kit is nearly the same price as most I’ve tested, and the picks above are a whole lot tastier.

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The original version of this story appeared in Quanta Magazine.

Standing in the middle of a field, we can easily forget that we live on a round planet. We’re so small in comparison to the Earth that from our point of view, it looks flat.

The world is full of such shapes—ones that look flat to an ant living on them, even though they might have a more complicated global structure. Mathematicians call these shapes manifolds. Introduced by Bernhard Riemann in the mid-19th century, manifolds transformed how mathematicians think about space. It was no longer just a physical setting for other mathematical objects, but rather an abstract, well-defined object worth studying in its own right.

This new perspective allowed mathematicians to rigorously explore higher-dimensional spaces—leading to the birth of modern topology, a field dedicated to the study of mathematical spaces like manifolds. Manifolds have also come to occupy a central role in fields such as geometry, dynamical systems, data analysis, and physics.

Today, they give mathematicians a common vocabulary for solving all sorts of problems. They’re as fundamental to mathematics as the alphabet is to language. “If I know Cyrillic, do I know Russian?” said Fabrizio Bianchi, a mathematician at the University of Pisa in Italy. “No. But try to learn Russian without learning Cyrillic.”

So what are manifolds, and what kind of vocabulary do they provide?

Ideas Taking Shape

For millennia, geometry meant the study of objects in Euclidean space, the flat space we see around us. “Until the 1800s, ‘space’ meant ‘physical space,’” said José Ferreirós, a philosopher of science at the University of Seville in Spain—the analogue of a line in one dimension, or a flat plane in two dimensions.

In Euclidean space, things behave as expected: The shortest distance between any two points is a straight line. A triangle’s angles add up to 180 degrees. The tools of calculus are reliable and well defined.

But by the early 19th century, some mathematicians had started exploring other kinds of geometric spaces—ones that aren’t flat but rather curved like a sphere or saddle. In these spaces, parallel lines might eventually intersect. A triangle’s angles might add up to more or less than 180 degrees. And doing calculus can become a lot less straightforward.

The mathematical community struggled to accept (or even understand) this shift in geometric thinking.

But some mathematicians wanted to push these ideas even further. One of them was Bernhard Riemann, a shy young man who had originally planned to study theology—his father was a pastor—before being drawn to mathematics. In 1849, he decided to pursue his doctorate under the tutelage of Carl Friedrich Gauss, who had been studying the intrinsic properties of curves and surfaces, independent of the space surrounding them.

After-Christmas deals are an excellent way to redeem any gift cards or cash you got for Christmas. You can purchase something you actually want, and you can do it for less money than usual. I’ve scoured the Internet for truly good after-Christmas deals on the gear that we’ve hand-tested on the WIRED Reviews team. Many of these sales will end this weekend, so keep that in mind while you’re shopping. Find all the highlights below.

For more inspiration, check out some of our recently updated buying guides, including the Best Office Chairs, the Best Cheap Phones, and the Best Space Heaters.

WIRED Featured Deals:

Anker Laptop Power Bank for $88 ($47 off)

We love this beefy power bank. Its 25,000-mAh capacity is more than enough for fully charging your iPhone between 4 and 6 times, and it can deliver up to 165 watts to two devices meaning that you can charge your laptop, gaming console, or anything else you fancy. The built-in USB-C cable doubles as a carrying loop. There’s also a nifty display that’ll give you at-a-glance information on remaining battery, temperature, charging speeds, and more. It has pass-through charging support and only takes about two hours to fully recharge. This deal price matches what we saw on Black Friday.

Google Pixel 10 for $599 ($200 off)

There was an on-page coupon (PIXEL10) that had the best price we’ve tracked for any of the phones in the Google Pixel 10 lineup. That coupon is not available as of Saturday morning, but it may be back—clip it if you see it. This is still a good deal on the smartest Android phones you can buy, with fantastic cameras, snappy processors, gorgeous displays, and more AI integration than the average person needs. Check out our dedicated buying guide to figure out which Google Pixel 10 is right for you. If you’re in the market for an upgrade, now is a good time to buy considering that we’ve never seen any phone in this flagship lineup sell for less.

Bruvi BV-01 Brewer Bundle for $228 ($120 off)—Clip the Coupon

Photograph: Louryn Strampe

I’ve tested a lot of pod coffee makers, and the Bruvi BV-01 is my favorite. This deal price is the best we see outside of special events like Black Friday and Cyber Monday. The brewer is cute and looks great on a counter, with a large reservoir, an intuitive touchscreen display, and a built-in wastebin that collects used pods for you. The best part are the proprietary B-Pods, which are designed to biodegrade in a landfill. The bundle gets you the machine plus an assortment of bestselling coffee and espresso pods to get you started.

Fitbit Charge 6 for $100 ($60 off)

The Fitbit Charge 6 has been at the top of our fitness tracker buying guide since we first tested it. It’s attractive, affordable, accessible, and on sale for a match of the best deal we’ve seen. It’ll play well with iOS and Android, and it has a solid suite of features that’ll cover almost anyone’s needs—including skin temperature, heart rate readings, ECGs, activity and workout tracking, and more. The battery lasts for at least a week on a single charge. This deal comes with a six-month subscription to Fitbit Premium, which normally costs $10 per month.

Hydro Flask Standard Mouth Water Bottle for $30 ($10 off)

Photograph: Dick’s Sporting Goods 

Hydro Flask

Standard Mouth Water Bottle

This budget-friendly deal gets you a steal on the best reusable water bottle. Hydro Flask bottles are durable, portable, and easy to cover in all the stickers you’ve been hoarding. The handle is flexible, the bottle is leakproof, and every component is dishwasher safe (though you may want to opt for hand-washing if you do end up plastering it in stickers). A few different colors are on sale at this price.

Beats Powerbeats Pro 2 for $200 ($50 off)

If hitting the gym is one of your New Year’s resolutions for 2026, the Beats Powerbeats Pro 2 are worth considering. They’re the best workout headphones we’ve tested thanks to their comfortable and ergonomic fit, noise cancelation, spatial audio, a heart rate monitor, and the fact that they play well with both iOS and Android phones. The sound is solid, the battery life is good, and they’re water-resistant. This deal price comes within $20 of the best we’ve seen. Every color—orange, lavender, grey, and black—is on sale.

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