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I originally published this recipe in 2022, and I’ve since updated it with additional success tips to help guarantee perfectly thick and creamy frosting.

Enjoy Creamy, Lightly Sweet Whipped Frosting

Today’s recipe can be titled many things, including whipped frosting, creamy lightly sweetened frosting, whipped cream frosting that pipes well, won’t-give-you-a-toothache-frosting, etc. I settled on Not-So-Sweet Whipped Frosting so you understand the selling point as soon as you read the title… this is a whipped frosting that isn’t too sweet. 😉

This frosting is, more or less, a very sturdy whipped cream. Think of a thicker, fluffier version of soft whipped cream. Even though it’s thick, it’s still pretty light and airy. There’s something known as stabilized whipped cream and today’s recipe could fall into that category, but it does contain cream cheese so there’s a little extra flavor.

You can pipe this whipped frosting on cupcakes, spread on cakes or ice cream cake, or even use between layers of pastry in homemade mille-feuille. If you’ve made this cookies and cream cake before, you’ve made a version of today’s frosting!

One reader, Erika, commented: “I wanted an alternative to buttercream, which always seems overly sweet and heavy. This came out amazing. I followed the directions exactly and it came out so silky smooth and light. ★★★★★“

One reader, John, commented: “This is the best ‘whipped’ frosting recipe I have ever made. I was cautious to make it about a year ago for my daughter’s birthday cake, but I went ahead and tried it. I was not let down. EVERYONE LOVED IT. I have not bought store-made frosting since. I have used it at least half a dozen times and it has been a hit every single time. I have been asked by multiple people for the recipe. The great part is that it’s not a difficult recipe. In addition, you make it very easy to follow, so thank you for that. I look forward to using this for years to come. ★★★★★“

Whipped Frosting Details

• Texture: Light, airy, fluffy
• Flavor: A little tangy and flavored with vanilla
• Sweetness: Less sweet than buttercream
• Difficulty: Easy
• Time: 10 minutes
• Best For: Cupcakes, cakes, fruit desserts
• Key Tip: Use cold ingredients for best volume

I especially love this whipped frosting with soft cakes that have strong flavor such as lemon blueberry cake, pumpkin cake, and citrus cake. You can’t really taste the cream cheese, but if you really dislike cream cheese, you may be able to detect it. (A few taste testers had no idea there was cream cheese in the frosting!)

If you love the consistency and structure of Swiss meringue buttercream, but are looking for something simpler, this whipped frosting is a prime choice. It’s probably the easiest frosting you’ll ever make because even if you mess up, there’s likely a solution to fix it. All you’re doing is mixing the ingredients together in a particular order at various speeds.

Even though this recipe is easy, I want to set you up for success by giving you all the information you need to get started. Review these headnotes because they will help you understand the best ingredients to use and the target consistency you need.

This Whipped Frosting Has 4 Ingredients

And with only 4 ingredients, it’s imperative you use the correct ones!

1. Room-Temperature Full-Fat Brick Cream Cheese: Cream cheese is the magical ingredient because it acts as the sturdy, structured base. Make sure you use full-fat brick-style cream cheese, not cream cheese spread in a tub or reduced-fat cream cheese. It must be softened to room temperature so you can successfully rid any lumps. You need 6 ounces (170g), which is a little less than one 8-ounce brick.
2. Confectioners’ Sugar: Confectioners’ sugar sweetens the frosting and compared to many frosting recipes like vanilla buttercream, you need a fraction of the amount to produce the same volume of frosting. Wow!
3. Vanilla Extract: Vanilla extract adds flavor. If you want to get started or already have some going, homemade vanilla extract is fantastic in this whipped frosting. Vanilla bean paste is also wonderful.
4. Cold Heavy Cream: Emphasis on the COLD temperature. You may remember this from making regular whipped cream, but the colder the heavy cream, the easier and more successfully it will whip. Make sure you use cream labeled heavy cream, heavy whipping cream, or double cream. All contain 36% or higher milkfat. Whipping cream (without “heavy” in the title) is a little lighter, with 30% milkfat. Do not use that because your frosting will never firm up.

By the way, this recipe is very easy to scale up or down. Use 2 ounces (57g) of cream cheese per 1/4 cup (30g) confectioners’ sugar and 1/2 cup (120g/ml) heavy cream. Add more or less vanilla extract. When you’re whipping in the heavy cream, reduce or extend that length of time based on the volume. Whip for less time if you scaled down the recipe and whip longer if you scaled up the recipe.

If you’re looking for a lighter topping, I recommend regular whipped cream. For a sturdy, yet lightly sweetened frosting, try Swiss meringue buttercream. If you need a whipped buttercream, use the frosting found with this vanilla sheet cake. Or search for whipped frosting made without cream cheese—some recipes use cornstarch or instant pudding mix instead.

Let’s Make Whipped Frosting!

In terms of preparation, the recipe reminds me of no-bake cheesecake. We’re using mostly the same ingredients found in the filling, except that recipe instructs you to whip the cream cheese and heavy cream separately. Here, we’re doing it all in 1 bowl in different stages.

First, beat the cream cheese to begin breaking it down and smoothing it out. You can use a hand mixer or a stand mixer with a whisk attachment.

Then add the confectioners’ sugar and vanilla extract and beat together. You really want to rid all the lumps:

Now here comes the *magic*!

Turn the mixer on low speed and add a few Tablespoons of the cold heavy cream. Once that’s fully incorporated and the mixture has smoothed out again, slowly—in a steady stream—pour in the rest of the cream. After all the cream has been added, turn the mixer up to high speed and watch your new favorite frosting fill with air and rise up in the bowl.

You’re looking for a thick, airy consistency with stiff peaks. If you were to shimmy and shake this bowl, the frosting would hardly move:

Now let me show you what not to do.

Too Thin vs Too Thick

Too thin: If you do not whip the mixture long enough, you’ll have soft, soupy, thin frosting. If you were to shake a bowl of under-whipped frosting, it will jiggle all around like a jello mold. This is an easy fix—just keep whipping until you have the consistency above.

Too thick: If you over-whip the frosting, it will appear chunky and curdled. While my fix isn’t perfect, it will certainly help: Stir in a splash of cold heavy cream, a Tablespoon at a time, by hand with a spatula or wooden spoon until the frosting smooths out again.

Whipped Frosting: 4 Success Tips (Do Not Miss These!)

1. No lumps in cream cheese. Be sure to start with room-temperature cream cheese. Cold cream cheese will give you stubborn lumps. While you can over-whip the frosting after you add the heavy cream, you cannot over-mix the first 3 ingredients in the recipe. Beat the cream cheese, confectioners’ sugar, and vanilla extract together for as long as you need to rid all of the cream cheese lumps. Stop and scrape down the mixing bowl as needed.
2. Add the heavy cream gradually. Start by beating in just a few Tablespoons of the cream, until the mixture smooths and thins out. Then pour in the remaining cream very slowly while the mixer runs on low speed.
3. Don’t leave. After you’ve added all the cream and increased the mixer speed, do not walk away. The frosting could set up in 1 minute or it could take closer to 5 minutes. Keep your eyes on the mixture to avoid over-whipped frosting.
4. Pop the air bubbles if needed. After you make the whipped frosting, you’ll notice that the consistency can change the longer it sits in the bowl. The frosting can develop more air bubbles; if you want the silky, yet thick consistency back, stir the frosting by hand a few times to deflate the air. I don’t notice this as much when the frosting sits on a finished cake and that’s likely because you handled it a lot in the frosting process—the bubbles develop most when the frosting is just sitting in the bowl before you use it. Likewise, if you notice the frosting looks really airy or over-whipped as you pipe it, either “massage” the frosting while it’s in the piping bag (sounds weird, but this can help deflate air bubbles) or pipe back into the mixing bowl and gently stir it.

The success of this recipe depends on the ingredients used and length of time mixing. Follow the recipe below carefully. It’s so nice to have an easy sturdy frosting that isn’t too sweet!

Pictured below: my soft and springy white cake with today’s whipped frosting. Dessert perfection!

Can I make whipped frosting ahead of time?

Yes, but whipped frosting is really best used the same day. You can prepare and store the whipped frosting in the refrigerator for up to 2 days. If needed, re-whip the frosting to smooth it out before using.

Why isn’t my whipped frosting thickening?

If your frosting is soupy and not thickening, the likely culprits are that your heavy cream is not cold enough, you poured in the cream too quickly/all at once, and/or that it hasn’t been whipped long enough. Also, be sure you’re using cream that’s at least 36% milkfat, as well as full-fat cream cheese.

Can I pipe with whipped frosting?

Absolutely! When whipped to stiff peaks, this whipped frosting holds its shape well for piping.

Is whipped frosting stable?

Whipped frosting is less stable than traditional American-style buttercream and therefore should be refrigerated.

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Description

Made from only 4 ingredients, this lightly sweetened whipped frosting is creamy and fluffy, yet holds its shape when piped with a piping tip. For best results, review the success tips above and recipe Notes below before you begin.

• 6 ounces (170g) full-fat brick cream cheese, softened to room temperature
• 3/4 cup (90g) confectioners’ sugar
• 1 and 1/2 teaspoons pure vanilla extract
• 1 and 1/2 cups (360g/ml) cold heavy cream or heavy whipping cream (very cold!)

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1. In a large bowl using a handheld or stand mixer fitted with a whisk attachment, beat the cream cheese on medium speed until creamy, about 1 minute. Scrape down the sides and bottom of the bowl and beat again as needed until completely smooth (no lumps). Add the confectioners’ sugar and vanilla extract, and beat on medium speed until combined and completely smooth, at least 2 full minutes. Scrape down the sides and bottom of the bowl and beat again as needed.
2. Add a few Tablespoons of the cold heavy cream, and beat until the mixture smooths and thins out. Scrape down the sides and bottom of the bowl as needed. Then, with the mixer running on low speed, pour in the remaining cream in a very slow and steady stream. After all of the cream has been added, increase the speed to medium-high and whip until stiff peaks form, about 2–4 minutes. This time can vary depending on exact temperature of ingredients, temperature in the kitchen, and even the humidity. Do not walk away during this time and do not be concerned if your frosting takes less or more time to whip. You’re looking for a thick, airy consistency with stiff peaks. If you were to shimmy and shake your bowl, the frosting would hardly move. If your frosting appears curdled, it’s over-whipped. To fix, stir 1 Tablespoon of heavy cream into the frosting by hand with a spatula to smooth out again. 
3. After you make the whipped frosting, it’s ready to frost your cupcakes, cake, or other confections. After frosting a cake or cupcakes with this frosting, I strongly recommend refrigerating them uncovered for at least 30 minutes to help “set” the frosting (especially when using on a layer cake). Then you can serve or set out for a couple hours before serving. And note that you’ll notice the frosting becomes thicker and airier the longer it sits in your mixing bowl. This is not a problem and can easily be fixed by gently stirring it to pop any air bubbles. Likewise, if you notice the frosting is really airy and looking over-whipped as you pipe it with piping tips, either “massage” the frosting while it’s in the piping bag to help deflate air bubbles, or pipe back into the mixing bowl and gently stir it with a spatula. You can stir in a splash of cold heavy cream to smooth out if needed.
4. Serve or Make Ahead: After the 30 minutes of refrigerating to “set” the frosting as instructed in step 3, frosted confections are fine to serve or sit out at room temperature for a couple hours. If you plan to serve later than that, such as the next day, I recommend storing in the refrigerator. Lightly cover as best you can (a cake carrier/cupcake carrier works great for storing). Confections topped with this frosting can be made ahead and refrigerated for up to 2 days.

Notes

1. Freezing Instructions: This whipped frosting freezes and thaws surprisingly well. For best results, I recommend freezing the frosting after you’ve already frosted your cake or cupcakes—as opposed to freezing the frosting in your mixing bowl or other container. Frost your baked good(s), refrigerate for at least 1 hour to set the frosting, and then cover and freeze for up to 3 months. (Note that covering this frosting can get messy and I haven’t found a workaround for that.) Thaw your frosted baked good(s) at room temperature or in the refrigerator.
2. Special Tools (affiliate links): Electric Mixer (Handheld or Stand) | Piping Bag (Disposable or Reusable) | Wilton 1M Piping Tip
3. Can this frosting sit out at room temperature or in a warm environment? A couple hours at room temperature is fine. If you’re serving your frosted confections outside on a hot day (I’ve done this a few times), refrigerate your frosted cake/cupcakes for up to 1 day. Remove from the refrigerator 30–60 minutes before serving them. This way they start out a little colder and can last longer in the heat.
4. Can I leave out or replace the cream cheese? No. See notes above. Instead, I would try a different recipe like regular whipped cream, Swiss meringue buttercream, or this whipped buttercream.
5. Can I tint this frosting a color? Yes. This frosting holds onto food coloring nicely and I strongly recommend using gel food coloring or natural food coloring powder. If you plan to tint the frosting, it’s best to add the food coloring when you add the heavy cream. If you need to add more food coloring after the frosting is done, gently stir it in by hand. If the frosting becomes too thick, stir in a splash of heavy cream to thin out again.
6. Can I flavor this frosting? Yes. Feel free to replace up to 1 teaspoon of vanilla extract with another extract of choice such as lemon or coconut extract. If it’s a potent extract such as peppermint extract, I would only use 1/2 teaspoon. You can also turn this into a whipped strawberry frosting by replacing 1/4 cup (30g) confectioners’ sugar with 1/4 cup freeze-dried strawberry crumbs/dust. See strawberry frosting for how to do that.
7. If your frosting begins losing shape: If your frosting becomes unstable or thins out/loses shape overtime, whip it on high speed until stiff peaks form to reintroduce more air.
8. Quantity: This recipe yields about 4–5 cups of frosting. This is enough to heavily frost 12–16 cupcakes (as pictured), a 9×13-inch quarter sheet cake, or a 2-layer cake. For a 3-layer cake, I recommend slightly scaling up the recipe by using 8 ounces (226g) of cream cheese, 1 cup (120g) confectioners’ sugar, 2 teaspoons vanilla extract, and 2 cups (480g/ml) heavy cream. After adding the heavy cream, you may need to whip the mixture for slightly longer.
9. Piping Tip: I used (affiliate link) Wilton 1M piping tip in the photos above. This is one of my favorite piping tips and you can see how to use it in this piping tips tutorial video.

According to quantum field theory (QFT), the framework that describes elementary particles and their interactions, empty space should be filled with quantum fluctuations that contribute an enormous amount of energy. In fact, calculations suggest the cosmological constant should be extraordinarily large, effectively approaching infinity.

Yet observations show something very different. The actual value of the cosmological constant is incredibly small compared with what theory predicts.

Now, researchers at Brown University have proposed a possible explanation.

Their work suggests that a mathematical feature of space-time itself may prevent the cosmological constant from ballooning to the huge values expected from quantum physics. The idea draws on an unexpected connection between quantum gravity and the quantum Hall effect, a remarkable phenomenon in condensed matter physics.

A Surprising Link Between Quantum Gravity and the Quantum Hall Effect

The team found that the mathematics behind a simple approach to quantum gravity closely resembles the mathematics that describes the quantum Hall effect, an unusual state of matter in which electrical conductance takes on highly precise values.

In the quantum Hall effect, those values remain fixed even when the conducting material contains imperfections. The stability comes from topology, a branch of mathematics concerned with the underlying "shape" or structure of a system.

The researchers argue that a similar type of topology appears in the Chern-Simons-Kodama state, a proposed ground state of quantum gravity.

"What we've shown is that if space-time has this non-trivial topology, then it resolves one of the deadliest problems of the cosmological constant," said study co-author Stephon Alexander, a professor of physics at Brown. "All the quantum perturbations that should blow up the value of the cosmological constant are rendered inert by this topology, which keeps the constant's value stable."

The study, co-authored by Alexander and Brown Theoretical Physics Center colleagues Aaron Hui and Heliudson Bernardo, was published in Physical Review Letters.

Einstein's "Ugly" Cosmological Constant

The cosmological constant first appeared in Albert Einstein's equations of general relativity, his theory of space, time, and gravity.

At the time, Einstein believed the universe was static. To keep his equations from predicting a collapsing universe, he introduced the cosmological constant as a kind of repulsive effect in empty space that counterbalanced gravity.

That idea seemed unnecessary after Edwin Hubble discovered in 1929 that the universe was expanding. Since the cosmos was not static after all, Einstein removed the term from his equations. He reportedly disliked the constant and later referred to it as his "biggest blunder."

For decades, the cosmological constant largely faded from prominence.

Then, in 1998, astronomers discovered something surprising: the expansion of the universe is speeding up. Rather than disappearing from the story, the cosmological constant suddenly became essential again because it could account for this accelerating expansion.

The Cosmological Constant Problem

The revival of the cosmological constant created a serious problem.

During the years when the constant had fallen out of favor, quantum field theory had become one of the most successful theories in science and a cornerstone of the Standard Model of particle physics.

QFT describes empty space as anything but empty. Instead, it is filled with particles constantly appearing and disappearing through quantum fluctuations.

All of this activity should contribute a vast amount of vacuum energy. That vacuum energy is associated with the cosmological constant, which means the constant should be extraordinarily large.

But observations show that it is not.

If the cosmological constant were as large as QFT predicts, the universe would have expanded so rapidly that galaxies, stars, planets, and ultimately life could never have formed.

The mismatch between theory and observation remains one of the most perplexing problems in modern physics. The puzzle is made even more striking because experiments have repeatedly confirmed the extraordinary accuracy of quantum field theory in other contexts.

A Topological Solution

Alexander has spent years studying Chern-Simons-Kodama (CSK) theory, a proposed quantum gravity state that emerges from quantum field theory.

Physicists still lack a complete quantum theory of gravity that describes gravity at the smallest scales. According to Alexander, the CSK approach is among the more straightforward possibilities.

"It's a really conservative approach to quantizing gravity," he said. "This is the approach used by people like Dirac, Schrödinger and Wheeler. It's just good, old-fashioned quantization."

Alexander had long noticed similarities between CSK theory and the mathematics of the quantum Hall effect. To better understand those connections, he collaborated with Hui, an assistant professor at Brown who studies topological systems.

"This is the beauty of the Brown Theoretical Physics Center," Alexander said. "We want to be a place where there's a mixing of lots of perspectives, and this is us practicing what we preach -- a cosmologist working closely with a condensed matter theorist."

How Topology Creates Stability

The researchers found that the cosmological constant in the CSK framework appears to benefit from the same kind of topological protection seen in the quantum Hall effect.

The quantum Hall effect occurs when electricity flows through extremely thin materials exposed to a magnetic field.

Imagine a thin rectangular strip of metal carrying an electric current. When a magnetic field is applied, a second voltage develops at right angles to the current. This effect produces what is known as a Hall voltage (named after Edwin Hall, who discovered it).

Under ordinary conditions, the Hall voltage changes smoothly as the magnetic field increases.

Under extremely cold temperatures and very strong magnetic fields, however, the behavior changes dramatically. Instead of varying smoothly, the Hall voltage increases in distinct steps and plateaus. Remarkably, those values remain identical regardless of the material being used or any imperfections it contains.

That reliability comes from topology.

In these extreme conditions, electrons behave collectively and enter a highly correlated quantum state. The topology of that state fixes the values of the steps and plateaus, making them resistant to disturbances and defects.

The Brown researchers argue that an analogous process occurs in the CSK description of quantum gravity.

Just as topology locks the Hall voltage into specific values, the topology of space-time could lock the cosmological constant into stable values, protecting it from the quantum fluctuations that would otherwise drive it much higher.

"What we find is that this quantization of the electrical conductance in quantum Hall has an analog with the cosmological constant," Hui said. "It also ends up becoming quantized for topological reasons. There turn out to be constraints in the theory that force the cosmological constant to take certain allowed quantized values."

A New Direction for Quantum Gravity

Alexander emphasizes that much more work is needed before a topological explanation of the cosmological constant can be fully established.

Still, he believes the findings represent an important step toward solving the gravitational side of the problem. The work also strengthens the case for the CSK state as a serious candidate for a future theory of quantum gravity.

"We took something old, which is this conservative, canonical approach to quantum gravity, and discovered something new that had been there all along," Alexander said. "Now we're working on a bigger picture of how this phenomenon works." %!s()

The U.S. and Iran signed a memorandum Thursday to open the Strait of Hormuz, ending a war that has upended global energy supply chains, pushed inflation higher and dented the outlook for growth.

But even if shipping through the strait normalizes, higher inflation has already been largely "baked in" across many economies, Simon MacAdam, deputy chief global economist at Capital Economics, said in a note this week.

"It can take many months for higher energy and fertiliser prices to be passed along food supply chains to end-consumers," MacAdam said. Prices of natural gas piped to households typically lag the upstream market by around three months, he said.

Oil prices retreated to around $80 a barrel on Friday, down from a peak of $118 in March when the war was at its height. Goldman Sachs cut its oil price forecast Tuesday, projecting Brent to average $80 in late 2026 and $75 in 2027, citing a faster-than-expected recovery in Persian Gulf crude flows.

Higher energy costs and upstream supply disruptions would take longer to feed through to the downstream food and energy sectors. A backlog of vessels waiting to transit the Strait of Hormuz could further delay a full recovery in freight flows.

The World Bank, which last week lowered its global economic growth forecast to 2.5%, the slowest pace since the pandemic, expects global inflation to climb to 4% this year, up from 3.3% in 2025, even if disruptions to oil flows ease in the coming weeks.

Fertilizer prices could jump as much as 38% this year as supply disruptions and shortages of key inputs from the Gulf ripple through agricultural markets, it said.

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Europe could face particular pressure because natural gas storage levels remain historically low, MacAdam said, expecting inflation in Europe and Japan to rise by an additional 3 to 4 percentage points as U.S. liquefied natural gas export prices move higher.

The European Central Bank was the first major central bank to raise interest rates last week, its first tightening move in nearly three years.

Meanwhile, the Fed, under new Chairman Kevin Warsh, left short-term interest rates unchanged on Wednesday but raised its forecast for personal consumption expenditures inflation to 3.6% by December, from 2.7% projected in March. Nine of the 18 voting members expect at least one rate hike before the end of this year.

The trajectory underscores how the Hormuz crisis has altered the calculus for central banks trying to balance slowing growth against rising inflation.

The Bank of England also kept its policy rates unchanged but warned that "even in the event of prompt conflict resolution, there could be a logistical delay in restoring energy production and transportation."

Ensuring that everyone has a certain level of buffer in peaceful times would provide that cushion against even a global contingency.

Matteo Lanzafame

Director, Asian Development Bank

Central banks that have shifted to a hawkish stance are unlikely to reverse course quickly, with fuel prices and inflation set to stay elevated, said Alex Holmes, regional director at Economist Intelligence Unit. Food inflation also faces additional pressure, he said, as a super El Niño threatens agricultural output in the coming months.

The crisis has also prompted governments to rethink energy security strategies. Countries affected by the disruption are expected to bolster energy stockpiles, direct resources to ramp up domestic production, and pursue alternative supply routes to reduce dependence on a single chokepoint.

"Ensuring that everyone has a certain level of buffer in peaceful times would provide that cushion against even a global contingency," Matteo Lanzafame, director at the Asian Development Bank, said at a virtual event Thursday. %!s()

The two events - on Saturday, 24 and Sunday, 25 April - will allow 100,000 people to take part in the London Marathon in 2027, effectively doubling the chances of success for those who entered the ballot.

The move is also expected to raise more than £150m for charities and provide a £400m boost to the UK economy, according to Hugh Brasher, chief executive of London Marathon Events.

Everyone who applied to take part next year will be entered into a ballot for both the Saturday and Sunday, with the ballot results announced in early July.

"The 2027 London Marathon double is our most ambitious evolution to date - a once-in-a-generation one-time-only reimagining of what a marathon and city-wide celebration of activity can be," said Brasher.

"By expanding to 100,000 runners across two days, we're opening the door for more people, more charities and more communities to take part in the world's greatest marathon. We believe that more than £150m can be raised for good causes and the UK economy will have a £400m social and economic benefit.

"We are grateful for the vision and support of the Mayor of London, the councils on the route, the emergency services, and all the stakeholders involved who have given their support to enable this world first event to be held for London and the UK."

Sadiq Khan, the Mayor of London, said: "London is the sporting capital of the world and I am delighted that, for one year only in 2027, the world famous London Marathon will expand into a two-day event."

A total of 1,338,544 people applied for the 2027 London Marathon, breaking the record of 1,133,813 applicants for the 2026 event.

The London Marathon had a record 59,830 finishers in 2026 and was the biggest annual one-day fundraising event in the world, with more than £90m raised to date for charity by 2026 participants.

History was also made on the course at this year's event, as Kenya's Sabastian Sawe became the first athlete to run a sub-two-hour marathon in a competitive race.

Brasher has remained adamant that the expanded two-day event will be for one year only, following what he described as an "astonishing total of applicants" hoping to take part in 2027.

He told BBC Sport the two-day event has been nine years in the making, but after the initial idea was formed in 2017, with the intention to hold it in 2020, they failed to gain permission.

The plan is for the elite women, elite female wheelchair athletes, championship and 'good for age' women to lead the mass event one day, with the elite men, elite male wheelchair athletes, championship and 'good for age' men leading the mass event on the other.

However, London Marathon organisers said all format details will be confirmed in the coming months.

All 100,000 participants across the two days will run on the normal London Marathon route from Greenwich to Westminster.

Brasher clarified to the BBC that a ballot draw will first be held for the Sunday - the day on which the marathon is normally held - before a second draw takes place for the Saturday.

The Mini London Marathon will be held on the Friday, with more than 20,000 young participants.

Organisers say all additional income generated by the two-day format will be distributed by the London Marathon Foundation to projects that inspire activity for children and young people across London and the UK. %!s()

Among the most ambitious and challenging ideas riding this wave of enthusiasm is something that sounds almost like science fiction: orbital data centers. SpaceX may be one of the most well-known companies seeking to build them, but it is not the only one.

The logic is seductive: Launch the data centers into orbit, where solar energy is abundant and land, water and local power grids are no longer constraints. As artificial intelligence drives an explosion in computing demand, companies are pitching orbital data centers as a way to escape the growing environmental and infrastructure pressures of Earth-based computing. Data centers often also face backlash from the public at having these centers located in their communities.

But there is a vast difference between launching satellites and operating an industrial-scale computing infrastructure in orbit. Space is unforgiving. Radiation damages electronics. The electronics generate enormous amounts of heat, and getting rid of that heat is surprisingly difficult in space. Repairs are extraordinarily expensive, and every pound launched into orbit still carries a significant cost.

We are engineering professors who study data center design and space systems engineering. Building a space-based data center will involve considerations from both sides.

What goes into a data center on Earth

First off, consider what goes into an Earth-based data center, like those that you’ve probably begun to see pop up everywhere. These facilities power cloud computing, video streaming, online banking, scientific computing and, increasingly, artificial intelligence. But a data center is much more than a room full of servers.

A data center needs several things to operate reliably. The first is electric power. Servers, networking equipment and storage devices consume large amounts of electricity, and that power demand is growing rapidly with AI.

The second is cooling. Almost all the electricity consumed by servers eventually becomes heat. If that heat is not removed quickly and reliably, equipment performance drops, failures increase and the data center can shut down. Cooling systems often include air handling units, chillers, cooling towers, pumps and, increasingly, liquid-cooling equipment. In many facilities, cooling is the largest energy consumer after the computing equipment itself.

The third is physical infrastructure, including the necessary land, buildings, structural support, backup power, water systems, communication networks and maintenance access. Data centers also need to be close enough to users and network backbones to provide fast digital services.

In short, Earth-based data centers are large electrical and thermal infrastructure systems built around computing hardware.

Placing them in space

So what would it take to build these data centers in space, and why are companies finding this possibility such an interesting business proposition?

As on Earth, these data centers would require massive amounts of power. In space, this power would come from solar panels. The Sun always shines in space and can’t be blocked by clouds. However, depending on the orbit the solar panels are put in, the Earth may shadow them for some portion of the orbit.

And even the best solar cells available today can convert only about half the sunlight that hits them to electricity.

Another potential advantage found in space is cooling. The cold background of space (near minus 455 degrees Fahrenheit, or minus 270 degrees Celsius) creates an opportunity: waste heat from the data center could escape into space through radiators, keeping the electronics cool.

In principle, that design could eliminate some of the bulky and water-intensive cooling infrastructure used on Earth. However, those thermal radiators would require a large amount of surface area, and that would be in addition to the area required by the solar panels.

In space, there is no air to blow across hot equipment and help heat escape. The heat has to leave as infrared radiation, which is a relatively slow process. As a result, removing 10 megawatts of waste heat can require radiator surfaces comparable to the size of two football fields.

Space-based data centers could also avoid some of the local conflicts that come with building large data centers on the ground. Many communities resist new data center developments because of their land use, energy and water demand, and noise and environmental impact.

A space-based system would avoid competing for local land and water resources, and it would not generate neighborhood noise or require local zoning approval in the same way.

However, space is already getting crowded, and launching thousands of large orbital data centers would accelerate this issue. Orbital debris and micrometeorites are hazards because they can puncture the space data center, and a worst-case collision could destroy it and create even more space debris.

The frequency of space launches necessary to send all the equipment to orbit may also become a concern for some communities. SpaceX has had protests at its launch complex in Boca Chica, Texas, from local activists who argue that its rocket testing and launches damage the surrounding environment.

All that data would need to be sent between Earth and these data centers – and between the data centers themselves – using radio waves or laser communications systems. Although satellite constellations such as Starlink and Amazon Leo have demonstrated that doing this is possible, the amount of data sent to and from space would balloon.

Additional challenges

These data centers, along with their solar panels and radiators, cannot be launched in one piece and would need to be assembled in space. This process would require new equipment for in-space servicing, assembly and manufacturing.

Another key challenge is the refresh cycle of computing hardware. Data center servers are not built to last forever. Operators on Earth usually replace or upgrade hardware every three to five years as chips improve, workloads change and equipment ages.

And equipment failures can require replacing components. The refresh and repair processes are relatively straightforward on Earth, where workers can physically remove and replace servers.

In space, refresh and repair becomes much harder. Hardware sent to orbit may be difficult or too expensive to upgrade. If the computing platform cannot be updated, or too many components fail, it may become obsolete long before the surrounding infrastructure reaches the end of its useful life.

In a field where performance improves so rapidly and demand from computing continues to increase, this hurdle could prove a major economic and operational challenge.

Then there is the harshness of space. These data centers would be in a near vacuum, with constant radiation hitting them. And depending on their orbit, they would go from hot when in the sunlight to cold in Earth’s shadow many times a day. All of these challenges, and more, are issues that will need to be addressed.

So, do they still make sense?

Despite these challenges, companies are moving forward with designing space-based data centers. SpaceX just announced the design for its AI1 Compute Satellite, which it hopes to use as an orbital data center spacecraft. However, this satellite is 100 to 1,000 times less capable than current Earth-based data centers.

Not every computing task makes sense to do in space. Many data center applications depend on fast response times and close connections to users on Earth. Financial transactions, interactive AI services and most cloud applications are extremely sensitive to delay.

More feasible early applications may be those that are less latency-sensitive and more tightly connected to space operations. Examples could include processing Earth observation data from satellites, military or intelligence data processing, scientific computing related to space missions, or specialized computing for satellites and other space assets.

In other words, the first viable space data centers may serve space-based customers before they compete with mainstream cloud data centers on Earth. %!s()