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By Dejan Stojkovic, University at Buffalo 

Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to [email protected].

What are wormholes and do they exist? – Chinglembi D., age 12, Silchar, Assam, India

Imagine two towns on two opposite sides of a mountain. People from these towns would probably have to travel all the way around the mountain to visit one another. But, if they wanted to get there faster, they could dig a tunnel straight through the mountain to create a shortcut. That’s the idea behind a wormhole.

A wormhole is like a tunnel between two distant points in our universe that cuts the travel time from one point to the other. Instead of traveling for many millions of years from one galaxy to another, under the right conditions one could theoretically use a wormhole to cut the travel time down to hours or minutes.

Because wormholes represent shortcuts through space-time, they could even act like time machines. You might emerge from one end of a wormhole at a time earlier than when you entered its other end.

While scientists have no evidence that wormholes actually exist in our world, they’re good tools to help astrophysicists like me think about space and time. They may also answer age-old questions about what the universe looks like.

Fact or fiction?

Because of these interesting features, many science fiction writers use wormholes in novels and movies. However, scientists have been just as captivated by the idea of wormholes as writers have.

While researchers have never found a wormhole in our universe, scientists often see wormholes described in the solutions to important physics equations. Most prominently, the solutions to the equations behind Einstein’s theory of space-time and general relativity include wormholes. This theory describes the shape of the universe and how stars, planets and other objects move throughout it. Because Einstein’s theory has been tested many, many times and found to be correct every time, some scientists do expect wormholes to exist somewhere out in the universe.

But, other scientists think wormholes can’t possibly exist because they would be too unstable.

The constant pull of gravity affects every object in the universe, including Earth. So gravity would have an effect on wormholes, too. The scientists who are skeptical about wormholes believe that after a short time the middle of the wormhole would collapse under its own gravity, unless it had some force pushing outward from inside the wormhole to counteract that force. The most likely way it would do that is using what’s called “negative energies,” which would oppose gravity and stabilize the wormhole.

But as far as scientists know, negative energies can be created only in amounts much too small to counteract a wormhole’s own gravity. It’s possible that the Big Bang created teeny, tiny wormholes with small amounts of negative energies way back at the beginning of the universe, and over time these wormholes have stretched out as the universe has expanded.

Just like black holes?

While wormholes are interesting objects structures to think about, they still aren’t accepted into mainstream science. But that doesn’t mean they’re not real – black holes, which we astrophysicists know abound in our universe, weren’t accepted when scientists first suggested they existed, back in the 1910s.

Einstein first formulated his famous field equations in 1915, and German scientist Karl Schwarzschild found a way to mathematically describe black holes after only one year. However, this description was so peculiar that the leading scientists of that era refused to believe that black holes could actually exist in nature. It took people 50 years to start taking black holes seriously – the term “black hole” wasn’t even coined until 1967.

The same could happen with wormholes. It may take scientists a little while to come up with a consensus about whether or not they can exist. But if they do find strong evidence pointing to the existence of wormholes – which they may be able to do by looking at odd movements in star orbits – the discovery will shape how scientists see and understand the universe.

Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to [email protected]. Please tell us your name, age and the city where you live.

And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.

About the Author:

Dejan Stojkovic, Professor of Physics, University at Buffalo

This article is republished from The Conversation under a Creative Commons license. Read the original article.

By Aisling Pigott, University of Colorado Boulder; Jennifer Scheib, University of Colorado Boulder, and Kyri Baker, University of Colorado Boulder 

Hot summer days can mean high electricity bills. People want to stay comfortable without wasting energy and money. Maybe your household has fought over the best strategy for cooling your space. Which is more efficient: running the air conditioning all summer long without break, or turning it off during the day when you’re not there to enjoy it?

We are a team of architectural and building systems engineers who used energy models that simulate heat transfer and A/C system performance to tackle this perennial question: Will you need to remove more heat from your home by continuously removing heat throughout the day or removing excess heat only at the end of the day?

The answer boils down to how energy intensive it is to remove heat from your home. It’s influenced by many factors such as how well your house is insulated, the size and type of your air conditioner and outdoor temperature and humidity.

According to our unpublished calculations, letting your home heat up while you’re out at work and cooling it when you get home can use less energy than keeping it consistently cool – but it depends.

Blast A/C all day, even when you’re away?

First, think about how heat accumulates in the first place. It flows into your home when the building has less stored heat than outside. If the amount of heat flowing into your home is given by a rate of “1 unit per hour,” your A/C will always have 1 unit of heat to remove every hour. If you turn off your A/C and let the heat accumulate, you could have up to eight hours’ worth of heat at the end of the day.

It’s often less than that, though – homes have a limit to how much heat they can store. And the amount of heat that enters your home depends on how hot the building was to begin with. For example, if your home can only store 5 units of thermal energy before coming to an equilibrium with the outdoor air temperature, then at the end of the day you will only ever have to remove 5 units of heat at most.

Additionally, as your home heats up, the process of heat transfer slows down; eventually it reaches zero heat transfer at equilibrium, when the temperature inside is the same as the temperature outside. Your A/C also cools less effectively in extreme heat, so keeping it off during the hottest parts of the day can increase overall efficiency of the system. These effects mean there’s no one straightforward answer to whether you should blast the A/C all day or wait until you get back home in the evening.

Energy used by different A/C strategies

Consider a test case of a small home with typical insulation in two warm climates: dry (Arizona) and humid (Georgia). Using energy modeling software created by the U.S. National Renewable Energy Laboratory for analyzing energy use in residential buildings, we looked at multiple test cases for energy use in this hypothetical 1,200 square-foot (110 square-meter) home.

We considered three temperature strategy scenarios. One has the indoor temperature set to a constant 76 degrees Fahrenheit (24.4 degrees Celsius). A second lets the temperature float up to 89 F (31.6 C) during an eight-hour workday – a “setback.” The last uses a temperature setback to 89 F (31.6 C) for a short four-hour workday.

Within these three scenarios, we looked at three different A/C technologies: a single stage central A/C, a central air source heat pump (ASHP) and minisplit heat pump units. Central A/C units are typical of current residential buildings, while heat pumps are gaining popularity due to their improved efficiency. Central ASHPs are easily used in one-to-one replacements of central A/C units; minisplits are more efficient than central A/C but costly to set up.

We wanted to see how energy use from A/C varied across these cases. We knew that regardless of the HVAC technology used, the A/C system would surge when the thermostat setpoint returned to 76 F (24.4 C) and also for all three cases in the late afternoon when outdoor air temperatures are usually the highest. In the setback cases, we programmed the A/C to start cooling the space before the resident is back, ensuring thermal comfort by the time they get home.

What we found was that even when the A/C temporarily spikes to recover from the higher indoor temperatures, the overall energy consumption in the setback cases is still less than when maintaining a constant temperature throughout the day. On an annual scale with a conventional central A/C, this could result in energy savings of up to 11%.

However, the energy savings may decrease if the home is better insulated, the A/C is more efficient or the climate has less dramatic temperature swings.

The central air source heat pump and minisplit heat pump are more efficient overall but yield less savings from temperature setbacks. An eight-hour setback on weekdays provides savings regardless of the system type, while the benefits gleaned from a four-hour setback are less straightforward.

About the Authors:

Aisling Pigott, Ph.D. Student in Architectural Engineering, University of Colorado Boulder; Jennifer Scheib, Assistant Teaching Professor of Building Systems Engineering, University of Colorado Boulder, and Kyri Baker, Assistant Professor of Building Systems Engineering, University of Colorado Boulder

This article is republished from The Conversation under a Creative Commons license. Read the original article.

By JustForex

The US stock indices were trading lower on Friday. By the closing of the stock market, Dow Jones (US30) decreased by 0.85% (-0.01% for the week), and S&P 500 (US500) lost 1.29% (-0.96% for the week). The NASDAQ Technology Index (US100) fell by 2.01% (-2.24% for the week). Amazon, Apple, and Microsoft all fell, and the S&P 500 and Nasdaq slowed the most. Higher rates tend to be negative for technology companies and growth stocks.

Richmond Federal Reserve President Thomas Barkin said on Friday that US Central Bank officials still have plenty of time before they need to decide how much to raise interest rates in September. The recovery in US stocks is inspiring confidence among investors. The S&P 500 (US500) rebounded about 16% from its low after its worst first half since 1970, helped by stronger-than-expected corporate earnings, and hopes the economy can avoid a recession.

Stock markets in Europe were mostly down on Friday. German DAX (DE30) decreased by 1.12% (-2.19% for the week), French CAC 40 (FR40) lost 0.94% (-1.32% for the week), Spanish IBEX 35 (ES35) fell by 1.09% (-1.05% for the week), British FTSE 100 (UK100) was up by 0.11% (+0.66% for the week).

In the last few days, Europe has been hit by the rains. Water levels in a key German bottleneck on the Rhine River jumped, easing a crisis that has hampered energy and industrial production this month. An extended period of very hot and dry weather this summer drained Europe’s rivers, disrupting the transportation of goods and energy at a time when the region needs alternative energy sources instead of gas the most. This helped push natural gas prices to record highs, increasing inflationary pain for industries and households and threatening to push Germany into recession.

On Sunday, a senior ministry official said that energy-intensive industries in Italy are also modifying their production to save energy as they struggle with rising bills. Italy recently struck deals with several alternative gas-producing countries to reduce its dependence on Moscow. Those agreements allowed Rome to fill its gas storage facilities quickly, but it was not enough to protect its industry from skyrocketing energy prices.

Oil prices stabilized on Friday but fell over the week because of a stronger US dollar and fears that the economic slowdown would weaken demand for crude oil. The strengthening US dollar hit a five-week high, which limited the rise in oil prices as it makes oil more expensive for buyers in other currencies. Haitham al-Gais, the new secretary general of the Organization of the Petroleum Exporting Countries, told Reuters he was optimistic about oil demand in 2023.

Asian markets traded flat last week. Japan’s Nikkei 225 (JP225) decreased by 0.04% for the week, Hong Kong’s Hang Seng (HK50) added 1.32% for the week, and Australia’s S&P/ASX 200 (AU200) was up by 1.17% for the week.

Earlier this year, the COVID-19 shutdown in China disrupted global supply chains, causing delays in shipments and production worldwide and hampering economic growth. Now the country faces another severe threat, and that threat could be even worse for the economy. This month, China is battling its worst heat wave in 60 years. In Sichuan province, home to more than 80 million people, the record-breaking heat wave has exacerbated an ongoing drought that has caused reservoir levels to drop by half this month. As a result, officials announced on Aug. 15 that factories in 19 cities and prefectures would be forced to close for five days to save power.

The People’s Bank Loan Prime Rate rate was cut for the second time in two weeks. The move comes as the bank struggles to stimulate the economy amid headwinds from COVID lockdowns, a debt-laden real estate market, and a looming energy crisis.

In the commodities market, futures on natural gas (+5.84%) and cotton (+3.64%) showed the largest gains over the week. Futures on lumber (-12.23%), silver (-8.37%), platinum (-7.31%), wheat (-6.33%), orange juice (-5. 91%), palladium (-4.03%), coffee (-3.96%), sugar (-3.06%), gold (-3.04%), soybeans (-2.88%), WTI oil (-2.68%), and Brent oil (-2.1%) showed the biggest drop.

S&P 500 (F) (US500) 4,228.48 −55.26 (−1.29%)

Dow Jones (US30) 33,706.74 −292.30 (−0.86%)

DAX (DE40) 13,544.52 −152.89 (−1.12%)

FTSE 100 (UK100) 7,550.37 +8.52 (+0.11%)

USD Index 108.10 +0.62 (+0.58%)

• – China PBoC Loan Prime Rate at 04:15 (GMT+3).

By JustForex

This article reflects a personal opinion and should not be interpreted as an investment advice, and/or offer, and/or a persistent request for carrying out financial transactions, and/or a guarantee, and/or a forecast of future events.