5 . Our carbon footprint is the estimated amount of carbon dioxide (CO₂) given off as we go about our daily lives. While the global average carbon footprint is about 4 tons per person each year, Americans contribute approximately 20 tons of greenhouse gas per person each year. Compared to other countries, even those who use the least amount of energy in the US still contribute double the carbon emissions than the global average per person. And, not surprisingly, a person’s carbon footprint increases in size as his or her income increases.

How is it possible that people in the US who live simple lifestyles, e.g., children or the homeless, make such large contributions to greenhouse gas emissions? The answer is simple: Each US citizen has access to various basic government services such as firefighting and police departments, road and bridge repair, libraries, jails and prisons, the military, etc. When these public services are divided equally among the entire US population, it significantly raises the carbon footprint per person. In fact, according to a study conducted by the Massachusetts Institute of Technology, the lowest carbon footprint that can be calculated for a person living in the US is 8.5 tons. And shockingly, this carbon footprint corresponds to a homeless person who sleeps in public shelters and eats in soup kitchens.

While it is admirable to make changes in lifestyle to reduce a carbon footprint, in reality, it is very difficult to do. The MIT study revealed that a “rebound effect” occurred when someone made an effort to reduce his or her carbon footprint. Take the example of a person who made the deliberate choice to buy a hybrid car instead of a large SUV to save money on gas costs. Very often that person would use the money he or she saved to do something else, e.g., take a long airplane trip. In this case, just one long airplane trip produces more CO₂ emissions than driving the large SUV for a year. This ends up having a negative impact on a person’s carbon footprint by making it bigger!

Can Americans reduce their carbon footprints? According to the study, it is possible, but it would require lifestyle changes such as giving up long-distance travel and buying fewer smartphones, tablets, and MP3 players that have large energy costs to produce and deliver. Another way to lower the average Americans US carbon footprint is to add a CO₂ tax on food, housing, and transportation, and most Americans don’t want their taxes raised. Unless we can find a way to reduce our carbon footprints, the price we may ultimately have to pay is much higher than the amount Americans will ever have to pay in taxes.

How to get all of the toothpaste out of the tube haunts many a bathroom. Bus not, perhaps, for much longer. Colgate-Palmolive, an American consumer-goods     1    , has taken up an invention in super-slippery surfaces to produce a toothpaste tube that     2     to deliver every last scrap of their contents.

In 2012, two inventors set up a company called LiquiGlide to commercialise their work on making liquids flow easily through pipes and out of containers. What caught many people’s imaginations at the time was a(n)     3     of how this could be used to empty a ketchup bottle without shaking it vigorously.

So far, ketchup-makers have not     4     the idea. But the health and beauty industry, where products tend to be pricier than ketchup, is interested. A Swiss company     5     the technology to lessen the amount of material left stuck to the insides of pipes and vesseis in its factories when it is time for a clean-up.

LiquiGlidc’s deal with Colgate is, though, the firm’s first big break into a consumer business. The new toothnastc called Elixu, comes in three varicties: a formula tor whitening teeth, one for gum and enamel care and a “detox”     6     which, it is claimed, removes any     7     from the mouth. All are packaged in plastic tubes that can be emptied with ease.

To produce the slippery pipes and containers, a pattern is first     8     an them and then a suitably formulated liquid is     9    . This fills the gaps in the texture, treating a surface across which gooey substances slide easily.

Besides pleasing customers who like to get their money’s worth, the new, slippery toothpaste tubes should help with recycling. Existing tubes are rarely recycled, not only because they have residue left inside them but also because they are usually made from a laminate of plastic and aluminum foil.     10     materials of this sort are hard to recycle, and therefore end up being dumped in landfills.

10 . On December 16, 2023, the first section of Maya Train officially opened, which runs between Campeche and Cancún, carrying up to 231 passengers across 290 miles and stopping at 14 train stations.

Built as an ambitious effort to promote tourism and boost Mexico’s economy, the rail system connects the major cities and tourist regions of the Yucatán Peninsula —from Cancún’s beaches to Tulum’s archaeological wonders. Once the project is completed, the entire rail system will link tourist destinations across five states. However, environmentalists and archaeologists argue that the train route will cause great damage to the environment-and ancient Mayan sites.

The Maya Train passes through six UNESCO World Heritage sites and thousands of archaeological sites. One particular area of concern is the Calakmul biosphere reserve, which is home to many endangered species, such as jaguars and over 500 other animal species. The train lines, more than 60 meters wide, could act as artificial barriers that may limit the movement of these animals within the reserve making it difficult for them to move around and access food and water sources.

Opponents also express safety concerns. Certain sections of the rail system will be built right on top of the aquifer’s(含水层的) most fragile points of contact with the surface. “It’s like wanting to build over eggshells,” says Guillermo Christy, a water treatment consultant. “Putting trains weighing thousands of tons on top could cause the underground caves to crash down.” To construct the train infrastructure also requires driving long piles deep into the ground, which poses a big threat to this fragile ecosystem and leads to water shortages.

In the ongoing debate of Maya Train, it is crucial to consider the delicate balance between economic development and environmental preservation. While Maya Train may provide economic benefits, we must not overlook the potential environmental and cultural losses, as well as the safety risks it may bring. Achieving harmony between progress and conservation may be a significant challenge for the project, but we must take into account the long-term consequences of our actions.