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According to the Daily Mail, astronomers recently gave the most accurate measurements of the universe's expansion speed to date. The latest measurements conducted by a team of scientists using NASA's Spitzer Space Telescope show that the universe's expansion speed is about 46 miles (74 kilometers) per second and a million seconds (more accurate values ​​are: 74.3 ± 2.1 (km/s)/mp).

American astronomer Edwin Hubble first discovered through a large number of meticulous observations in the early 2000s that the universe was constantly expanding, and this expansion has begun since the birth of the universe.

According to current mainstream scientific understanding, scientists believe that the universe was born in a big explosion about 13.7 billion years ago. Since it is a violent expansion process, it is crucial to calculate the speed of its expansion. This value is called the "Hubble Constant". It is generally represented in capital h in physics. This value will be extremely critical to determining the age and size of the universe.

The Spitzer Space Telescope works in the infrared band with longer wavelengths, rather than the visible band. Its latest measurement data increases the accuracy of a similar observation previously conducted by the Hubble Space Telescope by three orders of magnitude, reducing the uncertainty range of this value to less than 3%, a major flyby in the field of cosmological measurement. Astronomers say the latest accurate value is 74.3 ± 2.1 (km/s)/mp, with a 1 million second gap of about 3 million light years.

Mihael Werner, a Spitzer project scientist, from NASA's Jet Propulsion Laboratory in California, said: "This time the Spitzer telescope has completed a work that did not belong to it. Before that, it surprised us by studying the atmosphere of exoplanets, and this time, it became a weapon for cosmology."

The data obtained from this discovery, combined with data previously released by NASA's Wilkinson microwave anisotropy detector, is hoped to use it to make an independent dark energy measurement. Dark energy is one of the largest unsolved mysteries in the universe.

In the late 1990s, astronomers were shocked to find that the universe we live in was actually in accelerating expansion. This is a very abnormal phenomenon. Because the universe is full of matter and dark matter, they both have mass and are also gravity. Under the influence of these gravity, the universe should gradually slow down or at least maintain balance, but should never accelerate expansion. In order to find out the answer to this question, astronomers had to conceive an "unknown mysterious force", which alone fought against the gravity generated by all matter and dark matter in the entire universe, and even defeated them all and promoted the accelerated expansion of the universe. Since scientists knew nothing about this mysterious powerful force, people gave it a name for granted: "dark energy". Wendy Freedman, the first author of this study and director of the Carnegie Observatory in the United States, said: "This is a huge mystery."

"It's great that we can use the Spitzer Space Telescope to conduct such research projects that touch the most basic level of cosmology, namely the precise expansion rate of the universe at the current stage and measure the proportion of dark energy in the universe from another perspective," she said.

Since the observed band is in the infrared band, the Spitzer Space Telescope can further forward the observation results of the Hubble Space Telescope in the visible light band, because compared to Hubble, the Spitzer Telescope's field of view can penetrate dust and gas clouds, and better observe a type of stars called "Ceffrey variable stars".

These variable stars are pulsating variable stars. Because of their obvious characteristics between their brightness and light change period, they are often used by astronomers as scales: by finding these variable stars with known distances and then observing their speed of leaving us, we can measure the expansion speed of the universe.

The reason why Cepheid variable stars can be used as a measure of the sky is because the distance between them and the earth can be directly measured. In 1908, the famous American female astronomer Henrietta Leavitt noticed that a type of star called Cepheid variable stars has a strict correlation between its brightness and light change period, which is the famous "period-light relationship".

To further illustrate why this property is very important, imagine a scenario where a person is gradually moving away from you, holding a candle in his hand. As this person gradually moves away, the candle light in his hand will also become darker. Then we just need to directly measure the brightness of the candle, and we can get the distance between the candle and our place. The same is true for the Cepheid variable stars in the universe, which are known as the "standard candlelight" in the universe. As long as they measure their brightness in the sky, astronomers can calculate their distance.

The Spitzer telescope selected 10 in the Milky Way and 80 Cepheid variable stars in the adjacent large Magellanic system for observation. Through these observations, the team was able to measure their brightness with higher accuracy and calculate their actual distances, thereby improving the previous measurements made on this subject. With this data, astronomers can go a step further and take a step up the ladder of the cosmic metrics to estimate the expansion rate of the entire universe.
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