You should know that the earth was born more than 4.6 billion years ago, while human civilization is only a few thousand years old. Even the origin of human beings is only a few hundred thousand years, which is only a drop in the ocean compared with the age of the earth. So how do people with only a few thousand years of civilization or even hundreds of years of modern civilization know that the earth has a life span of 4.6 billion years?

1956, scientist Patterson calculated the age of the earth as 4.549 billion years by using U-Pb isotope, which was the first time that human beings measured the age of the earth. Later, in order to continue to confirm the final age of the earth, human beings continued to explore and finally confirmed that the final age of the earth was 4.586 billion years, which was very close to the answer of scientist Patterson. Moreover, humans also found the Casta gneiss 4.2 billion years ago and a fragment of zircon, which was also 4.4 billion years ago, confirming that the life of the earth really exceeded 4 billion years.

Later, in order to reconfirm the age of the earth, scientists used the decay of tungsten 182 and hafnium 182 to calculate the age of the earth. Hafnium 182 has a half-life of nine million years, and it decays into hafnium 182. At present, there is only a small amount of hafnium 182 on the earth, and it is this small amount of hafnium 182 that allows scientists to calculate the real age of the earth as 4.6 billion years. According to the scientists' budget, it will take 6 billion years for all tungsten on the earth to decay into hafnium, and there is still a small amount of hafnium on the earth, which shows that the hafnium on the earth has not completely decayed, so the age of the earth has finally been confirmed.

According to researchers' estimation, this asteroid named 20 12 LZ 1 is between 300 and 700 meters in diameter and will fly over the earth in less than 5.4 million kilometers.

Bao Kumar, the head of the space observation website Slooh, said that the asteroid is huge, but it is still invisible to the naked eye. Astronomers can watch it pass the earth through live webcast.

Bao Luqi said that the Slooh website will broadcast live the process of asteroids flying over the Earth from GMT 15: 00 (Beijing time 15: 08), using pictures taken by an observatory in the Canary Islands.

The National Aeronautics and Space Administration (NASA) of the United States has set up a file and recorded about 9,000 similar NEOs, but astronomers have been looking for new asteroids. The diameter of the asteroid about to fly is more than 152 meters, and the distance close to the earth is within 7.5 million kilometers. Its size and proximity to the earth have reached the standard of "potentially harmful" near-earth objects.

Minot, an astronomer at the Institute of Astronomy and Astrophysics of Australian National University, and his colleagues discovered this huge asteroid only a few days ago. Paolucci said, "Occasionally, asteroids suddenly appear, just like this, it's really big."

We live in holograms?

Holographic projection has become more and more popular in recent years, and it is applied in various fields in combination with VR technology. Recently, it has been suggested that our universe may be projected from a two-dimensional hologram.

The universe is a hologram, and all information is stored on its boundary. This idea sounds ridiculous, but a study published in June 20 17 in Physical Review Letters found that the experimental observation of cosmology is consistent with the prediction of "holographic universe".

Does this mean that we live in a two-dimensional hologram? Don't worry, we're already out!

For decades, some people in the scientific community have been half-joking about the idea that our universe is a giant hologram, or that it used to be, but it is not now. The laws of physics in holograms only need two dimensions, and everything in them is presented to us in three dimensions. (Note: 2D and 3D in this paper refer to spatial dimensions. )

As you can imagine, this is not an easy hypothesis to prove. However, some physicists also said that they now have some observation data of the early universe, which is just in line with the above holographic universe image, and the matching degree is comparable to the standard Big Bang model. Simply put, the holographic universe is the application of holographic principle in the universe: the universe can be described by its boundary (horizon), which is a two-dimensional hologram.

One of the team members, Niayesh Afshordi of the University of Waterloo, Ontario, Canada, said: "We proposed a scheme to adopt this holographic universe. Although it is also a big bang model, it is very different from the generally accepted model that relies on gravity and expansion. "

"These models have clear predictions. As we improve the data and deepen the theoretical understanding, the predictions can also be tested-these will be completed within five years. "

To clarify, the researchers did not say that we are living in holograms now. They are talking about the early stage of the universe, in the hundreds of thousands of years after the big bang. At that time, everything in the world was projected from the boundary of two dimensions to three dimensions.

If you don't know much about "the universe is a hologram", it can be traced back to the 1990s, when physicist Leonard Susskind popularized the view that technically speaking, the laws of physics we understand don't need three-dimensional space.

Then, if the universe is actually only two-dimensional, how can it assume a three-dimensional posture?

Since 1997, there have been more than 10,000 papers supporting this view, so it is far less ridiculous than we feel.

Now, Afshordi and his team write that they have studied the fluctuation of the cosmic microwave background (the "afterglow" of the Big Bang) and found strong evidence to support the holographic interpretation of the early universe.

Another member of the team, costas Skende of Southampton University in England, said: "Imagine that what we see, feel, smell and feel about time actually comes from a flat two-dimensional field."

"This idea is similar to the usual hologram. A two-dimensional surface contains the coding of three-dimensional images, which is a bit like the security chip of a credit card containing a lot of information. However, this time it is the whole universe. "

The holographic origin and evolution of the universe show the process of the universe we see.

Although the standard model of the Big Bang seems to be much more reasonable, physicists still have to consider the holographic principle, because there are some fundamental loopholes in the standard model, which push our overall understanding of the laws of physics to a desperate situation.

According to the big bang theory, in the very early days, the universe expanded at an extremely fast speed, which is called inflation. Inflation "sowed the seeds" for the formation of various structures in the universe today.

Although most physicists agree with the expansion of the universe and put forward various expansion models, the expansion theory is far from perfect. In fact, when we use the existing general relativity and quantum mechanics to explain the behavior of large objects and their atoms, we can't be consistent. Similarly, these basic physical laws can't explain how the various components of the universe should be wrapped in that incredible little thing.

Inflation theory is based on Einstein's general theory of relativity, but in the early stage of inflation, when the universe only has subatomic atoms, the role of quantum mechanics can not be ignored. But the problem is that quantum mechanics and general relativity are difficult to reconcile.

Ryan F. Mandelbaum wrote on Gizmodo's website: "Quantum gravity, one of the [hypotheses] to reconcile the two theories, thinks that if one spatial dimension is abandoned, gravity can be thrown away in the calculation, and things will be simple."

This is the basic idea of holographic principle.

Afsholdi told Mandelbaum: "The holographic description of the universe is based on a low-dimensional system, which accords with all the results we got from the Big Bang theory."

In order to test the effect of holographic principle on the occurrence of BIGBANG and its subsequent explanation, the research team constructed a model of one-dimensional time and two-dimensional space.

According to the real cosmic data, including the data observed from the cosmic microwave background (hundreds of thousands of years of thermal radiation after the Big Bang), they found that the predictions of the holographic universe were completely consistent with the data analysis results.

But there is a problem: only when the width of the model universe does not exceed 10 degrees, the results are completely consistent.

Researchers say it is too early to prove that the early universe is indeed a holographic projection. However, the actual observation data support the holographic universe, which makes us have no reason to rule out this scheme.

So, does this mean that we may live in holograms now? Afsholdi replied, I'm afraid not-their model only applies to the very early universe. As for how everything changed from two-dimensional to three-dimensional, no one can say for sure now.

"If you ask me, we are not living in a hologram, but we may get out of it." Afsholdi told Gizmodo website, "[20 17] must be three-dimensional."