What is gravitational lensing?

Everyone is already familiar with the real-life applications of gravity. Not only do we feel its effects every day, but also we are provided enough information from mass media. Gravity allows to keep our feet on the ground. Without gravity, we would simply float off into the atmosphere. Gravity is an essential force in the Universe, holding the Earth and all of the planets in place. Our galaxy is made up of hundreds of billions of stars and all of them hold together due to the force of attraction.

One of the most interesting things about gravity is that it operates like a lens, making distant objects appear nearer. Thanks to Albert Einstein’s insight on how gravity works, we now know that the universe isn’t static. On the contrary, it’s fully dynamic. Einstein predicted gravitational lensing, in which massive objects can bend light. Clearly, he was ahead of his time.

Cosmic lensing is something that allows us to see faint objects that otherwise would not be visible. What happens is that the light emitted from faraway galaxies goes past massive objects, such as galaxy clusters, and the force of attraction from these objects can distort or bend the light. This is the so-called gravitational lensing effect. The bigger the object is, the more powerful its gravitational pull is and, consequently, the greater the refraction of light is.

The gravitational lens effect was first validated during the first total solar eclipse in 1919 when astronomers Arthur Eddington and Frank Watson Dyson noticed that the position of the stars close to the Sun was a little bit different. The astronomical objects near the Sun were not in the correct place, the light coming from these stars being bent due to the curvature of spacetime. The two astronomers basically proved the theory of relativity. However, it was not until 1936 that humanity understood the true potential of gravitational lensing. Fritz Zwicky discovered that cosmic lensing can be used to study distant galaxies. Cosmic lensing is very similar to a magnifying glass in the sense that it makes distant objects easier to examine. It’s, therefore, possible to image the universe with the help of gravity.

The natural phenomenon can magnify light by factors of 10 and 20. What is more, the gravitational lensing effect is visible only in rare cases. The good news is that there is a telescope that can capture the phenomena. We are talking about Hubble. Hubble is capable of seeing the most remote cosmic lenses. The space telescope was launched in 2009 and since then it has offered sensitive images obtained from distant universes. At present, there is another program that guarantees to reveal galaxies a lot faster.

Most of the clusters of galaxies consist of matter that does not emit light – in other words, dark matter. Examining the nature of gravitational lensing patterns allows astrophysicists to understand how dark matter is distributed. If we understand dark matter, then we understand how background galaxies are distorted. An example in dark matter research is represented by Bullet Cluster. The nature of dark matter will be discussed another time.

The bottom line is that our Universe is full of cosmic lenses. It is these lenses that provide us useful insight into various parts of the universe. The question now is where should we concentrate our gravitational lensing efforts.

How quantum entanglement works

Quantum entanglement is a physical phenomenon in which two particles remain connected over long distances so that the actions performed on one particle also have an effect on the second particle. If it sounds mind-boggling, it’s because it is. Albert Einstein, who first discussed the idea of quantum entanglement in a joint paper with Boris Podolsky and Nathan Rosen, dubbed the phenomenon “spooky action at a distance” because it implies faster than light communication, which his theory of relativity ruled out.

The particles in the entangled pair form an inseparable whole and one cannot be fully described without the other. However, entanglement is broken when particles interact with the environment, such as when a measurement is made. The paradox of quantum entanglement lies in the fact that a measurement of either one of the entangled particles collapses the entire system before the result of one measurement can be transmitted to the other particle.

As a thought experiment, we can imagine that two separate particles are sent in opposite directions, separated by thousands of miles, one in Washington and one in London. In quantum entanglement, these two particles remain connected in spite of the distance, so if we were to spin one particle in Washington clock-wise, the second one in London would instantly spin anti-clockwise.

Quantum entanglement only applies to small particles such as atoms and electrons, not too large objects such as animals or buildings. Although scientists initially believed that the phenomenon only applied to minuscule particles, recent experiments have shown that it can also happen between slightly larger objects that are visible to the naked eye – such as vibrating aluminum sheets measuring 15 micrometers in diameter.

Scientists don’t know yet what exactly links the two particles and Einstein called the phenomenon impossible because it implied that objects could be influenced by something else other than their own surroundings, but scientists were able to prove that it is possible.

One study published in the journal Science reports the experiment of physicist Jian-Wei Pan from the University of Science and Technology of China in Shanghai, who together with his team produced a pair of entangled particles on a satellite which orbits 300 miles above the atmosphere, then beamed these particles to two labs on earth that were 750 miles apart. This experiment broke two records: one – it was the first time someone ever produced entangled particles in space, and 2 – this was the biggest distance that linked particles could maintain. Before it, the biggest distance was 86 miles. This distance was achieved because on Earth, in order to send two entangled particles in different directions, you need diver optic cables to transmit them. Since fibers absorb light, the connection is weakened after every mile. But in the vacuum of space, there is no light to be absorbed, and so the entangled particles will maintain their connection for longer.

The implications of experiments such as this one – and of the phenomenon itself – are huge. Scientists believe that quantum entanglement could have applications in computing and cryptography and that it could help us create ultra-precise clocks. At the same time, by challenging our understanding of causality, locality, and realism, quantum entanglement raises both scientific and philosophical debates, breaking the rules of standard physics.