1. How did the universe originate?
On the one hand there is the widely accepted theory of the Big Bang, the Big Bang, according to which the universe was originally something extremely dense, small and hot, which in a matter of tenths of a second radically expanded and cooled, and still continues to expand. Sort of like a raisin cake in the oven that grows by separating raisins (or galaxies) from each other. But there are experts who propose a new model according to which the origin was not a single Big Bang, but many. A continuous chain of universes that follow and repeat each other, but without being exact replicas of the previous ones. As for the age of the universe, recent observations suggest that it is between 13.5 and 14 billion years old.
2. What is the future of the universe?
According to the new theory of continuous universes, the universe will not die, but will continue to repeat itself. Or maybe it will be a cold and dark universe, as the galaxies and stars separate from each other and their light and heat are lost in the darkness, expanding eternally and cooling until they reach a state of absolute cold, where the molecules do not have the energy to make the slightest movement? Or will it be a universe that, after expanding, will come to a point where it will begin to collapse on itself and then the problem will be the other way around? Lately there are other theories that speak of a Big Rip, in which the rate of expansion would be so tremendous that groups of galaxies, stars, dark energy and everything else would become a kind of fabric that is stretched to rip.
3. Are there alternative or multiple universes?
One theory postulates that an alternate dark matter universe could exist at the same time as this one, but we couldn’t achieve it. The best way to imagine it is to think of a double glazed window with a fly in the middle. The fly cannot cross from one side to the other, just as we cannot cross from one universe to another. These two universes would be attracted to each other by the force of gravity and would eventually collide. By doing so, they would create a Big Bang. This would imply that things are happening right now that will help create another universe in the future. On the other hand, there are several multiple-universe hypotheses in quantum physics and cosmology, in which the physical constants and the nature of each universe are different. For example, the “bubble universe” is an infinite series of open universes with different constants.
4. What is the geometry of the universe?
According to Einstein, the universe is a continuum in time-space that could take three forms, depending on the content of matter and energy:
- Spherical shape (positive curvature ). Travel in one direction and you will eventually return to the starting point. Without dark energy, this universe will stop expanding and collapse in on itself. With it, the expansion will continue.
- Flat (no curvature). The traveler will never return to his starting point. Even without dark energy, this universe will continue to expand eternally, albeit more and more slowly. With dark energy, the expansion will accelerate more and more. According to the latest observations, this is the shape of our universe.
- Saddle shape (negative curvature) . The traveler will never return. The expansion will hardly slow down, even without the presence of dark energy.
5. What are the components of the universe?
Stars, asteroids, planets, cosmic dust, elusive neutrinos, helium, hydrogen, and everything we can see around us make up a tiny part of what the universe is. The remaining 95% is occupied by strange dark matter and the even more incomprehensible dark energy.
6. What is cosmic expansion?
Cosmic acceleration is the observation that the universe appears to be expanding at an accelerating rate. In 1988 observations of stars called type 1A supernovae suggested that this expansion is accelerating more and more. The expansion of the universe was proposed and demonstrated by Edwin Hubble, by determining the distance to several galaxies and verifying that the most distant ones were shifted towards the red, that is, they were moving away from us.
The most accurate observations to date, made with WMAP and the Hubble Space Telescope, point to an expansion speed of between 70 and 72 kilometers per second.
7. What is cosmic background radiation?
It is an ancient microwave radiation that permeates the entire universe, and is considered as the embers that were left after the Big Bang. It was accidentally discovered by two astronomers at Bell Laboratories, Arno Penzias and Robert Wilson. Their measurements, combined with Hubble’s discovery that galaxies are moving away from us, are strong evidence for the Big Bang theory.
8. What is dark matter?
It is a hypothetical form of matter that has more mass than visible matter, but unlike the latter, it does not interact with the electromagnetic force. Scientists infer its presence because it has gravitational effects on visible matter. For example, the rotational speeds of galaxies, the orbital speeds of galaxies within clusters, and the temperature distribution of galaxy gases suggest that there must be something there, something else. There is more matter in galaxy clusters than we might expect from the galaxies and the hot gas we can see. Apparently 30% of the universe is made up of dark matter. Discovering its nature is one of the most important goals of modern astronomy.
9. What is dark energy?
This is Mecca and perhaps the greatest mystery in current cosmology. Dark energy is a mysterious presence that offers the best explanation yet for why the universe is expanding at an accelerating rate. In the current model of cosmology, dark energy makes up 70% of the total mass-energy of the universe. There are two models according to which dark energy either permeates the universe in a heterogeneous way or changes its density and energy at certain times / places. Scientists agree that it has low density
(10-29 grams per cubic centimeter) and does not interact with fundamental forces except gravity.
10. How is a star born and how does it die?
Galaxies contain clouds of dust and gas called nebulae. If a nebula grows large enough, its gravity overcomes the pressure of the gas and the cloud begins to collapse until it reaches enough temperature to melt (or burn) the hydrogen. The released energy stops the contraction and the outer layers of the gas are lost. What remains is an incandescent ball, composed mainly of hydrogen, illuminated by the fusion reactions of its nucleus. That is, a star.
When its fuel runs out, the star begins to decline. The nucleus is mostly converted to helium and begins to collapse, at the same time that the outer regions are pushed out. The star becomes colder and brighter: it is a red giant. If the star is large, it will start the cycle again by burning the helium. If it is massive, it will enter a third stage, burning coal. And if it’s really big, it will burn iron.
11. What is a supernova and what is it for?
It is a star between 5 and 10 times the mass of the sun that, after burning hydrogen, helium and carbon to stay alive, will turn to iron. But iron fusion does not release energy, it absorbs it. Then the core cools, all fusion ceases, and the poor star implodes. And then it explodes. This explosion is the greatest act of violence in the cosmos. A single supernova can be brighter than an entire galaxy for a few days. After this phase, the nucleus can end up as a white dwarf, a neutron star, or a black hole. Supernovae are used to determine how far away another galaxy is and its rate of expansion.
12. Where do the most energetic cosmic rays come from?
Observations from the Pierre Auger Cosmic Ray Observatory in Argentina in 2007 suggest that one of the sources of these rays is the active nucleus of galaxies, that is, black holes. 90% of cosmic rays are protons, 9% are helium nuclei, while the remaining 1% are electrons. Thanks to the low density of matter in space, these particles manage to travel in one piece, until they collide with other particles in our atmosphere, causing showers whose energy and composition are measured in various astronomical observatories.
13. How many galaxies are there and how were they formed?
There are about 100 billion (10011) galaxies. Now, the detailed process of its formation is another of the open questions of astronomy. There are several theories according to which small structures such as globular clusters were joining one another under gravitational forces. In other models, several protogalaxies formed in a great simultaneous collapse that could last 100 million years.
14. What happens when two galaxies collide?
It is very common for galaxies to collide and interact with each other. In fact, collisions and junctions between galaxies are believed to be one of the main processes in their evolution. Most galaxies have interacted since they formed. And the interesting thing is that in these collisions there are no collisions between stars. The reason is that the size of the stars is very small compared to the distance between them. On the other hand, gas and dust do interact in such a way that they even change the shape of the galaxy. Friction between gas and colliding galaxies produces shock waves that can in turn initiate star formation in a given region of the galaxy.
15. Are galaxies still being created?
The latest observations indicate that it is. Most galaxies were created early in the history of the universe, and astronomers thought that large galaxies like the Milky Way, which is 12 billion years old, could no longer be born. But NASA’s GALEX (Galaxy Evolution Explorer) space telescope, launched in 2003, has detected several galaxies that appear to be between one hundred million and one billion years old. I mean, babies.
The Galaxy Evolution Explorer has managed to photograph stars never seen to date in the outer part of the galaxy M83, also known as the Austral Pinwheel.
16. When will stars stop being born?
The current era of star formation is expected to continue for another hundred billion years. Then the “stellar age” will begin to decline for a hundred trillion years (1013–1014 years), as the smallest and longest-lived stars, the tiny red dwarfs, fade. At the end of the “stellar age,” galaxies will be made up of compact objects: brown dwarfs, white dwarfs, neutron stars, and black holes.
17. What is antimatter and why is there so little?
Antimatter is a real and proven thing. All elementary particles have a counterpart with the same mass but opposite charge. For example, the antiparticle of an electron (negative charge) is a positron (positive charge). When a particle collides with its antiparticle both are destroyed, releasing a burst of energy known as a gamma ray. Antimatter has practical medical uses in positron emission tomography (PET). And it could be used as a spacecraft fuel.
In the initial stages of formation of the Universe there were pairs of particle-antiparticles of all kinds that were continually created and destroyed in collisions. But at one point, a reaction called bariogenesis violated this symmetry, causing a small excess of quarks and leptons over antiquarks and antileptons. Since then, our universe has been dominated by “normal” matter.
18. What are black holes? How are they formed?
They are very prevalent objects in the universe and so dense that nothing escapes their gravitational pull. They are usually formed when a star goes supernova: its core explodes and there is no known force that can stop the immense gravity that looms over it. Almost all galaxies are believed to contain black holes at their center, millions and billions more massive than our sun. Some of them are the most violent and energetic objects in the universe: absorbing stars, dust, and gases, these black holes fire radio jets and emit extremely intense points of light called quasars (“quasi-stellar radio sources.” Others, often the oldest ones (like the one that lies in the center of the Milky Way), are calmer eaters.We cannot observe black holes directly, but we do see the effect they have on the material that surrounds them.
19. Do black holes die? Do they evaporate?
Research by experts such as Stephen Hawking seems to indicate that black holes do not capture matter forever, but that sometimes there are slow “drips” in the form of an energy called Hawking radiation. That means they may not have eternal life. The holes get smaller and it happens that the rate of radiation increases as the mass of the hole decreases, in such a way that the object radiates more intensely as it fades. But no one is sure what happens during the later stages of evaporation from a black hole. Some astronomers think that a tiny remnant remains. In general, the concept of black hole evaporation remains rather speculative.
20. What happens when two black holes collide?
When two galaxies come together, their supermassive black holes (billions the size of the sun) eventually have to interact, either in a violent direct impact or moving toward the center until they touch each other. And there is where things get interesting. Instead of getting close in a good way, the forces of both monsters are so extreme that one of them is kicked out of the newly joined galaxy with such tremendous speed that it can never return. For its part, the kicking hole receives an enormous amount of energy, which it injects into the disk of gas and dust that surrounds it. And then this disk emits a soft X-ray glow that lasts for thousands of years. The collision of two black holes is a very rare event.
21. What is a white hole?
The equations of general relativity have an interesting mathematical property: they are symmetric in time. That means that one can take any solution to the equations and imagine that time flows in reverse, instead of forward, and one will get another set of solutions to the equations, equally valid. Applying this rule to the mathematical solution that describes black holes, a white hole is obtained. Since a black hole is a region of space from which nothing can escape, the opposite version is a region of space into which nothing can fall. In fact, just as a black hole can only swallow things, a white hole can only spit them out. White holes are a perfectly valid mathematical solution to the equations of general relativity. But that doesn’t mean that one actually exists in nature.
22. Does the Higgs Boson exist and does it have the secrets of the Universe?
Proton aurora over Earth captured by NASA’s IMAGE satellite
For more than two decades scientists have been searching for one of the most elusive things in the universe, the Higgs boson, the particle that gives mass to everything in the cosmos. It is a theorized particle, but never seen. The Higgs boson is famous for being the only particle predicted by the Standard Model of Physics that remains undetected. In theory, all the other particles in this universe obtain their mass by interacting with the field created by the Higgs bosons. If the Higgs is discovered, the standard model can announce that it is the theory that unifies everything, except gravity.
23. Do protons have a finite life?
The Great Unified Theories of particle physics predict that the proton has a finite life. The physics of how a proton spontaneously decays is closely related to the physics of the Big Bang, and to the difference between the amount of matter and antimatter in the universe. The discovery of this spontaneous proton decay would be one of the most fundamental in physics and cosmology. His answer could come with a large international underground detector that Europe is trying to design.
24. What are gravitational waves?
A gravitational wave is a small fluctuation in the curvature of the fabric of space-time, which propagates in the form of a wave, traveling outward from an object or a system of moving objects. It was predicted by Einstein, and his study could answer the big question about what is the nature of gravity. Although gravitational radiation has not been directly measured, its existence has been indirectly proven, and it is thought that it could be linked to violent cosmic phenomena. A sophisticated space interferometric antenna called LISA, which will be launched in orbit in the next decade, will be dedicated to detecting and analyzing gravitational waves.
25. What are gravitational lenses and what are they used for?
Gravitational lenses are curvatures in spacetime that break starlight into double, triple, and quadruple mirages from the beginning of time. Imagine a bright object that is very far from Earth, say 10 billion light-years away. If there is nothing between you and that object, you will see (with a super-telescope) only one image. But if a massive galaxy or galaxy cluster blocks direct view of that other star, the light from the distant object will bend following the gravitational field around the galaxy. That is, the gravity of the galaxy ahead acts like a lens to redirect light rays. But instead of creating a single image of the distant object, this lens creates multiple images of the same object. Gravitational lenses are used like natural telescopes to detect these extremely old and distant objects, as well as to study the geometry and expansion of the universe.
26. Is there extraterrestrial life?
So far no space probe or telescope has found concrete traces of life as we know it on Earth. The debate about extraterrestrial life is divided between those who think that life on Earth is extremely complex, so it is unlikely that there is something similar to us on another planet, and those who point out that the processes and chemical elements involved in the Terrestrial creatures are very common throughout the universe, and the only thing to look for is the right conditions. For the latter, it is quite probable that there is life similar to ours on other worlds, extrasolar planets in whose search we are engaged.
27. Did life reach Earth on an asteroid?
For astrobiologists studying the possibility of life on other worlds, interplanetary travel doesn’t have to be the privilege of comets, cosmic dust, or space probes with or without people inside. It is not unreasonable, they say, to think that there are or have been other cosmonauts out there: Cowboys traveling on the back of asteroids, stowaways hiding between the folds of a spacesuit, and even unhappy creatures displaced from their worlds by brutal collisions. All these tiny life forms could have bounced from one planet to another, blown around like leaves in the wind by brutal cosmic weather. Seen like this, life on Earth could very well come from Mars … or vice versa. Or maybe from the moon Europa, or why not, from Titan. Or maybe the spore with the spark of life came from the other side of the Oort asteroid cloud. This is the theory of panspermia.
28. Can there be life without water?
Tardigrades with tiny invertebrates that, in extreme environmental situations, can enter states of suspended animation known as cryptobiosis.
The water and the life that we know are inseparable. No organism has yet been seen to exist without water, as cells need water to surround their membranes. However, there are life forms – a few animals, plants, and an unknown number of microbes – that manage to survive for long periods of time without the liquid. They can be dissected like paper and remain that way for hours or decades, to immediately revive upon contact with water. The unresolved questions about these very special beings are two: how do they tolerate this internal drought of their bodies? and why are they not more common?
29. Is Jupiter a failed star?
Anyone would say, observing our Solar System from afar, that Jupiter and the Sun are the only two objects here. This planet is huge, but despite that enormity it is still a thousand times smaller than the sun. To be a star, Jupiter would have to be 80 times bigger. Because being massive is the only way to generate enough internal heat to allow thermonuclear fusion reactions – the energy that gives stars their light. And since that’s never going to happen, that’s why Jupiter is said to be a failed star.
30. Do neutrinos keep the secrets of the cosmos?
The Standard Model of Physics predicted that neutrinos were massless. But it turns out they do, according to a discovery from the past decade. What’s more, neutrinos come in various “flavors” and can oscillate, or change identities. That means that these interesting particles are the first reliable proof of phenomena that are outside the standard model. The neutrino detectors of the future have the mission to answer other questions about these particles. For example, what do these identity shifts tell us about the processes that generate heat inside the Earth? Do you have clues to supernova explosions? Are neutrinos their own antiparticles?
