A short history of black holes | Science News for Students

A short history of black holes

Scientists now have the first-ever picture of a black hole. Here’s the historical context
Apr 10, 2019 — 4:14 pm EST
an illustration of a black hole with stars in the background, a dark black circle with a white ring and aura around the outside of the hole

The story of how black holes (one illustrated) came to be accepted in science is a tale worth recounting.

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Black holes have been sucking up scientific attention from the very beginning. They were hinted at as early as the 1780s. Albert Einstein predicted them in his general theory of relativity. But they didn’t get the name we know today until the 1960s.

Black holes were once thought to be only a mathematical curiosity. They were bizarre beasts that squashed gobs of matter into infinitely dense abysses. But bit by bit, astronomers tallied up evidence for black holes’ existence. They puzzled over where these behemoths live and how they gulp down matter. They questioned what the existence of black holes means for other physics theories.

For more than a decade, a team of researchers has been engrossed in an ambitious effort to snap a picture of a black hole for the very first time. Now, they’ve done it. What better time to think back to black holes’ origins and the journey so far?

Power Words

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American Association for the Advancement of Science     (or AAAS)   Formed in 1848, it was the first permanent organization formed to promote the development of science and engineering at the national level and to represent the interests of all its disciplines. It is now the world’s largest such society. Despite its name, membership in it is open to anyone who believes “that science, technology, engineering, and mathematics can help solve many of the challenges the world faces today.” Its members live in 91 nations. Based in Washington, D.C., it publishes a host of peer-reviewed journals — most notably Science.

archive     (adj. archival) To collect and store materials, including sounds, videos, data and objects, so that they can be found and used when they are needed. The term is also for the process of collecting and storing such things. People who perform this task are known as archivists.

astronomy     The area of science that deals with celestial objects, space and the physical universe. People who work in this field are called astronomers.

behemoth     A term for anything that is amazingly big. The term comes from a monstrous animal described in the Bible’s book of Job.

black hole     A region of space having a gravitational field so intense that no matter or radiation (including light) can escape.

data     Facts and/or statistics collected together for analysis but not necessarily organized in a way that gives them meaning. For digital information (the type stored by computers), those data typically are numbers stored in a binary code, portrayed as strings of zeros and ones.

equation     In mathematics, the statement that two quantities are equal. In geometry, equations are often used to determine the shape of a curve or surface.

evaporate     To turn from liquid into vapor.

event horizon     An imaginary sphere that surrounds a black hole. The more massive the black hole, the bigger the sphere. Anything that happens inside the event horizon is invisible, because gravity is so strong that under normal circumstances even light can’t escape. But according to some theories of physics, in certain situations small amounts of radiation can escape.

field     An area of study, as in: Her field of research was biology. Also a term to describe a real-world environment in which some research is conducted, such as at sea, in a forest, on a mountaintop or on a city street. It is the opposite of an artificial setting, such as a research laboratory. (in physics) A region in space where certain physical effects operate, such as magnetism (created by a magnetic field), gravity (by a gravitational field), mass (by a Higgs field) or electricity (by an electrical field).

galaxy     A massive group of stars bound together by gravity. Galaxies, which each typically include between 10 million and 100 trillion stars, also include clouds of gas, dust and the remnants of exploded stars.

gravity     The force that attracts anything with mass, or bulk, toward any other thing with mass. The more mass that something has, the greater its gravity.

Hawking radiation     The particles emitted from the event horizon on the outer edges of a black hole. Energy can be converted into a pair of particles. If that happens very close to outer edge of a black hole, one of those particles can tunnel out and become detected — providing the only direct physical clue to the black hole’s presence. These emissions are called Hawking radiation for Stephen Hawking, the famous British physicist who came up with the idea that black holes can emit particles.

haze     Fine liquid or solid particles scattered through the atmosphere that make it hard to see. Haze can be caused by harmful substances such as air pollutants or by water vapor.

information     (as opposed to data) Facts provided or trends learned about something or someone, often as a result of studying data.

information paradox     (in physics) A problem created by two conflicting ideas about how black holes work and how the universe works. Black holes eventually disappear, and presumably, the information they contain about what’s in them also disappears. But this disappearance breaks a law of quantum mechanics, which says that information is never “lost” to the universe.

laser     A device that generates an intense beam of coherent light of a single color. Lasers are used in drilling and cutting, alignment and guidance, in data storage and in surgery.

light-year     The distance light travels in one year, about 9.48 trillion kilometers (almost 6 trillion miles). To get some idea of this length, imagine a rope long enough to wrap around the Earth. It would be a little over 40,000 kilometers (24,900 miles) long. Lay it out straight. Now lay another 236 million more that are the same length, end-to-end, right after the first. The total distance they now span would equal one light-year.

LIGO     (short for Laser Interferometer Gravitational wave Observatory) A system of two detectors, separated at a great geographical distance, that are used to register the presence of passing gravitational waves.

mass     A number that shows how much an object resists speeding up and slowing down — basically a measure of how much matter that object is made from.

matter     Something that occupies space and has mass. Anything on Earth with matter will have a property described as "weight."

media     (in the social sciences) A term for the ways information is delivered and shared within a society. It encompasses not only the traditional media — newspapers, magazines, radio and television — but also Internet- and smartphone-based outlets, such as blogs, Twitter, Facebook and more. The newer, digital media are sometimes referred to as social media. The singular form of this term is medium.

Milky Way     The galaxy in which Earth’s solar system resides.

NASA     Short for the National Aeronautics and Space Administration. Created in 1958, this U.S. agency has become a leader in space research and in stimulating public interest in space exploration. It was through NASA that the United States sent people into orbit and ultimately to the moon. It also has sent research craft to study planets and other celestial objects in our solar system.

observatory     (in astronomy) The building or structure (such as a satellite) that houses one or more telescopes.

online     (n.) On the internet. (adj.) A term for what can be found or accessed on the internet.

paradox     An idea or a statement that is true, but that seems logically impossible.

particle     A minute amount of something.

perception     The state of being aware of something — or the process of becoming aware of something — through use of the senses.

physical     (adj.) A term for things that exist in the real world, as opposed to in memories or the imagination. It can also refer to properties of materials that are due to their size and non-chemical interactions (such as when one block slams with force into another).

physics     The scientific study of the nature and properties of matter and energy. Classical physics is an explanation of the nature and properties of matter and energy that relies on descriptions such as Newton’s laws of motion. Quantum physics, a field of study that emerged later, is a more accurate way of explaining the motions and behavior of matter. A scientist who works in such areas is known as a physicist.

quasar     Short for quasi-stellar light source. This is the brilliant core of some galaxy (massive collections of stars) that contains a super-massive black hole. As mass from the galaxy is pulled into that black hole, a huge quantity of energy is released, giving the quasar its light.

radiation     (in physics) One of the three major ways that energy is transferred. (The other two are conduction and convection.) In radiation, electromagnetic waves carry energy from one place to another. Unlike conduction and convection, which need material to help transfer the energy, radiation can transfer energy across empty space.

radio waves     Waves in a part of the electromagnetic spectrum. They are a type that people now use for long-distance communication. Longer than the waves of visible light, radio waves are used to transmit radio and television signals. They also are used in radar.

relativity     (in physics) A theory developed by physicist Albert Einstein showing that neither space nor time are constant, but instead affected by one’s velocity and the mass of things in your vicinity.

simulation     (v. simulate) An analysis, often made using a computer, of some conditions, functions or appearance of a physical system. A computer program would do this by using mathematical operations that can describe the system and how it might change over time or in response to different anticipated situations.

spacetime     A term made essential by Einstein’s theory of relativity, it describes a designation for some spot given in terms of its three-dimensional coordinates in space, along with a fourth coordinate corresponding to time.

spherical     Adjective for something that is round (as a sphere).

star     The basic building block from which galaxies are made. Stars develop when gravity compacts clouds of gas. When they become dense enough to sustain nuclear-fusion reactions, stars will emit light and sometimes other forms of electromagnetic radiation. The sun is our closest star.

stellar     An adjective that means of or relating to stars.

sun     The star at the center of Earth’s solar system. It’s an average size star about 26,000 light-years from the center of the Milky Way galaxy. Also a term for any sunlike star.

telescope     Usually a light-collecting instrument that makes distant objects appear nearer through the use of lenses or a combination of curved mirrors and lenses. Some, however, collect radio emissions (energy from a different portion of the electromagnetic spectrum) through a network of antennas.

theoretical     An adjective for an analysis or assessment of something that based on pre-existing knowledge of how things behave. It is not based on experimental trials. Theoretical research tends to use math — usually performed by computers — to predict how or what will occur for some specified series of conditions. Experimental testing or observations of natural systems will then be needed to confirm what had been predicted.

theory     (in science) A description of some aspect of the natural world based on extensive observations, tests and reason. A theory can also be a way of organizing a broad body of knowledge that applies in a broad range of circumstances to explain what will happen. Unlike the common definition of theory, a theory in science is not just a hunch. Ideas or conclusions that are based on a theory — and not yet on firm data or observations — are referred to as theoretical. Scientists who use mathematics and/or existing data to project what might happen in new situations are known as theorists.

universe     The entire cosmos: All things that exist throughout space and time. It has been expanding since its formation during an event known as the Big Bang, some 13.8 billion years ago (give or take a few hundred million years).

wave     A disturbance or variation that travels through space and matter in a regular, oscillating fashion.

World War I     Also known as WWI and the Great War. This war began in 1914, as two alliances faced off against one another. On one side were the so-called Central Powers — Germany, Bulgaria and the Ottoman and Austro-Hungarian empires. On the other side were the Allies — France, Great Britain, Russia, Italy and, beginning in 1917, the United States.

X-ray     A type of radiation analogous to gamma rays, but having somewhat lower energy.