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Space Physics

Even if you haven’t thought about it much, space has played an important part in your life and will continue to play an important role far into the future. The vast expanses of the cosmos are the last great frontier for humanity, so we need to talk about what is out there, and how everything out there interacts with everything else. This article is here to give you an overview of each topic that you need to know about within space physics, as well as a very quick rundown of what you’ll learn in each. Make sure to go deep into the articles

What is Space Physics?

Space physics is the branch of physics that tries to answer some of the oldest questions humans have ever had, such as what is our place in the universe? or where did we come from? These questions have been asked for thousands of years and are likely to continue being asked and answered for thousands more.

Space Physics Topics

Within GCSE physics, space physics has a more clearly defined goal. You will have to learn about 4 topics within space physics: Our Solar System, The Life Cycle of a Star, Orbital motions and Redshift. Each of these topics has an associated explanation that goes into a lot more depth than we are going to cover in this one, so make sure you read them!

Space Physics vs Astrophysics

At GCSE level, space physics and astrophysics can be used completely interchangeably. You do not need to worry about any differences between the two. For now, you only need to know and use the term space physics and be aware that astrophysics is a field of research that means essentially the same thing. But just because you don't have to worry, doesn't mean that you can't go beyond the scope of your school curriculum and learn about how space physics and astrophysics are different now!

Outside of GCSE physics, astrophysics is the study of objects outside the solar system, such as supernovae, nebulae and black holes. Space physics, on the other hand, is the term given to a specific field of research that studies plasmas within our solar system, which includes subjects like planetary physics and solar physics.

Outside of GCSE physics, space physics more closely focuses on the magnetic fields of planets, how these magnetic fields interact with the solar wind, and how these changes can affect satellites in orbit. You don’t need to know about these yet though, so it’s best not to worry about them until they come up.

An Overview of Each Topic

Let’s now take this opportunity to look at each topic within space physics and figure out what each one involves. As you learn each of these topics, you will also be able to start drawing links between them which should also strengthen your overall understanding of space physics.

Our Solar System

  • The topic “Our Solar System” explores the objects in the Solar System, and how they were formed. There are 9 major objects in the solar system, including the Sun. In order of distance from the sun, these are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Each of these planets orbits the sun at a different speed and a different orbital radius.
  • Some of the planets in our solar system also have objects orbiting them, called moons. Moons are usually substantially smaller than the planets they orbit and are examples of natural satellites. On top of these natural satellites, there are also hundreds of man-made satellites travelling through the solar system each performing different tasks, being used as communications relays or for scientific studies.
  • You will also learn about the fusion reaction that keeps a star in a delicate equilibrium between collapsing in on itself and expanding outwards into nothing. This leads quite nicely to learning about the life cycle of a star as well.

The Life Cycle of a Star

Stars are some of the largest individual objects in the universe, and compared to a human lifespan they seem to live forever! Stars do still go through a life cycle, however, just like humans do.

  • All stars go through a life cycle from the birth of the star to their inevitable death. The size of a given star determines a few things about its life cycle. The size of a star determines how long a star will live, as well as the stages it goes through leading up to its death.
  • At GCSE level, you need to be able to describe the life cycle of two different sizes of stars: stars that are about the same size as the sun and stars that are much larger than the sun. The diagram below outlines the life cycles of these two varying sizes of stars. Notice how no matter the size of the star, they all go through the same first three stages!A diagram which shows the life cycle of stars the same size as the sun and stars that are much more massive than the sun.
    A diagram showing the life cycles of different sizes of stars, Kourosh Simpkins - StudySmarter Originals
  • You will also need to learn about how a star generates heat and light. In short, they utilise a process called nuclear fusion. Nuclear fusion is where two atomic nuclei are fused into one nucleus. In main-sequence stars, the fuels used for nuclear fusion are hydrogen and helium atoms. However, as stars reach the end of their life cycles they fuse heavier elements, all the way up to Iron. Any elements heavier than iron were formed in supernovae which spread all of the elements created throughout the universe.
  • Several of the elements in the periodic table are formed in the hearts of dying stars. This process is called supernova nucleosynthesis. Another type of nucleosynthesis is stellar nucleosynthesis, which covers all nuclei that are formed in a star at any stage of its life. In fact, most elements are formed because of a reaction or interaction involving stars. Check out the version of the periodic table below for the elements and where they can be formed.

    A version of the periodic table, indicating the main origin of elements found on Earth, By Cmglee - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=31761437

Orbital Motion, Natural and Artificial Satellites

Companies and countries spend a lot of time, manpower, and money sending satellites into space to perform a variety of tasks. Some satellites are used for global navigation, like the GPS or GLONASS constellations. Other satellites may be used for satellite internet connections, like SpaceX's Starlink constellation. Importantly, every single one of these satellites has had its orbital speed calculated at one point or another in its life. We want to know the orbital speed of a satellite so that we can ensure that it remains in orbit.

If the orbital speed of any satellite ever dropped below the minimum speed to orbit the Earth, engineers would immediately want to know why that happened, as well as find a way to fix it. Because it is very likely that you either directly or indirectly use at least one of these satellites a day, calculating orbital speed is a daily part of life that you may never have considered, and essential to the modern world.

  • The force that causes objects to maintain circular orbits is gravity. Every object in the universe has a gravitational pull, however, you probably don't feel the gravitational pull of people or other relatively small objects, because it only really has a noticeable pull when the object has a very large mass, such as a planet.

  • Not only does every object in space exert a gravitational pull, but they also have an orbital motion that defines how the object moves through space. For a circular orbit, the speed of the orbit is constant, but the velocity is constantly changing. Remember, velocity is the speed of an object in a given direction. In the diagram below, the speed of the planet doesn't change but notice that the velocity changes between location 1 and location 2 due to the change in the direction of the object's motion as it moves from location 1 to location 2.

    A diagram displaying the velocity and force vectors of an object orbiting in circular motion around a more massive body. StudySmarter Originals

Red-Shift

There are a few theories that explore how our universe came into existence. These theories are based on observations that astronomers have made and on looking at concepts such as red-shift and dark energy. As part of the red-shift topic, we'll also explore and explain the big bang theory.

  • Red-shift is the phenomenon of light we observe from distant galaxies being 'redder' when it reaches Earth than when it was originally emitted by a galaxy. The light's wavelength is shifted towards the red end of the visible spectrum. One source of red-shift is the expansion of the universe. The expansion of space causes galaxies that are further away from us to recede from us faster. The light waves emitted by further and relatively faster-moving galaxies are red-shifted more than closer slower galaxies. The more red-shifted the light from a galaxy is, the faster the galaxy is moving away from us.
  • The fact that we can observe red-shift is evidence supporting the big bang theory. The big bang theory suggests that the universe began as a very small region that was extremely hot and densely packed. This theory is further backed up by the fact that the universe seems to be expanding, and we have observed this expansion thanks to red-shift.
  • There is still more about the universe that we do not know. Two such examples are dark energy and dark matter.
  • Scientists are not completely sure why the rate of expansion of our universe is increasing, however, some have theorised that it is due to a phenomenon we have not yet fully discovered called dark energy.

  • Dark matter was theorised due to observations of galaxies rotating too quickly for the mass that they contain. We only know of its existence because it has a gravitational effect on nearby objects, but we have never directly observed it.

Space Physics - Key takeaways

  • Space physics is the study of objects in our universe and how they interact with each other.
  • Inside the space physics topic, there are four main sub-topics that you need to be aware of. These are our solar system, the life cycle of a star, orbital motion, and red-shift.
  • Our solar system explores objects that are in our solar system, how they interact and how they were all formed.
  • The life cycle of a star looks at what happens as a star is born, lives, and what happens when stars die.
  • Orbital motion explains how objects interact with each other due to gravity, and how we describe and explain orbits.
  • Red-shift looks at the life of the universe, the evidence for the big bang theory and some unknown things that we cannot currently explain.

Frequently Asked Questions about Space Physics

Space in physics, or outer space, is everything beyond the Earth and its atmosphere. It contains everything we know of, from the smallest particles up to the largest stars and black holes.

The topics of space physics are our solar system, the life cycle of a star, orbital motion and red-shift.

Space physics is about exploring how objects interact with each other in our universe, some of the rules they have to follow and understanding some of the best examples of how we as humans have gotten to where we are today.

Final Space Physics Quiz

Question

What is the relationship between Doppler effect and red-shift?

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Answer

You may have observed that an ambulance or police car's siren sounds high-pitched as it approaches you and then drops to a low-pitched tone as it leaves. This phenomenon is called the Doppler effect and it is caused by a change in frequency or wavelength. It occurs whenever a wave source moves closer to or away from an observer. When an object moves closer to an observer, the waves change to a higher frequency with a shorter wavelength. there is a shift in the frequency of the waves to higher, and in the wavelength to shorter. The same applies to light in addition to sound. 

When the light waves move away from an observer, the wavelengths increase. Since the spectrum of light shifts toward the red color in the spectrum, it is called red-shift.

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What is the difference between red-shift and blue-shift?

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When the light waves move away from an observer, the wavelengths increase. Since the spectrum of light shifts toward the red color in the spectrum, it is called red-shift. However, when the light waves move towards the observer, then the wavelengths get shorter and the spectrum shifts to the blue color. In this case, it is called blue-shift

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How fast a star or galaxy is is not related to the red-shift. (True/False)

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Answer

False. 

The faster a star or galaxy is moving relative to the observer, the bigger the shift is.  

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What does the red-shift phenomenon indicate?

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The red-shift phenomenon indicates that the other galaxies are moving away from the Milky Way galaxy and the universe is expanding.  

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What is the definition of the Big Bang?

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The Big Bang is the name given to the event that, in the light of modern cosmological theories, made it possible for our Universe to form as a result of the expansion of matter from an extremely dense and hot point. In other words, just like the singularity at the center of black holes, there is also a singularity at the beginning of the Universe. The universe started from this singular point and evolved towards its present state.  

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What was the name of the theory of Fred Hoyle?

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Steady State Theory

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The Big Bang is an explosion. (True/False)

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False. It is more of an expansion.

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What is Cosmic Microwave Background Radiation?

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Cosmic microwave background radiation is a form of electromagnetic wave that fills the entire universe. 

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Why is Cosmic Microwave Background Radiation called ''cosmic''?


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It is not radiation that is located in a certain place in the Universe; rather, it fills every part of the Universe that we can observe (and most likely, cannot observe). 

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Why is Cosmic Microwave Background Radiation called ''microwave''?


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Although it originally radiated at many frequencies, the frequency at which it was most pronounced was at the level of 160.2 Gigahertz, which corresponds to the interval known as a "microwave" in the light spectrum. 

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Why is Cosmic Microwave Background Radiation called ''microwave''?


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If you took into account all other sources of heat and radiation in the Universe and measured the temperature of a space cavity that was "black", you would measure an average temperature of 2.7 Kelvin. in other words, this radiation is caused by the space-time fabric that makes up the Universe itself, it is like a "background noise". 

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Why is Cosmic Microwave Background Radiation called ''radiation''? 

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Answer

Because we are talking about electromagnetic radiation. 

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What does Steady State Theory suggest?

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According to this theory, the density of matter in the Universe has always been constant over time, because the creation event has been going on continuously.  

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What does the Primeval Atom Hypothesis suggest?


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Answer

 The Universe may not be in a continuous state of creation but instead came from a singular beginning.

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According to the Big Bang theory, the Universe is isotropic. (True/False)

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Answer

True. 

No matter which direction you look at the Universe in, you will see similar qualities. So the Universe is isotropic.


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How many planets are there in the Solar System?

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Answer

There are eight planets in the Solar System

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What is the Solar System?

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The solar system is the name given to our local collection of planets, the sun that they orbit and any other local objects.

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Which planet in the solar system is the hottest

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Venus

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What is the order of the planets?

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Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune

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What is a common similarity of all of the Inner planets?

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All of the inner planets are rocky and solid, they are often also called the rocky planets.

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Name all of the inner planets

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Mercury, Venus, Earth and Mars

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What is a similarity of all of the Outer planets?

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They are all made of gas and are commonly called gas giants.

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What are the names of the four outer planets?

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Jupiter, Saturn, Uranus and Neptune.

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Why is Pluto not a planet?

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It is considered a dwarf planet, as it is too large to be seen as an asteroid but too small to be thought of as a planet.

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How many known dwarf planets are there?

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There are currently 5 known dwarf planets. Their names are: Ceres, Pluto, Haumea, Makemake and Eris.

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What are comets made from?

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Comets are made of dust, rock and ice.

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What are asteroids made from?

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Asteroids are made of rock.

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Where are the majority of asteroids in the solar system located?

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Asteroids are mainly located in the asteroid belt, between Mars and Jupiter.

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How high can temperatures on Venus reach?

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Temperatures on Venus can reach up to 460o Celsius, which makes it the hottest planet in the Solar System.

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Where does all of the energy in the solar system come from?

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Answer

The Sun provides all of the energy in the solar system.

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What is orbital motion?

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Orbital motion is the motion of an object or body around a more massive object due to the force of gravity exerted by the more massive object.

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What objects exhibit orbital motion?

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All objects in space must exhibit some form of orbital motion.

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Question

Which of these objects doesn't orbit the sun?

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Answer

All of them orbit the sun

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Question

Does velocity change along a circular orbit?

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Answer

The motion of an orbit is a circle, therefore an object's velocity cannot remain constant. So yes, its velocity does change along an object's orbit.

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Question

What is the shape of the orbit of most planets?

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Technically planetary orbits are slightly non-circular, however, they are almost circular.

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What is the orbital shape of a comet?

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The orbit of a comet is extremely stretched.

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Why is a stable orbital motion important for artificial satellites?

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If an object's orbit is unstable, then it will either drift off into space or crash back into the object that it is orbiting.

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What is the lowest orbital speed that an object orbiting the Earth can have?

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The slowest orbital speed for an orbit around the Earth is 7,600 metres per second.

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How fast can an object orbit Earth before it will leave the Earth's orbit?

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The fastest orbital speed around the Earth for any object is 11,200 m/s.

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How do galaxies exhibit orbital motion?

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Answer

Stars in galaxies orbit around the galactic centre.

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Question

What is the orbital speed of Mercury?

Orbital radius = 58 million kilometres, Orbital period = 88 days.

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Answer

4.1 million km/day

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What is the orbital speed of the Earth?

Orbital radius = 150 million kilometres, Orbital period = 365 days.

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2.6 million km/day

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What object does the Earth accelerate towards?

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The Earth accelerates towards the Sun.

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What is meant by the expansion of the universe?

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Answer

The expansion of the universe is the increase in the distance between distant parts of the universe over time.  

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Why is Hubble's work important in the Expanding Universe Theory?

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Answer

Edwin Hubble, as a result of his observations in 1929, showed that distant celestial bodies in all directions, without exception, were moving away from the Earth and that as the distance to the Earth increased, the rate of recession also increased.  

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Why did the expansion rate of the universe decrease until 5 billion years ago?


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Answer

The decrease in the expansion rate of the universe can be attributed to the effect of gravity. As the universe expands, the effect of gravity decreases as the distance between the materials increases.

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Question

What explains the increase in the expansion rate of the Universe?

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Answer

The existence of dark energy has been suggested to explain the increase in the expansion rate of the universe. Unlike gravity, the effect of dark energy does not diminish as the universe expands. 

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Question

What is responsible for the acceleration of the expansion of the universe?

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Answer

Dark energy

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Can dark energy be observed? 

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Answer

No

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Question

To study dark energy and matter, what do physicists and cosmologists use?


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Answer

Physicists and cosmologists use space telescopes and electron accelerators. 

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