What do scientists mean when they say space is curved?
The technical term is Minkowski space – Euclidian space and time. Curved space is either de Sitter space (with positive curvature, also called closed, in the same way as a ball has a endless but finite surface), and anti-de Sitter space (with negative curvature, also known as open space, often imagined like an infinite Pringle).
What does 'curved space' mean?
Curved space often refers to a spatial geometry which is not "flat", where a flat space is described by Euclidean geometry.Curved spaces can generally be described by Riemannian geometry though some simple cases can be described in other ways. Curved spaces play an essential role in general relativity, where gravity is often visualized as curved space.
Is space is really curve?
Any space that is not completely flat is called curved space. The surface of a sphere is curved space, as is the surface of a saddle. A sphere is an example of positive curvature, meaning if a triangle is made with straight lines in curved space, the angles will add up to more than the normal 180 degrees.
Is space curve due to gravity?
The curvature of spacetime (not just space) is responsible for gravity. Literally, near heavy objects, the “future direction” points slightly down. So anything that moves forward in time will find its trajectory pointing down slightly.
Is space actually curved?
Space is indeed curved -- in four dimensions. Many people think the fourth dimension is simply time, and for some astronomical equations, it is. Einstein used time as a fourth dimension to describe a coordinate system called space-time.
Did Einstein say space is curved?
Einstein said that space is curved and that matter is the source of the curvature. (Matter is also the source of gravitation, so gravity is related to the curvature—but that will come later in the chapter.)
Is the universe flat or spherical?
flatThe exact shape is still a matter of debate in physical cosmology, but experimental data from various independent sources (WMAP, BOOMERanG, and Planck for example) confirm that the universe is flat with only a 0.4% margin of error.
Is space curved around Earth?
Because space is curved, even light rays must be deflected by gravity. A heavy object like a galaxy can distort light rays so much that it alters the images of objects beyond it, like a lens. This phenomenon is known as gravitational lensing.
Does gravity bend light?
Gravity bends light Light travels through spacetime, which can be warped and curved—so light should dip and curve in the presence of massive objects. This effect is known as gravitational lensing GLOSSARY gravitational lensingThe bending of light caused by gravity .
What is the 4th Dimension in space?
timeThere is a fourth dimension: time; we move through that just as inevitably as we move through space, and via the rules of Einstein's relativity, our motion through space and time are inextricable from one another. But could additional motions be possible?
Is space infinite or finite?
The observable universe is finite in that it hasn't existed forever. It extends 46 billion light years in every direction from us. (While our universe is 13.8 billion years old, the observable universe reaches further since the universe is expanding).
Does space have a bottom?
The universe has a bottom. That bottom extends infinitely outward and has an infinite sky above it, with an infinite number of stars and galaxies. The bottom is remarkably terrestrial, with gravity, mountains, lakes, forests, and sunshine, each of which deserves additional discussion.
Does space have an edge?
As far as we can tell, there is no edge to the universe. Space spreads out infinitely in all directions. Furthermore, galaxies fill all of the space through-out the entire infinite universe.
Is time linear or curved?
Time itself is neither linear nor circular. It does not flow or move but allows others to do so.
What is space made of?
Outer space is not completely empty—it is a near perfect vacuum containing a low density of particles, predominantly a plasma of hydrogen and helium, as well as electromagnetic radiation, magnetic fields, neutrinos, dust, and cosmic rays.
Do black holes curve space?
Black holes are a curvature in spacetime. They are an object where gravity is so powerful that spacetime – a fabric of the three dimensions of space plus the fourth dimension of time shown to be linked by Einstein's theory of relativity – is bent so far that it becomes a hole.
Who said space is curved?
Albert Einstein'sEinstein's theory of general relativity: 100 years of bent spacetime. One of Albert Einstein's most important insights is that empty space can be curved and what we call gravity is really just a consequence of those curves. The most common is probably the grid dipping under a planet, star or galaxy.
Why does curved space time cause gravity?
It is fine to say that for an object flying past a massive object, the spacetime is curved by the massive object, and so the object flying past follows the curved path of the geodesic, so it "appears" to be experiencing gravitational acceleration.
What do physicists mean by flat universe?
In a flat universe, Euclidean geometry applies at the very largest scales. This means parallel lines will never meet, and the internal angles of a triangle always add up to exactly 180 degrees—just like you're used to. But in curved universes, whether finite or infinite, things get weird.
What is time space curvature?
3:386:20General Relativity: The Curvature of Spacetime - YouTubeYouTubeStart of suggested clipEnd of suggested clipLike a bowling ball pressing down on a membrane. This curvature creates what we know of as gravity.MoreLike a bowling ball pressing down on a membrane. This curvature creates what we know of as gravity. Being that massive objects tend to fall towards more massive objects. And this explains the orbits
Is space empty?
You find yourself floating in space You activate your spacesuit’s jet pack and head out 100km forwards from the drop-off point.
How is spacetime curved?
Spacetime is curved by the mass of objects like the Sun and Earth. Credit: vchal / iStock / Getty Images Plus
What if you don't turn back after the first 100km?
But what if you don’t turn back after the first 100km? Instead you make a 90 º left turn, travel another 100km, turn left 90 º again, then travel another 100km – so you’re moving parallel to your first path as in the illustration below.
How do Flatlanders know if their universe is curved?
Flatlanders, who cannot rise above their curved universe to view its spherical shape, can still work out that their universe is curved by drawing a grid all over it and seeing how the shapes fit together.
What happens after 100km?
After 100km, you decide to turn around and return to the drop-off point. You know that, if you travel 100km back the way you came, you’ll be back at the drop-off point. But how do you know that’s the case?
Which scientist proposed that space gets curved by massive objects and that this causes gravity?
In his general theory of relativity, Albert Einstein proposed that space gets curved by massive objects and that this causes gravity.
What happens when an object moves in a curve?
So when an object moves in a curve, like the Moon’s elliptical orbit around Earth, it shows that a force is at play – in that case, Earth’s gravity pulling on the Moon.
What is the difference between flat and curved coordinates?
In flat coordinates, the orbiting body is attracted to where the opposing body is at that moment with the force carried instantaneously, whereas in curved coordinates, the orbiting body is attracted to where the opposing body was a moment earlier with the force carried at the speed of light. Either way, you get the same result.
What is relativity theory?
Relativity Theory speculates that objects cause effects upon space and space causes effects upon objects. That theory has no equations that support this claim. That theory has no direct empirical evidence that supports that claim.
What happens if there is any curvature in space?
If there is any curvature in space then that is less than we can measure or observe.
What does it mean when space is flat?
When physicists speak of space on the greater scale, they often describe it as “flat,” meaning that we see no evidence of a distortion in its broad geometry. While massive bodies — stars, galaxies — exert enough gravitational attraction to distort spacetime locally and affect passing light, space generally exhibits no great bending, as one might imagine it doing as a response to the combined masses of the universe.
How many degrees does spin1/2 go through?
Kirsten Hacker's answer to When we say that spin-1/2 fermions must go through 720 degrees to equal the 360 degrees required by spin-1 bosons, what exactly is being measured?
How can quantum constants be tied to gravitational constants?
By translating between these coordinate systems , one can tie quantum constants to the gravitational constant.
Why would a spiral be best applied?
If one had to speculate, a spiral would best apply, because the galaxies appear that way.
Why do Planck and the other probes have tension?
So when they go to mix in the other probes, they find a tension, because the other eyewitnesses tell us that we live in a flat universe — hence the controversy over a possible "crisis" in cosmology.
Why do astronomers care about the ultimate curvature of the universe?
Astronomers are very curious about the ultimate curvature of the universe: how do parallel lines and triangles behave on the very largest scales? They care because the shape of the universe is intimately connected to its fate. Einstein's theory of general relativity, which we use to understand the cosmos, tells us that the contents of space-time affect its shape, and the shape tells the contents how to move.
What is the cosmic microwave background?
Enter the cosmic microwave background (CMB), a bath of light soaking the universe, left over from when our cosmos was just a baby, only 380,000 years old. That light has spent the past 13.8 billion years racing to us, so we can study features in the CMB to test our universe for flatness.
What is the Planck satellite?
The Planck satellite, a joint effort between NASA and the ESA, was the latest effort to map the CMB across the whole sky. Planck did a really good job, measuring the CMB to the greatest level of precision yet, with its most recent data released in 2018.
What is the shape of the universe?
The shape of the universe is one of the most important questions in cosmology, with far-reaching implications, up to and including the ultimate fate of the cosmos. For decades, we've been measuring our universe to be geometrically flat, but a team of cosmologists are now reporting that our latest measurements actually prefer something rounder.
How to test the geometry of space time?
To test the geometry of space-time, we need to look at all sorts of distant sources and determine if the light from those sources has undergone any major deviations in its path to us. Light beams should stay on the straight and narrow over billions of years, so we can use distant probes to "smooth over" tiny little bumps and wiggles like those caused by galaxies and black holes, and look at the true, underlying geometry of the universe.
Why do we know that the Earth is curved?
Know the curves. The surface of the Earth is curved. We know this because the tiles of geometry that you learned in high school don't always apply. For example, parallel lines don't always stay parallel on the Earth: lines of longitude intersect at the north and south poles, something that can never happen on a flat plain.
What happens if a 4D being crumples?
If a 4D being decides to "crumple" our 3D space, like the Flatlanders, you wouldn't notice anything right away, either. You might notice some unusual phenomena, like walking to your mailbox and ending up in Mongolia. Scientists believe, however, that our space is smoothly curved -- more like a ball than a wad of paper -- and thus the effects are only noticeable on cosmological scales. As 3D beings, we experience just the "surface" of the 4D ball, just as Flatlanders experience only two dimensions of their space that you can curve into three dimensions.
How to curve flatland?
You can curve Flatland in your three-dimensional reality by rolling the piece of paper into a tube, folding it into a paper airplane, or just crumpling it into a wad. Doing so would not be immediately apparent to Flatlanders, because light still travels in straight lines within their 2D space.
Why did Einstein use time as a fourth dimension?
Einstein used time as a fourth dimension to describe a coordinate system called space-time. This is the stage on which planets, stars, galaxies -- all matter in the universe -- act their gravitational roles. In Einstein's Theories of Relativity, time helps us understand the three-dimensional experience of gravity.
What does curvature mean in math?
Regardless of the number of dimensions that describe a space, the curvature of that space, by definition, implies the existence of at least one more. In other words, an additional dimension must exist into which the other dimensions can be curved.
Is time a spatial dimension?
But time is not a true spatial dimension like the three we're familiar with . Unlike width, length, and height, we only know time to move in one direction: past to present to future. In this way, time merely serves as a yardstick for our personal experiences and our laws of physics.
How to make a donut out of 2D paper?
With your 2D piece of paper, you can connect the ends a few different ways. Connect one of the dimensions normally and you have a cylinder. Flip one edge over before connecting and you've made a Mobius strip. Connect two dimensions, the top to the bottom and one side to the other, and you have a torus (aka a donut).
What does the shape of the universe depend on?
The shape of the universe depends on its density . If the density is more than the critical density, the universe is closed and curves like a sphere; if less, it will curve like a saddle. But if the actual density of the universe is equal to the critical density, as scientists think it is, then it will extend forever like a flat piece of paper. (Image credit: NASA/WMAP Science team.)
Why are cylinders flat?
There's an important distinction between geometry, the behavior of parallel lines, and topology, the way a space can get all twisted up. While the geometry of the universe is very well measured (again, it's flat), the topology is not.
What is the opposite of the Earth's curved shape?
The opposite of the Earth's curved shape is a saddle: on that surface, lines that start out parallel end up spreading apart from each other (in swanky mathematical circles this is known as "ultraparallel"). [ I explore the possible shapes of the universe in this video.]
How to measure flatness of a structure?
So there you have it: You can measure the "flatness" of a structure just by watching how parallel lines behave. In our 3D universe, we could watch beams of light: If, say, two lasers started out perfectly parallel, then their long-term behavior would tell us important things.
How long do parallel lines stay parallel?
One answer lies in parallel lines. If you start drawing two parallel lines on your paper and let them continue on, they'll stay perfectly parallel forever (or at least until you run out of paper). That was essentially the definition of a parallel line for a couple thousand years, so we should be good.
How many hours of exposure time did the Hubble Space Telescope take to capture this image?
The Hubble Space Telescope accumulated approximately 555 hours of exposure time to capture this Hubble eXtreme Deep Field image. The area shown represents a seemingly empty patch of sky about the width of a toothpick when held at arm's length. The picture contains only two foreground stars (indicated by surrounding spikes). Every other object is a galaxy. The most distant galaxies' light is reddened by the expansion of the universe. We're seeing light that left them 13.2 billion years ago. (Image credit: <a href="http://hubblesite.org/newscenter/archive/releases/2012/37/image/a//">NASA</a>)
How to find the curvature of the universe?
One can experimentally calculate this Ω to determine the curvature two ways. One is to count up all the mass-energy in the universe and take its average density then divide that average by the critical energy density. Data from Wilkinson Microwave Anisotropy Probe (WMAP) as well as the Planck spacecraft give values for the three constituents of all the mass-energy in the universe – normal mass ( baryonic matter and dark matter ), relativistic particles ( photons and neutrinos ), and dark energy or the cosmological constant:
What is curvature in space?
The curvature is a quantity describing how the geometry of a space differs locally from the one of the flat space. The curvature of any locally isotropic space (and hence of a locally isotropic universe) falls into one of the three following cases:
How does mass and energy determine the curvature of spacetime?
General relativity explains that mass and energy bend the curvature of spacetime and is used to determine what curvature the universe has by using a value called the density parameter, represented with Omega ( Ω ). The density parameter is the average density of the universe divided by the critical energy density, that is, the mass energy needed for a universe to be flat. Put another way,
What are distance measures?
See also: Distance measures (cosmology) As stated in the introduction, there are two aspects to consider: its local geometry, which predominantly concerns the curvature of the universe, particularly the observable universe, and. its global geometry, which concerns the topology of the universe as a whole.
What is the shape of the universe?
The shape of the universe, in physical cosmology, is the local and global geometry of the universe. The local features of the geometry of the universe are primarily described by its curvature, whereas the topology of the universe describes general global properties of its shape as of a continuous object. The spatial curvature is related ...
What is the comoving coordinates?
Cosmologists normally work with a given space-like slice of spacetime called the comoving coordinates, the existence of a preferred set of which is possible and widely accepted in present-day physical cosmology. The section of spacetime that can be observed is the backward light cone (all points within the cosmic light horizon, given time to reach a given observer), while the related term Hubble volume can be used to describe either the past light cone or comoving space up to the surface of last scattering. To speak of "the shape of the universe (at a point in time)" is ontologically naive from the point of view of special relativity alone: due to the relativity of simultaneity we cannot speak of different points in space as being "at the same point in time" nor, therefore, of "the shape of the universe at a point in time". However, the comoving coordinates (if well-defined) provide a strict sense to those by using the time since the Big Bang (measured in the reference of CMB) as a distinguished universal time.
How is the local geometry of the universe determined?
The local geometry of the universe is determined by whether the density parameter Ω is greater than, less than, or equal to 1.
